At this point, we have two choices: We can put her on life support, which means inserting a breathing tube through the mouth into the lungs and delivering more oxygen with a ventilator, or we make a decision to continue all other treatments but without a ventilator. The breathing tube may mean a better chance of survival, but it also means she will not be able to talk while it is in and, even with medication, it is painful. If she requires many days of ventilator support, she is facing a prolonged and rocky recovery with an inevitable loss of independence and function.
I have end-of-life conversations about these kinds of decisions every single week as an intensive-care physician. Pneumonia is common and, even with modern treatment, has always been particularly lethal in the elderly and compromised. Ideally, this is an intensely personal decision that my patient would make with me. The reality is that once blood oxygen is dropping during a severe infection, patients have neither the mental clarity nor time for this important discussion. In these critical situations, the legal and ethical responsibility falls on their relatives.