title: The influence of perioperative oxygen concentration on postoperative lung function in moderately obese adults.
abstract: OBJECTIVE
  Obesity aggravates the negative effects of general anaesthesia and surgery on the respiratory system, resulting in decreased functional residual capacity and expiratory reserve volume, and increased atelectasis and ventilation/perfusion (Va/Q) mismatch. High-inspired oxygen concentrations also promote atelectasis. This study compares the effects of perioperative inspired low-oxygen and high-oxygen concentrations on postoperative lung function and pulse oximetry values in moderately obese patients (BMI 25-35).
  
  
  METHODS
  We prospectively studied 142 overweight patients, BMI 25-35, undergoing minor peripheral surgery; they were randomly allocated to receive either low-inspired or high-inspired oxygen concentrations during general anaesthesia. Premedication, general anaesthesia and respiratory patterns were standardized. Arterial oxygen saturation (pulse oximetry) was measured on air breathing. Inspiratory and expiratory lung functions were measured preoperatively (baseline) and at 10 min, 0.5, 2 and 24 h after extubation with the patient supine, in a 30 degrees head-up position. The two groups were compared using repeated-measure analysis of variance and t-test analysis.
  
  
  RESULTS
  The low-inspired oxygen group had significantly better arterial saturation during the first 24 h (P < 0.01). Mid-expiratory flow 25 values indicating small airway collapse were significantly better in the low-oxygen group at all measurements (P < 0.05).
  
  
  CONCLUSIONS
  We conclude that postoperative lung function and arterial saturation is better preserved by a low-oxygen strategy, although it is not clear whether this has clinical relevance for the prevention of postoperative pulmonary complications.
authors: Department of Anaesthesia and Intensive Care Medicine, University of Marburg, Marburg, Germany. zoremba@med.uni-marburg.de
authors: Martin
authors: M
authors: Zoremba
authors: Frank
authors: F
authors: Dette
authors: Thorsten
authors: T
authors: Hunecke
authors: Stefan
authors: S
authors: Braunecker
authors: Hinnerk
authors: H
authors: Wulf
mesh_terms: D000768:Anesthesia, General / Q000009:adverse effects*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000601:surgery*; D010092:Oximetry; D010100:Oxygen / Q000008:administration & dosage* / Q000032:analysis; D019990:Perioperative Care / Q000379:methods*; D011183:Postoperative Complications / Q000517:prevention & control*; D011446:Prospective Studies; D012129:Respiratory Function Tests; D016896:Treatment Outcome
chemical_list: D010100:Oxygen