ST. PAUL, Minn. (AP) _ A 3-month-old boy who ''could not possibly have survived with any conventional technology,'' was released from a hospital Monday after his life was saved by a 91-hour hookup to an artificial lung machine.

Tony Waldo, who has fully recovered from a severe viral lung infection, is one of only 10 children in the world over one month old who have been treated in such a way on a lung machine, said Dr. John Tilelli, a critical-care physician at St. Paul Children's Hospital who treated the boy.

''Tony has 70 years ahead of his normal, productive life. He's a miracle baby,'' said Dr. Richard Gehrz, another of Tony's physicians.

The infant was hospitalized after the millions of tiny air sacs in his lungs had become so inflamed by respiratory syncytial virus infection that they no longer could put oxygen into his bloodstream. On March 21, Tony underwent surgery to connect his blood system to the artificial lung to take the place of his own lungs and give them time to heal.

The machine fed oxygen to his red blood cells and removed carbon dioxide before his blood was returned to his heart.

Later, his own lungs, aided by a conventional respirator, helped as his body weaned itself from the artificial lung, which was removed April 24. The respirator was disconnected April 8.

''He could not possibly have survived with any conventional technology,'' Gehrz said.

''Everything went so fast - bad news, bad news, bad news. Then bad news, good news, bad news, good news, good news,'' said Tony's mother, Mary Beth Waldo, of River Falls, Wis.

Mrs. Waldo and her husband Joseph picked up their son Monday morning.

In the past few years, the artificial lung has been used to help about 120 newborns throughout the world and 90 have survived, said Tilelli. But he said most of the newborns had problems such as immature lungs that were relatively easy to help, rather than infection.

Total medical costs, most covered by insurance, were about $125,000. About $5,000 of that was directly attributable to the artificial lung, Gehrz said.