Method and apparatus for continuous assessment of a cardiovascular parameter using the arterial pulse pressure propagation time and waveform

• US 20080033305A1
• Filed: 11/06/2006
• Published: 02/07/2008
• Est. Priority Date: 07/13/2006
• Status: Active Grant

• Current Assignee: Edwards Lifesciences Corporation
• Original Assignee: Edwards Lifesciences Corporation
• Inventors: Roteliuk, Luchy D., Mooney, Charles R., Hatib, Feras S.
• Granted Patent: US 8,905,939 B2
• Time in Patent Office: Days
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• 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 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 8/04 Measuring blood pressure
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/488 involving Doppler signals

Abstract

A method and apparatus for determining a cardiovascular parameter including receiving an input signal corresponding to an arterial blood pressure measurement over an interval that covers at least one cardiac cycle, determining a propagation time of the input signal, determining at least one statistical moment of the input signal, and determining an estimate of the cardiovascular parameter using the propagation time and the at least one statistical moment.

Claims

1. A method for determining a cardiovascular parameter comprising:

receiving an input signal corresponding to an arterial blood pressure measurement over an interval that covers at least one cardiac cycle;

determining a propagation time of the input signal; and

determining an estimate of the cardiovascular parameter using the propagation time.

2. The method as defined in claim 1 further comprising determining at least one statistical moment of the input signal.

3. The method as defined in claim 2 wherein the step of determining an estimate of the cardiovascular parameter using the propagation time includes determining an estimate of the cardiovascular parameter using the at least one statistical moment.

4. The method as defined in claim 2 wherein the at least one statistical moment of the input signal is selected from a group consisting of a standard deviation of the input signal and a statistical moment having an order greater than two, the kurtosis of the input signal and the skeweness of the input signal.

5. The method as defined in claim 1 wherein the cardiovascular parameter is selected from a group consisting of arterial compliance, vascular resistance, cardiac output and stroke volume.

6. The method as defined in claim 1 wherein the step of determining a propagation time of the input signal includes determining a transit time between a reference signal detected near a heart of a subject and a peripheral arterial signal detected near an artery of the subject.

7. The method as defined in claim 6 wherein the reference signal is selected from a group consisting of an electrocardiogram measurement, a central aortic pressure measurement, a transthoracic bioimpedance measurement and a Doppler ultrasound blood velocity measurement.

8. The method as defined in claim 6 wherein the peripheral arterial signal is selected from a group consisting of an arterial blood pressure measurement, an optical oximetry measurement that measures the oxygen saturation of the blood of the subject, a peripheral bioimpedance measurement and a Doppler ultrasound blood velocity measurement.

9. The method as defined in claim 1 wherein determining an estimate of the cardiovascular parameter using the propagation time also includes using a standard deviation of the input signal to determine an estimate of the cardiovascular parameter.

10. The method as defined in claim 1 further comprising receiving an anthropometric parameter of the subject.

11. The method as defined in claim 10 wherein determining an estimate of the cardiovascular parameter using the propagation time also includes using the anthropometric parameter to determine an estimate of the cardiovascular parameter.

12. The method as defined in claim 10 further comprising estimating an arterial compliance value using the propagation time and the anthropometric parameter.

13. The method as defined in claim 12 further comprising estimating a stroke volume using the arterial compliance value and a standard deviation of the input signal.

14. The method as defined in claim 13 further comprising:

receiving a heart rate measurement of a subject; and

estimating cardiac output using the heart rate measurement and the stroke volume.

15. The method as defined in claim 14 further comprising estimating cardiac output using the arterial compliance and the standard deviation.

16. The method as defined in claim 15 further comprising:

receiving a calibration cardiac output value; and

calculating a calibration constant as a quotient between the calibration cardiac output estimate and the product of the heart rate, the arterial compliance and the standard deviation.

17. The method as defined in claim 12 wherein estimating an arterial compliance value further comprises:

determining an approximating function relating to a plurality of reference measurements to arterial compliance, wherein the approximating function is a function of the propagation time of the input signal and the anthropometric parameter; and

estimating the arterial compliance value of the subject by evaluating the approximating function with the propagation time of the input signal and the anthropometric parameter.

