Preliminary Studies of Gas Resorption from the Middle Ear

Abstract

¹³³Xenon, dissolved in physiological NaCl, was introduced into the middle ear systems of 9 subjects with normal otoscopic findings. The activity over the middle ear system was measured with a scintillation detector and the activity in the expired air was simultaneously recorded with a separate, shielded detector. In 3 tracheotomized cases the expired air was collected directly from the tracheal cannula. The recordings on living subjects as well as model experiment and measurements on dead subjects show a primary phase of faster decrease mainly due to the mixing of xenon and air in the closed middle ear system. A secondary and slower phase represents the resorption and removal of xenon from the cavity. This means that the decrease of activity of a radioactive gas introduced into the ear does not reflect a real absorption by the vessels in the mucosa before the end of a 8–10-minute period. The half-life has been calculated. There was no correlation between the volume of the middle ear system and the disappearance rate of xenon. If the conditions of resorption are similar or identical for xenon and nitrogen, it seems possible to derive information about nitrogen resorption from data for xenon. From a clinical as well as a physiological point of view nitrogen is the most interesting gas in the middle ear system.