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Middle Ear Gas Composition during Nitrous Oxide-Oxygen Ventilation

1980; SAGE Publishing; Volume: 89; Issue: 2 Linguagem: Inglês

10.1177/000348948008900214

1943-572X

Ervin Ostfeld, Judith Blonder, Moshe Crispin, À. Szeinberg,

Respiratory Support and Mechanisms

The middle ear gas composition during 180 minutes ventilation with nitrous oxide-oxygen mixture was determined in 12 mongrel dogs. The mean relative concentration of N 2 O in the middle ear (ME) rose to 12, 26.4 and 29.3% after 60, 120 and 180 minutes respectively. During this period, the relative concentration of N 2 dropped from a mean of 83.2% in the air-ventilated dogs to 54.8%, without an essential change in the concentrations of O 2 or CO 2 . The elimination of N 2 O from the ME during 30 minutes of postanesthetic ventilation with O 2 was incomplete, an average of 11.4% N 2 O remaining in the ME. At the same time, the mean relative concentration of O 2 reached 19%, higher than the O 2 relative concentration normally present in the ME. The results indicate that gas diffusion may occur across the ME mucosa for N 2 O as well as for O 2 , producing selective changes in the middle ear gas composition.