The effects of different respiratory maneuvers on Pao2, Qs/Qt, and cardiac output were studied during one-lung anesthesia in 21 adult patients undergoing pulmonary surgery in lateral position with halothane-oxygen anesthesia using endobronchial intubation. The patients were divided into three groups. In group A (n = 11) seven different respiratory maneuvers were sequentially performed. When both lungs were ventilated (maneuver A) Pao2 and Qs/Qt were 376 ± 28 torr (mean ± SE) and 26 ± 2.33% (mean ± SE), respectively. Corresponding values were 155 ± 25 torr and 38 ± 1.5% when the upper lung was deflated (maneuver B) and 85 ± 11 torr and 44 ± 4% when PEEP (10 cm H2O) was added to the dependent lung with the upper lung remaining deflated (maneuver C). When the collapsed upper lung was insufflated with oxygen (7 L/min) with the lower lung receiving PEEP (maneuver D) Pao2 and Qs/Qt were 127 ± 29 torr and 38 ± 3%, respectively, 177 ± 34 torr and 37 ± 3.5% when the upper lung was insufflated with oxygen and lower lung ventilated without end-expiratory pressure (maneuver E). When the upper lung was insufflated with oxygen at 10 cm H2O pressure with the dependent lung ventilated with PEEP (maneuver F), Pao2 was 248 ± 41 torr and Qs/Qt was 31 ± 2% and finally, during insufflation of the upper lung at 10 cm H2O pressure while the lower lung was ventilated with zero end-expiratory pressure (maneuver G) Pao2 averaged 286 ± 49 torr and Qs/ Qt 28 ± 2.5%. Cardiac output was reduced only when the dependent lung was ventilated with PEEP and the deflated upper lung insufflated with oxygen with or without pressure. In group B (n = 5) the effects of only maneuver F on arterial oxygenation were evaluated 50, 95, and 140 minutes after the start of anesthesia. In group C (n = 5), only maneuver G was studied 50, 95, and 140 minutes after the start of anesthesia. The values for Pao2 and Qs/Qt did not differ from each other at these time intervals and were comparable with the values obtained during corresponding maneuvers in group A patients. It is concluded that arterial oxygenation can be optimized during one-lung anesthesia by oxygen insufflation of the upper deflated lung at 10 cm H2O pressure while the lower lung is ventilated with zero end-expiratory pressure.
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© 1980 International Anesthesia Research Society