The Analysis Subsystem
Below is the block diagram for the Analysis Subsystem. All tweaking of the heart beat (compliance), parameter viewing at run time, and sorting of output data is done from this subsystem.
Figure 1. SIMULINK 2.0 block diagram of the Analysis Subsystem.
Physiological notes:
- The three To Workspace blocks at the bottom of the block diagram save blood volume, internal pressure, and input pressure for each of the nine subsystems. This data is available in the variables volume, pressure, and pin, respectively
- Unlike the plot shown in the original PHYSBE article [1], the compliance pattern is different for the right and left ventricles. The compliance values used in this example came from the DARE/PHYSBE article[2] and are shown below in table 1.
Time 0 0.04 0.08 0.12 0.16 0.20 0.24 0.28 0.32 0.36 0.40 1 1/C1 0.0033 0.05 0.10 0.15 0.17 0.24 0.30 0.36 0.40 0.30 0.0033 0.0033 1/C3 0.0066 0.60 1.00 1.25 1.40 1.50 1.60 1.60 1.50 1.00 0.0066 0.0066 Table 1. Compliance values for right (C1) and left (C3) ventricles.
Simulation notes:
- Goto and From blocks are used extensively to allow key output and input information to be passed directly to or from the appropriate subsystem. This allows the heartbeat for both left and right ventricle to be input at one location. It also allows key data to be gathered from all subsystems and muxed into three vectorized To Workspace blocks without having lines crisscrossing all over the place on the main block diagram.
- The new SIMULINK integrator yields better accuracy, allowing the simulation to run with a maximum step size greater than prescribed by McLeod. The integrator automatically reduces the step size at non-linearities in order to maintain accuracy levels specified in the simulation parameters.
- The new To Workspace blocks aid in data reduction by decimating the output data before writing it to the MATLAB workspace. The output has been subsampled at every 10th time-step, as shown in the To Workspace dialogue box for volume data, given in figure 2.
Figure 2. To Workspace dialog box.
- The new Scope block, shown in figure 3, makes viewing data during run-time much easier, with:
- x and y axis labels
- full zoom, plus zoom x-axis only and zoom y-axis only modes
- auto-zoom button to fit all data onto scope
- fix-axes button to freeze current axis limits as defaults for the scope
- a full parameter dialog box to adjust axis limits explicitly, as well as other features (shown below).
Figure 3. Scope block
References
- McLeod J, PHYSBE...a physiological simulation benchmark experiment, SIMULATION, vol.7, no.6, 324-329, 1966.
- Korn G, McLeod J, Wait J, DARE/PHYSBE, SIMULATION, 229-231, Nov. 1970.
