WO2015157649A1

WO2015157649A1 - Devices and methods for continuous blood pressure montoring

Info

Publication number: WO2015157649A1
Application number: PCT/US2015/025333
Authority: WO
Inventors: Michael Sand; David JORGENSON
Original assignee: Michael Sand; Jorgenson David
Priority date: 2014-04-10
Filing date: 2015-04-10
Publication date: 2015-10-15

Abstract

A blood pressure monitoring device includes at least one force sensor configured to detect an arterial force, a positioning device coupled to the at least one force sensor, and a computing device in communication with one or both of the positioning device and the at least one force sensor. The positioning device is configured to apply a continuous static force to the at least one force sensor in order to position the at least one sensor over or near an artery of a patient. The computing device is configured to receive a signal containing a measurement from the at least one force sensor. In some examples, the device may include three force sensor matrices positioned along an artery of a patient and an actuator coupled to a middle one of the force sensors configured to apply a force to the middle force sensor sufficient to occlude the artery.

Description

DEVICES AND METHODS FOR CONTINUOUS BLOOD PRESSURE

MONITORING

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 61/978,174 filed April 10, 2014, which is hereby incorporated by reference in its entirety.

BACKGROUND

[0002] The challenges of cardiovascular disease and high blood pressure (hypertension) are well known by medical professionals and the general public. Around 31% of American adults have high blood pressure. High blood pressure costs the US $47.5 billion annually in direct medical expenses and $3.5 billion each year in lost productivity. Approximately 26% of the world's adult population has hypertension, 80 million in the U.S. alone and blood pressure is implicated in heart attacks, strokes, and chronic heart failure. The standard of care for blood pressure measurement is an inflation cuff device and the physician refines the blood pressure medication through periodic clinic visits. Blood pressure is known to vary day and night which is not captured using present methods. In addition, blood pressure measurement errors are due to both technique and "white-coat syndrome". It is estimated that a 5 mmHg error (roughly a 5% error) in blood pressure measurement costs $1 ,000 annually per patient. High blood pressure is a major clinical concern with significant economic impact.

[0003] Accordingly, the accurate measurement of blood pressure is of vital importance. Blood pressure measurements are traditionally taken in a doctor's office using an inflation cuff device and are typically recorded at a single point in time, two to four times per year. However, measurements obtained in this fashion may not be reliable for a host of reasons including variation in measurement methods, or factors that may affect a patient's blood pressure at the time of measurement, such as the anxiety that some patients feel from being in a doctor's office or at having a clinical procedure performed. Further, the traditional practice of obtaining an isolated measurement does not allow for a doctor to appreciate the variations in a patient's blood pressure which may occur throughout the day, over extended periods of time, or in response to certain events.

[0004] Studies have confirmed blood pressure measured over a 24-hour period is superior to a single clinic blood pressure measurement in predicting future cardio vascular events and target organ damage. However, two major challenges have emerged with 24-hour blood pressure measurement techniques; 1) patient compliance is highly variable because inflation cuffs can be intrusive and especially interrupt sleep with repeated inflations and deflations each hour. The patient's behavior may change when alerted by the inflation and, for some, the inflation itself causes an alteration in blood pressure and 2) interpretation of 24 to 48-hour blood pressure measurements by physicians to draw clinically actionable conclusions from these data is more challenging. As of today, 24-hour blood pressure monitoring is not common in clinical practice but can be found in research studies or an occasional hypertension clinic. Thus, there is a considerable opportunity to fill an unmet clinical need for a cuff-less noninvasive blood pressure (NIBP) measurement device that (1) improves patient 24-hour compliance and (2) produces clinically-actionable metrics that improves hypertension treatment. Therefore, a new clinical approach is proposed— a Non-Invasive Self- calibrating Ambulatory Multi-Modality (NISAM) device to collect calibrated blood pressure addressing patient 24-hour compliance issues and improving long-term hypertension treatment.

[0005] The blood pressure monitoring devices and methods disclosed herein aim to address these disadvantages. For example, the present device is beneficially untethered from wall-mounted or other cumbersome equipment and may be worn under a user's clothing permitting a user to engage in normal daily activities while blood pressure measurements are taken and recorded. In addition, the device is passive in operation due to a continuous static force applied by a positioning device that couples the blood pressure monitoring device to a patient, whereas known blood pressure cuffs must actively inflate in order to take a blood pressure reading. This inflation may be annoying or distracting to a user and others around them, especially if the blood pressure is being monitored in regular intervals like every minute, every five minutes, or every ten minutes, for example.

[0006] In operation, the continuous blood pressure monitoring device may provide a doctor with a patient's blood pressure profile over an extended period of time, for instance, throughout the course of an entire day, week, or month, rather than being forced to rely on isolated blood pressure measurements in an office setting or physically recorded by the patient. This additional information may allow the doctor to make a more complete and accurate assessment of a patient's health, and may allow the doctor to tailor a more effective treatment for a patient's symptoms, such as high blood pressure. More complete blood pressure data may also be correlated with other measureable health metrics such as pulse rate, respiratory rate, sleep patterns, blood sugar levels, and more to offer further insights into a patient's health and a provide a basis for determining improved healthcare treatments.

DEFINITIONS

[0007] As described herein, a "positioning device" means anything that may couple the at least one force sensor to a location on a patient's body, for example, an arm. The positioning device may take the form of an elastic band, a strap, a belt, a wrapping, or adhesive tabs, among other possibilities. The positioning device may further include a locking mechanism, such as a clasp, a buckle, hook and loop material, or any other similar material or structure sufficient to couple the force sensor to the patient's body. In addition, the positioning device may be portable and untethered from cumbersome monitoring equipment or air pressure inducing equipment such that the positioning device may be worn under clothing, which permits the patient to engage in normal daily activities while wearing the blood pressure monitoring device.

