Critical analysis of the factors associated with enteral feeding in preventing VAP: a systematic review

Ventilator-associated pneumonia (VAP) is a common cause of morbidity in critically ill patients. Appropriate enteral feeding is the most important factor associated with the prevention of VAP. However, the standardization of enteral feeding methods needs clarification. The purpose of this systematic review was to synthesize the factors associated with enteral feeding in order to prevent VAP and to describe the characteristics of these factors. A comprehensive search was undertaken involving all major databases from their inception to September 2008 using medical subject heading terms associated with enteral feeding in relation to VAP. The overall reference list of identified studies was audited, and eligible studies included randomized controlled trials, controlled before-and-after (pre-post) studies and meta-analyses. To generate the characteristics of the factors associated with VAP, the reported components of these trials were pinpointed and categorized. A total of 14 papers were found that had investigated the factors linking enteral feeding and VAP. For these, 11 were randomized controlled trials, 1 was a meta-analysis and 2 were case-controlled analyses. Twelve of these 14 studies were conducted at a single institute and 2 were conducted at multiple institutes. The sample sizes varied from 10 to 2,528 subjects. Three major issues were identified based on the purpose of study interventions, and these were the effects of feeding method (continuous vs. intermittent), feeding site on aspiration (gastric vs. small bowel), and the timing of enteral feeding (early vs. late). The evidence suggests that a correct choice of enteral feeding method can effectively reduce complications due to aspiration. Furthermore, intermittent enteral feeding and with a small residual volume feed can reduce gastroesophageal reflux, and increased total intake volume and early feeding can reduce ICU mortality. Nonetheless, the effects of these choices on preventing VAP still need further evaluation. A set of clinical guidelines based on these evidence-based findings with respect to enteral feeding is required, particularly one that covers all aspects of the enteral feeding process.