Vatican City (AFP) - Pope Francis suffered two new breathing attacks on Monday, requiring two separate bronchoscopies, the Vatican said, as the 88-year-old pontiff struggles to recover from pneumonia.

“Today, the Holy Father experienced two episodes of acute respiratory failure, caused by a significant accumulation of endobronchial mucus and consequent bronchospasm,” it said in a statement on Francis’s 18th day in hospital, the longest of his papacy.

In its usual evening update, the Holy See said the pope had resumed the use of an oxygen mask and noted that he was “alert, focused and cooperative”.

It added that Francis’s prognosis remains “reserved,” an indication that doctors cannot predict the likely outcome of his condition.

The Argentine pope was admitted to Rome’s Gemelli hospital on February 14 with bronchitis, which developed into pneumonia in both lungs, sparking alarm across the globe.

Despite “slight” incremental improvements in the pope’s condition last week, according to the Vatican, he suffered a setback on Friday with a bronchospasm that required him to use a “non-invasive mechanical ventilation”.

On Monday, with the two episodes of acute respiratory failure, the Vatican said two separate bronchoscopies were performed in order to “aspirate abundant secretions”.

Acute respiratory failure, which can be life-threatening, occurs when the lungs cannot pass enough oxygen into the blood, or when carbon dioxide builds up in the body.

A bronchoscopy is a medical procedure that allows doctors to view the air passages using a small camera at the base of a flexible tube, while also taking tissue samples.

- ‘All your affection’ -

On Sunday evening, the Vatican had said the condition of the leader of the world’s almost 1.4 billion Catholics was stable.

Francis, who has been pope since March 2013, had required the oxygen mask on Friday and Saturday, but not on Sunday, when he participated in mass and spent the rest of the day alternating rest with prayer.

The pope also on Sunday received Italian Cardinal Pietro Parolin, the Vatican’s secretary of state, and Edgar Pena Parra, a Venezuelan archbishop who is also a senior Vatican official.

The Jesuit is being treated in a special suite reserved for pontiffs on the 10th floor of the Gemelli, where the Vatican has said he has continued to work.

Francis, born Jorge Bergoglio, missed his traditional Angelus prayer for a third straight Sunday and the Vatican issued a written text instead.

In it, the pope thanked well-wishers for their prayers, saying: “I feel all your affection and closeness and, at this particular time, I feel as if I am ‘carried’ and supported by all God’s people. Thank you all.”

As pilgrims and other well-wishers continue to pray and leave offerings outside the hospital, medical experts, along with the Vatican itself, continue to warn that Francis is not out of danger and the path to recovery could be long.

This hospital stay is the fourth of his nearly 12-year papacy.

In recent years, he has had surgery on his colon, a hernia operation and pain in his knee and hip that have caused him to rely on a wheelchair.

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.

Francis has said he would be open to following his predecessor, Benedict XVI – who in 2013 stepped down because of his physical and mental health – were he unable to fulfill his functions as pope.

But before his recent hospitalisation he repeatedly had said it was not yet the time.