chilul shabbos for cha'yei sha'ah

There is a wild Ohr haChaim in last week’s parsha. The Torah warns “ach es shabsosai tishmoru”; why the need to repeat “v’shamru es hashabbos…la’asos es hashabbos”? Explains the Ohr haChaim that pikuch nefesh is doche shabbos only if the person being saved will live and continue “la’asos es hashabbos”, to observe the shabbos. But to save someone for chayei sha’ah, to save someone who will die on that same day before shabbos is even complete, to break shabbos so someone can have just a few more minutes or hours of life, this is not permitted. The halacha is quite the opposite – one is permitted to break shabbos even for chayei sha’ah, even to extend someone’s life for a few moments longer. The Ohr haChaim seems to be built on the idea (thought he does not explicitly reference it) that the heter for pikuach nefesh stems from the sevara “chalal alav shabbos achas k’dei she’yishmor shabbosos harbei”, it is permissible to break one shabbos to extend a person’s life for the sake of the many future shabbosos that the person can observe. If the person will die within hours of being saved, the basis for the sevara doesn’t work. See Shu”t Minchas Eluzar I:9 which one of the new Mikraos Gedolos editions mentions in a footnote.