Ailing pope suffers breathing 'crisis', Vatican says
The episode came just hours after a Vatican source said the 88-year-old pontiff's condition was no longer considered critical, following a series of incremental improvements.
Francis, who has spent the past two weeks at Rome's Gemelli hospital, "presented an isolated crisis of bronchospasm which... led to an episode of vomiting with inhalation and a sudden worsening of the respiratory picture", the Vatican said in a statement on Friday evening.
"The Holy Father promptly underwent broncho-aspiration and began non-invasive mechanical ventilation, with a good response on gas exchange," it said.
Francis "remained alert and oriented at all times, cooperating with the therapeutic manoeuvres", it added.
His doctors said it would take the next 24 to 48 hours to see if this breathing trouble has worsened his condition or not, a Vatican source said.
The pontiff, who is "not out of danger", was using an oxygen mask that covers his nose and mouth but was "in good spirits", the source added.
He also responded better than others might have done in his condition, the source said.
The pope was hospitalised on February 14 for breathing difficulties but his condition deteriorated into pneumonia in both lungs, sparking alarm.
He suffered a breathing attack at the weekend but since then appeared to have been getting slightly better, with the Vatican releasing more optimistic medical updates.
It has not yet modified the pope's prognosis of "reserved", however, which means doctors will not predict changes in his health.
Still reserved
Medical experts have warned that Francis's age and the chronic respiratory disease from which he suffers mean a sustained recovery could take time.
The pope, head of the world's nearly 1.4 billion Catholics, had part of one of his lungs removed as a young man and has suffered increasing health problems in recent years.
He is prone to bronchitis and suffers from hip and knee pain which has made him reliant on a wheelchair.
Nonetheless, Francis has continued to work from the special hospital suite on the Gemelli's 10th floor.
He also has been doing breathing exercises in between resting and praying, according to the Vatican.
This hospital stay is the fourth of the Argentine's nearly 12-year papacy and the longest.
In recent years, he has had surgery on his colon and a hernia operation, as well as a previous stay in hospital with bronchitis.
There has been speculation as to whether Francis might now resign, especially as his schedule has been packed with papal duties amid celebrations for the holy Jubilee year.
"If the pope survives, many imagine that he will want to finish the Jubilee year but that afterwards, when he is 89, he will face the question of whether or not to resign," Italian Vatican expert Marco Politi told AFP.
But before his hospitalisation, Francis had repeatedly said it was not yet the time -- and may never be.