As a family practice physician, I work with people from the beginning to the end of life. I talk to people about death and dying, and try to help them determine what they do and don't want with end of life care.
Not surprisingly, most people feel as Terri Schiavo did: if there is no or minimal hope of return to a functional, interactive life, let me die. Pull the plug, remove the feeding tube, no sustenance, please.
Also not surprisingly, when this decision is left up to family there are more agonizing decisions. The members closest to the dying person tell me to let the dying person go. The ones flying in from far away tell me to do everything medically possible to keep their mother/father/uncle Bob alive. The less connected the relative, or the more tumultuous relationship with the dying person, the more ardently they try to keep death at bay.
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Why? We need to come to peace with the dying person. We need to be able to let go. We need to know that what we have had with them is enough. We need to do what is right for them, not try to fulfill a need to hang on because of our own unfinished business with the person who is dying.
I have found uniformly the family members who want to "do everything" in a situation without hope of recovery, are either selfish and self-absorbed and have no empathic ability, or are guilt-ridden over a rocky relationship and somehow hope that by keeping mom/dad alive, this can heal. This is how I see Terri Schiavo's parents.
So, all of us with the hope of a peaceful death but less-than-sanguine personal relationships, fill out those living wills. Don't let your disaffected sons and daughters decide what constitutes life. Living wills can save your life (or death, so to speak). (http://www.uslivingwillregistry.com/forms.shtm)