Thermal response of skin to cyclic pressure and pressure with shear: A technical note

The thermal response of skin to pressure alone and to pressure with shear w as compared under cyclic loading conditions. Stresses were applied to the a nterior aspect of the leg of three healthy subjects for time intervals up t o 10 min, and the difference in temperature between the stressed site and a contralateral control site was assessed after load release. The thermal re covery time (TRT), the time interval between load release and either a maxi mum or a stabilization in the temperature difference vs, time record was de termined. Results demonstrated that for a resultant stress of 142.9 kPa, TR Ts were longer for combined pressure and shear than for pressure alone. For Subjects A, B, and C, TRT increases were 1.5 min, 5.5 min, and 2.0 min res pectively. For a resultant stress magnitude of 71.4 kPa, increases were 1.5 min, 3.5 min, and -0.5 min respectively. Comparing responses for different resultant stress magnitudes for pressure-only application, TRTs were 1.5 m in, 1.5 min, and 5.5 min longer for the 142.9-kPa condition than for the 71 .4-kPa condition for Subjects A, B, and C. For combined pressure and shear, increases were 1.5 min, 3.5 min; and 8.0 min respectively. A next step wil l be to determine if the TRT differences measured here are physiologically relevant and have clinical meaning. The thermal response assessment method could then potentially be used to quantitatively evaluate the effects of di fferent interface design features in lower-limb prosthetics on tissue respo nse.