The effects of incremental continuous positive airway pressure on arterial oxygenation and pulmonary shunt during one-lung ventilation

Abstract

Background: Although one lung ventilation (OLV) is frequently used for facilitating thoracic surgical procedures, arterial hypoxemia can occur while using one lung anesthesia. Continuous positive airway pressure (CPAP) in 5 or 10 cmH2O to the non-ventilating lung is commonly recommended to prevent hypoxemia. We evaluated the effects of incremental CPAP to the non-ventilating lung on arterial oxygenation and pulmonary shunt without obstruction of the surgical field during OLV. Methods: Twenty patients that were scheduled for one lung anesthesia were included in this study. Systemic and pulmonary hemodynamic data and blood gas analysis was recorded every fifteen minutes according to the patient's positions and CPAP levels. CPAP was applied from 0 cmH2O by 3 cmH2O increments until a surgeon notifies that the surgical field was obstructed by the expanded lung. Following that, pulmonary shunt fraction (QS/QT) was calculated. Results: There were no significant differences of QS/QT between supine and lateral positions with two lung ventilation (TLV). OLV significantly decreased arterial oxygen partial pressure (PaO2) and increased QS/QT compared to TLV. PaO2 and QS/QT significantly improved at 6 and 9 cmH2O of CPAP compared to 0 cmH2O. However, there were no significant differences of PaO2 and QS/QT between 6 and 9 cmH2O CPAP. In 18 patients (90%), surgical fields were obstructed at 9 cmH2O CPAP. Conclusions: This study suggests that 6 cmH2O CPAP effectively improved arterial oxygenation without interference of the surgical field during OLV when CPAP was applied from 0 cmH2O in 3 cmH2O increments. © the Korean Society of Anesthesiologists, 2012.