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Air travel - health advice before you take off

Chief physician Steffen Lyduch, who specialises in aerospace medicine, outlines some basic advance precautions you can take if you are concerned about flying


Over the years, flying has developed into the safest form of transportation and the most popular, with more than one billion people travelling every year on aeroplanes. More and more passengers with chronic or latent (hidden) illnesses are also using this means of transport. However, airline companies are reporting increasing cases of in-flight illness, and a lot of work is now being put into informing travellers about preventative measures.

It was recently estimated that one case of in-flight illness will occur for every ten million Passenger Revenue Miles (PRM—one PRM being equivalent to one passenger being transported one mile), and that one flight diversion for medical emergency reasons will occur for every three billion PRM.

Let me emphasize from the start that flying is an extremely safe form of transport and safe also as regards the health. Only a very few people will be unable to tolerate the stresses the body is exposed to when flying. Even passengers with severe chronic illnesses can fly safely—they just need to take some basic advance precautions, which require a little extra planning. These passengers are advised to contact their General Practitioner for advice and information prior to flying.

Atmospheric pressure decreases with altitude. The higher we go, the thinner the air becomes, and already at an altitude of 12-14,000 feet, the air is so thin that there is not enough oxygen for humans to survive for a long period.

Most modern passenger aeroplanes fly at an altitude of 30-40,000 feet. To make high-altitude flight possible for humans, modern airliners are equipped with pressurised cabins. This means that even though the aeroplane is flying at 40,000 feet, a pressure equivalent to an air pressure of 6 – 8,000 feet altitude is maintained in the cabin. In other words: the air pressure outside the cabin is only ¼ atmosphere whilst the pressure inside the cabin is ¾ atmosphere and therefore contains enough oxygen for passengers to function normally. Cabin air pressure at this altitude therefore poses no risk to healthy people.

In-flight problems

The main problems are those caused in particular by the thinner air (lack of oxygen) and the expansion of the air (in the middle ear, sinuses and stomach). But the dry atmosphere, confined space, lack of activity, and low fluid intake can also cause symptoms of illness to appear during the flight.

Strobe effects, or ‘flicker', caused by the reflection of light from the aircraft’s propellers, or the reflection when flying through layers of cloud, can cause 'seizures' in some passengers who are predisposed to that.

Heart and lung diseases

If a passenger suffers from certain heart or lung diseases or from a low blood count, this may mean that not enough oxygen can be absorbed into the blood for distribution to the organs of the body. Signs of illness may then appear, depending on which organ is not being adequately supplied with oxygen.

If the heart is starved of oxygen, Angina Pectoris (heart cramp) may occur. If the brain is affected, this may cause confusion, paralysis or loss of consciousness. If suffering from a fever, the body's need for oxygen is increased significantly due to symptoms which may appear at a very early stage in the flight. Passengers with fever are advised to avoid flying until the fever has subsided.

Passengers suffering from asthma must be in a stable state without recent attacks. Any medication should always be hand-carried.

For passengers with heart and lung diseases the rule of thumb is: "If you can walk the stairs to the first floor and back with no great difficulty, then you can stand the reduced pressure in the cabin during flight."

Middle ear, sinuses and stomach

According to the laws of physics, air expands when the atmospheric pressure is decreased. A balloon, which holds three litres of air at ground level, will thus expand to hold four litres in a pressurised cabin when the aeroplane has reached its cruising altitude.

You can feel this during take off when the air in the middle ear expands, and when it contracts during landing. The air from the middle ear can only enter and exit through the Eustachian Tube, the channel that connects the inner ear to the back of the naso-oral cavity. Because of the shape of the Eustachian Tube, it is easier for air to get out of the middle ear than to get in. It often needs a helping hand, by holding the nose and breathing out gently with the mouth closed (this is called the Valsalvas manoeuvre.

