The effects of the vacuum on vascular permeability of the middle ear.

Following local application of various degrees of negative pressure to the middle ear, the authors observed changes in vascular permeability in guinea pigs, using Majno's vascular labelling technique. Increased permeability and effusions were seen in all experimental middle ears. Any pressure below -5 mm of mercury induced middle ear effusions. Accordingly, a decrease in pressure developed in the middle ear cavity may cause transdation of serum drawn from the submucosal vessels, resulting in fluids in the middle ear of aero-otitis. In such a circumstance, mast cells which are easily influenced by atmospheric pressure may be involved in increasing vascular permeability.