Compression therapy involves applying external pressure to the limbs or other body parts to support the body’s circulatory systems. This method helps manage conditions characterized by poor blood flow and fluid accumulation. The external pressure improves the movement of both blood and lymphatic fluid, which is often impaired by gravity or disease. By gently squeezing the tissues, compression helps maintain a more balanced fluid environment, reducing swelling.
Physiological Mechanism of Action
The fundamental goal of compression therapy is to enhance the flow of fluids toward the torso by overcoming gravitational forces and supporting circulatory structures. External pressure physically narrows the diameter of superficial veins in the affected limb. This reduction in the vessel’s internal size, known as the lumen, directly increases the velocity of blood flow returning to the heart.
By accelerating venous blood flow, compression helps prevent blood from pooling in the lower extremities, a condition called venous stasis. Faster flow supports the function of one-way valves inside the veins, which are designed to prevent the backward flow of blood. When these valves are compromised, compression physically assists them in directing blood upward against gravity. Furthermore, the applied pressure provides a firm counter-force against the muscles, which increases the efficiency of the muscle pump action during movement.
Compression improves lymphatic system function, which collects excess fluid, proteins, and waste from the tissues. The external pressure helps push interstitial fluid, or lymph, into the network of lymphatic capillaries. This mechanical action aids in lymphatic drainage and stimulates the intrinsic muscular contractions of the lymph vessels, known as lymphangions, which propel the fluid forward.
Compression reduces edema by preventing fluid accumulation between cells. It counteracts the hydrostatic pressure that causes fluid to leak out of the capillaries into the surrounding tissue. By increasing the pressure outside the vessel, the net rate of fluid filtration from the capillaries is reduced. This combined effect on the veins and lymphatics ensures efficient fluid clearance from the limb.
Key Clinical Applications
Compression therapy is a standard management strategy for several circulatory conditions. It is a primary intervention for Chronic Venous Insufficiency (CVI), where damaged vein valves lead to impaired blood return. Pressure reduces high venous pressure in the lower leg, alleviating symptoms like pain, heaviness, and skin changes. In severe cases, compression aids in healing venous leg ulcers by improving blood flow and reducing localized swelling that impedes tissue repair.
It also manages lymphedema, chronic swelling caused by an impaired lymphatic system. The sustained external pressure prevents the re-accumulation of protein-rich lymph fluid that has been manually drained or mobilized. By maintaining reduced limb volume, compression helps soften the tissue and prevents the long-term fibrotic changes associated with persistent swelling.
Compression also prevents Deep Vein Thrombosis (DVT), particularly in patients with limited mobility. By increasing the velocity of blood flow in the deep veins, the risk of blood stasis is lowered. Preventing blood from pooling reduces the likelihood of a clot forming, a major concern during long periods of immobility, such as surgical recovery or extended travel.
Common Types of Compression Devices
Compression is delivered through various devices, each suited to different medical needs and phases of treatment. The most common form is elastic garments, such as compression stockings or socks, which apply graduated pressure that is tightest at the ankle and decreases further up the leg. These garments are used for long-term CVI management and DVT prevention, providing continuous, mild to moderate pressure. The specific pressure level is measured in millimeters of mercury (mmHg) and is prescribed based on the condition’s severity.
Another category involves bandaging and wraps, typically used during the intensive reduction phase of lymphedema treatment. Multi-layer bandaging systems use short-stretch materials that generate high working pressure when the patient moves but low resting pressure. These wraps accommodate the rapid decrease in limb volume that occurs early in therapy, allowing for frequent adjustments. They provide high-stiffness support that enhances the muscle pump action more effectively than elastic materials.
Pneumatic Compression Devices (PCDs) represent a third, more active method of applying pressure. These devices consist of sleeves for the limbs that contain multiple air chambers connected to an intermittent air pump. The pump sequentially inflates and deflates the chambers, starting at the furthest point from the body and moving toward the torso. This creates a mechanical wave of pressure that mimics natural muscle action, actively pushing fluid out of the limb and stimulating the flow of both venous blood and lymph.