Pope Francis experienced a "sudden worsening of the respiratory picture" Friday, the Vatican said, when he had an "isolated crisis of bronchospasm," which is when the muscles that line the airways in the lungs tighten.

The episode caused the 88-year-old pope to inhale vomit, the Vatican said in a statement. Francis was treated with noninvasive mechanical ventilation had a good response, the Vatican said.

"The Holy Father has always remained vigilant and oriented, collaborating in therapeutic maneuvers," the Vatican said. "The prognosis therefore still remains reserved."

Earlier Friday, Vatican sources indicated to CBS News that the pope's health had improved, saying he was not currently in critical condition after exactly two weeks in hospital for bronchitis that developed into pneumonia in both lungs.

"The clinical picture remains complex, the criticality has subsided for the moment, but I would respect the caution of the doctors as the prognosis remains guarded," the sources said. There was no indication of how much longer the pontiff might remain hospitalized.

The Vatican has been providing brief updates on the pope's health twice daily, and he had been improving in recent days, but doctors said his condition remained critical until Friday.

A CT chest scan taken Tuesday evening showed the "normal evolution" of an infection as it is being treated. Blood tests have confirmed an improvement, according to the Vatican's update. The slight kidney insufficiency detected a few days ago has receded, and Francis is continuing to receive respiratory physiotherapy.

The bilateral pneumonia diagnosis given to the pope on February 18 would have been a worrying turn for any patient of his age, but it was of particular concern for the leader of the Catholic Church, who has long suffered from respiratory problems.

The pope has always kept a very busy schedule, and he appeared breathless at some of his public events earlier in the month before being admitted to the hospital on February 14 for what was first diagnosed as bronchitis.

People have been gathering outside Rome's Gemelli hospital to show their support, with many leaving messages and notes near a statue of former Pope John Paul II.

The Vatican has said Francis is thankful for the "closeness he feels" from his supporters, and that he asked for people to pray for him.

This is the pope's fourth hospitalization since he took over leadership of the Roman Catholic Church in 2013. He underwent significant abdominal surgery in 2021 and then had another procedure in 2023 to repair scar tissue and an abdominal hernia. He had been hospitalized briefly for treatment for pneumonia earlier that year.

As a young man in his home country of Argentina, Francis had part of one lung removed following a pulmonary infection, which left him vulnerable to respiratory illnesses.

The Vatican announced earlier this month that Francis wouldn't celebrate Sunday Mass at St. Peter's Basilica this year, due to his ongoing recovery. The pope's ongoing hospitalization comes just ahead of the start of the annual Christian observance of Lent. The 40-day Lenten period begins on Ash Wednesday, which this year falls on March 5.

Just before Easter last year, Francis declined to attend a Good Friday procession at Rome's Colosseum in a bid to conserve his health, but the pope later led tens of thousands of worshipers in Easter celebrations.