Process for determining the volume of blood in circulation

• US 5,687,726 A
• Filed: 04/03/1995
• Issued: 11/18/1997
• Est. Priority Date: 09/13/1991
• Status: Expired due to Term

• Current Assignee: Andreas Hoeft
• Original Assignee: Andreas Hoeft
• Inventors: Hoeft, Andreas
• Primary Examiner(s): Casler, Brian L.
• Application Number:
  US08/415,583
• Time in Patent Office: 960 Days
• Field of Search: 128/653.1, 128/654, 128/633, 128/691, 128/692, 128/694, 128/666
• US Class Current: 600/431
• CPC Class Codes: A61B 5/0275 using tracers, e.g. dye dilution

Abstract

A process of rapidly determining the blood circulation volume in a patient during surgery. Blood circulation volume is determined from circulation transport functions based on the evaluation of a compartmental analysis of a dye dilution curve. The information content of the entire dye dilution curve is utilized for the calculation of the parameters of the circulation transport function.

Claims

1. A process for determining circulating blood volume V_d in a patient comprising the steps of:

a) injecting a known amount of indicator dye M_o into the circulating blood whereby the dye circulates with the blood and the concentration of dye in the blood varies with time in an indicator dye dilution curve indicative of a dye concentration time course C(t);

b) optically measuring the dye concentration time course C(t) in the circulating blood immediately after injecting the dye;

c) from the concentration time course C(t), calculating the mean transit time m_tt which the indicator dye requires in order to pass through a predetermined portion of the circulation;

d) measuring the blood volume flow V in the patient; and

e) calculating the blood volume V_d using the equation V_d =V * m_tt.

2. A process for determining circulating blood volume V_d in a patient whose circulation has a characteristic transport function g(t) and circulation pulse response, comprising the steps of:

a) injecting a known amount of indicator dye M_o into the circulating blood whereby the dye circulates with the blood and the concentration of dye in the blood varies with time in an indicator dye dilution curve to establish a dye concentration time course C(t) for the dye in the circulating blood;

b) optically measuring the dye concentration time course C(t) in the circulating blood immediately after injecting the dye;

c) calculating the circulation transport function g(t) for the patient based on the measured dye concentration time course c(t) using an iterative, nonlinear adaptation process, wherein under allowance of a model function ##EQU6## in which the individual compartments a_m g_m are described by left-skewed distribution functions, repeated recursive convolutions are carried out according to the equations ##EQU7## while the parameters k, a_m as well as the parameters of the distribution functions are optimized according to the process of the least quadratic deviation, in which at least one compartment a₁ g₁ (t) is posited, and C_bolus (t) is the constituent directly passing through the measuring place of the dye concentration time course C(t) and k the elimination fraction of the dye eliminated through the liver;

d) determining the circulation pulse response d(t) which corresponds to an ideal indicator injection in an extremely brief period of time at point t=0 using the circulation transport function g(t);

e) determining a virtual dye concentration C_o at the time point t=0 from the circulation pulse response d(t) by back-extrapolation or direct calculation from the parameters of the circulation transport function g(t), wherein the virtual dye concentration C_o is the hypothetical concentration of dye in the blood if all the dye were injected instantaneously at a time t=0; and

f) calculating the blood volume V_d from the known amount of indicator dye and the virtual dye concentration C_o at the time point t=0 according to the relation V_d =M_o /C_o.

3. The process according to claim 2, wherein:

a) two compartments a_g and a₂ g₂ are posited in the calculation of the circulation transport function.

4. The process according to claims 2, and including the step of:

a) optically measuring the dye concentrationtive course resulting in the circulating blood by fiber-optic measurement in a central vessel.

5. The process according to claim 2, further characterized in that:

a) optically measuring the dye concentration resulting in the blood circulation non-invasively by measuring light-transmission or reflection at a suitable place on the body.

6. A process for determining circulating blood volume V_d in a patient whose circulation has a characteristic transport function g(t) and circulation pulse response, comprising the steps of:

a) injecting a known amount of indicator dye M_o into the circulating blood whereby the dye circulates with the blood and the concentration of dye in the blood varies with time in an indicator dye dilution curve indicative of a dye concentration time course C(t);

b) optically measuring the dye concentration time course C(t) in the circulating blood by fiber-optic measurement in a central vessel immediately after injecting the dye;

c) calculating the circulation transport function g(t) for the patient based on the measured dye concentration time course C(t);

d) determining the circulation pulse response d(t) which corresponds to an ideal indicator injection in an extremely brief period of time at point t=0 using the circulation transport function g(t);

e) determining a virtual dye concentration C_o at the time point t=0 from the circulation pulse response d(t) by back-extrapolation or direct calculation from the parameters of the circulation transport function g(t), wherein the virtual dye concentration C_o is the hypothetical concentration of dye in the blood if all the dye were injected instantaneously at a time t=0; and

f) calculating the blood volume V_d from the known amount of indicator dye and the virtual dye concentration C_o at the time point t=0 according to the relation V_d =M_o /C_o.

7. A process for determining circulating blood volume V_d in a patient comprising the steps of:

a) injecting a known amount of indicator dye M_o into the circulating blood whereby the dye circulates with the blood and the concentration of dye in the blood varies with time in an indicator dye dilution curve to establish a dye concentration time course C(t) for the dye in the circulating blood;

b) optically measuring the dye concentration time course C(t) in the circulating blood non-invasively by measuring light-transmission or reflection at a suitable place on the body immediately after injecting the dye; and

c) calculating the blood volume V_d based upon the circulating time course C(t).

8. A process for determining circulating blood volume V_d in a patient whose circulation has a characteristic transport function g(t) and circulation pulse response, comprising the steps of:

a) injecting a known amount of indicator dye M_o into the circulating blood whereby the dye circulates with the blood and the concentration of dye in the blood varies with time in an indicator dye dilution curve to establish a dye concentration time course C(t) for the dye in the circulating blood;

b) optically measuring the dye concentration time course C(t) in the circulating blood non-invasively by measuring light-transmission or reflection at a suitable place on the body immediately after injecting the dye;

c) calculating the circulation transport function g(t) for the patient based on the measured dye concentration time course C(t);

d) determining the circulation pulse response d(t) which corresponds to an ideal indicator injection in an extremely brief period of time at point t=0 using the circulation transport function g(t);

e) determining a virtual dye concentration C_o at the time point t=0 from the circulation pulse response d(t) by back-extrapolation or direct calculation from the parameters of the circulation transport function g(t), wherein the virtual dye concentration C_o is the hypothetical concentration of dye in the blood if all the dye were injected instantaneously at a time t=0; and

f) calculating the blood volume V_d from the known amount of indicator dye and the virtual dye concentration C_o at the time point t=0 according to the relation V_d =M_o /C_o.