Ultraflex stents for the management of airway complications in lung transplant recipients

OBJECTIVE

We present our experience with the use of the Ultraflex (nitinol) stents in the management of airway complications in lung transplant (LT) recipients.

METHODOLOGY

Nine LT recipients underwent insertion of uncovered Ultraflex stents. Mean change in FEV1, duration to formation of granulation tissue and follow-up post-stent insertion were compared with results obtained in LT recipients who had undergone Gianturco stent (n = 10) and Wallstent insertion (n = 16).

RESULTS

Mean improvement in FEV1 after insertion of Gianturco, Wallstent and Ultraflex stents was 670 +/- 591 mL, 613 +/- 221 mL and 522 +/- 391 mL, respectively. No patient with an Ultraflex stent developed mucus plugging or stenosis at stent extremity at a follow up of 263 +/- 278 days. The mean and median duration to stenosis at stent extremity for patients with Gianturco stents was 102 +/- 85 days and 73 days, respectively, compared with 132 +/- 87 days and 142 days, respectively, for patients with Wallstents. Stricture formation in the middle of the Ultraflex stent occurred bilaterally, at the level of anastomosis in one patient in whom stent placement was undertaken in the presence of inflammation. Stent migration in one patient was related to undersizing of the stent diameter relative to the airway diameter. A larger diameter relative stent was subsequently inserted successfully.

CONCLUSION

Ultraflex stents appear to have fewer long-term complications when used in the management of airway complications following LT.

Thermomechanical study of Ni-Ti alloys

A preliminary study was conducted to demonstrate the usefulness of the combined technique of differential scanning calorimetry (DSC) and mechanical testing for the shape memory metals of 54NiTi and 53NiTiCo(3%) alloys. The DSC technique was used to measure precise transformation temperatures and the amount of thermal energy required for the corresponding phase transformation. The degree of plastic deformation by bending and the effect of alloying (such as Co) were studied with combined DSC and mechanical property measurements.