At least in Russia, typical treatment for severe pneumonia was pressure chamber ( increasing pressure you increase number of oxygen molecules in unit of volume ) or just adding oxygen to the breathing air.

Of course it is possible that some old and weak person could lose any strength in lung muscles trying to breath intensively, but you have to just don't give a fuck to his condition for a long time and intentionally leave him suffocating instead of placing him in pressure chamber or feedng with additional oxygen to make him breathe normally. So, you have to intentionally make lung muscles weak to get a reason for intubation in case of pneumonia. And it will not be pneumonia, it will be lang muscles failure. Obviously.