An Unusual Cause of Low Oxygen Saturation in the Operating Room

Pulse oximetry is commonly used in clinical practice as an indirect monitor of blood oxygen saturation. There are many factors, however, that can interfere with accurate readings. We present a case of a woman with metastatic thyroid cancer that had a sudden drop in her pulse oximetry during bronchoscopy and that eventually was found to have an uncommon cause for a misleading persistently low oxygen saturation.