Evidence of a coma can depend on the situation. Some people will twitch or move involuntarily. Others will lie completely still and be unresponsive. If the muscles that control the lungs and chest are affected, the person may be unable to breathe unaided.
Doctors use two scales to evaluate potentially comatose patients.
TheGlasgow Coma Scale determines the degree of mental impairment by assigning a score ranging from three (deepest coma) to 15 (normally awake and alert), based on eye response, best verbal response and best motor response.
The Rancho Los Amigos Scale helps doctors follow the progression of a head injury survivor recovering from a coma. It is most useful during the weeks or months directly after the injury.
Based on the results of the scales, doctors assign patients one of four awareness states:
Comatose and unresponsive-Patient can't move or respond to stimuli.
Comatose but responsive-Patient responds to stimuli, with reactions including movement and increased heart rate.
Conscious but unresponsive-Patient can hear, see, taste and touch, but can't respond.
Conscious and responsive-Patient is out of the coma and can respond to commands.