title: Inspiratory oxygen fraction and postoperative complications in obese patients: a subgroup analysis of the PROXI trial.
abstract: BACKGROUND
  Obese patients are at a high risk of postoperative complication, including surgical site infection (SSI). Our aim was to evaluate the effect of a high inspiratory oxygen fraction (80%) on SSI and pulmonary complications in obese patients undergoing laparotomy.
  
  
  METHODS
  This study was a planned analysis of the obese patients (body mass index ≥ 30 kg/m²) recruited in the Danish multicenter, patient- and observer-blinded, PROXI Trial of 1,400 patients undergoing acute or elective laparotomy. Patients were randomized to receive either 80% or 30% oxygen during and for 2 h after surgery. The primary outcome was SSI within 14 days. Secondary outcomes were atelectasis, pneumonia, and respiratory failure.
  
  
  RESULTS
  Two hundred thirteen patients had a body mass index ≥ 30 kg/m². The median (5-95% range) body mass index was 34 kg/m² (30-44) and 33 kg/m² (30-41) in patients allocated to the 80% and 30% oxygen group. SSI occurred in 32 of 102 (31%) versus 29 of 111 (26%) patients given 80% and 30% oxygen, respectively (odds ratio, 1.29; 95% CI, 0.71-2.34; P = 0.40). In addition, the incidence of pulmonary complications was not significantly different, with atelectasis occurring in 9% versus 6%, pneumonia in 6% versus 5%, and respiratory failure in 8% versus 5% in patients given 80% and 30% oxygen, respectively.
  
  
  CONCLUSIONS
  Administration of 80% oxygen, compared with 30% oxygen, did not reduce the frequency of SSI in obese patients. Moreover, no significant association was found between oxygen fraction and the risk of pulmonary complications.
authors.affiliation: Department of Anaesthesia, Centre of Head and Orthopaedics, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark. akstaehr1@hotmail.com
authors.forename: Anne K
authors.initials: AK
authors.lastname: Staehr
authors.forename: Christian S
authors.initials: CS
authors.lastname: Meyhoff
authors.forename: Lars S
authors.initials: LS
authors.lastname: Rasmussen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D001239:Inhalation / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000453:epidemiology / Q000601:surgery*; D010102:Oxygen Inhalation Therapy / Q000379:methods; D011183:Postoperative Complications / Q000453:epidemiology / Q000517:prevention & control*; D012307:Risk Factors; D016037:Single-Blind Method; D013530:Surgical Wound Infection / Q000453:epidemiology / Q000517:prevention & control*