SYSTEM AND METHOD FOR LOW POWER SAMPLING OF PLETHYSMOGRAPH SIGNALS

• US 20150133801A1
• Filed: 11/13/2013
• Published: 05/14/2015
• Est. Priority Date: 11/13/2013
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Soro, Stanislava, Hasan, SM Shajedul, Karp, Jason Harris
• Granted Patent: US 9,655,533 B2
• Time in Patent Office: Days
• US Class Current: 600/507
• 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 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• 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 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence

Abstract

A method for generating a sampled plethysmograph data, includes measuring a plethysmograph waveform indicative of a first cardiac cycle and a second cardiac cycle, each cycle including a systolic waveform and a diastolic waveform. The method further includes estimating a first start time and a first duration for the systolic waveform of the first cardiac cycle and computing a plurality of amplitudes at a plurality of time instants for the first duration. The method further includes determining a second start time and a second duration of the systolic waveform of the second cardiac cycle. The method also includes assigning the second cardiac cycle, the second start time, and the second duration to the first cardiac cycle, the first start time, and the first duration respectively. The method further includes iteratively performing the steps of measuring, estimating, computing, determining and assigning for the plurality of cardiac cycles acquired sequentially in time.

Claims

1. A method, comprising:

(I) measuring a plethysmograph waveform indicative of a plurality of cardiac cycles, wherein the plethysmograph waveform includes a systolic waveform and a diastolic waveform, corresponding to each cardiac cycle;

(II) estimating a first start time and a first duration for the systolic waveform of a first cardiac cycle, based on at least one cardiac cycle from the plurality of cardiac cycles;

(III) computing a plurality of amplitudes at a plurality of time instants for the first duration of the systolic waveform of the first cardiac cycle;

(IV) determining a second start time and a second duration of the systolic waveform of a second cardiac cycle from the plurality of cardiac cycles based on the plurality of amplitudes;

wherein the second cardiac cycle is acquired after the first cardiac cycle in time sequence;

(V) assigning the second cardiac cycle, the second start time, and the second duration to the first cardiac cycle, the first start time, and the first duration respectively; and

iteratively performing (III), (IV), (V) for the plurality of cardiac cycles acquired sequentially in time to generate a sampled plethysmograph data.

2. The method of claim 1, further comprising determining an average value of the plurality of cardiac cycles and estimating the first start time and the first duration based on the average value.

3. The method of claim 1, wherein the first duration comprises a systolic rise duration, a first offset duration before the systolic rise duration and a second offset duration after the systolic rise duration.

4. The method of claim 3, wherein the determining further comprises identifying a portion of the first cardiac cycle, which occurs within the first duration.

5. The method of claim 4, wherein the identifying comprises determining a peak value of the plurality of amplitudes.

6. The method of claim 5, wherein the determining further comprises assigning a first value less than the first duration, to the second duration, when the identified portion of the first cardiac cycle occurs within the systolic rise duration.

7. The method of claim 6, wherein the determining further comprises assigning a second value greater than the first duration, to the second duration, when the identified portion of the first cardiac cycle occurs within and beyond the systolic rise duration.

8. The method of claim 7, further comprising determining an entire duration of the first cardiac cycle.

9. The method of claim 8, wherein the determining further comprises assigning a third value equal to the entire duration, to the second duration, when the identified portion of the first cardiac cycle is the diastolic waveform.

10. The method of claim 3, wherein the determining comprises determining the second start time based on one time instant among the plurality of time instants, corresponding to a start time of the systolic waveform of the first cardiac cycle.

11. A system comprising:

a sensor configured to measure a plethysmograph waveform indicative of a plurality of cardiac cycles, wherein the plethysmograph waveform includes a systolic waveform and a diastolic waveform corresponding to each cardiac cycle;

a timing module communicatively coupled to the sensor and configured to estimate a first start time and a first duration for the systolic waveform of a first cardiac cycle, based on at least one cardiac cycle from the plurality of cardiac cycles;

a sampling module communicatively coupled to the timing module and the sensor, wherein the sampling module is configured to compute a plurality of amplitudes at a plurality of time instants for the first duration of the systolic waveform of the first cardiac cycle; and

a processing module communicatively coupled to the sampling module and the timing module, wherein the processing module is configured to;

(I) receive the plurality of amplitudes from the sampling module;

(II) determine a second start time and a second duration of the systolic waveform of a second cardiac cycle from the plurality of cardiac cycles, based on the plurality of amplitudes;

wherein the second cardiac cycle is generated after the first cardiac cycle in time sequence;

(III) assign the second cardiac cycle, the second start time, and the second duration to the first cardiac cycle, the first start time, and the first duration respectively; and

iteratively perform (I), (II), (III) for the plurality of cardiac cycles generated sequentially in time to capture a sampled plethysmograph data.

