• beds;
  • clinical trials;
  • intensive care unit;
  • mechanical ventilation;
  • nursing;
  • pressure ulcers;
  • prevention



To compare the effectiveness of alternating pressure air mattresses vs. overlays to prevent pressure ulcers in mechanically ventilated patients in intensive care units.


Pressure ulcers prevention is an important issue in the nursing of critically ill patients. It is not clear whether alternating pressure air mattresses are more effective than overlays to prevent pressure ulcers.


Prospective quasi-experimental study.


A prospective quasi-experimental study was conducted among patients in the medical–surgery intensive care unit of a university hospital on mechanical ventilation ≥24 hours during two time periods (2001 and 2006). Overlays were used in 2001 and mattresses in 2006. Primary outcome was the incidence of pressure ulcers grade ≥II (according to the European Pressure Ulcer Advisory Panel) during intensive care unit stay.


The study included 221 patients (116 in 2001 and 105 in 2006). Baseline characteristics were similar between groups except for a higher Acute Physiology and Chronic Health Evaluation III score, total and first-day respiratory Sequential Organ Failure Assessment Score on day 1 in overlay group. There was significantly lower incidence density in the mattress vs. overlay group (12·41 cases/1000 days vs. 18·67 cases/1000 days of stay). The multivariate analyses showed the use of the mattress to be a protective factor against pressure ulcer onset.


This quasi-experiment study that alternative pressure air mattresses were more effective than alternating pressure air overlays in preventing pressure ulcers in mechanically ventilated critical care patients.