The Ear Snorkel – Pressure Chamber Technique: Volumetric determinations of tubal ventilation

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Abstract
A handy pressure chamber technique is devised for clinical studies on the Eusta-chian tube function. A wooden box, enclosing the subject to be studied, functions as a pressure chamber when connected to an ordinary vacuum cleaner which can produce pressure variations from —40 to +40 mm Hg in the box. A tubing then connects hermetically the inner cuff-closed part of the auditory canal of the ear to be examined with the ambient pressure outside, passing airtightly through the wall of the box, i.e. the snorkel – a new principle. The flow direction of the tubal ventilation to or from the middle ear during deglutition is then regulated by varying differently graded pressure levels in the box above or below ambient pressure. Qualitative testing of the tubd function is performed in cases with intact ear drum as well as in clses with chronic otitis, by connecting a flow rate meter device to the ear snorkel tubing outside the box. The determination of the volume of air passing through the tube during each deglutition presupposes a perforated ear drum (as in chronic otitis or after a drum incision). In the present investigation the volume calculations are based on determinations of the pressure changes caused by tubal air passages in a rigid closed tank of known volume, connected to a snorkel tube outside the box. In this new way complete knowledge is obtained as to whether the tube can meet normal physiological demands or not, since for the first time the examination is made quantitatively in both flow directions.

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