Saturday 21 September 2019

What brings on deep vein thrombosis?

THERE HAS BEEN much debate about flying and the increased risk of deep vein thrombosis (DVT) and while many people believed the lack of leg room increased the chances of developing DVT, a recent study debunked this theory.

Deep vein thrombosis or DVT is when blood clots form in a deep vein. A clot that develops in a vein is also known as 'venous thrombosis'. DVT most commonly affects the leg veins or deep veins in the pelvis. It can cause pain and swelling in the leg but in some cases there may be no symptoms.

DVT can lead to the potentially lifethreatening condition known as a pulmonary embolism. This occurs when a clot breaks off into the bloodstream and travels to the chest, where it blocks one of the blood vessels in the lungs.

Experiencing DVT and pulmonary embolism together is known as venous thromboembolism ( VTE), which is a condition that can be life-threatening.

A recent study by the American College of Chest Physicians (ACCP) looked at a range of factors that could potentially raise the risk of DVT on flights.

Thankfully there is no need to shell out the extra cash for business class seats according to the study as although cramped budget seats are annoying they present no greater risk than flying business class.

Drinking on board a flight was also often seen as a contributing factor to an increased risk of DVT and again the study found no firm evidence that indulging in a tipple or two while jetting off to foreign climes brings on DVT.

Although there is bad news for those of us who like to spend our flight glued to the window looking at the clouds below as sitting by a window during a long haul flights was associated with a greater risk because of the limited opportunities for walking around.

People's age, previous DVT and recent operations were among the other factors found to raise DVT risk.

The evidence-based guidelines were produced by the American College of Chest Physicians to address the risk of both DVT after long-haul flights and the potentially fatal lung clots (pulmonary embolisms) that can follow. The guidelines also include recommendations about the best ways for travellers to reduce their risk of DVT.

The findings were published in the February issue of the medical journal CHEST.

The evidence review that informed the guidelines looked at a range of risk factors for the development of DVT in long-distance travellers. These included the use of oral contraceptives, sitting in a window seat, advanced age, dehydration, alcohol intake, pregnancy and sitting in an economy seat compared to business class.

The reviewers conclude that developing DVT or pulmonary embolism from a long-distance flight is generally unlikely, but that the following factors increased people's risk:

■ previous DVT or pulmonary embolism or known ' thrombophilic disorder'

■ cancer ■ recent surgery or trauma

■ immobility

■ advanced age

■ oestrogen use, including oral contraceptives

■ pregnancy ■ sitting in a window seat

■ obesity

The finding relating to window seats was discussed further. The study authors suggest that long-distance travellers sitting in a window seat tend to have limited mobility, which is responsible for their increased risk of DVT.

However, the review did not find any definitive evidence to support the theory that dehydration, alcohol intake or sitting in an economy seat (compared with sitting in business class) increases the risk of DVT or pulmonary embolism during a long-distance flight. On this basis, they conclude that travelling in economy class does not increase the risk of developing a blood clot, even during long-distance travel. However, they believe that remaining immobile for long periods of time does.

Overall, the study authors say that ' symptomatic DVT/PE [pulmonary embolism] is rare in passengers who have returned from long flights', but that the association between air travel and DVT/PE is strongest for flights longer than 8-10 hours.

Furthermore, most of the passengers who do end up developing a DVT/PE after long-distance travel have one or more risk factors.

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