The use of self-expandable metallic stents in the airways in the adult population

Forbearance with endobronchial stenting: cognisance before conviction

Endobronchial stenting is an important aspect of the practice of interventional pulmonology. The most common indication for stenting is the management of clinically significant airway stenosis. The list of endobronchial stents available on the market continues to grow. More recently, patient-specific 3D-printed airway stents have been approved for use. Airway stenting should be considered only when all other options have been exhausted. Due to the environment of the airways and the stent-airway wall interactions, stent-related complications are common. Although stents can be placed in various clinical scenarios, they should only be placed in scenarios with proven clinical benefit. The unwarranted placement of a stent can expose the patient to complications with little or no clinical benefit. This article reviews and outlines the key principles of endobronchial stenting and important clinical scenarios in which stenting should be avoided.

Bifurcated Silicone Stents for the Management of Anastomotic Complications in Lung Transplanted Patients: Ten Years’ Experience

<b><i>Background:</i></b> In lung transplantation (LT), the actual surgical practice is to cut the donor bronchus as short as possible in order to reduce anastomotic complications (AC). Consequently, the anastomosis is very close to the secondary carina. If AC occur, regular straight stents may be unsatisfactory and on-site modified bifurcated stents may represent an alternative. <b><i>Objectives:</i></b> This retrospective study sought to assess the short- and long-term outcomes of patients treated with customized bifurcated stent (CBS) for the management of AC following LT. <b><i>Methods:</i></b> Data from patients with AC following LT requiring CBS placement between June 2010 and June 2020 were analyzed. <b><i>Results:</i></b> Four hundred patients underwent lung transplant. AC requiring airway stenting occurred in 32 patients (8%), and CBS were inserted in 15 patients (3.5%). Indications were stenosis (<i>n</i> = 12; 80%) and bronchial dehiscence (<i>n</i> = 3; 20%). CBS were successfully deployed in 14 patients and failed in 1 patient. No migration was recorded during the follow-up. The median number of complication was 1 per patient (0–5). CBS could be removed in 11 patients (78.6%), and 3 died with their stents in place. AC recurrence or complications requiring new stenting occurred in 4/11 patients (36.3%), with a median time of 7 days (0–29). Seven patients (63.7%) had no AC recurrence, with a median follow-up of 925 days (118–3,249). <b><i>Conclusions:</i></b> The actual surgical anastomotic technique in LT provides new endoscopic challenges. CBS seem ideally positioned to address these difficulties safely and effectively but are associated with stent related complications requiring further endoscopic management.

Dilation versus laser resection in subglottic stenosis: protocol for a prospective international multicentre randomised controlled trial (AERATE trial)

INTRODUCTION

Subglottic stenosis (SGS) is a rare condition that results from progressive narrowing of the upper airways. Outcomes and treatment options depend on the benign or complex nature of the stenosis. Treatment options for SGS include surgery and endoscopic techniques. The main endoscopic techniques used are dilation and laser resection. Observational and retrospective studies suggest that endoscopic laser resection may be more effective than dilation. We, therefore, aimed to compare the effectiveness of dilation and laser resection in preventing recurrence of SGS.

METHODS AND ANALYSIS

AERATE (dilAtion vs laser Endoscopic Resection in subglottic trAcheal sTEnosis) is a multicentre, investigator-initiated, randomised controlled trial, comparing endoscopic dilation to endoscopic laser resection for simple benign SGS (less than 1 cm long without underlying cartilaginous damage) referred for endoscopic treatment (first treatment or recurrence). The study will be conducted in three centres in France and one in Canada with other centres from France and Canada expected to join. The primary outcome is the recurrence rate of stenosis at 2 years. Recurrence is defined as having a new onset of symptoms along with a stenosis of more than 40% (confirmed by bronchoscopy) requiring a new procedure. A sample size of 100 patients is calculated for the primary endpoint assuming a 10% recurrence rate in the laser resection group and 33% in the dilation group with a statistical significance level of 5%, a power of 80%.

ETHICS AND DISSEMINATION

This study is approved by local and national ethics committees as required. Results will be published, and trial data will be made available.

TRIAL REGISTRATION NUMBER

NCT04719845.

