Comparison of skin perfusion response with alternating and constant pressures in people with spinal cord injury

Study design:Two-way factorial mixed design, the between-subjects factor as the spinal cord injury (SCI) status (SCI and non-SCI) and the within-subjects factor as the pressure pattern (alternating and constant pressures).Objectives:To compare the effects of alternating and constant pressures on weight-bearing tissue perfusion in people with SCI, with application for improving alternating pressure support surface usage.Setting:University research laboratory.Subjects:A total of 28 participants were studied, 7 participants with cervical injury, 7 participants with injury below T6 and 14 healthy controls.Methods:Sacral skin perfusion was continuously measured using laser Doppler flowmetry under 10 min preloading, 20 min loading (alternating or constant pressures) and 10 min postloading. Alternating pressure was applied with low-interface pressure at 0 mm Hg and high-interface pressure at 60 mm Hg with a cycle time of 5 min; constant pressure was applied with interface pressure at 30 mm Hg.Results:The results showed that pressure pattern affects skin perfusion responses in weight-bearing tissues (P<0.01). Alternating pressure stimulates an increase in skin perfusion (1.21±0.08 au) as compared with constant pressure (0.74±0.07 au) in people with SCI (P<0.01). There was no overall difference in the skin perfusion responses of patients with SCI as compared with non-SCI patients (P>0.05).Conclusion:This study has shown that alternating pressure enhances the skin perfusion of weight-bearing tissues as compared with constant pressure in people with SCI. The protocol tested in this study may be used to guide the selection of parameters of commercial alternating pressure support surfaces for preventing pressure ulcers in people with SCI.