Skin vascular reaction to standard patient positioning on a hospital mattress.

The effects of duration and posture on reactive hyperemia in the skin overlying the greater trochanter of the femur was determined in normal subjects using thermography. Multivariate analysis revealed that in the six subjects studied, post-lying blood flow within the skin superficial to bony prominences was significantly increased over that of the preexperimental and passively-warmed controls. These analyses also showed that both maximal interface pressures and vascular reactions were experienced in the side-lying position when the legs were extended, and significantly reduced when the legs were flexed. While there was good correlation between magnitudes of interface pressures measured and vascular responses within each individual, there was no such direct correlation between individuals. The individual with the highest interface pressures did not have the most intense reactive hyperemic reactions, and the individual with the least interface pressures did not have the least intense reactive hyperemic reactions. Intrinsic features of each individual's vascular response to the normal mechanical forces experienced during lying appear to be a sensitive measure of the individual's susceptibility to develop pressure ulcers.