title: Higher fraction of inspired oxygen in anesthesia induction does not affect functional residual capacity reduction after intubation: a comparative study of higher and lower oxygen concentration.
abstract: BACKGROUND
  Low fraction of inspired oxygen (FIO2) reduces the atelectasis area during anesthesia induction. However, atelectasis may occur during laryngoscopy and endotracheal intubation because lungs can collapse within a fraction of a second. We assessed the effects of ventilation with 100 and 40 % oxygen on functional residual capacity (FRC) in patients undergoing general anesthesia.
  
  
  METHODS
  Twenty patients scheduled for elective open abdominal surgery were randomized into 40 % oxygen (GI, n = 10) and 100 % oxygen (GII, n = 10) groups and FRC was measured. Preoxygenation and mask ventilation with 40 and 100 % oxygen were used in GI and GII, respectively. In both groups, 40 % oxygen was used for anesthesia maintenance after intubation. Bilateral lung ventilation was performed with volume guarantee and low tidal volume (7 ml/kg predicted body weight) using bilevel airway pressure. We measured FRC and blood gas in all patients during preoxygenation, after intubation, and during surgery.
  
  
  RESULTS
  FRC decreased from during preoxygenation (GI 2380 ml, GII 2313 ml) to after intubation (GI 1569 ml, GII 1586 ml) and significantly decreased during surgery (GI 1338 ml, GII 1417 ml) (P < 0.05). PaO2/FIO2 decreased from during preoxygenation (GI 419 mmHg, GII 427 mmHg) to after intubation (GI 381 mmHg, GII 351 mmHg) and significantly decreased during surgery (GI 333 mmHg, GII 291 mmHg) (P < 0.05). No significant differences were found between the groups in both parameters.
  
  
  CONCLUSIONS
  FRC significantly decreased from the awake state to surgery in both groups. FRC was not influenced by FIO2 elevation at anesthesia induction.
authors: Department of Anesthesiology and Intensive Care, Tohoku University Hospital, 1-1 Seiryomachi, Aoba-ku, Sendai, Japan. canal_village0207@yahoo.co.jp
authors: Akihiro
authors: A
authors: Kanaya
authors: Daizoh
authors: D
authors: Satoh
authors: Shin
authors: S
authors: Kurosawa
mesh_terms: D000005:Abdomen / Q000601:surgery; D000768:Anesthesia, General / Q000379:methods; D001784:Blood Gas Analysis / Q000379:methods; D004305:Dose-Response Relationship, Drug; D005260:Female; D005652:Functional Residual Capacity / Q000187:drug effects*; D006801:Humans; D007440:Intubation / Q000379:methods; D008168:Lung / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage*; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D012121:Respiration, Artificial / Q000379:methods; D013990:Tidal Volume / Q000187:drug effects
chemical_list: D010100:Oxygen