Robot-Assisted Correction of a Supra-Long Tracheal Stenosis Using C-Type Nickel-Titanium Alloy Exterior Stenting and Suspension Fixation Technique: A Case Report.

T-tubes and airway stents are commonly used but have limited effectiveness and frequent complications. A 50-year-old male patient presented with severe tracheal stenosis, affecting an 8.7 cm length of the airway. We employed an innovative approach known as external suspension fixation of tracheal stent using robotic assistance. This method involves surgically attaching the stent to the exterior of the trachea to provide support and stabilize the softened or collapsed tracheal segments. We designed a C-shaped nickel-titanium alloy exterior stent and successfully fixed it using robotic assistance. This intervention effectively restored tracheal function and led to a favorable postoperative recovery. The technique does not affect tracheal membrane function or airway mucociliary clearance. It could potentially be considered as a new option for treating long-segment benign tracheal softening or collapse.

Spinal cord ischemia following laryngotracheal reconstruction surgery: a case report.

We present a 20-year-old patient with subglottic and tracheal stenosis was taken for a tracheal resection and end-to-end anastomosis. The patient's neck was positioned in hyperflexion using chin stitches to minimize tension at the anastomosis. On post-operative period, the patient developed paresthesias in upper and lower extremities associated with motor weakness. Magnetic resonance imaging was performed showing lesions compromising ventral spinal cord at the level of C4-C5 and C6-C7. Chin stitches were removed and neck flexion was reduced. The patient remained in the intensive care unit with vasopressors, physical therapy and intravenous fluid-therapy to maintain mean arterial pressure above 90 mmHg. After 3 weeks, the patient was discharged with no neurologic deficit. There are few cases reported of acute ischemic spinal injury following tracheal reconstruction. If this complication arises, neck posture should be corrected, maintenance of MAP above 90 mmHg and implementation of early physical therapy is key to improve neurologic outcomes.

Slide tracheoplasty for congenital tracheal stenosis: A systematic review.

INTRODUCTION: Slide tracheoplasty has become the gold standard surgery for congenital tracheal stenosis (CTS). This condition is rare and the surgery can be challenging and is performed by experienced surgeons in tertiary centers. A few reports involving relatively small cohorts have been published. The aim of this review is to evaluate the post-operative mortality and morbidity of pediatric slide tracheoplasty for CTS. METHODS: A systematic literature review was performed according to PRISMA guidelines. The Medline and EMBASE databases were screened using a search strategy defined in collaboration with a librarian. We included articles reporting the post-operative mortality rate of slide tracheoplasties for treatment of CTS in children, when at least 10 patients were included. RESULTS: A total of 932 articles were reviewed, and 15 studies were eligible with a total of 845 patients. The overall post-operative mortality rate was 9.3 %, and most deaths were airway related. The open revision surgery rate after surgery was 2.8 % and the endoscopic revision rate was 27.6 %. DISCUSSION: This study highlights key factors to consider before the surgery and helps anticipate post-operative follow-up considerations for children with CTS. Several factors were identified as predictors of mortality including young age, weight at the time of surgery and association with lung hypoplasia or aplasia. CONCLUSION: Although slide tracheoplasty has gained popularity in recent years due to better outcomes, it remains a major surgery with mortality risk and the need for multidisciplinary management.

Impact of preoperative respiratory distress on outcomes of slide tracheoplasty.

OBJECTIVES: Children with congenital tracheal stenosis born in the developing world face a high risk of mortality due to limited access to proper treatment. Patients who required preoperative respiratory support were suspected to have poor survival after slide tracheoplasty; however, this was not clearly demonstrated in the previous studies. This study aims to investigate the impact of preoperative respiratory conditions on outcomes of slide tracheoplasty. METHODS: From 2016 to 2022, children who underwent slide tracheoplasty were retrospectively reviewed. Patients with respiratory distress requiring emergency operations (group A) were compared with patients in stable condition who were scheduled for surgery (group B). RESULTS: Perioperative results revealed that group A (n = 43) had a longer bypass time (P < 0.001), operation time (P = 0.01), postoperative ventilation time (P < 0.001) and length of intensive care unit stay (P = 0.00125) than group B (n = 60). The early mortality rate was 7.8%, and the actuarial 5-year survival rate was 85.3%. The cumulative incidence test revealed that group A was highly significant for overall mortality [sudistribution (SHR) 4.5; 95% confidence interval (CI) 1.23-16.4; P = 0.023]. Risk factors for overall mortality were prolonged postoperative ventilation time (hazard ratio 3.86; 95% CI 1.20-12.48; P = 0.024), bronchial stenosis (hazard ratio 5.77; 95% CI 1.72-19.31; P = 0.004), and preoperative tracheal mucositis (hazard ratio 5.67; 95% CI 1.51-21.31; P = 0.01). Four patients needed reintervention during a follow-up of 28.4 months (interquartile range 15.3-47.3). CONCLUSIONS: Preoperative respiratory distress negatively affected the outcomes of patients who required slide tracheoplasty. Therefore, early detection of congenital tracheal stenosis and aggressive slide tracheoplasty are crucial and obligatory to enhance long-term survival in this lethal congenital airway disease.

