Response to: Do initial tidal volumes impact acute respiratory distress syndrome development in patients intubated in the emergency department?

Abstract

tion for patients intubated in the ED. We believe the editorial misstates our main conclusion. We primarily found that, in the subset of patients in whom the ARDS developed, initial tidal volumes were higher than the recommended tidal volume of 6 mL/kg of ideal body weight (IBW) [1]. Our study was not designed to show causality between higher initial ventilator settings and the subsequent development of ARDS. Rather, we selected the subset of patients in whom ARDS later developed because they are the patients in whom tidal volumes are felt to be most important. Lung-protective ventilation with a recommended tidal volume of 6 mL/kg has been commonly adopted for all comers since the And Respiratory Management in ARDS (ARMA) trial from the ARDS Network [1] .I n that prospective, randomized trial, the patients seeing a mortality benefit from lung-protective tidal volume ventilation were those who had ARDS. We therefore chose to look at this specific population by including only patients who developed ARDS within 48 hours after intubation. We sought to determine if the ED-initiated ventilator settings in this subset adhered to the goal of 6 mL/kg IBW and found that the volumes were set higher by approximately 1.5 mL/kg of IBW. Importantly, the assertion that the ARMA trial protocol called for an initial tidal volume of 8 mL/kg IBW is somewhat misleading. The protocol does call for an “initial” tidal volume of 8 mL/kg IBW but then states that this tidal volume “will be reduced by 1 mL/kg IBW at intervals of less than or equal to 2 hours until tidal volume equals to 6 mL/kg IBW,” at which point further adjustments would be made for acidosis, hypoxia, and plateau pressures. We did not findthat this titration occurredin our cohort. For patientswho were eventually ventilated at 6 mL/kg IBW, an average of 14 hours passed before they reached this goal. Furthermore, the same protocol states that the tidal volume could be increased above 6 mL/kg only in the setting of severe acidosis (pH b7.15) that persisted despite a respiratory rate of 35