WO2006124768A1

WO2006124768A1 - Method and apparatus for blood pressure measurement and analysis

Info

Publication number: WO2006124768A1
Application number: PCT/US2006/018715
Authority: WO
Inventors: V. Patteson Lombardi; Donald Pate
Original assignee: State Of Oregon Acting By And Through The State Board Of Higher Education On Behalf Of The University Of Oregon
Priority date: 2005-05-12
Filing date: 2006-05-12
Publication date: 2006-11-23

Abstract

Disclosed herein are methods and devices that permit a more accurate determination of the blood pressure of a subject. In particular examples, such methods and devices correct a blood pressure measurement after it is obtained from an ambulatory blood pressure device, for example by applying a correction factor that takes into account bias and variability caused by changes in the posture or activity level of the subject. In particular examples, such methods and devices calibrate one or more blood pressure monitor sensors prior to measuring blood pressure by a blood pressure monitor by adjusting for bias and variability caused by changes in the posture or activity level of the subject.

Description

METHOD AND APPARATUS FOR BLOOD PRESSURE MEASUREMENT

AND ANALYSIS

CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No.

60/680,829 filed May 12, 2005 and U.S. Provisional Application No. 60/680,986 filed May 13, 2005, both herein incorporated by reference in their entirety.

FIELD This application relates to methods and devices for measuring blood pressure.

BACKGROUND

There are currently numerous methods and devices that can be used to determine the blood pressure of a subject. However, in a clinical setting, some subjects are indicated to be hypertensive, though they may not be when monitored in other ways, such as when evaluated based on 24-hour ambulatory blood pressure monitor (ABPM) values. For example, "white-coat hypertensives" are individuals whose blood pressure is elevated in the presence of a healthcare worker wearing a white coat. Such individuals often have an elevated blood pressure in a doctor's office or hospital, but can have an otherwise normal blood pressure elsewhere, such as based on ABPM measurements.

Although ambulatory blood pressure monitoring provides more information concerning an individual's blood pressure, such devices can produce inaccurate readings, such as underestimating diastolic blood pressure measurements, hi addition, such devices can produce inconsistent blood pressure readings from an individual. Therefore, a need exists for ambulatory blood pressure measuring devices and methods that provide more accurate and consistent blood pressure measurements. SUMMARY

Novel and non-obvious methods and devices are disclosed for more accurately measuring ambulatory blood pressure (ABP). The inventors have determined that corrections or adjustments made to take into account the subject's position (such as posture or body position), provide for more accurate measurements, for example for an ambulatory subject having a blood pressure that is being monitored over a period of time, such as over a 24-hour period, hi particular examples, a correction is made after the blood pressure measurement is obtained, and in other examples a correction is made before the blood pressure measurement is made (for example by adjusting the sensor sensitivity prior to measurement).

Exemplary approaches set forth herein also enhance the reliability of blood pressure measurements. That is, the reproducibility of blood pressure measurements is enhanced in that variations in results from repeated blood pressure measurements under identical conditions are minimized. It should be noted that there is no requirement that a method or device solve any one or more specific problems in the prior art. Based on these observations, methods and devices for determining blood pressure in a subject, such as a human or veterinary subject, are provided.

BRIEF SUMMARY OF THE DRAWINGS FIG. IA and B are schematic drawings showing how the blood pressure of a subject can be monitored using two ambulatory blood pressure monitors (ABPMs) (Al and A2), for example in combination with two observers (Ol and 02).

FIG. 1C is a digital image showing measurement of an individual's blood pressure using a dual monitor protocol (DMP). Shown are two ABPMs (Al and A2) in combination with two observers (Ol and 02).

FIGS. 2A-C are Bland-Altman scatterplots demonstrating variations in diastolic blood pressure from two ABPMs recording same arm blood pressures simultaneously in a labile hypertensive male in a (A) supine, (B) seated, or (C) standing position. FIGS. 3A-C are Bland-Altman scatterplots showing the variation in diastolic blood pressure readings from (A) two observers or (B) two ABPMs, and (C) a comparison of the results. FIG. 4A is a graph showing the diastolic blood pressure over 24 hours in a subject who is standing with a relaxed arm.

FIG. 4B is a bar graph comparing observers' and ABPMs' simultaneous measurements of blood pressure in subjects with arms either relaxed at the side or elevated at the phlebostatic axis (at heart level).

FIG. 4C is a bar graph comparing the simultaneous readings obtained from observers and ABPMs in the same arm of subjects who were supine, seated, or standing.

FIG. 4D is a graph is which compares uncorrected 24-hour ABP values with observer-corrected 24-hour ABP values in a medicated hypertensive. Each data point in the 24-hour period was corrected according to simultaneous, same arm BP differences between the ABPM and observers using a mercury column prior to the subject's field testing.

FIG. 5 are graphs showing that the Korotkoff sound (K-sound) intensity changes with body and arm position and activity.

FIG. 6 is a schematic drawing of a three axis inclinometer (such as a triple- beam level) that is one example of a means that can be used to detect the position/posture of a subject. In some examples, an intermediate step between acceleration and position is velocity. FIGS. 7 A and 7B are schematic drawings showing how an accelerometer can be used to detect the position of a subject.

FIGS. 8A and 8B are particular embodiments of the disclosed blood pressure monitoring device.

FIG. 9 is a flow chart of a particular example of the disclosed blood pressure measuring method.

FIG.- 10 is a flow chart of a particular example of the disclosed blood pressure measuring method, for example for correcting blood pressure measurements manually.

FIG. 11 is a flow chart of a particular example of a device that can be used to automate correction of blood pressure measurements after they are obtained by an ABP device, for example correction based on the posture (or activity) of the subject at the time of the blood pressure measurement. FIG. 12 is a flow chart of a particular example of the disclosed blood pressure measuring method, for example for automating correction of blood pressure measurements after the measurements are recorded.

FIG. 13 is a diagram showing how auscultatory and oscillometric sensors can be used to measure blood pressure, for example simultaneously. The lines shown in the auscultatory method are representative of K-sounds detected. The bars shown in the oscillometric method are representative of pulsations detected in the cuff.

FIG. 14 is a flow chart of a particular example of a device that can be used to obtain blood pressure measurements from an auscultatory ABP device after sensor sensitivity has been adjusted, for example adjusted based on the posture (or activity) of the subject at the time of the blood pressure measurement.

FIG. 15 is a flow chart of a particular example of the disclosed blood pressure measuring method, for example for obtaining blood pressure measurements from an auscultatory blood pressure device after sensor sensitivity has been adjusted.

FIG. 16 is a flow chart of a particular example of a device that can be used to obtain blood pressure measurements from an ABP device after auscultatory and oscillometric sensor sensitivity has been adjusted, for example adjusted based on the posture (or activity) of the subject at the time of the blood pressure measurement. FIG. 17 is a flow chart of a particular example of the disclosed blood pressure measuring method, for example for obtaining blood pressure measurements from an ABP device that includes auscultatory and oscillometric sensors whose sensitivity can be adjusted based on the posture (or activity) of the subject, prior to obtaining a blood pressure measurement. FIG. 18 is a diagram showing an exemplary blood pressure cuff that includes auscultatory and oscillometric sensors, which can be used for example in the device shown in FIG. 16 and in the method shown in FIG. 17.

FIG. 19 is a diagram showing an exemplary blood pressure device, for example one that can receive and process signals from both auscultatory and oscillometric sensors. DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS Abbreviations and Terms

The following explanations of terms and methods are provided to better describe the present disclosure and to guide those of ordinary skill in the art in the practice of the present disclosure. The singular forms "a," "an," and "the" refer to one or more than one, unless the context clearly dictates otherwise. For example, the term "comprising a posture detector" includes single or plural posture detectors and is considered equivalent to the phrase "comprising at least one posture detector." The term "or" refers to a single element of stated alternative elements, a combination of two or more elements, and both, unless the context clearly indicates otherwise. As used herein, "comprises" means "includes." Thus, "comprising posture or activity," means "including posture, activity, or posture and activity," without excluding additional elements.

Unless explained otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, exemplary methods and materials are described below. Also, unless clearly stated or understood from the context, the order of performing method acts can be varied from the order described in the examples below. The materials, methods, and examples are illustrative only and not intended to be limiting.

ABP: ambulatory blood pressure

DBP: diastolic blood pressure DMP: dual monitor protocol

K-sound: Korotkoff sound

MAP: mean arterial pressure

SBP: systolic blood pressure

SE: seated ST: standing

SU: supine At the time of the blood pressure measurement: Can include the moment when blood pressure is measured, for example by an ABP device, or a time shortly before or after such a measurement. In particular examples, includes the time +/- one minute of the measurement, such as +/- 30 seconds, or +/- 10 seconds. Blood pressure device: An apparatus that can be used to measure the pressure of the circulating blood against the walls of the blood vessels (such as arteries or veins) that results from the systole of the left ventricle of the heart.

Coupled: Includes both direct connection of one element to another and indirect connection of one element to another with one or more intermediate elements.

Positional device or posture detector: A detector or sensor used to determine or indicate the posture or body position of a subject. For example, such devices can be used to determine if the subject is seated, standing, or lying down (supine). Examples include an accelerometer (for example as shown in FIGS. 7 A and 7B) and an inclinometers, such as a triple-beam level (for example as shown in FIG. 6). Exemplary posture detectors are available from Advanced Orientation Systems, (Linden, NJ) and Analog Devices, Inc..

Subject (or individual): Living multi-cellular vertebrate organisms, a category that includes human and non-human mammals, such as veterinary subjects. Exemplary veterinary subjects include laboratory animals (such as mice, rats, rabbits, and non-human primates), livestock (such as cows, horses, and pigs), and pets (such as dogs, cats and ferrets). In a particular example, a subject is one that is semi-bipedal (for example primates), hi a specific example, a subject is one who is anaesthetized or instrumented non-primate animals (for example by a direct chronic catheterization).

Methods for Measuring Blood Pressure

Currently available methods and devices for ambulatory blood pressure (ABP) monitoring often produce inaccurate readings, such as underestimating diastolic blood pressure (DBP). It is believed that this underestimation and variability produced by the currently available devices is due to one or more of: (1) lack of active sensor/microphone calibration, that is, static or one-time calibration with constant set sensor sensitivity, which is immutable once a blood pressure device is issued from the manufacturer, (2) for each particular subject, an individualized office calibration that remains constant once the subject begins field testing, and (3) an adjusting gain mechanism, which changes the sensitivity of the sensor but is retroactive in nature.

Korotkoffox blood pressure sound intensity changes with body position and activity level, hi accordance with one aspect of the disclosure, posture or activity level (or both) of the subject at the time the blood pressure is measured (or shortly before or after such measurement) is used to correct blood pressure measurements after they are obtained from an ABP device, or used to adjust sensor sensitivity prior to measuring blood pressure. It is shown by several examples herein that two identical models of one popular ABP device, when measuring same arm pressures simultaneously, can predict each other's diastolic pressures correctly less than VT. to 2/3 of the time. In accordance with one example, blood pressure measuring devices and methods are disclosed that take into account a subject's position (such as the subject's posture or body position) to obtain corrected blood pressure measurements. One specific example of this type is a postural ambulatory blood pressure monitor (pABPM). The subject's physical activity at the time of the blood pressure measurement (for example shortly before or after the measurement) can also be taken into account in accordance with one example of the disclosure. The examples can utilize a dual monitor protocol (DMP) for evaluating the validity and reliability of blood pressure measurements and of blood pressure measuring devices. One specific exemplary embodiment includes a pABPM with DMP. In particular examples, the disclosed methods provide a more accurate measurement of blood pressure than the blood pressure determined using currently available blood pressure devices (such as ABP monitors), for example a more accurate measurement than in the absence of a correction or adjustment, hi a more specific example, the disclosed methods provide a more accurate measurement of DBP than the DBP determined using currently available blood pressure devices (such as ABP monitors), such as an increase in accuracy of at least 30% (for example the accuracy in some cases can be improved by at least 40%, at least 50%, or even at least 60%, or a range such as 30-60%).

Methods for measuring blood pressure are provided. In particular examples, the method results in a more accurate blood pressure measurement. For example, a blood pressure measurement can be adjusted to account for the position or activity of the subject. In some examples, the blood pressure measurement is corrected after the blood pressure measurement is obtained, and in other examples, the sensitivity of one or more sensors is adjusted before the blood pressure measurement is made (resulting in an outputted blood pressure value that is more accurate). The resulting blood pressure measurement is generally more accurate than the blood pressure measurement in the absence of such a correction or adjustment. In particular examples this adjustment corrects the underestimation of blood pressure (such as DBP) often observed with ABP monitors.

