Middle ear gas exchange via the mucosa: estimation by hyperventilation.

CONCLUSION

It is thought that gas exchange via the mucosa occurred in relation to the partial pressure gradient, and it was impaired mainly by inflammatory changes in the mastoid mucosa. It was verified that gas exchange via the mucosa is less likely to be impaired than gas exchange via the eustachian tube.

OBJECTIVES

To evaluate the capacity of middle ear gas exchange via the mucosa by examining the effect of hyperventilation on middle ear pressure.

SUBJECTS AND

METHODS

A total of 55 patients, 40 patients with a type A tympanogram and 15 with type C, were selected. Tympanometry was performed in one ear every 2 min while hyperventilation was forcibly continued for 44-6 min in the supine position. The middle ear pressure and the pressure of end-tidal carbon dioxide (PETCO2) was measured, and sonotubometry was performed.

RESULTS

PETCO2 decreased gradually as hyperventilation continued in all cases. Although middle ear pressure decreased by hyperventilation in 49 of 55 patients, in 6 patients it hardly decreased despite the decrease in PETCO2. These six patients were treated for otitis media with effusion within 1 month before this examination.