The application of external pressure, known as compression, is a standard practice in the immediate care of open wounds. When an injury occurs, the primary danger is uncontrolled blood loss, and compression serves as a direct mechanical barrier to this flow. For the vast majority of cuts and lacerations, immediate pressure is a necessary first step. However, compression is a nuanced tool in wound care, and its benefit depends entirely on the timing, the force used, and the specific nature of the injury. Applying pressure incorrectly or to the wrong type of wound can cause harm, making it imperative to understand when and how to use this technique safely.
Compression as Immediate First Aid for Bleeding
The goal of applying pressure to an open wound is achieving hemostasis, the body’s process of stopping blood flow. Mechanically, external compression reduces the diameter of damaged blood vessels and provides counter-pressure to the escaping blood. This reduction in flow allows the body’s natural clotting cascade—involving platelet aggregation and fibrin mesh formation—to activate more effectively at the injury site.
The standard first aid protocol involves applying firm, continuous direct pressure over the wound using a clean dressing or cloth. The pressure stimulates a localized neurovascular response that contributes to the vasoconstriction of surrounding small arteries and arterioles. This narrowing of the vessels further slows the flow of blood into the wound bed, working with the physical force of the dressing.
This pressure should be steady and strong enough to visibly slow or stop the bleeding without cutting off circulation entirely to the rest of the limb. If blood soaks through the initial dressing, do not remove it, as this can dislodge a forming clot; instead, place additional layers of material on top and maintain constant pressure.
Coupling direct pressure with elevation of the injured limb above the level of the heart is also standard practice when possible. Elevation uses gravity to reduce the hydrostatic pressure in the blood vessels feeding the wound, which lessens the force behind the bleeding. Maintaining continuous pressure for several minutes is required for the clot to stabilize sufficiently before the wound can be cleaned or bandaged.
When Compression Must Be Avoided
While compression is generally effective for bleeding control, certain injury types make applying direct pressure dangerous. A major contraindication is the presence of a deeply embedded foreign object, such as glass or metal. Applying force in these cases can drive the object deeper into the tissue, potentially causing catastrophic damage to underlying nerves, arteries, or organs.
In situations involving impalement, the object itself may be acting as a plug to prevent severe hemorrhage. The appropriate action is to stabilize the object in place with bulky dressings and apply pressure only around the edges of the wound. Similarly, if there is a suspected fracture or dislocation near the wound site, direct pressure could cause bone fragments to lacerate surrounding soft tissue and vessels.
Compression must also be avoided on wounds where internal organs or tissue are visibly protruding, known as an evisceration. Applying pressure to push the tissue back in can introduce infection or severely damage the delicate exposed structures. Instead, the protruding tissue should be covered lightly with a moist, clean dressing to protect it while awaiting immediate medical transport. This caution applies specifically to penetrating injuries, where the depth of the wound is unknown.
Severe burns, where the skin is extensively damaged, should not be treated with compressive bandaging. The pressure can cause further trauma to the compromised tissue, leading to increased pain and worsening the depth of the burn injury. Furthermore, any application of pressure must be immediately released if the patient reports increasing pain or if signs of circulatory compromise become evident. Signs of compromise include numbness, coldness, or a loss of pulse distal to the injury.
Supportive Compression During the Healing Phase
Once acute bleeding is controlled and the wound has been cleaned and dressed, the purpose of compression shifts from stopping blood flow to providing support and protection. This supportive compression is significantly lighter than the firm pressure used for hemostasis and is often achieved using elastic bandages or medical tape. The primary function during this phase is to manage localized swelling, or edema, around the injury site.
Fluid accumulation is a natural part of the inflammatory response, but excessive edema can slow down the healing process by inhibiting the delivery of nutrients and oxygen to the wound bed. Gentle, supportive pressure helps to facilitate the removal of interstitial fluid, maintaining a healthier environment for cellular repair. This light bandaging also serves the purpose of keeping the sterile dressing securely in place and protecting the delicate new tissue from friction.
Any supportive bandaging applied during the healing phase must never impede circulation. Caregivers must regularly check the extremity distal to the bandage—such as the fingers or toes—for changes in color, temperature, or sensation. If digits appear blue or cold, or if the patient complains of tingling or numbness, the bandage is too tight and must be immediately loosened to restore proper blood flow.