Middle Ear and Maxillary Sinus During Nitrous Oxide Anesthesia

Abstract

The solubility of nitrous oxide in blood is 35 times that of nitrogen. Nitrous oxide will invade a closed air-filled cavity in the body 30 times faster than the enclosed nitrogen of the same partial pressure will escape, resulting in a pressure increase before equilibrium is established. In the middle ear an initial pressure increase ranging from 2–10 cm H₂O per minute has been demonstrated in several subjects during nitrous oxide anesthesia (50% of nitrous oxide in pure oxygen). Measurements of the flow of air from the maxillary sinus showed that 2–4.7 cm³ of air emanated during the first 30 minutes. Analyses of this air showed a steadily increasing concentration of nitrous oxide.