In the early 1960s, 50,000 babies a year died because they were born without a chemical substance necessary for proper lung function. Today, thanks to one Harvard researcher, such infants' chances for survival have more than doubled.

Mary Ellen Avery, Rotch professor of pediatrics at Harvard Medical School, was awarded a National Medal of Science in September for her work with pulmonary surfactant, the chemical substance lining the air spaces in the lungs and preventing their collapse.

The medal, presented by President Bush, is considered the most prestigious science award in the country.

During her career, Avery has worked to understand and come up with treatments for infants with respiratory ailments.

The neonatologist's first paper on the subject, co-written by Harvard colleague Jere Mead '43, was published in 1959. In the paper, the authors studied the surface tension of lung extracts prepared from babies with hyaline membrane disease, which causes respiratory distress syndrome (RDS) and often leads to death.

The researchers found that the surface tension of these extracts was consistently higher than that of extracts prepared from infants without the disease.

Avery and Mead concluded that something which regulates surface tension in the lung must be absent in those babies with hyaline membrane disease. If unregulated, surface tension causes alveoli--the air-carrying sacs of lungs--to collapse, followed by the collapse of the lungs.

At this point, scientists began investigating the differences in the infants' lungs, and specifically what in their composition might be affecting surface tension, says Avery.

This interest was sparked, she says, by the high death rate of premature infants with RDS.

"The first breath is the most difficult breath you ever take," she says. The differences in air pressure between the atmosphere and the newly born infant's lung, which is airless, create this difficulty. In infants with RDS, breathing is even harder.

Normally, says Avery, the lung contains a constant residue of oxygen, even on exhaling. But in infants with RDS, the lung does not contain this residue, and breathing remains difficult.

With further study, Avery discovered that these premature infants did not have normal amounts of the chemical surfactant. By 1980, the genetic process involved in producing the substance as well as the cell production sites in the lung had been isolated.

These findings, as well as work that Avery performed showing that administration of surfactant in the lamb fetus accelerated lung growth, set the stage for clinical trails of the substance.

Tetsoro Fujiwara, a Japanese researcher, began surfactant replacement therapy in infants, the results of which were reported in 1980. Fujiwara was able to achieve success in this therapy through the use of calf-lung surfactant administered as a liquid into the trachea.

Clinical trials sponsored by the National Institutes of Health, as well as two U.S. drug companies, Ross Laboratories and Burroughs Wellcome, have resulted in two Food and Drug Administration approved surfactants as of this fall.