Clinical Outcomes of Complications Following Self-Expandable Metallic Stent Insertion for Benign Tracheobronchial Stenosis

Background and Objectives: The use of metallic stents in benign TBS is controversial. Here, we report the clinical outcomes of patients who developed complications due to self-expandable metallic stent (SEMS) insertion for benign TBS. Materials and Methods: Our institution, which is the largest and most active referral hospital for airway stenosis in South Korea, only uses silicone stents. We conducted a retrospective review of 20 patients referred after the insertion of SEMS for benign TBS from 2006 to 2015. Results: All 20 patients underwent rigid bronchoscopy for SEMS removal due to airway obstruction from granulation tissue overgrowth. All but one (95%) experienced successful removal of the SEMS. During a median follow-up period of 40 months, a median of seven rigid bronchoscopies per patient was needed to maintain airway patency. Three (15%) patients suffered acute complications during SEMS removal (bleeding (10%) and fistula (5%)). All patients suffered chronic complications (granulation tissue (80%), stent migration (58%), mucostasis (55%), and restenosis (43%)). Eventually, 15 patients (75%) needed airway prostheses (silicone stent (75%) and tracheostomy (25%)). Conclusion: Our findings indicate that SEMS should be avoided until positive results are consistently reported by high-quality studies in patients with benign TBS.

Silicone Stent Versus Fully Covered Metallic Stent in Malignant Central Airway Stenosis

BACKGROUND

Airway stenting to restore airway patency in cases of malignant central airway obstruction is an effective palliation treatment. Our goal was to compare the efficacy after deployment and complications of a fully covered self-expandable metal stent (SEMS) (Aerstent) and a silicone stent (Dumon).

METHODS

This was a retrospective cohort of 2 similar groups of patients with malignant central airway obstruction treated with stents between August 2012 and July 2017. Complications were assessed bronchoscopically. A competing risk for death analysis was performed to adjust the probability of developing a complication.

RESULTS

Seventy patients (29 with silicone stents and 41 with SEMS) were included. Stent insertion was successful in all cases. Mucus retention was the most frequent complication (75.9% with silicone stents and 84.8% with SEMS; P = .51), followed by granulation tissue (51.7% with silicone stents and 41.3% with SEMS; P = .52) and migration (6.9% with silicone stents and 13.0% with SEMS; P = .47). In the first month, the cumulative incidence of a complication was 36.7% for silicone stents and 41.3% for SEMS and increased to 90.0% and 97.8% after 6 months, respectively (hazard ratio = 1.66; P = .04). A competing risk for death analysis showed an adjusted hazard ratio of 1.41 (P = .49) indicating no differences in overall complications between stents.

CONCLUSIONS

Both stents were equally successful and safe. The incidence of complications increased over time to 90% at 6 months for both stents. The risk of overall complications was higher for SEMS; nevertheless, when mortality was measured in a competitive risk analysis, no differences were found between SEMS and silicone stents.

Clinical Comparison of Airway Stent Placement in Intervention Room and Operating Room

BACKGROUND

Airway stent placement is the effective regimen for central airway obstruction (CAO), while its application scenarios varied. This study aimed to make clinical comparison of airway stent placement in the intervention room and operating room.

METHODS

Patients underwent airway stent placement between 2014 and 2018 were included in this retrospective case-control study. Clinical performance of airway stent placement in intervention room and operating room were compared.

RESULTS

82 patients were included in this study, including 39 in the intervention room and 43 in the operating room. Patients treated in the intervention room had lower Charlson comorbidity index (CCI) (P=0.018) and received less Y-shaped stents (P<0.001). Better clinical response (P=0.026), more stents placed (P<0.001) and longer length of stent (P<0.001) were observed in operating room, while there was no significantly statistical difference of stent-related complications and post-stent survival rate between the two groups. Extracorporeal membrane oxygenation (ECMO) supported airway stent placement procedures were performed in the operating room, which provided definitive safety support for high-risk intervention.

CONCLUSIONS

Patients with CAO could benefit from the operating room scenario, and airway stent placement in the operating room is more suitable for patients with higher CCI scores and receiving more complicated procedures.

