Principles of Compression Therapy
The concept of compression therapy lies on a simple and efficient mechanical principle: the application of an elastic garment around the leg.
By compressing the limb with graduated compression - strongest at the ankle and decreasing going up the leg - the compression stocking helps the venous return, decreases venous pressure, prevents venous stasis and deterioration of venous walls, and efficiently relieves aching and heavy legs by aiding the body in moving blood up the leg against the pull of gravity.
This treatment is prescribed by a physician to treat phlebitis, thrombosis and aftercare following surgery, sclerotherapy and any other forms of varicose vein treatment, and also to relieve all conditions of chronic venous disease (heavy legs, varicose veins, oedemas, leg ulcers)
It can also be prescribed to prevent venous issues during pregnancy and long distance travel. If no contraindications like severe arterial insufficiency are present you may even buy compression stockings of lower pressure without prescription.
Depending on the pathology, medical compression therapy can be applied in different forms: socks, stockings, pantyhose or bandages.
The current new textures and fashion designs of SIGVARIS® compression products encourage better patient compliance.
The principle of this therapy is to exert a controlled pressure on the limb. The pressure unit is the millimeter of mercury (mmHg) or the hecto Pascals (hPa). 1 mmHg = 1.33 hPa.
The pressure is exerted by the application of a device on the limb.
Stockings or bandages are called medical devices. They must meet strict requirements. The devices are called orthesis meaning that their action is to support or to reinforce a part of the human body, and not to be a substitute like a prothesis.
The action of the device is mechanical. It utilizes the principle of hysteresis that is defined by the stretch-relaxation curve of an elastic body. The transmission of the pressure to the vascular system by those devices is indirect.
The principle stands against the hyperpressure induced by a defective venous system
The pressure is stronger at ankle level. The compression device must exert a contra-pressure where the pressure level is the strongest : at the ankle.
The pressure is degressive. The direction of the blood stream must be respected. Therefore the pressure must be degressive. The gradual pressure decrease is defined in the requirements of the devices, and depends on the compression classes.
The pressure is determined by:
- The elastic recoil force of the hosiery
- The form of the leg: The pressure exerted on the leg depends on the curvature of the local surface (Laplace Law). Thus, a given stocking exerts a higher pressure above the tibial edge and the Achille's tendon and a lower one at the lateral aspect of the leg. Behind the ankles, no pressure is exerted as the garment does not touch the skin.
- Pollack A.A. et Wood E.H. Venous pressure in the saphenous vein at the ankle in man during exercise and changes in posture. J Appl Physicl. 1949,1: 649.
- Partsch H., Rabe E., Stemmer R. Compression. Chaptre 5. In: Compression of the extremities. Editions Phlébologiques Françaises. 2000. Paris. Pages 57-134.
Effects of compression
1. Hemodynamics effect
- Increases venous blood flow
- Decreases venous blood volume
- Reduces reflux in diseased superficial and/or deep veins
- Reduces a pathologically elevated venous pressure
2. Effect on tissue
- Reduces an elevated oedema in of the tissue
- Increases the drainage of nocious substances
- Reduces inflammation
- Sustains reparative processes
- Improves movement of tendons and joints