Pope Francis, in critical condition battling double pneumonia, had a "tranquil" night, was alert and had rested after a respiratory crisis and blood transfusions, the Vatican said on Sunday. The pope

ROME — Pope Francis was conscious but still receiving high flows of supplemental oxygen Sunday following a respiratory crisis and blood transfusions, as he remains in critical condition with a complex lung infection, the Vatican said.

Concerns over Pope Francis' health have mounted in recent years as have questions about his succession. Here's what we know.