[0008] As used herein, a "continuous static force" refers to a constant force or pressure maintained by the positioning device when worn by a patient. This continuous static force is different from inflatable cuffs known in the art, which inflate and deflate during operation. In some embodiments, the positioning device may be configured to be placed under tension when worn by a user, such that a continuous static force is applied to the force sensor to position the force sensor over or near an artery of a patient and to maintain contact between a patient's skin and the force sensor.

[0009] As used herein, "arterial force" refers to the pressure exerted against an artery wall due to blood flow or pressure therein. A standard blood pressure measurement is represented as a systolic pressure over diastolic pressure. The systolic pressure represents the maximum arterial pressure exerted during contraction of the left ventricle of the heart. The diastolic pressure represents the minimum arterial pressure exerted, which occurs during the interval between heart beats.

[0010] As used herein, "health sensor" refers to any sensor for measuring one or more physiological parameters that may be indicative of one or more health attributes, such as, blood pressure, pulse rate, respiratory rate, blood sugar level, sleep patterns, skin temperature, or similar attributes. In a non-exhaustive list, the health sensor may include any one of an optical (e.g., CMOS, CCD, photodiode), acoustic (e.g., piezoelectric, piezoceramic), electrochemical (voltage, impedance), thermal, mechanical (e.g., pressure, strain), magnetic, or electromagnetic (e.g., magnetic resonance) sensor.

SUMMARY

[0011] Methods, computer readable mediums, and devices are described herein for monitoring a patient's blood pressure using a wearable untethered blood pressure monitoring device.

[0012] Some embodiments of the present disclosure provide a device, comprising: (1) at least one force sensor having a bottom surface configured to detect an arterial force; (2) a positioning device coupled to the at least one force sensor, wherein the positioning device is configured to apply a continuous static force to the at least one force sensor in order to position the at least one sensor over or near an artery of a patient and to maintain contact between a patient's skin and the bottom surface of the at least one force sensor, wherein the positioning device is untethered and portable; and (3) a computing device in communication with one or both of the positioning device and the at least one force sensor, wherein the computing device is configured to receive a signal containing a measurement from the at least one force sensor.

[0013] Further embodiments of the present disclosure provide a method for monitoring blood pressure comprising: (1) receiving, by a computing device, at least one pressure signal at each time in a series of regular times during a monitoring period, wherein the at least one pressure signal is detected by at least one force sensor coupled to a positioning device, wherein the positioning device is configured to position the at least one force sensor over or near an artery of a patient and to maintain contact between a patient's skin and the at least one force sensor; (2) determining, by the computing device, a value for the at least one pressure signal at each time, wherein the value corresponds to a systolic or a diastolic blood pressure; and (3) storing, by the computing device, the value of the at least one pressure signal at each time and a corresponding time in a memory unit.

[0014] Still further embodiments of the present disclosure provide a non-transitory computer readable medium having stored therein instructions executable by a computing device to cause the computing device to perform functions comprising: (1) receiving, by a computing device, at least one pressure signal at each time in a series of regular times during a monitoring period, wherein the at least one pressure signal is detected by at least one force sensor coupled to a positioning device, wherein the positioning device is configured to position the at least one force sensor over or near an artery of a patient and to maintain contact between a patient's skin and the at least one force sensor; (2) determining, by the computing device, a value for each pressure signal, wherein the value corresponds to a systolic or a diastolic blood pressure; and (3) storing, by the computing device, the value of each pressure signal and a corresponding time in a memory unit.

[0015] Some embodiments of the present disclosure also provide a device, comprising: (1) a housing having a first end and a second end; (2) an actuator coupled to the housing between the first end and the second end of the housing; (3) a first force sensor matrix coupled to the housing between the first end of the housing and the actuator; (4) a second force sensor matrix coupled to one or more of the housing and the actuator; and (5) a third force sensor matrix coupled to the housing between the actuator and the second end of the housing.

[0016] Further embodiments of the present disclosure provide a method, comprising: (1) providing a device for blood pressure monitoring; (2) coupling the housing to a patient and aligning each of the first, second and third force sensor matrix with an artery such that the first force sensor matrix is arranged upstream from the third force sensor matrix; (3) applying a force to the second force sensor matrix, via the actuator, until the artery is occluded; (4) determining a first systolic blood pressure via the microprocessor; (5) reducing the force applied to the second force sensor matrix until the third force sensor matrix detects blood flow; (6) reapplying the force to the second force sensor matrix, via the actuator, until occlusion occurs; and (7) determining a second systolic blood pressure reading.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1A is a schematic illustration of an example blood pressure monitoring device.

[0018] Figure IB is a schematic illustration of an example blood pressure monitoring device.

[0019] Figure 2A illustrates an example blood pressure monitoring device having a single force sensor mounted on a human arm.

[0020] Figure 2B illustrates an example waveform measured from the blood pressure monitoring device of Figure 2A. [0021] Figure 3 illustrates measurement results from a blood pressure monitoring device having a single force sensor.

[0022] Figure 4 is a schematic illustration of an example blood pressure monitoring device.

[0023] Figure 5 illustrates an example blood pressure monitoring device positioned on a human arm and waveforms detected therefrom.

[0024] Figure 6A illustrates the measured applanation, upstream pressure and upstream force detected by the example blood pressure monitoring device of Figure 4.

[0025] Figure 6B illustrates measured downstream pressure and force prior, during and after applanation detected by the example blood pressure monitoring device of Figure 4.

[0026] Figure 6C illustrates measured tonometry detected by the example blood pressure monitoring device of Figure 4.

[0027] Figure 6D illustrates measured pulse-wave velocity detected by the example blood pressure monitoring device of Figure 4.

