Over-inflation of the bronchial cuff of the double-lumen tube (DLT) can cause damage to the airway mucosa and misplacement of the tube, and under-inflation may cause incomplete collapse of the non-ventilated lung and incomplete ventilation of the lung that should be ventilated. Appropriate cuff pressure is generally known to be ranged 20-30 cmH₂O, but in the study of Okubo et al., who observed the minimum bronchial cuff volume and pressure that did not cause air leakage using the method of confirming by capnography, it was possible to obtain the result that OLV was possible without air leakage even at a pressure lower than 25 cmH₂O (the generally recommended tube cuff pressure) in both men and women. In a recent study of Yamada et al., when using the capnography waveform-guided method to inflate the bronchial cuff by checking for air leakage using the capnography waveform, the bronchial cuff volume (BCV) that satisfies the air-tight seal was significantly smaller compared with a pressure-guided method to inflate the bronchial cuff with 20 cmH₂O.

The minimum bronchial cuff volume (BCVmin) at which such air leakage does not occur may vary from individual to individual. It is presumed that this is because the diameter of the left main bronchus (LMB) differs from individual to individual, which causes the variation of the gap between the diameter of the LMB and the outer diameter of the DLT mounted thereon. Moreover, the previous study revealed that the lateral positioning could increase the pressure of the bronchial cuff mounted on the LMB due to the gravity-induced morphological and conformational change of the trachea. Considering these factors, the researchers hypothesized that the change in the bronchial cuff pressure (BCP) due to a positional change might vary depending on whether the bronchial cuff was inflated, that is, the initially established BCVmin.

Therefore, in this study, the researchers tried to investigate the effect of BCVmin on the change of minimum bronchial cuff pressure (BCPmin) due to the positional change from the supine to lateral decubitus, by dividing the groups whose BCVmin is 0 ml or exceeds 0 ml.

Inclusion Criteria:

Patients aged 18-80 and with an American Society of Anesthesiologists (ASA) physical status of 1 or 3 who are scheduled to undergo elective video-assisted thoracoscopic surgery (VATS)

Exclusion Criteria:

A. Need for a right-sided DLT B. An intraluminal lesion in the left main bronchus C. An anatomical problem in the tracheobronchial tree D. Patients with chronic obstructive pulmonary disease with impaired lung compliance E. Patients with interstitial lung disease with severe pulmonary dysfunction F. Patients with Body mass index (BMI) ≥ 30

The researcher contacts patients who are potential candidates for the study at the time of their preoperative visit. The participants are being enrolled in the study at the tertiary university hospital in Daegu, South Korea, from October 2021 to December 2021