External compression, often applied through specialized garments or wraps, is a mechanical therapy designed to manage fluid dynamics in the body. Whether compression increases blood flow depends on whether arterial or venous flow is being discussed. External pressure does not typically increase the volume of oxygen-rich blood flowing through the arteries. However, it significantly enhances the return of deoxygenated blood back to the heart through the veins, a process known as venous return. This targeted effect on the venous system is the primary mechanism behind the widespread use of compression therapy.
How Compression Affects Circulation
Compression garments apply external pressure to the limbs, influencing the diameter of blood vessels and surrounding tissues. The pressure works primarily on the highly compliant veins, which are easily compressed compared to the muscular arteries. By reducing the cross-sectional area of superficial veins, compression forces blood into the deeper veins and increases the velocity of blood flow within them.
This increase in flow velocity discourages blood from pooling in the lower extremities, an issue often caused by gravity and insufficient venous valve function. Compression also supports the venous walls, helping the one-way valves close more effectively to prevent reflux, or backward flow, of blood. A properly fitted garment applies graduated pressure, meaning it is tightest at the ankle and gradually decreases further up the leg. This creates a pressure gradient that physically pushes blood upward toward the heart.
While the main goal is to optimize venous return, therapeutic compression can also positively influence arterial circulation. Studies suggest that external pressure may increase the arteriovenous pressure gradient, leading to an increase in arterial blood flow in the limb. This augmentation of arterial flow, which can be substantial in modalities like intermittent pneumatic compression, is thought to result from arteriolar vasodilation or complex veno-arterial interactions. This beneficial effect is strictly dependent on the pressure level; excessive or non-graduated pressure can constrict arteries and restrict the volume of oxygenated blood reaching the tissues.
Common Uses for Compression Therapy
Compression therapy is widely used across various medical and functional applications to manage fluid and support the circulatory system. One recognized medical application is the prevention of deep vein thrombosis (DVT). DVT is a condition where blood clots form in deep veins, often during prolonged immobility, such as after surgery or long flights. The increased blood flow velocity caused by compression helps disrupt the conditions necessary for clot formation.
Compression is also a primary treatment for chronic venous insufficiency, a disorder characterized by poorly functioning venous valves that lead to blood pooling and high pressure in the veins. By supporting the valves and reducing venous pressure, compression helps alleviate symptoms like leg pain, heaviness, and skin changes. Compression is also used in managing edema and lymphedema, which involve the build-up of excess fluid in the tissues. The external pressure facilitates the movement of interstitial fluid back into the circulatory and lymphatic systems, reducing swelling.
Beyond clinical settings, compression garments are used in athletic recovery to manage post-exercise muscle soreness and fatigue. By enhancing blood flow, compression helps clear metabolic waste products, such as lactate, from the muscle tissue more rapidly. Athletes also use compression to reduce muscle oscillation during high-impact activity, which may decrease muscle damage and improve proprioception.
When Compression Should Be Avoided
Although compression therapy is beneficial for many, its use must be avoided or closely supervised by a physician in specific medical conditions. The primary contraindication is severe peripheral arterial disease (PAD), especially when the ankle-brachial pressure index (ABPI) falls below 0.5. In these cases, the arteries are already significantly narrowed. External compression could further impede the limited flow of oxygenated blood to the tissues, potentially leading to critical limb ischemia and tissue death.
Another condition requiring caution is decompensated or uncontrolled heart failure. Compression increases the amount of blood returning to the heart, which temporarily increases the heart’s workload (cardiac preload). If a patient’s heart is already struggling to pump effectively, this sudden influx of fluid can overload the system and worsen heart failure symptoms.
Compression garments should not be worn over areas with acute skin and soft tissue infections, such as cellulitis or an abscess. The pressure can spread the infection or trap moisture against the skin, delaying healing and exacerbating the condition. Individuals with severe peripheral neuropathy, which often causes a loss of sensation, should use compression with caution. They may not feel if a garment is improperly fitted or causing excessive pressure, potentially leading to undetected skin damage.