Unlike pressure redistribution mattresses, which aim to reduce peak pressures through pressure redistribution, alternating pressure mattress systems work through periodic pressure relief and are designed in such a way that they prevent any part of the body from being subjected to sustained pressure. This is achieved by alternating the parts of the body that are loaded at any one time.
For alternating systems to be effective however, the support surface must sufficiently reduce pressure low enough and for long enough to allow reperfusion.
It is important to know that alternating pressure mattress systems vary in several ways, meaning not all alternating pressure systems are the same. The main technical differences are cell size, cell configuration and cycle time
1. Cell Size:
Cell sizes can vary from mattress to mattress. If the cells are too small, there is a risk that the cells adjacent to a deflated cell will fill the resulting gap and prevent pressure relief. Cells less than 10cm in diameter cannot lift a patient sufficiently.
2. Cell Configuration:
Most alternating pressure mattress systems use a configuration of 2 cell or 3 cell alternation. In a 2-cell system, every alternate cell inflates while the intermediate cells deflate. In a 3- cell system, only one in three cells deflates at any given time. Both of these systems are designed to minimize the time the body is loaded to avoid biochemical and physiological effects that can lead to tissue death. This is done by stimulating normal body movement. This intermittently takes the pressure below individual thresholds and allows a natural reactive hyperemic response.
3. Cycle Time:
7.5 minute cycle times mimic natural spontaneous movements to relieve pressure. This is highlighted in physiological studies that showed that patients who moved every 7.5 minutes did not go on to develop pressure injuries. Longer cycles are also designed to provide regular reperfusion and may be more comfortable for some patients.
For a full understanding on the Design and Use of Alternating Pressure Surfaces, you can download a copy of Linet’s Clinical Guide: Why Alternate?