While the responses did not mean Mr Sharon was likely to fully regain consciousness, doctors said they were "encouraging".

BBC: Ariel Sharon: Israeli ex-PM in coma 'has brain activity'

But if the affected person has suffered severe brain damage, he or she may sustain permanent disabilities or may never regain consciousness.

CNN: Coma

He didn't regain consciousness.

WSJ: Italian Soccer Player Dies

Dr Petelenz told the European Society of Cardiology conference in Vienna that properly timed and performed coughs could allow the patient to maintain consciousness and even regain an effective heart beat.

BBC: Coughing 'could stop heart deaths'