With the development of electronic bronchoscopic interventional techniques in recent years, the elimination of tumors in the large airways is not difficult, and commonly used methods include high-frequency electric knife, argon plasma coagulation (APC), laser, CO2 freezing, and endoprosthesis placement. The electrocoil condenser is a special type of high-frequency electric knife, which is widely used for electrodesiccation and removal of gastrointestinal tumors or polyps [1], and it is also used in the treatment of airway polyps or tumors [2, 3], but it is far from popular. The authors summarize the experience of 80 cases of clinical application of electric trap combined with CO2 freezing and other treatment of large tumors in the airway for the reference of colleagues. I. Materials and methods 1. Clinical data Retrospective analysis of 77 cases of large intra-airway tumors or polyps admitted from February 2010 to March 2012, aged 33-84 years (mean age 60.9±1.3 years), of which 54 cases were male and 23 cases were female. The nature of intra-airway lesions: 70 cases of intra-airway malignant tumors, including 30 primary cases (including 11 cases of squamous carcinoma, 8 cases of adenoid cystic carcinoma, 2 cases each of adenocarcinoma, mixed adenosquamous carcinoma, small cell carcinoma (SCLC) and carcinoid tumor, and 1 case each of squamous carcinoma combined with small cell carcinoma, sarcomatoid carcinoma and mucous epidermis-like carcinoma. There were 40 cases of metastatic carcinoma in the trachea, 29 cases of lung cancer (including 24 cases of squamous carcinoma, 3 cases of adenocarcinoma, 1 case each of mixed adenosquamous carcinoma and SCLC), 5 cases of esophageal cancer, 3 cases of thyroid cancer, 2 cases of kidney cancer, and 1 case of colorectal cancer. There were 7 cases of benign lesions in the airway, including 4 benign tumors (2 cases of hemangioblastoma, 1 case each of lipoma and fibroma), 2 cases of post-tracheotomy airway polyps, and 1 case of airway amyloidosis. The protocol was approved by the hospital ethics committee, and the patients and their families signed the informed consent form. (1) Electronic bronchoscope (referred to as soft microscope) The soft microscope used was Japanese PENTAX-EPM3500, which was performed according to the operation routine of electronic bronchoscope. (2) Rigid mirror The rigid mirror used was Karl Storz (Tutlingen, Germany). The operation was performed in the operating room. Oxygen was administered by mask before anesthesia and preoxygenated for 5 to 10 minutes. Atropine 0.5 mg or scopolamine 0.3 was administered intravenously 10 minutes before surgery to suppress excessive secretions in the airway. Intraoperative monitoring of oxygen saturation, electrocardiogram, blood pressure and respiratory movements is required. Patients are applied midazolam 2 mg sedation 5 min before induction, followed by 1 to 2 μg /kg of fentanyl and 1% isoproterenol (1 to 2 mg/kg ). Then the muscle relaxant atracurium 0.5 mg?kg-1 was given, and the rigid mirror could be inserted through the mouth after the muscle fibrillation disappeared and the mandibular muscles relaxed. The drug concentration was maintained at 1% isoproterenol 1~2mg/kg?h-1 and remifentanil 0.1~0.2μg/kg?min-1. Then the anesthesia ventilator and high frequency jet ventilation were connected and various operations were performed through the operation hole at the back of the rigid scope. 2. Tracheoscopic interventional equipment The equipment used for argon plasma coagulation (APC) is a German-made CESEL 3000. The APC probe is extended through the electronic bronchoscopic biopsy hole at the insertion end of the bronchoscope (where the probe mark is visible) and cautery is started within 0.5 cm of the lesion. The APC output power is 30~50 W, argon flow rate is 0.8~1.6 L/min. Do not stop oxygen inhalation during cautery, but intermittent cautery is appropriate (about 5~10s each time), not too long, and continuously remove the carbonized and solidified tissue with biopsy forceps (carbonized tissue is flammable and fires). High-frequency electrical generator ( PSD-20, UES-30) for the Japanese Olympus company and the electric coiler type for the Nanjing Microtronics production. The power of electrocoagulation is 30~40 W. When the tumor is cut, the trap is wrapped around the base of the tumor, and the hand is pulled tightly to contract the trap, then the high-frequency electrocoagulation is started, and the power time is 5~10 s, and the tumor can be removed. Then the tumor will be removed with optical biopsy forceps or frozen. For the tumor with larger base or cannot be trapped, the method of freeze excision is used. The freezing machine adopts K300 type of cryotherapy instrument produced by Beijing Kulan Medical Equipment Co. and German ERBE . The diameter of the soft bendable cryoprobe is 1.9~2.3mm, and the length of the end of the probe is 5mm. the cold source is liquid carbon dioxide. The metal head of the freezing probe is placed on the surface of the tumor or pushed into the tumor, frozen for 5-10 seconds to produce the largest volume of ice ball around it, and the probe and its adherent tumor tissue are removed in the frozen state, and the probe is inserted again if necessary, until all the tumors in the cavity are removed. If there is bleeding after freezing and extraction, it is combined with APC to stop the bleeding. 