Positive End-expiratory Pressure and Postoperative Atelectasis

Abstract

Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New 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.

Perioperative Pulmonary Atelectasis: Part II. Clinical Implications

“…Emergence from anesthesia and extubation may hasten alveolar derecruitment. 94,103,147,153,236 Specifically, high pre-extubation Fio 2 has been associated with absorption atelectasis. 237,238 Yet the clinical impact on postoperative outcomes is unknown, and safety issues related to shortening desaturation time with Fio 2 less than 1.0, such as for difficult extubations, should be considered.…”

Pressure Support versus Spontaneous Ventilation during Anesthetic Emergence—Effect on Postoperative Atelectasis: A Randomized Controlled Trial

“…6,7 Furthermore, it is estimated that the emergence period contributes to approximately 39% of the total amount of postoperative atelectasis. 7 Currently, we allow patients to breathe spontaneously and assist their respiration intermittently during the transition from controlled ventilation to spontaneous respiration while assessing whether the patients have enough power to breathe without assistance. However, patients who are spontaneously breathing remain under the influence of residual anesthetic agents and neuromuscular blockers and may not have restored their functional residual capacity, 8,9 subsequently developing atelectasis.…”

Systematic review and meta-analysis on perioperative intervention to prevent postoperative atelectasis complications after thoracic surgery

“…Interventions are diverse, including preemptive strategies (before surgery) to optimize respiratory physiology, and intraoperative and postoperative interventions to minimize the adverse effects of surgery and anesthesia (10). The treatment of PPCs requires the multidisciplinary participation of anesthesia, surgery, respiratory medicine, physical therapy, and intensive care professionals, and bears the burden of related economic and health outcomes (11,12). Nevertheless, compared with postoperative cardiovascular complications, consensus guidelines for perioperative management to reduce the risk of PPCs are still rare.…”