12. The system of claim 11, wherein timing module is further configured to determine an average value of the plurality of cardiac cycle and estimate the first start time and the first duration based on the average value.

13. The system of claim 12, wherein the processing module is configured to identify a portion of the first cardiac cycle, which occurs within the first duration.

14. The system of claim 13, wherein the processing module is further configured to determine a peak value of the plurality of amplitudes.

15. The system of claim 14, wherein the processing module is further configured to assign a first value less than the first duration, to the second duration, when the identified portion of the first cardiac cycle occurs within a systolic rise duration of the first duration.

16. The system of claim 15, wherein the processing module is configured to assign a second value greater than the first duration, to the second duration, when the identified portion of the first cardiac cycle occurs within and beyond the systolic rise duration.

17. The system of claim 16, wherein the processing module is configured to determine an entire duration of the first cardiac cycle.

18. The system of claim 17, wherein the processing module is configured to assign a third value equal to the entire duration, to the second duration, when the identified portion of the first cardiac cycle is the diastolic waveform.

19. The system of claim 15, wherein the processing module is configured to determine the second start time based on one time instant among the plurality of time instants, corresponding to a start time of the systolic waveform of the first cardiac cycle.

20. The system of claim 11, further comprising a reconstruction module communicatively coupled to the sampling module configured to generate a plurality of diastolic amplitudes corresponding to the diastolic waveform of the first cardiac cycle.

21. A method comprising:

(I) generating a plethysmograph waveform indicative of a plurality of cardiac cycles, wherein the plethysmograph waveform includes a systolic waveform and a diastolic waveform, corresponding to each cardiac cycle;

(II) estimating a first start time and a first duration for the systolic waveform of a first cardiac cycle, based on at least one cardiac cycle from the plurality of cardiac cycles;

(III) computing a plurality of amplitudes at a plurality of time instants for the first duration of the systolic waveform of the first cardiac cycle;

(IV) determining a second start time and a second duration of the systolic waveform of a second cardiac cycle from the plurality of cardiac cycles based on the first plurality of amplitudes;

wherein the second cardiac cycle is generated after the first cardiac cycle in time sequence;

(V) reconstructing a plurality of diastolic amplitudes corresponding to the diastolic waveform of the first cardiac cycle based on the plurality of amplitudes;

(VI) assigning the second cardiac cycle, the second start time, and the second duration to the first cardiac cycle, the first start time, and the first duration respectively; and

iteratively performing (III), (IV), (V), (VI) for the plurality of cardiac cycles generated sequentially in time to generate a sampled plethysmograph data.

22. The method of claim 21, wherein the reconstructing comprises determining the plurality of diastolic amplitudes using a diastolic template.

23. The method of claim 21, wherein the reconstructing comprises determining the plurality of diastolic amplitudes using a polynomial interpolation technique.

24. A non-transitory computer readable medium encoded with a program to instruct at least one processor based device to:

(I) generate a plethysmograph waveform indicative of a plurality of cardiac cycles, wherein the plethysmograph waveform includes a systolic waveform and a diastolic waveform, corresponding to each cardiac cycle;

(II) estimate a first start time and a first duration for the systolic waveform of a first cardiac cycle, based on at least one cardiac cycle from the plurality of cardiac cycles;

(III) compute a plurality of amplitudes at a plurality of time instants for the first duration of the systolic waveform of the first cardiac cycle;

(IV) determine a second start time and a second duration of the systolic waveform of a second cardiac cycle from the plurality of cardiac cycles based on the plurality of amplitudes;

wherein the second cardiac cycle is generated after the first cardiac cycle in time sequence;

(V) assign the second cardiac cycle, the second start time, and the second duration to the first cardiac cycle, the first start time, and the first duration respectively; and

iteratively perform (III). (IV), (V) for the plurality of cardiac cycles generated sequentially in time to generate a sampled plethysmograph data.