Surface pressure distribution of the human body in the recumbent position

Surface pressure measurements of human body weight as distributed on 4 different commercial beds were examined. Sixty-five water-filled bladders connected to pressure transducers were employed to measure the pressure distribution patterns of the human body. These pressure measuring bladders were distributed on a sheet shaped to conform to the human figure and then placed on 5 different surfaces, including an orthopedic 720 coil mattress and box spring, a standard 500 coil bed, a standard 10-inch deep waterbed, a hybrid bed composed of a central water core surrounded by polyurethane, and the floor. Subjects were tested in both a supine and prone position on the various surfaces after the pressure measuring sheet was interposed. The results demonstrated a more uniform pressure distribution over the entire body on both the waterbed and the orthopedic bed than on any of the other surfaces. The softer (500 coil) bed, the hybrid bed, and the floor supported the body essentially on only 5 points (occiput, shoulders, buttocks, calves and heels) in the supine position. The water and orthopedic beds differed markedly, having more uniform and equally distributed surface pressures. The skin pressures measured over the bony prominences were significantly greater than the critical value for ischemia (30mmHg), thereby enhancing the development of decubiti--particularly in the beds which poorly distribute body weight.