Surface tension of secretions from eustachian tube and middle ear

The surface tension of secretions from the pharyngeal orifice of the eustachian tube in eight rabbits was analyzed with a modified maximum-bubble pressure method. Measurements were made before, during, and after intravenous injections of isoprenaline (10 micrograms/kg). Surface tension was found to be 57.6 +/- 0.9 (mean +/- SEM) mN/m before injections, and was not significantly changed by isoprenaline. The surface tension in middle-ear secretions from children with secretory otitis media was also determined, the serous type of secretion measuring 62.0 +/- 1.4 mN/m (n = 8), and the mucoid type 70.7 +/- 2.6 mN/m (n = 9). In another ten humans, measurements of tears were performed, and the surface tension was found to be 59.9 +/- 2.2 mN/m. This bubble technique promises to be useful for the evaluation of surface tension when the available sample volume is very small.