A new airway spiral stent designed to maintain airway architecture with an atraumatic removal after full epithelization-Research of feasibility and viability in canine patients with tracheomalacia

Enhancing Robustness of Adhesive Hydrogels through PEG-NHS Incorporation

Tissue wounds are a significant challenge for the healthcare system, affecting millions globally. Current methods like suturing and stapling have limitations as they inadequately cover the wound, fail to prevent fluid leakage, and increase the risk of infection. Effective solutions for diverse wound conditions are still lacking. Adhesive hydrogels, on the other hand, can be a potential alternative for wound care. They offer benefits such as firm sealing without leakage, easy and rapid application, and the provision of mechanical support and flexibility. However, the in vivo durability of hydrogels is often compromised by excessive swelling and unforeseen degradation, which limits their widespread use. In this study, we addressed the durability issues of the adhesive hydrogels by incorporating acrylamide polyethylene glycol N-hydroxysuccinimide (PEG-NHS) moieties (max. 2 wt %) into hydrogels based on hydroxy ethyl acrylamide (HEAam). The results showed that the addition of PEG-NHS significantly enhanced the adhesion performance, achieving up to 2-fold improvement on various soft tissues including skin, trachea, heart, lung, liver, and kidney. We further observed that the addition of PEG-NHS into the adhesive hydrogel network improved their intrinsic mechanical properties. The tensile modulus of these hydrogels increased up to 5-fold, while the swelling ratio decreased up to 2-fold in various media. These hydrogels also exhibited improved durability under the enzymatic and oxidative biodegradation induced conditions without causing any toxicity to the cells. To evaluate its potential for clinical applications, we used PEG-NHS based hydrogels to address tracheomalacia, a condition characterized by inadequate mechanical support of the airway due to weak/malacic cartilage rings. Ex vivo study confirmed that the addition of PEG-NHS to the hydrogel network prevented approximately 90% of airway collapse compared to the case without PEG-NHS. Overall, this study offers a promising approach to enhance the durability of adhesive hydrogels by the addition of PEG-NHS, thereby improving their overall performances for various biomedical applications.

Antimicrobial and Antiproliferative Coatings for Stents in Veterinary Medicine-State of the Art and Perspectives

Microbial colonization in veterinary stents poses a significant and concerning issue in veterinary medicine. Over time, these pathogens, particularly bacteria, can colonize the stent surfaces, leading to various complications. Two weeks following the stent insertion procedure, the colonization becomes observable, with the aggressiveness of bacterial growth directly correlating with the duration of stent placement. Such microbial colonization can result in infections and inflammations, compromising the stent's efficacy and, subsequently, the animal patient's overall well-being. Managing and mitigating the impact of these pathogens on veterinary stents is a crucial challenge that veterinarians and researchers are actively addressing to ensure the successful treatment and recovery of their animal patients. In addition, irritation of the tissue in the form of an inserted stent can lead to overgrowth of granulation tissue, leading to the closure of the stent lumen, as is most often the case in the trachea. Such serious complications after stent placement require improvements in the procedures used to date. In this review, antibacterial or antibiofilm strategies for several stents used in veterinary medicine have been discussed based on the current literature and the perspectives have been drawn. Various coating strategies such as coating with hydrogel, antibiotic, or other antimicrobial agents have been reviewed.

A novel ex vivo tracheobronchomalacia model for airway stent testing and in vivo model refinement

OBJECTIVES

We sought to develop an ex vivo trachea model capable of producing mild, moderate, and severe tracheobronchomalacia for optimizing airway stent design. We also aimed to determine the amount of cartilage resection required for achieving different tracheobronchomalacia grades that can be used in animal models.

METHODS

We developed an ex vivo trachea test system that enabled video-based measurement of internal cross-sectional area as intratracheal pressure was cyclically varied for peak negative pressures of 20 to 80 cm H2O. Fresh ovine tracheas were induced with tracheobronchomalacia by single mid-anterior incision (n = 4), mid-anterior circumferential cartilage resection of 25% (n = 4), and 50% per cartilage ring (n = 4) along an approximately 3-cm length. Intact tracheas (n = 4) were used as control. All experimental tracheas were mounted and experimentally evaluated. In addition, helical stents of 2 different pitches (6 mm and 12 mm) and wire diameters (0.52 mm and 0.6 mm) were tested in tracheas with 25% (n = 3) and 50% (n = 3) circumferentially resected cartilage rings. The percentage collapse in tracheal cross-sectional area was calculated from the recorded video contours for each experiment.

RESULTS

Ex vivo tracheas compromised by single incision and 25% and 50% circumferential cartilage resection produce tracheal collapse corresponding to clinical grades of mild, moderate, and severe tracheobronchomalacia, respectively. A single anterior cartilage incision produces saber-sheath type tracheobronchomalacia, whereas 25% and 50% circumferential cartilage resection produce circumferential tracheobronchomalacia. Stent testing enabled the selection of stent design parameters such that airway collapse associated with moderate and severe tracheobronchomalacia could be reduced to conform to, but not exceed, that of intact tracheas (12-mm pitch, 0.6-mm wire diameter).

CONCLUSIONS

The ex vivo trachea model is a robust platform that enables systematic study and treatment of different grades and morphologies of airway collapse and tracheobronchomalacia. It is a novel tool for optimization of stent design before advancing to in vivo animal models.

