[Prevention and therapy of decubitus ulcer. Oxygen availability in the skin as a function of imposed skin pressure].

Pressure is of crucial importance in the formation of decubitus ulcers. In order to elucidate the effect of imposed skin pressure we measured with a new cutaneous oxygen sensor the skin oxygen tension under increasing pressure upon skin tissue on hard sites (bony prominences) and upon soft sites (muscle padded areas). On hard sites the skin oxygen tension fell rapidly under increasing pressure (y = 90.9--0.39 x/r = 0.98) from initially 86.4 +/- 10.6 to 20.2 +/- 12.1 mmHg under an imposing skin pressure of 175 g/cm2. On soft sites a pressure load of 175 g/cm2 decreased the skin oxygen tension only from 82.9 +/- 5.8 to 71.4 +/- 10.0 mmHg. Our results may explain why hard sites (bony prominences) are preferential areas in decubitus ulcer formation.