Methods and systems for distal recording of phonocardiographic signals

• US 20030220577A1
• Filed: 04/18/2003
• Published: 11/27/2003
• Est. Priority Date: 04/19/2002
• Status: Active Grant

• Current Assignee: Omron Healthcare Company Limited (Omron Corporation)
• Original Assignee: Southwest Research Institute
• Inventors: Canady, Larry D. Jr., Honeyager, Kevin S., Bartels, Keith A.
• Granted Patent: US 7,137,955 B2
• Time in Patent Office: Days
• US Class Current: 600/510
• 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 5/02125 of pulse wave propagation time
• 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 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/6817 Ear canal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 7/023 for introduction into the body, e.g. into the oesophagus oesophageal ECG probes A61B5/285
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R

Abstract

Methods and systems for determining cardiovascular parameters of a patient. In an exemplary embodiment, the method includes placing a phonocardiogram sensor on a patient'"'"'s body at a first distal location to the heart, and a blood-pressure waveform sensor at a second distal location to the heart. Then, a first set and a second set of waveforms is obtained from the phonocardiogram sensor and the blood-pressure waveform sensor, respectively. A signal processing or conditioning operation may optionally be performed using the first and second sets of waveforms. Then, a time delay between a dicrotic notch signal and an S2 signal is determined. A blood pressure pulse transit time value is calculated by adding S2D, representing a time delay between a patient'"'"'s heart valve closure time and an arrival time of the S2 signal at the first distal location, to the time delay between a dicrotic notch signal and an S2 signal. Cardiovascular parameters are then determined using the determined blood pressure pulse transit time and at least one physical parameter representative of a arterial distance between a location of the aortic valve and a location of the blood-pressure waveform sensor.

Claims

1. A method to determine a S2D value representing a time delay between a patient'"'"'s heart valve closure and an arrival of a patient'"'"'s S2 heart sound at a distal location to the heart, the method comprising:

placing a first phonocardiogram sensor on a patient'"'"'s chest;

placing a second phonocardiogram sensor at the distal location to the heart;

obtaining a first set of phonocardiogram signals from the first phonocardiogram sensor;

obtaining a second set of phonocardiogram signals from the second phonocardiogram sensor;

performing a signal processing or conditioning operation using the first and second sets of phonocardiogram signals; and

determining the time delay based on results obtained from the signal processing or conditioning operation.

2. The method according to claim 1, wherein performing a signal processing or conditioning operation comprises determining a patient'"'"'s individual heart cycles.

3. The method according to claim 2, wherein determining a patient'"'"'s individual heart cycles comprises determining a delimiter in the patient'"'"'s individual heart cycles.

4. The method according to claim 3, wherein determining a delimiter of heart cycles comprises determining an R-wave using a first set of electrocardiogram signals obtained from at least one electrocardiogram sensor positioned on the patient'"'"'s body.

5. The method according to claim 3, wherein determining a delimiter of heart cycles comprises determining an S2 signal, representative of a second heart sound associated with closure of the heart valves, from the first set of phonocardiogram signals.

6. The method according to claim 5, wherein performing a signal processing or conditioning operation includes using dicrotic notch of arterial blood pressure waveform as a trigger.

7. The method according to claim 1, wherein the distal location is a patient'"'"'s elbow.

8. The method according to claim 1, wherein placing the second phonocardiogram sensor at the distal location comprises placing the second phonocardiogram sensor on a bone or a tissue at the distal location.

9. The method according to claim 1, wherein performing a signal processing or conditioning operation comprises one or more of performing an ensemble averaging operation, using a bandpass filter, and determining a stable detection point on a distal S2 signal.

10. A method for determining cardiovascular parameters of a patient, the method comprising:

placing a phonocardiogram sensor on a patient'"'"'s body at a first distal location to the heart;

placing a blood-pressure waveform sensor at a second distal location to the heart;

obtaining a first set of waveforms from the phonocardiogram sensor;

obtaining a second set of waveforms from the blood-pressure waveform sensor;

performing a signal processing or conditioning operation using the first and second sets of waveforms;

determining a time delay between a dicrotic notch signal and an S2 signal;

determining a blood pressure pulse transit time value by adding S2D, representing a time delay between a patient'"'"'s heart valve closure time and an arrival time of the S2 signal at the first distal location, to the time delay between a dicrotic notch signal and the S2 signal; and

determining cardiovascular parameters of a patient using the determined blood pressure pulse transit time and at least one physical parameter representative of a arterial distance between a location of aortic valve of the heart and a location of the blood-pressure waveform sensor.

11. The method according to claim 10, wherein cardiovascular parameters include blood pressure-wave velocity, a patient'"'"'s heart isovolumetric contraction period or the like.

12. The method according to claim 10, wherein performing a signal processing or conditioning operation comprises one or more of performing an ensemble averaging operation, performing a processing using a bandpass filter, and performing a processing to determine a stable detection point on a distal S2 signal.

13. A method for determining a delay time, DT, between a distal S2 signal and dicrotic notch signal for a patient, the method comprising:

placing a phonocardiogram sensor on a patient'"'"'s body at a first distal location to the heart;

placing a blood-pressure waveform sensor at a second location on the patient'"'"'s body;

obtaining a first set of waveforms from the distal phonocardiogram sensor;

obtaining a second set of waveforms from the blood-pressure waveform sensor; and

determining a delay time DT between a dicrotic notch signal from the blood-pressure waveform signal and an S2 signal from distal phonocardiogram sensor.

14. The method according to claim 13 further comprising performing a signal processing or conditioning operation of at least one of the first and second sets of waveforms.

15. The method according to claim 14 wherein performing a signal processing or conditioning operation comprises one or more of performing an ensemble averaging operation, performing a processing using a bandpass filter, and performing a processing to determine a stable detection point on a distal S2 signal.

16. A method for determining a patient'"'"'s cardiovascular parameters, comprising:

determining a pulse wave velocity index according to the process of claim 13.

17. A method for determining a corrected blood pressure pulse transit time value for a patient, the method comprising:

placing a phonocardiogram sensor on a patient'"'"'s body at a first distal location to the heart;

placing a blood-pressure waveform sensor at a distal location on the patient'"'"'s body;

obtaining a first set of waveforms from the phonocardiogram sensor;

obtaining a second set of waveforms from the blood-pressure waveform sensor;

performing a signal processing or conditioning operation using the first and second sets of waveforms; and

determining a time delay between a dicrotic notch signal and an S2 signal;

determining a corrected blood pressure pulse transit time value by adding S2D, representing a time delay between a patient'"'"'s heart valve closure time and an arrival time of the S2 signal at the first distal location, to the time delay between a dicrotic notch signal and an S2 signal.

18. The method according to claim 17 wherein performing a signal processing or conditioning operation comprises one or more of performing an ensemble averaging operation, performing a processing using a bandpass filter, and performing a processing to determine a stable detection point on a distal S2 signal.

19. A system for determining cardiovascular parameters of a patient, the system comprising:

a signal acquisition and processing device;

a blood pressure waveform measuring device coupled to the signal acquisition and processing device; and

at least one phonocardiogram (PCG) sensor coupled to the signal acquisition and processing device.

20. The system according to claim 19, wherein the signal acquisition and processing device includes a display device.

21. The system according to claim 19 further comprising at least one PCG sensor coupled to the signal acquisition and processing device.

22. The system according to claim 19, wherein the blood pressure waveform measuring device includes a blood pressure cuff device.

23. The system according to claim 19, wherein the blood pressure waveform measuring device includes an arterial tonometer.