Biodegradable tracheal stents: our ten-year experience with adult patients.

BACKGROUND: Biodegradable (BD) stents made from polydioxanone have been used only in human airways. These stents combine the advantages of classical tracheal stents, and fewer side effects are expected due to their biocompatibility and their time-limited presence in airways. However, new clinical consequences have arisen. Here, the authors share their experiences with BD stents for tracheal indications, focusing on their safety and efficacy. METHODS: This was a retrospective review of a collected database of adult patients who underwent implantation of biodegradable tracheal stents between September 2013 and December 2022 at the Department of Respiratory Medicine of the 1st Faculty of Medicine in Prague and Thomayer University Hospital. The indications included functionally significant nonmalignant tracheal stenosis and tracheomalacia. Self-expandable, biodegradable, polydioxanone tracheal stents manufactured by ELLA-CS Ltd. (Hradec Kralove, Czech Republic) were implanted during rigid bronchoscopy under general anaesthesia. All patients were followed up in the department and were provided with the necessary care. The main efficacy and safety parameters and relationships were analysed using descriptive statistics and Fisher´s exact, Wilcoxon and Kruskal‒Wallis tests. RESULTS: A total of 65 stents were implanted in 47 adult patients. During the first two months after implantation, when adequate function was expected, the stent was found to be effective in 26 out of 39 patients who completed this period (66.7%). The clinical effectiveness reached 89.7%, as early restenoses were mostly mild and necessitated treatment in only 4 patients. The frequencies of significant mucostasis, migration and granulation tissue growth were 2.6%, 7.5% and 23.1%, respectively, during this period. Thirty-four participants completed the half-year follow-up period after the first or second stent insertion, and some were followed up beyond this period. Poor control of symptoms, the development of restenosis and the need for interventions were characteristic of this period as the stents degraded. Twenty-two patients who experienced remodelling or stabilization of the tracheal lumen achieved a stent-free state. Seven patients underwent subsequent surgical treatment. CONCLUSIONS: BD stents are safe and provide adequate tracheal support until they begin to degrade. The use of BD stents necessitates close monitoring of patients and accurate treatment of possible restenosis. TRIAL REGISTRATION: Based on project NT14146 - Biodegradable stents in the management of the large airways (2013-2015, MZ0/NT), registered on May 1, 2013, in the Research and Development and Innovation Information System of the Czech Republic and at ClinicalTrials.gov (reg. no. NCT02620319, December 2, 2015).

Difficult endotracheal intubation in a patient with progressed tracheobronchopathia osteoplastica: A case report.

Tracheobronchopathia osteoplastica is a rare condition involving large airways with multiple bone and cartilage nodules in the tracheobronchial submucosa. This can cause tracheal stenosis, leading to difficulty in endotracheal intubation. A 79-year-old female patient, who had a history of successful endotracheal intubation for general anesthesia 8 years prior, was scheduled for abdominal surgery. Preoperative chest computed tomography and bronchoscopy revealed slight progression of tracheobronchopathia osteoplastica. Attempts to intubate with a smaller endotracheal tube failed; even the smaller endotracheal tube could barely pass. Mechanical ventilation was successfully administered and the surgery was completed without complications. The use of a smaller endotracheal tube may be beneficial for managing difficult airways in patients with tracheobronchopathia osteoplastica. Chest CT and bronchoscopic examination may be beneficial for evaluating the airway and determining the most appropriate airway management strategy. However, relying solely on these measures may lead to unexpected challenges because there is no established method to evaluate airway in patient with tracheobronchopathia osteoplastica. It is crucial for anesthesiologists to be aware of the potential existence of rare conditions such as tracheobronchopathia osteoplastica and be prepared to handle anticipated or unanticipated difficult airway management.

