title: Pre-oxygenation in the obese patient: effects of position on tolerance to apnoea.
abstract: BACKGROUND
  In obese patients, reduced functional residual capacity exacerbated by supine position might decrease the effectiveness of pre-oxygenation and the tolerance to apnoea. The aim of this study was to compare the effect of body posture during pre-oxygenation, sitting or supine, on its effectiveness in obese patients.
  
  
  METHODS
  Forty obese patients (BMI > or =35 kg m(-2)) undergoing surgery with general anaesthesia were randomly assigned to one of two groups: Group 1 (sitting, n=20) or Group 2 (supine, n=20). In the predetermined body position, pre-oxygenation was achieved with eight deep breaths within 60 s and an oxygen flow of 10 litre min(-1). After rapid sequence induction of anaesthesia in decubitus position, the trachea was intubated and the patient was left apneic and disconnected from the anaesthesia circuit until Sp(o2) decreased to 90%. The time taken for desaturation to 90% from the end of induction of anaesthesia was recorded. Arterial blood oxygen tension was measured before (baseline) and after pre-oxygenation. Values were compared with two-way anova and unpaired Student's t-test.
  
  
  RESULTS
  Oxygen and carbon dioxide tensions were similar between groups, both at baseline and after pre-oxygenation. However, the mean time to desaturation to 90% was significantly longer in the sitting group compared with the supine group [mean (SD): 214 (28) vs 162 (38) s, P<0.05].
  
  
  CONCLUSIONS
  Pre-oxygenation in sitting position significantly extends the tolerance to apnoea in obese patients when compared with the supine position.
authors.affiliation: Departamento de Anestesiología, Escuela de Medicina, Pontificia Universidad Católica de Chile, Chile. falterma@med.puc.cl
authors.forename: F R
authors.initials: FR
authors.lastname: Altermatt
authors.forename: H R
authors.initials: HR
authors.lastname: Muñoz
authors.forename: A E
authors.initials: AE
authors.lastname: Delfino
authors.forename: L I
authors.initials: LI
authors.lastname: Cortínez
mesh_terms: D000328:Adult; D000768:Anesthesia, General; D000886:Anthropometry; D001049:Apnea / Q000517:prevention & control*; D002245:Carbon Dioxide / Q000097:blood; D005260:Female; D006801:Humans; D007431:Intraoperative Complications / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D010100:Oxygen / Q000097:blood; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D010313:Partial Pressure; D011187:Posture; D011300:Preoperative Care / Q000379:methods*; D016683:Supine Position
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen