Airway pressures and early barotrauma in patients with acute lung injury and acute respiratory distress syndrome

Abstract

The determinants of barotrauma in mechanically ventilated patients with acute lung injury or acute respiratory distress syndrome (ALI/ARDS) have not been clearly established. Using data from ARDS Network randomized controlled trials, we retrospectively examined the association between airway pressures and the risk of early barotrauma in a cohort of 718 patients with ALI/ARDS and no baseline barotrauma. We studied airway pressures at three exposure intervals: baseline, one day preceding the barotrauma event (one-day lag), and concurrent with the barotrauma event. During the first four study days, the cumulative incidence of barotrauma was 13% (95% confidence interval [CI] 10.6 to 15.6%). In a forward stepwise Cox proportional hazards analysis using time-dependent variables, higher concurrent positive end-expiratory pressure (PEEP) was associated with an increased risk of early barotrauma (relative hazard [RH] 1.67 per 5-cm H2O increment; 95% CI 1.35-2.07). Once concurrent PEEP was selected into the model, no other airway pressure was related to barotrauma, including plateau pressure. In the multivariate analysis, higher concurrent PEEP was also related to a greater risk of barotrauma (RH 1.93; 95% CI 1.44-2.60), controlling for age, ventilator group (6 versus 12 ml/kg), baseline PEEP, baseline plateau pressure, baseline tidal volume, Acute Physiology and Chronic Health Evaluation score, vasopressor use, serum albumin, hepatic failure, and coagulopathy. When one-day lagged values of PEEP were analyzed, higher PEEP was associated with a greater risk of barotrauma (RH 1.38 per 5-cm H2O increment; 95% CI 1.09-1.76). Controlling for the covariates, higher PEEP was related to an increased risk of barotrauma (RH 1.50; 95% CI 0.98- 2.30). In conclusion, higher PEEP may increase the likelihood of early barotrauma in ALI/ARDS.