Table 4. Intervention parameters .

	Authors	Details of bronchoscope used for stent treatment	Treatment prior to stent therapy	Details of the procedure	Number of treatments/Length of treatment	Adjuvant therapy used alongside stent placement	Post stent therapy
1.	Dalar L et al [8].	Totally, 802 interventional rigid bronchoscopy procedures were applied in 547 patients having a malign airway obstruction.	Not mentioned	The study participants with malignant airway obstruction underwent different therapeutic bronchoscopy interventions such as stent placement, laser, cryotherapy, and Argon plasma coagulation.	Stents were applied during 171 procedures in 147 patients. Overall, 94 Y-stents and 52 tube stents (Novatech, LaCiotat, France) were placed into the central airways of patients having malign airway obstruction. A laser combined with stenting in 36 patients in the present study. Argon plasma coagulation (APC) was combined with stenting in 65 patients in the present study.   Cryotherapy was combined with stenting in 5 patients in the present study.	Mechanical debulking: Done as required. Laser therapy (Diode laser therapy): 250 procedures in 178 patients.   Cryotherapy: 93 procedures in 54 patients. Argon plasma coagulation: 373 procedures in 257 patients.	For follow up, a flexible bronchoscopy was used in 100 patients after they had stenting.
2.	Dutau H et al [9].	Not mentioned	Forty-three patients were free from any previous oncologic treatment. Of them, 23 patients (group 1) received first-line chemoradiation therapy (14 in the stent arm, 9 in the no stent arm). 20 patients (group 2) received first-line chemotherapy (9 in the stent arm, 11 in the no stent arm) after TB. The remaining 35 patients (group 3) (17 in the stent arm, 18 in the no stent arm) were either considered as failures of first-line oncologic treatment (31 patients) or candidates for palliative care alone (4 patients).	A total of 78 patients (64 males and 14 females) were included over 3 years. After randomization, 40 patients were included in the stent arm and 38 in the no stent arm. Silicone stents were provided by Novatech SA (La Ciotat, France).	A total of 38 patients in the stent arm underwent stent placement and 2 did not receive the allocated stent placement due to intraoperative complications.	Not mentioned	Not mentioned
3.	Grosu HB et al [10].	Not mentioned	Pre-procedure radiation therapy in 38 patients.	Patients were studied who underwent therapeutic bronchoscopy for malignant airway obstruction (including stent placement). For patients with malignant central airway obstruction, stents were placed if (1) there was pure extrinsic compression with > 50% airway occlusion, or (2) if adequate airway patency (> 50%) could not be achieved with ablative techniques alone, or (3) it was felt that airway re-occlusion would occur quickly if a stent was not placed following ablation for a mixed obstruction. Types of stents used: Ultraflex, Aero, Dumon tube stent, Silicone Y-stent and Polyflex.	24 patients underwent stent placement. Ultraflex: a total of 15 stents placed. Aero, a total of 9 stents placed. Dumon tube stent, 1 stent placed. Silicone Y-stent, 3 stents placed. Polyflex, 1 stent placed.	Seventeen of the 24 patients with stents (71%) had ablative therapies concurrent with stent placement.	Chemotherapy: Post procedure chemotherapy in 43 patients. Post procedure radiation therapy in 29 patients.
4.	Huang S et al [11].	The flexible bronchoscopy (BF 1T260, Olympus, Tokyo, Japan)	Not mentioned	Patients with lung and esophageal cancer who underwent stent placement were included in the study. The self-expanding covered metallic stent had a tracheal limb measuring 10 to 22 mm in diameter and 20 to 100 mm in length. For the Y stent, the diameter of the left or right main bronchi varied from 10 to 18 mm, and the length varied from 10 to 40 mm. The size of the stents was customized to fit different patients’ airways. Type of stents: Tube and Y shaped. Stent length: <60mm, 27 stents.  >60 mm, 15 stents.	Number of stents: 1, 46 patients. 2, 10 patients. Stents in right main bronchus: 31. Stent in carina: 14. Stent in main trachea: 32. Tube stent, 31 stents placed. Y shaped stent, 25 stents placed	Not mentioned	Not mentioned
5.	Iyoda A et al [12].	Rigid bronchoscopy under general anesthesia for patients undergoing silicone stent placement.	A total of 12 patients underwent chemoradiation prior to stent placement.	Patients with central airway obstruction due to thoracic malignancy were enrolled and underwent either silicone stent (SS) or metallic stent (MS) placement.	SS (number of stents): Dumon, 27. Dumon Y, 18. Ultraflex, 0. Aero, 0. MS (number of stents): Dumon, 0. Dumon Y, 0. Ultraflex 55. Aero, 6.	Not mentioned	14 patients required additional chemo after stent (8 patients who underwent silicone stent and 6 patients who underwent metallic stent placement.
