Nitrous oxide (N2O) promotes absorption atelectasis in poorly ventilated lung segments at high inspired concentrations. The original ENIGMA Trial found a higher incidence of postoperative pulmonary complications and wound sepsis with N2O anesthesia in major surgery compared with Fio2 0.8 without N2O. In this issue of Anesthesiology, Peyton et al. collected post hoc data to determine whether the incidences of atelectasis and pneumonia were higher with in patients receiving N2O who were recruited to the Australian cohort of the ENIGMA II trial. In an accompanying editorial, Gama de Abreu and Sessler discuss the conflicting evidence on nitrous oxide and postoperative pulmonary complications. Cover illustration: A. Johnson, Vivo Visuals Studio.

  • Peyton et al.: Postoperative Pulmonary Complications in the ENIGMA II Trial: A Post Hoc Analysis, p. 354

  • Gama de Abreu and Sessler: Nitrous Oxide and Postoperative Pulmonary Complications: Conflicting Evidence, p. 345