Background In acute respiratory distress syndrome, minimizing lung injury from repeated collapse and reopening of alveoli by applying a high positive end-expiratory pressure improves oxygenation without influencing mortality. Obesity causes alveolar atelectasis, thus suggesting that a higher positive end-expiratory pressure might be more protective among the obese. We hypothesized that the effect of applying a high positive end-expiratory pressure on mortality from acute respiratory distress syndrome would differ by obesity status. Methods This was a retrospective analysis of 505 patients from the Assessment of Low tidal Volume and elevated End-expiratory volume to Obviate Lung Injury Trial, a multicenter randomized trial that compared a higher vs a lower positive end-expiratory pressure ventilatory strategy in acute respiratory distress syndrome. We examined the relationship between positive end-expiratory pressure strategy and 60-day mortality stratified by obesity status. Results Among obese patients with acute respiratory distress syndrome, those assigned to a high positive end-expiratory pressure strategy experienced lower mortality compared with those assigned to a low strategy (18% vs 32%; P =.04). Among the nonobese, those assigned to high positive end-expiratory pressure strategy experienced similar mortality with those assigned to low strategy (34% vs 23%; P = .13). Multivariate analysis demonstrated an interaction between obesity status and the effect of positive end-expiratory pressure strategy on mortality (P <.01). Conclusions Ventilation with higher levels of positive end-expiratory pressure was associated with improved survival among the subgroup of patients with acute respiratory distress syndrome who are obese.
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