Removable Airway Stent Could Transform Lung Surgery

A new knitted airway stent inspired by a pair of socks can be unraveled and completely removed once no longer needed.

Developed by researchers at the Norwegian University of Science and Technology (NTNU), St. Olav’s Hospital, and other institutions, the self-expanding knitted metal stent is made of a single strand of memory alloy nitinol which can be unraveled into the thread from which it was made. The knitting technique also makes it possible to produce the stent for a variety of indications by varying thread thickness and mesh size, thus providing varying radial strengths, dimensions, and shapes, including Y-formation.

The stents are packed into delivery sheaths adjusted from standard vascular introducers, with an outer diameter of 6 French, and delivered by flexible bronchoscopy. In animal studies the new stent was easily and accurately deployed in the central airways, and remained fixed in the original position. It was later easy to unravel and completely remove from the airways without clinically significant complications. Granulation tissue induced by stent placement disappeared spontaneously with the removal. The study was published in the Fall 2016 issue of European Respiratory Journal.

“It sounds simple once you know about it, but basically we tried different ways of removing stents. But it wasn’t until I saw a pair of old-fashioned rag socks that I had a Eureka moment. So that was it,” said senior author Professor Erney Mattsson, MD, PhD, of NTNU. “All we have to do is leave a thread sticking out, and then we have to have a hold on the stent. Then we pull the thread and the stent unravels, and gets smaller and smaller.”

Benign and malignant airway obstruction (MAO) may affect individuals at all ages. Treatment options are numerous, including interventional bronchoscopy, systemic treatment, and endobronchial and extrathoracic irradiation. Minimal invasive treatment using airway stents often represents a meaningful and life-saving palliation, with or without local or systemic supplementary therapy. But the stents can migrate within the airways, cause granuloma formation, mucostasis, pneumonia, mucosal ischemia and fistulas. A removable stent could thus serve an important function in subsequent recovery.