DETAILED DESCRIPTION

[0028] Hypertension has been diagnosed in 26% of the world's adult population and studies have shown 24-hour blood pressure measurements are superior to single clinic blood pressure measurements in predicting future hypertension-related cardiovascular events and target organ damage. Despite the significant advantage of 24- hour blood pressure measurements, they are not used in routine clinical practice because of low patient compliance and the challenge of interpreting the 24-hour blood pressure data by clinicians. Patient compliance is low because repeated inflation cuff measurements are disruptive. However, patient compliance could be improved by developing a 24-hour NIBP device that does not use an inflation cuff. Furthermore, if the device could be used at home by the patient, 24-hour blood pressure measurements could be obtained that are devoid of white-coat syndrome and give the physician a clearer indication of the patient's typical blood pressure variation throughout the day, thereby representing a new clinical approach to the treatment of hypertension.

[0029] Methods, computer readable mediums, and devices are described herein for continuously monitoring a patient's blood pressure using a wearable untethered blood pressure monitoring device. By positioning a force sensor over a patient's artery and keeping the sensor in place for a desired monitoring period, multiple pressure measurements may be taken. The device may measure a patient's blood pressure numerous times at regular intervals during the monitoring period. For example, blood pressure may be measured continuously, several times per minute, once a minute, every five minutes, every ten minutes, every 30 minutes, or every hour, among other possibilities, in the course of a monitoring period. The monitoring period itself may extend from an hour, a day, a week and a month, among other possibilities. The device of the present invention may permit the patient may engage in normal daily activities during the monitoring period to provide a more accurate data set of the patient's blood pressure.

[0030] Turning to Figure 1A, an example blood pressure monitoring device 100 is shown. The device 100 may include a positioning device 102, such as an arm band, with at least one force sensor 110 mounted thereon. The positioning device 102 is configured to apply a continuous static force to the at least one force sensor 110 in order to position the at least one force sensor 110 over or near an artery, such as at the upper arm, elbow or wrist of a patient. In some examples, the continuous static force applied by the positioning device to the at least one force sensor may range from about 0 to about 8 pounds. Further, the positioning device 102 is configured to maintain contact between the patient's skin and a bottom surface of the at least one force sensor 110. The positioning device 102 and/or the at least one force sensor 110 may, in some examples, be flexible or rigid or have properties that range between flexible and rigid. In some embodiments, the device 100 may also include a computing device 120 configured to receive pressure signals detected by the at least one force sensor 110 coupled to a positioning device 102. The computing device 120 may be coupled to the positioning device 102 and/or the at least one force sensor 110.

[0031] The at least one force sensor 110 may include any sensor configured to detect a force applied thereto. For example, at least one force sensor 110 may include a piezoresistive force sensor, a capacitive force sensor, an electromagnetic force sensor, a piezoelectric force sensor, an optical force sensor, a potentiometric force sensor, a resonant force sensor, a thermal force sensor or an ionization force sensor. In some examples, the at least one force sensor 110 may include two or more types of force sensors. The surface of the one or more sensors 110 in contact with the body of the patient may be capable of detecting an arterial force ranging from about 0 pounds to about 8 pounds.

[0032] The positioning device 102 and, therefore, the blood pressure monitoring device 100, may be operated without being connected to any stationary device, such as by a mechanical or electrical connection. By providing a positioning device 102 that is untethered, the blood pressure monitoring device 100 may be portable, allowing the patient's blood pressure to be measured while the patient engages in normal daily activities and without the need to come to a fixed location to use a traditional inflation-cuff device.

[0033] A processor 122 of the computing device 120 may determine values for the pressure signals that are equal to a patient's systolic and diastolic blood pressures. Processor 122 may be a general-purpose processor or a special purpose processor (e.g., digital signal processors, application specific integrated circuits, etc.). The processor 122 can be configured to execute computer-readable program instructions 126 that are stored in the memory unit 124 and are executable to provide the functionality of the blood pressure monitoring device 100 described herein. The systolic and diastolic blood pressure values, in addition to the corresponding times at which the pressure signals were detected, may be stored in the memory unit 124, such as a computer readable medium, that may be read or accessed by the processor 122. Storage of the times may include the date and specific time of day. The memory unit 124 can include volatile and/or non- volatile storage components, such as optical, magnetic, organic or other memory or disc storage, which can be integrated in whole or in part with at least one of the one or more processors 122. In some embodiments, the memory unit 124 can be implemented using a single physical device (e.g., one optical, magnetic, organic or other memory or disc storage unit), while in other embodiments, the memory unit 124 can be implemented using two or more physical devices.

[0034] A patient's movements during a monitoring period may occasionally disrupt the at least one force sensor 110, leading to potentially inaccurate or misleading measurements. Accordingly, in some embodiments, the computing device 120 may receive motion data from one or more motion sensors 130 such as an accelerometer, gyroscope, or other motion sensor. The computing device 120 may then determine a value for the motion. If the value exceeds a threshold stored in the memory unit 124, the computing device 120 may take a number of different actions. For instance, the computing device 120 may store an error message, an indication that the threshold was exceeded, or a value of zero in conjunction with the corresponding time in the memory unit 124. Alternatively, the computing device 120 may store no value or no data at all if the threshold is exceeded. The threshold may be a default, or it may be set manually. For example, the computing device 120 may receive motion data from an accelerometer located in the blood pressure monitoring device 100 positioned on a patient's wrist. The computing device 120 may determine that the motion data indicates an acceleration of lg of the patient's arm. If this value exceeds the stored threshold, the computing device 120 may take any of the actions noted above. When the motion sensor 130 indicates that the value is below the threshold, blood pressure measurements and recording of values and times may resume as normal.