6.	Lachkara S et al [13].	Rigid bronchoscope.	Previous chemo and/or radiotheraprior to stent placement: 9 patients receiving silicone Y stent and 20 patients receiving SEM Y stent placement.	Y shaped stent, silicon based or self-expanding metallic stent placement.	40 patients underwent silicone Y stent placementand 38 patients underwent SEM Y stent placement. 21 auto-expansive esophageal stents were placed after the bronchial stent procedure (9 in the silicone Y group and 12 in the SEM Y group).	Radiation therapy in 12 patients and 12 patients for silicone Y and SEM Y groups, respectively.   Mechanical and/or electrocoagulation debulking was performed in19 patients (55.9%) in the silicone Y group and in 19 patients (50%) in the SEM Y group.	After stenting 20 patients (58.8%) in the silicone Y group and 26 patients (68.4%) in the SEM Y group received oncological treatment, including chemotherapy in 18 and 22 patients respectively.
7.	Ma G et al [14].	Bronchoscope (LF-TP-model, Olympus company)	Not mentioned	Stent placement for malignant air way obstruction.   All cases were divided into three groups according to the location of the primary tumor: lung cancer group, esophageal carcinoma group and lymphoma group. Three cases with unknown pathologies were not categorized into any groups. Ultraflex self-expandable, non-membrane coated metallic stents were used for all patients.	Stent implantation was performed success- fully in all 52 cases.	Not mentioned	All 33 patients from the lung cancer and the esophageal carcinoma group received postoperative radiotherapy/ chemotherapy, while six patients from the lymphoma group received postoperative chemotherapy.
8.	Marchese R et al [15].	Rigid bronchoscopy (model 1T-180; Olympus America Inc., Melville, N.Y., USA) under local anesthesia.	Not mentioned	Fully covered SEMS Silamet stent placement in malignant airway obstruction.	Stents were implanted in 52 patients. Stents were inserted in the trachea (n = 19), in the main bronchi (n = 21) and in the peripheral bronchi (n = 31).	Laser Therapy: Laser (λ = 980 nm; Ceralas D50/980/600; Biolitech, Bonn, Germany) therapy was used in case of endoluminal lesions.	Three patients needed mechanical ventilation in the postoperative period for less than 8 hours.
9.	Marchese R et al [16].	Stenting procedures were performed using rigid bronchoscope (Dumon-Harrell type; Bryan Corp; Woburn, MA) under general anesthesia and jet ventilation.	Pre-procedural treatment 16 (30%): Chemotherapy 13 (25%) Chemoradiotherapy 3 (5%)	Both metallic and silicone stents were used: fully covered self-expandable metallic stent (SEMS) Silmet® (Novatech, La Ciotat, France); covered Ultraflex® (Boston Scientific, Natick, MA, USA); Dumon stents straight, Y-shape; and Oki stent (Novatech).	A total of 52 stents were placed. Silmet: Linear, 19 Conic, 6. Silicone: Oki, 14 Straight, 5 Y, 3. Ultraflex: 5.	Not mentioned.	Post-procedural treatment: 40 (75%) Chemotherapy 33 (63%). Radiotherapy 2 (3%). Surgery 4 (7%).
10.	Marchioni A et al [17].	A Dumon rigid bronchoscope (Efer Medical, La Ciotat, Cedex, France) under general anesthesia performed in all patients	Traditional chemo and radiotherapy: 55 (92%) patients in the integrated treatment group and 35 in the standard treatment. Immunotherapy: 11 patients (18%) were in the integrated treatment group and 6 (15%) in the standard treatment. Tyrosine kinase inhibitor: 12 patients (12%) in the integrated treatment group and 3 (8%) in the standard treatment.	Patients were divided into 2 groups. 1) integrated treatment-IT (patients undergoing endoscopic treatment plus chemotherapy/radiotherapy); 2) standard treatment-ST (chemotherapy/radiotherapy alone). In cases with extrinsic compression from malignant occlusion, or whenever indicated, a silicone stent (NOVATECH Doumon stents, Boston Medical Products, Inc., Westborough, MA, USA) was placed.	Total number of stenting procedures, 54 (90%). Y shaped stent, 24 (40%). Single, 34 (58%).	Bougies: 16 (46%). Laser + mechanical, 13 (37%). Laser Therapy: 6 (17%).	Not mentioned.
