Patient enrollment and randomization: This study was approved by the institutional ethical committee of Guangzhou Women and Children’s Medical Center (No. 2014051229, approval date: June 3, 2014). The trial was registered prior to patient enrollment at China Clinical Trial Registry (http://www.chictr.org.cn/showproj.aspx?proj=4344, Principal investigator: Yingyi Xu, Registration number: ChiCTR-TRC-14005232, Date of registration: 12 August 2014). Written informed consent was obtained from all patients enrolled in the study. Informed consent was signed by the guardians of each patient. Pediatric patients scheduled for elective thoracic surgery between September 2014 and June 2016 at Guangzhou Women and Children’s Medical Center were selected. The enrollment criteria were as follows: (1) ASA stage I-III and (2) age of 0.5-3 years old. The exclusive criteria were as follows: (1) airway compression; (2) laryngeal edema or acute airway inflammation; (3) the opening of the right upper lung lobe is parallel to or higher than the carina (Figure 1); (4) patients suspected to have difficulty in laryngoscopy and airway management. (4) uncuffed ETT of 4.5mm could not be inserted. The enrolled patients were randomized into the bronchoscopy (BRO) group and the (CT) group using the closed envelope technique. Random numbers were generated using software (SAS 9.2, SAS Institute Inc, Cary, NC, USA) with a ratio of 1:1. These numbers were then sealed in envelopes and kept by an independent study coordinator who did not participate in anaesthesia, perioperative care and postoperative follow-up of the patients. The endobronchial blocker placement was guided by bronchoscopy in the BRO group and by CT 3-DimenSional airway evaluation in the CT group. All cases of anesthesia were performed by a pediatric anesthetist with 6-year experience of thoracic anesthesia. During the study period, patients were consecutively recruited and randomly divided into the control or intervention group accordingly. This study was single-blinded. Anaesthesiologists who gave anaesthesia did not participate patients’ follow up and data collection. Patients, healthcare providers and investigators who were in charge of follow-up and data collection, were blinded to the study protocol.
CT measurement: After sedation, All pediatric patients under sedation preoperative cervical and chest CT scanning (Aquilion 64, Toshiba) at the supine position. lung window was applied to reconstruct coronal and sagittal image with 3mm slice and 3mm slice gap and 512×512 image resolution . The Frankfurt horizontal plane was confirmed with the bilateral auriculares and the right infraorbital margin; the midsagittal plane was confirmed with the middle of sella turcica, the nasion and the posterior edge of foramen magnum. The distance from the incisor teeth to the tracheal carina was measured at the sagittal image when the incisor teeth, the glottis and the whole airway were able to be exposed clearly at the same time. In the case of inproper position or the airway compression, MPR( multiplanar reconstruction ) or CPR (curve planar reconstruction)was applied. (Figure 2).
Anesthesia: All pediatric patients received intravenous injection of 0.01 mg/kg penehyclidine hydrochloride before surgery and oxygen inhalation after entering the operation room. They received micro-pump infusion (8-10 ml/kg/h) of sodium acetate Ringer's injection, and their BP, HR, ECG, and SpO2 were monitored. Midazolam (0.05 mg/kg), sufentanil (0.3 μg/kg), and rocuronium (0.6 mg/kg) were injected intravenously to induce general anesthesia. Then, a tracheal tube without side holes (Weili Medical Inc, Guangzhou, China) was intubated under direct vision of laryngoscopy. The catheter model was selected according to the calculation using the classic formula (based on predicted age formula). When patient was 0.5 -1 years old, uncuffed ETT of 4.5mm was tried to insert. If uncuffed ETT of 4.5mm could not be inserted, the case was excluded. After intubation, the partial pressure of carbon dioxide in endexpiratory gas (PETCO2) as well as invasive arterial blood pressure and central venous pressure were monitored, and tracheal aspiration was performed. Inhalation of 1%-3% sevoflurane was used for anesthesia maintenance with a tidal volume of 6-8 ml/kg. The concentration of sevoflurane was adjusted according to hemodynamic changes and data of anesthesia monitoring. Rocuronium and sufentanil were supplemented while necessary. All patients were subjected to ICU care after surgery.
