Listen to your ears
WHILE NON-DIVERS TEND to exaggerate the threat from sharks, divers obsess about avoiding decompression illness – even though it is middle-ear barotrauma that is the most common diving injury.
Ear problems may also contribute to a large proportion of diving incidents, including some fatalities. Awareness of how our ears work might make diving safer and more enjoyable.
THE ANATOMY OF THE EAR
Visualise three compartments: the outer, middle and inner ear. Working in from the auricle (pinna) – the visible part – the ear canal extends about 24mm into the head of the average adult.
The outer portion contains the glands that produce earwax (cerumen). The ear canal stops at the tympanic membrane, or eardrum.
The middle ear is an air-filled space that contains the ossicles – three tiny bones called the hammer (malleus), anvil (incus) and stirrup (stapes) – that amplify sound.
Separating middle from inner ear are the round and oval windows. At only two cells thick, these are two of the thinnest and most delicate membranes in the human body.
The inner ear houses the cochlea for hearing and the vestibular system, which incorporates the semi-circular canals and provides our sense of balance and spatial orientation.
The Eustachian tubes connect each middle ear to the back of the nose (nasopharynx). The opening to the tube starts at the Eustachian cushion and is located above the soft palate, the soft tissue at the back of the roof of the mouth. This is the bit mistakenly blamed for making that annoying rattling noise when we snore.
These tubes are normally closed to prevent bacteria invading the middle ear, but they open naturally when we swallow or yawn.
This allows air to pass between the back of the nose and the middle ear to ensure that the pressure on both sides of the eardrum is “equalised” automatically.
Apparently people hear a faint pop or click when this happens – I rarely do.
However, scuba-diving involves bigger and faster pressure changes than we normally experience, so the diver must learn to open these tubes on demand.
WHY WE MUST EQUALISE
The middle ear is a dead-air space, separated from the other compartments by thin membranes. The eardrum separates the outer and middle ear; the oval and round windows sit between the middle and inner ear.
The only connection between the middle ear and ambient pressure is via the Eustachian tubes. If these are closed then, according to Boyle’s Law, the volume of air in the middle ear will shrink in response to an increase in pressure as we descend.
Failure to equalise means that these membranes will bulge inwards. This stretches the nerve-endings in the eardrum, perceived as pain.
If no effort has been made to equalise before the diver is 2m down, it becomes virtually impossible to do so because the higher pressure in the back of the nose clamps the tubes shut.
This is why it’s so important to start equalising early and keep repeating it every half-metre or so – to prevent a pressure difference developing equivalent to a depth of 2m (or 20% of atmospheric pressure).
To continue to descend without equalising will cause injury. With luck, you would experience a middle-ear barotrauma. Less lucky and you would burst an eardrum – or two.
This, middle-ear barotrauma, is the most common diving injury, caused by failure to equalise. Blood and mucus fill the middle ear and this equalises the pressure on the eardrums.
Pain is replaced by a feeling of fullness in the ears that will typically persist for a week until the fluid drains away. Hearing is muffled.
The symptoms usually develop immediately but there can be a delay of a day or more. An ear problem immediately following a dive outing suggests barotrauma rather than otitis media (middle-ear infection).
Diving must cease until the symptoms clear up and flying should be postponed if possible. Decongestants can speed up recovery, but if symptoms persist for more than a week you need to be assessed by an otolaryngologist or ENT (ear, nose and throat) specialist.
This can occur just 2m below the surface but the exact depth varies – partly because we’re all built differently.
It doesn’t always result in pain or the discharge of blood or fluid from the ear. Hearing loss and tinnitus (a ringing or roaring sound) are not always present either but when water floods into the middle ear, the sudden sensation of cold against the balance mechanism in the inner ear may induce vertigo.
This is more likely if only one eardrum ruptures, though the sensation will subside as water in the middle ear warms up.
If you suspect a ruptured eardrum, you should cease diving to avoid the risk of vertigo and ear infection. Don’t put any liquids in your ear, either.
This is often confused with acrophobia or fear of heights. Normally the vestibular systems in both ears will detect the same pressure (or temperature). Your brain interprets
any difference in what is detected as movement and this induces vertigo, making you feel extremely drunk, with the same spinning sensation and strong urge to vomit.
The disorientation is made worse if there are no visual cues, as might happen out in the blue or in low visibility, when you can’t see the seabed or the surface.
If vertigo fails to subside, the advice is to ensure that there is some water in your mask to indicate which way is down, and follow your bubbles, slowly, to the surface.
