Update on airway stents

Study onin vivoandin vitrodegradation of polydioxanone weaving tracheal stents

The appropriate degradation characteristics of polydioxanone (PDO) are necessary for the safety and effectiveness of stents. This study aimed to investigate the degradation of PDO weaving tracheal stents (PW stents)in vitroandin vivo. The degradation solution ofS. aureus(SAU),E. coli(ECO),P. aeruginosa(PAE), and control (N) were prepared, and the PW stents were immersed for 12 weeks. Then, the radial support force, weight retention, pH, molecular structure, thermal performance, and morphology were determined. Furthermore, the PW stents were implanted into the abdominal cavity of rabbits, and omentum was embedded. At feeding for 16 weeks, the mechanical properties, and morphology were measured. During the first 8 weeks, the radial support force in all groups was progressively decreased. At week 2, the decline rate of radial support force in the experimental groups was significantly faster compared to the N group, and the difference was narrowed thereafter. The infrared spectrum showed that during the whole degradation process, SAU, ECO and PAE solution did not lead to the formation of new functional groups in PW stents.In vitroscanning electron microscope observation showed that SAU and ECO were more likely to gather and multiply at the weaving points of the PW stents, forming colonies.In vivoexperiments showed that the degradation in the concavity of weaving points of PW stents was more rapid and severe. The radial support loss rate reached more than 70% at week 4, and the radial support force was no longer measurable after week 8. In omentum, multinuclear giant cells and foreign giant cells were found to infiltrate. PW stents have good biocompatibility. The degradation rate of PW stents in the aseptic conditionsin vivowas faster than in the bacteriological environmentin vitro.

Tracheobronchial stents: an expanding prospect

The first dedicated tracheobronchial silicone stent was designed by the French pulmonologist Jean-Paul Dumon. The most common indications for stenting are to minimise extrinsic airway compression from mass effect, maintain airway patency due to intrinsic obstruction or treat significant nonmalignant airway narrowing or fistulae. Silicone stents require rigid bronchoscopy for insertion; however, they are more readily repositioned and removed compared with metallic stents. Metallic stents demonstrate luminal narrowing when loads are applied to their ends, therefore stents should either be reinforced at the ends or exceed the area of stenosis by a minimum of 5 mm. Nitinol, a nickel-titanium metal alloy, is currently the preferred material used for airway stents. Airway stenting provides effective palliation for patients with severe symptomatic obstruction. Drug-eluting and three-dimensional printing of airway stents present promising solutions to the challenges of the physical and anatomical constraints of the tracheobronchial tree. Biodegradable stents could also be a solution for the treatment of nonmalignant airway obstruction.

Treatment of aerodigestive fistulas with a novel covered metallic Y-shaped segmented airway stent customized with the assistance of 3D printing

Background

The management of aerodigestive fistula remains challenging. An airway stent that matches well with the individual geometry of the airway is needed for the treatment of the aerodigestive fistula. This study aimed to evaluate the feasibility of a novel covered metallic segmented Y-shaped airway stent customized with the assistance of 3D printing in aerodigestive fistulas involving the carina and distal bronchi and to compare the flexibility of the novel stent with the conventional wholly knitted stent.

Methods

In the flexibility study, we measured the longitudinal bending force and spring-back force of the segmented stent and wholly knitted stent. Patient-specific stents that were individually customized with the assistance of 3D printing technology were implanted in 26 patients with aerodigestive fistulas. The technical success, clinical success, Karnofsky performance status (KPS), and stent-related complications were recorded.

Results

The bending force and spring-back force of the segmented stent were significantly lower than those of the wholly knitted stent. Stent deployment was technically successful in all patients. Clinical success was obtained in 21 patients. The KPS of patients after the stenting procedure improved significantly compared with that before stenting (P<0.001). During follow-up, granulation tissue proliferation, sputum retention, stent migration, and intolerance of the stent were found in 2, 5, 1, and 1 patient, respectively.

