Comparable postoperative pulmonary atelectasis in patients given 30% or 80% oxygen during and 2 hours after colon resection

Background High concentrations of inspired oxygen are associated with pulmo nary atelectasis but also provide recognized advantages. Consequently, the appropriate inspired oxygen concentration for general surgical use remains controversial. The authors tested the hypothesis that atelectasis and pulmo nary dysfunction on the first postoperative day are comparable in patients given 30% or 80% perioperative oxygen. Methods: Thirty patients aged 18-65 yr were anesthetized with isoflurane an d randomly assigned to 30% or 80% oxygen during and for 2 h after colon res ection. Chest radiographs and pulmonary function tests (forced vital capaci ty and forced expiratory volume) were obtained preoperatively and on the fi rst postoperative day. Arterial blood gas measurements were obtained intrao peratively, after 2 h of recovery, and on the first postoperative day. Comp uted tomography scans of the chest were also obtained on the first postoper ative day. Results: Postoperative pulmonary mechanical function was significantly redu ced compared with preoperative values, but there was no difference between the groups at either time. Arterial gas partial pressures and the alveolar- arterial oxygen difference were also comparable in the two groups. till pre operative chest radiographs were normal. Postoperative radiographs showed a telectasis in 36% of the patients in the 30% oxygen group and in 44% of tho se in the 80%-oxygen group. Relatively small amounts of pulmonary atelectas is (expressed as a percentage of total lung volume) were observed on the co mputed tomography scans, and the percentages (mean +/- SD) did not differ s ignificantly in the patients given 30% oxygen (2.5% +/- 3.2%) or 80% oxygen (3.0% +/- 1.8%). These data provided a 99% chance of detecting a 2% differ ence in atelectasis volume at an a level of 0.05. Conclusions: Lung volumes, the incidence and severity of atelectasis, and a lveolar gas exchange were comparable in patients given 30% and 80% perioper ative oxygen. The authors conclude that administration of 80% oxygen in the perioperative period does not worsen lung function. Therefore, patients wh o may benefit from generous oxygen partial pressures should not be denied s upplemental perioperative oxygen for fear of causing atelectasis.