Management and Discussion of COVID-19 Related Tracheal Stenosis: A Single Center Retrospective Review.

SARS-CoV-2 virus has led to an unprecedented amount of tracheal stenosis. Rigid bronchoscopy can serve as a curative measure or bridge therapy to tracheal resection. We also briefly discuss the pathophysiology of tracheal stenosis from prolonged intubation and SARS-CoV-2 virus. This should be differentiated from other forms of airway obstruction such as tracheobronchomalacia which would be considered a pseudo-tracheal stenotic disease. The aim of this study is to evaluate stenosis that is unable to be improved with positive airway pressure or "PAP" therapies and required stenting and/or subsequent tracheal resection. By performing Rigid Bronchoscopy and subsequent stenting of airways, we demonstrated outcomes for long term airway patency regarding patients who were intubated secondary to the SARS-CoV-2 virus. We demonstrate superb outcomes in a consecutive case series of 6 patients managed with rigid bronchoscopy, airway stent and tracheal resection. The patients were all managed from a pulmonary perspective by the physicians mentioned in this study.

[Tracheobronchial involvement in relapsing polychondritis and differential diagnoses]. / Atteinte trachéo-bronchique de la polychondrite atrophiante et diagnostics différentiels.

Relapsing polychondritis is a systemic auto-immune disease that mainly affects cartilage structures, progressing through inflammatory flare-ups between phases of remission and ultimately leading to deformation of the cartilages involved. In addition to characteristic damage of auricular or nasal cartilage, tracheobronchial and cardiac involvement are particularly severe, and can seriously alter the prognosis. Tracheobronchial lesions are assessed by means of a multimodal approach, including dynamic thoracic imaging, measurement of pulmonary function (with recent emphasis on pulse oscillometry), and mapping of tracheal lesions through flexible bronchoscopy. Diagnosis can be difficult in the absence of specific diagnostic tools, especially as there may exist a large number of differential diagnoses, particularly as regards inflammatory diseases. The prognosis has improved, due largely to upgraded interventional bronchoscopy techniques and the development of immunosuppressant drugs and targeted therapies, offering patients a number of treatment options.

Involvement of PD-1+CD4+ T cells in the development of traumatic tracheal stenosis by regulating the IL-17/STAT3 pathway.

Studies have highlighted an upregulation of PD-1 expression in CD4+ T cells, which accelerates lung fibrosis by activating the IL-17/STAT3 pathway, leading to IL-17A and TGF-ß1 secretion. However, the relation with traumatic tracheal stenosis (TS) remains unexplored. Our analysis found significant increases in PD-1+CD4+ T cells, IL-17A, and TGF-ß1 in the TS patients (n = 10). The cellular model used CD4+ T cells co-cultured with bronchial fibroblasts while the animal model used a nylon brush to scrape the damaged tracheal mucosa. Interventions with PD-1 and STAT3 inhibitors both in vitro (n = 5) and in vivo (n = 6) showed decreased expression of TGF-ß1 and IL-17A in CD4+ T cells, decreased collagen I synthesis in vitro, and reduced tractal fibrosis in vivo. Furthermore, PD-1's modulation of the STAT3 was evident. This research unveils PD-1+CD4+ T cells' role in TS, thus suggesting a novel immunotherapeutic strategy to counteract tracheal fibrosis.

Silicone stent placement for tracheal stenosis induced by a giant goiter due to Graves' disease: a case report.

