title: Efficacy of preoxygenation with non-invasive low positive pressure ventilation in obese patients: crossover physiological study.
abstract: OBJECTIVE
  The impact of non-invasive positive pressure ventilation (NIPPV), which is a combination of inspiratory positive airway pressure (IPAP) and positive end expiratory pressure (PEEP), on the effectiveness of preoxygenation in obese patients was evaluated.
  
  
  METHODS
  Randomized, controlled, double blinded, crossover study comparing NIPPV vs. tidal volume breathing (TVB) with regard to the expiratory O(2) fraction (FeO(2)).
  
  
  METHODS
  Thirty participants with body mass index (BMI) greater or equal to 30 kg/m(2) scheduled for elective surgery were included. Patients with facial hair, and airway anomalies were excluded. Each patient underwent 3 minutes 100% O(2) preoxygenation with the two following methods in a random order: 1: TVB; 2: NIPPV (4 cmH(2)O IPAP+4 cmH(2)O PEEP). Primary outcome was FeO(2) after 3 minutes. Secondary outcomes were the number of patients reaching FeO(2) greater or equal to 90%, tidal volume, respiratory rate, and patient comfort on a 4-point scale.
  
  
  RESULTS
  No differences between methods were found regarding the FeO(2) change with time or after 3 minutes (89 ± 6% with TBV vs. 91 ± 4% with NIPPV). FeO(2) greater or equal to 90% was reached more frequently with NIPPV (80%) than with TVB (60%) (P=0.008). Tidal volume (m ± SD) was larger throughout preoxygenation with TBV (837 ± 440 mL) than with NIPPV (744 ± 368 mL), (P=0.0005). Respiratory rate did not differ between regimens. Patient comfort was good and similar.
  
  
  CONCLUSIONS
  This study suggests that providing a positive pressure of 4 cmH(2)O throughout inspiration and expiration during preoxygenation in obese patients provided benefits with regard to the FeO(2).
authors: Département d'anesthesiologie, hôpital Maisonneuve-Rosemont, centre affilié à l'université de Montréal, 5415, boulevard de l'Assomption, Montréal (Québec) Canada, H1T 2M4.
authors: M
authors: M
authors: Georgescu
authors: I
authors: I
authors: Tanoubi
authors: L-P
authors: LP
authors: Fortier
authors: F
authors: F
authors: Donati
authors: P
authors: P
authors: Drolet
mesh_terms: D000328:Adult; D001784:Blood Gas Analysis; D015992:Body Mass Index; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007385:Intermittent Positive-Pressure Ventilation / Q000379:methods*; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology / Q000628:therapy*; D010100:Oxygen / Q000008:administration & dosage / Q000627:therapeutic use*; D010101:Oxygen Consumption; D011175:Positive-Pressure Respiration / Q000379:methods*; D015656:Respiratory Mechanics; D013990:Tidal Volume
chemical_list: D010100:Oxygen