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Severe cases of pediatric tracheobronchomalacia can require tracheostomy, prolonged periods of positive pressure ventilation, and/or invasive surgical procedures intended to stabilize the airways. Prior attempts at therapeutic internal airway stenting to avoid the need for positive pressure ventilation in children have been largely unsuccessful due to poor mucous clearance, fragmentation, and diameter reduction. Surgical approaches are invasive and carry a significant failure rate along with risks of fistulization and other complications.
describe the in vivo evaluation of a new airway stent designed to overcome some of these challenges.
For the design of the stent, the authors borrowed from the wine cabinet (Figure 1) and replicated a corkscrew design constructed from nitinol. The helical nickel titanium wire stents provide radial support set for a certain airway pressure, and provide spaces between the coils for normal mucociliary clearance of the respiratory epithelium. Once in place, the stent is low profile and can be removed with little trauma due to a ball forceps rotational removal system.
Five experimental swine were utilized for 4 weeks, the first 3 with the stent in place and another week without. The stents were tolerated and removed without complication, despite most showing some degree of endothelialization. One migration was noted but remained within the trachea. Polytetrafluoroethylene discs were used to evaluate airway clearance, which was deemed intact. Pathologic review showed inflammation and granulation at the sites of stent wire contact, but intervening segments were without significant tissue damage and <12% of the area was unciliated.
The strength of this study is the longitudinal live animal model with multiple static and dynamic measurements of native airway function following stent placement. The stent design also appears to have clear advantages over existing technology for airway applications. The limitations of the study and device included 1 migration and a relatively low sample size in a model with inevitable differences from human airway anatomy and lack of initial demonstrable tracheobronchomalacia. The diameters of the pig tracheas in this study (range, 11-14 mm) are larger than human neonatal and infant airways that may require intervention before age 1 year (range, 5-6 mm). Further dynamic longitudinal studies in smaller animals may be needed to determine whether the stent accomplishes its intended goal of preventing pediatric airway collapse.
These preclinical results show promise for a new type of stent with successful initial performance in an animal airway model. The potential influence of this new device is excellent, and it could fill a critical vacancy where no good current options exist. This represents another example of important surgical innovation from an exemplary team, and further clinical progress is eagerly anticipated.
Tracheomalacia and tracheobronchomalacia in pediatrics: an overview of evaluation, medical management, and surgical treatment.
Disclosures: The authors reported no conflicts of interest.
The Journal policy requires editors and reviewers to disclose conflicts of interest and to decline handling or reviewing manuscripts for which they may have a conflict of interest. The editors and reviewers of this article have no conflicts of interest.
We sought to demonstrate in an animal model that helical stents made from a nickel titanium alloy called nitinol (NiTi) and designed for malacic airways could be delivered and removed without significant trauma while minimally impeding mucus clearance during the period of implantation.
We were pleased to read the commentaries by Bryant1 and Overbey and colleagues2 on our published preclinical evaluation of a pediatric airway stent.3 We are encouraged by their opinions and concur with their comments toward translating our technology for the treatment of malacic airways in pediatric patients.