
Pressure relief devices decrease pressures from the human body. Skin and tissues directly compressed between the bone and support surface such as, bed and wheelchair increases pressure on human body. Moreover, skin and tissues are pulled in different direction, which also increases body pressure. To overcome on this problem, some advanced pressure relief devices, such as foam filled mattresses, fibre filled mattresses, gel filled mattresses, air filled mattresses and standard foam mattresses, are designed to decrease pressure from different parts of the body. In addition, some high-tech devices, such as air fluidized devices, low air devices and turning beds are also used to reduce body pressure. These devices are placed on the top of mattress and reduce pressures from the body. Gel filled mattresses are viscoelastic materials and decreases pressure from shoulders and hips. These mattresses are also used to reduce headaches and neck pain. Air fluidized beds provide healing environment for affected tissues by minimizing the external forces.