NON-INVASIVE BLOOD PRESSURE MEASUREMENT SYSTEM

• US 20190090760A1
• Filed: 07/27/2018
• Published: 03/28/2019
• Est. Priority Date: 07/22/2010
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Kinast, Eric Karl, Telfort, Valery G.
• Granted Patent: US 11,234,602 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2562/0204 Acoustic sensors
• CPC Class Codes: A61B 2562/04 Arrangements of multiple sensors of the same type
• CPC Class Codes: A61B 2562/06 Arrangements of multiple sensors of different types
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/02255 the pressure being controlled by plethysmographic signals, e.g. derived from optical sensors
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/349 : Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/7203 : for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7246 : using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/725 : using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: A61B 5/7271 : Specific aspects of physiological measurement analysis A61B5/316, A61B5/349 and A61B5/374 take precedence
• CPC Class Codes: A61B 7/00 : Instruments for auscultation
• CPC Class Codes: A61B 7/02 : Stethoscopes acoustic details thereof G10K11/00
• CPC Class Codes: A61B 7/045 : Detection of Korotkoff sounds A61B5/0225 takes precedence; measuring blood pressure A61B5/021
• CPC Class Codes: A61B 8/02 : Measuring pulse or heart rate

Abstract

A system for non-invasively determining an indication of an individual'"'"'s blood pressure is described. In certain embodiments, the system calculates pulse wave transit time using two acoustic sensors. The system can include a first acoustic sensor configured to monitor heart sounds of the patient corresponding to ventricular systole and diastole and a second acoustic sensor configured to monitor arterial pulse sounds at an arterial location remote from the heart. The system can advantageously calculate a arterial pulse wave transit time (PWTT) that does not include the pre-ejection period time delay. In certain embodiments, the system further includes a processor that calculates the arterial PWTT obtained from the acoustic sensors. The system can use this arterial PWTT to determine whether to trigger an occlusive cuff measurement.

Claims

1. A method of monitoring blood pressure of a patient, the method comprising:

receiving a physiological electrical signal from an electrical sensor coupled with a patient, the physiological electrical signal configured to reflect electrical activity of the patient'"'"'s heart;

receiving a cardiac ejection signal from a second sensor coupled with the patient, the cardiac ejection signal reflecting a cardiac ejection event associated with ejection of blood from the patient'"'"'s heart;

receiving an arterial pulse signal from an acoustic sensor coupled with a limb of the patient;

determining an arterial pulse wave transit time (PWTT) that compensates for a pre-ejection period of a cardiac cycle associated with the patient'"'"'s heart, based at least partly on the physiological electrical signal, the cardiac ejection signal, and the arterial pulse signal; and

triggering an occlusive blood pressure cuff to obtain a blood pressure measurement from the patient responsive to a change in the arterial PWTT.

2. The method of claim 1, wherein said determining further comprises calculating a pre-ejection period between a feature of the physiological electrical signal and a feature of the cardiac ejection signal.

3. The method of claim 2, wherein said determining further comprises subtracting the pre-ejection period from a time difference between a feature of the physiological electrical signal and a feature of the pulse wave signal to produce the arterial PWTT.

4. The method of claim 2, further comprising calculating an overall PWTT by calculating a time difference between a feature of the physiological electrical signal and the arterial pulse signal.

5. The method of claim 4, further comprising performing one or both of the following:

averaging the pre-ejection period with one or more previously-calculated pre-ejection periods; and

averaging the overall PWTT with one or more previously-calculated overall PWTT values.

6. The method of claim 5, further comprising:

subtracting the averaged pre-ejection period from either the averaged overall PWTT or the overall PWTT to produce the arterial PWTT.

7. The method of claim 5, wherein the averaging of the pre-ejection period is applied at a different rate than the averaging applied to the overall PWTT.

8. The method of claim 2, further comprising using a previously-calculated pre-ejection period to calculate the arterial PWTT in place of the calculated pre-ejection period in response to determining that the cardiac ejection signal is insufficiently indicative of the cardiac ejection event.

9. A system for monitoring blood pressure of a patient, the system comprising:

a blood pressure analyzer comprising one or more processors, the blood pressure analyzer configured to;

receive an electrocardiograph (ECG) signal from an ECG sensor coupled with a patient,

receive a cardiac ejection signal from a second sensor coupled with the patient, the cardiac ejection signal configured to reflect ejection of blood from the patient'"'"'s heart,

receive a pulse signal from an acoustic sensor coupled with a limb of the patient, and

determine an arterial pulse wave transit time (PWTT) based at least partly on the ECG signal, the cardiac ejection signal, and the pulse signal; and

a non-invasive blood pressure module configured to trigger an occlusive blood pressure cuff to obtain a blood pressure measurement from the patient responsive to a change in the arterial PWTT.

