Patient monitoring apparatus 101, placed between a bed and mattress, comprises chambers 3a-3d and a sensor for detecting fluid pressure in the chambers (40, fig. 1), pressure data being compared to detect subject movement. Chambers 3a, 3b of the uppermost quadrants may be placed beneath regions of a cushioning element such as a mattress 13 receiving a patient’s shoulders. A position identifier may be assigned based on the fluid pressures. A carer may be alerted or a dynamic air mattress system operated when no movement is detected within a certain time, possibly wirelessly to a remote device 11, 12, which may be a mobile telecommunications device. The apparatus may comprise a pad of opposed sheets welded together to form isolated cavities, which each chamber including a port fluidically connected to the sensor. The apparatus may mitigate the likelihood of decubitous ulcers or bed sores, caused by rubbing at weight-bearing areas.
