Pope Francis was placed in “critical condition” on Saturday, the Vatican said, just four days after the religious leader contracted pneumonia.

“The condition of the Holy Father continues to be critical. Therefore, as explained yesterday, the Pope is not out of danger. This morning, Pope Francis experienced an asthma-like respiratory crisis of prolonged intensity, which required the administration of high-flow oxygen,” the Vatican said in a statement. 

The pope is not attached to a ventilator but is still struggling to breathe. His treatments are ongoing at the Gemelli Hospital in Rome. The Vatican announced that Saturday’s blood tests revealed thrombocytopenia, associated with anemia, which required the administration of blood transfusions.

Medical staff discovered the pontiff was suffering from a polymicrobial respiratory tract infection on Wednesday. 

Doctors are working to ensure a respiratory tract does not enter his bloodstream which could cause sepsis.

Despite Pope Francis’ condition, his surrounding staff said he had a restful night on Friday.

“The Holy Father remains alert and spent the day in an armchair, although he is more fatigued than yesterday. At the moment, the prognosis remains guarded,” the Vatican shared.

Francis admitted he has written a letter of resignation that would be invoked if he were medically incapable of excusing himself as the head of the Roman Catholic Church.

The Associated Press contributed to this report.