According to this article in the Daily Mail, terminally ill patients should be encouraged to make a living will; this sets out the patient's wishes in the event of their health deteriorating and their not being in a position to inorm health staff of what they wish to do in terms of treatment.

If you take part in high risk sports or passtimes, you may also wish to make one.

http://www.dailymail.co.uk/news/article-1149433/Living-wills-offered-routine-terminal-patients.html