Written by DAN Staff

Student divers often have difficulty clearing their ears. While most equalization problems can be solved with more practice, it’s important to recognize that certain anatomical and physiological differences can make equalizing more difficult.

Injuries associated with the middle ear and Eustachian tubes represent the single largest category of dive injuries — a full 38 percent of all injuries in the 2018 DAN Annual Diving Report (and 27 percent more than all cases of DCS). Brush up on your knowledge of Eustachian tube dysfunction and keep your students listening to your post-dive debriefs rather than heading to get medical help.

Eustachian tube (ET) dysfunction has been on the radar of dive physicians for a long time, but until recently, has been difficult to quantify. Using replicable physical measurements and impedance tests, a group of researchers associated with the Undersea and Hyperbaric Medical Society have been able to correlate ET function with incidents of inner-ear barotrauma (IEBT).

Research

Kitajima and colleagues in 2016 used a novel approach combined with some simple metrics to measure the pressure required to open the ET, the maximum volume of air in the middle ear and the speed at which equalization occurred. As a baseline, it’s expected that it should take 200 – 650 dekapascals (daPa) to open a healthy ET. This is a pressure gradient equal to a depth change of 20 – 66 centimetres/8 -26 inches. The research paper categorizes ET function in the divers studied as one of three categories:

    1. Patulous (open, or requiring less than 200 daPa to open)
    2. Normal (collapsed but requiring less than 650 daPa to open, and filling or emptying instantaneously)
    3. Stenotic (collapsed and requiring up to 1200 daPa to open, or filling and emptying very slowly)

From top to bottom these represent good, moderate and poor ET function. Comparing these measurements to the subject diver’s history of IEBT they found the following:

    1. In healthy divers without a history of IEBT, 30 percent equalized slowly, but the pressure required to do so was within the normal range.
    2. Among divers with IEBT, most had notably stenotic ET, requiring either significant time to empty or fill or requiring increased pressure to open.
    3. Divers with IEBT and a perilymph fistula (a tear in the round or oval window of the ear often caused by forceful equalization) had significantly worse ET dysfunction. It’s suspected that the pressure caused by forceful equalization may have been the cause of IEBT in these divers. The paper presents 11 cases of IEBT-caused perilymph fistula.
    4. Some divers with IEBT had normal ET function at the time of testing.

Take-Away

There are measurable anatomical or physiological differences that can make equalization much more difficult for some students. Divers with ears of all types can avoid injuries with slow and careful equalization, however, divers with repetitive issues may wish to see an ENT (ear, nose and throat) physician.

There is no definitive treatment for poor Eustachian tube function, but the knowledge that equalization may take longer and should be done more gently and frequently can go a long way toward preventing injury.

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