In one example, the method includes determining a correction factor for one or more body postures (or activities) and using the appropriate correction factor to correct the blood pressure measurement obtained from an ABP device based on the body position (or activity) of the subject. For example, the method can be a manual method, wherein the blood pressure measurements obtained from the ABP device are analyzed subsequent to the data collection period (for example using a correction algorithm). For example, the method can include determining a correction factor for a plurality of body postures (or activities), measuring blood pressure over time using an ABP device, recording the posture (or activity) of the subject at the time of the blood pressure measurement (or shortly before or after the measurement), coding the blood pressure measured to indicate the body position (or activity) of the subject at the time of the measurement, and computing the corrected blood pressure using the correction factor, and thereby generating a coded blood pressure measurement, hi another example, the method is automated, for example wherein the correction of the blood pressure measurements obtained from the ABP device over time is automated. For example, the method can include determining a correction factor for a plurality of body postures (or activities) and inputting the correction factor(s) into a calculator device, measuring a blood pressure using an ABP device and transmitting the measurement to the calculator device, recording the posture (or activity) of the subject (for example using an accelerometer) at the time of the blood pressure measurement (or shortly before or after the measurement) and transmitting the measurement to the calculator device, wherein the calculator device determines which correction factor to apply to the blood pressure measurement based on the body posture (or activity) information received. The calculator device can report a corrected blood pressure measurement that takes into account the body position (or activity) of the subject at the time of the measurement (or can also report the uncorrected blood pressure measurement). Additional methods are provided that result in a blood pressure measurement that is more accurate, due to adjustment of sensor sensitivity prior to obtaining the measurement. In one example, the method includes determining a sensor sensitivity for one or more body postures (or activities) and using the appropriate sensor sensitivity to adjust a sensor prior to measuring blood pressure measurement by an ABP device. Such a method results in an output blood pressure measurement that takes into account body position (or activity), hi particular examples, such methods can also be used to determine the heart rate of the subject.

In one example, the method uses one type of sensor, such as an auscultatory sensor. In particular examples the method includes determining sensor sensitivity for a plurality of body positions (or activities). A signal or other output is measured from one or more positional devices (also referred to herein as posture detectors) associated with the subject, and based on the output from the positional device, adjusting the sensor to the appropriate setting based on the subject's posture prior to obtaining the blood pressure measurement, hi particular examples, the positional device and the blood pressure device are parts of a single device or unit. The posture calibrated output signal from the ABP device is measured, thereby allowing for a determination of the blood pressure of the individual. The posture (or activity) calibrated output signal obtained from the adjusted sensor provides a blood pressure of the subject, which is more accurate than a signal in the absence of such adjustment.

In other examples, the method uses a plurality of sensors, such as an auscultatory sensor and an oscillometric sensor. For example, the method can include measuring a signal from a first blood pressure device on the subject, measuring a signal from a second blood pressure device on the subject, and correlating the signal from the first and second blood pressure devices, thereby generating a correlated signal, wherein the correlated signal more accurately represents the subject's actual blood pressure condition than either individual signal from the first or second blood pressure device. In particular examples, the signals from the first and second blood pressure devices are measured substantially simultaneously. In some examples the first and second blood pressure devices are present on the same arm of the subject. For example, the method can include determining sensor sensitivity for a plurality of body positions (or activities) for both an auscultatory and an oscillometric sensor. A signal or other output is measured or detected from one or more positional devices associated with the subject (for example as part of the ABP device), and based on the output from the positional device, adjusting both the auscultatory and oscillometric sensors to the appropriate setting based on the subject's posture, prior to obtaining the blood pressure measurement. The posture calibrated output signal from both the auscultatory and oscillometric sensors is measured, thereby allowing for a determination of the blood pressure of the individual. The posture (or activity) calibrated output signal resulting from the adjusted sensors provides a blood pressure of the subject that is more accurate than a signal in the absence of such adjustment, and in some examples, more accurate than either signal alone.

Blood pressure and posture detection devices Blood pressure devices are known in the art, and some are particularly disclosed herein. However, the disclosure is not limited to specific blood pressure devices. Exemplary blood pressure devices include, ambulatory blood pressure monitoring devices, such as the Accutracker® device (SunTech Medical, Morrisville, NC) and the SpaceLabs 90202 and 90207 devices (Redmond, WA). Extended ambulatory blood pressure monitoring, such as over a 24-hour period, is possible with a number of these devices. Other examples include hospital/clinic sphygmomanometers/mercury columns, automated home table-top auscultatory sensors (such as those from SunTech Medical) and oscillometric sensors (such as those from SpaceLabs).

Posture detection devices that can provide a signal indicating the position of a subject include, but are not limited to, inclinometers and triple-beam levels (for example see FIG. 6), and electronic position-sensing devices (such as an electronic accelerometer, for example see FIGS. 7 A and 7B).

The blood pressure device(s) can be present on any appropriate location on the subject, for example a limb (such as a component of the upper (arm, forearm, hand) or lower (thigh, leg, foot) extremities), a finger, or combinations thereof. Similarly, the posture detector(s) can be present on any appropriate location on the subject, for example a limb, on the torso, or on the head (or combinations thereof).

The blood pressure device and the posture detector can be located on different parts of the subject, or on the same part of the subject. In other examples, the blood pressure device and the posture detector are part of a single device present on a subject.

Manual correction of ABP device measurements

In one example, blood pressure measurements obtained by an ABP device, such as an auscultatory or oscillometric device, are corrected manually or separately from the time blood pressure measurement are taken using a computer to make the corrections. For example, blood pressure measurements obtained over time by an ABP device can be transferred to a computer program, which takes into account the subject's body position (or activity) and the correction factors for one or more body positions (or activities), to calculate corrected blood pressure measurements. One particular example of such a method is shown in FIG. 10. The method can optionally include calibrating or adjusting the sensor sensitivity of the ABP device. Exemplary ABP devices that can be used include the Accutracker® (an auscultatory device) or oscillometric devices (such as those available from SpaceLabs). However, not all ABP devices will permit or require such an adjustment.

To obtain correction factors associated with a particular body position, blood pressure measurements are obtained from the subject using both the ABP device and a reliable cross-checking procedure for one or more postures of the subject. Blood pressure measurements can include one or more of systolic blood pressure (SBP) and DBP (which can be used to calculate the mean arterial pressure, MAP). In one example, the blood pressure measurements are obtained simultaneously using both methods. Multiple reliable cross-checking procedures and multiple ABP device readings can be obtained, for example simultaneously. Reliable cross-checking procedures include those that provide a more accurate reading of blood pressure, for example as compared to an ABPM. An exemplary reliable cross-checking procedure is using sphygmomanometers/mercury column. The blood pressure measurements can be obtained from a plurality of positions, such as at least one position, at least two positions, at least three positions, for example one, two, or three positions. In addition, a plurality of measurements can be obtained for each position, such as at least one measurement, at least two measurements, or at least three measurements, such as one, two, or three measurements for each position. Exemplary body positions include supine (SU), seated (SE), and standing (ST). In particular examples, the correction factor for body positions is determined in the order SU, SE, ST (for example with at least 1 minute between measurements). In addition to (or as an alternative to) body position, blood pressure measurements can obtained that take into account a subject's activity (for example while walking, when on a stationary bike, or when doing squats), to obtain an activity correction factor. Such a correction factor can be used to take into account errors in ABP device measurements when the subject is performing a particular activity.

Based on the blood pressure measurement obtained by the ABP device, and the reliable cross-checking procedure, a correction factor for one or more body positions (or activities) is determined. By comparing the blood pressure measurement obtained using the ABP device and the reliable cross-checking procedure (such as addition or subtraction of the measurements, for example averaged measurements), a posture (or activity) correction factor can be determined. For example, if the subject is seated and the ABP device provides a blood pressure measurement of 120/70 and the reliable cross-checking procedure provides a blood pressure measurement of 124/80, the correction factor for seated can be +4 for SBP and +10 for DBP. Li one example, averaged blood pressure measurements from the ABP device or the reliable cross-checking procedure are used to determine the posture (or activity) correction factor.

Although particular examples described herein provide for the posture (or activity) correction factor(s) to be determined prior to measuring the subject's blood pressure over the desired time period, one skilled in the art will recognize that the posture (or activity) correction factor(s) can be determined following measuring the subject's blood pressure over the desired time period (for example measurement of blood pressure using the ABP device and the reliable cross-checking procedure can be performed after the subject's blood pressure is measured over the desired time period).

The method also includes measuring the subject's blood pressure over a desired time period, for example with the same ABP device used to obtain the correction factor(s). In particular examples, the subject is in a hospital or clinic. However, the subject can be at a location remote from where the calibrating blood pressure measurements described above were obtained. The time period can be random time intervals within a time period, for example within a time period of at least one hour, at least two hours, at least 12 hours, at least 24 hours, or at least 48 hours, such as 2, 12, 24, or 48 hours. Exemplary time intervals include every 5 minutes, every 15 minutes, every 30 minutes, or every 60 minutes. The time intervals can be varied, such as by using longer intervals when the subject is in bed, to minimize sleep disruptions from measurements. Appropriate time periods and intervals can be determined by a skilled clinician.

The resulting blood pressure measurements obtained by the ABP device are stored, for example in a memory unit associated with (or separate from) the ABP device. The subject maintains a log relating to the blood pressure measurements. The log includes posture (or activity) information, as well as a correlatory to the stored blood pressure measurement. For example, the subject can record the time of the blood pressure measurement or other notation that permits correlation of the blood pressure measurement and the activity/posture recorded in the log (such as which blood pressure measurement, such as the 1^st, 5^th, or 20^th measurement), as well as information on their posture (or activity). For example, the ABP device can record the time of the measurement, but the subject record the time as well to ensure synchrony. In one example, just after the blood pressure measurement is obtained, the subject records the time blood pressure was measured (such as the time displayed on the ABP monitor) and their posture (or activity). In particular examples, the posture/activity assumed immediately after the measurement is taken (for example within one minute of the measurement) is recorded. However, in some examples, the posture/activity assumed immediately before the measurement is taken (for example within one minute of the measurement) is recorded, or the posture/activity assumed at the time the measurement was taken is recorded. In one example the log is electronic; however, the log can also be recorded on paper (or other non-electronic medium). If the subject is a veterinary subject, a human monitoring the veterinary subject can record this information. In some examples, the blood pressure measurements and the log information are transmitted to a remote location (such as a laboratory or doctor's office).

The blood pressure measurements obtained from the subject over the time period can be coded based on the information in the log. This can be done automatically (for example if the log is electronic), or can be done manually (for example if the log was recorded on paper or other non-electronic medium). For example, each blood pressure measurement is coded for a particular body position (or activity), based on the information in the log. For example if at time point 1 the subject recorded that they were sitting and the stored blood pressure reading at time point 1 was 120/80, coding would include coding the 120/80 time point 1 reading with the seated position.

The posture correction factors are then imputed, for example into a computational computer program (such as Sigma Plot). The corrected blood pressure measurements are calculated from the correction factors, log information, and blood pressure measurements obtained from the ABP device. For example, if ■ the correction factors are SU +2, SE +5, and ST +4 for both systolic and diastolic, and the blood pressure readings at time 1, 2, and 3 are 110/90, 120/86, and 112/82, and the subject was supine, seated, and standing, respectively at those times, the corrected blood pressure would be 112/92, 125/91, and 116/86. Similar calculations can be made when the correction factor is different from SBP and DBP. hi one example, SBP and DBP are corrected. Similar methods can be used to correct blood pressure measurements based on the activity of the subject (for example using an activity correction factor).

The resulting corrected blood pressure measurements can be outputted. For example, the resulting measurements can be plotted or otherwise displayed or reported for analysis, for example to determine if the subject is normotensive, pre- hypertensive, borderline hypertensive, or hypertensive. In some examples, the corrected blood pressure measurements are transmitted, for example to a laboratory or doctor's office.

Automated Correction ABP device measurements

In one example, automated methods are used to correct blood pressure measurements obtained by an ABP device, such as an auscultatory or oscillometric device. For example, a blood pressure measurement corrector, which can be a calculating device, associated with the ABP device can be used to store correction factors, and correct blood pressure measurements obtained by an ABP device, by using the stored correction factors, the determined body position or activity of the subject, and the blood pressure measurements obtained from the ABP device. The resulting output can be the corrected or uncorrected blood pressure measurements, or both. One particular example of a device that can be used to perform such a method is shown in FIG. 11 (described in more detail below), and a particular example of the method is shown in FIG. 12.

As shown in FIG. 12, the automated method can optionally include calibrating or adjusting the sensor sensitivity of the ABP device. Exemplary ABP devices that can be used include the Accutracker® (an auscultatory device) or those oscillometric devices available from SpaceLabs. However, not all ABP devices will permit or require such an adjustment.

