A chronic respiratory disease that often develops in extremely premature infants after lifesaving ventilator treatment can continue to plague them into adolescence and adulthood, California researchers reported recently.

Although most of the children are living relatively normal lives, the researchers are concerned that they may be susceptible to serious lung disease as they get older.

The report in the New England Journal of Medicine stems from a follow-up of very premature infants, born between 1964 and 1973, who were among the first generation to be saved from lethal respiratory distress syndrome by mechanical ventilators and supplemental oxygen therapy.

They averaged about 4 pounds at birth, and some weighed as little as 2 1/2 pounds. It has long been known that those who survived often developed a chronic lung disease after being placed for an extended period on a mechanical ventilator. But the study by Stanford University researchers is the first to document that the condition continues even after the babies are grown.

Although most of the problems are not currently serious, researchers who examined 26 of the patients wrote that "the measurable pulmonary dysfunction in this group causes concern about their susceptibility to progressive obstructive pulmonary disease as older adults."

The team was headed by William H. Northway Jr., who first described the chronic condition, labeled bronchopulmonary dysplasia, in 1967. He and others found that the condition, which is marked by reduced lung function and inflammatory changes in the lungs and airways, caused death in about 40 percent of affected infants.

"The initial thought was that if you lived, you got off scot-free," said Mary Ellen B. Wohl, chief of pulmonary medicine at Children's Hospital in Boston. But continuing studies on the original group of infants have demonstrated that the condition persists into childhood; the new study shows that it appears to be a lifelong problem.

She said it is not clear whether the ventilator treatment causes the chronic disease or whether the babies were afflicted before treatment.

The Stanford scientists said they set out to determine whether the premature babies would have normal pulmonary function as they grew into adulthood.

The examinations showed that only six of the patients had respiratory symptoms, but overall they were more likely to have had asthmatic wheezing, pneumonia and limited capacity for exercise. They also used more medications for breathing problems.