Portable mattress replacement system for the critical care environment The Acer portable mattress replacement system for the critical care environment has been designed for patients at risk of complications due to immobility, including conditions associated with acute respiratory failure.. The Acer portable mattress replacement system is a dedicated low air loss system for patients with a very high risk of developing pressure ulcers and features up to 80° of continuous bilateral/unilateral rotation. Using sensors to detect real time patient positioning, it is a safe, cost effective solution to rotational therapy requirements for the ICU.