The effectiveness of noninvasive positive pressure ventilation to enhance preoxygenation in morbidly obese patients: a randomized controlled study

Anesth Analg. 2008 Nov;107(5):1707-13. doi: 10.1213/ane.0b013e318183909b.


Background: Noninvasive positive-pressure ventilation (NPPV) with pressure support-ventilation and positive end-expiratory pressure are effective in providing oxygenation during intubation in hypoxemic patients. We hypothesized administration of oxygen (O2) using NPPV would more rapidly increase the end-tidal O2 concentration (ETO2) than preoxygenation using spontaneous ventilation (SV) in morbidly obese patients.

Methods: Twenty-eight morbidly obese patients were enrolled in this prospective randomized study. Administration of O2 for 5 min was performed either with SV group or with NPPV (pressure support = 8 cm H2O, positive end-expiratory pressure = 6 cm H2O) (NPPV group). ETO2 was measured using the anesthesia breathing circuit, and is expressed as a fraction of atmospheric concentration. The primary end-point was the number of patients with an ETo(2) >95% at the end of O2 administration. Secondary end-points included the time to reach the maximal ETO2 and the ETO2 at the conclusion of O2 administration.

Results: A larger proportion of patients achieved a 95% ETO2 at 5 min with NPPV than SV (13/14 vs 7/14, P = 0.01). The time to reach the maximal ETO2 was significantly less in the NPPV than in the SV group (185 +/- 46 vs 222 +/- 42 s, P = 0.02). The mean ETO2 at the conclusion of O2 administration was larger in the NPPV group than the SV group (96.9 +/- 1.3 vs 94.1 +/- 2.0%, P < 0.001). A modest, although significant, increase in gastric distension was observed in the NPPV group. No adverse effects were observed in either group.

Conclusion: Administration of O2 via a facemask with NPPV in the operating room is safe, feasible, and efficient in morbidly obese patients. In this population NPPV provides a more rapid O2 administration, achieving a higher ETO2.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Anesthesia, Closed-Circuit
  • Humans
  • Hyperbaric Oxygenation / methods*
  • Intermittent Positive-Pressure Ventilation / methods*
  • Obesity, Morbid / complications
  • Obesity, Morbid / physiopathology*
  • Oxygen / blood
  • Oxygen Inhalation Therapy / methods*
  • Patient Selection
  • Positive-Pressure Respiration / methods*
  • Respiration, Artificial
  • Respiratory Insufficiency / etiology
  • Respiratory Insufficiency / therapy
  • Tidal Volume


  • Oxygen