Self-expanding metallic Y-stent compared to silicone Y-stent for malignant lesions of the main carina: A single center retrospective study

BACKGROUND

Bifurcation stents are often required in patients with malignant airway obstruction or fistulization involving the main carina. The silicone Y stent is the most used but remains challenging to place. The self-expanding metallic Y (SEM) stent appears easy to use. The objective is to report the feasibility, efficacy, and tolerance of SEM Y stent compared to silicone Y stent in patients with malignant tumors involving the main carina.

PATIENTS AND METHODS

This retrospective single center study was performed between May 2004 and May 2017. All patients with malignant carina involvement treated with a bronchial Y stent were included.

RESULTS

Forty silicone Y stents and 38 SEM Y stents were placed. Seven stenting placements failed in the silicone Y group but none in the SEM Y stent group (P=0.008). The median duration of the procedure was 80min (25-210) in the silicone Y group and.50min (25-110min) in the SEM Y group (P=0.001). There was no significant difference in terms of early or late complications between the 2 groups. Nine silicone Y stents (26.5%) and 7 SEM Y stents (18.4%) were removed (P=0.4). The median survival time following stent insertion was 171 days (Interquartile range (IQR): 53-379) in the silicone Y group and 104 days (IQR: 53-230) in the SEM Y group.

CONCLUSION

If silicone Y stent remains the best solution for benign obstruction, SEM Y stent seems to be an easy alternative with no difference in terms of complication or ablation for malignant lesions involving the main carina.

Stents for airway strictures: selection and results

Airway stents can provide effective and timely relief in patients with central airway obstruction. Silicone based stents are the most commonly used airway stents worldwide with a long track record of safety. Metallic stents continue to evolve from the earliest uncovered versions to a variety of newly designed covered stents. Despite the availability of a variety of stent materials and designs, minimal advances have been made towards innovation in stent technology and an ideal stent has unfortunately not yet been developed. Nevertheless, the first generation of biodegradable airway stents are available, work on drug-eluted stents is in the pipeline and three-dimensional printing of a customized airway stent may be the future. In this review, we discuss selection and results for most commonly utilized airway stents.

A new removable airway stent

Background

Malignant airway obstruction is a feared complication and will most probably occur more frequently in the future because of increasing cancer incidence and increased life expectancy in cancer patients. Minimal invasive treatment using airway stents represents a meaningful and life-saving palliation. We present a new removable airway stent for improved individualised treatment.

Methods

To our knowledge, the new airway stent is the world's first knitted and uncovered self-expanding metal stent, which can unravel and be completely removed. In an in vivo model using two anaesthetised and spontaneously breathing pigs, we deployed and subsequently removed the stents by unravelling the device. The procedures were executed by flexible bronchoscopy in an acute and a chronic setting – a ‘proof-of-principle’ study.

Results

The new stent was easily and accurately deployed in the central airways, and it remained fixed in its original position. It was easy to unravel and completely remove from the airways without clinically significant complications. During the presence of the stent in the chronic study, granulation tissue was induced. This tissue disappeared spontaneously with the removal.

Conclusions

The new removable stent functioned according to its purpose and unravelled easily, and it was completely removed without significant technical or medical complications. Induced granulation tissue disappeared spontaneously. Further studies on animals and humans are needed to define its optimal indications and future use.

Flexible Endoscopic Spray Application of Respiratory Epithelial Cells as Platform Technology to Apply Cells in Tubular Organs

Introduction: Inoperable airway stenoses are currently treated by placing stents. A major problem of covered stents is missing mucociliary clearance, which is caused by covering the native respiratory epithelium. By coating a stent with respiratory epithelium, this problem can be overcome. However, no methods are available for efficient endoscopic cell seeding.

Methods: We designed a flexible endoscopic spraying device based on a bronchoscope and tested it with respiratory epithelial cells. With this device cells can also be applied in a thin layer of fibrin glue. We evaluated the survival rate directly after spray application with a live-dead staining and the long-term differentiation capacity with histology and electron microscopy. Furthermore, the random distribution of cells when applied in a tube was analyzed and the macroscopic and microscopic characteristics of the endoscopic spray were investigated using high-speed visualization.