3. judgment of efficacy According to the authors’ experience, the central type airway was divided into 8 zones [5]: the main trachea was divided into 3 parts, from top to bottom as zones 1, 2 and 3; the mediastinum was zone 4; the right main bronchus was zone 5; the right middle segment bronchus was zone 6; the proximal 1/2 segment of the left main bronchus was zone 7 and the distal 1/2 segment was zone 8. Different zones should be treated in different ways. The efficacy criteria for airway stenosis recanalization [ 6]: completely effective (CR): the luminal lesion is completely cleared and the function is normalized; partially effective (PR): more than 50% of the stenotic lumen is reopened, the functional examination is approximately normal, and the patient’s subjective symptoms improve; mildly effective (MR): the stenosis is improved by less than 50%, but the inflammation in the lung distal to the stenosis is dissipated by drainage; not effective (NR): the lesion is not eliminated and the stenosis is not relieved. No effect (NR): lesion not resolved, stenosis not relieved. Shortness of breath was graded using the American Thoracic Society shortness of breath rating scale [7]: Grade 0: normal; Grade 1: shortness of breath during fast walking; Grade 2: shortness of breath during walking at normal speed; Grade 3: shortness of breath during walking at normal speed and stop walking; Grade 4: shortness of breath after slight activity. 4.Statistical processing: SPSS11.0 statistical package was used for analysis, and t-test was used. 5.Survival curves The starting point of survival time was calculated from the first d of receiving high-frequency electrocautery. Survival rate was calculated using Kaplan-Meier formula. III. RESULTS 1. Site of the airway where the circling lesion was located Table 1 Site of the airway where the circling lesion was located Site of the lesion 32 primary malignant 46 secondary malignant benign lesions (n/%) (n/%) (n/%) 1 2( 5.4 ) 1( 2.2) 1(14.3) 2 3( 8.1 ) 2( 4.3) 1(14.3) 3 5(13.5) 11(23.9) 1( 14.3) 4 0( 0) 1( 2.2) 1(14.3) 5 7(18.9) 14(30.4) 1(14.3) 6 5(13.5) 4( 8.7) 0( 0) 7 2( 5.4) 4( 8.7) 1(14.3) 8 5(13.5) 4( 8.7) 0( 0) top right 2( 5.4) 0(0) 0( 0) 0( 0) bottom left 1( 2.7) 0(0) 0( 0) left upper 0( 0) 1(2.2) 1(14.3) As seen in Table 1, 70 cases of malignant tumors in the large airways occurred in 30 cases (42.9%) in the right bronchus (5+6), 24 cases (38.3%) in the main trachea (1+2+3), and 15 cases (21.4%) in the left bronchus (7+8). There was no significant difference between the two groups for primary and secondary malignancies, both of which were most common in zones 3 and 5. There was no pattern in the sites of benign lesions. According to the location of the lesion on the canal wall, primary tumors: (intraductal + canal wall + extraductal) 20 cases (62.5%), (intraductal + canal wall) 8 cases (25%), and intraductal 4 cases (12.5%). Metastatic tumors: (intraductal + wall + extraductal) 20 cases (43.5%), (intraductal + extraductal) 22 cases (47.8%), intraductal 4 cases (8.7%). There were significantly more metastatic tumors in the metastatic tumor group (intraductal + ductal wall) than in the primary tumor group (p<0.05), and no significant difference between the other two groups. The mixed type of malignant tumor (more than two types of lesions) accounted for 89.7%, while the intra-tubular type alone accounted for only 10.3%. The method used in tracheoscopy In this group, 77 patients were treated by tracheoscopic laparoscopy 85 times, among which only 3 times were done under electronic bronchoscope alone, and the rest 82 times were done by rigid bronchoscope combined with electronic bronchoscope. 30 cases of primary tumor were treated by laparoscopy 32 times, and 40 cases of metastatic tumor were treated by laparoscopy 46 times. All 70 patients with malignant tumors received tracheoscopic treatment for an average of 3.8±0.4 times per case. 3. Improvement of airway obstruction and clinical status of patients before and after trap treatment Table 2 Improvement of airway obstruction and clinical status of patients before and after trap treatment Malignant tumors (n=76) Benign lesions (n=7) Degree of airway obstruction (%) Before treatment 84.0±2.2* 80.0±10.6* After treatment 22.2±3.3 22.9±10.4 KPS score (%) Before 62.9±2.2* 70.0±6.9 After 80.6±1.6 82.9±8.1 Shortness of breath score Before 2.8±0.1* 2.4±0.4* After 1.3±0.1 0.7±0.4 Note: Comparison between the same group before and after treatment (*P < 0.01) As shown in Table 2, except for the benign lesion group, there was no significant difference before and after KPS trap treatment, and all other There were significant changes in the treatment indexes before and after the treatment with the trap (P < 0.01). The tumor or polyp could be removed with the electric trap combined with freezing (Figure 1B, Figure 2B), and the postoperative