Seasickness

"The best cure for seasickness is to sit under a tree." ... Spike Milligan

Here's a table of useful anti-motion-sickness drugs. Below the table is an extended discussion by Chuck Oman, PhD, Director of the Man Vehicle Laboratory at MIT where his research includes virtual reality experiments on the Space Shuttle. He is an expert on motion sickness and frequent speaker at US SAILING Safety At Sea Seminars. A lifelong sailor, he has extensive cruising and racing experience, including six Newport to Bermuda races.

Sea sickness is one of the more common medical hazards encountered by people who sail offshore. Less experienced sailors, who seem to be most prune to it, often incorrectly assume that seasickness is predominantly psychological in origin.

In this article, we describe techniques that you can use to reduce the sickness stimulus. Effective anti-motion sickness drugs are readily available also, even over the counter. But to use these weapons wisely, you must learn also to recognize and react to your own earliest symptoms.

Susceptibility

Nine out of ten people say they have experienced some form of motion sickness at some point in their lives. In fact, virtually everyone who has normal inner ear balance function can be made motion sick. Susceptibility is highest in childhood and declines somewhat with age and experience in motion environments.

Women are more likely to admit they are sick, but recent evidence suggests that men and women are probably about equally susceptible when previous motion experience is factored out. Many experienced offshore sailors consider themselves relatively unsusceptible to seasickness. But if you sail offshore enough, chances are good that you will eventually encounter sea conditions that will bother your stomach.

What Causes Seasickness

The origin of motion sickness is now thought to have relatively little to do with one's stomach. Most researchers now agree that motion sickness occurs when portions of the brain responsible for maintaining your balance receive signals from the eyes, inner ear, muscles and joints in inconsistent, unexpected combinations for a prolonged period of time.

The best hypothesis is that over a lifetime of living ashore, the "balance brain" has learned to predict exactly what sensory signals it should receive from moment to moment each time an active body movement is made, particularly from the vestibular organs in the inner ear. The balance brain probably computes a "sensory conflict" signal -- the difference between actual and anticipated sensory information received. "Sensory conflict" signals represent the unanticipated portion of sensory information, and are thought to trigger corrective postural reflexes and help stabilize gaze. In everyday life ashore, sensory cues arrive in consistent, anticipated patterns and sensory conflict signals are small. However, when you go out on the ocean, the motion of the boat continuously disturbs your posture, greatly increasing the level of conflict signals.

According to the "sensory conflict" theory for motion sickness, when the conflict levels increase and are sustained, signals in the "balance brain" somehow spill over to the "emetic brain" and symptoms may start to appear. Fortunately, the "balance brain" also has the capacity to adapt to the new moving environment. It learns to anticipate and compensate for the boat's next motion and, when this happens, sensory conflict signals disappear. No wonder sailors have traditionally called the process of recovering from mal de mer as "getting your sea legs."

Understanding the role of postural anticipation in causing and curing motion sickness is of great practical importance, The sooner you learn to compensate subconsciously for your boat's motion, the better. Several methods for staying in tune with your boat's motion are described later in this article, including "wave riding," a way of actively sitting on deck.

Vision often plays a critical role in causing and curing motion sickness. While on deck, the motion you sense with your inner-ear organs and muscle and joint senses is confirmed by the tilt of the horizon and the motion of objects in your peripheral vision. If the motion isn't too severe, you feel fine, or only a little queasy. However, when you go below deck to work, you begin to feel ill more quickly. The normal correlation between peripheral vision and inner ear motion cues that existed on deck is altered down below. Your eyes see only your motion relative to the cabin interior, while your inner ear senses the motion of the boat in the waves, in addition to your own movement. The result is increased sensory conflict.

If you go topside again, sensory conflict will decrease and likely so will your symptoms, provided you've not let them become too advanced. Knowing that you reduce the stimulus when you have a broad view of the horizon in your peripheral vision is important, because often you can use deliberate horizon viewing as another means of controlling your symptoms.

Emetic Linkage

When you are first exposed to a conflict stimulus. the linkage between the balance and emetic centers initially takes many minutes to become activated. Typically at first you will not be aware that you are becoming ill. If you act quickly when your own characteristic first symptoms do appear (see below), you often can eliminate them by reducing the conflict stimulus.

Anti-motion sickness drugs are thought to act either by partially blocking the linkage, or by depressing the "emetic brain" centers directly. Unfortunately, no drug has yet been discovered that completely prevents motion sickness in most people. Drugs simply raise your threshold for sickness and are generally more effective in preventing symptoms than in reversing them after sickness is well established. Hence, drugs are best taken in advance or at the very first sign of symptoms.

Prevention And Treatment

What can you do to prevent or control seasickness when out on the ocean?

Recognize: The key to effective prevention is to recognize and react to your earliest symptoms. Each person's pattern of symptom onset is somewhat different, but it is usually repeatable. Generally the first symptoms are yawning and drowsiness, then abnormal fatigue and lethargy, but if you already are tired from standing watch these symptoms can go unrecognized. For many people, the first obvious symptoms are stomach awareness (which eventually turns to nausea) and slight sweating.

