Transmission of change in the atmospheric pressure of the external ear to the perilymph.
In experiments using guinea pigs, the middle ear and perilymphatic pressures were simultaneously registered in response to pressure change in the external ear canal. In the first experiment, pressure was slowly loaded in the ear canal in the range of 200 mm H2O to -200 mm H2O. Pressure transmission to the perilymph was smaller when the bulla was open to the outside than when it was closed. It was significantly impaired by disruption of the ossicular chain and especially by closure of the round window. The data indicate that air volume in the middle ear cavity plays an important role in transmission of slowly changing atmospheric pressures. In the second experiment, the eustachian tube was closed and the pressure was changed in the range of 1000 mm H2O to -1000 mm H2O. The middle ear and perilymphatic pressures increased or decreased corresponding to the loading pressure in the range of 400 mm H2O and -200 mm H2O. Beyond these levels, response rate of the middle ear pressure decreased and perilymphatic pressure declined in spite of further increase in loading pressure. The increase in pressure difference between the middle ear and the inner ear might cause disruption of the round and/or oval windows.
Nishihara
S
S
Department of Otolaryngology, Ehime University School of Medicine, Japan.
Gyo
K
K
Yanagihara
N
N
D000818:Animals; D001274:Atmospheric Pressure; D001469:Barotrauma / Q000209:etiology; D004431:Ear, External / Q000502:physiology*; D007758:Ear, Inner / Q000502:physiology*; D004432:Ear, Middle / Q000502:physiology*; D006168:Guinea Pigs; D010046:Oval Window, Ear / Q000502:physiology; D010498:Perilymph / Q000502:physiology*; D012405:Round Window, Ear / Q000502:physiology