Four-compartment whole body model with recirculation: repeated injections and first order hepatic clearance of Indocyanine Green dye.

Description

This is a whole body model composed of a central blood volume from which flows the whole cardiac output. The C.O.is distributed into three organs labelled "kidney" for kidney and heart,"liver", for liver and intestines, and "muscle" for the rest of the body. The four compartment model has recirculation. The input function to compartment 1 (Heart and Lung) is the sum of the recirculated indicator plus a series of injection pulses into V1, Qinjrate, each injection at x mg/min for a short duration. Each injection, Cin#, is defined at run time using a separate function generator. Clearance of the injected dye, indocyanine green, is really hepatic extraction via a saturable transporter followed by ATP-dependent excretion into the bile, but is represented here by a passive first order loss, G3; This is adequate kinetically only at low concentrations of ICG, where the transporter is mainly uncomplexed.

Figure: Time course of ICG clearance during multiple injections of ICG over the course of 240 minutes.
Green line is model simulation results, triangles are Edwards 1960 figure 1 data, and black lines
are injections of ICG (for timing purposes only).

Equations

The equations for this model may be viewed by running the JSim model applet and clicking on the Source tab at the bottom left of JSim's Run Time graphical user interface. The equations are written in JSim's Mathematical Modeling Language (MML). See the Introduction to MML and the MML Reference Manual. Additional documentation for MML can be found by using the search option at the Physiome home page.