A method of assisting a patient 24 in controlling their position comprises using reference position data indicative of a reference position of a patient, actual position data is also monitored and then compared with the reference position data to determine a position deviation, and light is emitted which is detectable by the patient as ambient light if there is a position deviation. In an embodiment the position data is breathing displacement, where the actual position data is based on a breathing cycle of the patient. In alternative embodiments, sound could also be used, for example, by changing the amplitude or tone of sound audible to a patient when there is a position deviation. In embodiments colour could be the property of light used, for example a change in colour from green to blue if there is a position deviation. Alternatively, brightness, hue angle or flicker rate could be used. The light source may be placed outside the line of sight of a patient, or be reflected off surfaces of the medical equipment for example.
