title: Preserved oxygenation in obese patients receiving protective ventilation during laparoscopic surgery: a randomized controlled study.
abstract: BACKGROUND
  Venous admixture from atelectasis and airway closure impedes oxygenation during general anaesthesia. We tested the hypothesis that continuous positive airway pressure (CPAP) during pre-oxygenation and reduced fraction of inspiratory oxygen (FIO2 ) during emergence from anaesthesia can improve oxygenation in patients with obesity undergoing laparoscopic surgery.
  
  
  METHODS
  In the intervention group (n = 20, median BMI 41.9), a CPAP of 10 cmH2 O was used during pre-oxygenation and induction of anaesthesia, but no CPAP was used in the control group (n = 20, median BMI 38.1). During anaesthesia, all patients were ventilated in volume-controlled mode with an FIO2 of 0.4 and a positive end-expiratory pressure (PEEP) of 10 cmH2 O. During emergence, before extubation, the control group was given an FIO2 of 1.0 and the intervention group was divided into two subgroups, which were given an FIO2 of 1.0 or 0.31. Oxygenation was assessed perioperatively by the estimated venous admixture (EVA).
  
  
  RESULTS
  The median EVA before pre-oxygenation was about 8% in both groups. During anaesthesia after intubation, the median EVA was 8.2% in the intervention vs. 13.2% in the control group (P = 0.048). After CO2 pneumoperitoneum, the median EVA was 8.4% in the intervention vs. 9.9% in the control group (P > 0.05). One hour post-operatively, oxygenation had deteriorated in patients given an FIO2 of 1.0 during emergence but not in patients given an FIO2 of 0.31.
  
  
  CONCLUSIONS
  A CPAP of 10 cmH2 O during pre-oxygenation and induction, followed by PEEP after intubation, seemed to preserve oxygenation during anaesthesia. Post-operative oxygenation depended on the FIO2 used during emergence.
authors.affiliation: Department of Anaesthesiology and Intensive Care, Västmanland Hospital Västerås, Västerås, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Edmark
authors.affiliation: Department of Anaesthesiology and Intensive Care, Västmanland Hospital Västerås, Västerås, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Östberg
authors.affiliation: Department of Anaesthesiology and Intensive Care, Västmanland Hospital Västerås, Västerås, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Scheer
authors.affiliation: Department of Anaesthesiology and Intensive Care, Västmanland Hospital Västerås, Västerås, Sweden.
authors.forename: W
authors.initials: W
authors.lastname: Wallquist
authors.affiliation: Department of Medical Sciences, Clinical Physiology, Uppsala University, Uppsala, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Hedenstierna
authors.affiliation: Department of Surgical Sciences, Anaesthesiology and Critical Care Medicine, Uppsala University, Uppsala, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Zetterström
mesh_terms: D000328:Adult; D000758:Anesthesia; D001784:Blood Gas Analysis; D015992:Body Mass Index; D045422:Continuous Positive Airway Pressure; D005260:Female; D006801:Humans; D007430:Intraoperative Care; D010535:Laparoscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology* / Q000601:surgery; D010101:Oxygen Consumption; D011028:Pneumoperitoneum, Artificial; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D012121:Respiration, Artificial; D016037:Single-Blind Method; D016896:Treatment Outcome; D055815:Young Adult