Background: Although thyroid tumors with tracheal stenosis are occasionally encountered, severe tracheal stenosis caused by benign thyroid tumors is rare. We herein describe a case in which a silicone tracheal stent was placed for severe tracheal stenosis induced by a giant goiter due to Graves' disease. Case Description: A 93-year-old woman had been receiving thiamazole treatment for Graves' disease with a thyroid goiter for 32 years. She emergently presented to the hospital with sudden difficulty breathing and the temporary loss of consciousness. Although marked stridor was heard, the patient's respiratory status was stable in the first visit. Computed tomography revealed a giant thyroid goiter that extended to the mediastinum. The trachea was compressed by the sternal notch and thyroid gland, resulting in severe stenosis, and the tracheal lumen was only 1 mm. Surgical thyroidectomy was expected to be difficult due to the high risk of complications associated with the large size of the goiter and advanced age of the patient. Therefore, we decided to place a tracheal stent. A silicone stent (Dumon tube®) was inserted into the site of tracheal stenosis under general anesthesia. After stent placement, respiratory distress symptoms improved, and no complications were observed. Three months after stent placement, the stent opening side was narrowed due to defective granulation and, thus, was cauterized with argon plasma coagulation. Conclusions: We encountered a patient who was treated by tracheal silicone stent placement for severe tracheal stenosis induced by a giant goiter due to Graves' disease. A silicone stent effectively secures the airway for benign thyroid tumors that cause severe airway stenosis.

Choice of suture technique may mitigate figure-of-8 deformity in slide tracheoplasty.

OBJECTIVES: To demonstrate varying degrees of immediate postoperative figure of 8 deformity following three different methods of tracheal suturing. STUDY DESIGN: Comparative ex-vivo study. METHODS: A fresh, unfixed rabbit trachea was harvested and bisected at its midpoint. The posterior membranous trachea was excised from both segments to mimic the anatomy of complete tracheal rings following longitudinal release. A slide tracheoplasty was performed on the same tracheal segments as an internal control, using three different methods of closure: simple running, running horizontal mattress, and a modified baseball stitch. Endoscopic and external photographs were taken immediately following repair to document the effect of closure technique on external and endoluminal anatomy. RESULTS: A simple running closure, in which traveling occurs between needle passes, showed the greatest degree of postoperative figure of 8 deformity. A running horizontal mattress suture closure showed less deformity and a modified running closure, in which traveling occurs within needle passes, showed the least deformity. CONCLUSIONS: Our study suggests that a minor modification of standard running closure techniques may help limit the common figure-of-8 deformity often noted following slide tracheoplasty. LAY SUMMARY: Figure of-8 deformity is a problem that can occur when repairing a narrow trachea referred to as tracheal stenosis. This deformity may be prevented using particular suture techniques which may decrease the likelihood that the trachea becomes blocked again following repair.

[Review of surgical treatment of suprastomal collapse in tracheostomised children]. / Übersichtsarbeit zur chirurgischen Behandlung des suprastomalen Kollapses bei tracheotomierten Kindern.

BACKGROUND: Suprastomal collapse (SSC) is considered a major late complication of paediatric tracheostomy and can be responsible for decannulation failure in up to 20% of tracheostomised children. Depending on the severity of SSC, surgery may be required. Various strategies and techniques are available, of which the treating with airway team should be aware. OBJECTIVE: This article intends to summarise the aetiology of SSC, its classification, clinical presentation, and the gold standard diagnostic and therapeutic algorithms according to the current literature. MATERIALS AND METHODS: A panel of experts reviewed the available literature on SSC. Published evidence on the different surgical techniques and their advantages and disadvantages was reviewed in detail, and a treatment algorithm created. RESULTS: The gold standard diagnostic procedure for SSC is flexible transnasal laryngotracheoscopy in spontaneous breathing followed by microlaryngoscopy (MLS) under general anaesthesia. Two main types of SSC can be differentiated, which differ in terms of surgical treatment. Purely anterior SSC is usually treated by tracheoplasty using an anterior costal cartilage graft (ACCG). Simple closure of the tracheostomy or excision of SSC with a potassium-titanyl-phosphate (KTP) laser are also described as less invasive approaches. For anterolateral SSC, segmental tracheal resection with end-to-end anastomosis or tracheoplasty with ACCG represent promising treatment options. Tracheal reinforcement with absorbable microplates is also discussed in the literature. With both types of SSC and depending on severity and the age of the child, a watch-and-wait strategy should always be considered. CONCLUSION: Dynamic airway endoscopy in spontaneous breathing followed by MLS in general anaesthesia should always be performed before decannulation. It is particularly important to visualise all segments of the airway during spontaneous breathing. The decision regarding the best surgical option for each child is based on the type and localisation of SSC, as well as on the patient's medical and surgical history and age.

Post-Tracheostomy Steroid Nebulization: A Retrospective Analysis on Postoperative Complications.

