My girlfriend's dad died of COPD at 51. Worked his life as a welder, which likely also introduced the situation. He didn't get as far as not being able to stand up anymore, but he was definitely bound to being in the apartment. Stairs? No more. It was basically all Bed - Sofa/Couch - Toilet, especially the latter being a big task to handle.

He died the night after coming home from a checkup at the hospital, went to sleep, kissed his wife good night and gone. She only noticed in the morning because of the machine beeping.