Monitoring patient use of pressure relief mattresses comprises providing a pressure relief mattress having a system which includes a pump 12 connectible to a flexible pressure chamber of said mattress and applying a sequence of differing pressures to the chamber for the alleviation of pressure to a patient supported on said mattress. Sensors 44, 46, 48, 50 are provided to sense different operating parameters of the pump and feed signals to a processor 26. In operation the processor analyses the signals to determine correct use during the period of operation. In embodiments the system can monitor patient absence from bed or mattress pressurisation system failure. Can be provided as part of a wireless communication network including a plurality of said mattresses. Sensors can be provided in close proximity to a conductor associated with a power supply and a fluid pressure output conduit of a pump, therefore being remote from the patient to provide non-intrusive monitoring.
