Risk of postoperative pneumonia after extubation with the positive pressure versus normal pressure technique: a single-center retrospective observational study

Purpose: A normal pressure extubation technique (no lung inflation before extubation), proposed by the Japanese Society of Anesthesiologists to prevent droplet infection during the coronavirus disease 2019 (COVID-19) pandemic, could theoretically increase postoperative pneumonia incidence compared with a positive pressure extubation technique (lung inflation before extubation). However, the normal pressure extubation technique has not been adequately evaluated. This study compared postoperative pneumonia incidence between positive and normal pressure extubation techniques using a dataset from the University of Tsukuba Hospital. Methods: In our hospital, the extubation methods changed from positive to normal pressure extubation techniques on March 3, 2020 due to the COVID-19 pandemic. Thus, we compared the risk of postoperative pneumonia between the positive (April 1, 2017 to December 31, 2019) and normal pressure extubation techniques (March 3, 2020 to March 31, 2022) using propensity score analyses. Postoperative pneumonia was defined using the International Classification of Diseases, 10th Edition (ICD-10) codes (J13–J18), and we reviewed the medical records of patients flagged with these ICD-10 codes (preoperative pneumonia and ICD-10 codes for prophylactic antibiotic prescriptions for pneumonia). Results: We identified 20,011 surgeries, including 11,920 in the positive pressure extubation group (mean age 48.2 years, standard deviation [SD] 25.2 years) and 8,091 in the normal pressure extubation group (mean age 47.8 years, SD 25.8 years). The postoperative pneumonia incidences were 0.19% (23/11,920) and 0.17% (14/8,091) in the positive and normal pressure extubation groups, respectively. The propensity score analysis using inverse probability weighting revealed no significant difference in postoperative pneumonia incidence between the two groups (adjusted odds ratio 0.98, 95% confidence interval 0.50 to 1.91, P = 0.94). Conclusions: These results indicated no increased risk of postoperative pneumonia associated with the normal pressure extubation technique compared with the positive pressure extubation technique. Clinical trial number: Clinical trial number: UMIN000048589 https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000055364