title: Oxygen in air (FiO2 0.4) improves gas exchange in young healthy patients during general anesthesia.
abstract: OBJECTIVE
  One hundred percent O(2) is used routinely for preoxygenation and induction of anesthesia. The higher the O(2) concentration the faster is the development of atelectasis, an important cause of impaired pulmonary gas exchange during general anesthesia (GA). We evaluated the effect of ventilation with 0.4 FiO(2) in air, 0.4 FiO(2) in N(2)O and 100% O(2) following intubation on the development of impaired gas exchange.
  
  
  METHODS
  Twenty-seven patients aged 18-40 yr, undergoing elective laparoscopic cholecystectomy were administered 100% O(2) for preoxygenation (three minutes) and ventilation by mask (two minutes). Following intubation these patients were randomly divided into three groups of nine each and ventilated either with 0.4 FiO(2) in air, 0.4 FiO(2) in N(2)O or 100% O(2). Arterial blood gases were obtained before preoxygenation and 30 min following intubation for PaO(2) analysis. Subsequently PaO(2)/FiO(2) ratios were calculated. Results were analyzed with Student's t test and one-way ANOVA. P value of < or = 0.05 was considered significant.
  
  
  RESULTS
  Ventilation of the lungs with O(2) in air (FiO(2) 0.4) significantly improved the PaO(2)/FiO(2) ratio from baseline, while 0.4 FiO(2) in N(2)O or 100% O(2) worsened the ratio (558 +/- 47 vs 472 +/- 28, 365 +/- 34 vs 472 +/- 22 and 351 +/- 23 vs 477 +/- 28 respectively; P < 0.05).
  
  
  CONCLUSIONS
  Ventilation of lungs with O(2) in air (FiO(2) 0.4) improves gas exchange in young healthy patients during GA.
authors.affiliation: Department of Anesthesia, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India. aagarwal@sgpgi.ac.in
authors.forename: Anil
authors.initials: A
authors.lastname: Agarwal
authors.forename: Prabhat K
authors.initials: PK
authors.lastname: Singh
authors.forename: Sanjay
authors.initials: S
authors.lastname: Dhiraj
authors.forename: Chandra M
authors.initials: CM
authors.lastname: Pandey
authors.forename: Uttam
authors.initials: U
authors.lastname: Singh
mesh_terms: D000328:Adult; D000388:Air / Q000032:analysis*; D000768:Anesthesia, General; D017081:Cholecystectomy, Laparoscopic; D005260:Female; D006801:Humans; D008297:Male; D010100:Oxygen / Q000032:analysis*; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial
chemical_list: D010100:Oxygen