Pope Francis' health has deteriorated over the past 24 hours, the Vatican confirmed in a statement on Saturday.
The pontiff suffered a "prolonged asthma-like respiratory crisis" and required blood transfusions. The Vatican's statement revealed that the Pope remains alert, having spent the day in a chair, although his condition is worse than it was the previous day.
"At the moment, the prognosis remains guarded," the Vatican added.
Pope Francis was admitted to Rome's Gemelli Hospital on February 14 after experiencing several days of breathing difficulties. Doctors diagnosed him with double pneumonia, a serious infection affecting both lungs.
On Saturday, the Vatican disclosed that due to the breathing crisis, doctors had to administer a "high flow" of oxygen. The blood transfusions were deemed necessary after tests showed a low platelet count, which is associated with anaemia.
"The Holy Father’s condition remains critical," the statement said. "The Pope is not out of danger."
The Vatican also announced that Pope Francis would not appear in public on Sunday to lead prayer with pilgrims, marking the second consecutive week he has missed the event.
Double pneumonia is a severe infection that causes inflammation and scarring in both lungs, making it difficult to breathe. The Vatican has described the Pope's condition as "complex," attributing it to a combination of micro-organisms.