VATICAN CITY (AP) -Pope John Paul II took his sense of humor into the operating room where he underwent a tracheotomy to relieve his breathing problems.

When doctors told the pope the Thursday operation would be a small one, the pontiff retorted: “Small! It depends for whom,” said Italian Cabinet Undersecretary Gianni Letta.

The top aide to Prime Minister Silvio Berlusconi who visited the pope said John Paul was “serene” after waking up from the anesthesia. The pope raised his hand and attempted to speak with doctors but was told not to try, Letta said told reporters at Gemelli Polyclinic Hospital in Rome.

Vatican spokesman Joaquin Navarro-Valls said the tracheotomy lasted 30 minutes and that the outcome was “positive.” The pope had approved the procedure, which he said, citing doctors’ accounts.

John Paul underwent the procedure Thursday night to insert a tube in his throat, hours after he was rushed back to the hospital for the second time in a month with flu-like symptoms of fever and congestion, the Vatican said.

The pontiff was conscious in his hospital room after the tracheotomy, breathing with the help of a respirator, the Italian news agency ANSA reported.

The frail, 84-year-old pontiff, who was taken to the hospital shortly before 11 a.m. in an ambulance, was to spend the night in his hospital room, Navarro-Valls said.

But the tracheotomy may require a longer hospital stay and have serious consequences for the pope’s abilities to carry out his duties since he will not be able to speak, at least initially, while the breathing tube is in his throat.

Medical experts said the respirator was a serious development. “The fact that he is on a respirator is not good. The fact that he was readmitted so quickly is not good. All this suggests there’s a serious problem,” said Dr. Michael Kaplitt, a Parkinson’s disease expert at New York Presbyterian Hospital/Weill Cornell Medical Center.

Before the tracheotomy, outside medical experts had said John Paul may have pneumonia. However, Navarro-Valls’ statement made no reference to pneumonia, saying the pope suffered a narrowing of his larynx.

President Bush, flying home from a European trip, said in a statement: “On behalf of all Americans, Laura and I send our heartfelt best wishes to Pope John Paul II. The Holy Father is in our thoughts and prayers and we wish him a speedy recovery and return to the service of his church and of all humanity.”

In recent days, the pope appeared to be recuperating from an illness that kept him in the hospital for 10 days earlier this month. On Wednesday, he gave a 30-minute audience by video hookup, reading a statement in six languages before waving and giving his blessing at the end.

With each successive appearance, he seemed a little stronger, a little more alert, and his voice rang out with greater clarity.

That made Thursday’s reversal all the more shocking for the faithful from Nigeria to the Philippines to St. Peter’s Square, and raised more doubts about his ability to carry on.

“We have prayed for the pope to live as long as possible so we can still share our joy with him,” said Zofia Gebala, a 73-year-old retiree, as she left a church in Wadowice, the pope’s birthplace in southern Poland. “We are praying for him every day, for his well-being. But it’s all in God’s hands now.”

Vanessa Animo Bono, 32, a Catholic being treated at Gemelli, expressed fear because of the pope’s recent treatment. “He is one of the few popes who is actually able to listen to people.”

Papal officials played down the seriousness of the hospitalization, saying a patient of the pope’s age is always at risk from the flu. Vatican aides said the pope had a fever and congestion in addition to the breathing problems.

ANSA reported the pope was conscious when he arrived at Gemelli and that he was sitting upright in a stretcher. According to the report, people who saw him enter the hospital said his face looked “quite relaxed.”

Earlier Thursday, Vatican officials had said the pope suffered from a “syndrome of influenza.”

Chile’s ambassador to the Holy See, Maximo Pacheco, told The Associated Press that the pope suffered a “bad relapse,” citing a conversation he had with the Vatican’s secretary of state, Cardinal Angelo Sodano.

But outside experts said people don’t get a relapse of influenza itself. Instead, flu can lead to a bacterial infection such as pneumonia or bronchitis, which is an inflammation of the tubes that carry air into the lungs, or to congestive heart failure, a treatable condition in which the heart is unable to pump enough blood to meet the body’s needs.

Thursday’s hospitalization was the pope’s eighth since his election in 1978.

The pope’s common touch and his willingness to travel to remote places, despite serious health problems that include knee and hip ailments, make him much loved among Catholics.

As with the previous hospitalization, the latest was certain to fuel speculation about whether he could continue as pope, and what would happen if he was incapacitated.

In the clearest sign that the Vatican may be taking the eventuality of papal resignation seriously, Vatican No. 2 Cardinal Angelo Sodano declined to rule out the possibility during John Paul’s first hospitalization this month, saying it was up to the pope’s conscience.

Thursday’s news spread quickly, with the pope’s illness flashed on television just as news shows were ending in the Philippines. Church officials relayed a prayer request to the faithful by text message on their cell phones.

Brigid Nolan, 73, saw the news on television in Dublin, Ireland, and walked to St. Columba’s church. She lit a candle and offered a five-minute prayer for the pope and her own struggle with Parkinson’s.

“I do draw inspiration from his own fight for life,” she said. “He is suffering, but he’s surviving, and more power to him. I get angry when people say he should quit. He should keep going for every minute God gives him.”

Tourists and pilgrims in St. Peter’s Square expressed alarm.

“I’m sure he wants to return to the Vatican because he has spent so much time there,” said Ornella Lisandrello, 29, an Italian physician. “I’m sure he would like to die at the Vatican.”

In the pope’s hometown of Wadowice, worshippers offered prayers at St. Mary’s church, where the young Karol Wojtyla was baptized.

“This is a very emotional moment for me,” said Zdzislaw Szczur. “His suffering really moves me. It’s all God’s providence now.”

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