Development of a survival animal model for subglottic stenosis

Effects of Inhaled Dexamethasone/Ciprofloxacin on Acute Subglottic Stenosis in a Rabbit Model

Objectives

Subglottic stenosis (SGS) is a challenging complication post-airway interventions. Effective preventive strategies lack sufficient evidence. This study investigated the preventive effect of inhalation therapy with dexamethasone/ciprofloxacin on acute SGS in a rabbit model.

Methods

Twenty New Zealand White rabbits underwent subglottic injury via endoscopy and received inhalation therapy twice daily starting on the injury day. Group 1 (n = 4) received saline for 5 days and was sacrificed on day 5; Group 2 (n = 4) received dexamethasone/ciprofloxacin for 5 days and was sacrificed on day 5; Group 3 (n = 4) received the same therapy for 5 days and survived for one week, and was sacrificed on day 15; Group 4 (n = 4) received the therapy for 10 days and was sacrificed on day 15; Group 5 (n = 4) received the therapy for 10 days and survived for one week, and was sacrificed on day 22. Rabbits underwent repeat endoscopy and were euthanized at the designated time point. Histological measurements were analyzed statistically.

Results

Histological analysis revealed median cricoid lumen measurements of 20.01 ± 1.42 mm2 for group 1, 17.94 ± 3.05 mm2 for group 2, 14.84 ± 2.55 mm2 for group 3, 17.18 ± 5.31 mm2 for group 4, and 11.87 ± 5.68 mm2 for group 5. No significant differences were found between treatment and control groups (p = 0.486) or between 5-day and 10-day treatments (p = 0.686). Multivariate statistical analysis indicated that cessation of inhalation therapy (p < 0.05) and prolonged survival (p < 0.05) were associated with shorter cricoid lumen measurements.

Conclusion

Short-term dexamethasone/ciprofloxacin inhalation does not prevent acute SGS. No improvements in cricoid lumen diameter were found. Extended survival correlated with shorter cricoid lumen, suggesting SGS progression is time dependent.

Level of Evidence

NA.

Establishment of a survival rabbit model for laryngotracheal stenosis: A prospective randomized study

Objective

To develop a reproducible survival rabbit model for laryngotracheal stenosis (LTS).

Methods

Seventy New Zealand white (NZW) rabbits were randomly divided into experimental groups (n = 30) and a control group (n = 40). In experimental groups, a nylon brush was inserted retrograde from the tracheotomy through the subglottis and rotated until a full layer circumferential mucosal injury to cartilage exposure, assisted by fiberoptic laryngoscopy (FOL) visualization. Experimental group 1 (n = 10), rotated 10 times; group 2 (n = 20), rotated 20 times. The control group underwent tracheotomy only without nylon brush scraping. The rabbits underwent FOL at 1st, 4th, 8th, and 12th week postinjury respectively to observe the formation of LTS. They were euthanized and the larynxes and tracheas were subjected to gross and histopathological examination at 12 weeks postinjury.

Results

The control group all survived, while five cases in experimental groups died from LTS and/or mucous plug. Histological observation showed that the control group had intact laryngotracheal mucosal epithelium without any stenosis; the experimental groups showed proliferation of fibroblasts and thickening of collagen fibers. The mean stenosis in control group was 9.31 ± 0.98%, while that in experimental group 1 was 32.78 ± 7.07% and 58.25 ± 8.96% in experimental group 2. The difference between the three groups was statistically significant (χ 2 = 47.98, p < .05).

Conclusions

We successfully developed a reproducible survival rabbit model for LTS using a nylon brush through FOL visualization combined with tracheostomy. This model can provide a mature and stable animal model for the exploration of wound-healing pathophysiology and the effect of interventions.

Level of evidence

NA.

The Wound Healing of Autologous Regenerative Factor on Recurrent Benign Airway Stenosis: A Canine Experimental and Pilot Study

INTRODUCTION

Benign airway stenosis (BAS) is a severe pathologic condition. Complex stenosis has a high recurrence rate and requires repeated bronchoscopic interventions for achieving optimal control, leading to recurrent BAS (RBAS) due to intraluminal granulation.

METHODS

This study explored the potential of autologous regenerative factor (ARF) for treating RBAS using a post-intubation tracheal stenosis canine model. Bronchoscopic follow-ups were conducted, and RNA-seq analysis of airway tissue was performed. A clinical study was also initiated involving 17 patients with recurrent airway stenosis.

RESULTS

In the animal model, ARF demonstrated significant effectiveness in preventing further collapse of the injured airway, maintaining airway patency and promoting tissue regeneration. RNA-seq results showed differential gene expression, signifying alterations in cellular components and signaling pathways. The clinical study found that ARF treatment was well-tolerated by patients with no severe adverse events requiring hospitalization. ARF treatment yielded a high response rate, especially for post-intubation tracheal stenosis and idiopathic tracheal stenosis patients.

