Method for determination of cardiac output

• US 8,679,025 B2
• Filed: 08/03/2007
• Issued: 03/25/2014
• Est. Priority Date: 08/31/2006
• Status: Active Grant

• Current Assignee: Atcor Medical Pty Ltd (CardieX Ltd.)
• Original Assignee: Atcor Medical Pty Ltd (CardieX Ltd.)
• Inventors: Harpas, Peter Chris, Qasem, Ahmad M.
• Primary Examiner(s): Mallari, Patricia
• Assistant Examiner(s): Ramachandran, Vasuda
• Application Number:
  US12/438,895
• Publication Number:
  US 20100016735A1
• Time in Patent Office: 2,426 Days
• Field of Search: 600481-488, 600500-508, 600/529
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence

Abstract

A method for determination of cardiac output from a recording of an arterial pressure waveform (10). The method comprises the steps of measuring the patient'"'"'s peripheral arterial pressure relative to time in order to estimate a central pressure waveform (CPW) and calculating the patient'"'"'s cardiac output from the CPW using the Water Hammer formula (as defined herein).

Claims

1. A method for determination of cardiac output from a recording of an arterial pressure waveform, the method comprising the following steps:

a) measuring the patient'"'"'s peripheral arterial pressure relative to time and using a processor to estimate a central pressure waveform (CPW) from the patient'"'"'s peripheral arterial pressure;

b) estimating, using the processor, from the CPW, forward Pressure pulse height (P_f), flow waveform and Pulse Wave Velocity (PWV) in the ascending aorta;

c) calculating a peak velocity fluctuation V in the ascending aorta using the following Water Hammer formula;

V=P_f/(ρ

* PWV), where ρ

is the density of blood;

d) calibrating an aortic flow waveform from the estimated flow waveform using V; and

e) calculating the patient'"'"'s cardiac output from the calibrated aortic flow waveform.

2. The method as claimed in claim 1, further including calculating Peak Flow Rate (PFR) by multiplying the velocity fluctuation V by the cross sectional area of the aorta, as follows:

3. The method as claimed in claim 1, further including calculating a Mean Flow from the calibrated aortic flow waveform.

4. The method as claimed in claim 3, wherein the Mean Flow is derived from an analysis of the CPW calibrated using the Water Hammer formula.

5. The method as claimed in claim 4, further including respectively calculating and estimating:

aortic reflection time (ART);

aortic PWV; and

ejection duration (ED) from the CPW.

6. The method as claimed in claim 5, further including calculating the Mean Flow by integrating the calibrated aortic flow waveform.

7. The method as claimed in claim 6, further including calculating Stroke Volume using the following formula:

Stroke Volume=Mean Flow×

ED.

8. The method s claimed in claim 7, further including calculating Cardiac Output using the following formula:

Cardiac Output=Stroke Volume×

Heart Rate.

9. The method as claimed in claim 8, further including estimating the patient'"'"'s aortic arterial distance from:

the patents physical characteristics;

a ratio of the carotid to femoral arterial distance;

or measuring the superficial distance between sternal notch to the level of the umbilicus.

10. The method as claimed in claim 9, wherein the patient'"'"'s carotid to femoral arterial distance is estimated form the patient'"'"'s height, weight and body mass index (BMI).

11. The method as claimed in claim 9, wherein a direct measurement of the distance between the carotid and femoral artery is made.

12. The method as claimed in claim 9, wherein the patient'"'"'s carotid to femoral arterial distance is estimated from superficial body surface measurements.

13. The method as claimed in claim 9, wherein the ascending aortic pulse wave velocity (PWV) is calculated by dividing the aortic arterial distance by the aortic pulse reflection time.

14. The method as claimed in claim 1, wherein the patient'"'"'s peripheral arterial pressure measurement is taken at a single site.

15. The method as claimed in claim 14, wherein the patient'"'"'s peripheral arterial pressure measurement is taken non-invasively.

16. The method as claimed in claim 14, wherein the patient'"'"'s peripheral arterial pressure measurement is taken using a pulse wave analysis system.

17. The method as claimed in claim 14, wherein the patient'"'"'s radial artery pressure waveform is measured, which is then used to derive the patient'"'"'s CPW.

18. The method as claimed in claim 1, wherein step (a) is performed by measuring, a direct invasive radial artery recording of pressure and calculating the central pressure waveform.

19. The method as claimed in claim 1, wherein the step (a) is performed on an average radial pulse from a continuous radial pressure waveform recording for every respiratory cycle, wherein each average pulse represents the radial pressure waveform in one respiratory cycle.

20. The method as claimed in claim 1, wherein step (a) is performed on a radial pulse from a continuous radial pressure waveform recording on a beat to beat basis.

21. The method as claimed in claim 1, further including determining the following parameters:

i. The forward Pressure pulse height (P_f) in mmHg.;

ii. Aortic Pulse Reflection Time (ART) in milliseconds;

iii. Un-calibrated flow waveform;

iv. Ejection Duration (ED) in milliseconds;

v. Heart Rate (HR) in beats/min; and

vi. Carotid to Femoral distance (C-F Dist) in mm.