Effectiveness of low levels of nonventilated lung continuous positive airway pressure in improving arterial oxygenation during one-lung ventilation.

Continuous positive airway pressure (CPAP) of 5 and 10 cm H2O applied to the nonventilated lung is effective in improving arterial oxygenation during one-lung ventilation (1-LV). The effectiveness of lower levels of CPAP on improving oxygenation, however, has not been reported, possibly because of 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 FIO2 of 1.0, and the respiratory rate was adjusted to maintain PaCO2 at 40 +/- 4 mm Hg. Patients were randomized to receive nonventilated lung CPAP at either the 2 (Group I) or 5 (Group II) 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 1-LV (Group I, 126 +/- 75 mm Hg, and Group II, 173 +/- 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 Group II, 386 +/- 66 mm Hg; P < or = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)