Researchers, led by a team at the University of Leicester, have put forward a theory based on research evidence that new alveoli are constantly being formed, challenging existing medical understanding that our lungs are completely formed by the age 3.

“It was believed that there was no further increase in the number of alveoli beyond that age, and that the existing alveoli just expanded as the lungs grew bigger until final adult size was reached,” said Manjith Narayanan, one of the study leaders from Leicester. “Our study challenged this by suggesting that new alveoli continue to be formed as the lung grow.”

The study appears in the American Journal of Respiratory and Critical Care Medicine.

The researchers studied over 100 healthy volunteers aged between 7 and 21 years. Each volunteer had a range of breathing tests and then a special magnetic resonance (MR) scan, during which they breathed in hyperpolarized helium and held their breaths.

“The helium is hyperpolarized, which means that the molecules all line up in one direction and it then behaves like a magnetized gas. Within the scanner, we can measure how the magnetism decays, and this in turn depends on the size of the air sacs—alveoli—which contain the helium,” said Narayanan.

Studying both small children, whose lungs contain approximately 1 liter of air, and adults with 4-liter lung volumes, the researchers found little difference in the size of the alveoli across the participants. According to Caroline Beardsmore, study author and senior lecturer at Leicester, “If the size of the alveoli are hardly changing, this can only mean one thing—as our lungs increase in size, we must be growing new alveoli.”

According to the study’s authors, the findings mean there is potential for lung repair following injury.

Source: University of Leicester