It is important to do this all the time the aeroplane is descending, since the negative pressure in the middle ear can increase to the point that it causes the Eustachian Tube to collapse. If the mucosa is thickened, as when you are suffering from a common cold, for example, pressure-equalization may be impeded or even be impossible, the condition may become very painful and require treatment from a medical specialist. It is therefore advisable not to fly when the middle ear and sinuses are blocked due to an infection.

Some people, mainly children, have difficulties in carrying out the Valsalva manoeuvre. If you have problems, you could use "Otovent", a balloon with a special mouthpiece, which is placed on the nose and blown. This method is particularly effective and can be carried out by children from the age of three. Otovent is available from good chemists.

When having difficulties in equalising pressure in the middle ear or sinuses during the flight, nasal spray or drops should to be taken as early as possible during the descent. Most Airliners carry a doctor’s or attendant’s kit, from which this medication can be issued on an emergency basis.

Air in the stomach and intestines expands in the same way, and when three litres of intestinal air become four litres in the pressurised cabin, it may be necessary, for the sake of one’s own comfort, to discreetly get rid of this excess air. Since the air in the cabin is renewed approximately 25 times an hour (compared to once or twice an hour in an ordinary room) these gases will soon disappear, generally without disturbing the other passengers.

Deep Vein Thrombosis (DVT) – Blood clots in the legs

Deep Vein Thrombosis (DVT) has been called ‘Economy Class Syndrome' by some media. This, of course, refers to the possible connection between the risk of developing DVT and the relatively confined space available to the passengers in economy class seats. DVT however, is not restricted to passengers in economy class; it also occurs in passengers in Business Class and First Class. In fact, DVT can occur in any situation where a person is sitting still for a long time, in the home, for example, or at work, on buses and also – naturally –in an aeroplane.

Under normal circumstances, blood is pushed back from the legs to the heart with the help of what is called the "muscle pump" action, i.e., when we use the muscles in the legs, these veins contract and push the blood from the legs back up to the heart. Valves in the veins make sure that the blood cannot run backwards.

DVT occurs particularly in situations when the blood is pumped back from the legs too slowly, or when it stops completely. This may be due to sitting completely still without moving the legs. DVT can also occur if there are defects in the valves in the veins, allowing the blood to flow backwards. If the blood is thicker than normal, because of dehydration (lack of fluid) for example, the risk of developing DVT increases. Pregnant women and women on birth control pills have an increased risk of developing DVT.

It is therefore of great importance that passengers constantly use the muscles in the legs by moving toes and feet during the flight, and if possible go for small walks, preferably every hour..


The air temperature outside the plane is generally –54° C. This air is then taken into the plane and warmed up. Since cold air does not contain much moisture, the humidity level in the cabin is very low, with most of the humidity coming from the passengers themselves (evaporation and exhaled air).

Cabin humidity is generally around three to five percent, compared with the normal 60% or so in temperate latitudes. Since coffee, tea and, in particular, alcohol, have a dehydrating effect, the body may start to suffer from a lack of fluid. Passengers can help prevent dehydration by drinking plenty of water before and during the flight.

Support hose (support stockings)

It is now possible to buy "medical" support hose / compression hose of a very high quality and which look like normal tights. They are available in several colours, including black for men. These support hose squeeze the leg, mainly at the ankle and then decreasing up the calf, so that there is a graduated level of pressure is exerted on the veins. The blood is thus pushed in the right direction, towards the heart. One example of these stockings is the support/compression hose marketed by Jobst/Beiersdorf, and which can be bought from most chemists. Passengers with an increased risk of developing DVT are advised to use such support stockings during flight.

Junior aspirin

Unless individuals have known allergies, a low dose of Acetylsalicylic acid (i.e., Junior Aspirin) is recommended on the day of departure. This will reduce the propensity of the blood to cloth (same mechanism as when aspirin is used for prevention of thrombosis).

If you are on regular medication, always bring this on board in your hand luggage. When travelling alone, you should inform the cabin crew about this when boarding.

If in doubt about possible health risks if travelling by air, passengers are always advised to consult their General Practitioner for assessment and advise.

Enjoy your flight!