Sensory experience induced by nitrous oxide analgesia.

Preliminary findings on a group of 15 dental patients, treated with nitrous oxide indicated frequent occurrence of several, well-defined sensory experiences related to various modalities. A subsequent controlled experiment carried out on 44 volunteers, inhaling a 35% N2O + 65% O2 sedative gas-mixture as well as O2 alone in two different sessions confirmed a large variety of sensations not related to external stimuli. Taste and/or odor and thermal sensations were often reported as well as changes in auditory or visual perception of the environment in addition to reports of general heaviness, relaxation or tingling.