Experimental pressure induced rupture of the tympanic membrane in man.

The size of the overpressure in the ear canal which causes rupture of the tympanic membrane (TM) in man (rupture pressure, RP) was determined in 90 subjects 7-112 h post mortem in connection with the autopsy. The equipment allowed an overpressure in the ear canal to be applied either gradually or suddenly. In 144 normal TMs it was demonstrated that the tensile strength of the TM increases post mortem. Corrected to the time 0 post mortem, RP of normal TMs ranged 0.5-2.1 kp/cm2, median 1.2 kp/cm2. It was found to be correlated to the age of the patient, i.e. RP decreased with increasing age. No correlation was found between RP and the application speed of the overpressure. Ninety-nine percent of the ruptures were localized to the pars tensa (63% to the anterior part of this structure) and typically had the shape of a minor tear. The RP of 23 TMs with atrophic scars was significantly lower, 0.3-0.8 kp/cm2, and the rupture typically had the shape of a larger defect. The results of this study indicate large intersubject variability of the tensile strength of the human TM. Some individuals are at increased risk of TM rupture at minor overpressures in the ear canal (e.g. during certain watersports, such as diving) which may carry medicolegal implications.