11.	Miyazawa T et al [18].	For stent insertion, a flexible bronchoscope was used in 24 instances, and a rigid bronchoscope was used in 10.	Surgery in 5 patients. Chemotherapy in 8 patients. Radiotherapy in 10 patients.	Implantation of Ultraflex Nitinol stent in malignant airway obstruction.	A total number of 54 Ultraflex stents placed of varying diameter and length.	In 11 patients, debulking was performed using Nd-YAG laser and/or mechanical debulking.	8 patients were subjected to additional radiotherapy/chemotherapy after stent implantation.
12.	Miyazawa T et al [19].	A flexible bronchoscope (BF 240; Olympus) was used to locate the lesion followed by rigid scope (EFER, La Ciotat, France) to place the stent.	Tracheal Stenosis: Chemotherapy, 15 patients. Radiotherapy, 17 patients. Carinal Stenosis: Chemotherapy, 10 patients. Radiotherapy, 11 patients. Bronchial Stenosis: Chemotherapy, 11 patients. Radiotherapy, 14 patients. Extensive Stenosis: Chemotherapy, 9 patients. Radiotherapy, 7 patients.	Dumon stents (Novatech, Aubagne, France) and uncovered Ultraflex stents (Boston Scientific, Natick, MA) placed in patients with tracheobronchial stenosis.	64 Dumon stents including 36 Y stents and 28 uncovered Ultraflex stents were placed.	Not mentioned	Not mentioned.
13.	Monnier P et al [20].	The rigid bronchoscope (Rigid step) was used 23 times and the flexible device (Tele step) was used 27 times.	Most of them had already undergone 1 or more treatments: 15 courses of radiotherapy, 11 pulmona1y resections, 10 palliative laser dilatations, 7 rounds of chemotherapy, and 4 insertions of another stent.	Use of covered Wallstent for the palliative treatment of inoperable tracheobronchial cancers.	50 Wallstents were inserted initially in 40 patients presenting with a tracheal or bronchial tumor.	Except in cases of pure extrinsic compression, the tracheal or bronchial lumen was initially reopened using an Nd-YAG laser.	Additional chemotherapy and/or radiation therapy in 21 patients.
14.	Nakajima Y et al [21].	Flexible bronchoscopy.	Chemotherapy: 9 patients. Radiotherapy: 13 patients. Esophagectomy, 5 patients. Lobectomy, 5 patients. Pneumonectomy, 3 patients.	Placement of Gianturco-Z tracheobronchial stent for malignant airway obstruction. More than one stent was used for complete coverage of the length of the stenosis for tracheal lesions. For lesions involving the tracheal bifurcation and extending into the left main bronchus, a 12-mm bronchial stent was used with a 15-mm tracheal stent partially overlapping the bronchial stent.	A total of 32 stents were placed.	Not mentioned	Patients experiencing stent breakage after 7 weeks analyzed: 3 underwent radiotherapy, 1 underwent bronchial arterial infusion chemotherapy and 3 patients underwent laser treatment.
15.	Oki M et al [22].	Rigid bronchoscopy	Not mentioned.	For airway stenosis, stenting was performed using a silicone straight stent (DUMON; Novatech, La Ciotat, France), silicone bifurcated stent (DUMON or OKI; Novatech), or self-expandable metal stent (Ultraflex, covered type; Boston Scientific, Natick, MA, USA).	Number of stents inserted: Silicone, 23. Straight stent, 2. Bifurcated stent, 12. Two bifurcated stents, 4. Straight stent and bifurcated stent, 3. Straight stent and two bifurcated stents, 2. Metallic, 7.	Bronchoscopic airway reestablishment using argon plasma coagulation, electrocautery, a Cryoprobe, a high-pressure balloon, or the bevel of a rigid bronchoscope prior to stent placement.	Chemo/radiotherapy performed in 21 (70%) patients. Only 3 of 8 patients (38%) who had undergone prior chemoradiotherapy received additional tumor-specific therapy, while 18 of 21 chemoradiotherapy-naïve patients (86%) could receive additional therapy.
