title: Direct demonstration of gas diffusion into the middle ear.
abstract: The gas composition of the middle ear differs from that of air, and resembles the gas composition of mixed venous blood. This observation suggests the existence of a bi-directional route for gas diffusion between the middle ear and blood. In an attempt to demonstrate this route in a direct way, we tracheotomized guinea pigs in such a way that they breathed freon-22 directly into the distal part of their tracheostomy. The proximal part of the trachea was sealed so that air by-passed the oropharynx and nasopharynx, thus preventing freon-22 from making contact with the eustachian tube orifice. At the same time middle ear gases were monitored with a mass spectrometer, through a measuring probe which was inserted into a hole in the bulla. The appearance of freon-22 in all middle ears--after 8 min on the average--demonstrated direct gas diffusion from the blood into the middle ear, since freon-22 could reach the middle ear only from the blood stream, i.e., by diffusion. Differences in gas diffusion rates into and from the middle ear may therefore play a role in regulating middle ear gas economy, and therefore in middle ear pressure.
authors.affiliation: Ear Research Laboratory, Sackler School of Medicine, the Bioengineering Program, Tel Aviv University, Ramat Aviv, Israel.
authors.forename: D
authors.initials: D
authors.lastname: Levy
authors.forename: M
authors.initials: M
authors.lastname: Herman
authors.forename: M
authors.initials: M
authors.lastname: Luntz
authors.forename: J
authors.initials: J
authors.lastname: Sadé
mesh_terms: D000818:Animals; D001784:Blood Gas Analysis; D005617:Chlorofluorocarbons, Methane / Q000032:analysis; D004432:Ear, Middle / Q000737:chemistry* / Q000503:physiopathology / Q000601:surgery; D005064:Eustachian Tube / Q000502:physiology; D005260:Female; D006168:Guinea Pigs; D013058:Mass Spectrometry; D008876:Middle Ear Ventilation; D010033:Otitis Media / Q000503:physiopathology; D001261:Pulmonary Atelectasis / Q000503:physiopathology
chemical_list: D005617:Chlorofluorocarbons, Methane