The primary objective of this research was to meticulously evaluate the therapeutic potential of steroid nebulization, administered over a 2-week period post-tracheostomy, in attenuating postoperative complications with a concentrated emphasis on tracheal stenosis. The study spanned three years, commencing in 2019 and concluding in 2022, examining a patient cohort of 400 individuals. Utilizing a retrospective cohort methodology, the participants were systematically stratified into two cohorts: those subjected to steroid nebulization (n = 200) and a control group (n = 200). Adverse outcomes were bifurcated into minor complications, which encompass stomal infections and inflammations, and major complications, which include bleeding, tracheoesophageal fistula, and tracheal stenosis. These complications were evaluated at distinct post-operative junctures: 1 week, 1 month, 3 months, and 6 months. The primary outcome was deduced through a rigorous multivariate logistic regression model, incorporating variables such as age, sex, and the diagnosis of chronic obstructive pulmonary disease (COPD). Analytical data unveiled that the cohort administered with steroid nebulization manifested a statistically significant diminution in the incidence of complications when juxtaposed with the control group (25 vs. 38%). Predominantly, the incidence of tracheal stenosis was discernibly lower in the steroid nebulization group (10 vs. 22%). The multivariate analytical framework further corroborated the pivotal role of steroid nebulization in substantially reducing the propensity for tracheal stenosis. The therapeutic intervention of steroid nebulization in the aftermath of a tracheostomy procedure presents a commendable avenue in curtailing major complications, with an acute focus on tracheal stenosis. To fortify these preliminary findings, it is quintessential to undertake more exhaustive studies, such as randomized controlled trials, to ascertain the optimal regimen concerning nebulization's timing, dosage, and duration.

Aerodynamic evaluation of surgical design for the stenosis correction of airway.

Introduction: Congenital tracheal stenosis (CTS) is a rare but life-threatening disease that can lead to respiratory dysfunction in children. Obstructive sleep apnea syndrome (OSAS) in children is characterized by prolonged partial upper airway obstruction and/or intermittent complete obstruction. Both of the diseases require surgical intervention. Although respective treatments of these two diseases are clear, there is a lack of literature discussing the surgical treatment of patients with CTS complicated by OSAS. Methods: We conducted a patient-specific study of patient with CTS complicated by OSAS. Computer-aided design was used to simulate surgical correction under different surgical sequences. Computational fluid dynamics was used to compare the outcomes of different sequences. Results: Aerodynamic parameters, pressure drop, velocity streamlines, wall shear stress (WSS), and the ratio of airflow distribution and energy loss rate were evaluated. An obvious interaction was found between the two diseases in different surgical sequences. The order of correction for CTS or OSAS greatly affected the aerodynamic parameters and turbulence flows downstream of tracheal stenosis and upstream of epiglottis. The CTS and OSAS had mutual influences on each other on the aerodynamic parameters, such as pressure drops and WSS. Discussion: When evaluating the priority of surgical urgency of CTS and OSAS, surgeons need to pay attention to the state of both CTS and OSAS and the physiological conditions of patients. The aerodynamic performance of the uneven airflow distribution and the potential impact caused by the correction of CTS should be considered in surgical planning and clinical management.

Tracheal Stenosis in Open Versus Percutaneous Tracheostomy.

OBJECTIVE: This study aims to investigate if there is an increased risk of developing tracheal stenosis after tracheostomy with an open versus percutaneous tracheostomy. METHODS: The patient cohort included patients receiving open or percutaneous tracheostomies at Catholic Health Initiatives Midwest facilities from January 2017 to June 2023. The primary aim was to compare the differences in the risk of developing tracheal stenosis between open and percutaneous tracheostomy techniques. Between-technique differences in the risk of developing tracheal stenosis were assessed via a Cox proportional hazard model. To account for death precluding patients from developing tracheal stenosis, death was considered a competing risk. RESULTS: A total of 828 patients met inclusion criteria (61.7% open, 38.3% percutaneous); 2.5% (N = 21) developed tracheal stenosis. The median number of days to develop tracheal stenosis was 84 (interquartile range: 60 to 243, range: 6 to 739). Tracheal stenosis was more frequent in patients who received a percutaneous tracheostomy (percutaneous: 3.5% vs. open: 2.0%); however, the risk of developing tracheal stenosis was statistically similar between open and percutaneous techniques (HR: 2.05, 95% CI: 0.86-4.94, p = 0.108). CONCLUSIONS: This study demonstrates no significant difference in the development of tracheal stenosis when performing an open versus a percutaneous tracheostomy. Tracheal stenosis is a long-term complication of tracheostomy and should not influence the decision about the surgical technique used.

