The 88-year-old pontiff suffered a constriction of his respiratory airways on Friday, akin to an asthma attack, renewing concerns over his well-being.
However, in a more upbeat readout on Saturday, the Vatican said the Pope did not have a fever and did not show signs of an increased white blood cell count, adding that his blood flow and circulation remained stable.
An elevated white blood cell count often indicates the presence of an active infection or inflammation.
"The Holy Father's clinical condition remained stable," the Vatican said, adding that the prognosis was still guarded, meaning he was not yet out of danger.
The Vatican said that for a second day running the Pope required non-invasive, mechanical ventilation, alternating between this and "long periods of high-flow oxygen therapy".
The Pope was continuing to eat and was always vigilant, the statement said.
Francis was admitted to Rome's Gemelli hospital on February 14 with severe respiratory problems that swiftly degenerated into double pneumonia - a serious infection in both lungs that can inflame and scar them, making it difficult to breathe.
He last suffered what the Vatican described as a "prolonged asthma-like respiratory crisis" on February 22 but there had not been any repeat crises until Friday.
Francis has experienced several bouts of ill health over the last two years and is prone to lung infections because he had pleurisy as a young adult and had part of one lung removed.
The Pope has not been seen in public since entering hospital, his longest absence from view since his papacy started in March 2013, and his doctors have not said how long his treatment might last.
As expected, the Vatican said that for a third week running, the Pope would not lead his usual Sunday prayers with pilgrims and that once again the text of the Angelus prayer would be published rather than read out.
Francis' hospitalisation has come as the Vatican is marking its Holy Year that is drawing pilgrims to Rome from all over.
They are walking through the Holy Door at St Peter's Basilica and also making pilgrimages to the hilltop Umbrian town of Assisi, to pray at the home of Francis' namesake, St Francis.
"Every day we're praying for the Pope," said the Reverend Jacinto Bento, a priest visiting Assisi on Saturday with a group of 30 Jubilee pilgrims from the Azores Islands.
"We're very sad for his situation."
Veronica Abraham, a catechist and Argentine native, came to Assisi on Saturday with her two children and other kids from her parish on Lake Garda and said the group had prayed for the Pope at every church they had visited.
"I'm sure that he's hearing our prayers, that he feels our closeness," she said.
with Reuters
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