Endobronchial blocker placement: In the CT group, CT-3-DimenSional evaluation images were used to measure the length of the main bronchus (the length from the incisor teeth to the carina) before endobronchial blocker placement. Before endotracheal intubation, the insertion depth was preset as the CT-measured length of the main bronchus minus 2 cm and was marked (marker 1) on the tracheal tube (Figure 3a). The endobronchial blocker was inserted through the tracheal tube until the point A of the sacculus reached the catheter tip. The positions on the blocker which paralleled the screw cap (marker 2) and the screw cap plus 2 cm (marker 3) were marked, then the endobronchial blocker was extubated after the cap was screwed on (Figure 3b). The tracheal tube was inserted to marker 1 under direct-vision laryngoscopy. The endobronchial blocker was inserted through the tracheal tube again. The connectors of the endobronchial blocker and the tracheal tube were fixed when the screw cap paralleled marker 2. The endobronchial blocker was further inserted until the screw cap paralleled marker 3 with resistance disappeared, and the sacculus was inflated with 1.5-2.5 ml of air (Figure 3c). Both lungs were auscultated to make sure that respiratory sounds disappeared in the lung of the blocking side. If proper blocking was not achieved after 5 consecutive repositioning trials, bronchoscopy-guided placement was applied, and the patient was excluded from the study. The proper blocker placement was confirmed by auscultation after the patient was shifted from the horizontal position.
In the BRO group, the insertion depth of tracheal tube was calculated using the classic formula 12. After the 5 French (5F) Weili endobronchial blocker (Weili medical Inc, Guangzhou, Guangdong, China) was placed into the tracheal tube, an electrobronchoscope (A20-2.8, Maidehao Co, Zhuhai, Guangdong, China) with a diameter of 2.8 mm was inserted to help locate the endobronchial blocker until the point A of endobronchial blocker reached the take off of the main bronchus at the blocking side (Figure 4 ). The proper blocker placement was confirmed under bronchoscopy after the patients shifted from the horizontal position to the lateral position.
Observational parameters: (1) the required time for successful blocker placement (measured since the endobronchial blocker was inserted through the vocal cord until it was placed at the proper position); (2) the number of repositioning trials for successful blocker placement (each extubation of the endobronchial blocker from the Trachealtube was counted as one repositioning trial);'' (3) the successful rate of the first blocker positioning; (4) the degree of lung collapse ranked by the surgeon as excellent (complete lung collapse at the blocking side), fair (lung collapse at the blocking side with a little amount of residual air that would not affect surgical exposure), moderate (partial lung collapse which requires suction or manual collapse), and poor (no collapse of the lung) 13; (5) airway mucosal injury graded using bronchoscopy after surgery by an anesthetist as none (no mucosal edema), mild (mild mucosal edema), moderate (obvious mucosal edema and hyperemia), severe (mucosal erosion and hemorrhage) 11; (6) pulmonary infection occurred within 72 h after surgery, which was defined as plaque-like shadow on both lungs with or without pleural effusion observed by chest X-ray; (7) hoarseness after tracheal extubation; (8) the duration of postoperative mechanical ventilation; (9) the duration of postoperative intensive care unit (ICU) stay; (10) the duration of postoperative hospitalization.
Estimation of sample size: The sample size was estimated with α = 0.05 and 1-β = 0.8 using the PASS 15.0 software (NCSS, Utah, USA). According to our previous clinical experience, the adequacy of lung collapse was similar in the two groups. According to the estimation, at least 61 patients in each group needed to be enrolled to find a moderate variation (i.e., W = 0.3) between the two groups.
Statistical analyses: The Statistical Package for the Social Science (SPSS) 15.0 software (NCSS, Utah, USA) was used for statistical analyses. The test level α = 0.05 and the power was set at 0.8. According to the previous clinical experiences, the difference between groups was moderate (w = 0.3). In order to find significant differences between groups, according to the calculation results, each group needs at least 61 subjects (n = 122). The demographic data between the two groups was analyzed using independent t test and Chi-squared test, including age, sex, weight, height. The ASA class and thoracic surgery type between groups were analyzed using Chi-squared test. The assessment of blocker operating duration between groups were evaluated by Chi-squared test including required time for successful blocker placement, repositioning and the successful rate of the first blocker positioning. The effectiveness and prognosis between groups was analyzed using Chi-squared test including degree of lung collapse, grade of airway mucosal injury, grade of airway mucosal injury, pulmonary infection and hoarseness after tracheal extubation. The durations of postoperative mechanical ventilation, ICU and hospitalization was analysis using independent t test. The distribution of data was analyzed using Kolmogorov-Smirnov test. If the data were not of normal distribution (p<0.1), Pearson Chi-squared test with correction or Wilcoxon rank sum test was played. The significant level of differences was set at 0.05.