Temporary or permanent tracheal splinting in pediatric patients may be indicated in
tracheomalacia or
bronchomalacia, repair of
congenital tracheal stenosis, and after tracheal resection. This study presents the results of the development of a new intraluminal airway
stent made from
titanium alloy, a
metal with "shape memory effect". At low temperatures (martensitic state) the
titanium alloy stent can be fashioned into a specific shape; then when heated to a higher temperature (austenitic state) the
stent alters its shape, only to regain its original shape when recooled to the lower temperature. The
stent, connected to a small
electric power supply, was introduced into 20 young rabbits with the use of a 2.5 cm rigid
bronchoscope. After implantation in the martensitic state the
stent was warmed to 40 degrees C, the austenitic state, by an electric current of 1.5 to 3 ampere for 1 to 2 seconds. After a period of 8 to 10 weeks the
stent was removed (in its martensitic state) through the same-sized
bronchoscope after being cooled with 3 to 4 ml of 80% alcohol
solution at 6 degrees C. No signs of
airway obstruction developed in any of the animals after implantation or extraction of the
stent. The biomechanical properties of the trachea, as shown by strain measurements with the use of incremental forces, showed significant differences between the stented and unstented segments (p < 0.005). The
titanium alloy intratracheal
stent adequately fulfilled the requirements of a temporary intraluminal airway
splint, and because of its unique feature of shape memory effect the
stent could be inserted, fixed, and removed easily, even in very small airways.