Inert gas exchange in the middle ear.

A novel mathematical description of inert gas exchange in the middle ear has been formulated and related to experimental measurements of the middle ear exchange of helium, neon, and nitrous oxide in the cat. This study indicates that the diffusion of gases across the tympanic membrane is not significantly affected by its blood supply and that the diffusion of gases across the mucosal layer of the middle ear cavity in perfusion limited. The diffusion of helium and neon is consistent with an aqueous model of the tympanic membrane, while that of nitrous oxide is one-tenth of the expected value for an aqueous membrane.