Blood pressure estimation based on pulse wave velocity

• US 10,213,117 B2
• Filed: 07/20/2016
• Issued: 02/26/2019
• Est. Priority Date: 02/18/2016
• Status: Active Grant

• Current Assignee: Philips Healthcare Informatics Incorporated (Koninklijke Philips N.V.)
• Original Assignee: Qualcomm, Inc.
• Inventors: Lading, Lars, Baek, David Boettcher
• Primary Examiner(s): Johnson, Nicole F
• Application Number:
  US15/215,260
• Publication Number:
  US 20170238817A1
• Time in Patent Office: 951 Days
• Field of Search: 600300-301, 600437
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/02 Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/026 Measuring blood flow A61B3/1233, A61B3/1241 take precedence
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/1076 for measuring dimensions inside body cavities, e.g. using catheters A61B3/1005 takes precedence
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/7253 characterised by using transforms
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence

Abstract

One aspect of the subject matter described in this disclosure can be implemented in a device capable of estimating blood pressure. The device includes two or more sensors capable of performing measurements along an artery. The device also includes at least one processing unit coupled with the two or more sensors. The processing unit is capable of accessing one or more parameters including a stress-strain parameter based on a hydrostatic pressure calibration. The processing unit also is capable of determining a pulse transit time (PTT) based on the measurements, and determining a pulse wave velocity (PWV) based on the PTT. The processing unit is further capable of determining a blood pressure based on the PWV and the stress-strain parameter.

Claims

1. A device capable of estimating blood pressure comprising:

two or more sensors capable of performing measurements along an artery of a subject; and

at least one processing unit coupled with the two or more sensors and capable of;

accessing one or more parameters including a stress-strain parameter based on a hydrostatic pressure calibration;

determining a pulse transit time (PTT) of a pulse propagating in the artery based on the measurements performed by the two or more sensors, the PTT being a time during which the pulse propagates from a first physical location to a second physical location;

determining a pulse wave velocity (PWV) based on the PTT; and

determining a blood pressure in the artery based on the PWV and the stress-strain parameter.

2. The device of claim 1, wherein the two or more sensors include at least a first sensor positioned at the first physical location and a second sensor positioned at the second physical location, and wherein the determination of the PTT based on the measurements performed by the two or more sensors includes:

determining a first temporal location of a pulse propagating through the artery based on the measurements performed by the first sensor;

determining a second temporal location of the pulse based on the measurements performed by the second sensor; and

determining the PTT based on the first temporal location and the second temporal location.

3. The device of claim 2, further including a wearable housing that encompasses at least portions of the first sensor and the second sensor, the wearable housing providing a fixed distance of separation between the first sensor and the second sensor, the processing unit being capable of determining the PWV based on the fixed distance of separation and the PTT.

4. The device of claim 3, wherein a magnitude of the fixed distance of separation is less than about 5 centimeters (cm).

5. The device of claim 1, wherein the determination of the blood pressure in the artery based on the PWV and the stress-strain parameter includes determining the blood pressure based on a first relationship between blood pressure and PWV that includes the stress-strain parameter and no other stress-strain parameters.

6. The device of claim 1, wherein the at least one processing unit is capable of performing the hydrostatic pressure calibration to obtain the stress-strain parameter.

7. The device of claim 6, further including at least one elevation sensor coupled with the at least one processing unit and capable of performing elevation measurements associated with a relative or an absolute elevation of the device, the at least one processing unit being capable of determining the stress-strain parameter based on a hydrostatic pressure difference between a first elevation and a second elevation.

8. The device of claim 1, further including a signal processor capable of performing one or more signal processing operations on the measurements performed by the two or more sensors to provide processed arterial distension data.

9. The device of claim 8, wherein one or more of the one or more signal processing operations includes applying a nonlinear function to provide the processed arterial distension data.

10. The device of claim 1, wherein the determination of the PTT based on the measurements performed by the two or more sensors comprises:

performing a correlation operation based on the measurements performed by a first sensor at a first physical location and based on the measurements performed by a second sensor at a second physical location;

determining correlation data as a function of time delay based on the correlation operation;

determining a time delay associated with an approximate maximum of the correlation data; and

determining the PTT based on the determined time delay.