Conclusions

The segmented metallic Y-shaped airway stent had greater flexibility than the wholly knitted stent in an ex vivo setting. Implantation of the segmented stent individually customized with the aid of 3D printing is feasible in treating aerodigestive fistulas involving the carina and bronchi distal to the carina.

Drug delivery to the pediatric upper airway

Pediatric upper airway disorders are frequently life-threatening and require precise assessment and intervention. Targeting these pathologies remains a challenge for clinicians due to the high complexity of pediatric upper airway anatomy and numerous potential etiologies; the most common treatments include systemic delivery of high dose steroids and antibiotics or complex and invasive surgeries. Furthermore, the majority of innovative airway management technologies are only designed and tested for adults, limiting their widespread implementation in the pediatric population. Here, we provide a comprehensive review of the most recent challenges of managing common pediatric upper airway disorders, describe the limitations of current clinical treatments, and elaborate on how to circumvent those limitations via local controlled drug delivery. Furthermore, we propose future advancements in the field of drug-eluting technologies to improve pediatric upper airway management outcomes.

The role of 3D printing in pediatric airway obstruction: A systematic review

BACKGROUND

Tracheomalacia and tracheal stenosis are complicated, patient-specific diseases that require a multidisciplinary approach to diagnose and treat. Surgical interventions such as aortopexy, slide tracheoplasty, and stents potentially have high rates of morbidity. Given the emergence of three-dimensional (3D) printing as a versatile adjunct in managing complex pathology, there is a growing body of evidence that there is a strong role for 3D printing in both surgical planning and implant creation for pediatric airway obstruction.

METHODS

A structured PubMed.gov literature search was utilized, and a two-researcher systematic review was performed following the PRISMA criteria. The following search query was utilized: (((((3D printing) OR three-dimensional printing) OR 3D printed) OR three-dimensional printed) AND trachea) OR airway.

RESULTS

Over 23,000 publications were screened. Eight literature reviews and thirty-seven original papers met inclusion criteria. Of the thirty-seven original papers, eleven discussed 3D printing for surgical planning and twenty-six discussed 3D printing implants for interventions.

CONCLUSION

The reported application of 3D printing for management of pediatric airway obstruction is emerging with positive and broad applications. 3D printing for surgical planning not only improves pre-operative assessment of surgical approach and stent customization, but also helps facilitate patient/family education. 3D printing for custom implantable interventions is focused on bioresorbable external airway splints and biological grafts, with both animal studies and human case reports showing good results in improving symptoms.

Reactivity Study of a Biodegradable Polydioxanone Tracheal Stent in a Rabbit Model

INTRODUCTION

The objective of this study was to evaluate tracheal reactivity induced by a biodegradable polydioxanone tracheal stent.

MATERIALS AND METHODS

Twenty-two rabbits were divided into 3 groups assigned to different survival times (30, 60 and 90days post-implantation). A biodegradable stent was implanted in each animal, except for 1 of each group (negative control). Implantation was performed through a small tracheotomy under fluoroscopic control. CT and histopathological studies were scheduled at the end of survival times.

RESULTS

No animal died during the procedure or follow-up. The stent had disappeared in 100% of the cases at 90days, in 50% at 60days, and in none at 30days. CT studies revealed a greater tracheal wall thickness at 30days than at 60 and 90days (1.60±0.41mm in the central part of the stent versus 1.11±0.18 and 0.94±0.11; P=.007, respectively). No granulomas were observed on histopathology. Some degree of histological changes were noted at 30days, which had reduced at 60 and 90days. Differences were also found in both CT and histology between animals in which the stent was present and animals in which it had degraded.

CONCLUSIONS

Polydioxanone stents produce a mild reaction that reverts with tracheal degradation. The use of these biodegradable stents in benign tracheal disease is promising.

Retrievable covered metallic segmented Y airway stent for gastrorespiratory fistula of carina or main bronchi

OBJECTIVE

To evaluate the feasibility of new retrievable covered metallic segmented Y airway stents modified with 3-dimensional (3D) printing for gastrorespiratory fistula involving carina or main bronchi.