To obtain correction factors associated with a particular body position, blood pressure measurements are obtained from the subject using both the ABP device and a reliable cross-checking procedure for one or more postures of the subject, for example as described above for the exemplary manual procedure. Similarly, activity correction factors can also be obtained to correct blood pressure measurements obtained when the subject is performing a particular activity. Based on the blood pressure measurement obtained by the ABP device, and the reliable cross-checking procedure, a correction factor for one or more body positions (or activities) is determined, for example as described above for the exemplary manual procedure. Although particular examples described herein provide for the posture (or activity) correction factor(s) to be determined prior to measuring the subject's blood pressure over the desired time period, one skilled in the art will recognize that the posture (or activity) correction factor(s) can be determined following measuring the subject's blood pressure over the desired time period (for example measurement of blood pressure using the ABP device and the reliable cross-checking procedure can be performed after the subject's blood pressure is measured over the desired time period).

The resulting correction factors, for example for SE, SU, or ST body positions, as well as for SBP, DBP, or both, are imputed into a calculating device, for example using a data entry device. For example, a keypad, keyboard, touch screen, or the like, can be used to enter the determined correction factors into the calculator device. The correction factors can be stored in the calculator device. In particular examples, a plurality of correction factors for the individual are stored in the calculator device, such as at least one, at least two, at least three, or at least four correction factors, for example 1, 2, 3, 4, 5, 6, 7, 8, or 9 correction factors. The method also includes measuring the subject's blood pressure over a desired time period, for example with the ABP device, for example as described above for the exemplary manual method. The resulting blood pressure measurements obtained by the ABP device can be stored or transferred. For example, the blood pressure measurements can be stored in a memory unit associated with (or separate from, for example in the memory of the calculator device) the ABP device. The memory can also be included in a microcontroller used for processing purposes. The blood pressure measurements can also be transferred to memory, such as incorporated into a microcontroller or a cpu of a calculating device (directly from the ABPM or from the memory), for example to permit correction of the blood pressure using the correction factor and posture of the subject. Exemplary microcontrollers that can be used (such as that can replace the memory and cpu of FIG. 11 and of FIGS. 14 and 16), include a microcontroller unit (for example MSP430 MCU from Texas Instruments), AT91SAM Smart ARM- based Microcontrollers and AVR32 32-bit MCU/DSP (both available from Atmel, San Jose, CA).

In addition, the method includes determining the posture (or activity) of the subject at a time correlating to when the blood pressure measurement was obtained. For example, a posture (or activity) detector associated with the subject (for example located on a limb or the torso of the subject) can detect the position of the subject (such as sitting, standing, or supine) at the time of the blood pressure measurement, or shortly before or after such a measurement (for example within at least two minutes of such a measurement, such as within 1 minute or within 30 seconds). The information on the posture (or activity) of the subject is transmitted to the memory or cpu (or both) of the calculating device, hi particular examples the posture (or activity) detector can be a part of the ABP device, a part of the calculator device, or a separate unit. The blood pressure measurements obtained from the subject over the time period can be automatically corrected by the calculating device, using the appropriate correction factor(s), position (or activity) of the subject at the time of the blood pressure measurement, and the blood pressure measurement determined by the ABP device. For example, if the correction factors imputed into the calculating device are SU +2, SE +5, and ST +4 for both SBP and DBP, and the blood pressure measurements obtained by the ABP device at time 1, 2, and 3 are 110/90, 120/86, and 112/82, and the position detector indicated that the subject was supine, seated, and standing, respectively at those times, the calculator would calculate a corrected blood pressure of 112/92, 125/91, and 116/86. hi one example, SBP and DBP are corrected. Similar methods can be used to correct blood pressure measurements based on the activity of the subject (for example using an activity correction factor and the activity detected by an activity detector, such as a pedometer), hi particular examples, the corrections are made in real time, hi other examples, the corrections are made at a later time, for example once all of the blood pressure measurements have been obtained by the ABP device.

The resulting corrected blood pressure measurements can be outputted, as can the uncorrected measurements. For example, the resulting measurements can be plotted or otherwise displayed or reported for analysis, for example to determine if the subject is normotensive, pre-hypertensive, borderline hypertensive, or hypertensive. In some examples, the corrected blood pressure measurements are transmitted, for example to a laboratory or doctor's office.

Auscultatory ABP device measurements

In particular examples, the disclosed method is performed using an auscultatory blood pressure device (such as the Accutracker), and the sensitivity of the auscultatory sensor (such as a piezo-electric crystal microphone) adjusted based on the position or activity of the subj ect prior to obtaining the blood pressure measurement. This permits an adjustment prior to obtaining the blood pressure measurement, and therefore the output blood pressure measurement can be one that is more accurate than in the absence of the adjustment. In particular examples, the method uses electrodes; however, they can be omitted. As shown in FIG. 13, auscultatory blood pressure measuring devices can be used to determine the blood pressure of a subject. Such methods rely on the detection of Korotkoff sounds (K-sounds) to determine the blood pressure of a subject. For example, a cuff is applied to the subject (for example to a portion of a limb, such as the upper arm) and the pressure increased. The pressure is then released, and a sensor detects the K-sounds. The pressure when the K-sounds are first detected is the SBP, and the pressure when the K-sounds end is the DBP. The mean arterial (MAP) pressure is DBP + 1/3 (SBP - DBP), or the DBP + 1/3 of the pulse pressure defined as the difference between systolic and diastolic.

An exemplary device that can be used to perform such a method is shown in FIG. 14 (and described in more detail below), and a particular example of the method is shown in FIG. 15. In particular examples, the subject is in a hospital or clinic. However, the subject can be at a location remote from where the calibrating blood pressure measurements described above were obtained.

As shown in FIG. 15, the sensitivity of the auscultatory sensor for one or more body positions or activities is determined. Blood pressure measurements are obtained from the subject using the auscultatory ABP device. Blood pressure measurements can include one or more of SBP and DBP. Multiple ABP device readings can be obtained, for example simultaneously. As described in the exemplary methods above, the blood pressure measurements can be obtained from a plurality of positions and a plurality of measurements can be obtained for each position. In addition to (or as an alternative to) body position, blood pressure measurements can obtained when the subject is performing an activity. Such a measurement can be used to determine the sensor sensitivity adjustment needed when the subject is performing a particular activity.

Based on the blood pressure measurement obtained by the auscultatory ABP device at various sensor sensitivity settings, a sensor sensitivity for one or more body positions (or activities) is determined. By determining the blood pressure measurement obtained using various sensor settings, a sensor's sensitivity for each body position or activity can be determined. For example, if at sensor sensitivity setting 1 the K-sound amplitude is above or below the limits for sensor sensitivity setting 1, the sensor sensitivity can be increased or decreased. For example, if the subject is seated and the auscultatory ABP device detects a K-sound that is above the sensor sensitivity for setting 1, the sensor sensitivity can be decreased, for example by 10-fold. This would result in a sensor sensitivity for the SE position of, for example -10 fold (and necessitate, for example, a switch to a different sensor setting, such as setting 2). Similarly, if the subject is seated and the auscultatory ABP device detects a K-sound that is below the sensor sensitivity for setting 1, the sensor sensitivity can be increased, for example by 10-fold. This would result in a sensor sensitivity for the SE position of, for example +10 fold (and necessitate, for example, a switch to a different sensor setting, such as setting 3). hi one example, averaged blood pressure measurements from the ABP device are used to determine the sensor sensitivity.

The method also includes determining the body position (or activity) of the subject, and measuring the subject's blood pressure with the auscultatory ABP device over a desired time period. For example, prior to measuring the subject's blood pressure (such as at least five seconds prior, such as at least 10 seconds prior), the body position of the subject (or whether the subject is engaged in an activity, such as walking) is determined, hi one example, the position is determined using an accelerometer or other posture detection device, and activity is detected using a pedometer or other activity detection device. Determination of the body position or activity permits selection of the appropriate sensor sensitivity setting.

If excessive motion or noise is detected (for example such that the particular body position cannot be determined), the average of the sensitivity for a plurality of postures or activities can be used. Alternatively, if no excessive motion or noise is detected, and the activity or position can be determined, the specific sensitivity setting for that activity or position is used. The auscultatory sensor sensitivity is set accordingly, and the ABP device takes a blood pressure measurement.

To determine whether there is excessive noise or motion, the following methods can be used. The amplitude threshold for the sensors (such as an auscultatory sensor or an inclinometer/posture sensor) can be previously determined, and this information stored where it is accessible. For example, an average of Korotkoff sound amplitude level can be stored, such as an average K-sound for the subject. By comparing the derived K-sounds (that is, derived from filtered raw data), to the stored average K-sounds, any extreme variance in instantaneous frequency or amplitude indicates noise problems or sampling error. For example, if the amplitude doubles between K-sounds or if the interval between K-sounds varies by a factor of 2, the data can be viewed as noise or sampling error. Specific thresholds can be determined empirically, for example by having subjects wear the device and engage in motion-excessive activities (such as picking up a bag of groceries or shoveling snow) or extreme ranges of motion (such as simple elbow flexion and extension while a measurement is taking place).

The time period over which body position (or activity) is determined and blood pressure measurements are obtained can be random time intervals within a time period, for example within a time period of at least one hour, at least two hours, at least 12 hours, at least 24 hours, or at least 48 hours, such as 2, 12, 24, or 48 hours. Exemplary time intervals include every 5 minutes, every 15 minutes, every 30 minutes, or every 60 minutes. Appropriate time periods and intervals can be determined by a skilled clinician. In some examples, R-waves are also detected, for example to determine heart rate (see below). For example, if electrodes are attached to the subject, R-waves can be detected. If R-waves are detected, heart rate can be determined. If R-waves are not detected, an error message can appear, for example indicating that the subject check electrodes or reduce activity temporarily.

The resulting blood pressure measurements (for example SBP and DBP), which are more accurate due to the adjustment of the sensor, can be are stored or recorded, for example in a memory unit associated with (or separate from) the ABP device. In addition, information on the posture (or activity) can also be stored or recorded. In some examples, the blood pressure measurements and the posture (or activity) information are transmitted to a remote location (such as a laboratory or doctor's office). The resulting blood pressure measurements can be outputted. For example, the recorded measurements can be plotted or otherwise displayed or reported for analysis, for example to determine if the subject is normotensive, pre-hypertensive, borderline hypertensive, or hypertensive. In some examples, the blood pressure measurements are transmitted, for example to a laboratory or doctor's office.

Auscultatory and Oscillometric ABP device measurements

In particular examples, the disclosed methods are performed using both an auscultatory blood pressure device and an oscillometric blood pressure device. For example, calibrations and the blood pressure measurements obtained over the time period can be obtained using an auscultatory blood pressure device, such as the Accutracker, and an oscillometric blood pressure device (such as the SpaceLabs 90202 or 90207 device). In particular examples, the method does not use electrodes attached to the subject.

As shown in FIG. 13, auscultatory and oscillometric blood pressure measuring devices can be used to determine the blood pressure of a subject.

Oscillometric methods rely on the detection of pulsations in a blood pressure cuff to determine the blood pressure of a subject. For example, a cuff is applied to the subject (for example to a limb, such as an arm) and the pressure increased. The pressure is then released, and a sensor detects the pulsations (represented by bars in FIG. 13). The pressure when the pulses first increase in intensity is the SBP, and the pressure when the pulses return to initial intensity is the DBP. An exemplary device that can be used to perform such a method is shown in FIG. 16 (and described in more detail below), and a particular example of the method is shown in FIG. 17. hi particular examples, the subject is in a hospital or clinic. However, the subject can be at a location remote from where the calibrating blood pressure measurements described above were obtained.

As shown in FIG. 17, the sensitivity of one or more auscultatory and oscillometric sensors for one or more body positions or activities is determined. Blood pressure measurements are obtained from the subject using an auscultatory and an oscillometric ABP device. Blood pressure measurements can include one or more of SBP and DBP. Multiple ABP device readings can be obtained, for example simultaneously. As described in the exemplary auscultatory ABP method above, the blood pressure measurements can be obtained from a plurality of positions and a plurality of measurements can be obtained for each position. In addition to (or as an alternative to) body position, blood pressure measurements can obtained when the subject is performing an activity. Such a measurement can be used to determine the sensor sensitivity adjustment needed when the subject is performing a particular activity.

Based on the blood pressure measurement obtained from auscultatory and oscillometric ABP devices at various sensor sensitivity settings, a sensor sensitivity for one or more body positions (or activities) is determined. By determining the blood pressure measurement obtained using various sensor settings, a sensor's sensitivity for each body position or activity can be determined.

