Device for determining hemodynamic state

• US 20050090753A1
• Filed: 03/21/2002
• Published: 04/28/2005
• Est. Priority Date: 04/02/2001
• Status: Abandoned Application

• Current Assignee: N.I. Medical Ltd.
• Original Assignee: N.I. Medical Ltd.
• Inventors: Cotter, Gad, Goor, Daniel, Moshkovitz, Yaron
• Application Number:
  US10/489,670
• Publication Number:
  US 20050090753A1
• Time in Patent Office: Days
• US Class Current: 600/508
• 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

Abstract

A non-invasive device for determining the hemodynamic state of a subject. The device comprises: (a) at least two electrodes (20); (b) an electrical total body integral bioimpedance measuring unit (26) coupled to the electrodes; and (c) a data processing and analyzing unit (30) coupled to the electrical integral bioimpedance measuring unit and optionally to a display means (34) for calculating the cardiac output of the subject from the active component of the-integral bioimpedance. Also disclosed are methods for determining the hemodynamic state of a subject and for diagnosing a tendency of a subject to a cardiac disease.

Claims

1. A non-invasive device for determining the hemodynamic state of a subject comprising:

(a) at least two electrodes;

(b) electrical total body integral bioimpedance measuring unit coupled to the electrodes and including a high stability amplitude alternating current source and an electronic circuit for automatic derivation of an active component of said integral bioimpedance; and

(c) a data processing and analyzing unit coupled to the electrical integral bioimpedance measuring unit and optionally to a display means for calculating the cardiac output of said subject from the active component of the integral bioimpedance; and

(d) optionally, display means;

wherein said data processing and analyzing unit has a predetermined analyzer utility operable to calculate the cardiac index (CI) of said subject from the cardiac output (CO);

and wherein the mean arterial blood pressure (MAP) of said subject has been entered into said data processing and analyzing unit;

and wherein said data processing and analyzing unit has a predetermined analyzer utility operable to calculate the cardiac power index (Cp_i) of said subject according to the formula Cp_i=CI*MAP, and to calculate the systemic vascular resistance index (SVR_i) of said subject according to the formula SVR_i=n*MAP/CI, where n=0.85 to 0.95, thereby obtaining a Cp_i and SVR_i paired value for said subject;

and wherein said data processing and analyzing unit has a predetermined analyzer utility including a memory for storing a plurality of sets of Cp_i and SVR_i paired values, each set corresponding to a hemodynamic state selected from the group consisting of systolic congestive heart failure (sCHF), pulmonary edema (PE), cardiogenic shock (CS), vasodilative shock (VS) and normal state, said sets of Cp_i and SVR_i paired values originating from a plurality of subjects who have been previously diagnosed as having said hemodynamic states;

and wherein said data processing and analyzing unit has a predetermined analyzer utility operable to compare the Cpi and SVRi paired value of said subject to the sets of Cp_i and SVR_i paired values;

and wherein said data processing and analyzing unit has a predetermined analyzer utility operable to determine the set of Cp_i and SVR_i paired values which is most similar to the Cp_i and SVR_i paired value of said subject, the hemodynamic state corresponding to said set indicating the hemodynamic state of said subject.

2. A device according to claim 1 wherein the cardiac output (CO) is calculated from the stroke volume (SV) and the heart rate (HR) of said subject according to the formula CO=SV*HR.

