Therapeutic value of a lung protective ventilation strategy in acute lung injury.

B oth observational and epidemiologic studies have identified clinical variables associated with a higher risk of mortality in patients with acute lung injury. The most consistent clinical risk factors for higher mortality have been sepsis as the cause of lung injury, chronic liver disease, underlying malignancy, older age, and higher severity of illness assessed by elevated acute physiology and chronic health evaluation or simplified acute physiology scores.1–5 However, there is little information regarding the impact of supportive care therapies on outcomes in patients with acute lung injury. In this issue of CHEST (see page 3098), Sakr et al6 reports the results of an observational study carried out in 198 European ICUs that participated in the Sepsis Occurrence in Acutely Ill Patients study. All 3,147 adult patients admitted to participating ICUs in Europe during a consecutive 2-week period in 2002 were included in the study population; of this group, 393 patients had either acute lung injury or ARDS. The investigators tested the hypothesis that sepsis and the use of tidal volumes higher than those applied in the National Heart, Lung, and Blood Institute (NHLBI) ARDS Network (ARDSnet) study,7 ( 7.4 mL/kg of predicted body weight [PBW]), would be associated with mortality in patients with acute lung injury. A total of 207 patients (53% of the sample with acute lung injury) received mechanical ventilation at least once during their clinical course of acute lung injury with a tidal volume different from the ARDSnet strategy.7 Higher tidal volumes ( 7.4 mL/kg of PBW) were more common in nonsurvivors than in survivors (44% vs 34%, p 0.019), and a multivariate analysis confirmed that the use of higher tidal volumes was an independent predictor of ICU mortality, with an odds ratio for death of 2.3 (95% confidence interval, 1.2 to 4.4; p 0.01). Other independent risk factors for ICU mortality included the presence of cancer, the degree of multiorgan dysfunction, and higher mean fluid balance. Sepsis was not an independent predictor of mortality; however, the authors hypothesize that multisystem organ failure is the true cause of increased mortality from sepsis rather than the infection itself. These data appear to confirm the results of the NHLBI ARDSnet clinical trial,7 which reported that ventilation of acute lung injury patients with a tidal volume of 6 mL/kg of PBW reduced hospital mortality to 31%, compared to a mortality of 40% in patients receiving mechanical ventilation with a traditional tidal volume of 12 mL/kg of PBW. A follow-up study8 by the ARDSnet has provided additional evidence that mortality has declined further to 26% with the use of the lower tidal volume, even though higher levels of positive end-expiratory pressure did not reduce mortality. Although the results of the current study are interesting, there are some shortcomings to the study design, as the authors acknowledge. First, this was not a randomized trial testing different ventilation CHEST editorials