16.	Özdemir C et al [23].	All procedures were performed using a rigid bronchoscope (Efer Dumon, EFER Endoscopy, La Ciotat, France) under general anesthesia.	Not mentioned	Self-expandable metallic stent (SEMS) placement for palliation of central airway obstruction.	9 patients received Y shaped SEMS. 2 patients received SEMS of 18 x 14 x 14 mm. 3 patients received SEMS of 20 x 14 x 14 mm.	Mechanical debulking or balloon dilatation: 9 patients. Laser Therapy: 4 patients. Argon plasma coagulation: 2 patients.	Not mentioned
17.	Razi SS et al [24].	Rigid bronchoscope	11 patients underwent chemotherapy and/or radiation prior to airway stenting.	Stents used for malignant airway obstruction were Ultraflex tracheobronchial stent (Bos- ton Scientific), Dynamic (Y) stent systems (Boston Scientific), and AERO stents (Merit Medical Endotek, South Jordan, UT).	Fifty patients received a total of 72 airway stents over a 2-year period, with 65 stents placed at the initial operation. Thirty-eight patients received a single stent, nine received 2 stents, and three patients received 3 stents at the initial operation.	If there was significant endobronchial tumor present, especially if it was felt that a stent could not be satisfactorily deployed, endobronchial tumor resection was performed before stenting (mostly done using bipolar cautery).	During the follow-up period, 10 patients (20%) underwent bronchoscopy evaluation with or without intervention due mucus plugging, stent migration, and for evaluation of disease progression seen on CT scan with planned intervention at the same time.   31 patients underwent chemo and/or radiotherapy after airway stenting.
18.	Righini C et al [25].	Early cases up to 2000 were treated under local anesthesia and using a flexible bronchoscope BF P40 (Olympus Optical, Tokyo, Japan). Subsequently, a rigid ventilating bronchoscope (F7.5 Karl Storz, Tuttingen, Germany) or flexible bronchoscope with intravenous general anesthesia.	Not mentioned	All patients in this study were not suitable for surgical resection and were treated with nitinol stent placement (Ultraflex Microinvasive, Boston Scientific, Watertown, MA).	Total number of stents placed: Trachea, 43. Tracheobronchial, 11. Bronchial, 15.	Balloon dilatation, mechanical debulking, electrosurgery, and laser photo resection as indicated.	Electrosurgery, laser photo resection, and mechanical debulking, were required in 5 patients after complications occurred.
19.	Saji H et al [26].	Rigid and flexible bronchoscopy was performed in almost all patients.	Not mentioned	Airway stenting for advanced lung cancer with central airway obstruction.	Silicon, metallic, or both types of stents were placed in 42 (60%), 19 (29%), or eight (11%) patients respectively. Trachea: 14 stents, 7 metallic and 7 silicon). Carina: 28 stents, 5 dynamic and 23 silicon Y). Right main bronchus, 17 stents, 6 metallic and 11 silicon. Left main bronchus, 17 stents, 15 metallic and 2 silicon). Trunchus intermedius: 4 stents, 2 silicon and 2 metallic. The number of stents required in a patient was single in 53 (83%) patients, double in 10 (14%) patients, and triple in two (3%) patients	Not mentioned	Not mentioned
20.	Tayama K et al [27].	Bronchoscopy was performed under local or intravenous anesthesia to inspect the stricture and clear the airway of any secretions.		Expandable metallic stent placement for central airway obstruction.	The number of stents placed per patient ranged from 1 to 4. A total of 32 stents placed in 20 patients	Laser Therapy: 15 patients with intraluminal obstruction disease. 8 received Nd:YAG laser vaporization before and after stent implement and one patient with extraluminal stenosis due to an adenoid cystic carcinoma received Nd:YAG laser therapy after stent insertion.	Not mentioned
21.	Verma A et al [28].	Rigid bronchoscopy. All other instruments were inserted through the lumen of the rigid bronchoscope.	Routine treatment including chemotherapy and radiation were provided to the patients.	Comparison of Nd:YAG laser therapy versus stent placement for central airway obstruction. 36 patients underwent laser therapy while 30 patients underwent stent placement. Silicone Dumon stents and Ultraflex metallic stents were used.	30 patients underwent stent placement. A total of 39 stents were placed in 30 patients.	2 patients in the stent group required balloon dilatation prior to stent placement. 6 patients underwent both stent and laser treatment.	4 patients in the laser group and 2 patients in the sent group required repeat intervention.
22.	Wilson GE et al [29].	Fiberoptic bronchoscope	Chemotherapy, 4 patients. Radiotherapy, 17 patients. Mechanical debulking: Pneumonectomy, 5 patients. Wedge resection, 1. Sigmoid colectomy, 1. Mastectomy, 2. Esophagogasterectomy, 3.	Use of expandable metal stents for large airway obstruction. Dimensions of stents: 20 mm (width) x 25 mm (length), 20 mm x 50 mm, 30 mm x 25 mm, and 30 mm x 50 mm. In general, the 20 mm width stents were used for obstruction in the main bronchi and 30 mm stents for obstruction in the trachea.	The stents were placed in the tracheo- bronchial tree as follows: Trachea, 19. Left main bronchus 13. Right main bronchus, 10. Both main bronchi, 7. Trachea and left main bronchus, 6. Trachea and right main bronchus, 2. trachea and both main bronchi, 1. The stents overlapped and placed in continuity with each other if the length of tumor was extensive. A total of 117 stents were placed (mean stents 2 per patient, range 1-4).	Not mentioned	Sixteen patients went on to receive radiotherapy and seven received chemotherapy.
