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Perilymph pressure during hypobaric conditions--cochlear aqueduct obstructed
K S Konrádsson1, A H Carlborg, J C Farmer
1Department of Otolaryngology, University Hospital of Lund, Sweden.
Acta Oto-Laryngologica
|January 1, 1994
Summary
Hypobaric pressure affects the inner ear (labyrinth) via the tympanic cavity, not systemic factors. Eustachian tube patency influences perilymph overpressure during pressure changes.
Area of Science:
- Otolaryngology
- Physiology
- Aerospace Medicine
Background:
- The inner ear's response to pressure changes is not fully understood.
- Previous research has not clearly delineated the pathways of pressure transmission to the labyrinth.
Purpose of the Study:
- To investigate the mechanism by which hypobaric pressure affects the inner ear.
- To determine if pressure changes in the tympanic cavity mediate hypobaric effects on the labyrinth.
Main Methods:
- Nine cats with surgically blocked cochlear aqueducts were exposed to stepwise hypobaric pressure (-5 and -7 kPa) in a pressure chamber.
- Continuous recording of pressures in the perilymph, tympanic cavity, cerebrospinal fluid, and vasculature.
- Observation of pressure changes after restoration of atmospheric pressure.
Main Results:
- Reduced chamber pressure induced relative overpressure in the tympanic cavity, creating pressure gradients affecting the labyrinth.
- Hypobaric effects on the labyrinth were mediated by tympanic cavity pressure changes, not systemic, vascular, or cerebrospinal fluid influences.
- Substantial perilymph overpressure persisted during hypobaric conditions, influenced by Eustachian tube patency.
Conclusions:
- The tympanic cavity acts as the primary mediator of hypobaric pressure effects on the inner ear.
- Eustachian tube patency is a critical factor in regulating perilymph pressure dynamics under hypobaric conditions.
- Restoration of atmospheric pressure resulted in a reversal of labyrinthine pressure to underpressure.