[0035] In some embodiments, the blood pressure monitoring device 100 may also include one or more activity sensors 132, such as a pedometer, an accelerometer, a GPS, a pulse monitor, a respiratory monitor, or other similar devices. The computing device 120 may receive an activity signal, which may include activity data, from the one or more activity sensors 132 and process the activity data to identify what type of activity the patient is engaged in at a corresponding time, such as walking, running, or sleeping. The activity data may further include quantitative values for the activity; for instance, it may indicate the rate at which the patient is running or breathing. The computing device 120 may store the type of activity, the activity data, and the corresponding time in the memory unit 124.

[0036] The computing device 120 may also receive a health signal from one or more health sensors 134. The health signal may include health data, and the computing device 120 may use the health data to identify health attributes such as pulse rate, respiratory rate, blood sugar level, sleep patterns, or other similar data. The health data may further include a value for one or more health attributes at a given time. The computing device 120 may store the health attribute, the health data, and the corresponding times in the memory unit 124.

[0037] In some embodiments, the computing device 120 may analyze the stored data. For instance, a thirty-day blood pressure average may be determined. The device may also correlate various portions of the data to determine patterns. For instance, the time of day corresponding to highest and lowest blood pressure, or relative increases and decreases in blood pressure, may be determined. It may also be determined whether changes in blood pressure are correlated to certain activities, or to certain values of or changes in the patient's other health attributes. Based, at least in part, on this information, a recommended blood pressure treatment plan may be determined for the patient. The blood pressure treatment plan may include instructions for the patient to make a change in activity, begin, change or adjust a medication-based treatment to control the patient's blood pressure, or seek immediate medical attention. The instructions may be provided to the patient directly via an indication from the device. The device may alternatively cause the instructions to be sent to the patient via email, text message, or any other similar format.

[0038] In addition to the collected data, the blood pressure treatment plan may be determined based on input from a physician, recognized standards of care in the medical field, or a combination of both. For example, the device 100 (or remote computing device 140) may transmit any of the blood pressure data either separately or simultaneously to a doctor via the communications link 128, who may review and analyse the data and provide recommendations. Additionally or alternatively, the computing device 120 or remote computing device 140 may have stored thereon, such as in memory unit 124, a set of recognized standards or guidelines against which the blood pressure data may be compared. These standards or guidelines may include thresholds for healthy, unhealthy or emergency blood pressure levels, each of which may be associated with generally-accepted medical recommendations for when the blood pressure data falls within a particular range. For example, one or more stored guidelines may indicate that an individual having systolic pressures of 120 to 139 and diastolic pressures of 80 to 89 may be at risk for hypertension. The one or more stored guidelines may associate these ranges of systolic and diastolic pressures with a recommendation that the individual engage in moderate physical activity to reduce blood pressure to normal levels. The recommendation may also provide specific examples of physical activity, such as thirty minutes a day of brisk walking.

[0039] The blood pressure treatment plan may be determined directly on the device itself, such as by the on-board computing device 120. Alternatively, in some embodiments, the blood pressure monitoring system may include a communications link 128 for sending raw data, the stored values and corresponding times, processed data, or correlations to a remote computing device 140. The remote computing device 140 may include any remote device or location, such as an email address, a phone number, a website, an online data repository, a smartphone, personal computing device or remote server. The communication may be either wired or wireless, using any number of technologies known in the art. If receiving raw collected data, the remote computing device 140 may perform the analysis and correlation of the collected data and determine the blood pressure treatment plan, including recommended instructions for treatment of the patient. The remote computing device 140 may also transmit the collected, processed and/or correlated data to a physician for consideration and receive feedback from a physician that may be used in determining the blood pressure treatment plan. The remote computing device 140 may transmit the instructions to the patient, for example, in the form of a message to the blood pressure monitoring device or patient's smart phone.

[0040] In some embodiments, the wearable blood pressure monitoring device 100 may require calibration. For example, the device 100 may detect pressures that are correlated, but not necessarily equal to the patient's actual systolic and diastolic blood pressures. In this case, the values determined by the device 100 may be calibrated using a more conventional, manual blood pressure measurement, allowing a doctor to determine a coefficient that may be used to translate the pressures detected by the system into the patient's actual systolic and diastolic pressures. The coefficient may vary from patient to patient depending on each patient's arterial elasticity, the artery that is monitored, the configuration of the monitoring device, and other factors.

[0041] In some embodiments, for example as shown in Figure IB, the one or more sensors 110 may comprise a plurality of sensors positioned over or near the patient's artery. The plurality of sensors may be arranged in an array 150 that may have a perimeter that is polygonal, rectangular, square or circular. The computing device may receive data from the array 150 of sensors, each sensor in the array 150 measuring the patient's arterial pressure. Some sensors in the array 150 may be positioned in a more optimal position to obtain a pressure measurement, and the system may determine which sensor in the array 150 is measuring the optimal pressure signal at any given time. The computing device may then record the value of the optimal pressure signal at a given time, and ignore as noise the pressure signals received from the other sensors in the array 150.

[0042] Further, because a patient may engage in normal activities throughout the course of a monitoring period, it is possible that the monitoring device may move slightly, thereby changing the position of the array of sensors with respect to the patient's artery. To compensate for this movement, the computing device may again determine which sensor in the array is measuring the optimal pressure signal at a given time, and store the value of the optimal signal. For any given pressure measurement, the optimal signal may be received from a different sensor in the array than one that was previously used.