11. A device capable of estimating blood pressure comprising:

one or more sensors capable of performing measurements along an artery of a subject; and

at least one processing unit coupled to the one or more sensors and capable of;

accessing one or more parameters including a stress-strain parameter based on a hydrostatic pressure calibration;

determining a blood flow through the artery based on the measurements from the one or more sensors;

determining a cross-sectional area of the artery based on the measurements from the one or more sensors;

determining a pulse wave velocity (PWV) based on the blood flow and the cross-sectional area, the PWV being a velocity at which an arterial distension waveform envelope propagates; and

determining a blood pressure in the artery based on the PWV and the stress-strain parameter.

12. The device of claim 11, wherein the determination of the PWV based on the blood flow and the cross-sectional area includes determining a derivative estimate of the blood flow as a function of the cross-sectional area.

13. The device of claim 12, wherein the determination of the PWV based on the blood flow and the cross-sectional area further includes determining a value of a constant portion of the derivative estimate.

14. A method of estimating blood pressure comprising:

performing measurements of arterial distension by two or more sensors positioned along an artery of a subject;

determining a pulse transit time (PTT) of a pulse propagating in the artery based on the measurements, the PTT being a time during which the pulse propagates from a first physical location to a second physical location;

determining a pulse wave velocity (PWV) based on the PTT; and

accessing one or more parameters including a stress-strain parameter based on a hydrostatic pressure calibration;

determining a blood pressure in the artery based on the PWV and the stress-strain parameter.

15. The method of claim 14, wherein the two or more sensors include at least a first sensor positioned at the first physical location and a second sensor positioned at the second physical location, and wherein determining the PTT based on the measurements performed by the two or more sensors includes:

determining a first temporal location of a pulse propagating through the artery based on the measurements performed by the first sensor;

determining a second temporal location of the pulse based on the measurements performed by the second sensor; and

determining the PTT based on the first temporal location and the second temporal location.

16. The method of claim 15, wherein the first sensor and the second sensor are encompassed at least partially by a wearable housing, the wearable housing providing a fixed distance of separation between the first sensor and the second sensor, and wherein the determining of the PWV is based further on the fixed distance of separation.

17. The method of claim 14, wherein determining the blood pressure in the artery based on the PWV and the stress-strain parameter includes determining the blood pressure based on a first relationship between blood pressure and PWV that includes the stress-strain parameter and no other stress-strain parameters.

18. The method of claim 14, further including performing the hydrostatic pressure calibration to obtain the stress-strain parameter.

19. The method of claim 18, further including:

performing elevation measurements associated with a relative or an absolute elevation; and

determining the stress-strain parameter based on a hydrostatic pressure difference between a first elevation and a second elevation.

20. The method of claim 14, further including applying a nonlinear function to the measurements performed by the two or more sensors to provide processed arterial distension data.

21. The method of claim 14, wherein the determining of the PTT based on the measurements performed by the two or more sensors comprises:

performing a correlation operation based on the measurements performed by a first sensor at a first physical location and based on the measurements performed by a second sensor at a second physical location;

determining correlation data as a function of time delay based on the correlation operation;

determining a time delay associated with an approximate maximum of the correlation data; and

determining the PTT based on the determined time delay.

22. A method of estimating blood pressure comprising:

performing measurements of arterial distension by one or more sensors positioned along an artery of a subject;

determining a blood flow through the artery based on the measurements;

determining a cross-sectional area of the artery based on the measurements;

determining a pulse wave velocity (PWV) based on the blood flow and the cross-sectional area, the PWV being a velocity at which an arterial distension waveform envelope propagates;

accessing one or more parameters including a stress-strain parameter based on a hydrostatic pressure calibration; and

determining a blood pressure in the artery based on the PWV and the stress-strain parameter.

23. The method of claim 22, wherein the determining of the PWV based on the blood flow and the cross-sectional area includes determining a derivative estimate of the blood flow as a function of the cross-sectional area.

24. The method of claim 23, wherein the determining of the PWV based on the blood flow and the cross-sectional area further includes determining a value of a constant portion of the derivative estimate.