Helping Newborns Breathe Easier

Scientists have long believed that fluid is squeezed out of the newborn lung by passage through the birth canal. But UNC-CH researchers have helped dispel that idea--instead they found that a sodium channel drains the lung liquid into the bloodstream.

Pierre Barker, research assistant professor of pediatrics, and other Carolina researchers, including Richard Boucher, professor of medicine, and John Gatzy, professor of pharmacology, discovered which gene controls the sodium channel in the lungs of genetically altered mice.

The research opens the possibility of new strategies for treating respiratory diseases caused by premature birth. "If you don't have this channel at the point of birth you can't clear all the liquid that is present during fetal life, and you basically drown," Barker says.

During labor, the sodium channel drains about half of the liquid in a baby's lungs. The stress of labor raises fetal levels of adrenaline, which helps opens the channel. After birth, absorption continues and the channel drains most of the remaining liquid within hours.

Barker and his colleagues affirmed most researchers' belief that hormones control liquid absorption in the lungs. They previously identified the controlling agents as thyroid and steroid hormones. By extrapolating from animal studies , Barker thinks that babies born before 30 weeks lack the hormones that produce the channel and therefore lack enough of the channels to drain the lungs properly.

In addition to providing a better understanding of basic human physiology, the study helps to explain the relationship between premature birth and respiratory distress syndrome (RDS), a major killer of premature babies.

"We assume RDS babies have defective water transport in their lungs. The study offers us a credible additional hypothesis as to what causes RDS," Barker says.

RDS is normally treated by introducing artificial surfactants, chemicals that allow infants' lungs to expand by reducing the surface tension of pulmonary fluids.

"Surfactant has cut the mortality rate by about half. But the very premature babies are still dying from RDS," Barker says. "This study allows us to focus on another mechanism to try to treat this condition."

-- Colleen Haikes