| Decubitus ulcers are major complications of tissue necrosis associated with spinal cord injury and the elderly who suffer from diminished pain sensation and/or diminished mobility. This study was composed of two parts. The first part aimed to investigate the movement of the ischial tuberosities (IT) and the redistribution of interface pressure during manual wheelchair propulsion. In the second part of the study, post-occlusive hyperaemia after three different loading regimes, namely (static) pressure only; combination of pressure and shear, and (dynamic) combination of pressure and cyclic shearing, were evaluated. Repeated measures ANOVA were used to compare the measured parameters in these experiments.; In the first part of the study, the three dimensional position of the pelvis was measured with an optical motion analysis system (Vicon 370, UK). Interface pressure was measured by a thin, flexible pressure mat (Tekscan, USA). Spatial resolution of the pressure mat was 3.2 sensors/cm 2. The two systems were synchronized to capture data at 60 Hz. The participants were measured in a manual wheelchair with a rigid seat support. Propulsion cycles were performed on a stationary wheelchair ergometer at the subject's maximum propulsion speed. The results indicated that during wheelchair sprinting, the predicted position of the ischial tuberosity based on the pelvic markers did not concur exactly with the corresponding peak pressure locations as measured by the pressure mat.; In the second part of the study, tissue reperfusion after loading was measured using a laser Doppler perfusion imager (Moor Instrument, UK). Three different loading sites were evaluated including the forearm, the greater trochanter and the ischial tuberosity. Spatial hyperaemic changes in blood perfusion were characterized in terms of their magnitude, half-life, as well as the perfusion-time integral (total hyperaemia). The results indicated that resting skin blood flow at the trochanter area was found to be higher in the normal group as compared to the wheelchair user group.; Experimental results suggested that combination of pressure and shear stress could cause a higher distress to tissue than with pressure alone. It was also found that dynamic loading with cyclic shear could cause high distress to the involved tissue, which apparently required a prolonged period to recover. (Abstract shortened by UMI.)... |