As symptoms advance, stomach awareness turns to nausea, the face becomes pale. particularly around the nose and mouth, and hands and face become cold and clammy. Belching, salivation and flatulence are common. Concentration on mental tasks becomes difficult. Eventually nausea comes in waves. and increases in uncontrolled crescendo leading almost inevitably to vomiting. Subsequent attacks of vomiting typically develop with less warning than the first.

React: As soon as you notice you have symptoms, do something about it! Take an anti-motion sickness medication, if you haven't done so already. Go on deck to eliminate visual conflict, and stay amidships or aft where the total motion stimulus due to pitching and rolling is less severe. It's a technique called horizon viewing. Station yourself where you have a good broad view of the Earth-sky boundary in your peripheral vision, preferably where you can see oncoming waves and more easily anticipate the motion. You needn't try to stare steadfastly at the horizon . It is fine to look around. If you're an experienced helmsman, take the wheel and steer by reference to oncoming waves, the horizon, clouds, and distant sails.

Look Out: Avoid navigating, staring at the compass. reading, cooking, or similar visual tasks whenever you feel sick. Your balance brain is automatically trying to stabilize your eyes with respect to the horizon, so any task that requires you to focus for long periods at objects on board is potentially provocative.

Ride the Waves: Don't sit or lie inert in the cockpit, leaning against the cabin or coaming, passively letting the motion toss you around, Postural anticipation of the boat's motion is the natural cure for seasickness. Use a method called wave riding: Sit upright, let your trunk and neck muscles keep your head and upper body balanced over your hips as the boat moves. Once you get the rhythm, it is far less tiring than fighting to hang on. If you feel well enough, stand up, walk around, and develop your sea legs while you find some work to do.

Communicate: Let the skipper know that you have symptoms. Don't be embarrassed; experienced skippers know seasickness happens because most get seasick sometimes themselves. They know that even a small course change can change the amplitude and frequency of the boat's motion in the waves, often with miraculous results.

Go on Deck: To avoid visual conflicts, minimize the time you spend below, particularly if you are beginning to feel queasy. When you awaken for your watch, dress quickly and get on deck. You may feel fine when you first wake up, but symptoms may appear once your balance brain is put back to work. Wear clothing that is absorbent, easily ventilated and quickly removed (e.g., zipper front instead of a pullover foul weather top). Err on the side of overdressing, It is easier to remove excess clothing on deck and hand it below than to go below yourself while sick. If necessary eat on deck.

When you go off watch, change and get into your bunk promptly, You won't adapt to the motion lying down, but you will be much less susceptible. Choose a narrow berth or arrange soft duffels and sail bags around you so you are wedged in and can relax completely. If you have to hang on while in your berth, your subconscious balance brain won't easily go "off watch." Close your eyes and go to sleep. Sleeping seems largely to turn off the balance brain, allowing the emetic brain to recover.

Pace Yourself: If your duties require you to work below, remember that you often can keep your symptoms under control if you pace yourself properly with intervals of horizon viewing. Take a break every few minutes, go on deck, or stand in a hatch or look out a large cabin window. Peeking out a porthole won't work, the idea being to obtain a wide view of the horizon in your peripheral vision. Remember that when symptoms are minimal, the delay between what you are doing and how you are feeling can be several minutes. Be alert to changes in your symptoms. With experience, you'll usually be able to keep your nausea below the point of no return.

Think Ahead: Seasickness is the curse of cooks and navigators. Advance preparations and technology can really help. Knowing exactly where your food is stowed, moving items in calm weather from deep stowage up forward to a handy spot aft near the galley, and "cooking ahead" using refrigeration have saved many a sea cook's stomach. Prolonged reading and writing inherent in offshore navigation can be quite provocative. Consider switching to a calculator rather than using tables when working celestial sights in a seaway.

Avoid Alcohol: Drink alcohol only in moderation. Alcohol has a direct effect on your vestibular system and depending on the degree of consumption you may he made to feel dizzy anytime you or the boat moves, especially with overindulgence. If you're hung over on the morning of departure from the previous evening's social events, chances are good that you will donate your breakfast to Neptune.

Eat Moderately: There isn't much strong scientific evidence indicating that susceptibility to seasickness is influenced by eating or avoiding certain foods, even though this idea is mentioned frequently in older textbooks. Feel free to eat moderate amounts of whatever foods you find appealing. Diet becomes important only if vomiting occurs.

Replace Nutrients: Sometimes a case of seasickness is limited to a single episode of vomiting. However, particularly in heavy weather, repeated attacks of vomiting and retching ("dry heaves") are common. Vomiting brings temporary relief from nausea, but after several episodes, weakness. drowsiness and apathy typically result. Sufferers usually are able to respond physically to real emergencies for a day or so. However. if you vomit repeatedly and don't eat because you feel nauseous. eventually you will "hit the wall" and become weak, confused and eventually incapacitated. Your breath will smell like acetone. To prevent this, force yourself to eat and drink (broth, Saltines, and candy, for instance) frequently in small amounts. It won't all stay down, but your net loss of fluids, glucose, and electrolytes due to vomiting will he much reduced.

