title: Prevention of atelectasis formation during induction of general anesthesia.
abstract: General anesthesia promotes atelectasis formation, which is augmented by administration of large oxygen concentrations. We studied the efficacy of positive end-expiratory pressure (PEEP) application during the induction of general anesthesia (fraction of inspired oxygen [FIO(2)] 1.0) to prevent atelectasis. Sixteen adult patients were randomly assigned to one of two groups. Both groups breathed 100% O(2) for 5 min and, after a general anesthesia induction, mechanical ventilation via a face mask with a FIO(2) of 1.0 for another 5 min before endotracheal intubation. Patients in the first group (PEEP group) had continuous positive airway pressure (CPAP) (6 cm H(2)O) and mechanical ventilation via a face mask with a PEEP of 6 cm H(2)O. No CPAP or PEEP was applied in the control group. Atelectasis, determined by computed radiograph tomography, and analysis of blood gases were measured twice: before the beginning of anesthesia and directly after the intubation. There was no difference between groups before the anesthesia induction. After endotracheal intubation, patients in the control group showed an increase of the mean area of atelectasis from 0.8% +/- 0.9% to 4.1% +/- 2.0% (P = 0.0002), whereas the patients of the PEEP group showed no change (0.5% +/- 0.6% versus 0.4% +/- 0.7%). After the intubation with a FIO(2) of 1.0, PaO(2) was significantly higher in the PEEP group than in the control (591 +/- 54 mm Hg versus 457 +/- 99 mm Hg; P = 0.005). Atelectasis formation is prevented by application of PEEP during the anesthesia induction despite the use of large oxygen concentrations, resulting in improved oxygenation.
  
  
  CONCLUSIONS
  Application of positive end-expiratory pressure during the induction of general anesthesia prevents atelectasis formation. Furthermore, it improves oxygenation and probably increases the margin of safety before intubation. Therefore, this technique should be considered for all anesthesia induction, at least in patients at risk of difficult airway management during the anesthesia induction.
authors: Departments of *Anesthesiology and †Diagnostic Radiology, University Hospital, Lausanne, Switzerland; and ‡Department of Clinical Physiology, University Hospital, Uppsala, Sweden.
authors: Marco
authors: M
authors: Rusca
authors: Stefania
authors: S
authors: Proietti
authors: Pierre
authors: P
authors: Schnyder
authors: Philippe
authors: P
authors: Frascarolo
authors: Göran
authors: G
authors: Hedenstierna
authors: Donat R
authors: DR
authors: Spahn
authors: Lennart
authors: L
authors: Magnusson
mesh_terms: D000293:Adolescent; D000328:Adult; D000768:Anesthesia, General / Q000009:adverse effects*; D001784:Blood Gas Analysis; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal; D008297:Male; D011175:Positive-Pressure Respiration; D001261:Pulmonary Atelectasis / Q000000981:diagnostic imaging / Q000517:prevention & control*; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome