Apparatus and method for determination of stroke volume using the brachial artery

• US 20060009710A1
• Filed: 06/21/2005
• Published: 01/12/2006
• Est. Priority Date: 06/16/2004
• Status: Active Grant

• Current Assignee: Cordeus, Inc.
• Original Assignee: Cordeus, Inc.
• Inventors: Bernstein, Donald P.
• Granted Patent: US 7,806,830 B2
• Time in Patent Office: Days
• US Class Current: 600/547
• 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 5/029 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
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

Provided herein are methods and apparatus for stroke volume determination by bioimpedance from a patient'"'"'s upper arm, or brachium, or a patient'"'"'s thorax, utilizing pulsations of the arteries contained therein. The apparatus includes two or more spaced apart alternating current flow electrodes positioned on the patient'"'"'s arm or thorax and two or more spaced apart voltage sensing electrodes positioned on the patient'"'"'s arm or thorax and in-between alternating current flow electrodes. The system and method utilizes the mean value of the second time-derivative of the cardiogenically induced impedance variation of the patient using the measured voltage from the voltage sensors in calculating the stroke volume of the patient.

Claims

1. An apparatus for determining stroke volume by bioimpedance from a patient, comprising:

two or more spaced apart alternating current flow electrodes positionable on a patient;

two or more spaced apart voltage sensing electrodes positionable on the patient and between the alternating current flow electrodes;

an alternating current source electrically connected to the alternating current flow electrodes;

a voltmeter electrically connected to the voltage sensing electrodes; and

a processing unit in communication with the voltage sensing electrodes, wherein the processing unit is capable of using a voltage sensed by the voltage sensing electrodes to calculate a mean value of a second time-derivative of a cardiogenically induced impedance variation of the patient and to determine therefrom a stroke volume of the patient.

2. The apparatus of claim 1, wherein the alternating current flow electrodes and the voltage sensing electrodes are positionable on an arm of the patient proximate a brachial artery.

3. The apparatus of claim 1, wherein the alternating current flow electrodes and the voltage sensing electrodes are positionable on a base of the patient'"'"'s neck and on a lower thorax of the patient.

4. The apparatus of claim 1, wherein the processing unit calculates the mean value of the second time-derivative of the cardiogenically induced impedance variation as a peak rate of change of the cardiogenically induced impedance variation divided by a time to peak value of the cardiogenically induced impedance.

5. The apparatus of claim 4, wherein the time to peak value is a measured time period between an aortic valve of the patient opening and a peak rate of change of the cardiogenically induced impedance variation.

6. The apparatus of claim 4, wherein the time to peak value is a selected time value at least as great as 0.01 seconds and no greater than 0.1 seconds.

7. The apparatus of claim 4, wherein the time to peak value is a corrected rise time between an aortic valve of the patient opening and a peak rate of change of the cardiogenically induced impedance variation.

8. The apparatus of claim 4, wherein the time to peak value is calculated as (TTP_c+TTP_m)/A, where TTP_m is a measured time period between an aortic valve of the patient opening and a peak rate of change of the cardiogenically induced impedance variation, TTP_c is a corrected rise time between an aortic valve of the patient opening and a peak rate of change of the cardiogenically induced impedance variation, and A is a value greater than zero but not greater than 5.

9. The apparatus of claim 4, wherein the time to peak value is calculated as (TTP_c+TTP_b)/A, where TTP_b is a selected time value at least as great as 0.01 seconds and no greater than 0.1 seconds, and TTP_c is a corrected rise time between an aortic valve of the patient opening and a peak rate of change of the cardiogenically induced impedance variation, and A is a value greater than zero but not greater than 5.

10. The apparatus of claim 4, wherein the time to peak value is calculated as (TTP_m+TTP_b)/A, where TTP_b is a selected time value at least as great as 0.01 seconds and no greater than 0.1 seconds, and TTP_m is a measured time period between an aortic valve of the patient opening and a peak rate of change of the cardiogenically induced impedance variation, and A is a value greater than zero but not greater than 5.

11. The apparatus of claim 1, wherein the processing unit calculates the mean value of the second time-derivative of the cardiogenically induced impedance variation as a maximum value of the second time-derivative of the cardiogenically induced impedance variation divided by value that is greater than zero but no greater than 10.

12. The apparatus of claim 1, wherein the processing unit uses the equation:

$\mathrm{SV}=V_C·<br><br>\sqrt[3]{\left[\left(\frac{{d<br><br>}^2<br><br>Z/d<br><br>t_{\mathrm{mean}}^2}{Z_0}\right)·<br><br>{10}^{-2}\right]}·<br><br>T_{\mathrm{LVE}}$

to determine the stroke volume of the patient, wherein V_c is a volume of electrically participating tissue of the patient, d²Z/dt²_mean is a mean value of a second time-derivative of a cardiogenically induced impedance variation of the patient, Z₀ is a quasi-static base impedance, and T_LVE is a left ventricular ejection time of the patient.

13. The apparatus of claim 12, wherein T_LVE is obtained from a dZ/dt waveform.

14. The apparatus of claim 13, wherein a trigger for initiating processing of the dZ/dt waveform is obtained from an R wave of an antecedent ECG waveform or a C wave of an antecedent dZ/dt waveform.

