Experts say new pope would be unable to do strenuous exercise, but should have enough energy for papal schedule

The new pope has daunting challenges ahead ranging from the church sex abuse scandal to reinvigorating the flock. And Francis will have to do it all with just one lung.

The Argentinian pontiff lost the greater part of one lung to a teenage infection. "He feels it today," said his authorised biographer, Sergio Rubin. "He's a little bit slowed by it, but he's OK."

Doctors said that losing one lung did not necessarily compromise the pope's health or reduce his lifespan, though it means no strenuous exercise since he no longer has as much air capacity as people with two lungs.

"He probably wouldn't be able to run marathons, but I don't think that would be on his schedule," said Dr Peter Openshaw, director of the Centre for Respiratory Infection at Imperial College London. "Having one lung should be enough as long as there is no other disease in that lung."

Openshaw did not think a papal schedule would be too taxing for Francis's one lung, though he noted the pope's ribcage might look slightly unusual. "His x-ray will probably look rather alarming, but understandable once you know he only has one lung," he said.

Openshaw said Francis's existing lung would probably have expanded to fill the space left by the missing one, and that his ribcage would have shrunk slightly in size. His diaphragm may also have moved up slightly higher than normal. But none of those changes should affect Francis's normal activities, he said.

Experts said it would be rare nowadays to remove a lung. Antibiotics would be used to treat most lung infections including tuberculosis, though part of the organ might be removed to treat advanced lung cancer.

Back when Francis had his lung removed, the available antibiotics were not as powerful. "In the past, doctors used all kinds of strange things to try to treat lung infections," said Dr Jennifer Quint, a respiratory expert at London's School of Hygiene and Tropical Medicine. She said physicians even used to stick ping pong balls into people's lungs in an attempt to starve the lung of oxygen, to kill the bacteria.

Quint said the fact that Francis appears so fit and healthy at 76 bodes well for his future."If he were going to have any major complications from the surgery [to remove the lung], he would have had them by now," she said.

She said Francis's main challenge would be to keep his remaining lung healthy. "I would recommend a yearly flu vaccination and an occasional pneumonia vaccine to avoid infection," she said.

Openshaw agreed the pope's remaining lung should be able to compensate for the missing one, similar to how parts of the brain may pick up functions of other regions damaged by a stroke.

"The other lung can gain capacity but there will be limits," he said, comparing it to a car engine that now runs slightly more slowly. "You may not be able to accelerate as hard but it still works just as well."