In vitro study of the safety limits of bronchoscopic argon plasma coagulation in the presence of airway stents

Abstract

The purpose of this study was to identify the safety limits of bronchoscopic argon plasma coagulation (APC) around indwelling airway stents. This is an experimental in vitro study simulating a patient-care environment. Uncovered and covered Nitinol (Ultraflex), uncovered and covered Wallstent and studded silicone stents were deployed in the tracheobronchial tree of a ventilated and oxygenated heart-lung block from an expired pig. APC was performed at power settings of 40 and 80 W using F(I)O(2) of 0.21, 0.40 and 1.00 and an argon gas-flow rate of 0.8 L/min through a flexible fiberoptic bronchoscope. The primary outcome was the time taken for the APC to cause stent damage. Stent damage was defined as discoloration, ignition or rupture. Airway fires involving all five stents consistently occurred in the presence of 100% oxygen at powers of 40 W and 80 W. At lower F(I)O(2) (0.21 and 0.40) silicone stents were not damaged at 40 W and 80 W. Uncovered Ultraflex stents were undamaged using 40 W at either F(I)O(2) (0.21 and 0.40), but could be damaged using both F(I)O(2) levels when the power was increased to 80 W. Covered Ultraflex and both uncovered and covered Wallstents were damaged at both power settings (40 W and 80 W) and F(I)O(2) (0.21 and 0.40) levels, with a trend towards earlier damage using higher F(I)O(2) and power. Working within the parameters identified in this study (power 40 W, F(I)O(2) 0.21, APC flow-rate 0.8 L/min), APC is a safe method for tissue devitalization and destruction and avoids the risk of airway stent ignition, especially if short bursts of APC are employed. The safety limits identified using an F(i)O(2) of 0.4, however, are also important because some patients undergoing resection may require oxygen therapy.