Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/02—Detecting, measuring or recording for evaluating the cardiovascular system, e.g. pulse, heart rate, blood pressure or blood flow
  • A61B5/021—Measuring pressure in heart or blood vessels
  • A61B5/02108—Measuring pressure in heart or blood vessels from analysis of pulse wave characteristics
  • A61B5/02116—Measuring pressure in heart or blood vessels from analysis of pulse wave characteristics of pulse wave amplitude
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/02—Detecting, measuring or recording for evaluating the cardiovascular system, e.g. pulse, heart rate, blood pressure or blood flow
  • A61B5/021—Measuring pressure in heart or blood vessels
  • A61B5/022—Measuring pressure in heart or blood vessels by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
  • A61B5/02225—Measuring pressure in heart or blood vessels by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers using the oscillometric method
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/02—Detecting, measuring or recording for evaluating the cardiovascular system, e.g. pulse, heart rate, blood pressure or blood flow
  • A61B5/026—Measuring blood flow
  • A61B5/0261—Measuring blood flow using optical means, e.g. infrared light
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration or pH-value ; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid or cerebral tissue
  • A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration or pH-value ; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid or cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B2560/00—Constructional details of operational features of apparatus; Accessories for medical measuring apparatus
  • A61B2560/02—Operational features
  • A61B2560/0223—Operational features of calibration, e.g. protocols for calibrating sensors

