Asthma & Scuba Diving

What is Asthma?

Asthma is a long-term disease which can be controlled with proper treatment. People with asthma have episodes of shortness of breath which may be brought on or made worse by certain trigger factors. Salt water, cold exposure and exercise are often triggers.

How do the lungs work?

Every breath you take draws air through your trachea (windpipe) and bronchial tubes into the lungs. In the lungs there are small air sacs called alveoli. It is from here the air passes into the blood stream. At the same time, carbon dioxide produced in the tissues of the body moves from the blood stream into the air sacs and out of the bronchial tubes.

During asthma, inflammation causes narrowing of the airways, making them “twitchy” and very sensitive to environmental changes. During asthma, breathing becomes harder even at rest. There may be a cough, wheezing and chest tightness. The severity of these symptoms are different in everyone. In severe causes these symptoms may require urgent medical attention.

WHAT IS SCUBA?

SCUBA = Self Contained Underwater Breathing Apparatus

It was developed by Jacques Cousteau making the world of underwater exploration more accessible. In the last 20 years there has been a tremendous increase in the use of scuba equipment for recreational purposes. Opportunities abound for all to enjoy the beauty of the water.

What are the dangers?

As with any sport there are risks associated with scuba diving. The chance of dying while scuba diving is 40 times higher than when playing football or water skiing. Many of the risks are to do with pressure effects on the body. A diver breathes air at a pressure the same as that of the depth of water in which the diver is swimming. Pressure increases rapidly under water, and at 10 metres (33 feet) depth, pressure is double that at the surface.

If the diver inhales from a scuba cylinder at 10 metres depth then comes to the surface, the air in the chest expands as the pressure falls. The expanding air needs to escape, usually through the mouth or nose. If any air passages become closed (as occurs in asthma) the expanding air cannot escape and may cause the lung to burst. The air form the bust lung either escapes into the chest cavity causing pain and possibly death, or into the blood vessels which carry the air bubble (air embolism) to the heart and brain. This can be fatal. This lung injury is called barotrauma.

Diving gas is dry and is released through a small valve, causing a cooling effect. Thus a diver inhales a cold and dry air mixture which is potentially dangerous for asthmatics as it may provoke an episode of asthma.

Heavy physical exercise such as swimming against a current with a heavy tank on the back can produce breathlessness and even exercise induced asthma.

Accidental inhalation of salt and fresh water can produce coughing and a fine mist of water which can lead airways to narrow by direct airway irritation.

The general stress and anxiety of diving may add to the situation, setting the scene for a very serious attack of asthma.

Picture the scene for a person with asthma who develops it under water. Using a reliever puffer is obviously out of the question. When the diver tries to return to the surface, there may be some areas of the lung which are blocked off due to closure of asthmatic airways, and the expanding air in the se areas will no longer have anywhere to escape. The person with asthma is thus at much greater risk of barotrauma. If they do make it to the surface without problems when have to wait for the boat to get them, because they are in the waves it is easy to inhale salt water and this causes further narrowing of the airways. It is easy for asthmatics to panic at this time further aggravating the airway narrowing, and swallowing water sometimes leads to drowning on the surface. Any degree of airway narrowing may limit exercise adding to the risk if heavy exercise is needed.

Are people with asthma allowed to dive?

People with asthma are especially at risk when the trigger factors are present while diving. These risks are so well known that a medical certificate is required prior to doing a diving course. If there has been a history of asthma or use of inhalers, then a hypertonic saline challenge is useful to assess the degree of irritability of the airways and thus better assess the risk involved in diving.

Many people are not aware of the risks associated with diving. It is essential that every asthmatic is able to make informed decisions about diving as this decision will also affect other family members and any diving buddies.

Does this mean a person with asthma can never dive?

Not always. Although the majority of people with asthma are troubled by asthma at least sometimes throughout their lives, some really do appear to grow out of it; and for them, scuba diving may be no more risky than for the general population. Most diving medical experts agree that if a person has no symptoms or signs whatsoever of asthma for at least five years and has not required anti-asthma medication for this period, and has had a normal diving medical examination including breathing tests, then they should be allowed to dive. People with more recent symptoms should have a hypertonic saline challenge test to determine if they are at high, medium or low risk when diving. These people who wish to dive should discuss their decision with a doctor training in Diving Medicine.

Can adults with childhood asthma be sure that asthma will not recur during diving?

Although one can never be 100% sure that asthma will not recur, it is possible to undergo a hypertonic saline challenge test. If this test has a positive result (airways narrowing is induced) then the person is still susceptible to an acute onset of asthma while underwater, and it is recommended that they should not dive. If the test is negative then there is additional reassurance that asthma is unlikely to develop while diving.

The Statistics

• 5% of New Zealand’s adult population have asthma
• 7000 do a dive course every year
• Up to 17 people die every year from diving, and around 10% of these will be directly from asthma
• 120 people need recompression therapy every year

Is snorkel diving also dangerous for people with asthma?

Snorkel diving holds less risk for people with asthma than scuba diving. The main reason is that snorkelers do not take air in while at depth, and thus there is less risk of bursting the lungs during accent. Common sense dictates however that one’s asthma should be stable and controlled as accidental aspiration of water and exercise associated with swimming against a current can also lead to asthma. Some of the best underwater videos and films have been made by divers using a snorkel, goggles and a hand-held camera.