Struggling to equalise on a descent into a very murky British quarry, I experienced severe vertigo.
A plug of earwax had caused one ear canal to fill with cold water more slowly than the other. It took willpower to suppress my anxiety, despite correctly guessing the probable cause.
In a paper published in 1995, sports researcher William Morgan suggests that more than half of scuba divers have experienced potentially life-threatening panic attacks, and I suspect vertigo induced by difficulties equalising might account for some of these. I continued with the dive, but vertigo is generally your cue to abort.
HOW TO EQUALISE
The Valsalva Manoeuvre, whereby you pinch your nostrils and try to blow through your blocked nose, is the method most new divers learn.
If a diver fails to equalise early or often enough, the higher pressure in the nose can force the soft tissues of the Eustachian cushion together, closing the ends of the tubes.
Forcing air against these soft tissues just locks them shut. Blowing too hard for longer than, say, five seconds, can rupture the oval or round windows, resulting in inner-ear barotrauma.
This can lead to vertigo, vomiting, and loud tinnitus. It may also lead to hearing loss if perilymph fluid drains from the cochlea into the middle ear.
This is a medical emergency, and the injured diver needs to be assessed by a diving medic, because barotrauma and DCI damage to the inner ear have similar symptoms, but the treatments are very different – recompression alleviates DCI but aggravates barotrauma.
Because of the risk of injury associated with Valsalva, the following alternative methods are recommended. All but the last one involve pinching or otherwise closing your nose.
With the Toynbee Manoeuvre, you simply swallow; this pulls open your Eustachian tubes while your tongue compresses air against them.
However, some divers have difficulty swallowing, as the mouth naturally becomes dry on open-circuit diving.
For these divers the Frenzel Manoeuvre might work. Close the back of your throat as if straining to lift a weight before making the sound of the letter K. Like the Toynbee Manoeuvre, this forces the back of your tongue upward, compressing air against the openings of your tubes.
Some techniques combine the Valsalva Manoeuvre but probably have the merit of reducing the pressures involved in using Valsalva on its own.
The Lowry Technique is a combination of Valsalva and Toynbee – you blow and swallow at the same time.
The Edmonds Technique is the Valsalva combined with tensing the soft palate and throat muscles, while pushing the jaw forward and down as if starting to yawn. This is very similar to another technique favoured by the French – the Voluntary Tubal Opening or béance tubiare volontaire (BTV).
Developed by George Delonca, it was adopted by the French Navy in the 1950s. If you have the art of stifling a yawn while in polite company, you might have the skill to join the exclusive band of divers who can perfect this technique.
BEFORE THE DIVE
Divers who have difficulty equalising should try mastering several techniques, practising in front of the mirror if necessary to watch your throat muscles.
Mucus can block your Eustachian tubes and, because dairy products can cause a fourfold increase in mucus production, avoid drinking milk. Abstain from tobacco and alcohol for the same reason.
Allergies or other allergic reactions may produce swelling of the mucus membranes, making equalisation more difficult. These are quite common and not limited to hay fever, which alone afflicts a quarter of the population.
People exposed to cigarette smoke as children are more likely to suffer hay fever and asthma. Antihistamines can help alleviate an allergic reaction, while vortico-steroids reduce inflammation.
Some divers use these over-the-counter drugs as a precaution after self-diagnosing an allergy but perhaps it’s better to get tested for allergies. With an overview of your medical history, your GP may then be able to advise on which medicines might work best for you. Otherwise it’s down to trial and error.
Experienced divers from my club start using a vortico-steroid such as Beconase a week before a dive trip, and while away also use a non-drowsy antihistamine. Many divers also use topical decongestants such as Sudafed.
Sudafed’s active ingredient, pseudoephedrine, is a vaso-constrictor – narrowing blood vessels in the nose dries up the mucus. The drug’s target is the nasopharynx at the very back of the nose, so it is recommended that you lie on your back with your nostrils pointing to the ceiling before putting 2-5 drops into each nostril and lying there for three minutes or so.
However, using a decongestant for 5-7 days in succession carries the risk of rebound congestion. Besides, DAN (Divers Alert Network) advises that divers seek advice from an ENT specialist if they cannot equalise without the help of a decongestant. Using drugs on a dive carries some risk because their performance has not been trialled at the pressures associated with diving, and there may be unforeseen side-effects.
Do not assume that a drug is safe for you just because your buddy uses it without problems – we’re all different.