15. The apparatus of claim 12, wherein T_LVE is obtained from a pulse oximetry waveform (Δ

SpO₂(t)), or its first time-derivative, dSpO₂(t)/dt.

16. The apparatus of claim 12, wherein T_LVE is obtained from an applanation tonometry (pressure) waveform (Δ

P(t)), or its first time-derivative dP(t)/dt.

17. The apparatus of claim 12, wherein T_LVE is obtained from regression equations.

18. A method of determining stroke volume by bioimpedance from a patient, comprising:

positioning two or more spaced apart alternating current flow electrodes on a patient;

positioning two or more spaced apart voltage sensing electrodes on the patient and between the alternating current flow electrodes;

providing an alternating current flow (I(t)) through the electrically conductive electrodes creating a current field;

measuring a voltage (U(t)) between the voltage sensing electrodes within the current field; and

calculating a mean value of a second time-derivative of a cardiogenically induced impedance variation of the patient using the measured voltage (U(t)); and

calculating the stroke volume (SV) of the patient using the calculated second time-derivative mean value.

19. The method of claim 18, wherein the positioning of the alternating current flow electrodes includes positioning the alternating current flow electrodes on an arm of the patient proximate a brachial artery, and wherein the positioning of the voltage sensing electrodes including positioning the voltage sensing electrodes on the arm of the patient proximate the brachial artery.

20. The method of claim 18, wherein the positioning of the alternating current flow electrodes includes positioning the alternating current flow electrodes on a base of the patient'"'"'s neck and on a lower thorax of the patient, and wherein the positioning of the voltage sensing electrodes including positioning the voltage sensing electrodes on the base of the patient'"'"'s neck and on the lower thorax of the patient

21. The method of claim 18, wherein the calculating of the second time-derivative mean value includes dividing a peak rate of change of the cardiogenically induced impedance variation by a time to peak value of the cardiogenically induced impedance.

22. The method of claim 21, wherein the time to peak value is determined by measuring a time period between an aortic valve of the patient opening and a peak rate of change of the cardiogenically induced impedance variation.

23. The method of claim 21, wherein the time to peak value is determined by selecting a time value at least as great as 0.01 seconds and no greater than 0.1 seconds.

24. The method of claim 21, wherein the time to peak value is determined by correcting a rise time between an aortic valve of the patient opening and a peak rate of change of the cardiogenically induced impedance variation.

25. The method of claim 21, wherein the time to peak value is determined by calculating (TTP_c+TTP_m)/A, where TTP_m is a measured time period between an aortic valve of the patient opening and a peak rate of change of the cardiogenically induced impedance variation, TTP_c is a corrected rise time between an aortic valve of the patient opening and a peak rate of change of the cardiogenically induced impedance variation, and A is a value greater than zero but not greater than 5.

26. The method of claim 21, wherein the time to peak value is determined by calculating (TTP_c+TTP_b)/A, where TTP_b is a selected time value at least as great as 0.01 seconds and no greater than 0.1 seconds, and TTP_c is a corrected rise time between an aortic valve of the patient opening and a peak rate of change of the cardiogenically induced impedance variation, and A is a value greater than zero but not greater than 5.

27. The method of claim 21, wherein the time to peak value is determined by calculating (TTP_m+TTP_b)/A, where TTP_b is a selected time value at least as great as 0.01 seconds and no greater than 0.1 seconds, and TTP_m is a measured time period between an aortic valve of the patient opening and a peak rate of change of the cardiogenically induced impedance variation, and A is a value greater than zero but not greater than 5.

28. The method of claim 18, wherein mean value of the second time-derivative of the cardiogenically induced impedance variation is calculated as a maximum value of the second time-derivative of the cardiogenically induced impedance variation divided by value that is greater than zero but no greater than 10.

29. The method of claim 18, wherein the calculating the stroke volume (SV) includes:

determining a volume of electrically participating tissue V_c of the patient;

determining a quasi-static base impedance Z₀;

determining a left ventricular ejection time T_LVE of the patient; and

calculating the stroke volume (SV) of the patient using the equation;

$\mathrm{SV}=V_C·<br><br>\sqrt[3]{\left[\left(\frac{{d<br><br>}^2<br><br>Z/d<br><br>t_{\mathrm{mean}}^2}{Z_0}\right)·<br><br>{10}^{-2}\right]}·<br><br>T_{\mathrm{LVE}}$

wherein d²Z/dt²_mean is the second time-derivative mean value.

30. The method of claim 29, wherein T_LVE is determined from a dZ/dt waveform.

31. The method of claim 30, wherein a trigger for initiating a processing of the dZ/dt waveform is obtained from an R wave or a C wave of an antecedent ECG waveform.

32. The method of claim 29, wherein T_LVE is determined from a pulse oximetry waveform (Δ

SpO₂(t)), or its first time-derivative, dSpO₂(t)/dt.

33. The method of claim 29, wherein T_LVE is determined from an applanation tonometry (pressure) waveform (Δ

P(t)), or its first time-derivative dP(t)/dt.

34. The method of claim 29, wherein T_LVE is determined from regression equations.