Middle Ear Pressure Changes with lnert Gas Respiration; Effect of Helium and Argon

Abstract

Middle ear pressure is thought to be an important factor in the pathogenesis of otitis media. It is well known that body position, type of breathing, and kind of inhaled gas influence middle ear pressure. There is an increase in middle ear pressure when general anesthesia is induced with a gas such as nitrous oxide. In this study, an attempt was made to answer the question as to whether the inhalation of non-anesthetic inert gas can increase middle ear pressure.
Eight ears were selected: 4 atelectatic ears and 4 infantile ears. Helium-oxygen mixture gas (He 79%, O₂ 21%) or argon-oxygen mixture gas (Ar 79%, O₂ 21%) was administered via face mask for 120 minutes, and middle ear pressure was measured with tympanometry just before and during gas inhalation. The middle ear pressure changes during gas inhalation were compared with those during air respiration.
The results were as follows;
1. Middle ear pressure was increased by the inhalation of argon-oxygen mixture gas. However, no specific pressure change was noted in the middle ear during inhalation of helium-oxygen mixture gas.
2. The difference in pressure in the middle ear during helium-oxygen inhalation and argon-oxygen inhalation might be due to the different solubility coeffients of the two inert gases.