Pope Francis on Monday suffered two new breathing attacks and was put back on non-invasive mechanical ventilation, the Vatican said.
"Today, the Holy Father experienced two episodes of acute respiratory failure," the Holy See said in a statement.
The breathing issues were caused by a "significant accumulation" of mucus in Francis' lungs, and bronchial spasms which cause airway obstruction.
"Two bronchoscopies were performed with the need for aspiration of copious secretions," according to the Vatican.
"In the afternoon, non-invasive mechanical ventilation was resumed. The Holy Father remained alert, oriented and cooperative at all times. The prognosis remains guarded," the statement said.
Pope Francis' health remains fragile
The development is another setback in the 88-year-old pontiff's battle to recover from pneumonia.
On Sunday, the Vatican said the Argentine pope's condition was stable after suffering an "isolated breathing crisis" and receiving non-invasive, mechanical ventilation on February 28.
