Head-of-bed elevation in critically ill patients: a review. 
Clinicians are confused by conflicting guidelines about the use of head-of-bed elevation to prevent aspiration and pressure ulcers in critically ill patients.  Research-based information in support of guidelines for head-of-bed elevation to prevent either condition is limited.  However, positioning of the head of the bed has been studied more extensively for the prevention of aspiration than for the prevention of pressure ulcers, especially in critically ill patients.  More research on pressure ulcers has been conducted in healthy persons or residents of nursing homes than in critically ill patients.  Thus, the optimal elevation for the head of the bed to balance the risks for aspiration and pressure ulcers in critically ill patients who are receiving mechanical ventilation and tube feedings is unknown.  Currently available information provides some indications of how to position patients; however, randomized controlled trials where both outcomes are evaluated simultaneously at various head-of-bed positions are needed.