The influence of an insecticide on the function of the eustachian tube

Organophosphorus compounds in the form of insecticides are in widespread use and have recently attracted considerable interest as environmentally toxic agents. As little is known about the effect of environmental toxins on the tubal function in the ear, we studied the middle ear pressure necessary to force the eustachian tube to open (POL = pressure opening level) under physiological conditions in laboratory mini pigs and under the influence of an i.v. organophosphorus compound (Paraoxon). The median POL in the untreated animals was 6.4 kPa (n = 8). After intoxication with Paraoxon the median POL increased to 12.0 kPa (n = 8). Tubal instillation of surfactant in intoxicated pigs reduced the POL to a median of 7.3 kPa (n = 8), while in non-intoxicated animals (n = 4) it also lowered the POL, though not significantly. These results suggest that organophosphorus compound interferes with the surfactant-dependent tubal patency.