Pressure and temperature patterns under the ischial tuberosities

A study was conducted to investigate the pressure relief patterns under the ischial tuberosities in a group of 12 paraplegic subjects. A small electrical pressure transducer was taped over each ischial tuberosity, and each subject had a thermistor taped near one tuberosity. The subjects were instrumented in the morning and allowed to go about their normal activities for the day sitting on a 4-inch foam cushion. The subjects sat at pressures> 150, > 90, > 30 mmHg for 17.6 percent, 53.5 percent, and 91.8 percent of the time, respectively. The subjects sat on the average for 10.1 min without doing a pushup with a duration > 1 sec and sat on the average for 29.6 min without doing a pushup with a duration > 5 sec. Two of the subjects sat for periods > 60 min for > 75 per cent of the time (ignoring pushups <5 sec) and > 65 percent of the time ignoring pushups <1 sec. The average time between pushups was within the generally accepted limits to prevent ulcers - 10-30 minutes. A few of the subjects had occasional long periods of uninterrupted pressure greater than what is thought to be required to produce ulcers - and did not develop them.