Real-time measurement of ventricular stroke volume variations by continuous arterial pulse contour analysis

• US 20050187481A1
• Filed: 03/22/2005
• Published: 08/25/2005
• Est. Priority Date: 12/05/2003
• Status: Active Grant

• Current Assignee: Edwards Lifesciences Corporation
• Original Assignee: Edwards Lifesciences Corporation
• Inventors: Roteliuk, Luchy, Hatib, Feras
• Granted Patent: US 7,422,562 B2
• Time in Patent Office: Days
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02 Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
• 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 5/0205 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 5/02108 from analysis of pulse wave characteristics
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• 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 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]

Abstract

Ventricular stroke volume variation (SVV) is estimated as a function of the standard deviation of arterial blood pressure value measured over each of at least two cardiac cycles, preferably over each of the cardiac cycles in a computation interval covering a full respiratory cycle. In one embodiment, maximum and minimum standard deviation values are determined over the computation interval. SVV is then estimated proportional to the ratio of the difference between the maximum and minimum standard deviation values and the mean of the standard deviation values. In another embodiment, SVV is then estimated proportional to the ratio of the standard deviation of the standard deviation values and the mean standard deviation over the entire computation interval. A pre-processing arrangement for improving reliability of estimates of more general cardiac or hemodynamic parameters is also disclosed and involves smoothing with an approximating function, and sampling and low-pass filtering at an adjustable rate.

Claims

1. A method for determining a cardiac parameter equal to or derivable from cardiac stroke volume variation (SVV) comprising:

inputting a waveform data set corresponding to arterial blood pressure over a computation interval that covers at least two cardiac cycles;

calculating a standard deviation value for the waveform data set over each cardiac cycle; and

calculating an estimate of the SVV as a function of the standard deviation values.

2. A method as in claim 1, further comprising:

over the computation interval, determining maximum and minimum standard deviation values; and

calculating the estimate of the SVV as a function of the maximum and minimum standard deviation values.

3. A method as in claim 2, further comprising:

over the computation interval, computing a mean standard deviation value; and

calculating the estimate of the SVV to be proportional to the difference between the maximum and minimum standard deviation values relative to the mean standard deviation value.

4. A method as in claim 1, further comprising:

detecting the boundaries of respiratory cycles; and

setting the computation interval to be at least one respiratory cycle.

5. A method as in claim 4, further comprising:

computing the standard deviation of the standard deviation values over the computation interval;

computing the mean of the standard deviation values over the computation interval; and

calculating the estimate of the SVV proportional to the ratio between the standard deviation of the standard deviation values and the mean of the standard deviation.

6. A method as in claim 1, further comprising:

measuring arterial pressure using a catheter-mounted pressure transducer; and

converting the measured arterial pressure into the waveform data set.

7. A method as in claim 1, further comprising:

measuring arterial pressure non-invasively; and

converting the measured arterial pressure into the waveform data set.

8. A method as in claim 1, further comprising calculating an estimate of right ventricular end diastolic volume as being inversely proportional to the calculated estimate of the cardiac stroke volume variation.

9. A method as in claim 1, further comprising:

computing an approximating function that best matches the calculated standard deviation values according to a predetermined metric over at least one of the computation intervals;

creating a set of sampled, approximating values by sampling the approximating function at an interval-specific sampling rate;

low-pass filtering the sampled, approximating values; and

calculating the estimate of the SVV as a function of the low-pass filtered, sampled approximating values.

10. A system for determining a cardiac parameter equal to or derivable from cardiac stroke volume variation (SVV) comprising:

an arrangement for determining and inputting a waveform data set corresponding to arterial blood pressure over a computation interval that covers at least two cardiac cycles;

a processing system including computer-executable code for calculating a standard deviation value for the waveform data set over each cardiac cycle; and

for calculating an estimate of the SVV as a function of the standard deviation values.

11. A system as in claim 10, in which the processing system further includes additional computer-executable code:

for determining maximum and minimum standard deviation values over the computation interval; and

for calculating the estimate of the SVV as a function of the maximum and minimum standard deviation values.

12. A system as in claim 11, in which the processing system further includes additional computer-executable code

for computing a mean standard deviation value over the computation interval;

and

for calculating the estimate of the SVV to be proportional to the difference between the maximum and minimum standard deviation values relative to the mean standard deviation value.

