Gluteal blood flow and oxygenation during electrical stimulation-induced muscle activation versus pressure relief movements in wheelchair users with a spinal cord injury

Background: Prolonged high ischial tuberosities pressure (IT pressure), decreased regional blood flow (BF) and oxygenation (%SO2) are risk factors for developing pressure ulcers (PUs) in patients with spinal cord injury (SCI). Electrical stimulation (ES)-induced gluteal and hamstring muscle activation may improve pressure distribution by changing the shape of the buttocks while sitting and also increase BF and %SO2. Objective: To compare acute effects of ES-induced gluteal and hamstring muscle activation with pressure relief movements (PRMs) on IT pressure, BF and %SO2. Participants and methods: Twelve men with SCI performed PRMs - push-ups, bending forward and leaning sideward - and received surface ES (87 +/- 19 mA) to the gluteal and hamstring muscles while sitting in their wheelchair. Ischial tuberosities pressure was measured using a pressure mapping system; (sub) cutaneous BF and %SO2 were measured using reflection spectroscopy and laser Doppler, respectively. Results: Compared with rest (156 +/- 26 mm Hg), IT pressure was significantly lower during all other conditions (push-ups 19 +/- 44; bending forward 56 +/- 33; leaning sideward 44 +/- 38; ES 67 +/- 45 mm Hg). For the whole group, all PRMs significantly augmented BF (+39 to -96%) and %SO2 (+6.0 to -7.9%-point), whereas ES-induced muscle activation did only for peak BF. In all, 63% of the participants showed an increased BF (average 52%) with ES. Conclusion: PRMs acutely reduced IT pressure and improved oxygenation and BF in SCI. The currently used ES method cannot replace PRMs, but it may be used additionally. ES-induced muscle activation is not as effective for acute pressure relief, but the frequency of stimulation is much higher than the performance of PRMs and can therefore be more effective in the long term