How is Eustachian Dysfunction related to Inner Ear Barotrauma

Diving and Hyperbaric Medicine Volume 46 No. 2 June 2016

Normal Eustachian tube (ET) function is important for fitness to dive. Eustachian tube dysfunction may result with ear injury during diving. The most common diving injury related to Eustachian tube dysfunction is middle ear barotrauma, and less common but more grave is inner ear barotrauma (IEBt). While middle ear barotrauma usually heals well, inner ear barotrauma may cause permanent damage if not recognized and treated on time and thus, the prevention of IEBt is very important. The Diving and Hyperbaric Medicine Volume 46 No. 2 June 2016 brings three articles addressing these issues.

Kitayima and co-authors studied Eustachian tube function in 16 divers who experienced IEBt and in 20 healthy divers without history of IEBt. They correlated the function of Eustachian tube to the incidence of IEBt. They measured the opening pressure for ET, the divelab20161013maximum volume of the air in the middle ear and the speed at which the equalization occurs. In the ideal conditions, the pressure differential needed to open the ET in either direction is 200 to 650 daPa which corresponds to a pressure gradient caused by depth change of 20 – 65 cm or 8-26 inches. The maximum volume of air in middle ear varies from 0.2 to 0.9 ml. The paper describes three main type of ET based on the equalization characteristics: patulous (open) ET, normal ET and stenotic (narrowed) ET. The patulous ET is open permanently or it takes pressure differential of less than 200 daPa to open it. Normal ET is collapsed but it takes less than 650 daPa to open it and it fills or empties instantaneously. The stenotic ET takes larger pressure (up to 1200 daPa/120 cm H2O measured) to open it or it fills and empties very slowly.

In healthy divers without a history of IEBt, one third had slow equalizing ET but the pressure differential required was within normal range. They avoided IEBt so far, probably by practicing slow ascent but they often experienced alternobaric vertigo. Among divers with IEBt, most had dysfunctional ET requiring either greater pressure differential to open it and/or it took longer time to equalize. However, some divers with IEBt had normal ET function at the time of measurement. Divers with IEBt and perilymph fistula had more severe ET dysfunction. Authors suspect that excessive pressure caused by forceful Valsalva may have been the cause of IEBt in some divers and especially in those with normal opening pressures but who became impatient with equalization and blew to strongly.

Morvan and co-authors presented a series of 11 cases of perilymphatic fistula due to IEBt in scuba divers. The perilymphatic fistula is most severe form of IEBt but it diagnosis is not always obvious. Dizziness, hearing impairment and tinnitus after scuba diving indicate likely injury of inner ear but the cause may be either decompression sickness or barotrauma. Delayed onset, fluctuation and progressive deterioration of deafness point toward perilymph fistula. In either case, occurrence of cochlea-vestibular symptoms after a dive is an emergency. Early evaluation should be focused on decompression sickness and need for hyperbaric oxygen treatment which may prevent permanent damage to inner ear. Effort must be made to exclude perilymph fistula before recompression treatment. However, that is not always possible and divers with a fistula sometimes get treated but there is no indication so far that it is deleterious if necessary precautions are taken. If there is no improvement on recompression or if there is worsening of symptoms, the treatment should be aborted and perilymph fistula considered.

Guenzani and co-authors reported case histories of nine cases of inner ear decompression sickness (IEDCS) in recreational technical divers who were identified through an online questionnaire. The most common leading symptom in IEDCS was vertigo, reflecting affliction of vestibular part of inner ear. The deafness which dominates in IEBt was seen in only three cases reported in this paper. IEDCS occurred in isolation (4 cases) and with other DCS manifestations (5 cases). The symptoms occur during ascent or soon after. IEDCS occurs more often than IEBt and due to growing participation in technical diving we may see it even more often in the future.

Presentation of these three papers in the same volume, seem like a good opportunity to re-fresh our knowledge about inner ear injuries in diving. Early recognition and prompt treatment are important to reduce the risk of permanent damage to hearing and orientation in space.

References

  1. Kitajima N, Sugita-Kitajima A, Kitajima S. Quantitative analysis of inner ear barotrauma using a Eustachian tube function analyzer. Diving Hyperb Med. 2016;46(2):76-81.
  2. Morvan J-B, et al. Perilymphatic fistula after underwater diving: a series of 11 cases. Diving and Hyperbaric Medicine. 2016;46(2):72-75.
  3. Guenzani S, et al. Inner ear decompression sickness in nine trimix recreational divers. Diving and Hyperbaric Medicine. 2016;46(2):111-116.
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