Inner lining of all veins including the major deep veins have smooth surface, and a valvular mechanism to help venous (blue) blood that returns to the lungs for re-oxygenation to travel unhampered. With ageing plaques are formed in arteries, which obstructs the flow of oxygenated blood as in coronary artery disease. Such plaques never occur in veins under normal situation.
Formation of clots in normal deep veins is called 'Phlebo-thrombosis' as opposed to clot formation in inflamed veins, called 'Thrombo-plebitis'. Here being discussed on Phlebo-thrombosis or commonly called 'Deep Vein Thrombosis' (DVT).
How do you get clots in healthy veins?
During operations preventive measure are frequently taken when people, particularly the elderly and the obese undergo surgical operations where the electrical muscle massage pads are used. Travel by any mode of transport, due to immobility of the lower limbs for long journeys are one of the commonest causes of DVT, though the incidence is rare.
The danger is that these clots being formed in undamaged deep veins can move along with the returning venous blood and cause pulmonary embolism (PE). The word embolus is used to define a moving blood clot, or any material through blood vessels, such as plaque dislodging in arteries during angiograms or Transient Ischemic Attacks (TIA).
In Thrombo-phlebitis the blood clots formed do not travel, and there is no danger of Pulmonary Embolism. The commonest symptom of Pulmonary Embolism (PE) is sharp chest pain with or without breathlessness. If the circulating clot is large it would be life threatening.
Each year in Australia there are up to 400 deaths from pulmonary embolism (PE) and of these only a small appear to be associated with air travel. However, it was the publicity surrounding two unexpected deaths from Pulmonary Embolism — a blood clot travelling from the legs to the lungs — after long-haul air travel in 2000 that sparked renewed interest in the issue and much public debate.
Some pre-disposing factors include smoking, age, obesity and pregnancy. Use of oral contraceptive pill and hormone replacement therapy among post-menopausal women is another cause for concern. Other causes are cancer, lower limb injuries or surgery, family history of DVT and previous history of thrombosis or embolism.
The Australian Society of Thrombosis and Haemostasis recommends the following to avoid DVT:
Drink plenty of (non-alcoholic) fluids during flights
If symptoms occur, seek medical advice without delay.
Most airlines demonstrate on sky screen the type of ankle exercises you should do regularly whilst sitting down for long hours on a plane. The movements make the peripheral calf muscles to freely pump the venous blood towards the heart. These exercises must be carried out frequently by all long distance travellers. Deep Vein Thrombosis is very rare among the Asians, but the demonstrated exercises should be done frequently on flights by all travellers.
Economy Class Syndrome
Low cabin pressure, low humidity has a dehydrating effect that concentrates the blood making it sluggish. Alcohol makes you more dehydrated and ads as a minor factor for clot formation
Symptoms of DVT
In some cases DVT does not give rise to any symptoms. Swelling around the ankle region may appear subsequently, and the area of the skin will be warm and red in colour. The redness is not visible among the dark Asians.
If you experience calf pain and tenderness when you are ravelling by a plane, promptly call a flight attendant and request for a crepe bandage. This should be wrapped from bottom, starting at the ankle right up to the knee area quite firmly. This compression required to prevent clot travelling. Drink plenty of water, abstain from alcohol consumption.
As soon as you land, see a doctor who'll order an ultra-sound (duplex ultrasound)to confirm. If the doctor is not satisfied with negative results, he may order a venogram.
Venogram uses an X-ray image to tract the distribution of a special dye injected into the vein at the ankle.
If symptoms are severe with difficulty in walking you may need hospitalisation. Intravenous drugs such as heparin will be given through drip to dissolve the clots.
Rare cases surgery may be required if there is no improvement.
According to the www.airhealth.org 3-5% of air travellers will develop clots. Most experts do not agree that clots are formed direct due to air travel. In the absence of large-scale studies, some airlines' authorities feel there is no scientific basis to warrant thrombosis prevention on flights. Ironically, most airlines include extensive instructions in flight magazines on how to avoid DVT during flight.
However, the apparent increase in risk has prompted some afflicted travellers to site the Warsaw Convention of 1929, which holds airlines liable for damages when passengers are injured by an accident, as grounds to file negligence claims against the carriers. The debate is whether a blood clot is a preventable event, or an individualized reaction to normal flight operations.
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