For example, if at auscultatory sensor sensitivity setting 1 the K-sound amplitude is above or below the limits for auscultatory sensor sensitivity setting 1, the auscultatory sensor sensitivity can be increased or decreased. For example, if the subject is seated and the auscultatory ABP device detects a K-sound that is above the auscultatory sensor sensitivity for setting 1, the auscultatory sensor sensitivity can be decreased, for example by 10- fold. This would result in an auscultatory sensor sensitivity for the SE position of, for example -10 fold (and necessitate, for example, a switch to a different auscultatory sensor setting, such as setting 2).

Similarly, if the subject is seated and the auscultatory ABP device detects a K-sound that is below the auscultatory sensor sensitivity for setting 1, the auscultatory sensor sensitivity can be increased, for example by 10-fold. This would result in an auscultatory sensor sensitivity for the SE position of, for example +10 fold (and necessitate, for example, a switch to a different auscultatory sensor setting, such as setting 3). Similar methods can be used to determine the oscillometric sensor sensitivity. For example, if at oscillometric sensor sensitivity setting 1 the pulse amplitude is above or below the limits for oscillometric sensor sensitivity setting 1, the oscillometric sensor sensitivity can be increased or decreased. For example, if the subject is seated and the oscillometric ABP device detects a pulse that is above the oscillometric sensor sensitivity for setting 1, the oscillometric sensor sensitivity can be decreased, for example by 10-fold. This would result in an oscillometric sensor sensitivity for the SE position of, for example -10 fold (and necessitate, for example, a switch to a different oscillometric sensor setting, such as setting 2). Similarly, if the subject is seated and the oscillometric ABP device detects a pulse that is below the oscillometric sensor sensitivity for setting 1 , the oscillometric sensor sensitivity can be increased, for example by 10-fold. This would result in an oscillometric sensor sensitivity for the SE position of, for example +10 fold (and necessitate, for example, a switch to a different oscillometric sensor setting, such as setting 3). In one example, averaged blood pressure measurements from the ABP device are used to determine the sensor sensitivity. In addition, averaged sensor sensitivities can be used, such as an averaged oscillometric sensor sensitivity, an averaged auscultatory sensor sensitivity, or an averaged auscultatory sensor and oscillometric sensor sensitivity. The method also includes determining the body position (or activity) of the subject, and measuring the subject's blood pressure with the ABP device over a desired time period. For example, prior to measuring the subject's blood pressure (such as at least five seconds prior, such as at least 10 seconds prior), the body position of the subject (or whether the subject is engaged in an activity, such as running) is determined. In one example, the position is determined using an accelerometer or other posture detection device, and activity is detected using a pedometer or other activity detection device. Determination of the body position or activity permits selection of the appropriate auscultatory and oscillometric sensor sensitivity setting.

If excessive motion or noise is detected (for example such that the particular body position cannot be determined), the average of the sensitivity for a plurality of postures or activities can be used. For example the average of all the auscultatory sensor sensitivities can be used (such as the average of the sensitivities for SE, ST, and SU), the average of all the oscillometric sensor sensitivities can be used (such as the average of the sensitivities for SE, ST, and SU), or the average of all the oscillometric and auscultatory sensor sensitivities can be used (such as the average of the sensitivities for SE, ST, and SU for both oscillometric and auscultatory). If no excessive motion or noise is detected, and the activity or position can be determined, the specific oscillometric and auscultatory sensitivity setting for that activity or position is used. The oscillometric and auscultatory sensor sensitivities are set accordingly, and the ABP device takes a blood pressure measurement. To determine whether there is excessive noise or motion, the methods described above can be used to determine if there is excessive noise or motion detected by the auscultatory sensor. To determine whether there is excessive noise or motion detected by the oscillometric sensor, the following methods can be used. The amplitude threshold for the oscillometric sensor can be previously determined, and this information stored where it is accessible. For example, an average pulse amplitude level can be stored, such as an average pulse signal for the subject. By comparing the derived pulse signal (that is, derived from filtered raw data) to the stored average pulse signals, any extreme variance in instantaneous frequency or amplitude indicates noise problems or sampling error. For example, if the amplitude doubles between pulse signals or if the interval between pulse signal varies by a factor of 2, the data can be viewed as noise or sampling error. Specific thresholds can be determined empirically as described above.

The time period over which body position (or activity) is determined and blood pressure measurements are obtained can be random time intervals within a time period, for example within a time period of at least one hour, at least two hours, at least 12 hours, at least 24 hours, or at least 48 hours, such as 2, 12, 24, or 48 hours. Exemplary time intervals include every 5 minutes, every 30 minutes, every 15 minutes, or every 60 minutes. Appropriate time periods and intervals can be determined by a skilled clinician.

Based on the position or activity detected, the appropriate sensitivity setting (determined as described above) is selected for both the auscultatory and oscillometric sensors. The blood pressure of the subject is then measured. For example, once the oscillometric sensor detects a change in pulse, the auscultatory sensor is directed to measure K-sounds. The resulting blood pressure measurements (for example SBP and DBP), which are "corrected" due to the adjustment of the oscillometric and auscultatory sensors, can be are stored or recorded, for example in a memory unit associated with (or separate from) the ABP device. In particular examples, the average of the blood pressure measured by oscillometric sensor or the auscultatory sensor is reported, for example if one of the sensors detects excessive motion or noise, hi some examples, the averaged blood pressure measured by oscillometric sensor and the auscultatory sensor is reported, hi addition, information on the posture (or activity) can also be stored or recorded. In some examples, the blood pressure measurements and the posture (or activity) information are transmitted to a remote location (such as a laboratory or doctor's office).

The resulting corrected blood pressure measurements can be outputted. For example, the resulting measurements can be plotted or otherwise displayed or reported for analysis, for example to determine if the subject is normotensive, pre- hypertensive, borderline hypertensive, or hypertensive, hi some examples, the corrected blood pressure measurements are transmitted, for example to a laboratory or doctor's office.

Correction factor for activity and detecting activity

As described above, correction factors and sensor sensitivity settings can be calculated based on the position of the subject (such as SE, ST, or SU). Similar methods can be used to determine a correction factor or sensor sensitivity setting for one or more activities that the subject may perform when the blood pressure measurements made over time, hi addition, methods can be used to determine the activity of the subject at the time of the blood pressure measurement (for example at the time the measurement is being taken, or shortly before or after such a measurement is made). Exemplary activities include squat/knee bends (such as at least 5 of such bends, for example 5-30 of such bends), walking or jogging on a treadmill, stationary cycle ergometry or stair climbing, or holding a Tai Chi squat pose for a period of time (such as at least 30 seconds). In one example, correction factor(s) are determined for one or more activities. Such a correction factor can be used to take into account errors in blood pressure measurements obtained by an ABP device when the subject is performing a particular activity. To obtain correction factors associated with a particular activity, blood pressure measurements are obtained from the subject using both an ABP device and a reliable cross-checking procedure for one or more activities performed by the subject. Blood pressure measurements can include one or more of SBP and DBP. In one example, the blood pressure measurements are obtained simultaneously using both methods. Multiple reliable cross-checking procedures and multiple ABP device readings can be obtained, for example simultaneously. Reliable cross-checking procedures include those that provide a more accurate reading of blood pressure, for example as compared to an ABPM. The blood pressure measurements can be obtained for a plurality of activities, such as at least one activity, at least two activities, at least three activities, for example one, two, or three activities. In addition, a plurality of measurements can be obtained for each activity, such as at least one measurement, at least two measurements, or at least three measurements, such as one, two, or three measurements for each position.

In particular examples the activity performed is based on information that the subject will perform that activity at least one time over the time period when the blood pressure is monitored with the ABP device. In some examples, the activity measured is based on the condition of the subject's knees or overall ability to perform the activity. For example, orthopedically-sound subjects could do squat/knee bends, walk or jog on a treadmill, stationary cycle ergometry or stair climbing, while orthopedically-limited subject could holding a Tai Chi squat pose. Based on the blood pressure measurement obtained by the ABP device, and the reliable cross-checking procedure, a correction factor for one or more activities is determined. By comparing the blood pressure measurement obtained using the ABP device and the reliable cross-checking procedure (such as addition or subtraction of the measurements, for example averaged measurements), an activity correction factor can be determined. For example, if the subject is walking and the ABP device provides a blood pressure measurement of 120/70 and the reliable cross-checking procedure provides a blood pressure measurement of 125/80, the correction factor for walking can be +5 for systolic and +10 for diastolic. In one example, averaged blood pressure measurements from the ABP device or the reliable cross-checking procedure are used to determine the activity correction factor.

Although particular examples described herein provide for the activity correction factor(s) to be determined prior to measuring the subject's blood pressure over the desired time period, one skilled in the art will recognize that the posture (or activity) correction factor(s) can be determined following measuring the subject's blood pressure over the desired time period (for example measurement of blood pressure using the ABP device and the reliable cross-checking procedure can be performed after the subject's blood pressure is measured over the desired time period).

In another example, sensor sensitivities are determined for one or more activities. Such sensor sensitivities can be used to adjust the sensitivity of a sensor (such as an auscultatory or oscillometric sensor) prior to obtaining a blood pressure measurement from an ABP device, thereby resulting in an output blood pressure measurement which more accurately reflects the actual blood pressure in the subject. Korotkoff (K)-sound amplitude increases with activity (for example see FIG. 5). For example, the K-sound amplitude can increase from a peak of 20 mV up to 50-60 mV even after a moderate intensity activity (for example 15 squat or knee bend repetitions with a subject using only body resistance, that is, no external resistance applied). To obtain blood pressure measurements when the subject is engaged in a particular activity, such as blood pressure measurements made with a auscultatory blood pressure monitor when the subject is walking, sensor sensitivity settings can be determined for one or more activities.

In a specific example, after obtaining blood pressure measurements to determine the correction factors for each of supine (SU), seated (SE), and standing (ST) postures, subjects perform the desired activity, for example for a time sufficient to increase the K-sound amplitude above the standing posture. This increase in K- sound can be calculated and stored for further use. If desired, an additional blood pressure measurement can be made. For example after a 3-5 minute rest period, the subject can repeat the activity, for example at a greater intensity (for example increasing from 5 to 15 squat/knee bend repetitions), to increase K-sound amplitude above the standing posture. This increase can be calculated and stored for later use.

To obtain the sensor sensitivity for the activity, the sensitivity setting obtained for ST is multiplied by the reciprocal of the proportional increase in amplitude from ST to post-exercise. For example, if the K-sound amplitude increases 3-fold from standing to moderate activity, the sensitivity setting is 1/3 of the original standing sensitivity.

During the period when the ABP device is measuring blood pressure over time, activity detectors can be used to determine if the subject is engaged in activity (and thus in particular examples triggering the use of an activity correction factor or a particular sensor sensitivity), and in some examples can determine which activity is being engaged in. In some examples, activity detectors detect motion, such as an inclinometer, postural sensor, accelerometer, or pedometer activity detector.

If more detailed calibration is desired, a variety of activities can be evaluated for their ability to enhance K-sound amplitude according to MET (resting metabolic energy equivalent level, 1 MET = 3.5 mL 02/kg of body wt/min or 1.2 Kcal/min for a 70 kg adult sitting quietly). Detailed MET estimations for moderate and intense activities can be viewed on the Internet by consulting the table established by the Centers for Disease Control and American College of Sports Medicine (such as the .pdf file General Physical Activities Defined by Level of Intensity).

Measurement of heart rate

In addition to measuring blood pressure using the methods disclosed herein, heart rate can be determined, for example when using the auscultatory pABP device and the auscultatory/oscillometric ABP device methods. As shown in FIG. 13, information obtained from an auscultatory or an oscillometric ABP device can be used to measure the heart rate of a subject. In humans, bradycardia or slow heart rate is generally defined as < 60 beats/minute, and tachycardia or fast heart rate as > 100 beats/minute.

If using an auscultatory ABP device, heart rate (in beats per minute) can be determined by dividing 60 seconds by the difference in time between two consecutive R-waves. For example, IfR₁ is detected at 2 seconds and R₂ is detected at 3 seconds, 60 seconds/(3-2) = heart rate of 60 beats per minute. In addition, if using an auscultatory ABP device, heart rate (in beats per minute) can be determined by subtracting the time between two consecutive K-sounds (FIG. 13) and dividing that value by 60 seconds. For example, if K-SOiUId₁ is detected at 2 seconds and K- sound₂ is detected at 2.5 seconds, (2.5-2)/60 seconds = heart rate of 120 beats per minute. The frequency of Korotkoff sounds could range from 0 (death) to 400 (extreme tachycardia) sounds per minute, while clinically normal, resting values are generally between 60 and 100 beats/minute (for example in a human subject). If using an oscillometric ABP device, heart rate can be determined by dividing 60 seconds by the difference in time between two consecutive pulsations detected (such as the time difference between the detected start of a first pulsation and the detected start of a second pulsation). For example, if the onset of P₁ is detected at 2 seconds and the onset of P₂ is detected at 3 seconds, 60 seconds/(3-2) = heart rate of 60 beats per minute. In some examples, heart rate is calculated by averaging a heart rate obtained from an auscultatory and from an oscillometric ABP device, such as a weighted average.

