On Physiological and Experimental Variation of the Perilymphatic Pressure in the Cat

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Abstract
The closeness of the hydrodynamic relationship between the perilymph and the cerebrospinal fluid (CSF) in different animal species and man is still debatable. the effect of variation of some basic physiological conditions on the perilymphatic pressure (Pp) was investigated in cats during simultaneous recording of the CSF, venous and arterial pressures. the perilymphatic pressure proved very sensitive to even moderate hypoxia and hypercapnia, both causing a rapid rise in the perilymphatic pressure. the therapeutic use of CO2 breathing in cases of sudden sensorineural hearing loss was thus questioned. Changes in position of the body caused a similar change in the Pp. and Pcsf- During a prolonged change in body position a pressure gradient was established between the Pp and Pcsf because the Pp fell slightly more than Pcsf. Blood pressure changes induced by neck vein compression, overhydration and exsanguination had a marked influence on the Pp and /CSF. the experiments showed that any change in the CSF pressure caused a corresponding change in the mean perilymphatic pressure with a minor or. in most cases. no time lag at all. This indicates a wide open communication between the CSF and the perilymphatic spaces in most cats.