ROME and LONDON — Pope Francis suffered two episodes of “acute respiratory failure” on Monday, the Vatican said.

The episodes were caused by a “significant accumulation of endobronchial mucus and consequent bronchospasm,” the Vatican’s press office said in a brief statement.

According to doctors, acute respiratory failure indicates the pope was not responding to oxygen therapy. Endobronchial mucus means there is mucus and fluid in the deep parts of the lung or lungs, causing a bronchospasm, also known as a coughing attack, doctors said.

A man walks in the ward where Pope Francis is hospitalized at the Agostino Gemelli Polyclinic, in Rome, Italy, Sunday, March 2, 2025.
Andrew Medichini/AP

Two bronchoscopies were performed on the pontiff, with “the need to aspirate abundant secretions,” the church said. Noninvasive mechanical ventilation was resumed on Francis and he continues to be “alert, oriented and cooperative,” the Vatican said.

Bronchoscopies allow for deep suction to remove mucus and fluids, doctors said. The noninvasive mechanical ventilation that was resumed on Francis refers to a high-pressure oxygen mask, according to doctors. The accumulation of mucus is a normal reaction of the lungs to pneumonia, Vatican sources told ABC News.

The pope’s prognosis “remains reserved,” the Vatican said in its Monday evening update.

Vatican sources said the pope’s blood levels remain stable and there is no increased presence of leucocytes, white blood cells signaling infection.

The pope has the same complex medical condition described in the past, but he is not out of danger, according to the Vatican sources. Doctors continue to be very cautious and have always left open the possibility that there could have been a crisis, the sources said.

Doctors said it’s not unusual for a patient’s condition to change from day to day.

Faithfuls pray in front of the statue of Pope John Paul II at the entrance to the Gemelli Hospital, where Pope Francis is hospitalized, Rome, Italy, Mar. 3, 2025.
Riccardo Antimiani/EPA-EFE/Shutterstock

Earlier Monday, the Vatican said the pope “rested well” overnight, his 17th night in Rome’s Gemelli Hospital.

“The pope rested well all night,” the Holy See, the Vatican’s press office, said in a brief statement.

The pope’s clinical condition had on Sunday remained “stable,” the church said. Vatican sources told ABC News on Sunday that the pope had eaten breakfast with coffee and continued his treatment. He read the daily newspapers, as usual, the sources said.

A nun holds a rosary during a prayer service in St. Peter’s Square, as Pope Francis continues his hospitalization, at the Vatican, March 2, 2025.
Dylan Martinez/Reuters

Francis, who has led the Catholic Church since 2013, was admitted to Gemelli on Feb. 14 and was diagnosed with bilateral pneumonia.

The 88-year-old pontiff had been in stable condition on Saturday, church officials said, following a bronchospasm attack on Friday.

ABC News’ Youri Benadjaoud contributed to this report.

This is a developing story. Please check back for updates.