The issue of blood clots during long distance travel is an ongoing fear for many travellers, even though it is a very rare event in healthy people (see risk factors below). We will look at the risks of getting a ‘deep vein thrombosis’ (DVT) and how we can prevent this from happening.
What is a deep vein thrombosis?
A DVT is a blood clot that forms in one or more of the large veins, usually in the leg, and particularly in the veins of the lower leg. It can happen after sitting still for prolonged periods during any form of travel, generally thought to be any journey of greater than four hours’ duration.
Though a DVT can cause swelling and discomfort in the lower leg, the greater danger of a DVT is the threat that this poses if a part of the clot breaks off. The clot can then travel to the lungs where it causes a sudden blockage of the arteries of the lungs, known as a ‘pulmonary embolus’ (PE). This is a rare but potentially life-threatening condition and requires urgent medical attention.
Who is likely to get a DVT?
The popular misconception is that DVTs are caused by air travel, especially in the economy cabin – referred to as ‘economy class syndrome’ in the late 1970s. This is not entirely accurate since it implies that a DVT is the result of travel in an aeroplane. In fact, the cause of a DVT is the immobility from any form of travel whether that be in a car or a coach or a plane. The preferred term is now ‘travel related thrombosis / venous thromboembolism (VTE)’
The act of sitting for a long time with your knees bent can potentially restrict the blood flow in the deep veins of the legs, especially in the calves, thus causing the clot to form. It is particularly noticed on a plane where you can be ‘trapped’ in a window seat and it is that much harder to get up and move around, thus encouraging normal blood flow.
Most people who develop travel-associated DVTs have one or more risk factors that make a DVT more likely:
- Previous blood clot – if you have had a recent DVT/PE and are taking anticoagulant medication you will therefore be at NO increased risk
- Family history of blood clots
- Known clotting disorder
- Recent surgery, hospitalisation or injury
- Oral contraceptive use
- Pregnancy (current or delivery within the last six weeks)
- Heart failure or recent heart attack
- People who have had a stroke
- Older age increases the risk (greater than 60 years of age)
- Extremes of height
- Active cancer/chemotherapy
- Limited movement – travel by air / car / coach greater than four hours duration
- Varicose veins with phlebitis
The risk of venous DVT for most travellers is low. For a flight greater than four hours, in healthy individuals, the risk is estimated to be one in 6,000 traveller flights. The risk of PE is estimated to be one in 200,000 traveller flights of duration greater than 12 hours.
What are the symptoms and treatment of a DVT/PE?
A DVT may have no symptoms and you may never know you had one.
If you do get a DVT, the first thing you notice is swelling with pain or tenderness in the affected limb – you may have unexplained tenderness in the calf, for example. The skin may be red and warm to touch. If the vein is completely blocked the limb may have a blue discolouration and be very swollen.
If a part of the clot breaks off and causes a PE, then you will usually experience sudden difficulty breathing that may be accompanied by a racing heartbeat. You may also develop chest pain that is worse if you take a deep breath. If prolonged you may get a cough and you may even cough up blood. Severe acute PE can cause light-headedness and loss of consciousness.
If you notice any symptoms of a DVT you should seek medical advice right away. If you have symptoms of a PE you should go straight to hospital or call the emergency services.
A DVT or a PE will be investigated with blood tests, ultrasound scan, ECG or CT/MRI investigations.
A DVT is treated with anti-coagulant medication over a prolonged period of time – the aim is to prevent any increase in the clot and to help to prevent a PE. The actual clot is broken down internally over time. You will also be advised to wear a compression stocking for a period of time.
A PE may require hospitalisation and more intense anticoagulant treatment, and a longer period of oral anticoagulants.
How to prevent a DVT
There are three ways to protect yourself from the dangers of a DVT:
- Frequent exercise/movement when travelling
- Awareness of the symptoms of DVT and when to seek help
- Discuss prevention with your doctor if you have risk factors
Prevention techniques with long-distance travel:
- Wear loose comfortable clothing
- Drink plenty of water
- Avoid alcohol and sleeping tablets
- Get up frequently during the journey and walk around – take breaks if in a car, choose an aisle seat if on a plane, walk around and stretch on a coach
- Exercise your calf muscles while sitting: pull your toes towards you and push your foot down; move your toes up and down; tighten and release your calf muscles by flexing and extending the ankles.
Prevention if you have risk factors:
- Make an appointment with your doctor in good time before travel, to discuss travel
- Wear fitted medical compression stockings (providing 15-30mmHg of pressure at the ankle)
- Take preventive medication before you travel, either oral anticoagulants or low molecular weight heparin injections, both prescribed by your doctor.
Aspirin can be useful in preventing arterial thrombosis, but it is NOT recommended for the prevention of venous thrombosis in travel.