Observe Others: Watch leaders should be alert for weakness, extreme drowsiness, and confusion in those suffering from prolonged seasickness. Severely afflicted crew members are often reluctant to go below because they might feel worse and they don't want to leave the rest of their watch shorthanded. Instead, they linger on deck, sometimes even falling asleep at the leeward rail. Seasick crew members easily can fall or be washed overboard. Insist that they use harnesses. Don't permit them to remain on deck under storm conditions. They are more likely to be able to respond in a real emergency if you get them wedged in a berth down below, medicated, fed, and resting.

Have A Plan: When preparing for a trip, the skipper or "ship's doc" should develop a plan for management of seasickness cases in advance. Find out what anti-seasickness drugs each crewmember plans to use and keep them all in a dry place very handy to the deck, not in a medicine locker located in the lurching, smelly confines of the head. Make sure you know whether any crew members have preexisting medical conditions such as ulcers or diabetes, or require special medications. These people may develop additional problems if they suffer from severe seasickness. Work out a viable plan for treating them.

Before departure, review procedures for prevention and treatment with your entire crew, Designate a narrow sea berth aft for use by the afflicted and have a supply of emesis bags, disposable towels, easily opened juice or water bottles, and candy available in the bunk. Bags really are far superior to the traditional bucket. Airline bags are adequate, but even better are the inexpensive "sic-sacs" available at aviation stores. These are much easier to use in a motion environment even when lying down.

Consider The Raft: Be certain your life raft medical kit is well stocked with anti-motion sickness drugs. Rafts have a really jerky motion and the canopy on the raft — although it provides essential protection from the elements — deprives the occupants of outside visual references. Because of this, seasickness in rafts is common.

Medications: Anti-motion-sickness drugs are a very effective way of raising your threshold for seasickness and of hastening recovery if you do become sick. As shown in the table above, a wide variety of useful drugs is available. The problem is that many sailors are reluctant to use them, usually because of concerns about side effects (e.g., drowsiness and blurred vision). Also, all oral drugs require at least a half hour, usually more, to become effective. Many people try drugs but give up on them, simply because they failed to take them in time. Finding a drug that works for you is worthwhile. Before choosing or using any anti-motion sickness drug, consult with your own physician, someone who knows your medical history, who can prescribe the stronger drugs and suppositories and who can advise on the type and dosage you can take safely. Not all anti-motion sickness drugs are appropriate for use by children. Women who are, or might be, pregnant should avoid drugs entirely.

If you are relatively susceptible to seasickness, or haven't sailed offshore recently, prophylactic drug use is probably the best strategy. To find one with acceptable side effects, experiment with several different types ashore first, taking them on the same schedule you would use at sea. When choosing a drug, duration of action is an important consideration, because bad weather offshore can last for several days and you must take doses at regular intervals. Longer acting drugs -- such as meclizine, promethazine. cinnarizine or dimenhydrinate in time-release form -- thus have practical advantages.

One prescription drug of interest to sailors is an adhesive patch worn behind the ear, which continuously administers a dose of the drug scopolamine through the skin over a three-day period. The idea is to try to minimize the incidence of side effects by maintaining a relatively constant level of scopolamine in the blood. The patch has been sold in the United States as Transderm-Scop only by prescription, but it has been available without one in Bermuda and in many provinces in Canada.

NASA astronauts now generally avoid oral and transdermal premedication and rely on intramuscular injection of promethazine for treatment. The injections leave a painful sore spot and may make you very sleepy. But when combined with bed rest, injected promethazine can give fast and effective relief, and the dose is not lost if the person vomits again. Use of injectables may make good sense when sailing offshore, but you must have a person aboard who is properly qualified to prescribe and administer them. A more practical but slower-acting alternative is the rectal suppository. However, remember that suppositories, too, require a prescription (in the United States) and can become difficult to use unless stored in a cool place.

Biofeedback/Relaxation: Using biofeedback, progressive relaxation and/ or autogenic imagery, many people can learn to control volitionally, to a degree, their own heart rate, blood pressure, and skin temperature if they practice regularly. Because the emetic brain is closely coupled to centers controlling these functions, there is reason to hope that these same methods can he used actively to suppress symptoms of motion sickness, You may have heard that several NASA and Air Force psychologists have experimented with this approach, which avoids the side-effect problems associated with anti-motion-sickness drug use. Results have been encouraging, but the studies have been small-scale and have been done mostly by advocates. Despite 20 years of research, the approach has not been adopted for regular use by NASA or the U.S. military.

Finally... The moral of this story is that you can do a great deal to prevent and treat seasickness when you know its causes. Coupling of the balance brain to the emetic brain is a universal human response to any abnormal motion environment. Susceptibility only disappears when your balance brain learns to anticipate subconsciously the next wave. Drugs can be of real value until you adapt. So too can techniques such as wave riding and horizon viewing, provided you recognize and react to your earliest symptoms. If you do become severely sick. there are important things you can do to make the experience less unpleasant and to assure a prompt recovery. Over the long term, the best way to prevent seasickness, aside from staying ashore, happens to be the most enjoyable: Go sailing a lot.