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Diving Doctor – Dr Oliver talks seasickness in the March issue of Sportdiver

Seasickness

Diving from a liveaboard off Pemba, The Green Island, is apparently amazing. However I spent 3 days in bed, feeling very green. Kitting up just once was hell. While some get benefit from being underwater and rush to get in, even the small wave motion underwater was enough to make me feel like vomiting. Everyone who has hearing and a functioning vestibular system is susceptible to motion sickness. Numbers are roughly split into 1/3 that are highly susceptible, 1/3 suffer in rough conditions and 1/3 only in extreme conditions. The books always discuss an imbalance between the 3 sensory modalities for spatial awareness. These include proprioception, which is joint position sense, vision and the vestibular system, which is the sense of movement and balance. However there is also clearly a psychological input. Once begun, seasickness is more difficult to get rid of, but it is also catching and distraction may help reduce it. Hence remedies tend to work better if in place before the motion and the thoughts get out of hand. If I was away for longer, I may have managed some diving as often sea sickness gets better after 2-3 days at sea.

Hyoscine, meclizine and cinnarizine (stugeron, TM) work by reducing vestibular inputs and can be sedating. Most people do not have any serious problems with these medications; however there is the possibility of side effects, drug interactions and effects on pre-existing medical conditions. Therefore these medications should be discussed with a doctor before diving. Carl Edmonds recommends the trial use of any medication that cause drowsiness to ensure no untoward reactions and to dive shallower than 18m to avoid narcosis. For this reason alcohol must also be avoided. The most common side effects of seasickness medications are:

        Drowsiness

        Headache

        Dizziness

        Agitation

        Poor concentration

        Fast heart rate

        Dry mouth

        Blurred vision

        Difficulty passing urine

        Stomach and gut upsets

Closing your eyes, or looking at the horizon, reduces the conflict between balance and visual inputs, which is worsened by going below deck. Lying down along the boat’s centre line, toward the stern and minimizing head movements, reduces proprioceptive input by incurring the least complex movements. However it’s also the best place for a smelly engine and for navigating the boat. So may incur the wrath of those still capable of useful function and compound the demoralising effects of seasickness.

An approach that involves different mechanisms to prevent sea sickness may work well. For example, chewing fresh ginger, good hydration and acupressure are safe with cinnarizine. The acupuncture point known as Pericardium 6, traditionally has been used to help relieve nausea. It is located on the inside of the wrist, about the length of 2 fingernails up the arm from the centre of the wrist crease. Many travel stores sell wrist bands with built in buttons designed to apply acupressure to this point, which has no significant side effects.

The following nutritional tips may help reduce symptoms, improve overall health and should be considered before taking medications:

        Avoid spicy, greasy, or fatty meals, alcohol and hangovers

        Don’t overeat

        Drink plenty of water.

        Dry crackers and carbonated drink (such as ginger ale) may help

Peppermint tea, black horehound, biofeedback, cognitive behavioural therapy, hypnosis and breathing exercises have also worked for some people. Probably through relaxation. However no treatments are known to be effective in all cases and if symptoms do not resolve soon after arriving on dry land then it’s time to phone the doctor.

Finally, dehydration is worth a special mention as it is common, associated with sun and alcohol, and can predispose sufferers to sea sickness, vomiting and more dehydration. The outflow from the stomach (pyloric sphincter) may also stay constricted and stop oral fluids and drugs from reaching their site of action. Hence intravenous, intramuscular or rectal routes may be required to correct the imbalance of electrolytes in the blood and the increased risk of decompression illness. Dehydration is definitely one predisposing factor to avoid.

Questions

1) I recently went on a day trip to complete my Advanced Open Water course with the Deep dive. On the way to the site I suffered with seasickness and one of the other divers advised that I didn’t do the deep dive as I was more likely to get bent on the dive because I was seasick. I did complete the dive in the end and had no decompression sickness symptoms afterwards but wanted to know if this was really true and whether I was taking a risk doing the dive?

There is no reason why seasickness would directly cause decompression sickness. However dehydration and poor concentration due to sedative medications, rushed kitting up or feeling unwell can contribute to an increased risk. So if you are a seasickness sufferer, then you should be aware of these problems and minimise the effects before diving.

2) I suffer occasionally from seasickness and have seen other divers use all sorts of patches and natural remedies. I don’t like to take medicines so I’m keen to know whether these more natural methods really work?

Patches for seasickness are usually hyoscine, which avoids the oral route and generally provides a low dose for longer than tablets. There is no guaranteed cure for seasickness, so I cannot say what will work for you, but it is worth trying a range of remedies. Examples of the more natural remedies with the best evidence are probably ginger and acupuncture. A review of the use of ginger in American Family Physician journal in 2007, described 4 trials of its use in motion sickness. 2 trials showed there was benefit and 2 did not. For acupuncture, there does not seem to be any serious reviews for its use in motion sickness. However there are many similarities with post operative nausea and vomiting, for which there is some significant trials and reviews that suggest there may be some benefit.

3) Do I need to take sea sickness tablets before I go on the boat or can I take them if I start to feel sick?

Sea sickness tablets are for prevention, not cure. Hence are best taken before leaving the land in order to give the medications time to work. For precise timings, read the information sheet that comes with all over the counter medications. Different drugs will take different times to work, but at least an hour will be required before significant benefit and probably more for full benefit. Once you feel sick, medications are much less likely to work, if at all. So take them early and read the information sheet.

4) Should I eat something before taking sea sickness tablets?

Seasickness tablets do not have to be taken with food but can be. If you are likely to feel sea sick, then eating small amounts before travelling may be a good idea and good hydration prior to travelling is a must.

5) Can I take sea sickness tablets if I’m pregnant?

Hyoscine, meclizine and cinnarizine (stugeron TM) are not advisable in pregnancy. As with most medications, there is little research into the effects on pregnancy. However, if you have taken seasickness tablets while pregnant, then speak to your doctor. On balance, long term effects are very unlikely. A few grams of ginger and wrist bands are safe.

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