Wet adhesive hydrogels to correct malacic trachea (tracheomalacia) A proof of concept

Tracheomalacia (TM) is a condition characterized by a weak tracheal cartilage and/or muscle, resulting in excessive collapse of the airway in the newborns. Current treatments including tracheal reconstruction, tracheoplasty, endo- and extra-luminal stents have limitations. To address these limitations, this work proposes a new strategy by wrapping an adhesive hydrogel patch around a malacic trachea. Through a numerical model, first it was demonstrated that a hydrogel patch with sufficient mechanical and adhesion strength can preserve the trachea's physiological shape. Accordingly, a new hydrogel providing robust adhesion on wet tracheal surfaces was synthesized employing the hydroxyethyl acrylamide (HEAam) and polyethylene glycol methacrylate (PEGDMA) as main polymer network and crosslinker, respectively. Ex vivo experiments revealed that the adhesive hydrogel patches can restrain the collapsing of malacic trachea under negative pressure. This study may open the possibility of using an adhesive hydrogel as a new approach in the difficult clinical situation of tracheomalacia.

Stents in Veterinary Medicine

Stenting in veterinary medicine has been a rapidly growing method of interventional surgery for several years. This procedure is usually performed in the respiratory and urinary tracts, but there are cases of stenting of blood vessels or gastrointestinal structures. It is based on maintaining the permeability of a given tubular structure, thus allowing the passage of gas or liquid. This procedure is often performed as a first-line treatment in situations where pharmacological agents do not work and as an alternative method, often cheaper than the classically performed ones. There are also cases where stenting is used as a palliative treatment, e.g., to enable defecation in colonic obstruction due to tumour infiltration of the colon wall. Stenting is often a life-saving or comfort-improving procedure for animals, but one should also be aware of possible postoperative complications and be prepared for any adversity. For this reason, this review provides an insight into the current knowledge in veterinary medicine about stenting and the consequences associated with this procedure.

A New Removable Helical Metallic Stent for the Treatment of Tracheomalacia in Children: Study in Pathological Animal Model

BACKGROUND

Congenital tracheomalacia is a pathology with no consensus of medical or surgical approach. The permanent nature and the major complications associated with metallic stents have limited their use over the years. The purpose of this study was to evaluate the feasibility of a helical stent design removal.

METHODS

Ten dogs diagnosed with tracheal collapse and treated with the helical stent were involved in the study. Animals were classified into three groups depending on stent indwelling time. Prior to the removal, endoscopic evaluation was performed to assess endothelization grade, mucous accumulation, and the presence of stenosis. During the removal, bleeding, fracture, or impossibility of removal were noted. After the removal, all macroscopic mucosal changes were recorded.

RESULTS

Technical success was 100%, without any complications. Complete epithelization of the stent was visualized in 7/10 animals. The removal procedure duration ranged from 2-12 min. At post-removal endoscopy, bleeding or epithelial damage, was visualized in any case. Stent fracture during removal occurred in one animal.

CONCLUSIONS

The removal of a metallic stent with spiral geometry is feasible, simple, and without complications, regardless of the degree of neo-epithelialization.

State of the Science in Tracheal Stents: A Scoping Review

OBJECTIVE

Recent material science advancements are driving tracheal stent innovation. We sought to assess the state of the science regarding materials and preclinical/clinical outcomes for tracheal stents in adults with benign tracheal disease.

METHODS

A comprehensive literature search in April 2021 identified 556 articles related to tracheal stents. One-hundred and twenty-eight full-text articles were reviewed and 58 were included in the final analysis. Datapoints examined were stent materials, clinical applications and outcomes, and preclinical findings, including emerging technologies.

RESULTS

In the 58 included studies, stent materials were metals (n = 28), polymers (n = 19), coated stents (n = 19), and drug-eluting (n = 5). Metals included nitinol, steel, magnesium alloys, and elgiloy. Studies utilized 10 different polymers, the most popular included polydioxanone, poly-l-lactic acid, poly(d,l-lactide-co-glycolide), and polycaprolactone. Coated stents employed a metal or polymer framework and were coated with polyurethane, silicone, polytetrafluoroethylene, or polyester, with some polymer coatings designed specifically for drug elution. Drug-eluting stents utilized mitomycin C, arsenic trioxide, paclitaxel, rapamycin, and doxycycline. Of the 58 studies, 18 were human and 40 were animal studies (leporine = 21, canine = 9, swine = 4, rat = 3, ovine/feline/murine = 1). Noted complications included granulation tissue and/or stenosis, stent migration, death, infection, and fragmentation.

CONCLUSION

An increasing diversity of materials and coatings are employed for tracheal stents, growing more pronounced over the past decade. Though most studies are still preclinical, awareness of tracheal stent developments is important in contextualizing novel stent concepts and clinical trials. Laryngoscope, 2021.

In Vivo Molding of Airway Stents

Like ready-to-wear clothing, medical devices come in a fixed set of sizes. While this may accommodate a large fraction of the patient population, others must either experience suboptimal results due to poor sizing or must do without the device. Although techniques have been proposed to fabricate patient-specific devices in advance of a procedure, this process is expensive and time consuming. An alternative solution that provides every patient with a tailored fit is to create devices that can be customized to the patient's anatomy as they are delivered. This paper reports an in vivo molding process in which a soft flexible photocurable stent is delivered into the trachea or bronchi over a UV-transparent balloon. The balloon is expanded such that the stent conforms to the varying cross-sectional shape of the airways. UV light is then delivered through the balloon curing the stent into its expanded conformal shape. The potential of this method is demonstrated using phantom, ex vivo and in vivo experiments. This approach can produce stents providing equivalent airway support to those made from standard materials while providing a customized fit.