Definitions

• the present invention pertains generally to devices for monitoring the blood pressure of a patient. More particularly, the present invention pertains to devices that continuously, or intermittently, monitor the blood pressure of a patient over an extended period of time.
• the present invention is particularly, but not exclusively, useful as a system and method for periodically calibrating an oximeter to provide uninterrupted indications of blood pressure, where the oximeter pulse is a faithful surrogate for blood pressure determined by routine measures (sphygmomanometer cuff or interarterial catheter). BACKGROUND OF THE INVENTION
• Blood pressure readings are typically made with a sphygmomanometer by positioning a pressure cuff around a patient's extremity containing a large artery.
• the cuff is usually placed on an arm. Once the cuff has been properly placed, pressure is imposed on the arm by the cuff to occlude the artery. This cuff pressure is then gradually reduced and transduced to first read a pressure at which a turbulent flow of blood begins, and to then read a pressure at the point where turbulence disappears.
• Systolic pressure is the point where turbulent flow starts and diastolic pressure is the point where turbulent flow ends.
• the systolic and diastolic pressures provide what is commonly referred to as a patient's blood pressure reading.
• a stethoscope is used to measure a patient's blood pressure
• the Korotkoff sounds are auscultated to identify the systolic and diastolic pressures. From a monitoring stand point an accurate systolic pressure is most important.
• the occurrence of each cardiac cycle and resultant blood flow can be detected by an oximeter.
• the oximeter functions using a photoelectric signal which varies in strength in accordance with oxygenation values as blood pulses through the area of signal origin.
• the amplitudes of the oxygenation values are unique for each pulse, and these values are related directly to the systolic and diastolic blood pressure of the patient.
• an object of the present invention to provide a system for monitoring the blood pressure of a patient by continuously measuring blood oxygenation values, and for correlating pulse oxygenation values in each cardiac cycle with the systolic and diastolic pressures of a patient.
• Another object of the present invention is to provide a system for monitoring the blood pressure of a patient by continuously measuring blood oxygenation values at a point in time and over an extended period of time.
• Still another object of the present invention is to provide a system and method for continuously monitoring blood pressure that is easy to use and is comparatively cost effective.
• a system for continuously monitoring the blood pressure of a patient combines the use of a blood pressure reading device (e.g. a sphygmomanometer) with the use of a device for monitoring blood oxygenation values (e.g. an oximeter).
• a blood pressure reading device e.g. a sphygmomanometer
• the sphygmomanometer is used to calibrate the signal from the oximeter (pulse wave form) which can then be used to continuously or discontinuously measure the blood pressure.
• these indications are monitored over a predetermined time interval before another calibration of the signal is required.
• calibration is accomplished using a sphygmomanometer (or in rare instances, with an interarterial pulse measurement).
• the oximeter pulse bears an inverse relationship to the sphygmomanometer measurement of blood pressure.
• the systolic cuff blood pressure is the point at which a small amount of turbulent flow begins to occur; this should produce no detectable flow at the oximeter and will thus represent zero pressure for the oximeter pulse.
• cuff pressure is progressively reduced, however, and as blood flow past the cuff increases, there will come a point where a pulse is first detected via the oximeter.
• This detection represents the diastolic pressure for the pulse oximeter and has a value that is equal to the pressure in millimeters of mercury between this point and the diastolic pressure previously determined by the sphygmomanometer.
• the diastolic pressure that is determined by the sphygmomanometer should be accompanied by a fully developed oximeter pulse amplitude and should be calibrated with systolic pressure determined by the sphygmomanometer.
• the system of the present invention includes a unit for periodically measuring the systolic and the diastolic blood pressures in an artery of the patient during a measurement cycle. Specifically, a systolic pressure is measured at the beginning of the measurement cycle and a diastolic pressure is measured at the end of the measurement cycle. This is done by any of several ways, all well known in the pertinent art (e.g. a sphygmomanometer). Typically, in the event, an inflatable cuff is positioned around an arm of a patient and it is then inflated to establish an initial cuff pressure for occluding an artery of the patient.
• a control value is then selectively operated to release the cuff pressure to allow blood flow through the artery. It is well known that in such an operation, measurements (i.e. readings) of the systolic pressure and the diastolic pressure can be obtained.
• a device for detecting blood oxygen content in the cardiovascular system of a patient.
• each pulse that is measured by the oximeter has a unique amplitude which is indicative of the blood oxygenation value at the time of the pulse.
• the device for detecting blood pressure pulses e.g. oximeter
• a computer is provided in the system of the present invention for correlating the pulse amplitude values that are detected by the photoelectric oximeter unit, with a cuff determination of blood pressure measurements that are obtained by the sphygmomanometer. Thereafter, with the correlation that is established by the computer, variations in pulse amplitudes are subsequently detected and these amplitudes are respectively identified as indications of corresponding variations in systolic and diastolic pressures. Such correlations continue during an extended time interval following the measurement cycle. As envisioned for the present invention, the extended time interval may range anywhere from fifteen minutes to several hours.
• a monitor is incorporated to record the indications of systolic pressure that are obtained by computer correlations with the pulse amplitudes detected by the oximeter and the systolic pressure can be presented on a visual display. Significant changes in blood oxygenation should automatically call for a recalibration of the device.
• calibration of the system essentially requires fitting the pulse responses that are detected by an oximeter, with the blood pressure readings that are obtained by a sphygmomanometer. Once a calibration has been completed, the oximeter alone can be used as an indicator of blood pressure. Subsequent calibrations can then be made periodically or whenever it is deemed necessary. The conduct of a calibration will perhaps be best appreciated from a temporal perspective.
• both the sphygmomanometer and the oximeter need to be properly positioned on the patient.