Blood Pressuring Monitoring Devices Also provided by the present disclosure are blood pressuring monitoring devices. In particular examples, the devices are auscultatory ABP devices, oscillometric ABP devices, or combinations thereof. In particular examples, the blood pressure measurements reported by the claimed blood pressure monitoring devices are correlated to body position (or activity) so as to adjust or compensate for bias and variability caused by changes in an individual's posture or activity, for example by using an algorithm. Computer or microprocessor implemented algorithms can be used to accomplish the correlation. In one example, the blood pressuring monitoring apparatus includes at least one means for detecting a position (or activity) of the subject (for example a posture detector means), for example two posture or activity detectors, and at least one means for detecting a representative blood pressure of the subject (such as an ABP device), which are coupled to a calculator device. The calculator device permits the storage of information (such as in memory or in a memory device) and the permits manipulation and reporting (such as transfer or printing) of information (such as by a microcontroller or a cpu). For example, the posture detector and the means for measuring the subject's representative blood pressure can be coupled (directly or indirectly) to the cpu of the calculator device. These connections can include a signal conditioning circuit. In one example, the means for detecting a position of the subject is part of the calculating device. However, it can also be separated from the calculating device.

In another example, the blood pressure monitoring apparatus includes at least one means for detecting a representation of blood pressure of a subject, at least one means for detecting a position (or activity)of the subject, and at least one means for adjusting the representation of blood pressure depending on the position of the subject, such as a calculating device. In some examples, the representation of blood pressure is increased if the position of the subject is standing. A particular example of such an embodiment is shown in FIG. 8B.

For example, a blood pressure monitoring device can include at least one posture detector for sensing the body position (or activity) of the subject and operable to produce at least one body position (or activity) indicating output signal, at least one calculator device operable to receive the at least one body position (or activity) indicating output signal and operable to convert the sensed blood pressure output signal corresponding to sensed blood pressure in a subject to a corrected blood pressure measurement signal based on the body position (or activity), and at least one blood pressure sensor operable to produce at least one sensed blood pressure output signal corresponding to sensed blood pressure in a subject, wherein the corrected blood pressure output signal more accurately represents the subject's actual blood pressure condition than in the absence of calibration. A particular example of such an example is shown in FIG. 11. In particular examples the device further includes a data entry device to provide a means for entering correction factors or sensor sensitivity settings for one or more postures or activities into the calculator device. For example, a blood pressure monitoring device can include at least data entry device for entering correction factors or sensor sensitivity settings and operable to transmit such information to the calculator device (such as the memory means). Exemplary data entry devices include keypads, keyboards, touch screens, and the like. The data entry device can be part of the calculator device, or can be separate.

In particular examples the device further includes at least one means for adjusting a blood pressure sensor depending on the position or activity of the subject. The blood pressure sensor can be an auscultatory sensor (one that permits detection of K-sounds, such as a piezo-electric curved crystal) or an oscillometric sensor (one that permits detection of pulses in a blood pressure cuff, such as a transducer). For example, the means for adjusting a blood pressure sensor depending on the position or activity of the subject can be used to change the sensitivity setting for one or more sensors.

For example, a blood pressure monitoring device can include at least one posture (or activity) detector for sensing the body position (or activity) of the subject and operable to produce at least one body position (or activity) indicating output signal, at least one blood pressure monitor sensor adjustor operable to receive the at least one body position (or activity) indicating output signal and operable to calibrate (for example change) the sensor setting depending on at least one body position (or activity) indicating output signal, and at least one blood pressure sensor operable to produce at least one sensed blood pressure output signal corresponding to sensed blood pressure in a subject, wherein the sensed blood pressure output signal' more accurately represents the subject's actual blood pressure condition than in the absence of calibration. Particular examples of such a device are shown in FIGS. 14 and 16.

Another example of the disclosed blood pressure monitoring apparatus includes at least one ABP operable to produce at least one sensed blood pressure output signal corresponding to sensed blood pressure in a subject, at least one body position sensor for sensing the body position of the subject and operable to produce at least one body position indicating output signal, at least one blood pressure correlator operable to receive the at least one sensed blood pressure output signal and the at least one body position indicating output signal, the blood pressure correlator providing a second blood pressure output signal corresponding to the at least one sensed blood pressure output signal that has been modified to compensate for the effect of body positions on the sensed blood pressure output signal such that the second blood pressure output signal more accurately represents the subject's actual blood pressure condition than the at least one sensed blood pressure output signal. One particular example of such an algorithm that can be used to adjust sensor sensitivity prior to taking a blood pressure measurement is as follows. The postural- adjusting ABP device (pABP) can include microphone sensitivity calibrations for each of multiple unique body positions: such as supine (SU), seated (SE), and standing (ST) positions. The pABP can use an accelerometer or 3-D balance sensor to detect a subject's body position prior to each measurement during a time period (such as over a 24-hr period). Prior to using the pABP device, calibrations (such as two calibrations) are made for each body position (SU, SE, ST), and at least one minute transpires between each calibration measurement to ensure normal flow and to prevent reactive hyperemia caused by repeated cuff inflations. The average of the calibrations for each body posture is stored in the pABP, such as in a matrix storage array. Also, during the calibration period, at least 5 minutes can transpire between changes in posture, for example to ensure that relative pressure homeostasis/equilibrium is maintained and acute transitions which occur due to baroreceptor reflex responses to changes in posture are minimized. During a monitoring period, immediately prior to each measurement (for example no more than 10 seconds), the pABP determines the subject's posture by the posture detection device (such as an accelerometer/3-D sensor) and the microphone's sensitivity is automatically switched to the appropriate calibration based on the subject's posture (or activity). To minimize noise/interference, the microphone can use R-wave gating of K-sounds, for example the sensor is only open for a measurement just prior to and just after the R-wave in each EKG record. If just prior to a measurement, the pABP is unable to certify the subject's posture, the average of the calibrations (such as SU, SE, ST) can be used. This measurement is noted with a code in the matrix array and report printout indicating that an average of the calibrations was used.

Not including the calibration period or potential repeats due to error codes, the pABP device in one exemplary form can store up to 288 measurements in a 24- hr period or 576 measurements in a 48-hr period (if measurements are taken every 5 minutes). More or fewer measurements can be stored. Data in a matrix array with these variables in the following columns: (1) time (hr:min), (2) measurement number (1-6 calibration, >7 field testing), (3) posture/calibration sensitivity setting (code: I=SU, 2=SE, 3=ST, or 4=Average Calibration/X), (4) systolic blood pressure (SBP, mm Hg, pressure corresponding to first Korotkoff sound detected by microphone), (5) diastolic blood pressure (DBP, mm Hg, pressure corresponding to last Korotkoff sound), (6) estimated mean arterial blood pressure (MAPest = 1/3 (SBP-DBP) + DBP), (7) estimated pulse pressure (PP = SBP - DBP), (8) heart rate (bpm) as determined by average time elapsed in seconds between EKG R- waves during which the corresponding Korotkoff sounds are assessed, divided into 60, (9) EKG regularity/irregularity codes including those which note excessive noise (code 0), and double-peaked R-waves (code 1) or large T-waves (code 2) which can arbitrarily double the heart rate (other codes for column #9, codes 3-10 TBA), and (10) machine error codes or repeat measurements due to errors detected (* for average sensitivity setting, and #s 1-10 for unique measurement or error report).

If an average postural calibration is used or errors are detected, then a repeat measurement is taken, for example after 1 minute has transpired. This measurement is noted as a repeat measurement in the records column 10 of the matrix array. Following a recording period, an abbreviated version of each individual data record can be displayed on the monitor (time, measurement #, SBP, DBP, HR, Error codes). Alternatively (and desirably), the monitor is connected to a computer and/or pABP device report printer by way of an interface and field data is downloaded, individual data points are plotted, 24-hr or 48-hr averages are calculated, and the subject's data is classified via a special software package. Classifications range from normotension to Stages IV hypertension based on National Heart Lung and Blood Institute Guidelines. A particular example of such an example is shown in FIGS. 9 and 15.

In another example, two or more ABP monitors, such as an oscillometric and an auscultatory ABP₅ are used to create a dual ABP monitoring device. The dual device desirably generates two simultaneous measurements of same-arm blood pressure. A particular example of such an example is shown in FIG. 17.

Automated correction ABP device

Li one example, the ABP device includes coupled features that permit automation for correcting blood pressure measurements obtained by the ABP device, such as an auscultatory or oscillometric device. The coupled features can be part of the ABP device, or directly or indirectly coupled to the ABP device. One particular example of a device that can be used to perform such a method is shown in FIG. 11. As shown in FIG. 11, the device includes a data entry device used to enter the subject's posture or activity correction factors into the calculator device. One or more posture (or activity) correction factors can be entered, such as a plurality of correction factors, for example correction factors for SU, SE, ST (or combinations thereof, such as 1, 2 or 3 of these). Correction factors can include corrections for SBP, DBP, or combinations thereof, such as 1 or 2 of these. The data entry device can be any device that permits entry of the correction factor into the calculator device, such as a keypad, keyboard, touch screen, or any other similar device. The data entry device can be part of the calculator, or can be attached thereto (as shown in FIG. 11). In one example, the data entry device is removably attached to the calculator device. The data entry device is in communication with a microcomputer, such as a memory device of the microcomputer. This permits storage of the correction factors in the microcomputer, such as a calculator device. The calculator device can include a memory device that permits storage of information, and a microcontroller (such as a cpu) that permits processing of information, for example calculation of corrected blood pressure. The memory device and the cpu are connected to permit transfer of information between them. For example, correction factors stored in the memory can be transferred to or accessed by the cpu. Optionally, the calculator device can include a posture detector (such as an accelerometer) or an activity detector (such as a pedometer). However, the posture or activity detector can be a separate device in communication with the cpu of the calculator, or can be part of the ABP device and in communication with the cpu of the calculator. The ABP device can be any one that permits blood pressure measurements over time. Examples include auscultatory and oscillometric devices, such as the Accutracker® (an auscultatory device) and oscillometric devices available from SpaceLabs. The ABP device is coupled to the microcomputer (such as the cpu or memory) to permit transfer of the blood pressure measurements obtained for the subject by the ABP device to the calculating device.

Coupling between the ABP device and the posture (or activity) detector with the cpu of the calculator can include a signal conditioning circuit, for example between the posture (or activity) detector and the cpu and between the ABPM and the cpu. The cpu determines the corrected blood pressure measurement received from the ABP device, by using the correction factor imputed by the data entry device, and the posture (or activity) information from the posture (or activity) detector. For example, at the time of the blood pressure reading (or shortly before or after, such as +/- no more than one minute), the posture (or activity) detector sends information to the cpu indicating the body position (or activity) of the subject at the time of the blood pressure measurement (or shortly before or after), and the cpu can correct the blood pressure measurement obtained by the ABP device using the appropriate stored correction factor. For example, if the posture detector indicates the subject was seated at the time of the measurement, the seated correction factor is used to correct that blood pressure measurement.

The corrected blood pressure measurements can be outputted, for example displayed, reported, transmitted, or printed for analysis. For example, the outputted measurement can be used to determine the blood pressure status of the subject. In one example, the outputted blood pressure measurements are not corrected. For example, non-corrected and corrected blood pressure measurements can be outputted. Device for auscultatory blood pressure measurement

In one example, the ABP device includes coupled features that permit automatic adjustment of auscultatory sensor sensitivity, thereby permitting more accurate blood pressure measurements obtained by an auscultatory ABP device. For example, auscultatory sensor sensitivity can be adjusted based on the position or activity of the subject at the time of the blood pressure measurement. The coupled features can be part of the ABP device, or directly or indirectly coupled to the ABP device. One particular example of a device that can be used to perform such a method is shown in FIG. 14. As shown in FIG. 14, the device includes a data entry device used to enter the subject's sensor sensitivity for each body position or activity into the calculator device (such as a microcomputer). One or more posture sensor sensitivities can be entered, such as a plurality of correction factors, for example a sensor sensitivity for SU, SE, ST (or combinations thereof, such as 1, 2 or 3 of these). Similarly, one or more activity sensor sensitivities can be entered. The data entry device can be part of the calculator device (such as a keypad or touch screen on the calculator device), or can be attached to the calculator device (as shown in FIG. 14).

The data entry device permits entry of the sensor sensitivity settings into the calculator device, thereby permitting storage and retrieval of the sensor sensitivity settings. As described above, the calculator device can include memory that permits storage of information, and a cpu that permits processing of information.

