Figure 1.
Hybrid model of pressure ulcer formation.
The model representation of the pressure ulcer formation process is shown.
Figure 2.
Components of the hybrid model of pressure ulcer formation.
Panel (A) shows interactions between main components of the model. Panel (B) demonstrates the connection between ODE and ABM portions of the model. Geometric shapes represent model components. Arrows show interactions between components. “Mac” in the figure represents inflammatory cells (nominally macrophages).
Figure 3.
Circuit model of the blood flow.
R (resistance) represents vascular resistance, C (capacitance) represents vessel compliance, V(t) represents the input blood flow pressure, and I (current) represents blood flow. I2(t) represents the skin blood flow.
Figure 4.
Average reactive hyperemia blood flow data.
Raw blood flow data was filtered with low pass filters. The filtered data was averaged over all six subjects in each group. Panel (A) shows the averaged data for people with SCI. Panel (B) shows the averaged data for people without SCI.
Figure 5.
Fitted results for average reactive hyperemia.
The explicit expression of I2(t) was used for finding best-fit results. Calibration was performed using Matlab R2011. Panel (A) shows the best-fit result in people with SCI. Panel (B) shows the best-fit result in people without SCI.
Figure 6.
Best-fit parameter ratios for the differential equation part of the model.
The x-axis shows the parameter names, and y-axis shows the ratios of parameters for people with and without SCI. The explicit expression of I2(t) was used for finding best-fit parameters.
Table 1.
Values of the best-fit parameters for control and SCI groups.
Figure 7.
Simulation snapshots after 2000 steps.
Green squares represent healthy epithelial cells, red squares represent damaged epithelial cells, red circles represent blood vessels, blue circles represent macrophage, and white squares represent the dead cells. Panel (A) shows the simulation result for the control group with the pressure interval = 210. Panel (B) shows the simulation result for the SCI group with the pressure interval = 107.
Table 2.
Subject-specific minimal value of the pressure interval that would be predicted to result in substantial tissue damage.
Figure 8.
Simulation of different pressure scales on the health of epithelial cells.
Graphs with different values of the pressure interval show how the predicted health of epithelial cells progresses over time for simulations of the control and SCI groups, respectively. Panel (A) shows the outcome of simulations for the control group. Panel (B) shows the outcome of simulations for the SCI group.