Thermal ablation (use of treatment modalities that generate heat) has become a widely used tool for treatment of central airway obstruction (e.g. laser, electrocautery, radiofrequency, and argon plasma coagulation). However, this method carries with it an increased risk for airway fire - a surgical fire that occurs in a patient's airway and could also include a fire in the attached breathing circuit. To decrease the risk of airway fire during mechanical ventilation with an endotracheal tube, the concentration of inspired oxygen (FiO2) is set below 40% while waiting for end tidal oxygen concentration (EtO2) to fall below 40% prior to starting thermal ablation. There is no published literature describing O2 concentration within the airways (AiO2) during jet ventilation with rigid bronchoscopy. The co-investigators of this study have recently collected data on AiO2 during rigid bronchoscopy using manual low frequency jet ventilation/high frequency jet ventilation with a period of apnea. The intent of this study is to measure the time taken for the central airway oxygen concentration to drop from 90 to 40% when the laser mode is activated on the Monsoon jet ventilator. Ventilation is continued during laser mode.