Fig. 2
![Fig. 2](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40981-021-00452-w/MediaObjects/40981_2021_452_Fig2_HTML.png)
Preoperative pulmonary function test. The flow-volume curve showed a characteristic fixed upper airway obstruction pattern
Preoperative pulmonary function test. The flow-volume curve showed a characteristic fixed upper airway obstruction pattern