Neodymium-YAG (yttrium-aluminum-garnet) laser resection of obstructing and inoperable tumors of the large airways is used as palliative therapy to improve the quality of survival in patients by alleviating airway obstruction. Rapid changes in oxygenation and ventilation can occur during these procedures. In a study of 14 patients, transcutaneous oxygen (PtcO2) and carbon dioxide (PtcCO2) monitors responded slowly to these changes and frequently provided misleading values. Pulse oximetry (SNO2) accurately reflected arterial oxygen saturation but did not indicate severe desaturation until arterial oxygen tension approached dangerously low values. Thus, we did not find PtcO2 or PtcCO2 monitoring to be clinically useful during neodymium-YAG laser resection of airway tumors through a rigid bronchoscope. SNO2 was clinically useful and accurate; however, a large decrement in oxygenation may occur before changes in oxygen saturation ensue and are detected.