Effectiveness of Low Levels of Nonventilated Lung Continuous Positive Airway Pressure in Improving Arterial Oxygenation During One-Lung Ventilation

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Abstract
F limitations of previous methods of CPAP delivery. Recently, a disposable, self-assembled CPAP system capable of delivering CPAP over a wide range of pressures has been introduced (Mallinckrodt Medical, Inc., St. Louis, MO). The purpose of this study was to evaluate the effectiveness of 2 and 5 cm H2O of CPAP delivered with this device in improving Pao2, in thoracic surgical patients during 1 -LV. Twenty patients scheduled for thoracotomy were anesthetized and a left-sided endobronchial tube was placed with fiberoptic bronchoscopic guidance. Patients were ventilated with a tidal volume of 12 mL/kg, an F102, of 1.0, and the respiratory rate was adjusted to maintain Paco, at 40 ± 4 mm Hg. Patients were randomized to receive nonventilated lung CPAP at either the 2 (Group I) or 5 (Group 11) cm H2O pressure setting of the device. Application of CPAP followed 20 min of stable 1-LV in the lateral decubitus position. Compared with two-lung ventilation, Pao2 (mean ± SD) was significantly less with I-LV (Group I, 126 ± 75 mm Hg, and Group 11,173 2 79 mm Hg). Application of the assigned CPAP resulted in an increase in Pao2 compared to 1-LV (Group I, 270 ± 112 mm Hg, and Group11, 386 ± 66 mm Hg, P < 0.05). Nonventilated lung airway pressure with the CPAP system at the 2 and 5 settings was 2.6 ± 0.4 and 5.5 ± 0.5 cm H2O, respectively. These results demonstrate that during 1-LV, improvement in arterial oxygenation with nonventilated lung CPAP can be achieved with both the 2 and 5 cm H2O CPAP settings of the Mallinckrodt CPAP system. Address correspondence and reprint requests to Charles W. Hogue, Jr., MD, Division of Cardiothoracic Anesthesia, Department of Anesthesiology, Washington University School of Medicine, 660 S. Euclid Ave., Campus Box 8054, St. Louis, MO 63110. The author is grateful to members of the Divisions of Cardiothoracic Anesthesia and Surgery for their assistance in the implementation of this study, especially to Demetrios Lappas, MD, and Anastasios Triantafillou, MD, for their review of this manuscript, and to Gerri Neumann for her help in preparing the manuscript. This work was supported in part by a grant from Mallinckrodt Medical, Inc. (St. Louis, MO). Accepted for publication March 29, 1994. © 1994 International Anesthesia Research Society...

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