Biomaterial Database

[Analysis of middle ear cavity gas composition by mass spectrometry]. 1994

J Okubo, and M Noshiro

Department of Otorhinolaryngology, Tokyo Medical and Dental University.

Gas compositions in the middle ear cavities of patients with a perforated tympanic membrane, and in normal subjects, were analyzed by mass spectrometry. The results showed that the gas in normal subjects consisted of nitrogen (83.7%), oxygen (9.2%) and carbon dioxide (6.2%). (The volume concentration of the various gases was expressed as a percentage of 713 mm Hg.) Thus, the concentrations of the various gases in the middle ear cavity differed greatly from those in the atmosphere. The low concentration of oxygen is suitable for microaerophilic bacteria and acts as a physiological barrier against bacterial infection. It was also found that the gas in patients with exudative otitis media consisted of nitrogen (77.9%), oxygen (15.6%) and carbon dioxide (5.5%), and in patients with chronic perforated otitis media, of nitrogen (77.8%), oxygen (16.9%) and carbon dioxide (4.4%). The concentration of oxygen in the middle ear cavity with perforated tympanic membrane is higher than that in the normal state because of diffusion of atmospheric gas into the middle ear cavity. In other words, perforation of the tympanic membrane exposes the middle ear cavity to a nonphysiological gaseous condition. The diffusion of atmospheric gas was simulated using small cylinders. Simulated results revealed that the atmospheric gas diffused rapidly. The change in the gas concentration during diffusion was approximated by an exponential function and a constant, and reproduced by a mathematical model. The change in the gas concentration in the middle ear cavity was usually approximated by two exponential functions and a constant. The constant represents the estimated final value of the gas concentration from which the effect of the diffusion is excluded. The final values were estimated for normal subjects and patients with perforated tympanic membrane. The final values in the normal subjects were almost equal to the measured values. The final value of carbon dioxide in the patients was greater than the measured value and nearly equal to the final value in the normal subjects. The final oxygen value in the patients was smaller than the measured value, but still greater than the final value in the normal subjects. The high oxygen concentration in the patients suggests enhanced oxygen metabolism.

UI	MeSH Term	Description	Entries
D008297	Male		Males
D008875	Middle Aged	An adult aged 45 - 64 years.	Middle Age
D009584	Nitrogen	An element with the atomic symbol N, atomic number 7, and atomic weight [14.00643; 14.00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth's atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells.
D010100	Oxygen	An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.	Dioxygen,Oxygen-16,Oxygen 16
D010313	Partial Pressure	The pressure that would be exerted by one component of a mixture of gases if it were present alone in a container. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Partial Pressures,Pressure, Partial,Pressures, Partial
D002245	Carbon Dioxide	A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.	Carbonic Anhydride,Anhydride, Carbonic,Dioxide, Carbon
D004432	Ear, Middle	The space and structures directly internal to the TYMPANIC MEMBRANE and external to the inner ear (LABYRINTH). Its major components include the AUDITORY OSSICLES and the EUSTACHIAN TUBE that connects the cavity of middle ear (tympanic cavity) to the upper part of the throat.	Tympanic Cavity,Tympanum,Middle Ear,Cavities, Tympanic,Cavity, Tympanic,Ears, Middle,Middle Ears,Tympanic Cavities,Tympanums
D005260	Female		Females
D005740	Gases	The vapor state of matter; nonelastic fluids in which the molecules are in free movement and their mean positions far apart. Gases tend to expand indefinitely, to diffuse and mix readily with other gases, to have definite relations of volume, temperature, and pressure, and to condense or liquefy at low temperatures or under sufficient pressure. (Grant & Hackh's Chemical Dictionary, 5th ed)
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man