Medical stockings may be failing to prevent some deep vein thrombosis (DVT) deaths in hospital because they do not fit well enough, according to research.
Ill-fitting anti-blood clot stockings could compromise treatment and even cause harm, potentially increasing the number of preventable deaths in UK hospitals, researchers found.
The findings have led to calls for a wide-ranging international survey of patient leg sizes by clinicians.
Long-haul travel isn't the only cause of DVT, say experts
The study was conducted by Dr Lisa Macintyre and her team at Edinburgh-based Heriot-Watt University's School of Textiles and Design.
The experts involved in the study said most people believe long-haul travel is the main cause of DVT, which can lead to pulmonary embolism (PE), in which the blood supply to the lungs is cut off.
But a House of Commons Health Committee report from 2005 found PE following DVT in hospitalised patients caused between 25,000 and 32,000 deaths each year in the UK.
Anti-embolism stockings are commonly used to prevent the development of thrombosis in hospital patients who are bed-bound or unable to keep moving, but the research team said it is critical the stockings fit the patient's leg properly, to achieve optimum blood flow and help prevent the development of a DVT.
Dr Macintyre and her team compared the available sizes of anti-embolism stockings to volunteers' leg sizes, analysing the sizing of 10 styles made by four brands.
They found one brand had sizes that matched the legs of all their volunteers while another had sizes that matched the legs of none.
They concluded that the issue of "fit" has been tackled by some brands by having fewer measurement points that need to be matched to the size chart of the stockings. However, this makes it difficult to guarantee the right pressure gradient or "dose" of compression, the team discovered.
Meanwhile, using open-ended sizes, where there is no upper or lower limit on the leg size that can be fitted with a product, makes it appear as though they fit more patients' legs, but those stockings may not deliver the correct level of
Dr Macintyre said: "Stockings may not fit as many patients as has previously been assumed and clinical guidelines are clear that stockings that don't fit well may compromise treatment and even worse, may cause serious harm.
"The big finding of this work is that some brands claim (via their size charts) to match most legs, but these are unlikely to deliver the correct pressure dose to all 'matching' legs.
"Meanwhile other brands, who are perhaps clearer about which legs their stockings will fit, nevertheless manufacture stockings that are the wrong sizes for many people's legs, and in the worst case none of our volunteers would have fitted any of their products."
Dr Macintyre plans to extend her research to measure stocking pressure and develop a simple method for checking the safety of medical stockings.
Brian Magowan, consultant obstetrician and gynaecologist at Borders General Hospital, said: "There is no doubt that compression stockings reduce the risk of DVTs after surgery, and in a number of other situations. What is unclear is how best to fit them.
"Intuitively, too tight may increase the risk of DVT, especially if patients remove them because of discomfort, and too loose may not prevent blood clots at all.
"It is therefore very welcome that we have this research to standardise the sizes - this will help with future research into prevention, and may later help to prevent this sometimes potentially disastrous problem."
:: The research is being published in the July issue of the International Journal of Nursing Studies.