Characterization of the non-linear loading curve of rat skin.

A phenomenological model was developed to characterize the non-linear portion of stress-strain curves for skin tissue removed from laboratory rats and tangent modulus calculations were used to characterize the linear portion of the curves. Modified coefficient of determination calculations obtained from non-linear regression analysis showed that the model was able to fit the actual data above the 90% level. The model coefficients and tangent modulus values were used to statistical comparisons. Combination treatments of radiation, hyperthermia and surgical incision were used to analyze changes in the loading response of rat skin. Least significant difference statistical analysis (P < 0.10) of the model coefficients showed that radiation treatment affected skin stiffness only in tissue when surgical wounding was applied and that radiation-hyperthermia treatment affected skin stiffness only in tissue when surgical wounding was not applied. Hyperthermia applied with no radiation treatment did not affect skin stiffness. Surgical wounding resulted in decreasing skin stiffness.