Randomization and blinding
PCV-VG
The 66 subjects were divided into two groups (1:1) using SPSS 26.0 software program (IBM SPSS Statistics, Chicago, Illinois, USA). and computer random number method. 33 pairs of numbers (1 or 2) were randomly generated, where 1 and 2 corresponded to the PCV-VG and VCV groups, respectively. The intervention methods adopted for PCV-VG or VCV groups were stored in opaque envelopes numbered 1 to 66 in the order in which they were produced. An anesthesiologist blinded to the study opened the envelope and determined the ventilation mode (PCV-VG or VCV). Fibrescope was performed by a senior and experienced anesthesiologist blinded to the study. A nurse who was blinded to the study recorded the data. The parameters of the anesthesia machine were covered using an opaque cloth during the bronchoscopy operation to ensure the operator was blinded to the study.