CONCLUSION

The study concludes that ARF presents a promising, effective, and less-invasive method for treating RBAS. ARF has shown potential in prolonging the intermittent period and reducing treatment failure in patients with recurrent tracheal stenosis by facilitating tracheal mucosal wound repair and ameliorating tracheal fibrosis. This novel approach could significantly impact future clinical applications.

The role of tracheal wall injury in the development of benign airway stenosis in rabbits

To investigate the role of tracheal wall injury in the development of benign airway stenosis in rabbits. Prospective study. We injured the tracheal walls of 28 New Zealand white rabbits using four different methods. Experimental group: Group A (n = 7, mild injury of tracheal mucosa by ordinary brush under bronchoscopy); Group B (n = 7, severe injury of tracheal mucosa by nylon brush under tracheotomy); Group C (n = 7, tracheal cartilage was injured by vascular clamp after tracheotomy); Group D (n = 7, the tracheal cartilage was injured with vascular forceps and the tracheal mucosa was injured with a nylon brush after tracheotomy). Bronchoscopy was performed on each experimental rabbit at 1, 2, 3 and 4 weeks after operation. High-resolution computed tomography (HRCT) and endobronchial optical coherence tomography (EB-OCT) were performed at 4 weeks, and the rabbits were sacrificed after the examination. Their gross and histological findings were comparatively determined whether the experimental rabbit stenosis was established. No airway stenosis was observed in group A. In group B, 28.57% of experimental rabbits developed tracheal stenosis (granulation tissue proliferation was observed in rabbits No. 2 and No. 6 at 1, 2 and 3 weeks after operation, and the tracheal scar contracture was observed in No.6 rabbit at 4 weeks after operation). Fourteen rabbits in group C and group D had tracheal stenosis caused by granulation tissue proliferation at 1, 2 and 3 weeks after operation. At the fourth week after operation, 71.43% of experimental rabbits had tracheal stenosis due to granulation tissue hyperplasia, 7.14% of experimental rabbits had tracheal stenosis due to scar contracture and granulation hyperplasia, and 21.43% of experimental rabbits had tracheal stenosis due to scar contracture. EB-OCT scan showed that the cartilage layer with low signal reflection band was discontinuous. The injury of cartilage is the key factor of benign airway stenosis. Acute injury of airway mucosa alone is unlikely to cause airway stenosis, but combined with cartilage injury may aggravate airway stenosis. EB-OCT can clearly identify the airway layers of rabbits, which is helpful to evaluate the damage of tracheal cartilage and mucosa. The diagnostic potential of this technique makes EB-OCT a promising approach for the study and monitoring of airway diseases.

Clinical, Histological, and Profibrotic Extracellular Matrix Protein Changes in a Model of Tracheal Stenosis Induced by Cervical Tracheal Autotransplantation

BACKGROUND

Tracheal stenosis (TS) is a complication of prolonged intubation, tracheotomy, and tracheal surgery that compromises the vascular supply. Animal models are essential for studying its pathophysiology and the effect of interventions.

OBJECTIVE

To establish a TS model in rats secondary to tracheal autotransplantation with a graft submerged in bleomycin (Atx-Bleo). Additionally, to evaluate the clinical and histological changes, as well as the expression of newly formed collagen (NFC), isoforms of transforming growth factor beta (TGFβ), fibronectin (FN), elastin (ELN), integrin β1 (ITGβ1), and matrix metalloproteinase 1 (MMP1) in TS.

METHODS

Twenty Wistar rats were divided into three groups: group I (n = 20) control; group II (n = 10) end-to-end anastomosis of the trachea (tracheoplasty); and group III (n = 10) Atx-Bleo. The animals were evaluated clinically, tomographically, macroscopically, morphometrically, and microscopically. NFC deposition, and the expression of profibrotic and antifibrotic proteins were evaluated in tracheal scars.

RESULTS

All animals survived the surgical procedure and the study period. Compared with the other study groups, the Atx-Bleo group developed TS and fibrosis, exhibited higher expression of NFC, TGFβ1, TGFβ2, FN, ELN, and ITGβ1, and mild expression of TGFβ3 and MMP1 (p < 0.005; analysis of variance, Dunnett and Tukey tests).

CONCLUSION

Atx-Bleo in TS model rats produces tomographic and histological changes, and induces the upregulation of profibrotic proteins (TGFβ1, TGFβ2, collagen, FN, ELN, ITGβ1) and downregulation of antifibrotic proteins (TGFβ3, MMP1). Therefore, this model may be used to test new pharmacological treatments for reversing or preventing TS, and conduct basic studies regarding its pathophysiology.