10. The system of claim 9, wherein the cardiac ejection signal comprises an acoustic signal responsive to a heart sound of the patient'"'"'s heart.

11. The system of claim 10, wherein the cardiac ejection signal is configured to be obtained by an acoustic sensor.

12. The system of claim 9, wherein the cardiac ejection signal comprises an impedance signal responsive to impedance of a chest cavity of the patient.

13. The system of claim 12, wherein the cardiac ejection signal is configured to be obtained by a bioimpedance sensor.

14. The system of claim 9, wherein the acoustic sensor is configured to be placed proximate a radial artery or ulnar artery of the patient.

15. The system of claim 9, wherein the acoustic sensor is configured to be placed proximate a carotid artery of the patient.

16. The system of claim 9, wherein the blood pressure analyzer is configured to determine the arterial PWTT by at least:

determining an initial PWTT based at least in part on a time difference between a feature of the ECG signal and a feature of the pulse signal;

determining a pre-ejection period based at least in part on a time difference between the initial PWTT and a feature of the cardiac ejection signal; and

determine the arterial PWTT based at least in part on a difference between the initial PWTT and the pre-ejection period.

17. The system of claim 9, wherein the blood pressure analyzer is further configured to determine the arterial PWTT by at least determining a time difference from a centroid of a first heart sound detected by the second sensor to a feature of the pulse signal.

18. The system of claim 17, wherein the first heart sound comprises the cardiac ejection signal.

19. A method for monitoring blood pressure of a patient, the method comprising:

receiving physiological electrical information associated with a patient, the physiological electrical information configured to reflect electrical activity of the patient'"'"'s heart;

receiving a cardiac ejection information associated with the patient, the cardiac ejection information reflecting ejection of blood from the patient'"'"'s heart;

receiving arterial pulse information associated with a limb of the patient from an acoustic sensor; and

determining an arterial pulse wave transit time (PWTT) measurement that compensates for a pre-ejection period of a cardiac cycle associated with the patient'"'"'s heart, based at least partly on the physiological electrical information, the cardiac ejection information, and the arterial pulse information;

wherein at least said determining is performed by one or more processors.

20. The method of claim 19, further comprising:

adjusting an averaging parameter for an averaging filter configured to be applied to a set of arterial PWTT measurements, including the arterial PWTT measurement, said adjusting being performed according to correlated signal information obtained from a physiological signal that is at least partially correlated with the set of arterial PWTT measurements; and

applying the averaging filter to the set of arterial PWTT measurements to thereby selectively reduce noise in the set of arterial PWTT measurements.

21. The method of claim 20, wherein the physiological signal from which the correlated signal information is obtained is a heart rate signal.

22. The method of claim 20, wherein the physiological signal from which the correlated signal information is obtained is a respiratory rate signal.

23. The method of claim 20, wherein the averaging parameter comprises one or more of the following:

an averaging time, a filter order, a number of averaging points, and a value of one or more coefficients.

24. The method of claim 20, further the correlated signal information comprises a statistic.

25. The method of claim 24, wherein the statistic comprises a standard deviation of the physiological signal.

26. The method of claim 25, wherein said adjusting comprises selecting a longer averaging time responsive to the standard deviation having a higher value compared with a shorter averaging time responsive to the standard deviation having a lower value.

27. The method of claim 26, wherein the averaging filter is configured to have a longer averaging time for a first portion of the set of arterial PWTT measurements and a shorter averaging time for a second portion of the set of arterial PWTT measurements.

28. The method of claim 19, further comprising:

receiving a correlated signal from the patient, the correlated signal being at least partially correlated with a set of arterial PWTT measurements, the set of arterial PWTT measurements comprising the arterial PWTT measurement; and

adaptively compensating a noise component of the set of arterial PWTT measurements using the correlated signal.

29. The method of claim 28, wherein said adaptively compensating comprises applying an adaptive filter to the set of arterial PWTT measurements.

30. The method of claim 29, wherein said applying the adaptive filter comprises using the correlated signal as a noise reference for the adaptive filter.

31. The method of claim 28, wherein the correlated signal comprises a heart rate signal.

32. The method of claim 28, wherein the correlated signal comprises a respiratory rate signal.

33. The method of claim 19, further comprising adjusting the arterial PWTT based on changes in previous arterial PWTT measurements that occurred per change in blood pressure of the patient over time.