The 88-year-old pontiff has been hospitalised since 14 February with pneumonia in both lungs and breathing difficulties.
The Vatican said Tuesday that Pope Francis was resting after suffering further setbacks in his fight against double pneumonia.
“The pope slept through the night, now rest continues,” the Vatican said.
On Monday night two new acute respiratory crises required Francis to resume using noninvasive mechanical ventilation to breathe.
Doctors at the Agostino Gemelli Polyclinic in Rome, where the 88-year-old pope is being treated, said they removed "copious" secretions of mucus from his lungs by inserting a camera-tipped tube into his airways and using a sucker at the tip to remove the fluid.
According to medical experts, doctors often use noninvasive ventilation to stave off intubation or the use of invasive mechanical ventilation.
Given that the pope's laboratory tests didn't reveal any new bacteria, the Vatican said the mucus was his body's response to the initial pneumonia illness rather than a new one.
Cautious outlook
Francis remained alert, oriented and cooperated with medical personnel, the Vatican said.
His prognosis is however classified as "guarded", meaning he is not out of danger.
Doctors didn’t say if he remained in stable condition, although they referred to the crises in the past tense — suggesting they were over.
The crisis was a new setback in the Pope's fight to recover from a complicated respiratory infection, which has lasted more than two weeks.
Pope Francis, who uses a wheelchair, has chronic lung disease and had part of one lung removed as a young man.
To enhance his lung function, the pope has been receiving respiratory physiotherapy. The build-up of secretions in his lungs, however, indicated that he lacked the muscular strength to cough up enough fluid, according to doctors treating him.
No images or videos of him have been made public by the Vatican since he was admitted to the hospital on 14 February.
Francis' hospitalisation has been his longest absence to date in his 12-year papacy.