Establishing an Endoscopic Chronic Subglottic Stenosis Rabbit Model

OBJECTIVES/HYPOTHESIS

To develop a reproducible and consistent chronic subglottic stenosis (SGS) in an endoscopic animal model.

STUDY DESIGN

Prospective study.

METHODS

We conducted a prospective study using New Zealand white rabbits. Chronic SGS was induced endoscopically by Bugbee electrocautery to 50% to 75% of the subglottic area's circumference, followed by 4-hour endotracheal intubation. The rabbit airways were endoscopically assessed and sized with uncuffed endotracheal tubes (ETTs) before the injury, during follow-up, and at the endpoints. There were four endpoints: 2, 4, 6, and 8 weeks post SGS induction. Animals were humanely euthanized for histopathological examination of the subglottic injury site and microscopic measurement of the cricoid lumen.

RESULTS

Twenty-two rabbits reached the endpoints, and 18 rabbits developed chronic SGS. ETT size significantly decreased by 0.5 from preinjury to the endpoint in all groups, P < .001. Control median cricoid lumen measurements were 20.48 mm² , the median cricoid lumen measurement for the 2 weeks endpoint was 14.3 mm² , 4 weeks 11.69 mm² , 6 weeks 16.03 mm² , and 8 weeks endpoint median was 16.33 mm² . Histopathological examination showed chronic scar tissue and new cartilage formation at the cricoid level, mainly at the posterior subglottic injury site starting from 4 weeks postinjury. Collagen staining revealed substantial amounts of organized collagen and different collagen orientation starting 4 weeks postinjury lasting until 8 weeks postinjury.

CONCLUSION

We developed an animal model to study chronic SGS. This model will be utilized to compare different endoscopic treatment interventions in acute SGS versus chronic SGS and further define the molecular basis of SGS.

LEVEL OF EVIDENCE

NA Laryngoscope, 2021.

Acute laryngeal lesions following endotracheal intubation: Risk factors, classification and treatment

Laryngeal stenosis is certainly one of the most severe complications of airway intubation in children, eventually leading to tracheostomy and sometimes to additional surgical procedures. Primary prophylaxis through modification of its risk factors and secondary prophylaxis through the management of post-extubation laryngeal acute lesions seem to be key to avoidance of this fearful complication. The present article addresses known risk factors for the development of laryngeal acute lesions with emphasis on sedation level and intubation time. It also discusses available classification systems proposed in medical literature, especially the Classification of Acute Laryngeal Injuries (CALI) conceived by our research group, and its positive predictive value for the development of chronic lesions. Finally, debate focuses on treatment of each individual lesion. Despite excellent results observed with endoscopic methods for treating these lesions, there is still doubts pending over their management, and there is need for further studies to define adequate treatment for each patient and for each type of lesion.

Application of Montgomery T-Tube Placement in Treating Cotton-Myer IV Subglottic Airway Atresia after Bi-Level Airway Recanalization

Objective

The purpose of this study is to explore the effectiveness and safety of Montgomery T-tube placement in treating Cotton-Myer IV subglottic airway atresia after bi-level airway recanalization.

Methods

This study is a retrospective study. 11 patients who were treated for IV subglottic airway atresia between January 2017 and January 2019 in the Second Affiliated Hospital of Jiaxing University were involved in this study. The 11 patients all had undergone tracheotomies at our hospital, and they were transferred to the Department of Pulmonary and Critical Care Medicine for Montgomery T-tube placement after bi-level airway recanalization when their subglottic airway was atretic. Patients were observed for their clinical manifestations after placement. The effectiveness of T-tube placement after bi-level airway recanalization was assessed. The incidence of short-term and long-term complications after surgery was assessed. Patients were followed up for 3 to 24 months for evaluating their airway recovery.

Results

T-tubes were successfully placed in 11 patients. The atretic airways of all patients were recanalized after treatment. Eight patients got restoration of vocal ability, and 3 patients could only say simple words. None of the patients needed assisted oxygen inhalation. The SpO2 average level was increased from 95 ± 2% before treatment to 97 ± 3% after treatment. Patients had significant relief of cough or sputum, and they had less difficulty in dyspnea. All short- or long-term complications were self-relieved or controlled without further malignant progression after treatment by doctors. The average postoperative extubating time was (14.86 ± 3.62) months.

Conclusion

The application of Montgomery T-tube placement in treating Cotton-Myer IV subglottic airway atresia after bi-level airway recanalization is well effective and safe for patients, and it can be promoted in clinical treatment.