Some divers advocate nasal irrigation as a drug-free alternative. This clears out mucus from around their Eustachian tubes. Solutions can be bought but are easy to prepare. Using cold tap water would irritate the mucus membranes – the opposite of the desired effect – so boil some water. Allow it to cool to lukewarm and add at least 9gm of table salt for every litre of water so that it is at least isotonic and matches or exceeds the salt concentration of the blood.
Add half a teaspoon of baking soda to match the pH of the body, and snort the water through the nostrils.
A simple alternative is to let gravity do the work by pouring the saline into one nostril and allowing it to run out through the other, keeping your mouth open to breathe.
IF PROBLEMS PERSIST
If you still have difficulty equalising, consider using an Otovent balloon, which you inflate via one of your nostrils or allow to deflate into one of your nostrils while swallowing some water.
Failing that, seek advice from an ENT specialist. Perhaps childhood ear infections have scarred the Eustachian tubes or left them partially blocked.
If you have ever broken your nose or otherwise have a deviated septum (that is, the bit that separates your nostrils isn’t quite central), one ear may clear before the other – a recipe for vertigo.
Several hours before your dive, blow your nose. Begin gently equalising your ears every few minutes. This would also be the time to use a decongestant. Some divers swear by chewing gum between dives.
The majority suggest that “pre-pressurising” at the surface helps them get down the first metre or two of descent when they are task-loaded – dumping air from their BC, clearing their mask etc.
Most authorities recommend equalising every half-metre of descent. A fairly conservative descent rate of 20m per minute equates to an equalisation every two seconds.
Many divers descend much faster and should be equalising constantly.
Studies have shown that the Valsalva Manoeuvre requires 50% more force when the diver is head-down than when head-up, so descend feet-first so that air can rise up your Eustachian tubes – besides, being head-down risks mucus draining into and blocking your tubes.
Looking up on descent extends your neck and tends to open the tubes.
This is a bit tricky when your impatient buddy is below and you need to look down to communicate, so warning of a potential problem during buddy-checks might be helpful.
Use a shotline, if available, to slow your descent rate. If you experience pain, ascend until it stops and try equalising again.
Like most divers, I don’t have to equalise on ascent – my ears pop naturally. Reverse squeeze or reverse ear happens when you can’t equalise on ascent and the membranes enclosing the middle ear bulge outwards.
Some claim that diving with a cold and relying on decongestants that have worn off during the dive risks reverse ear.
Try equalising, and ascend as slowly as your air supply allows. If the reverse block is caused by a tight hood or a plug of earwax that has been pushed further into your ear canal on descent, you have another dead-air space – this time outside your eardrum.
If the surrounding tissues fill the canal with blood and fluid you have an outer-ear barotrauma, with similar symptoms to middle-ear barotrauma.
Diving doctor Edward Thalmann cured the problem of ear infections in US Navy saturation divers in the 1970s, and the protocol he developed can be applied to recreational diving.
The cells lining the ear canal swell when we are under water for long periods (such as during a dive trip), which pulls the cells apart, inviting bacteria that normally live on the surface of your ear canal to move under your skin, where they can multiply.
If your ear canal itches and becomes sore and inflamed, you have the classic symptoms of otitis externa or swimmer’s ear. Thalmann recommends a solution that is no longer commercially available. Auro-Dri or Swim-Ear may be suitable substitutes, but the trick is that the solution must remain in each canal for at least five minutes. This is a preventative measure – it can’t cure an infection.
To prevent earwax build-up, Thalmann recommends gently flushing the ear canal when showering by cupping your hand next to your ear so that water overflows into the canal.
Cameron Gillespie, another diving doc, strongly cautions against using cotton buds, which are liable to ram any plug of earwax further down the ear canal and may damage the eardrum.
Besides, cotton may get left behind in the ear canal and harbour bacteria. Instead he suggests occasional washing using a bulb syringe filled with warm soapy water and a 3% hydrogen peroxide solution.
On a diving trip, he advises a 50:50 blend of white vinegar and surgical spirit (or rubbing alcohol) at the end of each day of diving.
The acid makes your ear a more hostile environment for bacteria. You could mix this into a 10ml bottle with a dropper pipette in the lid. Pack it in your hold luggage on an overseas trip or source it at your destination.
Ear injuries are not inherently life-threatening but vertigo can be, especially if accompanied by vomiting under water. Reduce the risk of injury or vertigo by keeping your ears clean and practising ear-clearing techniques.
Never dive with a cold or when you cannot clear your ears. Few things are more frustrating in diving than having “slow ears”, but never rush a descent – and ignore ear-pain at your peril.
You can find more information at www.scuba-doc.com