[0043] Figure 2A illustrates an embodiment of a blood pressure monitoring device, such as device 100, utilizing a single force sensor located over the brachial artery pulse point in use on a human subject. The sensor was held in place using an arm band as a positioning device (Figure 2 A) and adjusted to yield a pulse signal (Figure 2B). The pressure waveform derived from the pressure signals detected from the force sensor is shown in Figure 2B. The pressure data was sent to a computer for analysis. Figure 3 shows the short-term blood pressure measurement results, illustrating mean and variation of the systolic (SYS) blood pressure 310 and diastolic (DIA) blood pressure 320 readings taken from the single force sensor arm band. For the systolic blood pressure readings 310, a calibration measurement of 131 mmHg was taken and the average blood pressure reading taken with the blood pressure monitoring device, such as device 100, was 133 mmHg. For the diastolic blood pressure readings 320, a calibration measurement of 86 mmHg was taken and the average blood pressure reading taken with the blood pressure monitoring device, such as device 100, was 91.9 mmHg.

[0044] Methods for monitoring blood pressure, using the device 100 described above, are also disclosed herein. In operation, a computing device, such as computing device 120 or remote computing device 140, receives at least one pressure signal at each time in a series of regular times during a monitoring period. As described above, pressure signals may be acquired continuously, once per minute, once per hour, several times per day, etc. The monitoring period may range from about one minute to continuously. The at least one pressure signal is detected by the at least one force sensor 110 coupled to the positioning device 102. The positioning device 102 is configured to position the at least one force sensor over or near an artery of a patient and to maintain contact between the patient's skin and the at least one force sensor. The computing device 120 or remote computing device 140 determines a value, corresponding to a systolic or a diastolic blood pressure, for the at least one pressure signal at each time. The value of the at least one pressure signal at each time in the series and a corresponding time are stored by the computing device in a memory unit, such as, memory unit 124. The computing device may transmit a message, including the stored values of each pressure signal and the corresponding times to, for example, a remote device, such as a smart phone or mobile processing device, a remote server or database, or to the monitoring device itself.

[0045] The method may also be carried out where the at least one force sensor 110 comprises a plurality of force sensors arranged in an array 150. In such examples, the computing device, such as computing device 120 or remote computing device 140, receives a plurality of pressure signals from the plurality of force sensors at each time in the series of regular times during the monitoring period. The computing device may select from the plurality of pressure signals an optimal pressure signal at each time in the series. A selection of the optimal pressure signal may be based on the value determined for each of the plurality of pressure signals. The computing device may store the value of the optimal pressure signal and the corresponding time in the memory unit.

[0046] Further, the method may include receiving, by the computing device, a motion signal at one or more of each time in the series of regular times. The motion signal is detected by at least one motion sensor, such as motion sensor 130, and corresponds to a movement of one or more of the at least one force sensors, the positioning device, or the computing device. A value of the movement signal may be determined by the computing device. If the value exceeds a threshold, then the computing device may store in the memory unit, in addition to the corresponding time, one or more of: (i) an error message, (ii) an indication the threshold was exceeded, or (iii) a value of zero. If the value of the motion signal is at or beneath the threshold, then the computing device may store in the memory unit, the value of each pressure signal and the corresponding time.

[0047] A blood pressure treatment plan may also be determined in accordance with the method. The blood pressure treatment plan may be based, at least in part, on the stored values of each pressure signal and the corresponding times. Further, determining the blood pressure treatment plan may comprise transmitting the stored values of each pressure signal and the corresponding times to a physician, such as the patient's treating doctor for consideration, and receiving, by the computing device, feedback from the physician, such as recommendations for actions to take by the patient in order to lower his or her blood pressure. Determining the blood pressure treatment plan may additionally or alternatively comprise comparing the stored values of each pressure signal to one or more thresholds stored in the memory unit. These may include thresholds for identifying healthy and unhealthy blood pressures and may be associated with recommended courses of action, including seeking immediate medical attention, engaging in physical activity, or drug treatment.

[0048] Figure 4 illustrates another example blood pressure monitoring device 400. The novel multi-modality blood pressure monitoring device 400 is configured to provide simple, robust, and calibrated 24-hour blood pressure monitoring in ambulatory patients to overcome the limitations of current systems is provided herein. The example device 400 may provide for 24-hour blood pressure measurement and expand diagnosis and treatment options for hypertension. While the device is referred to as "24-hour" to show it is capable of collecting data 24 hours a day, the device has the ability to store months to years-worth of blood pressure data. [0049] Similar to device 100 described above with reference to Figures 1A and IB, blood pressure monitoring device 400 may include a positioning device 402, with a housing 404 mounted thereon. The housing 404 may have a first end 406 and a second end 408. An actuator 418 is coupled to the housing 404 between the first end 406 and the second end 408. The blood pressure monitoring device 400 further includes one or more force sensors 410, which may include a first force sensor matrix 412 coupled to the housing 404 between the first end of the housing 406 and the actuator 418, a second force sensor matrix 414 coupled to one or more of the housing 404 and the actuator 418, and a third force sensor matrix 416 coupled to the housing 404 between the actuator 418 and the second end of the housing 408. Each of the first 412, second 414 and third 416 force sensor matrices may comprise two or more individual force sensors. The sensor matrices may be affixed to a conformal surface, such as conformal polystyrene. The upper left panel of Figure 5 schematically illustrates the first 412, second 414 and third 416 force sensor matrices positioned over the brachial artery of a human. The device 400 may provide 24-hour ambulatory self-calibrated blood pressure measurement without the need for an inflation cuff, which may improve patient compliance and provide the clinician with detailed blood pressure information leading to more precise clinically actionable outcomes.

[0050] In some examples, the housing may have a length ranging from about 3 cm to about 6cm, a width ranging from about 3 cm to about 6cm and a height ranging from about lcm to about 3cm. The housing and/or the three sensor matrices may, in some examples, be flexible or rigid or have properties that range between flexible and rigid. In some examples, the housing and/or the three sensor matrices may be shaped to conform to the shape of the body, such as the shape of the upper arm. For example, the housing and/or the three sensor matrices may be convex in shape. Further, as shown in Figure 5, the housing 404 may define a window 417 between the first force sensor matrix 412 and the third force sensor matrix 416. The second force sensor matrix 414 is at least partially disposed within the window 417. Various housing shapes and structures and placements or types of force sensors are contemplated herein.

