Eustachian tube function in the chinchilla
W. J. Doyle
Eustachian tube function (ETF) was evaluated in 22 ears of 18 chinchillas
using the inflation-deflation and forced-response protocols. The results of
the ETF tests showed an unusual function in the chinchilla. Of the 22
tests, one indicated a patulous eustachian tube (ET) and 20 suggested a
semipatulous ET. This was evidenced by a passive, pressure-dependent,
complete reduction of applied positive or negative ME pressures in these
ears. This phenomenon has no counterpart in the ETF of rhesus monkeys or
humans. Discrete changes in the continual leakage of applied pressures,
indicative of active tubal dilation, were only observed during tests in
four ears. Passive tubal resistance was similar to that of humans, though
all values were characterized by large variances. Active tubal resistance
could only be defined for four of the test ears. The ET of eight ears
constricted with swallowing. In nine test ears, neither constriction or
dilation was observed during the forced-response test, and four tests
showed dilation of the ET with swallowing. These results show that the ETF
of the chinchilla is radically different from that of humans or monkeys.
