Effects of different cyclic pressurization and relief patterns on heel skin blood perfusion.

OBJECTIVE
It was hypothesized that a device or support surface providing intermittent cycles of pressurization and pressure relief might minimize the impact of blood flow deficits in the heels resulting from the application of pressure. Because this possibility depends on whether pressure-relief hyperemia can adequately compensate for blood flow deficits, the main objective was to determine how different temporal patterns of pressurization and pressure relief would affect average skin blood perfusion of the heels.

DESIGN
Using a laser Doppler, skin blood perfusion was measured in the heels of 20 healthy subjects while they lay supine for 80 minutes on a support surface. The end cell supporting the heel produced 3 different cyclic patterns of pressurization and either full or partial pressure relief. Each pattern of 1, 2, or 4 cycles was contained within contiguous 20-minute intervals. Skin blood perfusion was determined during full pressurization and during pressure relief for 2 protocols with 10 subjects each.

SETTING
University research center

MAIN OUTCOME MEASURE
Overall average skin blood perfusion in relation to baseline

RESULTS
Full pressure relief yielded a significantly greater skin blood perfusion than partial relief. However, whether pressure relief was full or partial, the average skin blood perfusion of each cyclic pattern was greater than baseline.

CONCLUSION
Consistent with the proposed hypothesis, pressure-relief cycles resulted in an average heel skin blood perfusion that was greater than resting baseline. In the healthy subjects studied, this occurred because hyperemia during pressure relief compensated for flow deficits during pressurization. These results are applicable when the patient is capable of a normal physiologic hyperemic response. The next major investigative challenge is to examine the impact of pressure-relief cycles on patients with diminished hyperemic reserve