Temperature effects on surface pressure-induced changes in rat skin perfusion: Implications in pressure ulcer development

The effect of varying local skin temperature on surface pressure-induced ch anges in skin perfusion and deformation was determined in hairless fuzzy ra ts (13.5+/-3 mo, 474+/-25 g). Skin surface pressure was applied by a comput er-controlled plunger with corresponding skin deformation measured by a lin ear variable differential transformer while a laser Doppler flowmeter measu red skin perfusion. In Protocol I, skin surface perfusion was measured with out heating (control, T=28 degrees C), with heating (T=36 degrees C), for c ontrol (probe just touching skin, 3.7 mmHg), and at two different skin surf ace pressures, 18 mmHg and 73 mmHg. Heating caused perfusion to increase at control and 18 mmHg pressure, but not at 73 mmHg. In Protocol II, skin per fusion was measured with and without heating as in Protocol I, but this tim e skin surface pressure was increased from 3.7 to 62 mmHg in increments of 3.7 mmHg, For unheated skin, perfusion increased as skin surface pressure i ncreased from 3.7 to 18 mmHg. Further increases in surface pressure caused a decrease in perfusion until zero perfusion was reached for pressures over 55 mmHg. Heating increased skin perfusion for surface pressures from 3.7 t o 18 mmHg, but not for pressures greater than 18 mmHg. After the release of surface pressure, the reactive hyperemia peak of perfusion increased with heating. In Protocol III, where skin deformation (creep and relaxation) was measured during the application of 3.7 and 18 mmHg, heating caused the tis sue to be stiffer, allowing less deformation. It was found that for surface pressures below 18 mmHg, increasing skin temperature significantly increas ed skin perfusion and tissue stiffness. The clinical significance of these findings may have relevance in evaluating temperature and pressure effects on skin blood flow and deformation as well as the efficacy of using tempera ture as a therapeutic modality in the treatment of pressure ulcers.