13. A system as in claim 10, further comprising a mechanism for detecting the boundaries of respiratory cycles, in which the computation interval is at least one respiratory cycle.

14. A system as in claim 13, in which the processing system further includes additional computer-executable code

for computing the standard deviation of the standard deviation values over the computation interval;

for computing the mean of the standard deviation values over the computation interval; and

for calculating the estimate of the SVV proportional to the ratio between the standard deviation of the standard deviation values and the mean of the standard deviation.

15. A system as in claim 10, further comprising:

a catheter-mounted pressure transducer measuring arterial blood pressure; and

conversion circuitry converting the measured arterial pressure into the waveform data set.

16. A system as in claim 10, further comprising:

a non-invasive arterial pressure measurement device; and

conversion circuitry converting the measured arterial pressure into the waveform data set.

17. A system as in claim 10, in which the processing system further includes additional computer-executable code for calculating an estimate of right ventricular end diastolic volume as being inversely proportional to the calculated estimate of the cardiac stroke volume variation.

18. A system as in claim 10, in which the processing system further includes a low-pass filter and additional computer-executable code

for computing an approximating function that best matches the calculated standard deviation values according to a predetermined metric over at least one of the computation intervals;

for creating a set of sampled, approximating values by sampling the approximating function at an interval-specific sampling rate; and

for calculating the estimate of the SVV as a function of the low-pass filtered, sampled approximating values filtered by the low-pass filter.

19. A method for determining a cardiac or hemodynamic output value comprising:

inputting a waveform data set corresponding to measurements of a measurement parameter;

generating a series of measurement values from the waveform data set;

computing an approximating function that best matches the measurement values according to a predetermined metric;

over each of at least one computation interval, creating a set of sampled, approximating values by sampling the approximating function at an interval-specific sampling rate;

low-pass filtering the sampled, approximating values; and

calculating an estimate of the output Value as a function of the low-pass filtered, sampled approximating values.

20. A method as in claim 19, in which the output value displays respiration-induced variation, further comprising:

identifying respiratory cycles;

detecting cardiac cycles;

setting the computation interval to be a respiratory cycle; and

for each computation interval, setting the interval-specific sampling rate as a function of the number of cardiac cycles in each respective respiratory cycle.

21. A method as in claim 19, in which the step of generating the series of measurement values includes pre-processing the waveform data set.

22. A method as in claim 19, in which the waveform data set corresponds to blood pressure, further comprising computing each measurement value to be a function of the standard deviation of blood pressure over each respective computation interval.

23. A method as in claim 19, in which the output value is systolic pressure variation.

24. A method as in claim 19, in which the output value is pulse pressure variation.

25. A system for determining a cardiac or hemodynamic output value comprising:

an arrangement for determining and inputting a waveform data set corresponding to measurements of a measurement parameter;

a low-pass filter;

a processing system including computer-executable code

for generating a series of measurement values from the waveform data set;

for computing an approximating function that best matches the measurement values according to a predetermined metric;

over each of at least one computation interval, for creating a set of sampled, approximating values by sampling the approximating function at an interval-specific sampling rate;

calculating an estimate of the output value as a-function of the sampled approximating values after filtering by the low-pass filter.

26. A system as in claim 25, in which the output value displays respiration-induced variation, further comprising:

an arrangement for identifying respiratory cycles;

an arrangement for detecting cardiac cycles;

in which the processing system further includes additional computer-executable code

for setting the computation interval to be a respiratory cycle; and

for each computation interval,'"'"'setting the interval-specific sampling rate as a function of the number of cardiac cycles in each respective respiratory cycle.

27. A system as in claim 25, further including a pre-processing module, included in the processing system, that pre-processes the series of measurement values includes pre-processing the waveform data set.

28. A system as in claim 25, in which

the arrangement for determining and inputting the waveform data includes a mechanism for determining blood pressure,

the waveform data set corresponds to blood pressure,

in which the processing system further includes additional computer-executable code for computing each measurement value to be a function of the standard deviation of blood pressure over each respective computation interval.

29. A system as in claim 25, in which the output value is systolic pressure variation.