Do Not Reconsider

I signed my first DNR order today. I did not refuse, but I can't say I'm proud of it. The philosophical conumdrums that come into play are weighty enough not to talk about at length.
(And what follows, it should go without saying, is not a religious or halachic treatment.)

What confused me in this instance was that I, as one of the treating physicians, was asked to confirm that resuscitation of the patient in this case would be "medically futile."

I don't know what the phrase means. Of course, I could look it up, but it seems to me on first glance -- and what is a blog after all but a displaycase for first glances and uninformed impressions? -- that most possible understandings would be either truisms or impossibilities. Does medically futile mean that resuscitation would not return a patient to his baseline functioning (i.e. before the illness)? Or that it would not cure the diseases which originally caused the cardiopulmonary problems in this patient?

Perhaps the most likely meaning is that it would condemn the participants - patient, family, and doctor alike - to a process which renders medical decision making futile, since all end points are the same.