Efficacy of low tidal volume ventilation in patients with different clinical risk factors for acute lung injury and the acute respiratory distress syndrome

In patients with acute lung injury (ALI) and acute respiratory distress syn drome (ARDS), a recent ARDS Network randomized controlled trial demonstrate d that a low tidal volume (VT) mechanical ventilation strategy (6 ml/kg) re duced mortality by 22% compared with traditional mechanical ventilation (12 ml/kg). In this study, we examined the relative efficacy Of low VT mechani cal ventilation among 902 patients with different clinical risk factors for AWARDS who participated in ARDS Network randomized controlled trials. The clinical risk factor for ALI/ARDS was associated with substantial variation in mortality. The risk of death (before discharge home with unassisted bre athing) was highest in patients with sepsis (43%); intermediate in subjects with pneumonia (36%), aspiration (37%), and other risk factors (35%); and lowest in those with trauma (11%) (p < 0.0001). Despite these differences i n mortality, there was no evidence that the efficacy of the low VT strategy varied by clinical risk factor (p = 0.76, for interaction between ventilat or group and risk factor). There was also no evidence of differential effic acy Of low VT ventilation in the other study outcomes: proportion of patien ts achieving unassisted breathing (p = 0.59), ventilator-free days (p = 0.5 8), or development of nonpulmonary organ failure (p = 0.44). Controlling fo r demographic and clinical covariates did not appreciably affect these resu lts. After reclassifying the clinical risk factors as pulmonary versus nonp ulmonary predisposing conditions and infection-related versus non-infection -related conditions, there was still no evidence that the efficacy Of low V T ventilation differed among clinical risk factor subgroups. In conclusion, we found no evidence that the efficacy of the low VT ventilation strategy differed among clinical risk factor subgroups for ALI/ARDS.