title: Prevention of atelectasis in morbidly obese patients during general anesthesia and paralysis: a computerized tomography study.
abstract: BACKGROUND
  Morbidly obese patients show impaired pulmonary function during anesthesia and paralysis, partly due to formation of atelectasis. This study analyzed the effect of general anesthesia and three different ventilatory strategies to reduce the amount of atelectasis and improve respiratory function.
  
  
  METHODS
  Thirty patients (body mass index 45 +/- 4 kg/m) scheduled for gastric bypass surgery were prospectively randomized into three groups: (1) positive end-expiratory pressure of 10 cm H2O (PEEP), (2) a recruitment maneuver with 55 cm H2O for 10 s followed by zero end-expiratory pressure, (3) a recruitment maneuver followed by PEEP. Transverse lung computerized tomography scans and blood gas analysis were recorded: awake, 5 min after induction of anesthesia and paralysis at zero end-expiratory pressure, and 5 min and 20 min after intervention. In addition, spiral computerized tomography scans were performed at two occasions in 23 of the patients.
  
  
  RESULTS
  After induction of anesthesia, atelectasis increased from 1 +/- 0.5% to 11 +/- 6% of total lung volume (P < 0.0001). End-expiratory lung volume decreased from 1,387 +/- 581 ml to 697 +/- 157 ml (P = 0.0014). A recruitment maneuver + PEEP reduced atelectasis to 3 +/- 4% (P = 0.0002), increased end-expiratory lung volume and increased Pao2/Fio2 from 266 +/- 70 mmHg to 412 +/- 99 mmHg (P < 0.0001). PEEP alone did not reduce the amount of atelectasis or improve oxygenation. A recruitment maneuver + zero end-expiratory pressure had a transient positive effect on respiratory function. All values are presented as mean +/- SD.
  
  
  CONCLUSIONS
  A recruitment maneuver followed by PEEP reduced atelectasis and improved oxygenation in morbidly obese patients, whereas PEEP or a recruitment maneuver alone did not.
authors.affiliation: Department of Anesthesia and Intensive Care, University Hospital, Uppsala, Sweden. henrik.reinius@surgsci.uu.se
authors.forename: Henrik
authors.initials: H
authors.lastname: Reinius
authors.forename: Lennart
authors.initials: L
authors.lastname: Jonsson
authors.forename: Sven
authors.initials: S
authors.lastname: Gustafsson
authors.forename: Magnus
authors.initials: M
authors.lastname: Sundbom
authors.forename: Olov
authors.initials: O
authors.lastname: Duvernoy
authors.forename: Paolo
authors.initials: P
authors.lastname: Pelosi
authors.forename: Göran
authors.initials: G
authors.lastname: Hedenstierna
authors.forename: Filip
authors.initials: F
authors.lastname: Fredén
mesh_terms: D000328:Adult; D000768:Anesthesia, General / Q000009:adverse effects*; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008170:Lung Compliance; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000150:complications* / Q000503:physiopathology; D011175:Positive-Pressure Respiration; D001261:Pulmonary Atelectasis / Q000503:physiopathology / Q000517:prevention & control*; D036542:Tomography, Spiral Computed; D014057:Tomography, X-Ray Computed / Q000379:methods*