Pressure-based system and method for determining cardiac stroke volume

• US 7,785,263 B2
• Filed: 03/09/2007
• Issued: 08/31/2010
• Est. Priority Date: 12/05/2003
• Status: Active Grant

• Current Assignee: Edwards Lifesciences Corporation
• Original Assignee: Edwards Lifesciences Corporation
• Inventors: Meyer, Doug Jr., Roteliuk, Luchy, McKown, Russell
• Primary Examiner(s): Getzow; Scott M
• Application Number:
  US11/684,525
• Publication Number:
  US 20070149884A1
• Time in Patent Office: 1,271 Days
• Field of Search: 600481-507
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• 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 5/7239 using differentiation including higher order derivatives

Abstract

Cardiac stroke volume (SV) of a subject is estimated as a function of a value derived from a measured arterial pressure waveform. The value may be the standard deviation, or a function of the difference between maximum and minimum pressure values, or a function of either the maximum value of the first time derivative or the absolute value of the minimum of the first time derivative of the pressure waveform, or both, or a function of the magnitude of one or more spectral components of the pressure waveform at a frequency corresponding to the heart rate. Cardiac output is then estimated as the product of the subject'"'"'s heart rate and SV, scaled by a calibration constant. Arterial pressure may be measured invasively or non-invasively.

Claims

1. A method for determining cardiac stroke volume of a subject comprising:

sensing arterial blood pressure;

converting the sensed arterial blood pressure to a pressure signal;

determining the heart rate of the subject;

determining the amplitude of a spectral component of the pressure signal for a frequency corresponding to a multiple of the heart rate;

calculating an average value of the pressure signal; and

calculating an estimate of the stroke volume as a function of the ratio of the amplitude of the spectral component and the average value of the pressure signal.

2. A method of claim 1, wherein sensing uses a blood pressure sensor, converting uses an analog-to-digital converter and further comprising outputting a parameter based on the estimate of stroke volume on a display.

3. A method of claim 1, wherein determining the amplitude of the spectral component includes using a Fourier transform.

4. A method of claim 3, wherein determining the heart rate includes using a Fourier transform.

5. A method of claim 4, wherein sensing arterial pressure is performed using a sensor placed in a peripheral artery.

6. A method for determining cardiac stroke volume of a subject comprising:

sensing arterial blood pressure;

converting the sensed arterial blood pressure to a pressure signal;

detecting a maximum value and minimum value of the first time derivative of the pressure value during a measurement interval; and

calculating an estimate of the stroke volume as a function of a magnitude of one of the maximum or minimum values,

wherein the estimate of the stroke volume is proportionate to a standard deviation calculated using the magnitude of the maximum and minimum values.

7. A method of claim 6, wherein the estimate of the stroke volume is also proportionate to the magnitude of the maximum or minimum value.

8. A method of claim 7, wherein the estimate of the stroke volume is proportionate to the magnitude of both the maximum and minimum values.

9. A method of claim 6, wherein the standard deviation is calculated by dividing a sum of the magnitude of the maximum and minimum values by 3.

10. A method of claim 6, wherein detection of the maximum and minimum values is determined only between the beginning of a cardiac cycle and a dichrotic point.

11. A method of claim 6, wherein sensing uses a blood pressure sensor, converting uses an analog-to-digital converter and further comprising outputting a parameter based on the estimate of stroke volume on a display.

12. A method of claim 6, wherein a component of the estimate of the stroke volume includes the magnitude of one of the maximum or minimum values.