Airway collapse hinders recovery in bronchoscopy therapy for postintubation tracheal stenosis patients.

BACKGROUND: Expiratory central airway collapse (ECAC) following postintubation airway stenosis (PITS) is a rare phenomenon. The impact of airway malacia and collapse on the prognosis and the success rate of bronchoscopic interventional therapy in patients with PITS had been inadequately investigated. OBJECTIVE: The aim of this research was to assess the influence of airway malacia and collapse on the efficacy of bronchoscopic interventional therapy in patients with PITS. DESIGN: This retrospective analysis examined the medical documentation of individuals diagnosed with PITS who underwent bronchoscopic intervention at the tertiary interventional pulmonology center of Emergency General Hospital from 2014 to 2021. MAIN OUTCOME MEASURES: Data pertaining to preoperative, perioperative, and postoperative stages were documented and subjected to analysis. RESULTS: The patients in malacia and collapse group (MC group) exhibited a higher frequency of perioperative complications, including intraoperative hypoxemia, need for reoperation within 24 h, and postoperative intensive care unit admission rate (P < 0.05, respectively). Meanwhile, patients in group MC demonstrated significantly worse postoperative scores (higher mMRC score and lower KPS score) compared to those in pure stenosis group (P < 0.05, respectively), along with higher degrees of stenosis after treatment and a lower success rate of bronchoscopic intervention therapy cured (P < 0.05, respectively). Pearson analysis results showed that these terms were all significantly correlated with the occurrence of airway malacia and collapse in the airway (P < 0.05, respectively). CONCLUSION: The presence of malacia or collapse in patients with PITS was associated with increased perioperative complications following bronchoscopic interventional therapy, and significantly reduced the long-term cure rate compared to patients with pure tracheal stenosis. Trial registration Chinese Clinical Trial Registry on 06/12/2021. REGISTRATION NUMBER: ChiCTR2100053991.

Use of the Disposcope endoscope for awake orotracheal intubation in an elderly patient with a large vocal cord polyp -a case report.

BACKGROUND: Vocal cord polyps are commonly encountered in the otorhinolaryngology department. The risk of anesthesia is high in patients with large vocal cord polyps. Awake intubation with appropriate airway tools provides a favorable safety profile. CASE: We present the case of a 60-year-old male patient who had been suffering from a large vocal cord polyp for 16 years. Electronic laryngoscopy revealed that the vocal cord polyp was approximately 1.5 cm in diameter. The polyp had a pedicle and demonstrated synchronous motion with respiratory excursion. It covered almost the entire glottic area during inspiration and moved away from the glottis during expiration. A Disposcope endoscope was used for awake tracheal intubation, and the surgery was completed successfully. CONCLUSIONS: The Disposcope endoscope can be a useful option for awake orotracheal intubation in cases of anticipated difficult intubation and difficult facemask ventilation.

Regeneration Process of an Autologous Tissue-Engineered Trachea (aTET) in a Rat Patch Tracheoplasty Model.

The treatment of long-tracheal lesion is difficult because there are currently no viable grafts for tracheal replacement. To solve this problem, we have developed an autologous Tissue-Engineered Trachea (aTET), which is made up of collagenous tissues and cartilage-like structures derived from rat chondrocytes. This graft induced successful long-term survival in a small-animal experiment in our previous study. In this study, we investigated the regeneration process of an aTET to attain reproducible success. We prepared an aTET by using a specially designed mold and performed patch tracheoplasty with an aTET. We assigned twenty-seven rats to three groups according to the three types of patch grafts used: aTET patches (the aTET group), fresh tracheal autograft patches (the Ag group), or polylactic acid and polycaprolactone copolymer sheets (the PPc group). In each group, gross and histological evaluations were performed at 1 month (n = 3), 3 months (n = 3), and 6 months (n = 3) after implantation. We obtained high survival rates in all groups, but only the PPc group attained thick tracheal walls with granular tissues and no tracheal regeneration. On the other hand, the aTET and Ag groups reproducibly achieved complete tracheal regeneration in 6 months. So, an aTET could be a promising candidate for tracheal regeneration grafts.