SYSTEM AND METHOD FOR DETERMINING STROKE VOLUME OF AN INDIVIDUAL

• US 20140066785A1
• Filed: 09/06/2012
• Published: 03/06/2014
• Est. Priority Date: 09/06/2012
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Watson, James Nicholas, Addison, Paul Stanley
• Granted Patent: US 9,357,937 B2
• Time in Patent Office: Days
• US Class Current: 600/479
• CPC Class Codes: A61B 5/0265 using electromagnetic means, e.g. electromagnetic flowmeter
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• 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 5/0295 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

Abstract

A system for determining stroke volume of an individual. The system includes a skew-determining module that is configured to calculate a first derivative of photoplethysmogram (PPG) signals of the individual. The first derivative forms a derivative waveform. The skew-determining module is configured to determine a skew metric of the first derivative, wherein the skew metric is indicative of a morphology of at least one pulse wave detected from blood flow of the individual in the derivative waveform. The system also includes an analysis module that is configured to determine a stroke volume of the individual. The stroke volume is a function of the skew metric of the first derivative.

Claims

1. A system for determining stroke volume of an individual, the system comprising:

a skew-determining module configured to calculate a first derivative of photoplethysmogram (PPG) signals of the individual, the first derivative forming a derivative waveform, the skew-determining module configured to determine a skew metric of the first derivative, wherein the skew metric is indicative of a morphology of at least one pulse wave detected from blood flow of the individual in the derivative waveform; and

an analysis module configured to determine a stroke volume of the individual, the stroke volume being a function of the skew metric of the first derivative.

2. The system of claim 1, wherein the skew metric is determined for each pulse wave or from a pulse-ensemble average that is based on a plurality of the pulse waves.

3. The system of claim 1, further comprising an identification module that identifies individual pulse waves from at least one of the derivative waveform or a PPG waveform that is formed by the PPG signals, wherein the pulse waves are approximately defined from a first upstroke to a second, adjacent upstroke in the corresponding waveform, each the first and second upstrokes corresponding to an increase in blood volume caused by a heartbeat.

4. The system of claim 1, wherein the skew metric is determined using at least one of Pearson'"'"'s skewness, Fisher-Pearson standardized moment coefficient, quartile-based measurements, distance skewness, Cyhelsky'"'"'s skewness coefficients, or a morphological metric of the derivative waveform.

5. The system of claim 1, further comprising a PPG sensor that is operably coupled to the monitor.

6. The system of claim 1, wherein the pulse waves are pulse waves detected from a finger of the individual.

7. The system of claim 1, wherein the stroke volume is based on at least one of a constant or a coefficient, the at least one of the constant or the coefficient being determined by observed historical data and/or characteristics of the PPG signals.

8. The system of claim 1, wherein the skew metric is a calculated value that is indicative of a distribution of values in a data set that includes the data points that define the pulse wave in the derivative waveform.

9. A method for determining stroke volume of an individual, the method comprising:

acquiring photoplethysmogram (PPG) signals of the individual, the PPG signals corresponding to pulse waves detected from blood flow of the individual;

calculating a first derivative of the PPG signals, the first derivative forming a derivative waveform;

determining a skew metric of the first derivative, wherein the skew metric is indicative of a morphology of at least one of the pulse waves in the derivative waveform; and

determining a stroke volume of the individual, the stroke volume being a function of the skew metric of the first derivative.

10. The method of claim 9, wherein the determining the skew metric of the first derivative includes determining the skew metric for each pulse wave or for a pulse-ensemble average that is based on a plurality of the pulse waves.

11. The method of claim 10, wherein the pulse waves are approximately defined from a first upstroke to a second, adjacent upstroke, each the first and second upstrokes corresponding to an increase in blood volume caused by a heart beat.

12. The method of claim 9, wherein the pulse waves are pulse waves detected from a finger of the individual.

13. The method of claim 9, wherein the determining the skew metric of the first derivative includes determining at least one of Pearson'"'"'s skewness, Fisher-Pearson standardized moment coefficient, quartile-based measurements, distance skewness, Cyhelsky'"'"'s skewness coefficients, or a morphological metric of the derivative waveform.

14. The method of claim 9, wherein the stroke volume is based on at least one of a constant or a coefficient, the at least one of the constant or the coefficient being determined by observed historical data and/or characteristics of the PPG signals.

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

acquire photoplethysmogram (PPG) signals of the individual, the PPG signals corresponding to pulse waves detected from blood flow of the individual;

calculate a first derivative of the PPG signals, the first derivative forming a derivative waveform;

determine a skew metric of the first derivative, wherein the skew metric is indicative of a morphology of at least one of the pulse waves in the derivative waveform; and

determine a stroke volume of the individual, the stroke volume being a function of the skew metric of the first derivative.

16. The computer readable medium of claim 15, wherein the instructions direct the monitor to determine the skew metric for each pulse wave or from a pulse-ensemble average that is based on a plurality of the pulse waves.

17. The computer readable medium of claim 16, wherein the pulse waves are approximately defined from a first upstroke to a second, adjacent upstroke, each the first and second upstrokes correspond to an increase in blood volume caused by a heart beat.

18. The computer readable medium of claim 15, wherein the pulse waves are pulse waves detected from a finger of the individual.

19. The computer readable medium of claim 15, wherein the instructions direct the monitor to determine the skew metric using at least one of Pearson'"'"'s skewness, Fisher-Pearson standardized moment coefficient, quartile-based measurements, distance skewness, Cyhelsky'"'"'s skewness coefficients, or a morphological metric of the derivative waveform.

20. The computer readable medium of claim 15, wherein the stroke volume is based on at least one of a constant or a coefficient, the at least one of the constant or the coefficient being determined by observed historical data and/or characteristics of the PPG signals.