Pediatric Airway Stent Designed to Facilitate Mucus Transport and Atraumatic Removal

Abstract

The goal was to develop a pediatric airway stent for treating tracheobronchomalacia that could be used as an alternative to positive pressure ventilation. The design goals were for the stent to allow mucus flow and to resist migration inside the airways, while also enabling easy insertion and removal. Methods: A helical stent design, together with insertion and removal tools, is presented. A mechanics model of stent compression is derived to assist in selecting stent design parameters (pitch and wire diameter) that provide the desired amount of tracheal support, while introducing the minimal amount of foreign material into the airway. Worst-case airway area reduction with stent support is investigated experimentally using a pressurized tracheal phantom matched to porcine tracheal tissue properties. The stent design is then evaluated in a porcine in vivo experiment. Results: Phantom testing validated the mechanics model of stent compression. In vivo testing demonstrated that the stent was well tolerated by the animal. Since the helical design covers only a small portion of the epithelium, mucus transport through the stented region was minimally impeded. Furthermore, the screw-like stent resisted migration, while also providing for atraumatic removal through the use of an unscrewing motion during removal. Conclusion: The proposed stent design and tools represent a promising approach to prevent airway collapse in children with tracheobronchomalacia. Significance: The proposed technology overcomes the limitations of existing airway stents and may provide an alternative to maintaining children on a ventilator. Index Terms-Tracheobronchomalacia, airway stent. I. INTRODUCTION T RACHEOBRONCHOMALACIA is the most common congenital defect of the central airways [1] and has been identified in up to 15% of infants and 30% of young children undergoing bronchoscopic examination for respiratory distress [2]. The condition arises due to intrinsic weakness of the wall and cartilaginous support. For these children, during dynamic expiration and coughing at low lung volume, pleural pressure exceeds intraluminal pressure resulting in airway collapse [3],

In Vivo Molding of Airway Stents

“…Furthermore, helical airway stents made from superelastic nitinol (NiTi) metal have previously been demonstrated to possess a number of desirable properties including resistance to migration, minimal disruption to mucus flow, and the ability to maintain patency of malacic airways while not eroding through tracheal tissue. [ 12,22,23 ] Moreover, if a helical stent becomes endothelialized, it can be removed with minimal damage to the airways using an unscrewing motion similar to how a corkscrew is removed from a cork. [ 12 ]…”

“…[ 12,22,23 ] Moreover, if a helical stent becomes endothelialized, it can be removed with minimal damage to the airways using an unscrewing motion similar to how a corkscrew is removed from a cork. [ 12 ]…”

“…While the use of polymers enables the design of stents with a broad range of mechanical stiffnesses, they are also much more compliant than metals. Since helical NiTi stents have been demonstrated to provide sufficient radial support and resistance to migration while not eroding through tracheal tissue, [ 12,22,23 ] our goal was to demonstrate that we could fabricate in vivo molded stents of a comparable stiffness. We selected tubing with an inner diameter of 1.14 mm and an outer diameter of 1.57 mm.…”

“…[ 9 ] It is also important for the stent to allow cilia‐mediated mucus flow through the stented region so as to avoid mucus plugging of the stent or mucus entrapment between the stent and the airway wall. [ 10–13 ]…”

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

“…In pediatric patients, the device must allow an atraumatic placement as well as the exchange. 35 For this reason, we have developed a new shape stent with the same characteristics of the classical devices, avoiding its complications.…”