surface was flat, white and coagulated without perforation, and bleeding was less and controllable. Tumors with a tip can be removed at once, while larger or broad-based tumors need to be lanced with multiple lancets, or combined with freezing or APC. After treatment, most of the lesions in the airway disappeared and the lumen was patent (Figure 1C, Figure 2C). After treatment, 78 cases of malignant tumors were treated with CR in 24 cases (30.8%), PR in 47 cases (60.3%), and MR in 7 cases (9.0%). The effectiveness rate (CR+PR) was 91%, and the clinical benefit rate (CR+PR+MR) was 100%. Benign lesions were CR in 4 cases (57.1%), PR in 2 cases (28.6%), and MR in 1 case (14.3%). According to the Kaplan-Meier survival curve, the survival time of malignant tumors was more than 1 year in 27.1% (primary tracheal cancer was similar to metastatic tracheal cancer). The median survival time was 6 months, and the mean survival time was 8.3 months. The high-frequency electric knife is a kind of thermal coagulation technique that converts electrical energy into thermal energy to remove or ablate the diseased tissues. In China, transbronchoscopic high-frequency electrosurgery was introduced in 1984 for the treatment of benign and malignant tracheobronchial tumors and inflammatory granulomas [8]. The electric coiler is a special type of high-frequency electric knife mainly used for the removal of tangential tumors or polyps. The electric trap is an essential tool for gastroscopy and has become an important industry [9]. However, in the respiratory field, electric traps have only sporadic applications and reports and are far from an industry. Large tumors or polyps in the airway are the most problematic issue for respiratory endoscopists, and are difficult to grasp with normal biopsy forceps due to the large size of the tumor. Previous authors have treated large tumors or polyps in the airway mainly by APC and freeze extraction [4, 10] , but there are risks of bleeding and asphyxia. Moreover, the operation time is long and the number of treatments is high. In this paper, the right main bronchus was the most common lesion, followed by the lower main bronchus. The tumors or polyps were located in the lumen. Intraluminal lesions alone are rare, and most of them are mixed (endotracheal combined with wall type or combined with extraluminal type). Regardless of whether the tumor or polyp has a tip or not, as long as it is elevated on the mucosal surface, an electric trap is suitable. The electric trap is mainly composed of trap wire, plastic cannula and handle, and the shape of the trap after opening is mostly oval, but there are also hexagonal and crescent-shaped. Adjust the position of the mirror body during treatment, extend the trap from the clamp channel, open the trap according to the size of the lesion, trap the lesion, stick the lesion with the front end of the trap outer tube, and then gradually tighten the trap to trap the size of the lesion as needed. After snapping, the capsule can be moved back and forth slightly, and the capsule is gradually tightened during energization until the lesion is removed. For tumors or polyps with tissues, the tissue can be excised by electrocoagulation after applying the device to the tissues and energizing them, which usually does not cause bleeding. For larger tissues, they can be removed with three-jaw foreign body forceps or frozen. For polyps without a tip, hypertonic saline or 1:10,000 epinephrine solution should be injected into the base of the tumor or polyp at 1 to 2 points, 1.0 ml per point, and then the raised tissue should be removed with a loop sleeve. For tumors with large bases or those that cannot be trapped directly, the electrocoagulation probe of the trap can be placed on the lesion with the sheath protruding slightly and energized for 10-30s, and then the lesion can be coagulated and vaporized by multiple clicks of electrocoagulation. Or the tissue can be cut into multiple pieces for easy access to the trap. The authors previously treated endotracheal tumors with tracheoscopy, which generally required 5.9 sessions [10]. In the present data, only 3.8 sessions were required, and the time required for each session was significantly reduced. After treatment with the trap, the obstruction in the airway was significantly reduced, the clinical symptoms were significantly improved, and the shortness of breath score was significantly reduced. After the treatment, the CR of malignant tumor reached 30.8%, PR reached 60.3%, and MR reached 9.0%. The effectiveness rate was 91%, and the clinical benefit rate was 100%. In benign lesions, CR was 57.1%, PR was 28.6%, and MR was 14.3%. All treatment procedures were safe, with no cases of serious complications such as hemorrhage, perforation or death. The median survival time for malignant tumors was 7 months, and 27.1% of the patients had more than 1 year. In conclusion, high-frequency electric trap treatment for airway obstruction has remarkable efficacy, low cost, low surgical trauma, few complications, and fast postoperative recovery, which is worthy of wide clinical application.