The impaired response of spinal cord injured individuals to repeated surface pressure loads

Three cyclic pressure loads (10 minutes "on" and 5 minutes "off") of 30 or 75 mmHg were applied to the flat anterior surface of the tibia on 11 able bodied (AB) and nine spinal cord injured (SCI) subjects. Transcutaneous PO2 (TcPO2) and PCO2 (TcPCO2), laser Doppler (LD) skin blood flow, velocity, and volume, and the depth of leg indentation (LI) were recorded. In the AB subjects the mean TcPO2 decreased from 31.5 to 27.2 mmHg with the 30 mmHg load. In contrast for the SCI subjects TcPO2 decreased from 32.3 to 7.3 mmHg (significantly differeNt from AB group at p < 0.05). Means of the LD values for volume, velocity, and flow were normalized, giving the highest value of each of the parameters including both the AB and SCI subject during the entire time period a value of 100%. At 30 mmHg loading, the laser LD normalized volume in the AB subjects were 72.5% and 97.0% for the on and off periods, respectively, whereas for the SCI subjects the values were 43.7% and 69.7% for the on and off periods, respectively (significantly different from the AB group at p < 0.05). At 75 mmHg loading, the volume values for the AB subjects were 59.1% and 95.3% for the on and off periods, respectively, whereas for the SCI subjects, the values were 31.6% and 65.4% for the on and off periods, respectively (significantly different from the AB group at p < 0.05).