Travel by air, and, to a lesser extent, by coach or car, is a frequent cause of both deep vein thrombosis and pulmonary embolism, which costs the UK economy more than £640m per year.
The immobility experience during long travel causes blood flow to stagnate in the leg veins. Deep vein thrombosis (DVT) will almost inevitably result in several weeks off work with many sufferers developing a long-term handicap; one third of pulmonary embolism (PE) being immediately fatal.
As most DVTs are preventable, we are seeing an increasing number of claims brought by employees who have suffered a DVT during frequent or long-haul air travel. David Platt QC of Crown Office Chambers affirms: “The duty of an employer is to take reasonable care for the safety of its employees, including the means by which they travel to places where they have to work. A review of the evidence appears to demonstrate a sizeable increase in the risk of DVT in passengers undertaking frequent or long-haul flights. As such, an employer would have a duty of care to assess and ameliorate such a risk.”
What is DVT?
DVT is when a blood clot develops in one of the deep veins. Usually, this is in the leg or pelvis, but can occur in any deep vein. Small or asymptomatic DVT occurs in 10% of people within 30 days of completing a return trip involving a flight of at least eight hours. A small DVT can then grow to become symptomatic or a dangerous source of PE during subsequent flights, which explains why frequent flying is also a risk. Obstruction of the vein leads to higher vein pressures and swelling of the limb below the obstruction.
The resultant inflammation causes pain, tenderness, leakage of fluid into the tissues and redness or discolouration of the overlying skin. This thrombus or clot can easily detach and flow with the blood stream up the inferior vena cava, through the right side of the heart and into the pulmonary artery causing a PE which, if large enough, may obstruct the circulation to the lung causing almost instant death.
Every year 100 in every 100,000 people develop DVT, with 40 out of 100,000 developing pulmonary embolism. According to the British Lung Foundation, there were 2,300 deaths from the condition in 2012.
There are significant short- and long-term effects for anyone suffering from a DVT. Aside from the symptoms described above, anticoagulation is routinely prescribed for three to six months to reduce the risk of further thrombosis. These drugs are effective, but also increase the risk of haemorrhage, frequently requiring hospital admission. There is also an increased risk of bleeding in the event of injury.
Following the initial symptoms, 40-50% of patients with a DVT will develop long-term symptoms due to chronic venous insufficiency or ‘post-thrombotic syndrome’. Typical symptoms include aching on standing or prolonged sitting, swelling, heaviness of the leg and permanent skin damage with brown discolouration. Suffering a DVT increases the risk of developing venous leg ulcers in later life by approximately five-fold. These are chronic, painful discharging wounds on the lower leg that are difficult to treat and may take several months to heal.
The inflammation associated with DVT results in scarring of the venous valves making them incompetent, which allows blood to reflux down the leg causing chronic inflammation within the tissues. The result is high venous pressures in the leg causing inflammation of the tissues. Ultimately, this may lead to ulceration of the skin, which is a severely debilitating, painful and unpleasant condition. Ulceration is also often malodorous and always difficult to heal.
Business travel and DVT
Travel by coach, train or aeroplane involves prolonged periods of immobility as the passenger sits in the same seat for many hours, often without moving or walking to activate their calf pump. This results in in prolonged venous stasis, which may precipitate DVT. Asymptomatic calf vein DVT (diagnosed by ultrasound, but not large enough to cause symptoms), can be detected in 10% of people completing two eight-hour flights within the same month.
Larger studies have confirmed that 1% of people flying for over four hours develop a symptomatic and therefore damaging DVT. It is likely that falling asleep on an aeroplane or coach greatly increases the consequences of immobility and is probably an important cause of DVT during travel. The important message for the employer is that this is a preventable condition.
In fact, the NHS recommends that all passengers flying for more than four hours should wear compression stockings. However, one clinical study showed that off-the-shelf compression socks failed to deliver the stated pressure for 98% of wearers.
It is for this reason that my department (surgery) and the department of textiles within the University of Manchester collaborated on the research needed to produce Isobar compression socks, knitted by computer-driven knitting machines, to precisely fit the 3D laser profile of each individual leg. These stockings are the only technology, worldwide, able to deliver bespoke, highly accurate graduated pressures to the limb, maximising compression and comfort.
Using this unique technology 20mmHg compression at the ankle reduces venous transit times by 38%. For those with a high risk (family history of DVT, those who are tall or obese, women on the contraceptive pill), socks delivering 25mmHg compression halve venous transit times and further reducing the risk of DVT.
An employer’s responsibility
An employer, so far as is reasonable practicable, must protect the health, safety and welfare of each employee. Although most employers provide a safe working environment, few honour the duty that extends beyond the traditional workplace. As more and more companies conduct international business, massive increases in air travel are the consequence. Frequent, or long-haul travel is a significant, but preventable risk, to employees who are increasingly litigating as a consequence of long-term disability associated with the consequences of DVT.
Employers owe their staff a duty of care to protect them from, or at least ameliorate against, the risk of DVT associated with frequent or long-haul travel. My advice would be to take 300mg of aspirin (unless contraindicated) with food 4-10 hours before travelling and to use precisely fitted below-knee flight socks, in order to limit prevent DVT and PE. Staff should also be advised to drink plenty of water (not alcoholic drinks!) and exercise the calf muscles by pumping the ankle up and down every 20 minutes during each flight.
What, if anything, is your company doing to protect your employees from the risk of DVT when travelling on behalf of the company?
NHS advice on travel & DVT here
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