The difference comes when measures are taken (deliberate overdoses or other medications designed to end life, removal of nutrition and hydration) that will only result in death.
“A person has every right to have a DNR or medical directive against ventilators. This IS NOT incompatible with being pro-life because they do not necessarily end a person’s life.”
True. Although you could end up like Ariel Sharon (ie. braindead, but your organs still function without life support machines attached). What then? There’s no real answer to a situation like that.