Background: studies of the effectiveness of alternating pressure air mattresses (APAMs) for the prevention of pressure ulcers are scarce and in conflict.

Objective: evaluating whether an APAM is more or equally effective as the standard prevention.

Design: randomised controlled trial.

Setting and subjects: patients admitted to 19 surgical, internal, or geriatric wards in seven Belgian hospitals were included if they were in need of prevention of pressure ulcers. To define this need, two methods were used randomly: the Braden Scale or the presence of non-blanchable erythema (NBE).

Methods: 447 patients were randomised into either an experimental or a control group. In the experimental group, 222 patients were lying on an APAM (Alpha-X-Cell®, Huntleigh Healthcare, UK). In the control group, 225 patients were lying on a visco-elastic foam mattress (Tempur®, Tempur-World Inc., USA) in combination with turning every 4 hours. Both groups had identical sitting protocols.

Results: there was no significant difference in incidence of pressure ulcers (grade 2–4) between the experimental (15.6%) and control group (15.3%) (P = 1). There were significantly more heel pressure ulcers in the control group (P = 0.006). There was an interaction effect between the risk assessment method and preventive measures for the development of all pressure ulcers and sacral pressure ulcers.

Conclusion: fewer patients developed heel pressure ulcers on an APAM. Patients identified as being in need of prevention based on the presence of NBE had a tendency to develop fewer pressure ulcers on an APAM. Patients identified as being in need of prevention, based on the Braden Scale, appeared to develop more sacral pressure ulcers on an APAM.