Q. Is there a mitzvah to visit (bikur cholim) a patient that is on coma or brain dead and is unaware of the visit, and all his needs are also cared for?
A. Poskim rule that since one of the more significant parts of the mitzva of visiting the ill, is for the purpose of davening for his refuah, since the Shechina is present at the head of the bed of the patient, therefore even if the ailing is sleeping, he is a newborn or in coma and totally unaware of the presence of his visitor, he still complies with the great mitzva of bikur cholim. There are also other issues, such as removing part of the illness, that may apply. (Shita Mekuvetzes Nedarim 39a, see Tzitz Eliezer – Ramas Rochel 7, Mincha Yitzchok 2: 84, Avnei Yashfe 1: 230 et. Al,). Horav Shlomo Miller’s Shlit’a opinion is similar.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a