title: 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 cmH(2)O 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 cmH(2)O by 3 cmH(2)O increments until a surgeon notifies that the surgical field was obstructed by the expanded lung. Following that, pulmonary shunt fraction (Q(S)/Q(T)) was calculated.
  
  
  RESULTS
  There were no significant differences of Q(S)/Q(T) between supine and lateral positions with two lung ventilation (TLV). OLV significantly decreased arterial oxygen partial pressure (PaO(2)) and increased Q(S)/Q(T) compared to TLV. PaO(2) and Q(S)/Q(T) significantly improved at 6 and 9 cmH(2)O of CPAP compared to 0 cmH(2)O. However, there were no significant differences of PaO(2) and Q(S)/Q(T) between 6 and 9 cmH(2)O CPAP. In 18 patients (90%), surgical fields were obstructed at 9 cmH(2)O CPAP.
  
  
  CONCLUSIONS
  This study suggests that 6 cmH(2)O CPAP effectively improved arterial oxygenation without interference of the surgical field during OLV when CPAP was applied from 0 cmH(2)O in 3 cmH(2)O increments.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Chonbuk National University Medical School, Jeonju, Korea.
authors.forename: Yeon Dong
authors.initials: YD
authors.lastname: Kim
authors.forename: Seonghoon
authors.initials: S
authors.lastname: Ko
authors.forename: Deokkyu
authors.initials: D
authors.lastname: Kim
authors.forename: Hyungsun
authors.initials: H
authors.lastname: Lim
authors.forename: Ji Hye
authors.initials: JH
authors.lastname: Lee
authors.forename: Min Ho
authors.initials: MH
authors.lastname: Kim