Pope Francis remains stable and prognosis reserved, Vatican says

ROME -- Pope Francis' condition remained stable on Tuesday, and his prognosis remains reserved, according to the Vatican.

The pope had needed medical intervention amid two episodes of "acute respiratory failure" on Monday, Vatican sources told ABC News.

The pope did not have any episodes of respiratory failure or bronchospasm on Tuesday, according to the Vatican.

Pope Francis has remained "alert, cooperating with therapy and oriented," the Vatican's press office, the Holy See, said. He underwent "high-flow oxygen therapy and respiratory physiotherapy" on Tuesday, the Vatican said.

He will resume noninvasive mechanical ventilation overnight and into Wednesday morning, "as planned," according to the Vatican.

The pope, 88, was taken off noninvasive mechanical ventilation and resumed receiving supplemental oxygen through a nasal tube, Vatican sources said Tuesday. He was no longer wearing a mechanical ventilation mask, a device that pumped oxygen into his lungs, the sources said.

The Holy See had earlier on Tuesday said the pontiff "slept all night" and that "now he continues his rest."

The episodes on Monday were caused by a "significant accumulation of endobronchial mucus and consequent bronchospasm," the Vatican said.

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.

The pope's prognosis "remains reserved," the Vatican said in its Monday evening update.

Francis, who has led the Catholic Church since 2013, was admitted to Rome's Gemelli Hospital on Feb. 14 and was diagnosed with bilateral pneumonia. The pontiff had a bronchospasm attack on Friday, church officials said.

ABC News' Youri Benadjaoud contributed to this report.

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