A study carried out at the University of Leicester, UK, found no link between reduced cabin air pressure and Deep Vein Thrombosis (DVT) among individuals who are not at higher than normal risk of blood clots.

Dr. William Toff, study team leader, stated that the link between long-haul flights and DVT is evident, especially for older passengers and people with a higher than normal risk of developing blood clots. What is not clear is whether it has anything to do with the air pressure in the airplane cabin.

The researchers gathered 73 healthy volunteers. They had to sit in a hypobaric chamber – a room with reduced levels of air pressure and oxygen, as would be the case in the cabin of an airplane during a flight. For 55 minutes of each hour the volunteers had to remain in their seats.

The participants had their blood tested both before and after the eight-hour session in the hypobaric chamber. When the researchers analysed their blood after the session for indications of clot formation they did not find any. They found no evidence that low air pressure and oxygen levels activated the clotting mechanism.

As none of the volunteers were high risk individuals for blood clots, Dr. Toff said his study did not show whether higher risk individuals would, or would not be affected.

All the test did was show that lower air pressure and oxygen levels for eight hours do not raise the risk of DVT for healthy individuals who get up and walk around for five minutes of every hour.

As cases of DVT occur more often among economy class than business or first class passengers on long haul flights, it may be useful to examine what effects cramped conditions for prolonged periods could have on the formation of blood clots.

A clot that forms in a vein in your leg can work its way to the brain or lung artery and cause serious problems to your health, even death. Doctors say the best way to protect yourself is to get up and walk around as often as you can during your flight. It is also advisable not to let your feet hang and dangle – try to have your feet touching the ground while you are sitting so that the weight of your legs is supported by the feet, not only the backs of your thighs. You can buy special socks/stockings for long haul flights which reduce the risk of developing DVT.

What is Deep Vein Thrombosis (DVT)?

DVT is a thrombus (blood clot) that develops in a deep vein, most commonly in the lower leg – below the knee. However, it can also develop in other parts of the body, such as the arm. In the United Kingdom about one person in every thousand develops DVT.

Deep veins are called ‘deep’ because they pass through the centre of the leg – they are completely surrounded by muscles.

DVT is much more serious than Superficial Thrombophlebitis, which appear under the skin. DVT develops much deeper down.

Symptoms of DVT

In the majority of DVT cases the clots are small and sort themselves out without any danger to the person – these have no symptoms.

A larger clot may block the vein completely or partially. In such cases the patient may experience:

— Calf swelling
— Pain in your calf
— The pain in your calf is worse when you stand up or walk

These symptoms do not always mean the person has DVT.

Danger

Most cases of DVT are not dangerous. However, some complications can occur:

— The clot can work it way to the lungs and get lodged in there and block blood flow. This is called Pulmonary Embolism. The patient will experience chest pain and/or breathlessness. The patient should see a doctor immediately.

— The blood clot can damage the valves in the vein. The blood does not flow well and builds up in the lower leg. This is called Post Thrombotic Syndrome. The patient will experience leg pain, and may develop ulcers. The patient should see a doctor immediately.

Risk Factors

Below is a list of some factors which may raise a person’s risk of developing DVT:

— If you are over 40 your risk is higher than people under 40. The older you get, the higher the risk.

— You have had DVT before

— Members of your immediate family have had DVT

— Some inherited conditions make the risk of developing DVT higher

— Immobility (not moving or walking around)

— Obesity

— If you recently had an operation or injury, especially on the hips or knees

— You are pregnant

— You recently gave birth

— You are being treated for cancer

— Some contraceptive pills with oestrogen (most of them today have lower levels of oestrogen)

— Your are having hormone replacement therapy

— You are having treatment for heart or circulatory problems

This is a list of just some of the factors. If you would like to know about them in more detail and seek advice on how you may be affected, you should see your doctor.

Useful Web Site: www.dvt.net/home.do

Written by: Christian Nordqvist
Editor: Medical News Today