Gas diffusion in the middle ear.

The ex vacuo theory, claiming that in cases of middle ear underaeration air enters the middle ear through the Eustachian tube in diminished amounts while oxygen continues to leave it into the blood by diffusion as in normal condition, does not provide a complete explanation for the aeration problems encountered in middle ear pathology. This study shows that when atelectatic ears are politzerized (hyperinflated) with different gases, these gases disappear with a speed that correspond to the diffusion coefficient of the different gases. This finding together with the fact that the composition of middle ear gases is very similar to that found in the venous circulation suggests that it is a diffusional process of several gases from the middle ear into the blood and in the opposite direction that mainly determines the middle ear pressure.