3. A device according to claim 2 wherein the SV is calculated substantially according to the following equation:

$\mathrm{SV}=\frac{{\mathrm{Hct}}_{\mathrm{corr}.}}{K<br><br>\left(\mathrm{shape}*\mathrm{sex}*\mathrm{age}\right)}*\mathrm{\delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>r<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{H_{\mathrm{corr}.}^2}{R}*\frac{\mathrm{\alpha <br><br>}+\mathrm{\beta <br><br>}}{\mathrm{\beta <br><br>}}*\mathrm{Ke1}*\mathrm{Kw}*\mathrm{IB}$

where;

Hct_corr. is a correcting factor depending from hematocrit, being 145+0.35(Hct−

40);

Hct is the hematocrit, obtained from analysis of the individual'"'"'s blood;

K(shape*sex*age) is a coefficient of the individual'"'"'s body, being;

527.3−

(3.1*(Actual Age −

20)), for men younger than 20 years old;

527.3, for men from 20 to 40 years old;

527.3+(3.1*(Actual Age −

40)), for men older than 40 years old;

587.6−

(2.9*(Actual Age −

18)), for women younger than 18 years old;

587.6, for women from 18 to 50 years old;

587.6+(2.9*(Actual Age −

50)), for women older than 50 years old;

δ

r is the amplitude value of the change of the individual'"'"'s basic body resistance R at the anacrotic (systolic) portion of a cardiac cycle;

R is the individual average basic body resistance during one cardiac cycle;

H_corr. is a corrected height of the individual, given by;

$\begin{array}{c}{H}_{\mathrm{corr}}=\left(H_{\mathrm{real}}+2\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{if}<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{\mathrm{legs}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{length}}{\mathrm{body}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{length}}=0.66\pm <br><br>0.04\\ \mathrm{or}\\ H_{\mathrm{corr}}=\left(H_{\mathrm{real}}-2\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{if}<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{\mathrm{legs}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{length}}{\mathrm{body}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{length}}=0.54\pm <br><br>0.04\\ \mathrm{or}\\ H_{\mathrm{corr}}=\left(H_{\mathrm{real}}\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{if}<br><br>\text{\hspace{1em}<br><br>}<br><br>0.62\ge <br><br>\frac{\mathrm{legs}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{length}}{\mathrm{body}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{length}}\ge <br><br>0.58\end{array}$

α

+β

is duration of a cardiac cycle, being a sum of its anacrotic and catacrotic portion;

β

is duration of the catacrotic portion of a cardiac cycle;

Kel is a coefficient depending on ion concentration in the individual'"'"'s blood plasma, calculated based on the blood analysis and being given by;

a) for an individual exposed to a hemodialysis

$\begin{array}{c}\mathrm{Kel}=<br><br>\mathrm{sum}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{of}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{the}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{blood}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{concentrations}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{at}\\ <br><br>\frac{{\mathrm{Na}}^{+}+K^{+}+{\mathrm{Mg}}^{+}+{\mathrm{Ca}}^{+}}{142+13}<br><br>9\end{array}$

b) for other individuals

$\mathrm{Kel}=\mathrm{blood}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{concentration}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{of}<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{{\mathrm{Na}}^{+}}{142};<br><br>$

K_w is a weight coefficient, being a ratio

$\frac{\mathrm{Actual}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{weight}}{\mathrm{Ideal}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{weight}},$

where Ideal weight being obtained from International Tables of ideal weights; and

IB is an Index Balance, reflecting ratio between the measured volume of extracellular fluids and the individual'"'"'s proper volume of extracellular fluids, wherein the Index Balance is calculated based on the following formula;

$\frac{R_{\mathrm{ind}.\text{\hspace{1em}<br><br>}<br><br>\mathrm{prop}}}{R_{\mathrm{measured}}}$

where R measured is the measured resistive component of the individual'"'"'s bioimpedance, not including the individual'"'"'s skin resistance;

R_{ind. prop.} is a proper value of the resistive component of the indivudual'"'"'s bioimpedance being calculated according to the two following formulae;

$\frac{0.42<br><br>H^2}{0.47<br><br>W-8.30}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{for}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{men}$$\frac{0.42<br><br>H^2}{0.37<br><br>W-4.96}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{for}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{women}$

where H is the individual'"'"'s height, and

W is the individual'"'"'s actual weight.

4. A device according to claim 1 further comprising means for measuring the MAP of said subject and transmitting the MAP data directly into the data processing and analyzing unit.

