Ordinary versus extraordinary care is not an easy subject, even for medical professionals who try to be well educated and faithful to the teachings of the Church. I still have a hard time defining it and expressing it in particular cases, and I've studied it for years.
Also, what is ordinary care here in Johnstown PA is not necessarily ordinary when I'm doing missionary work in Haiti.
What is ordinary care today may not be ordinary care in five years when a totalitarian regime refuses to pay for what it arbitrarily defines as "futile" and would literally bankrupt a family if forced to provide it out of pocket.
A good place to start might be something like this Linacre article:
Thanks for the link. You are right that is is not an easy subject. I will read more about it.