Unconsciousness is a physiological state in which the patient is unresponsive to sensory stimuli and lacks awareness of self and the environment (Wislowska et al. [133]). There are many central nervous system conditions that can result in a patient being in an unconscious state. In addition, an unconscious state can be medically induced, such as during general anaesthesia. The depth and duration of unconsciousness span a broad spectrum of presentations from fainting, with a momentary loss of consciousness, to prolonged coma lasting several weeks, months or even years. The physiological changes that occur in unconscious patients will depend on the cause of unconsciousness, the length of immobility while unconscious and the quality of care. Drugs (e.g. some muscle relaxants used in intensive care) can contribute to muscle weakness, raised intraocular and intracranial pressure, electrolyte imbalances and reduced airway tone (Murray et al. [78]). Unconsciousness can lead to problematic changes for patients that have implications for nursing interventions, including moving and positioning.