Process for determining the volume of blood in circulation

A process for determining circulating blood volume V.sub.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.sub.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.sub.m g.sub.m are described by left-skewed distribution functions, repeated recursive convolutions are carried out according to the equations ##EQU7## while the parameters k, a.sub.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 a.sub.1 g.sub.1 (t) is posited, and C.sub.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.sub.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.sub.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.sub.d from the known amount of indicator dye and the virtual dye concentration C.sub.o at the time point t=0 according to the relation V.sub.d =M.sub.o /C.sub.o.

A process for determining circulating blood volume V.sub.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.sub.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.sub.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.sub.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.sub.d from the known amount of indicator dye and the virtual dye concentration C.sub.o at the time point t=0 according to the relation V.sub.d =M.sub.o /C.sub.o.

A process for determining circulating blood volume V.sub.d in a patient comprising the steps of:

• a) injecting a known amount of indicator dye M.sub.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.sub.d based upon the circulating time course C(t).

A process for determining circulating blood volume V.sub.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.sub.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.sub.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.sub.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.sub.d from the known amount of indicator dye and the virtual dye concentration C.sub.o at the time point t=0 according to the relation V.sub.d =M.sub.o /C.sub.o.