The device also includes an auscultatory ABP device. The auscultatory ABP device can be any ambulatory auscultatory blood pressure monitor that permits blood pressure measurements over time. Examples include the Accutracker®. The auscultatory ABP device can be in communication with the calculator device, for example to permit transfer or storage of the blood pressure measurements obtained to the calculating device. Coupling between the auscultatory blood pressure monitor and the calculator can include a signal conditioning circuit.

The auscultatory ABP device is also in communication with a blood pressure cuff, for example via a pump that permits inflation and deflation of the cuff. The cuff includes one or more auscultatory sensors, such as those that permit detection of K-sounds. In some examples, the auscultatory sensor is in communication with the calculator device, for example to permit adjustment of the sensitivity of the sensor, based on the detected posture or activity of the subject prior to the blood pressure measurement. The device can include one or more posture detectors (such as an accelerometer or inclinometer), one or more activity detectors (such as a pedometer). These detectors permit the posture or activity of the subject to be determined, for example prior to the blood pressure measurement, and based on this information, the sensor sensitivity selected and adjusted accordingly.

The calculator can determine the appropriate auscultatory sensor sensitivity to be selected, by using the correction factor imputed by the data entry device, and the posture (or activity) information from the posture detector (or activity). For example, if prior to the time of the blood pressure reading (such as about 10 seconds prior), the posture detector (or activity) sends information to the cpu indicating the body position (or activity), and the cpu can then emit a signal that will adjust the auscultatory sensor sensitivity using the appropriate stored sensitivity setting. For example if the posture detector detects that subject is standing, the auscultatory sensor sensitivity is adjusted to the standing sensitivity prior to obtaining a blood pressure measurement by the ABP device (for example before or during inflation of the cuff).

The blood pressure measurements can be outputted, for example displayed, reported, transmitted, or printed for analysis. For example, the outputted measurement can be used to determine the blood pressure status of the subject.

Device for auscultatory/oscillometric blood pressure measurement

In one example, the ABP device includes coupled features that permit adjustment of both oscillometry and auscultatory sensor sensitivity, thereby permitting more accurate blood pressure measurements obtained by an ABP device. For example, the sensor sensitivity of both an oscillometric and auscultatory sensor can be adjusted based on the position or activity of the subject at the time of the blood pressure measurement. The coupled features can be part of the ABP device, or directly or indirectly coupled to the ABP device. One particular example of a device that can be used to perform such a method is shown in FIG. 16. As shown in FIG. 16, the device includes a data entry device used to enter the subject's oscillometric and auscultatory sensor sensitivity for each body position or activity into the calculator device (such as a microcomputer). One or more posture sensor sensitivities can be entered, such as a plurality of correction factors, for example a sensor sensitivity for SU, SE, ST (or combinations thereof, such as 1, 2 or 3 of these). Similarly, one or more activity sensor sensitivities can be entered. The data entry device can be part of the calculator device (such as a keypad or touch screen on the calculator device), or can be attached to the calculator device (as shown in FIG. 16). The data entry device permits entry of the oscillometric and auscultatory sensor sensitivity settings into the calculator device, thereby permitting storage and retrieval of the oscillometric and auscultatory sensor sensitivity settings. As described above, the calculator device can include memory that permits storage of information, and a cpu that permits processing of information. The device also includes an ABP device, which is associated with both oscillometric and auscultatory sensors. The ABP device can be any ambulatory blood pressure monitor that permits blood pressure measurements over time. The ABP device can be in communication with the calculator device, for example to permit transfer or storage of the blood pressure measurements obtained to the calculating device. Coupling between the auscultatory blood pressure monitor and the calculator can include a signal conditioning circuit.

The ABP device is also in communication with a blood pressure cuff, for example via a pump that permits inflation and deflation of the cuff. The cuff includes oscillometric and auscultatory sensors (such as at least one of each). In some examples, the sensors are in communication with the calculator device, for example to permit adjustment of the sensitivity of the sensors, based on the detected posture or activity of the subject prior to the blood pressure measurement. The device can include one or more posture detectors (such as an accelerometer or inclinometer), one or more activity detectors (such as a pedometer). In a particular example, the device includes two posture detectors. These detectors permit the posture or activity of the subject to be determined, for example prior to the blood pressure measurement, and based on this information, the sensor sensitivity of both the oscillometric and auscultatory sensors are selected and adjusted accordingly.

The calculator can determine the appropriate oscillometric and auscultatory sensor sensitivities to be selected, by using the correction factor(s) imputed by the data entry device, and the posture (or activity) information from the posture detector (or activity). For example, if prior to the time of the blood pressure reading (such as about 10 seconds prior), the posture detector (or activity) sends information to the cpu indicating the body position (or activity), and the cpu can then emit a signal that will adjust the oscillometric and auscultatory sensor sensitivities using the appropriate stored sensitivity setting. For example if the posture detector detects that subject is standing, the oscillometric and auscultatory sensor sensitivities are adjusted to the standing sensitivity prior to obtaining a blood pressure measurement by the ABP device (for example before or during inflation of the cuff).

Blood pressure cuff

FIG. 18 shows an exemplary blood pressure cuff that can be used in the methods disclosed herein (for example FIG. 17), and can be part of the devices disclosed herein (for example FIG. 16). The artery shown is not part of the device, but shown for reference purposes. Although the shape of the cuff in FIG. 18 is conical, one skilled in the art will appreciate that other shapes can be used, such as cylindrical. In addition, although particular measurements are provided in FIG. 18, one skilled in the art will appreciate that changes can be made, without significantly interfering with the ability of the cuff to perform its function. For example, the cuff can be scaled up or down to accommodate a variety of sized subjects (such as a cuff that can be used on large adults, adults, small adults, pediatric subjects, and neonatal subjects). Similarly, the cuff can be scaled to accommodate veterinary subjects. As shown in FIG. 18, the cuff includes a plurality of sensors, such as an auscultatory and an oscillometric sensor. An exemplary auscultatory sensor is a piezo-electric sensor curved crystal microphone, and an exemplary oscillometric sensor is a pressure transducer. Although an arcuate-shaped sensor is shown and provides a particularly good fit to the contour of a subject's arm, one skilled in the art will appreciate that other sensor shapes can be used, such as rectangular, square, oval, or circular shaped-sensors. In particular examples the oscillometric sensor location is one that permits it to traverse the desired artery, such as the brachial artery. In some examples the auscultatory sensor location is one that permits it to traverse the desired artery, such as the brachial artery. A specific exemplary orientation is to position an arcuate sensor so as to be skewed transverse relative to the longitudinal axis of a cuff when the cuff is positioned on a subject's arm with the sensor carried by the cuff. Such an orientation can permit the sensor to better contour the shape of the arm. The cuff can also include a rubber bladder, for example internal to the cuff, hi some examples, the cuff can further include guide strips, for example to assist in placement of the cuff on the subject.

The auscultatory and oscillometric sensors associated with the cuff can be stabilized directly over the desired artery (such as the brachial artery) using a variety of methods. Exemplary methods include directly adhering the sensors to the subject's limb (such as the arm) by using an adhesive pad open on one side and closed on the opposing side or by inserting each sensor into a tightly contoured, light-weight sleeve in the deep/internal side of the conical cuff (that is, the cuff side in direct contact with the subject's limb). Exemplary adhesive sensor pads can include a contour cutout for embedding, fixing, and protecting the sensor on the superficial/external side, while permitting direct contact with the subject's skin on the deep/internal side. Spandex (or other similar stretchable material) can be a component of the light-weight, contoured, cloth sensor sleeves. When this material is placed upon stretch and secured, a secure, stable and protected position for each sensor can be ensured. Sensor pads and sleeves can be angled such that their midpoints course directly over the desired artery (such as the brachial artery).

Example 1 Measurement of Blood Pressure with Two Monitors

Two dual-monitor protocols were used to determine the accuracy and reliability of ambulatory blood pressure monitors (ABPMs). As shown in FIGS. IA-C, these methods permit simultaneous, same arm measures by two ABPMs (Al, A2) in the field, or 2 ABPMs & 2 audiologically-tested, trained observers (01, 02) in the laboratory.

The blood pressure of a labile hypertensive male was determined using two ABPMs. It was observed that the level of agreement for the two ABPMs varied significantly according to body position, with the lowest level of agreement for standing diastolic pressure (DBP) (FIGS. 2 A-C). The highest degree of variability was observed for standing measurements (FIG. 2C) where one ABPM on average underestimated the other by about 2 mm Hg, yet varied by as much as 15 mm Hg above or 18 mm Hg below for about 95% of the measurements. For systolic pressure (SBP), both ABPMs had a shared variance of 85%, but for DBP only 52%.

These results indicate that correction of blood pressure readings is needed, to take in consideration the position of the individual when the reading is made.

Example 2

Blood Pressure Readings From ABPMs vs. Observers

Blood pressure readings in 15 normotensives were obtained from two ABPMs (Al and A2, FIG. 1) and from two trained observers (Ol and 02, FIG. 1).

As shown in FIGS. 3 A and 3B, the blood pressure readings from the observers had a higher level of agreement than did the ABPMs. In addition, as shown in FIG. 3C, the ABPMs underestimated (PO.001) the DBP readings obtained by the observers by 5 mm Hg, and predicted < 50% of the observer DBP variance. Observers shared DBP variance was 95%, while ABPMs was 69%.

Therefore, blood pressure readings obtained from ABPMs appear to underestimate actual blood pressure values, especially DBP values.

Example 3 ABPMs Can Underestimate Blood Pressure

Blood pressure readings were obtained in 14 normotensives, as well as medicated and nonmedicated hypertensives using two ABPMs and two observers.

As shown in FIGS. 4A-D, the ABPMs in this example significantly underestimated observers' DBP and that this varied according to posture & arm position. Standing, relaxed arm laboratory measurements provided the most accurate prediction of 24-hour pressures.

These results indicate that ABPMs may indicate falsely normotension (e.g., DBP=83 mm Hg) when the reality is hypertension (e.g., DBP=93 mm Hg). This may lead to misdiagnosis and mismanagement.

Example 4 Algorithm to Adjust Sensor Sensitivity

To address the ABPM measurement problems discussed in the above examples, methods and devices are provided that permit adjustment of an auscultatory sensor (or both an oscillometric and an auscultatory sensor) prior to obtaining a blood pressure reading by an ABP device. For example, the sensor(s) can be adjusted based on the position or activity of the subject detected. This example describes a statistical model that can be used to adjust sensor sensitivity. Korotkoff sound intensity was observed to change with body and arm position, as well as activity (FIG. 5). To adjust for this change, a postural or activity adjustment is made. For example, an inclinometer (FIG. 6) or a 3-D balance or accelerometer (FIGS. 7A and 7B) can be used to determine the position of the subject, while a pedometer can be used to detect activity. The sensitivity of one or more sensors associated with a blood pressure monitor is calibrated for one or more body positions (or activities), such as supine (SU), seated (SE), and standing (ST). The ABP device can include one or more sensors to detect an individual's body position (or activity) prior to each blood pressure measurement. The sensor can be part of a blood pressure monitor, or can be capable of sending a signal indication the subject's body position to the blood pressure monitor, hi particular examples an accelerometer or 3-D balance sensor to detect a subject's body position.

For each body position (SU, SE, ST), at least two calibrations are made for each type of sensor. Ideally, at least 1 minute transpires between each calibration measurement to ensure normal flow and to prevent reactive hyperemia caused by repeated cuff inflations. The average of the two calibrations for each body posture is stored in the ABP device a matrix storage array. During the calibration period, ideally at least 5 minutes transpires between changes in posture, to ensure that relative pressure homeostasis equilibrium is maintained and acute transitions which occur due to baroreceptor reflex responses to changes in posture are minimized.

During a 24-hour monitoring period, immediately (such as 10 seconds) prior to each measurement, the ABP device determines the subject's posture (or activity), for example by way of the built-in accelerometer/3-D sensor, and the sensitivity of one or more sensors is switched to the appropriate calibration based on the subject's posture (or activity). To minimize noise/interference, the auscultatory sensor can use R- wave gating of K-sounds, in that it can only detect sounds (or is only "open" for a measurement) just prior to and just after the R- wave in each EKG record.