Results: Spray visualization revealed a polydisperse character of the spray with the majority of droplets larger than epithelial cells. Spray application does not influence the survival rate and differentiation of respiratory epithelial cells. After 4 weeks, cells built up a pseudostratified epithelial layer with cilia and goblet cells. When cells are applied in a thin layer of fibrin gel into a tube, a nearest neighbor index of 1.2 is obtained, which suggests a random distribution of the cells.

Conclusions: This spraying device is a promising tool for application of various cell types onto stents or implants with high survival rates and homogeneous distribution as shown in this study for ovine respiratory epithelial cells. The system could also be used for cell therapy to locally apply cells to the diseased parts of hollow organs. For the first time, the fluid dynamics of a spray device for cells were examined to validate in vitro results.

Bronchoscopic palliation to treat endobronchial metastasis of the tracheobronchial tree

BACKGROUND

Endobronchial metastases (EBM) are rarely observed, but they are caused by a number of different tumors. Bronchoscopy is the main approach for both differential diagnosis and to maintain endoluminal palliation. In this study, consecutive EBM cases that had been diagnosed and treated were evaluated in a retrospective cohort.

METHODS

In total, 18 pathologically verified patients with EBM originating from extrathoracic tumors who were referred to our interventional pulmonology unit with respiratory symptoms were retrospectively evaluated. Tumor type, metastasis location, treatment method and frequency, and complications were evaluated.

RESULTS

In total, there were 18 patients (13 women) with EBM enrolled in this study. All were diagnosed by a bronchial biopsy. The mean age of the patients was 48±15.24 years (range: 24-76 years). The most frequent sites of origin of the metastases were the bone (5) and kidney. Obstructions were observed in the tracheas of 12 patients, in the right main bronchi of 10, and in the left main bronchi of 11. Twelve airway stents were placed in nine patients. The removal of the obstruction was effective in the remaining patients. The mean number of treatment applications was 1.47 (range: 1-3). Hemorrhage, mucostasis, and granulation were observed. The median follow-up duration was 528 days (range: 62-1177 days). The median survival time for the patients who died was 122 days (range: 2-885 days).

CONCLUSIONS

EBM is rare, and bronchoscopy is the primary method of diagnosis, followed by palliation, if necessary.

Biodegradable Airway Stents - Bench to Bedside: A Comprehensive Review

Airway stents are indicated to treat symptomatic narrowing or to close fistulas of the central airways. They are generally divided into two types: the silicone stents and the metallic stents. Unlike in malignancies, removability is a major objective of temporary stenting in benign conditions, which poses the challenge of a new rigid bronchoscopic procedure under general anesthesia and stent removal with all its attendant risks and costs. The concept of a biodegradable (BD) stent that could maintain the patency of an airway for a predetermined duration of time is very appealing. These BD stents would gradually degrade and eventually vanish from the airway once they are no longer needed. Such stents are currently an area of intense research. Another very promising concept of drug delivery with such stents is also a very exciting area of current research. The aim of this comprehensive review is to discuss all pertinent available literature on the use of BD materials in various clinical applications and to extensively review all animal and humans trials involving BD airway stents.

Serious Complications after Self-expandable Metallic Stent Insertion in a Patient with Malignant Lymphoma

An 18-year-old woman was evaluated for a chronic productive cough and dyspnea. She was subsequently diagnosed with mediastinal non-Hodgkin lymphoma (NHL). A covered self-expandable metallic stent (SEMS) was implanted to relieve narrowing in for both main bronchi. The NHL went into complete remission after six chemotherapy cycles, but atelectasis developed in the left lower lobe 18 months after SEMS insertion. The left main bronchus was completely occluded by granulation tissue. However, the right main bronchus and intermedius bronchus were patent. Granulation tissue was observed adjacent to the SEMS. The granulation tissue and the SEMS were excised, and a silicone stent was successfully implanted using a rigid bronchoscope. SEMS is advantageous owing to its easy implantation, but there are considerable potential complications such as severe reactive granulation, stent rupture, and ventilation failure in serious cases. Therefore, SEMS should be avoided whenever possible in patients with benign airway disease. This case highlights that SEMS implantation should be avoided even in malignant airway obstruction cases if the underlying malignancy is curable.