23.	Yerushalmi R et al [30].	Olympus 240 video-flexible bronchoscopes (Olympus, Tokyo, Japan).	Not mentioned	Placement of metal Wallstents for malignant airway obstruction	Airway stents were used in 34 patients, including 2 who required 2 stents at different locations, and one who required 2 adjacent stents (total, 37 stents).	If necessary, the endoluminal tumor was resected using Nd:YAG laser or electrocautery. discharge. Eighteen patients (50%) received brachytherapy to the area of obstruction.	During follow-up, recurrent stenoses and obstructions were identified bronchoscopically and were treated by laser resection. All patients underwent at least one bronchoscopy for follow- up and maintenance, except for three who died before such intervention was indicated.
24.	Zwischenberger JB et al [31].	Fiberoptic bronchoscopy.	Radiotherapy, 3 patients.	Metallic stent placement to palliate large airway obstruction in advanced unresectable lung cancer.	Trachea, 1 patient. Main bronchi: Right, 5 patients. Left, 1 patient. Bilateral, 1 patient. Combination trachea and bilateral main bronchi, 1 patient. Combination right main and right upper lobe bronchi, 1 patient. Right upper lobe bronchus, 1 patient.	Not mentioned	Radiotherapy, 4 patients.
25.	Akram MJ et al [32].	Flexible bronchoscopy.	Chemotherapy: All patients. Radiotherapy: 48 patients. Mechanical debulking: 29 patients underwent surgery.   Electrocautery done prior to stenting to debulk those lesions which were found not amenable for stenting due to intraluminal and/or extraluminal tumor infiltration.	Fully covered self-expanding metallic stents (FC-SEMS). Variable sized stents were used depending upon scope movement, and distance of lesion from vocal cord and carina.	Left main bronchus stenting, 12 patients. Left lower lobe bronchus stenting, 1 patient. Right main bronchus stenting, 6 patients. Right lower lobe bronchus stenting, 1 patient. Left and right main bronchus stenting, 1 patient. Tracheal stenting, 27 patients. Tracheal and left main bronchus stenting, 3 patients.	11 patients went through both pre and post procedural chemo and radiotherapy.	Not mentioned.
26.	Bolliger CT et al [33].	All procedures were performed by rigid bronchoscopy under general anesthesia.	15 patients had received various cycles of chemo- and/or radiotherapy.	Use of Studded Polyflex stents for neoplastic obstruction of the central airways. The stents used were combinations of various diameters and lengths, with diameters varying from 10 to 18 mm, and lengths from 25 to 60 mm. A total of 27 stents were used.	A total of 27 stents were used. The stents were placed in the following positions: Right main bronchus, 10 stents. Left main bronchus, 8 stents. Trachea, 7 patients. Tracheobronchial, 2 stents.	Laser therapy used for resection of endoluminal components of the central Airway Obstruction.   Electrocautery used for resection of endoluminal components of the Central Airway Obstruction.	Bronchoscopy had to be performed 48 ± 24 hours after stent placement. 1 patient with central small-cell lung cancer who under- went radio-chemotherapy, 1 patient with tracheal carcinoma who underwent external beam irradiation.
27.	Chhajed PN et al [34].	Rigid bronchoscopy (Efer-Dumon, Karl Storz Optics; Germany) was performed under general anesthesia in the operating room. Laser ablation (Deka Medical Electronic Associates, Italy) was performed either through the rigid bronchoscope or via the flexible bronchoscope inserted in the rigid bronchoscope.	Not mentioned	Use of stent placement versus laser therapy for malignant airway stenosis. The Dumon stent in the trachea and the right bronchial tree, Ultraflex stent for lesions on the left side. Y stents (Dumon, Polyflex, Dynamic) were used for lesions involving the trachea and both the main bronchi. Overall, laser therapy was used in 127 procedures in 98 patients. Laser therapy as the only therapeutic modality was used during 62 out of 167 (37%) procedures.	108 total stents used. In total, 15 Y-stents and 93 tube stents (Dumon 34, Polyflex 13, Ultraflex 46) were placed. In three patients, two stents were inserted in one procedure. Stents were placed during 105 procedures in 93 patients. Only stent insertion was undertaken in 40 out of 167 (24%) procedures and combined laser followed by stent insertion was performed in 65 out of 167 (39%) procedures.	Not mentioned.	Not mentioned.