Pressure ulcer, pressure and flow motion

This article summarized some of our recently published works on the effects of epidermal pressure on skin flowmotion and discussed the implications to the development of pressure ulcer. Studies were conducted in 5 normal subjects and 5 persons with spinal cord injury (SCI). A series of animal studies were conducted using an established rat model. In the human subject study, external pressure of 16.0kPa was applied to the ischial tuberosity for 30 minutes. In anaesthetized rats, external pressure of 13.3kPa was applied to the trochanter area for 6 hours/day for 4 consecutive days. The normalized amplitude of the metabolic component (0.01-0.02 Hz) and neurogenic component (0.02- 0.06 Hz) for persons with SCI was found to be significantly lower during the resting (F=5.26, p=0.032) and post loading conditions (F=5.44, p=0.029) respectively as compared with normal individuals. In anaesthetized rats, prolonged tissue compression induced significant decrease in the normalized amplitude in the frequency interval of 0.01-0.05 Hz in the trochanter area (p<0.001). These findings suggest that the contributions of endothelial related metabolic and neurogenic activities to the blood perfusion regulation became relatively less for persons with SCI during the resting and post loading periods respectively. Also prolonged compression might induce endothelial damage and affect the endothelial related metabolic activities.