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Observations of middle ear pressures. Commentary with movie
Abstract:
Previous direct measurements of middle ear pressure in ears with serous otitis resulted in the range of from 0 to -10 mm H2O pressure. To confirm these findings we attempted to quantify middle ear pressures by doing myringotomies in serous otitis patients through sterile saline solution. We compared the rate of aspiration of the saline in ears with serous otitis to the rate of aspiration of saline after an experimental myringotomy in an ear model in which known pressures were imposed. To record our findings we used motion picture photography. Layering a film of sterile oil suspension of oxytetracycline and hydrocortisone over dry tympanic membrane perforations resulted in the demonstration of a pulsatile positive pressure of about 6 mm water in many of the ears which we tested. The oil film often formed an external bubble which ruptured after several minutes. In some ears there was no change in pressure and in only a small percentage there was evidence of a decreased pressure by absorption of air in the middle ear during the period of observation. This positive pressure is unrelated to swallowing and suggests that the current theories of middle ear aeration via opening of the eustachian tube may not be valid. These findings were demonstrated with motion picture film.
Insights
This study found a pulsatile positive pressure in many middle ear infections, challenging current theories on how the middle ear ventilates. Further research is needed to understand this pressure in serous otitis.
Area of Science:
- Otolaryngology
- Biomedical Engineering
- Medical Physics
Background:
- Previous measurements indicated negative middle ear pressure in serous otitis.
- Current theories propose eustachian tube function for middle ear aeration.
Purpose of the Study:
- To quantify middle ear pressure in serous otitis.
- To investigate the mechanism of middle ear pressure regulation.
Main Methods:
- Myringotomy in serous otitis patients with sterile saline.
- Comparison with an experimental ear model with known pressures.
- Motion picture photography for recording pressure dynamics.
Main Results:
- A pulsatile positive pressure of approximately 6 mm water was observed in many tested ears.
- Some ears showed no pressure change; a small percentage exhibited pressure decrease via air absorption.
- The observed positive pressure was independent of swallowing.
Conclusions:
- Findings challenge the prevailing theories of middle ear aeration solely through eustachian tube opening.
- A novel positive pressure mechanism in serous otitis requires further investigation.