Primary outcome
postoperative atelectasis, atelectasis
POSTOPERATIVE ATELECTASIS, ATELECTASIS

There was no significant difference in the percentage of postoperative atelectasis volume between the 30% FiO
The primary outcome was missing in seven patients among the patients in the randomization, thus we performed multiple imputation to handle missing normalized primary outcome data. Consistent with the results of the original data, none of the five imputations showed significant differences in the percentage of postoperative atelectasis volume between the two groups (Table 
The percentage of atelectasis volume handled by multiple imputation (5 imputations datasets)CI, confidence interval; FiO
The normalized percentage of atelectasis volume (square root transformation) handled by multiple imputation and sensitivity analysisCI, confidence interval; FiO
The normalized primary outcome. The percentage of postoperative atelectasis volume is shown by (
The multiple imputation pattern. Grey square: no missing data; Red square: missing data imputed by multiple imputation