Rat Model of External Auditory Canal Stenosis

HYPOTHESIS

Circumferential electrocautery injury of the rat external auditory canal (EAC) can induce a reproducible animal model of acquired stenosis.

BACKGROUND

Acquired EAC stenosis may occur as a result of chronic inflammation or trauma to the EAC skin and is characterized by narrowing of the EAC, retention of debris, and hearing loss. Treatment is surgery but it is often complicated by restenosis. A reliable and inexpensive animal model of EAC stenosis has not been described. There have been no studies correlating the extent of EAC injury with the extent of stenosis.

METHODS

Rats received a 25, 50, or 75% circumferential EAC injury with electrocautery. The extent of resulting stenosis was quantified 21 days following injury. The nature of the injury and healing response was assessed with histology.

RESULTS

A 25% circumferential injury led to 4 to 34% stenosis (mean, 13%), 50% injury resulted in 43 to 100% stenosis (mean, 73%), and 75% injury resulted in 94 to 100% stenosis (mean=99%, p < 0.0001). The 50% circumferential injury produced 30 to 75% stenosis in five of eight ears, the remainder had >75% stenosis. Wounded ears showed evidence of intact cartilage and epithelium, with increased thickness of the subepithelial layer and localized fibrosis.

CONCLUSIONS

Electrocautery injury in the ventral aspect of the rat EAC resulted in reproducible EAC stenosis. This rat model may be useful in studying therapy to prevent acquired EAC stenosis due to acute injury. The correlation of the extent of injury (circumference) with resulting stenosis may inform clinical management of EAC injuries.

Rabbit model of consistently survivable subglottic stenosis using a modified brush technique

INTRODUCTION

Several animal models of subglottic stenosis (SGS) have been described in the literature, however many result in severe stenosis that requires early intervention and carry a high mortality rate. This limits the application of the model and may require the use of additional animals to achieve desired results due to procedural complications. A novel endoscopic method of inducing SGS in a rabbit model was developed as part of a larger investigation on the treatment of this condition. The objective of this study was to develop an animal model for survivable subglottic stenosis.

METHODS

12 New Zealand white rabbits underwent 2 trials of prolonged intubation that were not successful in inducing SGS. A partially sheathed nylon brush injury technique was then designed and implemented. Airway assessment consisted of rigid bronchoscopy 6 weeks and 8 months after injury.

RESULTS

12 rabbits undergoing subglottic brush injury had focal posteriorly based subglottic stenosis on bronchoscopy at 6 weeks and 8 months post-injury. One rabbit was euthanized after the brush induced subglottic injury but prior to 6 week bronchoscopy due to an unrelated orthopedic injury. This animal was therefore excluded from analysis and replaced. No rabbits required early airway intervention or sacrifice. All survived a period of 8 months.

CONCLUSION

Inducing subglottic injury with a partially-sheathed nylon brush safely and reliably creates a controlled SGS with zero procedure-related mortality over 8 months. This model could be the basis for a longer-term evaluation of subglottic scar evolution and intervention.

Subglottic Stenosis: Development of a Clinically Relevant Endoscopic Animal Model

OBJECTIVE

Develop a clinically relevant and reproducible endoscopic animal model for subglottic stenosis amenable to testing of minimally invasive therapeutic modalities.

STUDY DESIGN

Cohort study.

SETTING

Division of Laboratory Animals Research, University of Pittsburgh.

SUBJECTS AND METHODS

Subglottic stenosis was induced endoscopically via microsuspension laryngoscopy in 26 New Zealand white rabbits. A trimmed polypropylene brush connected to a novel electronic stenosis induction apparatus was used to create circumferential trauma to the subglottis. By using open source image analysis software, the cross-sectional areas of the stenotic and native airways were compared to calculate the percentage of stenosis and the Myer-Cotton classification grade.

RESULTS

Of the 26 rabbits, 24 (92%) exhibited stenosis after the first attempt. The mean percentage of airway stenosis was 57% (range, 34%-85%; SD, 15%). Five rabbits (19.2%) died on the day of stenosis induction from procedural complications. Of the 21 rabbits, 2 demonstrated no stenosis 7 days after initial injury and so underwent reinduction of airway injury, upon which they developed stenosis. Overall, 14 of the 21 rabbits (67%) exhibited moderate to severe stenosis (grade 2 or 3).

CONCLUSION

The stenosis induction apparatus reliably induced stenosis with a low mortality rate as compared with that of other methods in the literature. The device could be improved to generate a predetermined potentially reproducible grade of stenosis as desired by the operator. This method sets the stage for a clinically relevant and reproducible subglottic stenosis disease model that is amenable to testing of minimally invasive treatment modalities.