Q. Re- the recent case of saving the life of a brain dead patient. Taking into account that once the patient was entubed into a respirator, he can’t be disconnected, would it not have been better, if he is already brain dead not to entube him?

A. Likely the patient was placed in a respirator when hospitalized and they were trying to save his life.
See question 129 in regards to returning a terminally ill patient from hospital to die at home, where you can also provide basic nursing and medical care, and the patient has not yet been attached to a respirator etc.
Since all cases are different, and they are many crucial details to every situation, Horav Shlomo Miller’s Shlit’a opinion is that questions on specific cases, should be answered by competent Rabbinical authorities familiar with the case.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a