Assessing the risks, benefits of oxygen therapies for preemies

A gentle oxygen-delivery technique is as effective as a more invasive one for treating very preterm infants, according to a new study. The researchers also found that slightly lower oxygen levels decrease the risk for eye damage but may raise the risk of death.

Very preterm infants – those born at 24 to 27 weeks of gestation instead of the full term of about 40 weeks – face a number of health challenges. Even with today's high-tech neonatal intensive care units, about 1 in 5 very preterm babies does not survive.

Extremely preterm babies are traditionally treated with an artificial surfactant – a viscous substance that helps keep the lungs' air sacs open – and a ventilator and to aid breathing. But a growing number of doctors have started to use a less-invasive method called continuous positive airway pressure (CPAP). A technique that's long been used for adults with sleep apnea, CPAP relies on a machine to blow air through a preterm infant's nostrils to gently inflate the lungs. Until now, the 2 techniques hadn't been compared in a large clinical trial. Also unknown was the ideal blood oxygen level for these newborns.

To explore the treatments, scientists at 20 medical centers enrolled 1,316 very premature infants in a 2-pronged study. The study received primary funding from NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), with additional support from NIH's National Heart, Lung and Blood Institute (NHLBI) and National Center for Research Resources (NCRR). The results were published in 2 separate papers in the 27 May 2010 issue of the New England Journal of Medicine.

In the first prong of the study, infants were randomly assigned to receive oxygen either by CPAP or by ventilation with surfactant. If infants in the CPAP group couldn't achieve adequate oxygen levels, they were placed on a ventilator. Of those who received CPAP initially, 83% required a ventilator tube in the windpipe, and 67% received surfactant.

The researchers found that, although the 2 therapies had nearly identical death rates and evidence of a lung disorder, children placed on early CPAP fared somewhat better by other measures. They had better survival rates and were less likely to need breathing therapy a week after birth. They were less likely to need steroid treatment for their lungs, and they spent less time overall on ventilators. Initial CPAP treatment also led to better survival rates for the earliest preterm infants, born at 24 to 25 weeks gestation.

In the study's second prong, infants were randomised to receive either a higher or lower target range for blood oxygen saturation. Higher oxygen levels had already been linked to an increased risk of retinopathy of prematurity, a potentially blinding eye condition.

The researchers found that about half as many infants in the lower oxygen group developed retinopathy of prematurity compared to those in the higher oxygen group (about 9% compared to 18%). However, more infants in the lower oxygen group died-about 20%-than in the higher level group (16%). The evidence suggests there may be 1 additional death for every 2 cases of severe retinopathy prevented.

"Balancing the benefits of supplemental oxygen against the risks in these very premature babies has been a concern of doctors and parents for decades," says NHLBI Acting Director Dr Susan B. Shurin. "The results of this large clinical trial will help inform management decisions to improve chances of survival and reduce complications associated with breathing problems in these vulnerable patients."

(Source: National Institute of Health: New England Journal of Medicine: June 2010)