Preventing deep vein thrombosis

If you’ve ever been on a long-haul flight, you’re probably aware of the risk of developing deep vein thrombosis (DVT). While air travel may increase your risk of developing DVT, it’s not the only thing that can contribute to this condition.

What is DVT?

DVT is when a blood clot that forms in the deep veins of your body, usually in your lower legs and thighs. 

Blood circulation in your legs relies on the muscle contractions of your calves to act as a pump, which means that blood usually flows upwards towards your heart. When you don’t move for long periods of time, your blood flow can slow down or ‘pool’, causing a blood clot to form.

DVT can also occur in your pelvis or arm, but this is rare.

What causes DVT?

There are plenty of reasons apart from long-haul travel that can increase your risk of DVT including:

  • Being over 40
  • Being a smoker
  • Being immobile as a result of an operation (especially on a hip or knee) or injury
  • Having a blood clot in a vein before
  • Having a family history of blood clots
  • Having a condition that causes your blood to clot more easily (thrombophilia)
  • Being very overweight or obese
  • Having cancer or previous cancer treatment
  • Having heart disease or circulation problems, including varicose veins
  • Being a woman taking a contraception pill that contains oestrogen, or hormone replacement therapy (HRT)
  • Being pregnant or having recently had a baby

DVT and travel

Not all studies have found a link between DVT and long-haul flights but those that do, have found the risk to be similar to other forms of long-distance travel, whether by car, bus or train. This suggests that being immobile for a long time is the common factor.

Generally, your risk of developing DVT when flying is very small – there is about one case of DVT in every 4500 flights lasting over four hours.

Woman on a plane

Signs and symptoms

Many of the blood clots that cause DVT are small and don't produce any symptoms. Your body is usually able to gradually break them down with no long-term effects.

The most common signs of DVT due to a larger clot partially or completely blocking a vein include pain and swelling. Sometimes the skin near the blood clot may feel warmer than the surrounding areas or be redder in colour. 

Is DVT serious?

It can be. If the clot remains where it is, it can cause infection and ulcers. However, the real danger occurs if some or all of the clot breaks off and travels in your blood stream to block one of the veins in your lungs. This is called a pulmonary embolism (PE) and is a common and sometimes fatal complication of DVT.

Can you prevent DVT?

While not every case of DVT is preventable you can reduce your risk by not smoking, maintaining a healthy weight and exercising regularly. For long-haul flights:

  • stay hydrated and avoid alcohol and caffeine
  • wear loose clothes
  • stretch your legs and move about the cabin as much as possible
  • exercise your calf muscles when sitting (by moving your heels up and down while your toes remain on the floor)
  • wear compression stockings if you have other risk factors for DVT.

Surgery can increase your risk of developing DVT, so you may be given anti-clotting (anticoagulant) medicines before and after surgery, or be asked to wear compression stockings after your operation. You may also be given a mechanical pump to use on your feet and legs in the first few days after the operation. 

If you are concerned about your risk of DVT, speak to your doctor.

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