Web page from www.sigvaris.com : Principle 09/08/2010

PRINCIPLE OF COMPRESSION THERAPY



1. The principle of this therapy is to exert a controlled pressure on the limb


Action of compression
The pressure unit is the millimeter of mercury (mmHg) or the hecto Pascals (hPa).
1 mmHg = 1.33 hPa.


2. The pressure is exerted by the application of a device on the limb

Stockings or bandages are called medical devices. They answer to specific reglementations that fix their 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 subtitute like a prosthesis does.


3. 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.


4. The principle stands against the hyperpressure induced by a defective venous system





References :

- 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. Chapitre 5. In : Compression of the extremities. Editions Phlébologiques Françaises. 2000. Paris. Pages 57-134.


5. 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.


6. The pressure is degressive

The direction of the blood stream must be respected. Therefore the pressure must be dregressive. The gradually pressure decrease is defined in the requirements of the devices, and depends on the compression classes.


7. 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.










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