Model: BODY, whole body recirculation with four chambered heart, seven organs, four arteries and four veins

1. TABLE OF CONTENTS

Parameters

Outputs

Caveats:

Diagrams

Model demonstrations with parameter sets

2. Online demonstration

Available from the NSR web site. You must have X-server running on your local machine.

Users with slow internet connection should avoid using the online demo.

Users with XSIM installed on the local machine can download the demo parameter files (links are given in this document) from the NSR web site, and start the demo on your local machine with "xsim <parameter file name>".

Attention UNIX users !!! To run an online demonstration from the NSR web site, enter "xhost +nsr.bioeng.washington.edu" in one of your windows to allow the demonstration program to open windows on your machine !!!

3. Parameters

The model is parameterized at different levels. At the level of the body, the governing parameters are flow and mass (w) for each organ system, and flow and volume for the arteries, veins, and chambers of the heart.

At the submodel level, each organ being modelled with a four region blood tissue exchange model (see BTEX40) has the full range of parameters available in a BTEX40 model. The vascular transport (see VOPB10) is also characterized by relative dispersion (RD), a measure of how a signal spreads in time relative to its mean transit time. The atria are modelled as single compartment models, and the ventricles are modelled as two compartments to allow for incomplete emptying during the ejection phase of contraction. The underlying model for the heart chambers is ECOMP3 (a maximum of three compartments model).

See btex10, vopb10, and ecomp3 for their parameters .

Table 1. BODY Parameters

Parameters

Description

Typical Value

Units

Fhead

Flow to Head and upper body

 

ml/min

Fcor

Flow to the heart muscle

 

ml/min

Fkid

Flow to the kidneys

 

ml/min

Fgut

Flow to the gut

 

ml/min

Fliv

Flow to the liver

 

ml/min

Fll

Flow to the lower limbs

 

ml/min

FTOT

Total Flow = Fhead+Fcor+Fkid+Fliv+Fll

 

NOTE: Flows for organs set the flows

for arteries, veins, and summing

junctions.

 

ml/min

wthead

weight of head and upper body

 

g

wtlung

weight of lungs

 

g

wtcor

weight of heart muscle

 

g

wtkid

weight of kidneys

 

g

wtgut

weight of gut

 

g

wtliv

weight of liver

 

g

wtll

weight of lower limbs

 

g

Var[1-4]

Volume of arteries 1 through 4

 

ml

RDar[1-4]

Relative Dispersion of arteries 1 through 4

0.0 - 0.48

unitless

Vvn[1-4]

Volume of veins 1 through 4

 

ml

RDvn[1-4]

Relative Dispersion of veins 1 through 4

0.0 - 0.48

unitless

Cin1, Cin2

Concentration Input functions

 

user's choice

[RA,LA,RV,LV]vol1

[Right atrium, Left atrium, Right

ventricle, Left Ventricle] volume

 

ml

[RV,LV]vol2

[Right ventricle, Left Ventricle]

secondary volume to simulate

incomplete emptying]

 

ml

[RV,LV]K

Transfer coefficient for [right

ventricle, left ventricle]to simulate

incomplete emptying

0

ml/min

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

4. Outputs

Output variables are given by:

Table 2. Body Output Variables

Output Variable

Description

Typical Value

units

Cin1, Cin2

Concentration Input functions (see

XSIM manual)

 

user's choice

chead

Concentration outflow from head and

upper body

 

user's choice

clung

Concentration outflow from lungs

 

user's choice

ccor

Concentration outflow from heart muscle

 

user's choice

ckid

Concentration outflow from kidneys

 

user's choice

cgt

Concentration outflow from guts

 

user's choice

cliv

Concentration outflow from liver

 

user's choice

cll

Concentration outflow from lower limbs

 

user's choice

car[1-4]

Concentration outflow from arteries 1-4

 

user's choice

cvn[1-4]

Concentration outflow from veoms 1-4

 

user's choice

cra

Concentration outflow from right atrium

 

user's choice

crv

Concentration outflow from right ventricle

 

user's choice

cla

Concentration outflow from left atrium

 

user's choice

clv

Concentration outflow from left ventricle

 

user's choice

csum[1-4]

Concentration outflow from summing

junctions 1-4

 

user's choice

crecirc

Concentration outflow about to enter

the system at the point of recirculation

for the next time step

 

user's choice

q[ ... ]

Amount of material in corresponding tissue, artery, vein, atria, ventricle, etc

 

user's choice * ml

qint

The integrated amount of material

entering the system via the two input

functions

 

user's choice * ml

qsystem

The total amount of material in

organs, arteries, veins, and the four

chambers of the heart

 

user's choice * ml

qrecirc

The amount of material outside the

system that re-enters the point of

recirculation during the next time

step. At steady state,

qrecirc=crecirc*FTOT*dt.

With no consumption,

qint=system+qrecirc

 

user's choice * 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. Caveats:

Organs can be bypassed by giving them zero volumes. Their inputs will be passed to their outputs during the time step. Organs can also be bypassed by given them zero flow, in which case nothing will pass through them. Recirculation can be halted in the model by making the final volume in each path before recirculation very large. Large volumes will still accumulate material. The exception to this is the compartmental models for the chambers of the heart--they release material during all time steps (the assumption for compartmental models is that they are well mixed.)

6. Diagrams

 

Heart & Lung Model

R with the oval around it marks the point of recirculation in the model. At each time step, the model begins the calculaiton at this point, and sequentially solves the recirculation problem, organ-by-organ. See note about output variables qsystem, qrecirc, and qint.

7. 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.

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

7.1. A test parameter set with non-physiological values to compare the amount of material in the system (qsystem) plus the amount recirculating (qrecirc) with the amoung injected (qint). : final.test.par

Run model. In the main XSIM window, click on "Results" then choose "Plot Area 1".

(download the parameter file)

7.2. A test parameter set with non-physiological parameter values to illustrate a recirculating vascular bolus injection. : bolus.par

Run model. In the main XSIM window, click on "Results" then choose "Plot Area 1".

(download the parameter file)

 


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