Debate: what constitutes 'terminality' and how does it relate to a living will?

A moribund and debilitated patient arrives in an emergency department and is placed on life support systems. Subsequently it is determined that she has a 'living will' proscribing aggressive measures should her condition be judged 'terminal' by her physicians. But, as our round table of authorities reveal, the concept of 'terminal' means different things to different people. The patient's surrogates are unable to agree on whether she would desire continuation of mechanical ventilation if there was a real chance of improvement or if she would want to have her living will enforced as soon it's terms were revealed. The problem of the potential ambiguity of a living will is explored.