METHODS AND APPARATUS FOR DETERMINING CUFF BLOOD PRESSURE

• US 20140066793A1
• Filed: 08/28/2013
• Published: 03/06/2014
• Est. Priority Date: 08/28/2012
• Status: Active Grant

• Current Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Original Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Inventors: Mukkamala, Ramakrishna, Liu, Jiankun, Hahn, Jin-Oh
• Granted Patent: US 10,136,823 B2
• Time in Patent Office: Days
• US Class Current: 600/494
• 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 5/02208 using the Korotkoff method
• CPC Class Codes: A61B 5/02225 using the oscillometric method
• CPC Class Codes: A61B 5/02241 of small dimensions, e.g. adapted to fingers
• CPC Class Codes: A61B 5/02255 the pressure being controlled by plethysmographic signals, e.g. derived from optical sensors
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence

Abstract

A method is provided for determining blood pressure for a subject using a sphygmomanometer. The method includes: measuring an oscillometric cuff pressure waveform of the subject using the sphygmomanometer; representing the measured waveform with a physical model accounting for mechanics of the cuff, an artery and coupling between the cuff and the artery; determining the model unknowns from the measured waveform; and determining blood pressure for the subject using the determined model.

Claims

1. A method for determining blood pressure for a subject using a sphygmomanometer having a cuff and a pressure sensor integrated therein, comprising:

measuring an oscillometric cuff pressure waveform of the subject using the sphygmomanometer, where the oscillometric cuff pressure waveform indicates the time evolution of the pressure inside the cuff during inflation and deflation of the cuff;

representing the measured waveform with a physical model, where the model accounts for a nonlinear relationship between a cross-sectional area of an artery and blood pressure;

determining unknowns of the physical model using the measured oscillometric cuff pressure waveform; and

determining blood pressure for the subject using the determined model.

2. The method of claim 1 wherein the model accounts for the cuff, the artery, including the nonlinear relationship, and coupling between the cuff and the artery.

3. The method of claim 2 wherein a portion of the model pertaining to the cuff accounts for a nonlinear relationship between the oscillometric cuff pressure and volume of air pumped into the cuff.

4. The method of claim 2 wherein the model of the coupling between the cuff and the artery ignores compressibility of arm tissue.

5. The method of claim 1 wherein the model has inputs of a blood pressure waveform and volume of air pumped into and out of the cuff and an output of the oscillometric cuff pressure waveform.

6. The method of claim 1 further comprises determining the unknowns of the model using a priori measurements on the cuff and the volume of air pumped into and out of the cuff.

7. The method of claim 6 further comprises determining the cross-sectional area of the artery from a priori measurements on the cuff and the volume of air pumped into and out of the cuff.

8. The method of claim 7 wherein determining the cross-sectional area of the artery further comprises representing the blood pressure waveform and the relationship between the cross-sectional area of an artery and blood pressure in terms of unknown parameters.

9. The method of claim 8 further comprises estimating the unknown parameters by optimally predicting the cross-sectional area of the artery.

10. The method of claim 9 further comprises determining a blood pressure waveform from the estimated parameters.

11. The method of claim 1 further comprises

measuring a blood volume waveform of the subject using a photoplethysmography;

and

determining the blood pressure of the subject based in part on the measured blood volume waveform.

12. The method of claim 7 wherein determining the cross-sectional area of the artery further comprises

detecting an envelope of a plot of the cross-sectional area of the artery in relation to negative oscillometric cuff pressure waveform;

and

shifting the envelope so that its peak derivative is at zero trans-mural pressure, thereby yielding the relationship between the cross-sectional area of an artery and blood pressure, wherein the model is non-parametric.

13. The method of claim 12 further comprises determining a blood pressure waveform from the cross-sectional area of the artery and the relationship between the cross-sectional area of an artery and blood pressure.

14. The method of claim 13 further comprises vertically shifting the blood pressure waveform so that mean of the blood pressure is equal to oscillometric cuff pressure at maximal cuff pressure oscillation.

15. The method of claim 7 further comprises

representing the relationship between the cross-sectional area of an artery and blood pressure with a parametric model;

detecting one or more envelopes of a plot of the cross-sectional area of the artery in relation to negative oscillometric cuff pressure waveform;

estimating parameters of the parametric model and one or more blood pressure values by fitting the parametric model to the envelope.

16. The method of claim 15 further comprises determining a blood pressure waveform from the cross-sectional area of the artery and the relationship between the cross-sectional area of an artery and blood pressure.

17. A method for determining blood pressure for a subject using a sphygmomanometer having a cuff and a pressure sensor integrated therein, comprising:

measuring an oscillometric cuff pressure waveform of the subject using the sphygmomanometer, where the oscillometric cuff pressure waveform indicates the time evolution of the pressure inside the cuff during inflation and deflation of the cuff;

representing the measured waveform in terms of a physical model, where the model accounts for a nonlinear relationship between a cross-sectional area of an artery and blood pressure, and a nonlinear relationship between the oscillometric cuff pressure and volume of air pumped into the cuff;

determining the cross-sectional area of the artery using the physical model and the measured oscillometric cuff pressure waveform;

determining parameters of the relationship between cross-sectional area of an artery and blood pressure from the determined waveform and the measured oscillometric cuff pressure waveform; and

determining blood pressure for the subject using the determined waveform and the determine relationship.

18. The method of claim 17 further comprises

representing the relationship between the cross-sectional area of an artery and blood pressure with a parametric model;

detecting one or more envelopes of a plot of the cross-sectional area of the artery in relation to negative oscillometric cuff pressure waveform;

estimating parameters of the parametric model and one or more blood pressure values by fitting the parametric model to the envelope.

19. The method of claim 18 further comprises determining a blood pressure waveform from the cross-sectional area of the artery and the relationship between the cross-sectional area of an artery and blood pressure.

20. A method for determining blood pressure for a subject using a sphygmomanometer having a cuff and a pressure sensor integrated therein, comprising:

measuring oscillometric cuff pressure waveform of the subject using the sphygmomanometer, where the oscillometric cuff pressure waveform indicates the time evolution of the pressure inside the cuff during inflation and deflation of the cuff;

representing the measured waveform in terms of a physical model, where the model accounts for a nonlinear relationship between a cross-sectional area of an artery and blood pressure, and a nonlinear relationship between the oscillometric cuff pressure and volume of air pumped into the cuff;

determining the cross-sectional area of the artery using the physical model and the measured oscillometric cuff pressure waveform;

determining non-parametrically the relationship between cross-sectional area of an artery and blood pressure from the determined waveform and the measured oscillometric cuff pressure waveform; and

determining blood pressure for the subject using the determined waveform and the determined relationship.

21. The method of claim 20 wherein determining the cross-sectional area of the artery further comprises

detecting an envelope of a plot of the cross-sectional area of the artery in relation to negative oscillometric cuff pressure waveform;

and

shifting the envelope so that its peak derivative is at zero trans-mural pressure, thereby yielding the relationship between the cross-sectional area of an artery and blood pressure, wherein the model is non-parametric.

22. The method of claim 21 further comprises determining a blood pressure waveform from the cross-sectional area of the artery and the relationship between the cross-sectional area of an artery and blood pressure.

23. The method of claim 22 further comprises vertically shifting the blood pressure waveform so that mean of the blood pressure is equal to oscillometric cuff pressure at maximal cuff pressure oscillation.