5. A device according to claim 1 wherein n=0.9.

6. A device according to claim 1 wherein the hemodynamic state of said subject is displayed on said display means.

7. A device according to claim 6 wherein the Cp_i and SVR_i paired value of said subject is displayed on said display means.

8. A device according to claim 6 wherein the HR, SV, CO and CI values of said subject are displayed on said display means.

13. A method according to claim 10 wherein said Cp_i and SVR_i paired values of said subject are determined using a device according to claim 1.

9. A method for determining the hemodynamic state of a subject, comprising the steps of:

(a) attaching at least two electrodes to the subject'"'"'s body in a manner ensuring a low impedance contact between the electrodes and the individual'"'"'s skin, and positioning the electrodes so that current which passes between the at least two electrodes flows between at least one arm or at least one leg to at least another arm or at least another leg of the individual;

(b) passing an alternating current with a stable and constant amplitude through said at least two electrodes and at the same time, measuring the potential change as the result of the current flow, whereby an electrical bioimpedance measurement of the individual'"'"'s body from the measured potential between the said at least two electrodes is obtained;

(c) simultaneously separating an active component from said integral bioimpedance;

(d) calculating the stroke volume (SV) of said subject from the active component of said integral bioimpedance, using a semi-empiric formula applicable to integral bioimpedance measurements, in such a manner so as to obtain a number of values of the SV for a number of cardiac cycles during a respiratory cycle, and calculating an average of the SV during a single respiratory cycle;

(e) calculating the cardiac output (CO) of said subject from the SV;

(f) calculating the cardiac index (CI) of said subject from the CO;

(g) calculating the cardiac power index (Cp_i) of said subject according to the formula Cp_i=CI * mean arterial blood pressure (MAP), and to calculate the systemic vascular resistance index (SVR_i) of said subject according to the formula SVR_i=n*MAP/CI, where n=0.85 to 0.95, thereby obtaining a Cp_i and SVR_i paired value for said subject;

(h) comparing the Cp_i and SVR_i paired value of said subject to a plurality of sets of Cp_i and SVR_i paired values, each set corresponding to a hemodynamic state selected from the group consisting of systolic congestive heart failure (sCHF), pulmonary edema (PE), cardiogenic shock (CS), vasodilative shock (VS) and normal state, said sets of Cp_i and SVR_i paired values originating from a plurality of subjects who have been previously diagnosed as having said hemodynamic states; and

(i) determining the set of Cp_i and SVR_i paired values which is most similar to the Cp_i and SVR_i paired value of said subject, the hemodynamic state corresponding to said set indicating the hemodynamic state of said subject.

10. A method for diagnosing a tendency of a subject to a cardiac disease comprising:

(a) measuring a first Cp_i and SVR_i paired value of said subject;

(b) performing a step of a stress test on said subject;

(c)measuring a second Cp_i and SVR_i paired value of said subject;

(d) optionally repeating steps (b) and (c) one or more times;

(e)comparing said first Cp_i and SVR_i paired value with said second and optional subsequent Cp_i and SVR_i paired values, wherein a decrease in Cp_i of >

15%, an increase in SVR_i of >

15% or an increase in Cp_i to <

400 watt/M² during stages 3 or 4 of said stress test indicates that said subject is prone to myocardial ischemia,

and wherein if said first Cp_i is <

2.7 L./min/M² and said first SVR_i is >

35 wood/M² and said Cp_i increases to <

400 watt/M² without a subsequent decrease in Cp_i or an increase in SVR_i during stages 3 or 4 of said stress test indicates that said subject is prone to systolic congestive heart failure (sCBF).

11. A method according to claim 10 wherein said stress test is selected from the group consisting of pharmacological, exercise and mental stress tests.

12. A method according to claim 11 wherein said pharmacological stress test uses dobutamine, dipyridamole or adenosine.