An alternating pressure mattress (APM) is specialized medical equipment designed to provide a dynamic support surface for individuals confined to a bed for extended periods. This device uses a mechanical system to constantly adjust and redistribute the pressure exerted between the patient and the mattress surface. The primary purpose of an APM is to actively manage pressure. This technology is a standard intervention in clinical settings to support the health of patients with limited mobility.
How Alternating Pressure Works
The core of an alternating pressure mattress system consists of interconnected air cells or bladders that run laterally across the bed surface. These cells are linked to an external pump and control unit that regulates the inflation and deflation process. This mechanism creates a constantly changing support profile, providing active therapy.
The control unit governs a cyclical process where specific groups of air cells are systematically inflated while others simultaneously deflate. In a common 1-in-3 cycle, two-thirds of the body is supported by inflated cells while the remaining one-third rests on deflated cells. This cycle repeats over a specified period, often ranging from 5 to 10 minutes, ensuring no single area is subjected to sustained pressure. By periodically offloading pressure, the system allows blood flow to return to compressed tissues, which is essential for maintaining tissue viability.
Preventing and Treating Pressure Injuries
The medical necessity of an alternating pressure mattress relates directly to the prevention and management of pressure injuries, sometimes known as bedsores. These injuries occur when prolonged pressure restricts blood flow to the skin and underlying soft tissue. Without adequate blood flow, the tissue is deprived of oxygen and nutrients, which can quickly lead to cell damage and tissue necrosis.
Areas over bony prominences, such as the sacrum, heels, hips, and elbows, are most susceptible to developing these injuries. The dynamic pressure redistribution offered by the APM counteracts this risk by ensuring no single area is subjected to sustained pressure. This active pressure relief is beneficial for individuals unable to independently shift their weight or reposition themselves. APMs are used both as a preventative measure for high-risk patients and as a treatment strategy for existing early-stage injuries, typically Stage I or Stage II, promoting healing by improving circulation.
Different Types of Alternating Pressure Mattresses
Alternating pressure mattresses are available in various configurations to suit different patient needs and care environments. One common distinction is between a mattress overlay and a full replacement system. An overlay is a shallower air-cell pad placed directly on top of an existing standard mattress, offering a cost-effective option for temporary or lower-risk situations.
A full replacement system is a thicker, self-contained mattress designed to completely replace the standard bed surface, providing a higher level of pressure relief for patients at greater risk. Some systems also incorporate Low Air Loss (LAL) technology, which continuously circulates a small volume of air through tiny perforations in the mattress surface. This gentle airflow helps to wick away moisture and reduce heat build-up, which is important for managing the skin’s microclimate and preventing breakdown. The choice depends on the patient’s risk level, mobility, and the severity of any existing pressure injuries.