Earlier this year, an ambulance brought a man in his 80s to the emergency room at Brigham and Women’s Hospital in Boston. He had metastatic lung cancer; his family had arranged for hospice care at home.

But when he grew less alert and began struggling to breathe, his son tearfully called 911.

“As soon as I met them, his son said, ‘Put him on a breathing machine,’” recalled Dr. Kei Ouchi, an emergency physician and researcher at the hospital.

Hospice patients know that they’re close to death; they and their families have also been instructed that most distressing symptoms, like shortness of breath, can be eased at home.

But the son kept insisting, “Why can’t you put him on a breathing machine?”

Dr. Ouchi, lead author of a new study of how older people fare after emergency room intubation, knew this would be no simple decision.