title: Influence of perioperative oxygen fraction on pulmonary function after abdominal surgery: a randomized controlled trial.
abstract: BACKGROUND
  A high perioperative inspiratory oxygen fraction (FiO2) may reduce the frequency of surgical site infection. Perioperative atelectasis is caused by absorption, compression and reduced function of surfactant. It is well accepted, that ventilation with 100% oxygen for only a few minutes is associated with significant formation of atelectasis. However, it is still not clear if a longer period of 80% oxygen results in more atelectasis compared to a low FiO2.Our aim was to assess if a high FiO2 is associated with impaired oxygenation and decreased pulmonary functional residual capacity (FRC).
  
  
  METHODS
  Thirty-five patients scheduled for laparotomy for ovarian cancer were randomized to receive either 30% oxygen (n = 15) or 80% oxygen (n = 20) during and for 2 h after surgery. The oxygenation index (PaO2/FiO2) was measured every 30 min during anesthesia and 90 min after extubation. FRC was measured the day before surgery and 2 h after extubation by a rebreathing method using the inert gas SF6.
  
  
  RESULTS
  Five min after intubation, the median PaO2/FiO2 was 69 kPa [53-71] in the 30%-group vs. 60 kPa [47-69] in the 80%-group (P = 0.25). At the end of anesthesia, the PaO2/FiO2 was 58 kPa [40-70] vs. 57 kPa [46-67] in the 30%- and 80%-group, respectively (P = 0.10). The median FRC was 1993 mL [1610-2240] vs. 1875 mL [1545-2048] at baseline and 1615 mL [1375-2318] vs. 1633 mL [1343-1948] postoperatively in the 30%- and 80%-group, respectively (P = 0.70).
  
  
  CONCLUSIONS
  We found no significant difference in oxygenation index or functional residual capacity between patients given 80% and 30% oxygen for a period of approximately 5 hours.
  
  
  BACKGROUND
  ClinicalTrials.gov Identifier: NCT00637936.
authors: Department of Anaesthesia, Centre of Head and Orthopaedics, Copenhagen University Hospital, Rigshospitalet, Copenhagen Ø, Denmark. akstaehr1@hotmail.com
authors: Anne K
authors: AK
authors: Staehr
authors: Christian S
authors: CS
authors: Meyhoff
authors: Steen W
authors: SW
authors: Henneberg
authors: Poul L
authors: PL
authors: Christensen
authors: Lars S
authors: LS
authors: Rasmussen
mesh_terms: D000005:Abdomen / Q000601:surgery*; D000328:Adult; D000368:Aged; D060666:Airway Extubation; D003718:Denmark; D005260:Female; D005652:Functional Residual Capacity; D013509:Gynecologic Surgical Procedures; D006801:Humans; D008168:Lung / Q000187:drug effects* / Q000503:physiopathology; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000601:surgery*; D010100:Oxygen / Q000008:administration & dosage / Q000009:adverse effects*; D001261:Pulmonary Atelectasis / Q000209:etiology* / Q000503:physiopathology / Q000517:prevention & control; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial / Q000009:adverse effects* / Q000379:methods; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D010100:Oxygen