SYSTEM AND METHOD FOR DETERMINING STROKE VOLUME OF A PATIENT

• US 20140073962A1
• Filed: 09/11/2012
• Published: 03/13/2014
• Est. Priority Date: 09/11/2012
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Addison, Paul Stanley, Watson, James Nicholas
• Granted Patent: US 9,241,646 B2
• Time in Patent Office: Days
• US Class Current: 600/479
• 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 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/02427 Details of sensor
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: A61B 8/02 Measuring pulse or heart rate

Abstract

A PPG system for determining a stroke volume of a patient includes a PPG sensor configured to be secured to an anatomical portion of the patient. The PPG sensor is configured to sense a physiological characteristic of the patient. The PPG system may include a monitor operatively connected to the PPG sensor. The monitor receives a PPG signal from the PPG sensor. The monitor includes a pulse trending module determining a slope transit time of an upslope of a primary peak of the PPG signal. The pulse trending module determines a stroke volume of the patient as a function of the slope transit time.

Claims

1. A photoplethysmogram (PPG) system for determining a stroke volume of a patient, the PPG system comprising:

a PPG sensor configured to be secured to an anatomical portion of the patient, wherein the PPG sensor is configured to sense a physiological characteristic of the patient; and

a monitor operatively connected to the PPG sensor, the monitor receiving a PPG signal from the PPG sensor, wherein the PPG signal includes a primary peak separated from a trailing peak by a dichrotic notch, the monitor comprising a pulse trending module configured to determine a slope transit time of an upslope of the primary peak of the PPG signal, the pulse trending module configured to determine a stroke volume as a function of the slope transit time.

2. The PPG system of claim 1, wherein the slope transit time is calculated based upon an inverse of a gradient of the upslope of the primary peak of the PPG signal.

3. The PPG system of claim 1, wherein the slope transit time is calculated by the pulse trending module as a temporal gradient of the PPG signal.

4. The PPG system of claim 1, wherein the slope transit time is calculated by the pulse trending module as an inverse of a gradient of the upslope of the primary peak of the PPG signal.

5. The PPG system of claim 1, wherein the PPG signal forms a PPG waveform, the pulse trending module analyzing a contour of the PPG waveform along the upslope of the primary peak to identify a gradient of the contour, the pulse trending module calculating the slope transit time as the inverse of the gradient.

6. The PPG system of claim 1, wherein the PPG signal forms a PPG waveform, the pulse trending module analyzing a contour of the PPG waveform along the upslope of the primary peak to identify a temporal gradient of the contour, the pulse trending module calculating the slope transit time as a function of the temporal gradient.

7. The PPG system of claim 1, wherein the PPG signal forms a PPG waveform, the pulse trending module analyzing a contour of the PPG waveform along the upslope of the primary peak to identify at least one waveform characteristic thereof, the waveform characteristic comprising at least one of an amplitude (A) of the contour, a gradient (m) of the contour and a temporal gradient (k) of the contour, the pulse trending module calculating the stroke volume based upon at least one of the ratios of m=A/STT, k=1/m and k=STT.

8. The PPG system of claim 1, wherein the pulse trending module calculates stroke volume based upon empirically determined constants.

9. The PPG system of claim 1, wherein the pulse trending module uses a calibration constant to determine the stroke volume.

10. The PPG system of claim 1, wherein the monitor displays an output of the stroke volume on a display.

11. A method of determining a stroke volume of a patient from a photoplethysmogram (PPG) system, the method comprising:

securing a PPG sensor to an anatomical portion of the patient;

sensing a physiological characteristic of the patient with the PPG sensor;

receiving a PPG signal from the sensor at a monitor comprising a pulse trending module, wherein the PPG signal includes a primary peak separated from a trailing peak by a dichrotic notch;

analyzing the PPG signal at the pulse trending module to determine a slope transit time of an upslope of the primary peak of the PPG signal; and

calculating a stroke volume at the pulse trending module of the patient based on the slope transit time of the upslope of the primary peak of the PPG signal.

12. The method of claim 11, wherein the analyzing operation comprises correlating the slope transit time of the upslope of the primary peak of the PPG signal to a slope transit time of an initial pressure wave.

13. The method of claim 11, wherein the analyzing operation comprises analyzing a contour of the PPG waveform along the upslope of the primary peak to identify at least one waveform characteristic thereof, the waveform characteristic comprising at least one of an amplitude (A) of the contour, a gradient (m) of the contour and a temporal gradient (k) of the contour, the pulse trending module calculating the slope transit time based upon at least one of the ratios of m=A/STT, k=1/m and k=STT.

14. The method of claim 11, wherein the correlating operation comprises calculating the slope transit time of the PPG signal as a function of effects of reflected waves of previous pulses based on at least one of wave periods, pulse periods, pulse transit times, and shapes of the previous waveforms.

15. The method of claim 11, wherein the calculating operation comprises calculating the stroke volume based upon the slope transit time and empirically determined constants.

16. A tangible and non-transitory computer readable medium that includes one or more sets of instructions configured to direct a computer to:

receive a photoplethysmogram (PPG) signal from a PPG sensor secured to an anatomical portion of a patient, wherein the PPG signal includes a primary peak separated from a trailing peak by a dichrotic notch;

determine a slope transit time of an upslope of the primary peak of the PPG signal; and

calculate a stroke volume of the patient based on the slope transit time of the upslope of the primary peak of the PPG signal.

17. The tangible and non-transitory computer readable medium of claim 16, further configured to correlate the slope transit time of the upslope of the primary peak of the PPG signal to a slope transit time of an initial pressure wave.

18. The tangible and non-transitory computer readable medium of claim 16, further configured to:

analyze a contour of the PPG waveform along the upslope of the primary peak to identify at least one waveform characteristic thereof, the waveform characteristic comprising at least one of an amplitude (A) of the contour, a gradient (m) of the contour and a temporal gradient (k) of the contour, and

calculate the slope transit time based upon at least one of the ratios of m=A/STT, k=1/m and k=STT.

19. The tangible and non-transitory computer readable medium of claim 16, further configured to calculate the slope transit time of the PPG signal as a function of effects of reflected waves of previous pulses based on at least one of wave periods, pulse periods, pulse transit times, and shapes of the previous waveforms.

20. The tangible and non-transitory computer readable medium of claim 16, further configured to calculate the stroke volume based upon the slope transit time and empirically determined constants.