Intermittent compression units assist in venous and lymphatic drainage by creating a pressure gradient that forces fluid out of the extremity through the venous system and spreads solid matter proximally along lymphatic ducts. The appliance may be filled with air (pneumatic compression) or chilled water (cryocompression) and may inflate as a single unit or sequentially. The ON/OFF cycle assists in milking or pumping edema out of the extremity.
• Intermittent compression units use mechanical pressure to encourage venous and lymphatic return from the extremities. Compression units consist of a nylon appliance designed to fit the body part (e.g., foot and/or ankle, half leg, full leg) that is connected to the unit through one or more hoses. The flow of air or cold water into the appliance creates the compression around the extremity.
The resulting compression is either circumferential or sequential. Circumferential compression applies an equal amount of pressure to all parts of the extremity simultaneously. The pressure is gradually increased to a level determined by the operator and held for a preset time during the ON cycle. The pressure then drops during the OFF cycle. The process then repeats.
Through this cycle, swelling is forced toward the torso through the venous and lymphatic return systems. Sequential compression increases the distal-to-proximal gradient through the sequential filling of pressure chambers within the appliance. The most distal compartment inflates, followed by the next compartment, and so on, until pressure is applied to the length of the appliance (Fig. 14-1).
Sequential Compression. Compartments within the appliance fill distal to proximal, forcing the fluids toward the torso. Following the cycle, all the compartments deflate and the process repeats.
✱ Practical Evidence
Constant compression is useful in preventing swelling and assisting in venous return. Intermittent compression is most effective in activating the lymphatic return mechanism.1
Compression devices work on two principles. Mechanical pressure waves force fluids within the venous system back toward the heart.2 When the edema is confined to a local area, a limited number of lymphatic ducts are capable of reabsorbing the solid matter. Lymphatic uptake and return are assisted by spreading the edema over a larger area (usually proximally), allowing more lymphatic ducts to absorb the solid matter within the edema.
Intermittent cold compression units are used to treat acute injuries because of their ease of use and their ability to provide cold and compression while the limb is elevated (ice, compression, and elevation) (Fig. 14-2). Circumferential compression units may also be used immediately between ice bouts to prevent the formation of edema. However, compression units should not be used until the possibility of a fracture or compartment syndrome has been ruled out. In subacute or chronic conditions, intermittent or sequential compression is used ...