 Emergency surgery, or any other aspiration risk Minor, age 18 Pregnant Febrile illness Contraindication to nasal instrumentation Allergy to propofol Malignant hyperthermia Requiring Total Invravenous Anesthesia TIVA Inability to oxygenate on less than 50 FiO2 Intra-cranial surgery Receiving vasoactive medications Significant valvular heart disease Unstable cardiac disease Surgery requiring prone or lateral positioning Contraindication to nitrous oxide Prisoners 