Preventing pressure ulcers by increasing pressure: An unorthodox alternating-pressure mattress

Despite the devastating effects of pressure ulcers (PUs), little is understood about how they can be prevented using alternating-pressure (AP) mattresses. Such mattresses typically aim to minimize the pressures imparted while alternating between different states of pressure to prevent areas of tissue from being persistently occluded of blood flow. In this work, we built an actuator bed to study AP approaches and learned that AP mattresses should aim to increase-not decrease-peak pressures to a certain extent if such areas are to be minimized for effectively preventing PUs. In addition, we learned that such mattresses should aim to increase the difference between their loading and off-loading pressures. We identified optimal parameters from the study and used them to design an AP mattress made of compliant mechanisms that markedly reduce areas of persistent occlusion by exhibiting relatively high peak pressures that are periodically alternated with substantially lower off-loading pressures. The mattress's performance was characterized and compared against a standard foam pad in its flat and raised configurations. The load required to actuate the mattress from one of its stable states of pressure to the other was also measured.