CHOOSING THE RIGHT TRAVEL SOCK

FLIGHT SOCKS PROVE THEIR WORTH..........

Research shows compression socks can reduce likelihood of blood clots. New tests have shown that wearing compression socks on long-haul flights DOES reduce the chance of getting blood clots.

Research by an Italian team, carried out on 205 people known to be at risk of deep vein thrombosis (DVT), was published over the weekend at a conference in Lisbon. Half of the group were told to wear the socks on a flight lasting around 12 hours, half were not.

Of the 103 people who wore the socks, just one developed a blood clot, while of the people not wearing the socks, six developed clots. The leader of the study, Professor Gianni Belcaro, stated: “If you fly for 12 hours, and if you have a high chance of DVT, there is a chance you will get a clot, but if you wear flight socks it is possible that a clot will not develop.

According to The Times, he added that the best way to avoid DVT was to “stop cramming people into aircraft” – but that until that was a feasible solution, the best bet was to wear compression socks.

TravelMole30.0603 Reproduced with the permission of TravelMole.com, the online community for the travel and tourism industry For more travel news go to www.travelmole.com

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Anti-Embolism Stockings in the Prophylaxis of Deep Vein Thrombosis - By Dr. J I Broch MBChB BSc (hons) For AIRTIGHT INTERNATIONAL – March 2002

Deep Vein Thrombosis (DVT) can be defined as the formation of a blood clot (thrombus) within the veins deep in the leg. It can be a benign condition, but many patients suffer leg problems afterwards. More importantly, there is an associated risk of death by pulmonary embolism (PE), in which a fragment of the clot breaks away from the vein wall and travels with the blood to the lungs, where it becomes lodged in small arteries. When this happens, lung damage occurs and life is threatened.

The 3 main factors in the aetiology of DVT were described in 1846 by Virchow. Effectively, changes in blood clotting potential, vessel shape or flow can initiate the formation of a DVT in an otherwise healthy individual.
DVT occurs due to abnormal blood flow in the leg veins. This can be caused by reduced leg movement, which is necessary to maintain adequate blood return up the leg. Immobility during travel or after surgery will cause blood stagnation deep in the leg veins resulting in increased risk of thrombosis. DVT is most commonly seen in post-operation patients, but a study published in 1999 by Ferrari et al, showed that at least 25% were related to travel, of which more than a quarter were related to air-travel. Although it has long been established that DVT and PE are related to travel, it is only recently that there has been some evidence that air travel may pose additional risk. The main factor in all forms of travel is immobility. For reasons of safety and cabin crew activity, airline passengers have enforced immobility; it is unreasonable to suggest that all passengers would be able to mobilise sufficiently during a flight. It is unfortunate that the press has misnamed the problem ‘Economy class syndrome’, as DVT also occurs in business and first class passengers. Indeed the recent House of Lords report ‘Air Travel And Health’ states that the misnomer is inaccurate. A recent study published in the Lancet showed that cabin environment (low oxygen and low pressure) results in the increase formation of early clots.
The House of Lords report demonstrates that many within the general population will have some degree of irreversible predisposition towards DVT formation and makes several recommendations about reducing risk during travel. Advice includes drinking plenty of fluid, avoiding sedatives and caffeine containing beverages, not sleeping and keeping as mobile as possible.

The recommendations also include the use of graduated compression hosiery.
The purpose of this review is to outline the mechanism and evidence to support the use of ‘Anti-Embolism Stockings’ in DVT prophylaxis.

As previously outlined, passengers will have a degree of irreversible predisposition so in order to reduce their risk, the additional risks due to travel must be tackled. Immobility results in reduced blood flow up the leg (venous return). Anti-Embolism stockings have been designed to assist venous return. Graduated compression hosiery has been used in hospitals for many years to help reduce DVT in ‘at risk patients’. The design is such that there is a different level of compression along the length of the product. The ideal compression (measured in mmHg) is based on work carried out as early as 1973 (Sigel et al) and 1990 (Kakkar) . The relevant pressures are shown in the following table.

The stockings exert a sustained and even pressure over the entire surface of the calves and therefore reduce the cross-sectional area of the leg, the effect of which is to increase the velocity (flow) within the deep veins ( in the same way as the water moves out of a hose pipe quicker when you squeeze it ). An external pressure of just 15mmHg will significantly increase blood flow and thus reduce venous stagnation.

Graduated hosiery has been shown to be of benefit in DVT prophylaxis in several medical studies. The studies have been concerned with post-operative patients and there are indications that the reduction might be as much as 64% in general surgery patients and 57% in orthopaedic patients (higher risk patients) . It does seem that the lower the overall risk of DVT, then the greater is the benefit of hosiery (i.e. DVT is better prevented in lower risk general surgery patients than in higher risk orthopaedic or gynaecological patients). A study in the Lancet, showed that Cabin environment increased the formation of clots, but that compression hosiery may reduce the risk by over 90%. To date there has been one major study looking at DVT on board an actual aircraft and this concluded that symptomless DVT might occur in up to 10% of long-haul airline travellers and wearing compression hosiery is associated with a reduction thereof. Some studies have suggested that slightly less compression is necessary (16.8,14.5,6.4 mmHg are thought to be the optimum), although compression products usually provide pressures within a small range comparable to both sets of figures.
Compression hosiery is available in Knee length and Thigh length, the latter being more uncomfortable. Studies, however, have shown that there is no difference in the efficacy of the two types.

Finally, it must be mentioned that compression products are not suitable for All people. There are some conditions, which can be worsened by high compression and it is important that products are supplied with information about their contraindication.

CONCLUSION

‘Anti-Embolism Stockings’ (knee length) provide an effective, low cost and manageable method of reducing the risk of DVT. Their efficacy has been shown in several studies concerning ‘at risk’ hospital patients and there is every reason to believe the same benefits would be gained by airline passengers. In fact there is some evidence to suggest that the benefits may be even greater for them. It is important to ensure that the product used conforms to the pressure standards dictated by the latest medical evidence and information is provided about its proper use.

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Sigel B., et al (1973) ‘Compression of the deep venous system of the lower leg during inactive recumbency’ Arch Surg 106: 38 – 43
Kakkar V (1990) ‘Prevention of venous thrombosis and pulmonary embolism’ American Journal of Cardiology 54: 50-4
British Journal of Nursing, 1999, Vol 8, No 1: 44 - 49
Jeffery PC et al, ‘Graduated compression stockings in the prevention of postoperative Jeffery PC et al, ‘Graduated compression stockings in the prevention of postoperative deep vein thrombosis’ Br J Surg. 1990; 77: 380-3
Stilburg BN et al. ‘Deep-vein thrombosis following total knee replacement. An analysis of sis hundred and thirty eight arthroplasties’ J Bone Joint Surg. Am 1984; 66: 194-201
Parker-Williams J et al. ‘ Major orthopaedic surgery on the leg and thromboembolism’ British Medical Journal 1991; 303: 531-2
‘Thromboembolic Risk Factors (THRIFT) Consensus Group. Risk and prophylaxis for venous thromboembolism in hospital patients’ BMJ 1992: 305: 567-74
Scurr et al. ‘Frequency & prevention of symptomless deep-vein thrombosis in long-haul flights: a randomised trial’ The Lancet. 2001; 357: 1485-1488
Sparrow RA et al. ‘Effect of antiembolism compression hosiery on leg blood’ Br J Surg. 1995; 82: 53-9

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