Background: Oxygenation is impaired in almost all subjects during anesthesia, and hypoxemia for shorter or longer periods is a common finding. Moreover, postoperative lung complications occur in 3-10% after elective abdominal surgery and more in emergency operations.
Discussion: Rapid collapse of alveoli on induction of anesthesia and more widespread closure of airways seem to explain the oxygenation impairment and may also contribute to postoperative pulmonary infection. Causative mechanisms to atelectasis and airway closure seem to be loss of respiratory muscle tone and gas resorption.
Conclusion: Avoiding high inspired oxygen fractions during both induction and maintenance of anesthesia prevents or reduces atelectasis, while intermittent "vital capacity" maneuvers recruit atelectatic lung regions.