ExostosesĮxostoses are bony outgrowths of the medial ear canal. 6 The principles of treatment remain the same as for non-divers, with dry ear precautions, aural toilet and topical antimicrobial therapy. 5 Pseudomonas aeruginosa is the organism most responsible for acute otitis externa following diving. Prolonged exposure of the ears to water results in a change in canal pH and skin maceration, damaging the primary skin barrier and promoting infection. Otitis externa is common among those who spend considerable amounts of time submerged underwater. During uncontrolled ascent, the reduction in pressure causes release of dissolved gas nitrogen bubbles within tissues or blood that can lead to cell injury and hypoxia, causing the symptoms of DCS. Henry’s Law dictates that as the partial pressure of a gas increases, a greater amount becomes dissolved in surrounding liquids. Boyle’s law dictates that as pressure increases below the water surface, the volume of closed spaces decreases.Īs ambient pressure increases, so does the partial pressure of each of the gases within the environment. This accounts for direct pressure–related ear injuries during diving.įigure 1. If equalisation does not occur, then a vacuum is created, placing pressure on the tympanic membrane and round and oval windows (the flexible walls of this space). The middle ear, being an air-filled space, correspondingly reduces its volume by 50% in the first 10 m of descent (Figure 1). As the diver descends, ambient pressure increases. Boyle’s Law (P1V1 = P2V2) dictates that the pressure and volume of a gas at a constant temperature are inversely proportional. Two important laws of physics govern the physiology associated with pressure changes during scuba diving. For most purposes, atmospheric gas is made up of 21% oxygen and 79% nitrogen, similar to compressed gases found in a scuba tank. For every 10 m a diver descends below this level, the ambient pressure increases by 1 atm. At sea level the atmospheric pressure is 1 atmosphere (atm). Otological diving injuries occur as a result of the effect of ambient pressure changes on the ear structures. 3 Inner ear DCS (IEDCS) is rare, with an estimated recreational diving incidence rate of 0.01–0.03%. 2 Decompression sickness (DCS) is one of the most severe diving-related complications and has an Australian incidence rate of 10 per 100,000 dives. 1,2 Middle ear barotrauma (MEB) is most common, accounting for nearly 50% of presentations. Epidemiologyĭiving-related otological injuries account for 65–72% of all diving-related presentations to practitioners. As many patients present to the GP with diving-related concerns, it is pertinent that treating clinicians are aware of the common presentations, initial treatment and prevention of such injuries. Incorrect diagnosis and management of otological diving injuries can lead to significant morbidity including chronic vestibulopathy and hearing loss. While the results show whales, like other mammals, are subject to severe blast trauma, it remains unclear whether lower level stimuli induce temporary and/or acute threshold shifts in marine mammals.Scuba diving, during which a diver uses a self-contained underwater breathing apparatus (scuba), is a popular recreational activity resulting in frequent presentations to the general practitioner (GP). There was no evidence that the pathologies found in these whales resulted from repeated barotrauma or chronic infection, and no similar abnormalities were found in control ears from humpbacks not exposed to blasts. These observations are consistent with blast injury reports in humans, particularly with damage to victims near the source who sustained massive, precipitous increases in cerebrospinal fluid pressure. In one animal, there were bilateral periotic fractures. Evidence of mechanical trauma was found in all four ears: Round window rupture, ossicular chain disruption, sero‐sanguinous effusion of peribullar spaces, and dissection of the middle ear mucosa with pooled sera. In this study, temporal bones from two humpback whales, which died following a 5000‐kg explosion in Trinity Bay, Newfoundland, were harvested, preserved in formalin, scanned with 1‐mm‐high resolution spiral CT, decalcified, and sectioned at 20 μ. External injuries consistent with inner ear damage have been found in dolphins subjected to Class C explosives, but often little change is seen in surface animal behavior near blast areas. To date, there is no published report of effects on marine mammal hearing from underwater explosions.
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