[0051] The device 400 further includes a computing device 420, having processor 422, a memory unit 424 having computer-readable program instructions 426 executable by the processor 422 stored thereon, and a communications link 428. The computer-readable program instructions 126 are executable by the processor 422 to provide the functionality of the blood pressure monitoring device 400 described herein. In some examples, the processor 422 is a microprocessor coupled to the first 412, second 414, and/or third 416 force sensor matrices. The processor 422 is configured to control the actuator 418. Further, the processor 422 is configured to receive a signal containing a measurement from the first 412, second 414, and/or third 416 force sensor matrices.

[0052] The first 412, second 414 and third 416 force sensor matrices may be provided as any type of force sensor, including piezoresistive, capacitive, electromagnetic, piezoelectric, optical, potentiometric, resonant, thermal and/or ionization force sensors. Increased sensor density can be achieved by using smaller form factor (0204) chip force sensors. This smaller size may allow the elements in the matrix to be staggered or offset from one another thus allowing a higher packing factor and better pulse point coverage. Printed conductor technology may be used to reduce interconnect size on conformal surfaces of the housing 404. Increased signal processing, which may be necessary due to increased sensor density, may be provided by embedding a dedicated low power, high performance microprocessor, such as processor 422, combined with efficient array processing coding schemes.

[0053] Additionally, the blood pressure monitoring device 400 may also include a communications link 428 for communicating with a remote computing device 440. Similar to that described above with respect to device 100, the remote computing device 440 may be any device having computing capabilities that is remote from the wearable blood pressure monitoring device 400, such as a smart phone or other mobile computing device or remote server. The raw sensed blood pressure data or data processed by the computing device 420 housed on the device 400 may be transmitted to the remote computing device 440 for storage, processing, or review by a third party, such as a physician. The pressure data collected by device 400 and transmitted to a remote computing device 440 may be compatible with an example electronic health records management system. The device 400 may also transmit data according to standards or guidelines in order to protect the confidentiality and security of healthcare information as well as other data requirements. Further, the blood pressure monitoring device 400 may also include a movement sensor 430, an activity sensor 432 and/or a health sensor 434 which may have similar features, configurations and functionality to movement sensor 130, activity sensor 132 and health sensor 134 described above with respect to device 100. Additional sensors, such as interfacial pressure and accelerometers, may also be provided on the device 400. [0054] The actuator 418 is configured to apply a force, such as a continuous static force, to the second force sensor matrix 414. In some examples, the continuous static force applied by the actuator to the second force sensor matrix 414 ranges from about 0 to about 8 pounds. The magnitude of the continuous static force depends on the amplitude of the force and the surface area of the actuator. In some examples, the continuous static force may have a magnitude of up to 300 mmHg spread over a displacement surface sufficient to occlude the artery, such as the brachial artery. The actuator 418 may be any device or configuration of devices sufficient to apply the requisite force to the second force sensor matrix 414. For example, the actuator 418 may be provided as an electric motor. In some examples, the actuator 418 may be a rotating electric motor coupled to a cam that pushes on the second sensor matrix 414. As the miniature motor steps through its rotation, the cam turns and produces an ever greater deflection of the second sensor matrix 414. The actuator 418 may also take the form of either a different motor or a precision linear actuator. In addition, actuator performance may be modified or refined via a software revision for the processor 422.

[0055] The example blood pressure monitoring device 400 uses unique miniaturized sensing matrices 412, 414, 416 and a calibrated occlusion/applanation actuator 418 positioned on an arm over the brachial artery pulse point. An exploded view of device 400 is shown in the dotted circles of Figure 5. The three sensor matrices 412, 414, 416 span the subcutaneous artery. One sensor matrix is located upstream, such as first sensor matrix 412, and another downstream, such as third sensor matrix 416. The second sensor matrix 414, positioned between the first 412 and third 416 matrices, is coupled to a calibrated force actuator 418 that moves independently of the other two matrices to collapse the artery by applying a force.

[0056] The multi-modality blood pressure monitoring device 400 is designed to utilize the strengths of four common non-invasive blood pressure measurement techniques— auscultatory, oscillometric, pulse wave velocity (PWV) and tonometry. By using the advantages of each technique, multiple estimates of blood pressure can be obtained and used for a more accurate blood pressure measurement. The blood pressure monitoring device 400 achieves multi-modality blood pressure measurement through the use of the three novel force sensor matrices 412, 414, 416. More specifically, the first 412 and third 416 matrices are used for PWV, auscultatory and oscillometric methods; the second sensor matrix 414 is used for calibration and tonometry. [0057] By observing the upstream 412 and downstream 416 force matrices during application of force by the actuator 418, arterial occlusion is detected by the downstream sensor matrix 416 and the pressure required to occlude the artery is known from the calibrated force sensor 414, thereby establishing systolic blood pressure (top right panel Figure 5). As the applied force decreases, the downstream matrix 416 detects momentary waves of blood pressure, incorporating oscillometric blood pressure detection into this blood pressure monitoring device 400 (bottom right panel Figure 5). As the applied force decreases, the upstream and downstream matrices readings become identical with a phase delay due to PWV (bottom left panel Figure 5). When these pressure waveforms are identical, the diastolic blood pressure is measured by the applied force and PWV can be computed. Also during the time period between total arterial occlusion (systolic blood pressure) and high correlation (diastolic blood pressure), the artery is in a partial state of applanation thus allowing for tonometry blood pressure measurement. As used herein, "applanation" means abnormal flattening of a convex surface.

