Pope Francis was in critical condition Saturday after he suffered a long asthmatic respiratory crisis that required high flows of oxygen, the Vatican said.

Francis, who has been hospitalized for a week with a complex lung infection, also received blood transfusions after tests showed a condition associated with anemia, the Vatican said in a late update.

“The Holy Father continues to be alert and spent the day in an armchair although in more pain than yesterday. At the moment the prognosis is reserved,” the statement said.

Doctors have warned that the main threat facing the 88-year-old Francis would be the onset of sepsis, a serious infection of the blood that can occur as a complication of pneumonia. As of Friday, there was no evidence of any sepsis, and Francis was responding to the various drugs he is taking, the pope’s medical team said in their first in-depth update on the pope’s condition.

“He is not out of danger,” said his personal physician, Dr. Luigi Carbone. “So like all fragile patients I say they are always on the golden scale: In other words, it takes very little to become unbalanced.”

Francis, who has chronic lung disease, was admitted to Gemelli hospital on Feb. 14 after a weeklong bout of bronchitis worsened.