Experimental background for the use of tympanostomy tubes

Already within 24 h, splitting of the soft palate in rats caused production of effusion in the attic space. During the next couple of days the effusion material filled the meso- and hypotympanon. The production of a serous fluid in the attic space appeared concomitant with an elevated histamine content in the middle ear cavity, irrespective of whether the ears were ventilated or not. In the artificially ventilated middle ears no effusion appeared in the meso- and hypotympanon and the hypotympanal mucosal lining remained normal. The serous effusion filling the middle ear cavities with the intact tympanic membranes was replaced at about 7 days by a purulent effusion material containing mainly Gram-negative enteric rods. Thus it seems that a serous otitis media and a purulent otitis media occur in a continuum. The change to a purulent infection could be prevented by artificial ventilation, but as soon as the myringotomies were healed or the tympanostomy tubes got clogged a flocculent, pus-like effusion also appeared in these middle ear cavities.