[0058] The example blood pressure monitoring device 400 may also improve blood pressure measurement by using autonomous self-calibration, thereby removing the requirement of patient interaction with the device and improving compliance. This autonomous self-calibration is achieved by utilizing force actuator 418 coupled to the second sensor matrix 414. In operation, the actuator 418 may apply a known force until occlusion of the artery occurs and the known applied force at which this occurs is used to determine systolic blood pressure. Next, the applied force is slightly reduced until flow is determined by the downstream force sensor matrix, third sensor matrix 416, and the actuator 418 reapplies a force until occlusion occurs. The processor 422 may repeat this process several times over a short period of time, thereby obtaining multiple estimates of the systolic blood pressure for better accuracy. The actuator force is then reduced until the first (upstream) force sensor matrix 412 and third (downstream) force sensor matrix 416 indicate their pressure waveforms are highly correlated, and the force at which this occurs is related to diastolic blood pressure. This process may also be repeated over a short amount of time through precise microprocessor control of the actuator 418 thereby obtaining multiple diastolic blood pressure readings safely. Calibration may occur throughout the day to maintain highly accurate blood pressure measurements during 24-hour ambulatory conditions. To promote patient comfort PWV will be the primary blood pressure measurement in the time periods between self- calibrations.

[0059] To assist in the capture of blood pressure waves, the example blood pressure monitoring device 400 may use three densely-populated force sensor matrices 412, 414, 416 affixed to a housing 404. This arrangement permits at least one force sensor to be positioned over the brachial artery for each of the three force sensor matrices and allows for blood pressure measurement even if the force sensors move relative to the brachial artery pulse point. A high-speed microcontroller 460 detects the patient's arm motion using an accelerometer and may determine the best time to collect blood pressure data through PWV or if recalibration is required. The accelerometer may be a three-axis accelerometer or may have any other number of axes. The high-speed microcontroller 460 also continuously scans the three force sensor matrices and is capable of capturing the PWV, and using the iterative self-calibration techniques described above.

[0060] Figures 6 A, 6B and 6C illustrate the blood pressure monitoring device's 400 ability to perform auscultatory, oscillometric and PWV measurements, respectively. Specifically, Figure 6A illustrates the measured applanation, upstream pressure and upstream force; Figure 6B illustrates measured downstream pressure and force prior, during and after applanation, demonstrating oscillometric measurements; Figure 6C illustrates measured tonometry. Figure 6D illustrates upstream and downstream force sensors demonstrating pulse-wave velocity. The measurements illustrated in Figures 6A-6C were taken on a mock brachial artery. A syringe was attached to one end of the mock artery and the other end was terminated. The syringe and mock artery were filled with water and the plunger in the syringe was used to control the pressure in the mock artery. In summary, it was shown that with multiple sensors, the device can withstand minor changes in sensor location relative to the pulse point, and multiple sensors help establish the contact force between the device and the pulse point.

[0061] Methods for monitoring blood pressure, using the device 400 described above, are also disclosed herein. In operation, the housing 404 is coupled to a patient. Each of the first 412, second 414 and third 416 force sensor matrices are aligned with an artery such that the first force sensor matrix 412 is arranged upstream from the third force sensor matrix 416. A force is applied by the actuator 418 to the first sensor matrix 414 until the artery is occluded and a first systolic blood pressure is determined by the processor 422. The actuator reduces the force applied to the second force sensor matrix 414 until the third force sensor matrix 416 detects blood flow. The actuator then reapplies force to the second force matrix 414 until occlusion occurs again and a second systolic blood pressure reading is determined by the processor 422. The method further includes reducing the force applied to the second force sensor matrix 412 and detecting pressure waveforms by the first 412 and third 416 force sensor matrices. The processor 422 determines when the pressure waveforms are correlated and determines a diastolic blood pressure reading. A tonometry reading may be determined by the processor 422 when the artery is partially occluded. A pulse wave velocity reading may be determined by the first 412 and the third 416 force sensor matrices.

[0062] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims.

Claims

CLAIMS What is claimed is:

1. A device, comprising:

at least one force sensor having a bottom surface configured to detect an arterial force;

a positioning device coupled to the at least one force sensor, wherein the positioning device is configured to apply a continuous static force to the at least one force sensor in order to position the at least one sensor over or near an artery of a patient and to maintain contact between a patient's skin and the bottom surface of the at least one force sensor, wherein the positioning device is untethered and portable; and

a computing device in communication with one or both of the positioning device and the at least one force sensor, wherein the computing device is configured to receive a signal containing a measurement from the at least one force sensor.

2. The device of claim 1, wherein the at least one force sensor comprises a plurality of force sensors.

3. The device of claim 2, wherein the plurality of force sensors are arranged in an array having a perimeter that is polygonal, rectangular, square, or circular.

4. The device of any of claims 1-3, wherein the at least one force sensor is selected from the group consisting of: a piezoresistive force sensor, a capacitive force sensor, an electromagnetic force sensor, a piezoelectric force sensor, an optical force sensor, a potentiometric force sensor, a resonant force sensor, a thermal force sensor and an ionization force sensor.

5. The device of any one of claims 1-4, wherein the continuous static force applied by the positioning device to the at least one force sensor ranges from about 0 to about 8 pounds.

6. The device of any one of claims 1-5, wherein the bottom surface of the at least one force sensor detects the arterial force ranging from about 0 pounds to about 8 pounds.

7. The device of any one of claims 1-6, further comprising one or more of a movement sensor, an activity sensor, or a health sensor coupled to one or more of the positioning device, the at least one force sensor and the computing device.