18. The method as defined in claim 1 further comprising:

calculating a component propagation time value for each of the plurality of cardiac cycles;

computing a composite propagation time value as an average of the component propagation time values; and

using the composite propagation time value in calculating an estimate of the cardiovascular parameter.

19. An apparatus for determining a cardiovascular parameter comprising:

a processing unit to;

receive an input signal corresponding to an arterial blood pressure measurement over an interval that covers at least one cardiac cycle;

determine a propagation time of the input signal; and

determine an estimate of the cardiovascular parameter using the propagation time.

20. The apparatus as defined in claim 19 wherein the processing unit determines at least one statistical moment of the input signal.

21. The apparatus as defined in claim 20 wherein the processing unit determines an estimate of the cardiovascular parameter using the at least one statistical moment.

22. The apparatus as defined in claim 20 wherein the at least one statistical moment of the input signal is selected from a group consisting of a statistical moment having an order greater than two, the kurtosis of the input signal, the skeweness of the input signal and a standard deviation of the input signal.

23. The apparatus as defined in claim 19 wherein the cardiovascular parameter is selected from a group consisting of arterial compliance, vascular resistance, cardiac output and stroke volume.

24. The apparatus as defined in claim 19 wherein the processing unit determines a propagation time of the input signal by determining a transit time between a reference signal detected near a heart of a subject and a peripheral arterial signal detected near an artery of the subject.

25. The apparatus as defined in claim 24 wherein the reference signal is selected from a group consisting of an electro-cardiogram measurement, a central aortic pressure measurement, a transthoracic bioimpedance measurement and a Doppler ultrasound blood velocity measurement.

26. The apparatus as defined in claim 24 wherein the peripheral arterial signal is selected from a group consisting of an arterial blood pressure measurement, an optical oximetry measurement that measures the oxygen saturation of the blood of the subject, a peripheral bioimpedance measurement and a Doppler ultrasound blood velocity measurement.

27. The apparatus as defined in claim 19 wherein the processing unit determines an estimate of the cardiovascular parameter using a standard deviation of the input signal.

28. The apparatus as defined in claim 19 wherein the processing unit receives an anthropometric parameter of the subject.

29. The apparatus as defined in claim 28 wherein the processing unit determines an estimate of the cardiovascular parameter using the propagation time and the anthropometric parameter.

30. The apparatus as defined in claim 28 wherein the processing unit estimates an arterial compliance value using the propagation time and the anthropometric parameter.

31. The apparatus as defined in claim 30 further comprising estimating a stroke volume using the arterial compliance value and a standard deviation of the input signal.

32. The apparatus as defined in claim 31 further comprising:

receiving a heart rate measurement of a subject; and

estimating cardiac output using the heart rate measurement and the stroke volume.

33. The apparatus as defined in claim 32 further comprising estimating cardiac output using the arterial compliance and the standard deviation.

34. The apparatus as defined in claim 33 further comprising:

receiving a calibration cardiac output value; and

calculating a calibration constant as a quotient between the calibration cardiac output estimate and the product of the heart rate, the arterial compliance and the standard deviation.

35. The apparatus as defined in claim 29 wherein estimating an arterial compliance value further comprises:

determining an approximating function relating to a plurality of reference measurements to arterial compliance, wherein the approximating function is a function of the propagation time of the input signal and the anthropometric parameter; and

estimating the arterial compliance value of the subject by evaluating the approximating function with the propagation time of the input signal and the anthropometric parameter.

36. The method as defined in claim 19 further comprising:

calculating a component propagation time value for each of the plurality of cardiac cycles;

computing a composite propagation time value as an average of the component propagation time values; and

using the composite propagation time value in calculating an estimate of the cardiovascular parameter.

37. A machine-readable medium that provides instructions, which when executed by a processor, cause the processor to determining a cardiovascular parameter comprising:

receiving an input signal corresponding to an arterial blood pressure measurement over an interval that covers at least one cardiac cycle;

determining a propagation time of the input signal; and

determining an estimate of the cardiovascular parameter using the propagation time.