Model: SIMVOL-multi-organ recirculating system with shunt

TABLE OF CONTENTS

Parameters

Output Variables

Diagram

Model demonstrations with parameter sets

1. IMPORTANT !!! To run a demonstration, enter "xhost +nsr.bioeng.washington.edu" in one of your windows to allow the demonstration program to open windows on your machine !!!

2. Parameters

SIMVOL is parameterized as follows.

Table 1. SIMVOL Parameters

Parameter	Description	Units
Cin	Input concentration parameters	as specified
mass A	Mass of organ A	g
fr mass Ac	The fraction of mass A being modeled with CTEX (compartment tissue exchange model)	dimensionless
RATIO A	The ratio of flow/mass of CTEX/(CTEX+BTEX) for organ A	dimensionless
FLOW TOT	Total flow	ml/min
fr Shunt	The fraction of the flow being shunted around organ B	dimensionless
mass B	Mass of organ B	g
fr mass Bc	The fraction of mass A being modeled with CTEX (compartment tissue exchange model)	dimensionless
RATIO B	The ratio of flow/mass of CTEX/(CTEX+BTEX) for organ B	dimensionless
fr Clear	Fractional Clearance, the fraction of Cout removed each time step	dimensionless

Access to all input variables is via clicking the "INPUT" button on the main model page or by selecting "Inputs" under the "Parameters" menu.

3. Output Variables

Output variables are given by:

Table 2. SIMVOL Output Variables

Parameter	Description	Units
Cin	Input concentration waveform	molar (M)
Cin A	Input concentration to Organ A Sum of Cin + C recirc	molar (M)
Cout Ac	Outflow concentration of Organ A (CTEX)	molar (M)
Cout Ab	Outflow concentration of Organ A (BTEX)	molar (M)
Cout A	Combined concentration outflow of organ A (CTEX+BTEX)	molar (M)
Cin B	Input concentration to Organ B	molar (M)
Cout Bc	Outflow concentration of Organ B (CTEX)	molar (M)
Cout Bb	Outflow concentration of Organ B (BTEX)	molar (M)
Cout B	Combined concentration outflow of organ B (CTEX+BTEX)	molar (M)
C shunt	Concentration shunted around organ B	molar (M)
Cout	Output concentration Sum of Cout B and C shunt	molar (M)
C clear	Concentration cleared from system C clear = Cout*fr Clear	molar (M)
C recirc	Concentration recirculation Crecirc = Cout*(1 - fr Clear)	molar (M)
F/m Ac	Flow/mass for Organ A (CTEX)	ml/(min(g)
F/m Ab	Flow/mass for Organ A (BTEX)	ml/(min(g)
F/m Bc	Flow/mass for Organ B (CTEX)	ml/(min(g)
F/m Bb	Flow/mass for Organ B (BTEX)	ml/(min(g)
Flow noshunt	Flow into Organ B Flow noshunt=FLOT TOT*(1 - fr Shunt)	ml/min
Q_ct_A	Quantity of material in Organ A (CTEX)	molar*ml
Q_bt_A	Quantity of material in Organ A (BTEX)	molar*ml
Q_ct&bt_A	Quantity of material in Organ A (CTEX+BTEX)	molar*ml
Q_ct_B	Quantity of material in Organ B (CTEX)	molar*ml
Q_bt_B	Quantity of material in Organ B (BTEX)	molar*ml
Q_ct&bt_B	Quantity of material in Organ B (CTEX+BTEX)	molar*ml
Q_A&B	Quantity of material in Organs A and B combined	molar*ml
Q_integral	integral of FLOW TOT(Cin-C clear)dt	molar*ml
Qintct_A	Quantity of material in Organ A (CTEX) by integral method	molar*ml
Qintbt_A	Quantity of material in Organ A (BTEX) by integral method	molar*ml
Qintct_B	Quantity of material in Organ B (CTEX) by integral method	molar*ml
Qintbt_B	Quantity of material in Organ B (BTEX) by integral method	molar*ml
Qrecirc	Amount of material recirculation back into the system in the next time step	molar*ml

To plot results, select "Plot Area 1" from the Results menu. Place the cursor in an unused box under Y-parameters and press the right mouse button to bring up a list of plottable parameters.

5. Model demonstrations with parameter sets

The user should inspect the input parameters and the output curves. Output curves can be found under the Results button under Plot Area 1 and Plot Area 2.

The following parameter sets are can be demonstrated by clicking on them:

5.1. Figure 9.2 : Figure09.02.par

Run the model. Displacement of fluid from a well stirred chamber. Flow is 600 ml/min (10 ml/sec). Volume is 100 ml. Amount of material injected is 1 mmole. Numeric and analytic solutions are plotted.

5.2. Figure 9.3: Figure09.03.par

Run the model. Dilution into a pair of well stirred volumes. Time course of concentrations with pulse input when each of V1 and V2 are instaneously mixed. (Flow=10 ml/sec, V1=100ml, V2=200ml)

5.3. Figure 9.5: Figure09.05.par

Run the model. See output under Results: Plot Area 1. The response of the system when the solute is constrained to just the plasma space, compared to the solute entering the ISF space, with concentrations measured at the outflows of this two-organ "whole-body" model.

5.4. Figure 9.6: Figure09.06.par

Run the model. Tracer concentration-time courses under Results: Plot Area 1 for 4-organ, 3-tissue-region model analogous to that in Figure 9.5 (zero clearance). Each "organ" was composed of regions for plasma, ISF, and cells. An extracellular flow marker enters the former two regions only; tracer water enters all three regions.

5.5. Figure 9.7: Figure09.07.par

Run the model. Plasma concentratime time curves for plasma, extracellular flow, and water markers where there is tracer lost from the body and the clearance is 30%.

5.6. Figure 9.8: Figure09.08.par

Semilog plots of plasma concentrations of markers for plasma, ECF and water spaces when clearance is exactly 30% of the flow or "cardiac output" in the model used in Figure 9.6. All curves have a monoexponential tail.

5.7. Figure 9.9: Figure09.09

Semilog plot of plasma concentration time curves for a strictly intravascular marker which is gradually cleared from the circulation. The tails of the curves are fitted by a single exponential. The loss rate or clearance was set at 0, 5, 10, 15, and 20% of the whole body recirculation. Monoexponential curves fitting the "data" from 100 to 200 seconds extrapolate back to an apparent common intersection at negative time. The intercept at t=0 is lower with clearance > 0, and using its value, C(t=0) , gives overestimates of Vpl .

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Contact garyr@nsr.bioeng.washington.edu with comments, questions, or critiques.