If just prior to a measurement, the device is unable to certify the subject's posture (or activity), the average of the two or more calibrations (such as SU, SE, ST) is used. This measurement is noted with a code in the matrix array and report printout indicating that an average of the calibrations was used. Not including the calibration period or potential repeats due to error codes, the device can store up to 288 measurements in a 24-hr period or 576 measurements in a 48-hr period (assuming measurements taken every 5 minutes). Data in a matrix array with these variables in the following columns: (1) time (hr:rnin), (2) measurementnumber (1-6 calibration, >7 field testing), (3) posture/calibration sensitivity setting (code: I=SU, 2=SE, 3=ST, or 4=Average Calibration/X), (4) systolic blood pressure (SBP, mm Hg, pressure corresponding to first K-sound detected by microphone), (5) diastolic blood pressure (DBP, mm Hg, pressure corresponding to last K-sound), (6) estimated mean arterial blood pressure (MAPest = 1/3 (SBP-DBP) + DBP), (7) estimated pulse pressure (PP = SBP - DBP), (8) heart rate (bpm) as determined by average time elapsed in seconds between EKG R-waves during which the corresponding Korotkoff sounds are assessed, divided into 60, (9) EKG regularity/irregularity codes including those which note excessive noise (code 0), and double-peaked R-waves (code 1) or large T- waves (code 2) which can arbitrarily double the heart rate (other codes for column #9, codes 3-10 TBA), and (10) machine error codes or repeat measurements due to errors detected (* for average sensitivity setting, and #s 1-10 for unique measurement or error report). If an average postural calibration is used or errors are detected, then a repeat measurement is taken, for example after 1 minute has transpired. This measurement is noted as a repeat measurement in the record's column 10 of the matrix array.

Following a recording period, an abbreviated version of each individual data record can be displayed on the monitor (time, measurement #, SBP, DBP, HR, Error codes). Alternatively, the monitor is connected to a computer and/or an ABP device report printer by way of an interface and field data is downloaded, individual data points are plotted, 24-hour or 48-hour averages are calculated, and the subject's data is classified via a special software package. Classifications range from normotension to Stages IV hypertension based on National Heart Lung and Blood Institute Guidelines.

Example 5 Method of ABP Device Measurement and Manual Correction This example describes a particular example that can be used to perform the manual ABP device method. However, one skilled in the art will appreciate that variations can be made to the method.

Blood pressure measurements are obtained from the subject using both an ABP device and a reliable cross-checking procedure two times for each posture position. For example, blood pressure measurements are obtained (for example simultaneously) from the subject using both the ABP device (such as the Accutracker) and a reliable cross-checking procedure when the subject is first supine, then seated, then standing, hi particular examples the subject has been in the position for at least five minutes prior to obtaining the blood pressure measurement. The blood pressure measurements for both readings are averaged for each position and for each type of measurement (ABP or cross-checking method). For example, if the subject is supine, and the two ABP readings were 110/70 and 112/80 (for an average of 111/75) and the blood pressure reading using the cross-checking method were 124/100 and 120/90 (for an average of 122/95), the posture correction factor for supine would be +11 for systolic and +20 for diastolic. Similar methods can be used to determine the correction factor for any desired position. These posture correction factors can be stored, for example in a cpu. The subject is subjected to blood pressure monitoring over a desired time period, for example using the same ABP device used to determine the posture correction factors. For example, blood pressure can be monitored over a 24 hour period, with blood pressure measurements obtained at least once per hour (such as every 15 minutes while awake, and every 30 minutes while sleeping). Just after the blood pressure measurement is taken, the subject records their body position and a correlator to the measurement on a log. For example if the subject is seated, the subject records in the log that they were seated and the time the measurement was taken. Time can be recorded as actual time (such as 12:00 pm), or as relative time (such as time point 5), or as another arbitrary marker which correlates to the stored measurement.

The blood pressure measurements obtained from the ABP device over the time period are corrected based on the posture correction factors. For example, the blood pressure measurements are coded as to the body position at the time of the measurement. The corrected blood pressure measurements are determined from the imputed posture correction factors, log information, and actual blood pressure measurement obtained. For example, if the correction factors for supine are +11 for systolic and +20 for diastolic (as described above) and the blood pressure readings at time 5, 24, and 50 are 100/90, 90/85, and 120/80, and the subject was supine at those times, the corrected blood pressure would be 111/110, 101/105, and 131/100. Similar methods can be used to determine the blood pressure for other body positions using other correction factors (such as activity correction factors).

Example 6 Method of ABP Device Measurement and Automated Correction

This example describes a particular example that can be used to perform the automated ABP device method. However, one skilled in the art will appreciate that variations can be made to the method.

Blood pressure measurements are obtained from the subject using both the ABP device and a reliable cross-checking procedure two times for each posture position. For example, blood pressure measurements are obtained (for example simultaneously) from the subject using both the ABP device (such as the Accutracker) and a reliable cross-checking procedure when the subject is first supine, then seated, then standing. In particular examples the subject has been in the position for at least 5 minutes prior to obtaining the blood pressure measurement. The blood pressure measurements for both readings are averaged for each position and for each type of measurement (ABP or cross-checking method). For example, if the subject is supine, and the two ABP readings were 110/70 and 112/80 (for an average of 111/75) and the blood pressure reading using the cross-checking method were 114/78 and 112/82 (for an average of 113/80), the posture correction factor for supine would be +2 for systolic and +5 for diastolic. Similar methods can be used to determine the correction factor for any desired position. These posture correction factors can be stored, for example in a cpu.

The subject is subjected to blood pressure monitoring over a desired time period, for example using the same ABP device used to determine the posture correction factors. For example, blood pressure can be monitored over a 24 hour period, with blood pressure measurements obtained at least once per hour (such as every 15 minutes or every 30 minutes). Just after the blood pressure measurement is taken (for example within one minute), the position detector located on the subject (such as an accelerometer located on the arm or leg) determines the body position of the subject (such as SE, SU₅ or ST). Information on the measured blood pressure and the detected body position are transferred to a calculator device, such as the memory or cpu of such a device. The blood pressure measurements obtained from the ABP device over the time period are corrected by the calculator device based on the posture correction factors, actual blood pressure measurement obtained, and the detected postures. For example, the blood pressure measurements are coded as to the body position at the time of the measurement, and the calculator device selects the appropriate correction factor based on the reported body position and the blood pressure reading to be corrected (such as the systolic or diastolic BP, or the mean arterial pressure). For example, if the correction factors for supine are +2 for systolic and +5 for diastolic (as described above) and the blood pressure readings at time 5, 24, and 50 are

100/90, 90/85, and 120/80, and the subject was supine at those times, the corrected blood pressure calculated by the calculator device would be 102/95, 92/90, and 122/85, and this information could be outputted for further analysis. This correction can be made in real time, or can be performed at a later time. Similar methods can be used to determine the blood pressure for other body positions using other correction factors (such as activity correction factors).

Example 7 Auscultatory ABP Device Measurement and Adjusting Sensor Sensitivity

This example describes a particular example that can be used to measure blood pressure using an auscultatory ABP device wherein the auscultatory sensor sensitivity is adjusted prior to taking the measurement. However, one skilled in the art will appreciate that variations can be made to the method.

Blood pressure measurements are obtained from the subject using an auscultatory ABP device two times for each posture position. For example, blood pressure measurements are obtained from the subject using an auscultatory ABP device (such as the Accutracker) when the subject is first supine, then seated, then standing. In particular examples the subject has been in the position for at least 5 minutes prior to obtaining the blood pressure measurement.

The blood pressure measurements are used to determine a sensor sensitivity setting for each body position (wherein both readings for each position are averaged). For example, if at sensor sensitivity setting 5 the K-sound amplitude is above or below the limits for sensor sensitivity setting 5, the sensor sensitivity can be increased or decreased. For example, if the subject is standing and the auscultatory ABP device detects a K-sound that is above the sensor sensitivity for setting 5, the sensor sensitivity can be decreased, for example by at least 2-fold (such as at least 5-fold, at least 10-fold, or at least 100-fold). This would result in a sensor sensitivity for the ST position of, for example -2 fold (and necessitate, for example, a switch to a different sensor setting, such as setting 3). Similarly, if the standing is seated and the auscultatory ABP device detects a K-sound that is below the sensor sensitivity for setting 5, the sensor sensitivity can be increased, for example by at least 2-fold (such as at least 5-fold, at least 10-fold, or at least 100- fold). This would result in a sensor sensitivity for the ST position of, for example +2 fold (and necessitate, for example, a switch to a different sensor setting, such as setting 7). The sensor sensitivity setting needed for each body position (or activity) can be stored, for example in a cpu.

The body position of the subject (such as SE, ST, or SU) is determined, for example at least 5 seconds (for example at least 10 seconds, such as 5, 10, 20 or 30 seconds) before each blood pressure measurement, for example by detecting a measurement from an accelerometer on the subject. If excessive motion or noise is detected (for example such that the particular body position cannot be determined), the average of the sensitivity for a plurality of postures or activities is used. Alternatively, if no excessive motion or noise is detected, and the activity or position can be determined, the specific sensitivity setting for that activity or position is used. The auscultatory sensor sensitivity is set accordingly, and the ABP device takes a blood pressure measurement. The resulting blood pressure is more accurate than if no adjustment were made to the auscultatory sensor prior to taking the measurement. Similar methods can be used to take into account the subject' activity prior to measuring the blood pressure (for example by determining and using activity sensor sensitivity settings).

The subject's blood pressure is measured with the auscultatory ABP device over a desired time period. For example, blood pressure can be monitored over a 24 hour period, with blood pressure measurements obtained at least once per hour (such as at least every 15 or 30 minutes). Information on the measured blood pressure and the detected body position are recorded, for example to permit analysis of the blood pressure measurements.

Example 8 Auscultatory/oscillometric ABP Device Measurement and Adjusting Sensor Sensitivity

This example describes a particular example that can be used to measure blood pressure using an auscultatory/oscillometric ABP device wherein the auscultatory and oscillometric sensor sensitivities are adjusted prior to taking the measurement. However, one skilled in the art will appreciate that variations can be made to the method. Blood pressure measurements are obtained from the subject using an auscultatory ABP device and an oscillometric ABP device (or a single device that includes both types of sensors) two times for each posture position. For example, blood pressure measurements are obtained from the subject using an auscultatory ABP device (such as the Accutracker) and using an oscillometric ABP device (such as the SpaceLabs 90202 or 90207 device) when the subject is first supine, then seated, then standing. In particular examples the subject has been in the position for at least 5 minutes prior to obtaining the blood pressure measurement.

The blood pressure measurements are used to determine an auscultatory and an oscillometric sensor sensitivity setting for each body position (wherein both readings for each position are averaged). For example, if at auscultatory sensor sensitivity setting 5 the K-sound amplitude is above or below the limits for auscultatory sensor sensitivity setting 5, the auscultatory sensor sensitivity can be increased or decreased. For example, if the subject is standing and the auscultatory ABP device indicates a K-sound that is above the sensor sensitivity for setting 5, the auscultatory sensor sensitivity can be decreased, for example by at least 2-fold (such as at least 5-fold, at least 10-fold, or at least 100-fold). This would result in a auscultatory sensor sensitivity for the ST position of, for example -2 fold (and necessitate, for example, a, switch to a different auscultatory sensor setting, such as setting 3). Similarly, if the standing is seated and the auscultatory ABP device detects a K-sound that is below the auscultatory sensor sensitivity for setting 5, the auscultatory sensor sensitivity can be increased, for example by at least 2-fold (such as at least 5-fold, at least 10-fold, or at least 100-fold). This would result in a auscultatory sensor sensitivity for the ST position of, for example +2 fold (and necessitate, for example, a switch to a different auscultatory sensor setting, such as setting 7).

Similarly, if at oscillometric sensor sensitivity setting 5 the pulse signal amplitude is above or below the limits for oscillometric sensor sensitivity setting 5, the oscillometric sensor sensitivity can be increased or decreased. For example, if the subject is standing and the oscillometric ABP device indicates a pulse signal that is above the oscillometric sensor sensitivity for setting 5, the oscillometric sensor sensitivity can be decreased, for example by at least 2-fold (such as at least 5-fold, at least 10-fold, or at least 100-fold). This would result in an oscillometry sensor sensitivity for the ST position of, for example -2 fold (and necessitate, for example, a switch to a different oscillometric sensor setting, such as setting 3). Similarly, if the standing is seated and the oscillometric ABP device indicates a pulse signal that is below the oscillometric sensor sensitivity for setting 5, the oscillometric sensor sensitivity can be increased, for example by at least 2-fold (such as at least 5-fold, at least 10-fold, or at least 100-fold). This would result in an oscillometric sensor sensitivity for the ST position of, for example +2 fold (and necessitate, for example, a switch to a different oscillometric sensor setting, such as setting 7). The auscultatory and oscillometric sensor sensitivity settings for each body position (or activity) can be stored, for example in a cpu. The body position of the subject (such as SE, ST, or SU) is determined, for example at least 5 seconds (for example at least 10 seconds, such as 5, 10, 20 or 30 seconds) before each blood pressure measurement, for example by detecting a measurement from an accelerometer on the subject. If excessive motion or noise is detected (for example such that the particular body position cannot be determined), the average of the sensitivity for a plurality of postures or activities is used (such as the average of oscillometric and auscultatory sensor sensitivities). Alternatively, if no excessive motion or noise is detected, and the activity or position can be determined, the specific oscillometric and auscultatory sensitivity setting for that activity or position is used. The oscillometric and auscultatory sensor sensitivities are set accordingly, and the ABP device takes a blood pressure measurement.

