Newly Published
Perioperative Medicine  |   May 2019
Positive End-expiratory Pressure and Postoperative Atelectasis: A Randomized Controlled Trial
Author Notes
  • From the Departments of Anesthesia and Intensive Care (E.Ö., L.E.) and Radiology (A.T.) and the Center for Clinical Research (M.E.), Västerås Hospital, Västerås, Sweden; the Department of Anesthesia and Intensive Care, Köping County Hospital, Köping, Sweden (E.Ö., L.E.); the Department of Surgical Sciences, Anesthesiology and Intensive Care (H.Z.) and the Department of Medical Sciences and Clinical Physiology (G.H.), Uppsala University, Uppsala, Sweden.
  • Submitted for publication October 31, 2018. Accepted for publication March 28, 2019.
    Submitted for publication October 31, 2018. Accepted for publication March 28, 2019.×
  • Correspondence: Address correspondence to Dr. Östberg: Västerås Hospital, 721 89 Västerås, Sweden. erland.ostberg@regionvastmanland.se. Information on purchasing reprints may be found at www.anesthesiology.org or on the masthead page at the beginning of this issue. Anesthesiology’s articles are made freely accessible to all readers, for personal use only, 6 months from the cover date of the issue.
Article Information
Perioperative Medicine / Respiratory System
Perioperative Medicine   |   May 2019
Positive End-expiratory Pressure and Postoperative Atelectasis: A Randomized Controlled Trial
Anesthesiology Newly Published on May 14, 2019. doi:10.1097/ALN.0000000000002764
Anesthesiology Newly Published on May 14, 2019. doi:10.1097/ALN.0000000000002764
Abstract

Editor’s Perspective:

What We Already Know about This Topic:

  • Positive end-expiratory pressure (PEEP) is used during anesthesia to prevent atelectasis, but its impact during emergence from anesthesia is uncertain.

What This Article Tells Us That Is New:

  • Thirty patients undergoing nonabdominal surgery under general anesthesia were randomized to maintained (7 or 9 cm H2O) or zero PEEP before being given 100% oxygen for emergence preoxygenation. Postoperative atelectasis (assessed by computed tomography) was small with no effect on oxygenation, whether or not PEEP was used during emergence.

Background: Positive end-expiratory pressure (PEEP) increases lung volume and protects against alveolar collapse during anesthesia. During emergence, safety preoxygenation preparatory to extubation makes the lung susceptible to gas absorption and alveolar collapse, especially in dependent regions being kept open by PEEP. We hypothesized that withdrawing PEEP before starting emergence preoxygenation would limit postoperative atelectasis formation.

Methods: This was a randomized controlled evaluator-blinded trial in 30 healthy patients undergoing nonabdominal surgery under general anesthesia and mechanical ventilation with PEEP 7 or 9 cm H2O depending on body mass index. A computed tomography scan at the end of surgery assessed baseline atelectasis. The study subjects were thereafter allocated to either maintained PEEP (n = 16) or zero PEEP (n = 14) during emergence preoxygenation. The primary outcome was change in atelectasis area as evaluated by a second computed tomography scan 30 min after extubation. Oxygenation was assessed by arterial blood gases.

Results: Baseline atelectasis was small and increased modestly during awakening, with no statistically significant difference between groups. With PEEP applied during awakening, the increase in atelectasis area was median (range) 1.6 (−1.1 to 12.3) cm2 and without PEEP 2.3 (−1.6 to 7.8) cm2. The difference was 0.7 cm2 (95% CI, −0.8 to 2.9 cm2; P = 0.400). Postoperative atelectasis for all patients was median 5.2 cm2 (95% CI, 4.3 to 5.7 cm2), corresponding to median 2.5% of the total lung area (95% CI, 2.0 to 3.0%). Postoperative oxygenation was unchanged in both groups when compared to oxygenation in the preoperative awake state.

Conclusions: Withdrawing PEEP before emergence preoxygenation does not reduce atelectasis formation after nonabdominal surgery. Despite using 100% oxygen during awakening, postoperative atelectasis is small and does not affect oxygenation, possibly conditional on an open lung during anesthesia, as achieved by intraoperative PEEP.