As the diver descends in the water column, the air-filled space of the middle ear is subject to the effects of Boyle's law. With increasing pressure, the volume of the gas in the middle ear reduces proportionately and must be equalized by some technique (see equalizing techniques later in the chapter). Frequent equalization is required near the surface as one descends and less so as the diver achieves greater depth. If equalization is not performed, the volume of the middle ear gas is reduced to the point that the tympanic membrane is retracted severely and fluid or blood (or both) is secreted into the middle ear, reducing the volume and equalizing the pressure. Alternately, the tympanic membrane may rupture.
Because of the unique etiology of diving disorders, the treating physician will see the entire spectrum of middle ear disease from eustachian tube obstruction, occurring rapidly, rather than over an extended period. Because this spectrum is caused by pressure changes, and usually on descent, it is referred to as barotrauma.
Occasionally, middle ear barotrauma can occur with ascent. In this case, the middle ear is equalized at depth, or partially so, and the diver ascends with an obstructed eustachian tube due to rebound rhinitis. The air in the middle ear space increases in volume with a decrease in ambient pressure, and if the middle ear is not vented via the eustachian tube, there will be pain and possible rupture of the tympanic membrane into the external ear canal. Descending to a deeper depth can relieve these symptoms; however, the diver is usually ascending because his/her breathing gas supply is low. Swallowing continually and ascending very slowly may partially relieve the symptoms, but if the gas supply is low, returning to the surface is mandatory. The symptoms, findings, and treatment are the same as for barotrauma of descent.
Middle ear barotrauma can be prevented by not diving when there is any condition that might lead to eustachian tube obstruction (including upper respiratory infection or allergy). The diver should be able to easily equalize the middle ear. Prophylactic oral decongestants, short courses of nasal decongestants (no longer than 3 days because of possible rebound rhinitis), and steroid nasal sprays can assist in preventing obstruction.
Symptoms of middle ear barotrauma range from a dull feeling in the ear to pain and hearing loss. If a perforation of the tympanic membrane occurs, there will be vertigo with nausea and vomiting caused by the passage of water that is colder than body temperature into the middle ear; this water stimulates the lateral semicircular canal (a caloric stimulation).
Physical findings can be as simple as retraction, erythema and injection, or hemorrhage in the tympanic membrane. More severe findings include serous otitis, hemotympanum, and perforation of the tympanic membrane. Tuning fork tests and audiograms reveal a conductive hearing loss.
Treatment of middle ear barotraumas consists of oral decongestants, short-term decongestant nasal sprays, and appropriate antibiotics if secondary infection is present. The diver should stay out of the water until the middle ear is healed and the diver can easily equalize the middle ear. If a perforation occurs, one must wait until the perforation heals and the tympanic membrane is intact again. If surgery is required for a nonhealing perforation, the above requirements must be met, usually requiring 3–4 months after surgery.
Divers should not return to diving until all the symptoms and findings have cleared. There should be ease of equalization of both middle ears confirmed by physical examination, tympanometry with a Valsalva maneuver, or both.
There remains controversy among otologists as to if or when divers who have had middle ear surgery can return to diving. The conditions that usually require myringoplasty or tympanoplasty are caused by eustachian tube obstruction. The surgical site and procedure should be completely healed with no evidence of difficulty in equalizing the middle ear. If ancillary conditions (eg, allergy or sinus disease) contributed to the need for middle ear surgery, they should be completely cleared, and if they recur, diving should be avoided.
Bove AA. Bove & Davis' Diving Medicine, 4th ed. Saunders, 2004. (This text includes a very complete discourse on all aspects of diving medicine. The reader can consult it for much greater detail on the subjects included in this chapter.)
Edmonds C, Lowry C, Pennefather J, Walker R. Diving and Subaquatic Medicine, 4th ed. Arnold/Hodder Headline Group, 2002. (The fourth edition of one of the primary references in diving medicine, it includes detailed coverage of every subject and additional references at the end of each chapter.)