Inner Ear Disorders in SCUBA Divers: A Review

Abstract

Self-Contained Underwater Breathing Apparatus (SCUBA) diving is a popular sport. However, improper diving may injure different organs. The majority of dive-related disorders concern otolaryngology, and may include hearing loss, tinnitus, aural fullness, disequilibrium, and vertigo. Three main inner ear pathological conditions can occur underwater: inner ear barotrauma (IEB), inner ear decompression sickness (IEDS), and alternobaric vertigo (AV). IEB results from inappropriate equalization of middle ear pressure and consequent inner ear injury produced by pressure changes within the middle ear; IEDS is characterized by the formation of gas bubbles within the vessels of the inner ear during rapid ascent; AV typically develops while ascending or performing the Valsalva maneuver and can follow asymmetrical equalization of middle ear pressure transmitted via the oval and round window membranes. The clinical pictures of these pathological conditions are partly superimposable, even if they have specific peculiarities. Before starting SCUBA diving, a fit-to-dive assessment is recommended. It should include an otolaryngologic examination with audiological assessment to evaluate nasal, middle ear, and tubal patency and to minimize the risk of IEB, IEDS, and AV. It is of utmost importance to identify individual risk factors and predisposing pathological conditions that favor inner ear injury before diving, to prevent acute events and preserve auditory and vestibular functions in SCUBA divers. This review aims to provide an overview of the pathological conditions characterized by inner ear injury in SCUBA divers, discussing their pathogenetic mechanisms, diagnostic work-up, and prevention.

Figure 1.

Boyle's law: at a given temperature, the volume of a gas is inversely proportional to its pressure.

Figure 2.

Henry's law: at a constant temperature, the amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid.

Figure 3.

Schematic diagram of inner ear barotrauma: pressure increases during descent and a Valsalva maneuver can help equalize the middle ear pressure. (A) In the case of a patent Eustachian tube, if a vigorous Valsalva maneuver is performed, an uncontrolled increase in pressure in the middle ear occurs with a consequently violent outward displacement of the stapes footplate and inward movement of the slight round window membrane. (B) If the Eustachian tube is blocked, lower pressure in the middle ear occurs. A forceful Valsalva at this stage can increase the cerebrospinal fluid pressure (CFP) and consequently favor round or oval window rupture.