title: Continuous positive airway pressure/pressure support pre-oxygenation of morbidly obese patients.
abstract: BACKGROUND
  Morbidly obese patients are more prone to desaturation of arterial blood during apnea with induction of anesthesia than are non-obese. This study aimed to assess the effect of low-pressure continuous positive airway pressure (CPAP) with pressure support ventilation (PSV) during pre-oxygenation on partial oxygen pressure in arterial blood (PaO2 ) immediately after tracheal intubation (post-intubation PaO2).
  
  
  METHODS
  Forty-four adult patients scheduled for laparoscopic gastric bypass surgery were pre-oxygenated with 80% O2 for 2 min, randomized either to CPAP 5 cm H2O + PSV 5 cm H2O (CPAP/PSV, n = 22) or neutral-pressure breathing without CPAP/PSV (control, n = 22). Anesthesia was induced in a rapid-sequence protocol and the trachea was intubated without prior mask ventilation. Arterial blood gases were measured before pre-oxygenation, before induction of anesthesia, and immediately following intubation, before the first positive pressure breath.
  
  
  RESULTS
  After pre-oxygenation, partial carbondioxide pressure was significantly lower in the CPAP/PSV group (4.9 ± 0.5 kPa), (mean ± standard deviation) than in the control group (5.2 ± 0.7 kPa) (P = 0.025). Post-preoxygenation PaO2 did not differ between the groups, but post-intubation PaO2 was significantly higher in the CPAP/PSV group (32.2 ± 4.1 kPa) than in the control group (23.8 ± 8.8 kPa) (P < 0.001). In the control group, nadir oxygen saturation was lower (median 98%, range 83-99%) than in the CPAP/PSV group (median 99%, range 97-99%, P = 0.011).
  
  
  CONCLUSIONS
  In morbidly obese patients, low-pressure CPAP combined with low-pressure PSV during pre-oxygenation resulted in better oxygenation, compared with neutral-pressure breathing, and prevented desaturation episodes.
authors.affiliation: Department of Anesthesiology and Intensive Care, Danderyd Hospital, Stockholm, Sweden.
authors.forename: P
authors.initials: P
authors.lastname: Harbut
authors.forename: W
authors.initials: W
authors.lastname: Gozdzik
authors.forename: E
authors.initials: E
authors.lastname: Stjernfält
authors.forename: R
authors.initials: R
authors.lastname: Marsk
authors.forename: J F
authors.initials: JF
authors.lastname: Hesselvik
mesh_terms: D000328:Adult; D000769:Anesthesia, Inhalation; D000771:Anesthesia, Intravenous; D002245:Carbon Dioxide / Q000097:blood; D045422:Continuous Positive Airway Pressure / Q000379:methods*; D017558:Elective Surgical Procedures; D005260:Female; D015390:Gastric Bypass; D006801:Humans; D006935:Hypercapnia / Q000097:blood / Q000209:etiology / Q000517:prevention & control; D000860:Hypoxia / Q000097:blood / Q000209:etiology / Q000517:prevention & control; D007431:Intraoperative Complications / Q000097:blood / Q000209:etiology / Q000517:prevention & control; D007442:Intubation, Intratracheal; D010535:Laparoscopy; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000601:surgery / Q000628:therapy*; D010100:Oxygen / Q000097:blood; D010102:Oxygen Inhalation Therapy; D010313:Partial Pressure; D011175:Positive-Pressure Respiration / Q000379:methods*; D011300:Preoperative Care; D011659:Pulmonary Gas Exchange
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen