Method and system for cardiovascular system diagnosis

• US 7,771,364 B2
• Filed: 08/19/2008
• Issued: 08/10/2010
• Est. Priority Date: 01/27/2004
• Status: Expired due to Fees

• Current Assignee: Spirocor Ltd.
• Original Assignee: Spirocor Ltd.
• Inventors: Tal, Yoram, Arbel, Ronen, Ortenberg, Michael
• Primary Examiner(s): Nasser; Robert L
• Assistant Examiner(s): Natnithithadha; Navin
• Application Number:
  US12/194,139
• Publication Number:
  US 20090076399A1
• Time in Patent Office: 721 Days
• Field of Search: 600/481, 600/483, 600/484, 600500-503, 600/529, 600/300, 600/301
• US Class Current: 600/500
• 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 5/024 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 5/4035 Evaluating the autonomic nervous system
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

The present invention is directed to a method and system for monitoring function and/or diagnosing dysfunction of the cardiovascular system of a human subject. The method comprise measuring pulse wave signals of the subject during rapid excitation of the cardiovascular system, analyzing the measured signals and computing indicators reflecting a response to said excitation. The cardiovascular excitation preferably comprise a controlled breathing protocol characterized by a predefined frequency of breaths (e.g., about 0.1 Hz).

Claims

1. A method comprising:

measuring, by a sensing device, blood pulse wave signals of a subject during a periodic excitation of a cardiovascular system of the subject, wherein the periodic excitation is at an excitation frequency around 0.1 Hertz;

transforming, by a computational device, the blood pulse wave signals to a frequency domain representation by computing a power spectrum of the blood pulse wave signals;

extracting, by a computational device, a respiratory stress response (RSR) indicator associated with a respiratory peak of the frequency domain representation around the excitation frequency; and

evaluating the condition of the cardiovascular system of the subject based on the RSR indicator.

2. The method of claim 1, wherein the periodic excitation of the cardiovascular system is achieved by periodically applying pressure to an eyeball of the subject associated with the cardiovascular system.

3. The method of claim 1, wherein the periodic excitation of the cardiovascular system is achieved by periodically contracting extraocular muscles of the subject associated with the cardiovascular system.

4. The method of claim 1, wherein the periodic excitation of the cardiovascular system is achieved by periodically performing a Valsalva manoeuvre.

5. The method of claim 1, wherein the periodic excitation of the cardiovascular system is achieved by periodically performing a Muller manoeuvre.

6. The method of claim 1, wherein the periodic excitation of the cardiovascular system is breathing at the excitation frequency.

7. The method of claim 1, wherein the blood pulse wave signals are measured by a photoplethysmograph (PPG) sensor placed on a finger of the subject.

8. The method of claim 1, wherein the blood pulse wave signals are received from measurement of blood flow, blood volume or blood pressure of the subject.

9. The method of claim 1, wherein extracting the respiratory stress response (RSR) indicator comprises:

defining a first frequency range in the frequency domain representation around the excitation frequency, the first frequency range is delimited by a low boundary frequency below the excitation frequency and a high boundary frequency above the excitation; and

computing a first area parameter corresponding to an area delimited by a curve of the frequency domain representation within the first frequency range and a line connecting points on the curve that correspond to the low and high boundary frequencies, respectively.

10. The method of claim 9, wherein the low and high boundary frequencies are determined at points where the slope of the curve is smaller than a predefined value.

11. The method of claim 9, wherein extracting the respiratory stress response (RSR) indicator further comprises:

computing a second area parameter that corresponds to an entire area under the curve of the frequency domain representation within the first frequency range; and

computing the RSR indicator as the ratio between the first area parameter and the second area parameter.

12. The method of claim 9, wherein extracting the respiratory stress response (RSR) indicator further comprises:

defining a second frequency range in the frequency domain representation between zero and a cut-off frequency, wherein the cut-off frequency is higher than the a high boundary frequency of the first frequency range;

computing a third area parameter that corresponds to the entire area under the curve of the frequency domain representation within the second frequency range excluding the area associated with the first area parameter; and

computing the RSR indicator as the ratio between the first area parameter and the third area parameter.

13. The method of claim 12, wherein the cut-off frequency is at around 0.4 Hertz.