Similar methods can be used to take into account the subject' activity prior to measuring the blood pressure (for example by determining and using activity sensor sensitivity settings).

The subject's blood pressure is measured with the auscultatory and oscillometric ABP device over a desired time period. For example, blood pressure can be monitored over a 24 hour period, with blood pressure measurements obtained at least once per hour (such as every 15 or 30 minutes). Information on the measured blood pressure and the detected body position are recorded, for example to permit analysis of the blood pressure measurements Example 9 Blood Pressure Cuff with Oscillometric and Auscultatory Sensors

This example describes an exemplary blood pressure cuff that can be used in the methods disclosed herein (for example that shown in FIG. 17), and can be part of the devices disclosed herein (for example that shown in FIG. 16). One skilled in the art will appreciate that modifications can be made to the cuff, without affecting the ability of the cuff to function properly.

An exemplary blood pressure cuff is shown in FIG. 18. The shape of the cuff when placed on the limb (such as an arm) is conical. The cuff includes at least two sensors, such as an auscultatory sensor and an oscillometric sensor. In one example, the midpoint of the oscillometric sensor is near the top of the cuff (for example in the upper half, upper third, or upper quarter of the cuff), and the midpoint of the auscultatory sensor is near the bottom of the cuff (for example in the lower half, lower third, or lower quarter of the cuff). Auscultatory sensors are those that can detect K-sounds (such as a piezo-electric curved crystal microphone), and oscillometric sensors are those that can detect pressure, such as a pulse (such as a pressure transducer). The sensors are arcuate-shaped, and are at a location that permits that permits the sensor to traverse the desired artery, such as the brachial artery. The oscillometric sensor traverses the longitudinal axis medially. The arcuate auscultatory sensor is skewed transverse relative to the longitudinal axis of the cuff when the cuff is positioned on a subject's arm with the sensor carried by the cuff. The sensors are positioned such that their midpoints are directly over the desired artery (such as the brachial artery). The cuff also includes a rubber bladder, for example internal to the cuff, hi some examples, the cuff further includes guide strips (such as a colored guide strip, for example a neon guide strip), for example to assist in placement of the cuff on the subject. -

Example 10

Auscultatory-Oscillometric-postural adjusting Ambulatory Blood Pressure Device

This example describes an exemplary ABP device that uses both auscultatory and oscillometric sensor that can be used in the methods disclosed herein (for example that shown in FIG. 17), and is a specific exemplary devices disclosed herein (for example that shown in FIG. 16). One skilled in the art will appreciate that modifications can be made to the device, without affecting the ability of the cuff to function device. For example, although particular dimensions are shown, one skilled in the art will appreciate that the device can be scaled up on down.

An exemplary auscultatory/oscillometric blood pressure device is shown in FIG. 19. The device shown in FIG. 19 includes a PC board with microprocessor/microcomputer, a pump, a battery (such as a rechargeable battery), position or activity sensors (such as one or more inclinometers/tilt sensors/electronic postural sensors/accelerometers), acoustic/auscultatory sensors, pressure/oscillometric sensors, a blood pressure cuff (such as the one shown in FIG. 18), and interface electronics and tubing for interconnections. In particular examples, the device also includes a data entry device (such as a touchpad), an LCD display, or both. For example, the data entry device can be used to enter sensor sensitivities for particular body postures or activities.

Exemplary pumps that can be used include a piezo-electric pump, a CO2 gas canister (such as those available from Colin Medical Instruments/Omron, Bannockburn, IL), and a conventional diaphragm pump (such as the Cylindrical Instrument Pump, Gillian Instruments, Wayne, NJ). For example, a piezoelectric pump or a CO₂-gas canister/cartridge pump can be used to reduce one or more of weight, power consumption, and noise.

In particular examples, the one or more batteries are rechargeable or are a rechargeable battery pack(s). The one or more posture or activity detectors can include two inclinometers/electronic postural sensors, for example to permit distinguishing between supine and seated postures.

In a particular example, the bottom of the monitor box component of the device (such as one having a 7.7 x 2.75 cm horizontal face) can include a plurality of USB ports for input/output (such as at least two USB ports or at least three USB ports). The device can include one or more electronic interface cables between the auscultatory (A) sensor and the monitor and between the oscillometric (O) sensor and the monitor. In a specific example, the electronic interface cable between the auscultatory sensor and the monitor box is at least 47 cm and the interface cable between the oscillometric sensor and the monitor box is at least 32 cm. The electronic interface cables can be interconnected by small (such as 1.5 cm diameter) synch rings (for example at the top of the blood pressure cuff and near the monitor box housing) to prevent pull out/detachment during field testing of the test subject. The oscillometric sensor can be housed within the cuff (for example as- shown in FIG. 18) or more remotely from the cuff within the monitor box, since pressure in the cuff can be detected at any point in the closed cuff-tube system. In one example, dual oscillometric sensors (such as one in the cuff and one near the pump) are used to detect pressure differences between the cuff and the pump (for example to detect system leaks and prompt an error message).

A pressure tube can be used to connect the cuff to the pump. This length of the tube can allow the monitor to be attached to the subject's waist (for example with a belt) and to allow the pressure tube to traverse unencumbered from the monitor over the subject's shoulder and arm to the blood pressure cuff. In on example the pressure tube is approximately 60 cm. In a particular example, the pressure tube absolute diameter is 7 mm, with an internal bore diameter of 4 mm.

In particular examples, the weight for the portion of the monitor that includes the PC board, pump, and battery pack) is no more than 500 g, such as no more than 400 g, for example no more than 376 g (13.3 oz) (such as 300-400 g).

In particular examples, the LCD display is inverted from anterior view, for example so the person calibrating the device (such as a laboratory technician or a clinician) can view the LCD display during baseline calibration and subjects can view it during testing. The device can include an option for blocking column display output, for example so that subject's view only Time, Measurement #, Posture, and EC/Error Codes for 1 minute. after each field test measurement.

The cuff can be worn on the subject's non-dominant arm, for example to facilitate activities of daily living, to minimize motion artifact, and to maintain consistency for inter-patient/population comparisons. For each measurement, initial pressure inflation is the cue for the subject to relax the arm at the side (with elbow fully extended) so that noise is reduced when a measurement is taken. In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only examples of and should not be taken as limiting the scope of the invention. The claims set forth below are directed toward novel and non- obvious combinations and sub-combinations of elements and method acts and there is no requirement that the claims contain other elements or method acts not set forth therein. We claim as our invention all that comes within the scope and spirit of these claims.

Claims

We claim:

1. A blood pressure monitoring apparatus, comprising: at least one means for detecting a position of the subject; and at least one means for detecting a representation of blood pressure of a subject.

2. The blood pressure monitoring apparatus of claim 1, wherein the apparatus further comprises a means for storing and reporting blood pressure measurements.

3. The blood pressure monitoring apparatus of claim 1, wherein the apparatus further comprises a means for storing and reporting one or more correction factors or one or more sensor sensitivities.

4. The blood pressure monitoring apparatus of claim 1 or 2, wherein the means for storing and reporting one or more correction factors or one or more sensor sensitivities and the means for storing and reporting blood pressure measurements comprise a microcomputer.

5. The blood pressure monitoring apparatus of claim 1 , wherein the apparatus further comprises at least one means for adjusting a blood pressure sensor depending on the subject's position or activity.

6. The apparatus of claim 5, wherein the means for detecting the subject's position comprises at least one inclinometer or accelerometer.

7. The apparatus of claim 6, wherein the means for detecting the subject's activity comprises at least one pedometer.

8. The blood pressure monitoring apparatus of claim 1, wherein the apparatus further comprises a means for entering one or more correction factors or one or more sensor sensitivities.

9. The apparatus of claim 1, wherein the blood pressure sensor comprises one or more auscultatory sensors or one or more oscillometric sensors.

10. The apparatus of claim 9, wherein the auscultatory sensors comprise one or more piezo-electric crystal microphones.

11. The apparatus of claim 1, wherein the apparatus further comprises a blood pressure cuff.

12. The apparatus of claim 11, wherein the blood pressure cuff includes one or more auscultatory sensors or one or more oscillometric sensors.

13. The apparatus of claim 1, wherein the means for detecting a representation of blood pressure of a subject comprising an ambulatory blood pressure monitor.

14. A blood pressure monitoring apparatus, comprising: at least one means for detecting a representation of blood pressure of a subject; at least one means for detecting a position of the subject; and at least one means for adjusting the representation of blood pressure depending on the position of the subject.

15. The apparatus of claim 14, wherein there are two means for detecting a representation of blood pressure of a subject.

16. A blood pressure monitoring apparatus, comprising: at least one posture detector for sensing the body position of a subject and operable to produce at least one body position indicating output signal; at least one blood pressure monitor sensor adjustor operable to receive the at least one body position indicating output signal and to calibrate a blood pressure sensor depending on the at least one body position indicating output signal; and at least one blood pressure sensor operable to produce at least one sensed blood pressure output signal corresponding to sensed blood pressure in a subject, wherein the sensed blood pressure output signal more accurately represents the subject's actual blood pressure condition than in the absence of calibration.

17. The apparatus of claim 16, wherein the blood pressure monitor sensor comprises one or more auscultatory or oscillometric sensors.

18. A blood pressure monitoring apparatus, comprising: at least one blood pressure monitor operable to produce at least one sensed blood pressure output signal corresponding to sensed blood pressure in a subject; at least one body position sensor for sensing the body position of the subject and operable to produce at least one body position indicating output signal; at least one blood pressure correlator operable to receive the at least one sensed blood pressure output signal and the at least one body position indicating output signal, the blood pressure correlator providing a second blood pressure output signal corresponding to the at least one sensed blood pressure output signal that has been modified to compensate for the effect of body positions on the sensed blood pressure output signal such that the second blood pressure output signal more accurately represents the subject's actual blood pressure condition than the at least one sensed blood pressure output signal.

19. A method of determining blood pressure of a subject, comprising: measuring a signal from one or more posture detectors on the subject, thereby generating a posture signal; adjusting a sensitivity of one or more blood pressure device sensors based on the posture signal; and measuring a signal from one or more blood pressure devices associated with the sensors, wherein the signal correlates with the blood pressure of the subject.

20. The method of claim 19, further comprising: calibrating the blood pressure device for at least three body positions prior to measuring the posture signal.

21. A method of determining blood pressure of a subject, comprising: measuring a signal from a blood pressure device on the subject; measuring a signal from a posture detector on the subject; and correlating the signal from the blood pressure device and the positional device, thereby generating a correlated signal, wherein the correlated signal provides a blood pressure of the subject.

22. The method of claim 21, wherein the blood pressure device and the positional device are located on different parts of the subject.

23. The method of claim 22, wherein the blood pressure of the subject provided by the correlated signal is more accurate than a blood pressure determined using the blood pressure device.

24. A method of determining blood pressure of a subject, comprising: measuring a signal from a first blood pressure device on the subject; measuring a signal from a second blood pressure device on the subject; and correlating the signal from the first and second blood pressure devices, thereby generating a correlated signal, wherein the correlated signal more accurately represents the subject's actual blood pressure condition than either signal from the first or second blood pressure device.

25. The method of claim 24, wherein measuring the signals from- the first and second blood pressure devices is simultaneous.

26. The method of claim 24, wherein the first and second blood pressure devices are present on one arm of the subject.

27. The method of claim 19, 21, or 24 wherein the subject is a human or veterinary subject.

28. A blood pressure cuff comprising: a first and a second blood pressure sensor, wherein the first sensor comprises an auscultatory sensor and the second sensor comprises an oscillometric sensor.

29. The blood pressure cuff of claim 28, wherein the auscultatory sensor is near a bottom portion of the cuff and the oscillometric sensor is near a top portion of the cuff.

30. The blood pressure cuff of claim 28, wherein the first and second sensors are arcuate-shaped.

31. The blood pressure cuff of claim 28, wherein the auscultatory sensor is skewed transverse relative to a longitudinal axis of the cuff when the cuff is positioned on a subject's arm with the auscultatory sensor carried by the cuff.

32. The blood pressure cuff of claim 28, wherein the sensors are positioned on or within the cuff such that a midpoint of the first sensor and a midpoint of the second sensor will be directly over an artery when the cuff is appropriately placed on a subject.

33. The blood pressure cuff of claim 28, wherein the cuff further includes a bladder.

34. The blood pressure cuff of claim 28, wherein the cuff further includes one or more guide strips to assist in placement of the cuff on a subject.

35. The blood pressure cuff of claim 28, wherein the cuff is conical in shape when appropriately attached to a subject's limb.