Catechism of the Catholic Church
Euthanasia
2276 Those whose lives are diminished or weakened deserve special respect. Sick or handicapped persons should be helped to lead lives as normal as possible.
2277 Whatever its motives and means, direct euthanasia consists in putting an end to the lives of handicapped, sick, or dying persons. It is morally unacceptable.
Thus an act or omission which, of itself or by intention, causes death in order to eliminate suffering constitutes a murder gravely contrary to the dignity of the human person and to the respect due to the living God, his Creator. The error of judgment into which one can fall in good faith does not change the nature of this murderous act, which must always be forbidden and excluded.
2278 Discontinuing medical procedures that are burdensome, dangerous, extraordinary, or disproportionate to the expected outcome can be legitimate; it is the refusal of "over-zealous" treatment. Here one does not will to cause death; one's inability to impede it is merely accepted. The decisions should be made by the patient if he is competent and able or, if not, by those legally entitled to act for the patient, whose reasonable will and legitimate interests must always be respected.
2279 Even if death is thought imminent, the ordinary care owed to a sick person cannot be legitimately interrupted. The use of painkillers to alleviate the sufferings of the dying, even at the risk of shortening their days, can be morally in conformity with human dignity if death is not willed as either an end or a means, but only foreseen and tolerated as inevitable Palliative care is a special form of disinterested charity. As such it should be encouraged.
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My snippy comments: The main problem with this issue is where is the line and who draws it? Of course it's much easier when it is a 64 year old man trying to decide how much treatment he wants while struggling with emphysema, adenocarcinoma and congestive heart failure or a 42 year old mother who is ravaged and tired of suffering and barely holding on just so she can see her youngest child make it to high school.
It's a problem because people will interpret this to be on the side of whatever is most convenient for them, and for most of us, not accompanying someone who is suffering is the most convenient.
However, I think what the passage means is the bizarre extremes of "medical care" - such as the 93 year old woman in my family who was in very frail condition and non compos mentis, suffered a stroke and was brought to the hospital - where they "revived" her and while she screamed and flailed, intubated her - which of course caused her to suffer a massive heart attack that finished her off. There was no need for that "treatment," which added fear and pain to her last moments on this earth. The doctor later told me she ordered it because they are now afraid of being sued if they don't do this.