Lung reaeration after surfactant instillation - caused by surfactant or caused by instillation?

signifi cant and prolonged lung reaeration after intratracheal bolus instillation of porcine-derived surfactant. In this substudy of a larger randomized controlled trial of patients with acute lung injury [2], the investigators elegantly demonstrate increased volumes of gas in poorly and non-aerated lung of patients who were treated with surfactant as compared with patients who received routine care. Do these encouraging fi ndings truly support the rationale for exogenous surfactant replacement as an indication for lung reaeration in patients with acute lung injury? Th is can be questioned. First, intratracheal bolus instillation of surfactant required recruitment maneuvers. Indeed, larger tidal volumes (TVs) and higher levels of positive end-expiratory pressure (PEEP) were used for as long as 30 minutes after instillation of surfactant to each lung. Th e instillation procedure per se could be (solely) responsible for increased volumes of gas in poorly and non-aerated lung. In addition, bolus instillation of surfactant resulted in temporarily severe hypoxemia in more than half of the patients treated with surfactant [2]. Th ough not reported in the original study or the present study, rescue therapies such as prone ventilation, repeated recruitment maneuvers, and higher levels of PEEP could have been used more intensively in these patients. Th ese rescue maneuvers, in response to surfactant instillation-induced hypoxemia, could also be responsible for the fi ndings by Lu and colleagues [1].