• the sphygmomanometer is positioned on an upper arm of the patient, and the oximeter is positioned on a finger of the same arm.
• the cuff of the sphygmomanometer is then inflated until the artery in the arm is occluded and blood flow into the arm has ceased.
• the blood pressure reading (p-i) and the blood pressure drop ( ⁇ ) are established at time the cuff pressure is further reduced. This reduction in cuff pressure continues until, at a time “t 2 ", the Korotkoff sounds stop to indicate that blood flow in the arm has returned to normal and is fully developed. It is at the time “t 2 " that the patient's diastolic pressure "Pdiastoiic" is measured (i.e. the Korotkoff sounds stop). Also, a second pulse value "V 2 " indicating the fully developed oximetry pulse is detected by the oximeter at the time "t 2 "- The difference between the pulse values Vi and V 2 is then established as a pulse differential " ⁇ ⁇ ".
• ⁇ ⁇ can be compared to ⁇ ⁇ to correlate the pulse metrics of ⁇ ⁇ to the pressure metrics of ⁇ ⁇ . Based on this correspondence, the units of pulse value (oxygenation level) that are measured by the oximeter can be directly converted to units of pressure (mm Hg) that are measured by the sphygmomanometer.
• the pulse value "Vi" which is measured by the oximeter at time "ti" corresponds directly to the patient's diastolic pressure "p d iastoiic".
• Fig. 1 is a schematic presentation of the components used in an operation of the present invention
• Fig. 2 is a representative time line graph for the heartbeat of a patient.
• Fig. 3 is a graphical representation of pressure and pulse measurements required for calibration and operation of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS
• a system for continuously monitoring the blood pressure of a patient is shown and is generally designated 10.
• the system 10 includes a computer 12 that is connected with a pressure unit 14.
• a pressure unit 14 Included in the pressure unit 14 is an inflatable cuff 16 that is connected directly to a manometer 18.
• the pressure unit 14 is functionally the same as, or is similar to, a common sphygmomanometer or interarterial catheter.
• the pulse detector 20 is an oximeter of a type well known in the pertinent art for taking oxygenation readings (hereinafter, the pulse detector 20 may sometimes be referred to as oximeter 20).
• a sensor 22 is incorporated as part of the oximeter 20, and the oximeter 20 is connected directly to the computer 12. Further, the computer 12 is connected to a monitor 24 that may include a visual display 26.
• the inflatable cuff 16 is properly positioned on a patient 28. In Fig. 1 , this positioning is shown to be on the left arm of the patient 28. Additionally, the sensor 22 is positioned on a finger of the patient 28. With these connections, the system 10 is ready for calibration and/or operation.
• Fig. 2 shows a typical graph for heart beats 30 of a patient 28.
• the heart beats 30 are shown to extend through a measurement cycle 32 and, after the measurement cycle 32, on into an extended period of time 34.
• Both Fig. 2 and Fig. 3 show that the measurement cycle 32 begins at a time to and ends at a time t 2 .
• the extended period of time 34 will start at the time t 2 and may continue for as long as a few hours. Further, it is envisioned that the extended period of time 34 may actually include several intermittent continuous intervals of time. In any event, during the extended period of time 34 the pulse of each heart beat 30 will provide pulse values "V", that are detected by the pulse detector (oximeter) 20.
• pulse values "V” are then correlated with blood pressure readings for a systolic pressure “Psystoiic” and a diastolic pressure “Pdiastoiic” that were taken during the measurement cycle 32.
• the pulse detector (oximeter) 20 needs to be calibrated. A calibration of the system 10 for such an operation is best appreciated with reference to Fig. 3.
• Fig. 3 the description of a calibration for the system 10 is best appreciated in a temporal context.
• the patient 28 is connected with the system 10 substantially as shown in Fig. 1. More specifically, the inflatable cuff 16 and the sensor 22 are positioned on the patient 28 in an arrangement of system 10 that is only exemplary. As indicated, with this arrangement, the measurement cycle 32 begins at time t 0 .
• a calibration begins at the time t 0 when the pressure unit 14 measures the systolic pressure (p sy stoiic) of the patient 28.
• the cuff pressure that is being detected by the inflatable cuff 16 is reduced from p sys toiic to a pressure pi.
• the pressure pi is measured when the pulse detector (oximeter) 20 first senses a pulse value V-i . This occurs at the time t
• no pulse values are detected by the pulse detector (oximeter) 20 during the time interval from t 0 to t
• two essential measurements are made at the time ti.
• One is the pulse value V ! which is the lowest pulse value detected by the oximeter 20.
• the other is an initial pressure drop ( ⁇ ) which is the difference between p sys toiic and pi ( ⁇
• the next significant event in the measurement cycle 32 occurs at the time t 2 when the pressure unit 14 measures the diastolic pressure (Pdiastoiic) of the patient 28.
• the pulse detector (oximeter) 20 obtains a pulse value V 2 .
• the pulse value V 2 is the highest pulse value detected by the oximeter 20, and it will occur when the heart cycle has again become fully developed.
• the computer 12 uses the operational parameters obtained during the measurement cycle 32 at times to, ti and t 2 as inputs to establish an operational configuration for the system 10.
• the pulse and pressure differentials i.e. ⁇ ⁇ and ⁇ ⁇
• pulse values "V" obtained from the pulse detector (oximeter) 20 can be used as equivalents of pressure readings taken from the pressure unit 14.
• p sys toiic is equated with V 2 + ⁇ - ⁇ and Pdiastoiic is equated with Vi .
• the pulse detector (oximeter) 20 can be used alone to provide blood pressure readings for the visual display 26 on monitor 24.

Landscapes

• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Physics & Mathematics (AREA)
• Cardiology (AREA)
• Pathology (AREA)
• Animal Behavior & Ethology (AREA)
• Veterinary Medicine (AREA)
• Engineering & Computer Science (AREA)
• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
• Medical Informatics (AREA)
• Molecular Biology (AREA)
• Surgery (AREA)
• Biophysics (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Vascular Medicine (AREA)
• Physiology (AREA)
• Ophthalmology & Optometry (AREA)
• Optics & Photonics (AREA)
• Hematology (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)
• Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=49513076

Family Applications (1)

Country Status (5)

Cited By (3)

Families Citing this family (5)

Citations (3)

Family Cites Families (11)

• 2012
  • 2012-05-04 US US13/464,732 patent/US8951204B2/en active Active
• 2013
  • 2013-04-26 WO PCT/US2013/038363 patent/WO2013165836A1/en not_active Ceased
  • 2013-04-26 EP EP13785164.8A patent/EP2844133B1/en active Active
  • 2013-04-26 CA CA2872574A patent/CA2872574C/en active Active
  • 2013-04-26 JP JP2015510344A patent/JP6224081B2/ja active Active

Patent Citations (3)

Also Published As

Similar Documents

Legal Events