Abstract: Objective To explore the application effect of bronchial blockers in thoracoscopic surgery with one-lung ventilation (OLV) in children aged 2-9 years and their impact on the intraoperative lung collapse score (LCS). 
Methods Eighty children aged 2-9 years admitted to the Children's Hospital of Xuzhou City were randomly divided into the tracheal group (n=40) and the bronchial group (n=40) using envelope drawing. The tracheal group underwent thoracoscopic surgery with OLV via a tracheal catheter, while the bronchial group underwent thoracoscopic surgery with OLV via a bronchial blocker. Perioperative indicators were compared between the two groups. Mean arterial pressure (MAP), heart rate (HR), and blood gas analysis before ventilation (T1), during ventilation (T2), at 20 min after initiation of ventilation (T3) and at 40 min after initiation of ventilation (T4), as well as quality of recovery 15 (QoR-15) scores and LCS during surgery, and complications, were compared. 
Results The duration of surgery (208.37±24.28) min, duration of intubation (2.69±0.23) min, and catheter displacement rate (2.5%) in the bronchial group were lower than those in the tracheal group ［(21.87±28.34) min, (3.74±0.28) min, 17.5%］, and the first attempt intubation success rate (100.0%) was higher than that in the tracheal group (90.0%) (χ2/t=2.779, 22.258, 5.000, 4.211, P＜0.05). There was no significant difference in interactions between groups, and time points between groups in terms of MAP (P＞0.05), but the difference was significant with respect to time points (F time points=5.236, P＜0.05). For HR, no significant differences of interaction were found between groups, time points, and time points between groups (P＞0.05). The partial pressure of oxygen (PaO2) in arterial blood in the bronchial group gradually decreased with time, while in the tracheal group it initially decreased and then increased. Significant differences of interaction were found between groups, time points, and time points between groups (F between groups = 118.084, F time points = 175.854, F time points between groups = 9.310, all P＜0.05). The partial pressure of carbon dioxide (PaCO2) in arterial blood and oxygen saturation (SpO2) in both groups gradually decreased over time. The difference of interaction between groups, time points and time points between groups was statistically significant (F between groups = 16.742, 151.743, F time points = 33.740, 84.641, F time points between groups = 8.357, 45.565, all P＜0.05). The intraoperative LCS score (6.70±0.56) and QoR-15 score (102.33±12.20) at 1 day after surgery in the bronchial group were higher than those in the tracheal group (5.35±0.47, 89.60±10.10) (t=14.184, 6.17, P＜0.05). There was no significant difference in the incidence of complications between the tracheal and bronchial groups (P＞0.05). 
Conclusion The use of bronchial blockers in thoracoscopic surgery with OLV for children aged 2-9 is effective and significantly influences the intraoperative LCS. 

Key words: pulmonary atelectasis, thoracoscopy, bronchial blocker