EVIDENCE OF SURFACE-ACTIVE AGENT IN THE EUSTACHIAN TUBE o PHILIP

N.

RAPPORT,

DAVID J. LIM, M.D.

M.D. HAROLD

S. WEISS, PH.D.

COLUMBUS, OHIO

The main function of Eustachian tube opening is equalization of pressure between the middle ear and the atmosphere. Improper function of the tube may contribute to middle ear infections and serous otitis media. It has been postulated that there is a surface-active agent (SAA) in the Eustachian tube which normally facilitates tubal opening but which may be inactivated by infection, resulting in poor tubal function. The present experiment was an attempt to demonstrate the effect of this

surface-active agent by measuring changes in Eustachian tube opening pressure following removal of the suspected tubal surface-active agent by saline. To make these measurements, air or normal saline was injected into the middle ear of 15 fresh guinea pig temporal bones until pressure was sufficient to open the Eustachian tube. In each ear tested, a higher pressure was required to open the Eustachian tube after it had been washed with saline (p < .001). Also, tubal opening became progressively easier with consecutive opening trials before washing (p < .001), but not after washing (Fig. 1). These phenomena were interpreted to be the result of the presence and subsequent removal of a tubal surface-active agent ( SAA). The present

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