• Gaku Kawamura, Takayuki Kitamura, Ikuo Homma, and Yoshitsugu Yamada.
• Department of Anesthesiology, Faculty of Medicine, The University of Tokyo, Tokyo 113-8655.
• Masui. 2013 Jun 1; 62 (6): 652-9.

BackgroundThe use of positive end-expiratory pressure (PEEP) is a practical intervention to improve oxygenation during anesthetic management; however, the underlying mechanisms have not been elucidated.MethodsParameters of ventilator settings and results of arterial blood gas analyses were collected from medical records of adult patients undergoing surgery under general anesthesia with pressure-controlled ventilation in our hospital from January 2009 to March 2010. We analyzed the changes in dynamic compliance (Cdyn) and alveolar-arterial oxygen difference (A-aDo2).ResultsA total of 139 patients were enrolled; anesthesia was maintained with sevoflurane in 82 patients, and with propofol in 57 patients. After the application of PEEP, significant decreases in A-aDo2 were accompanied with significant increases in Cdyn under sevoflurane anesthesia. However, significant decreases in A-aDo2 were not always accompanied by significant increases in C(dyn) under propofol anesthesia.ConclusionsThese results suggest that the mechanisms for improved oxygenation by PEEP under sevoflurane anesthesia are different from those under propofol anesthesia. The improved oxygenation after the application of PEEP under sevoflurane anesthesia is mainly due to reduction of atelectasis, whereas reduction of atelectasis as well as reduction of intrapulmonary shunt is associated with the improved oxygenation after the application of PEEP under propofol anesthesia.

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