title: The use of air in the inspired gas mixture during two-lung ventilation delays lung collapse during one-lung ventilation.
abstract: BACKGROUND
  Collapse of the ipsilateral lung facilitates surgical exposure during thoracic procedures. The use of different gas mixtures during two-lung ventilation (2LV) may improve or impede surgical conditions during subsequent one-lung ventilation (OLV) by increasing or delaying lung collapse. We investigated the effects of three different gas mixtures during 2LV on lung collapse and oxygenation during subsequent OLV: Air/Oxygen (fraction of inspired oxygen [FIO(2)] = 0.4), Nitrous Oxide/Oxygen ("N(2)O," FIO(2) = 0.4) and Oxygen ("O(2)," FIO(2) = 1.0).
  
  
  METHODS
  Subjects were randomized into three groups: Air/Oxygen (n = 33), N(2)O (n = 34) or O(2) (n = 33) and received the designated gas mixture during induction and until the start of OLV. Subjects' lungs in all groups were then ventilated with FIO(2) = 1.0 during OLV. The surgeons, who were blinded to the randomization, evaluated the lung deflation using a verbal rating scale at 10 and 20 min after the start of OLV. Serial arterial blood gases were performed before anesthesia induction, during 2LV, and every 5 min, for 30 min, after initiation of OLV.
  
  
  RESULTS
  The use of air in the inspired gas mixture during 2LV led to delayed lung deflation during OLV, whereas N(2)O improved lung collapse. Arterial oxygenation was significantly improved in the O(2) group only for the first 10 min of OLV, after which there were no differences in mean Pao(2) values among groups.
  
  
  CONCLUSIONS
  De-nitrogenation of the lung during 2LV is a useful strategy to improve surgical conditions during OLV. The use of FIO(2) 1.0 or N(2)O/O(2) (FIO(2) 0.4) during 2LV did not have an adverse effect on subsequent oxygenation during OLV.
authors.affiliation: Department of Anesthesia and Pain Management, Toronto General Hospital, University Health Network, University of Toronto, Ontario, Canada.
authors.forename: Raynauld
authors.initials: R
authors.lastname: Ko
authors.forename: Karen
authors.initials: K
authors.lastname: McRae
authors.forename: Gail
authors.initials: G
authors.lastname: Darling
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Waddell
authors.forename: Desmond
authors.initials: D
authors.lastname: McGlade
authors.forename: Ken
authors.initials: K
authors.lastname: Cheung
authors.forename: Joel
authors.initials: J
authors.lastname: Katz
authors.forename: Peter
authors.initials: P
authors.lastname: Slinger
mesh_terms: D000280:Administration, Inhalation; D000368:Aged; D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D001239:Inhalation; D008175:Lung Neoplasms / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009609:Nitrous Oxide / Q000008:administration & dosage*; D010100:Oxygen / Q000008:administration & dosage* / Q000097:blood; D011013:Pneumonectomy; D011031:Pneumothorax, Artificial; D012121:Respiration, Artificial / Q000379:methods*; D013906:Thoracoscopy; D013908:Thoracotomy; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D018685:Anesthetics, Inhalation; D009609:Nitrous Oxide; D010100:Oxygen