The effect of increased FIO(2) before tracheal extubation on postoperative atelectasis.
General anesthesia promotes pulmonary atelectasis, which can be eliminated by a vital capacity (VC) maneuver (inflation of the lungs to 40 cm H(2)O for 15 s). High-inspired oxygen concentration favors recurrence of atelectasis. Therefore, 100% oxygen before tracheal extubation may contribute to atelectasis. To evaluate whether the use of 100% oxygen before extubation increases the amount of postoperative atelectasis, we studied 30 adults scheduled for elective surgery of the extremities. Ten minutes before the presumed end of surgery, patients were randomly assigned to (a) a fraction of inspired oxygen (FIO(2)) = 1.0 (n = 10), (b) VC maneuver + FIO(2) = 1.0 (n = 10), or (c) VC maneuver + FIO(2) = 0.4 (n = 10). The amount of atelectasis was measured by computed tomography scan, and oxygenation was studied by arterial blood gas analysis. Data were analyzed by one-way analysis of variance with Bonferroni correction. Results are presented as mean +/- SD; P < 0.05 was considered significant. In the VC maneuver + FIO(2) = 0.4 group, postoperative atelectasis was smaller (2.6% +/- 1.1% of total lung surface, P < 0.05) than in the FIO(2) = 1.0 group (8.3% +/- 6.2%) and in the VC maneuver + FIO(2) = 1.0 group (6.8% +/- 3.4%). Oxygen 100% at the end of general anesthesia promotes postoperative atelectasis. A safety margin in terms of oxygenation during tracheal extubation is essential, and further studies should therefore evaluate whether atelectasis formation could be prevented despite the use of 100% oxygen.


CONCLUSIONS
For safety reasons, it is common to ventilate patients with 100% oxygen before tracheal extubation. This study demonstrates that this practice favors postoperative atelectasis.
Benoît
Zilgia
Z
Department of Anesthesiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Suisse.
Wicky
Stephan
S
Fischer
Jean-François
JF
Frascarolo
Philippe
P
Chapuis
Carine
C
Spahn
Donat R
DR
Magnusson
Lennart
L
D000293:Adolescent; D000328:Adult; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000009:adverse effects*; D011183:Postoperative Complications / Q000209:etiology*; D011446:Prospective Studies; D001261:Pulmonary Atelectasis / Q000209:etiology* / Q000503:physiopathology; D014797:Vital Capacity
D010100:Oxygen