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This NIHR-funded trial found that using intermittent pneumatic compression sleeves around the legs was effective in preventing deep vein thrombosis in immobile people after a stroke.

When used on people admitted within three days of an acute stroke, this technique was inexpensive and also appeared to improve survival at six months. The results of this study were used in the 2015 update to the 2010 NICE guideline about the care and treatment of people who are at risk of developing deep vein thrombosis while in hospital. Healthcare staff working in UK stroke units may require training in the use of intermittent pneumatic compression devices. Providing information to people with stroke and their carers in the benefits and risk of treatment may help them maintain the treatment for 30 days.

Why was this study needed?

People with stroke who are admitted to hospital and are immobile for a period of time are at risk of developing deep vein thrombosis which can lead to serious complications including death. Every year around 110,000 people have a stroke in England. The risk of deep vein thrombosis may affect 20% of immobile people in the first few weeks of stroke. Although there are drug treatments they increase the risk of bleeding and may not be safe especially in people with stroke. Other treatments such as elastic compression stockings may not be effective for preventing deep vein thrombosis.

This trial aimed to find out if whether using intermittent pneumatic compression thigh-length sleeves in stroke patients can reduce the risk of deep vein thrombosis in people with stroke who are unable to walk independently.

What did this study do?

This NIHR-funded trial (CLOTS 3) included 2876 immobile stroke patients within the first three days of their hospital admission in 94 UK hospitals. Half of the patients were randomly allocated to standard medical care and the other half to standard care plus intermittent pneumatic compression for 30 days or until they could walk independently or were discharged from hospital. The device needed to be worn day and night on both legs; however, some people had the sleeves removed for some days. Only about a quarter of patients complied fully with the requirement to use the device for one month.

The study included a cost-effectiveness evaluation from an NHS hospital perspective.

What did it find?

  • There was a reduction in deep vein thrombosis in those using the device. After excluding people who died before 30 days or those not assessed by ultrasound, 122 (8.5%) of the people in the device group and 174 (12.1%) of the people in the standard care group developed deep vein thrombosis within 30 days. This means that 36 in every 1000 people using the device avoided a clot by using the device. Absolute risk reduction 3.6% (95% confidence interval [CI] 1.4 to 5.8).
  • At six months’ follow up 240 (16.7%) people in the device group and 312 (21.7%) in the standard care group had developed deep vein thrombosis (absolute risk reduction 5.0% (95% CI 7.9 to 2.1).
  • There was also a significant improvement in survival over six months in the device group compared with the standard care group (hazard ratio 0.86, 95% CI 0.74 to 0.99).
  • There was a small increase in skin breaks due to the device. Forty four people (3.1%) in the device group and 20 people (1.4%) in the standard care group developed skin breaks. Absolute risk increase 1.7% (95% CI 0.6 to 2.7).
  • The direct cost of preventing a deep vein thrombosis was £1,282 per event (95% CI £785 to £3,077).

What does current guidance say on this issue?

The 2010 NICE guideline about the care and treatment of people who are at risk of developing deep vein thrombosis while in hospital states that drugs are not enough to prevent thrombosis. The use of elastic compression stockings is also not recommended. For people with stroke the guideline’s 2015 update states that intermittent pneumatic compression can be considered for prevention in immobile patients who are admitted within three days of acute stroke. Intermittent pneumatic compression should continue for 30 days or until the patient is mobile or discharged, whichever is sooner. The NICE updated recommendation has taken into account the results of this trial.

What are the implications?

To implement the updated NICE recommendations for prevention of deep vein thrombosis in patients with stroke admitted to hospital healthcare staff working in UK stroke units will require training in the use of intermittent pneumatic compression devices. Medical, nursing and therapy staff will also require training in selecting the patients who might benefit from this treatment and in providing information about the device to people with stroke and their carers.


Dennis M, Sandercock P, Graham C, et al. The Clots in Legs Or sTockings after Stroke (CLOTS) 3 trial: a randomised controlled trial to determine whether or not intermittent pneumatic compression reduces the risk of post-stroke deep vein thrombosis and to estimate its cost-effectiveness. Health Technol Assess. 2015;19(76):1-90.

This project was funded by the Chief Scientist Office of the Scottish Government and the National Institute for Health Research Health Technology Assessment programme (project number 08/14/03).


NHS Choices. Stroke. London: Department of Health; 2014.

NICE. Venous thromboembolism: reducing the risk for patients in hospital. CG92. London: National Institute for Health and Care Excellence; 2010.

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre

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Deep vein thrombosis occurs when a blood clot forms in the deep veins of the body, usually in the leg or pelvis. Venous thromboembolism is a more general name referring to a blood clot in any vein. The most serious complication of deep vein thrombosis is when the blood clot moves and travels in the bloodstream to block the artery taking blood from the heart to the lungs. This is called pulmonary embolism and can be life threatening. There are a number of risk factors including hereditary factors, having a cancer or another serious medical condition, or being immobile for a period of time, for example when in hospital or after surgery.

Intermittent pneumatic compression uses an inflatable sleeve or boot that wraps around the leg, pressure lines are connected between the sleeve and an air pump. When activated, the pump fills the air chambers of the sleeve and presses on the muscle in the leg. This forces blood out of the pressurised area. A short time later, the pressure is reduced allowing blood to flow back into the leg. The flow in and out is thought to help prevent clots forming.


Expert commentary

Venous thromboembolism and deep vein thrombosis are big problems in stroke care. They are common and cause both mortality and morbidity. So any effective treatment to prevent them is welcome, especially when it is inexpensive and straight-forward. These results showing that intermittent pneumatic compression can reduce deep vein thrombosis and mortality in immobile stroke survivors are very good news. They should be implemented into clinical practice and added to national clinical guidelines. Further research to enhance adherence and reduce the incidence of skin breaks would be useful.

Sarah F Tyson, Professor of Rehabilitation, Stroke and Vascular Research Centre, University of Manchester

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