When Is It Permissible to Remove a Patient From a Ventilator?

Some of the proposals for tie-breakers specifically a quality of life or age of the patient are very bad ways to determine tie-breakers. When is it permissible to remove a patient from a ventilator one part of that answer has to be with the informed consent of the patient or of the patient's surrogate. One of the challenges in this whole pandemic situation is remembering old lessons and fundamental principles I would say.