System and method for determining stroke volume of a patient

• US 10,448,851 B2
• Filed: 12/21/2015
• Issued: 10/22/2019
• Est. Priority Date: 09/11/2012
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Addison, Paul Stanley, Watson, James Nicholas
• Primary Examiner(s): Layno, Carl H
• Assistant Examiner(s): Ghand, Jennifer L
• Application Number:
  US14/977,301
• Publication Number:
  US 20160106322A1
• Time in Patent Office: 1,401 Days
• 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 method, comprising:

receiving a photoplethysmogram (PPG) signal from a single PPG sensor at a PPG monitor comprising a processor, wherein the PPG sensor is configured to be secured to a skin surface of a patient, and wherein the PPG sensor comprises one or more light sources configured to emit light into a tissue and one or more detectors configured to detect an amount of the light from the tissue, and wherein the PPG signal comprises a primary peak separated from a trailing peak by a dichrotic notch;

analyzing the PPG signal via the processor to determine an inverse gradient of an upslope of the primary peak of the PPG signal; and

calculating a stroke volume via the processor based on the inverse gradient of the upslope of the primary peak of the PPG signal.

2. The method of claim 1, wherein the PPG signal comprises a PPG waveform, and wherein analyzing the PPG signal comprises analyzing a contour of the PPG waveform along the upslope of the primary peak to identify the inverse gradient.

3. The method of claim 1, wherein analyzing the PPG signal comprises correlating the inverse gradient of the upslope of the primary peak of the PPG signal to a slope transit time of an initial pressure wave.

4. The method of claim 3, wherein correlating the inverse gradient of the upslope to a slope transit time comprises calculating the inverse gradient of the PPG signal as a function of effects of reflected waves of previous pulses.

5. The method of claim 1, wherein calculating the stroke volume comprises calculating the stroke volume based upon one or more empirically determined constants.

6. The method of claim 5, wherein the one or more empirically determined constants are determined through clinical examinations of the patient.

7. The method of claim 5, wherein the one or more empirically determined constants are derived from historical data related to the patient, wherein the historical data comprises patient demographic data, a body mass index, a height, a weight, or a combination thereof.

8. The method of claim 5, wherein the one or more empirically determined constants are derived from measured characteristics of the PPG signal, wherein the measured characteristics comprise a heat rate, a pulse transit time, a differential pulse transit time, or a combination thereof.

9. The method of claim 1, comprising calculating a heart rate based on a frequency of or a time interval between one or more primary peaks in the PPG signal.

10. The method of claim 9, comprising calculating a cardiac output based on the calculated stroke volume and the heart rate.

11. The method of claim 10, comprising displaying the calculated stroke volume, the heart rate, or the cardiac output on a display of the PPG monitor.

12. The method of claim 1, comprising triggering an alarm when the stroke volume exceeds a threshold, wherein the threshold is based on physiological conditions of the patient, and wherein the physiological conditions comprise an age, a weight, a height, a diagnosis, medications, treatments, or a combination thereof.

13. The method of claim 1, comprising:

measuring a gradient of the upslope of the primary peak, wherein the gradient is a fixed height change or an amplitude of the PPG signal; and

determining an actual gradient of the upslope of the primary peak from the measured gradient by using a scaling factor, an algorithm, a lookup table, or a combination thereof.

14. The method of claim 13, wherein the inverse gradient is the inverse of the measured gradient or the actual gradient.

15. A method, comprising:

receiving a photoplethysmogram (PPG) signal from a single PPG sensor at a PPG monitor comprising a processor, wherein the PPG sensor is configured to be secured to a skin surface of a patient, and wherein the PPG sensor comprises one or more light sources configured to emit light into a tissue and one or more detectors configured to detect an amount of the light from the tissue, and wherein the PPG signal comprises one or more primary peaks;

calculating a heart rate based on a frequency of or a time interval between the one or more primary peaks in the PPG signal;

determining an inverse gradient of an upstroke of a primary peak of the PPG signal;

calculating a stroke volume based at least in part on the inverse gradient;

calculating a cardiac output based at least in part on the stroke volume and the heart rate; and

displaying the cardiac output, the stroke volume, the heart rate, or a combination thereof, on a display.

16. The method of claim 15, wherein the PPG signal comprises a PPG waveform, and wherein analyzing the PPG signal comprises analyzing a contour of the PPG waveform along the upslope of the primary peak to identify the inverse gradient.

17. The method of claim 15, comprising calculating the stroke volume based at least in part on the inverse gradient of the PPG signal and one or more empirical constants.

18. The method of claim 17, wherein the one or more empirically determined constants comprise a calibration constant or the one or more empirically determined constants are derived from clinical examinations of the patient.