METHODS

We designed a new retrievable covered metallic segmented Y airway stent to fit the anatomical characteristics of the carina region in individual patients. All stents were individually customized based on a 3D-printed mold. Six patients with gastrorespiratory fistula and aspiration pneumonia after esophagectomy underwent the stent implantation. The stents were retrieved when the fistula was cured or stent-related complications occurred.

RESULTS

Seven Y stents were successfully implanted and removed in 6 patients. All stents expanded well, and the fistulas were completely sealed. Aspiration pneumonia was controlled in 6 patients. The median Karnofsky Performance Status scores significantly improved after stenting compared with those before stent implantation (P = .024). Sputum retention was the most common complication after stenting and was treated with aspiration under bronchoscopy (33.33%). Excessive granulation tissue proliferation was found in 1 patient (16.7%) and was treated with cryotherapy. The indwelling time of the stent was 64 days (interquartile range, 52-69 days). After stent removal, bronchoscopy, gastroscopy, and computed tomography of the chest showed cured fistulas in all patients, and no stents showed fractures.

CONCLUSIONS

Retrievable covered metallic segmented Y airway stents modified with 3D printing appear to be feasible for the treatment of gastrorespiratory fistula involving carina or main bronchi.

Airway stenting: Technological advancements and its role in interventional pulmonology

AS offers rapid and sustained relief of symptoms in most patients treated for malignant or benign CAO and can also be curative in itself in cases of benign tracheobronchial stenosis. In the past 30 years, this field has seen significant progress, from the misuse of vascular non-covered metallic stents to the development of silicone airway stents with an increasingly large panel of shapes and of hybrid, partially or fully covered, SEMS customized to the airways. This study aims to offer an overview on: (i) the respective advantages and drawbacks of these two main categories of devices; (ii) the main indications for AS and the rationale behind the choice of stent in each situation; and (iii) the main promises borne from the progress made in the field in the past few years, including the development of drug-eluting, biodegradable or patient-specific customized AS.

Lung Cancer

Lung cancer is the world's leading cause of cancer death. Screening for lung cancer by low-dose computed tomography improves mortality. Various modalities exist for diagnosis and staging. Treatment is determined by subtype and stage of cancer; there are several personalized therapies that did not exist just a few years ago. Caring for the patient with lung cancer is a complex task. This review provides a broad outline of this disease, helping clinicians identify such patients and familiarizing them with lung cancer care options, so they are better equipped to guide their patients along this challenging journey.

3D printing for airway disease

It has been 30 years since the first commercial three-dimensional (3D) printer was available on market. The technological advancement of 3D printing has far exceeded its implementation in medicine. The application of 3D printing technology has the potential of playing a major role within interventional pulmonology; specifically, in the management of complex airway disease. Tailoring management to the patient-specific anatomical malformation caused by benign or malignant disease is a major challenge faced by interventional pulmonologists. Such cases often require adjunctive therapeutic procedures with thermal therapies followed by dilation and airway stenting to maintain the patency of the airway. Airway-stent size matching is one key to reducing stent-related complications. A major barrier to matching is the expansion of the stent in two dimensions (fixed sizes in length and diameter) within the deformed airway. Additional challenges are created by the subjective oversizing of the stent to reduce the likelihood of migration. Improper sizing adversely affects the stability of the stent. The stent-airway mismatch can be complicated by airway erosion, perforation, or the formation of granulation tissue. Stents can migrate, fracture, obstruct, or become infected. The use of patient-specific 3D printed airway stents may be able to reduce the stent airway mismatch. These stents allow more precise stent-airway sizing and minimizes high-pressure points on distorted airway anatomy. In theory, this should reduce the incidence of the well-known complications of factory manufactured stents. In this article, the authors present the brief history of 3D printed stents, their consideration in select patients, processing steps for development, and future direction.