title: Comparison of margin of safety following two different techniques of preoxygenation.
abstract: OBJECTIVE
  Shortening the duration of efficacious preoxygenation would provide benefit in emergency situations like fetal distress etc. This study aims to compare the margin of safety following preoxygenation using 8 vital capacity breaths (VCB) in 1 min and tidal volume breathing (TVB) for 3 min, by assessing changes in PaO2 and apnea induced desaturation time.
  
  
  METHODS
  Patients were randomly divided into Group A and B. In Group A, 3 min of TVB using O2 flow of 5 l/min and in Group B, 8 VCB in 60 s using O2 flow of 10 l/min were used. Anesthesia was induced in all patients with propofol followed by succinylcholine 2 mg/kg intravenously. Mask ventilation was not done and following intubation endotracheal tube was kept open to atmosphere. The time taken for the patients to desaturate to 90% was noted and immediately ventilation was resumed. Arterial blood gas samples were taken while patients were breathing room air, immediately after preoxygenation and at 90% desaturation.
  
  
  RESULTS
  Baseline PaO2 of both the groups were comparable. After preoxygenation Group B had a significantly high PaO2 value than Group A (439.05 ± 62.20 vs. 345.16 ± 20.80). At 90% desaturation there was no significant difference between groups. Group B showed a significantly high apnea induced desaturation time when compared to Group A (6.87 ± 1.78 vs. 3.47 ± 0.38 min).
  
  
  CONCLUSIONS
  Preoxygenation by 8 VCB in 1 min provides a greater margin of safety, as it results in a significantly high PaO2 with an almost doubled apnea induced desaturation time, in comparison with TVB for 3 min.
authors.affiliation: Department of Anaesthesiology and Critical Care, Amrita Institute of Medical Sciences, Kochi, Kerala, India.
authors.forename: Sunil
authors.initials: S
authors.lastname: Rajan
authors.affiliation: Department of Anaesthesiology and Critical Care, Amrita Institute of Medical Sciences, Kochi, Kerala, India.
authors.forename: Prasanth
authors.initials: P
authors.lastname: Mohan
authors.affiliation: Department of Anaesthesiology and Critical Care, Amrita Institute of Medical Sciences, Kochi, Kerala, India.
authors.forename: Jerry
authors.initials: J
authors.lastname: Paul
authors.affiliation: Department of Anaesthesiology and Critical Care, Amrita Institute of Medical Sciences, Kochi, Kerala, India.
authors.forename: Abraham
authors.initials: A
authors.lastname: Cherian
keywords: Arterial oxygen tension; preoxygenation; tidal volume breathing; vital capacity breathing