Compression stockings are a specialized hosiery, designed to help prevent the occurrence of, and guard against further progression of venous disorders such as edema, phlebitis and thrombosis. Compression stockings are elastic garments worn around the leg, compressing the limb, exerting pressure against the legs, reducing the diameter of distended veins, and causing an increase in venous blood flow velocity and valve effectiveness. Compression therapy helps decrease venous pressure, prevents venous stasis and impairments of venous walls, and relieves heavy and aching legs.
Unlike traditional dress or athletic stockings and socks, compression stockings use stronger elastics to create significant pressure on the legs, ankles and feet. Compression stockings are tightest at the ankles and gradually become less constrictive towards the knees and thighs. By compressing the surface veins, arteries and muscles, the circulating blood is forced through narrower circulatory channels. As a result, the arterial pressure is increased, which causes more blood to return to the heart and less blood to pool in the feet.
Gradient compression stockings
These stockings are designed to remedy impaired "Musculovenous pump" performance caused by incompetent leg vein valves. They are woven in such a way that the compression level is highest around the ankle and lessens towards the top of the hose.
Doctors will typically recommend these stockings for those who are prone to blood clots, lower limb edema, and blood pooling in the legs and feet from prolonged periods of sitting or inactivity.
They are worn by those who are ambulatory in most cases, where they assist the calf muscles to perform their pumping action more efficiently to return blood to the heart. In some cases, they are worn by those at increased risk of circulatory problems, such as diabetics, whose legs are prone to excessive swelling. A common indicator for the prescription of such stockings is chronic peripheral venous insufficiency, caused by incompetent perforator veins. Low pressure compression stockings are available without prescription in most countries, and may be purchased at a pharmacy or medical supply store. Stockings with a higher pressure gradient, say, above 25-30mmHg, may require a prescription from a doctor.
There are several crucial cautionary steps that need to be taken before using compression stocking:
- A patient's ABI (Ankle Brachial Index) must be >1.0 per leg to wear compression stockings, otherwise the stockings may obstruct the patient's arterial flow. The ABI indicates how unobstructed a patient's leg and arm arteries are. Any competent doctor or nurse can measure and calculate a patient's ABI.
- It is crucial that compression stockings are properly sized. The compression should gradually reduce from the highest compression at the smallest part of the ankle, until a 70% reduction of pressure just below the knee.
Vascular doctors & nurses may use special pads to ensure uniform higher pressure around the circumference of the ankle (to smooth out the irregular cross-sectional profile.) Self-prescription is reasonably safe assuming that the compression gradient is 15-20 mmHg, the ABI (for both legs) is >1.0 and that the stockings fit correctly. "Firm" gradient stockings (20-30 mmHg and 30-40 mmHg) should generally be worn only on medical advice.