The treatment showed some benefits in one study, but proved not to aid in development of healthy lungs.
By TRAN M. PHUNG
CHICAGO -- Adding fuel to a debate over whether breathing nitric oxide can benefit premature infants, two new studies appearing Thursday in the New England Journal of Medicine reached contradictory conclusions.
University of Chicago researchers found that infants who had received small amounts of nitric oxide to treat underdeveloped lungs were less likely to have delayed mental development or disability two years later.
But a study by the National Institute of Child Health and Human Development, which looked at babies with more severe lung impairment, found that those who inhaled nitric oxide and those who did not were equally likely to die or to develop chronic lung disease.
Some experts said the NICHD results demonstrated that nitric oxide is still an unproven therapy for premature babies. But Dr. Michael Schreiber, a leader of the university study, believes his team showed the therapy might someday benefit some preterm babies with mild lung damage.
"Nitric oxide helps a certain group of premature babies -- which exact babies it will help, we do not know yet," Schreiber said. "It does not appear to help the really critical ones, but the babies with a moderate amount of lung disease, it does help."
Nitric oxide, not to be confused with nitrous oxide or "laughing gas," naturally occurs in the body and helps aid blood flow.
The U.S. Food and Drug Administration has approved nitric oxide for treating full-term babies with respiratory problems that require mechanical ventilation. The nitric oxide helps the lungs absorb oxygen more easily by making the blood vessels in the lungs relax.
The Chicago researchers found that 46 percent of premature babies who were not treated with nitric oxide had developmental disabilities, including blindness, hearing loss and cerebral palsy. Those who were treated were half as likely to develop those problems. The same researchers reported two years ago that the nitric oxide group was less likely to develop chronic lung disease than the control group -- a result now disputed by the institute's study.
Sara Ramos, one of the first recipients of the therapy at the University of Chicago, attended a news conference Wednesday with her parents. Six years after receiving nitric oxide, she is excelling in kindergarten and loves physical activities. Her development may have been assisted by the treatment, though there's no way to know for sure.
The institute team studied infants at high risk of death from severe lung disease, for whom the nitric oxide was a last-resort therapy. About half of the babies in both groups died. Overall, administering nitric oxide did not improve their fragile lungs.
But the institute study's results pointed to a possible benefit for infants with less lung damage. Babies who weighed more than 2.2 pounds had decreased mortality and chronic lung disease with nitric oxide, while infants weighing less had increased risk of cranial bleeding and death. Those results were preliminary, the authors said.
According to Dr. Krisa Van Meurs, the lead investigator in the institute study, "at this point, nitric oxide use should be used only within clinical trials until we can determine who will benefit."