8. A method for monitoring blood pressure, the method comprising:

receiving, by a computing device, at least one pressure signal at each time in a series of regular times during a monitoring period, wherein the at least one pressure signal is detected by at least one force sensor coupled to a positioning device, wherein the positioning device is configured to position the at least one force sensor over or near an artery of a patient and to maintain contact between a patient's skin and the at least one force sensor;

determining, by the computing device, a value for the at least one pressure signal at each time, wherein the value corresponds to a systolic or a diastolic blood pressure; and storing, by the computing device, the value of the at least one pressure signal at each time and a corresponding time in a memory unit.

9. The method of claim 8, wherein the monitoring period ranges from about one minute to continuous.

10. The method of any one of claims 8-9, wherein the at least one force sensor comprises a plurality of force sensors in an array, wherein the step of receiving, by the computing device, at least one pressure signal at each time in a series of regular times during a monitoring period comprises receiving a plurality of pressure signals from the plurality of force sensors at each time in the series.

11. The method of claim 10 further comprising:

selecting, by the computing device, an optimal pressure signal at each time in the series from the corresponding plurality of pressure signals based on the value determined for each of the plurality of pressure signals, wherein the step of storing, by the computing device, the value of each pressure signal and the corresponding time in a memory unit comprises storing the value of the optimal pressure signal and the corresponding time in the memory unit.

12. The method of any one of claims 8-11, further comprising:

receiving, by the computing device, a motion signal at one or more of each time in the series of regular times, wherein the motion signal is detected by at least one motion sensor, wherein the motion signal corresponds to a movement of one or more of the at least one force sensor, the positioning device or the computing device;

determining, by the computing device, a value of the movement signal; and if the value of the motion signal exceeds a threshold, then storing, by the computing device, one or more of (i) an error message, (ii) an indication the threshold was exceeded, or (iii) a value of zero, and the corresponding time in the memory unit;

if the value of the motion signal is at or beneath the threshold, then storing, by the computing device, the value of each pressure signal and the corresponding time in a memory unit.

13. The method of any one of claims 8-12, further comprising sending, by the computing device, a message including at least the stored values of each pressure signal and the corresponding times.

14. The method of any one of claims 8-13, further comprising:

determining, by the computing device, a blood pressure treatment plan based at least in part on the stored values of each pressure signal and the corresponding times.

15. The method of claim 14, wherein determining, by the computing device, a blood pressure treatment plan further comprises:

transmitting the stored values of each pressure signal and the corresponding times to a physician; and

receiving, by the computing device, feedback from the physician.

16. The method of claim 14, wherein determining, by the computing device, a blood pressure treatment plan further comprises:

comparing the stored values of each pressure signal to one or more thresholds stored in the memory unit.

17. The method of any one of claims 8-16, wherein the method is carried out by the device of any one of claims 1-7.

18. A non-transitory computer readable medium having stored therein instructions executable by a computing device to cause the computing device to perform functions comprising:

determining, by the computing device, a value for each pressure signal, wherein the value corresponds to a systolic or a diastolic blood pressure; and

storing, by the computing device, the value of each pressure signal and a

corresponding time in a memory unit.

19. A device, comprising:

a housing having a first end and a second end;

an actuator coupled to the housing between the first end and the second end of the housing;

a first force sensor matrix coupled to the housing between the first end of the housing and the actuator;

a second force sensor matrix coupled to one or more of the housing and the actuator; and

a third force sensor matrix coupled to the housing between the actuator and the second end of the housing.

20. The device of claim 19, further comprising at least one microprocessor coupled to one, two, or all three of the first, second and third force sensor matrices.

21. The device of claim 20, wherein the at least one microprocessor is configured to control the actuator.

22. The device of any one of claims 20 or 21 , wherein the at least one microprocessor is configured to receive a signal containing a measurement from one, two or all three of the first, second and third force sensor matrices.

23. The device of any of claims 19-22, wherein the actuator comprises an electric motor.

24. The device of any one of claims 19-23, wherein the housing has length ranging from about 3 cm to about 6 cm, has a width ranging from about 3 cm to about 6 cm, and has a height ranging from about 1 cm to about 3 cm.

25. The device of any one of claims 19-24, wherein the second force sensor matrix is at least partially disposed within the window.

26. The device of any of claims 19-25, wherein the actuator is configured to apply a force to the second force sensor matrix ranging from about 0 pounds to about 8 pounds.

27. The device of any of claims 19-26, wherein each of the first, second, and third force sensor matrices comprise two or more individual force sensors.

28. The device of any one of claims 20-27, further comprising a high-speed microcontroller coupled to the housing.

29. The device of any of claims 19-28, further comprising one or more of a movement sensor, an activity sensor, or a health sensor coupled to the housing.

30. The device of any of claims 20-30 further comprising a communications link for transmitting the measurements from the microprocessor to a remote computing device.

31. A method, comprising:

providing the device according to any one of claims 19-30; coupling the housing to a patient and aligning each of the first, second and third force sensor matrix with an artery such that the first force sensor matrix is arranged upstream from the third force sensor matrix;

applying a force to the second force sensor matrix, via the actuator, until the artery is occluded;

determining a first systolic blood pressure via the microprocessor;

reducing the force applied to the second force sensor matrix until the third force sensor matrix detects blood flow;

reapplying the force to the second force sensor matrix, via the actuator, until occlusion occurs; and

determining a second systolic blood pressure reading.

32. The method of claim 31 , further comprising:

reducing the force applied to the second force sensor matrix;

detecting pressure waveforms via the first and third force sensor matrices;

determining via the microprocessor that the pressure waveforms are correlated; and determining diastolic blood pressure reading via the microprocessor.

33. The method of any one of claims 33 or 34, further comprising:

determining a tonometry blood pressure reading via the microprocessor when the artery is partially occluded.

34. The method of any one of claims 31-33, further comprising:

detecting pulse wave velocity via the first and the third force sensor matrices.