Doctors said it would take a day or two to evaluate how and if the Friday afternoon episode impacted Francis’ overall clinical condition. His prognosis remained guarded, meaning he wasn’t out of danger.

In its morning update on Saturday, the Vatican said the 88-year-old pope didn’t have any further respiratory crises overnight: “The night has passed quietly, the pope is resting.” He had coffee in the morning for breakfast, suggesting that he was not dependent on a ventilation mask to breathe and was still eating on his own.

In the late Friday update, the Vatican said Francis suffered an “isolated crisis of bronchial spasm,” a coughing fit in which Francis inhaled vomit, that resulted in a “sudden worsening of the respiratory picture.” Doctors aspirated the vomit and placed Francis on noninvasive mechanical ventilation.

The pope remained conscious and alert at all times and cooperated with the maneuvers to help him recover. He responded well, with a good level of oxygen exchange and was continuing to wear a mask to receive supplemental oxygen, the Vatican said.

The episode, which occurred in the early afternoon, marked a setback in what had been two successive days of increasingly upbeat reports from doctors treating Francis at Rome’s Gemelli hospital since February 14.

The pope, who had part of one lung removed as a young man, has lung disease and was admitted after a bout of bronchitis worsened and turned into pneumonia in both lungs.

Doctors say the episode is alarming

The Vatican said the episode was different from the prolonged respiratory crisis on February 22, that was said to have caused Francis discomfort.

Dr. John Coleman, a pulmonary critical care doctor at Northwestern Medicine in Chicago, said the isolated episode Friday as relayed by the Vatican was nevertheless alarming and underscored Francis’ fragility and that his condition “can turn very quickly”.

“I think this is extremely concerning, given the fact that the pope has been in the hospital now for over two weeks, and now he’s continuing to have these respiratory events and now had this aspiration event that is requiring even higher levels of support,” he told The Associated Press.

“So given his age and his fragile state and his previous lung resection, this is very concerning,” added Coleman, who is not involved in Francis’ care.

Dr. William Feldman, a pulmonary specialist at Brigham and Women’s Hospital in Boston, said it was a good sign that the pope remained alert and oriented during the episode, but concurred that it marked “a worrying turn.”

“Often we will use noninvasive ventilation as a way of trying to stave off an intubation, or the use of invasive mechanical ventilation,” Feldman said.

Types of noninvasive ventilation include a BiPAP machine, which helps people breathe by pushing air into their lungs. Doctors will often try such a machine for a while to see if the patient’s blood gas levels improve so they can eventually go back to using oxygen alone.

Friday’s statement said Francis showed a “good response” to the gas exchange using the ventilation.

Doctors did not resume referring to Francis being in “critical condition,” which has been absent from their statements for three days now. But they say he isn’t out of danger, given the complexity of his case.