In 1997, guidelines for Swedish neonatologists attempting to resuscitate markedly depressed term infants were altered to provide for starting resuscitation with 40% oxygen rather than the previously accepted 100% oxygen. Most Swedish hospitals complied with the revised guideline; the few that did not provided an opportunity to compare the two regimens. Four perinatal level III centers provided data from the years 1998 to 2003 on 1223 live-born singleton term infants with birth weights appropriate for gestational age whose 1-minute Apgar score was less than 4. Infants with major malformations were excluded. Two of the centers used 100% oxygen, and two, 40% oxygen for resuscitation. Cesarean section rates were similar in the two treatment groups.
Neither nonparametric analysis nor analysis of covariance demonstrated any difference between the treatment strategies for 1- and 10-minute Apgar scores, but the mean 5-minute score was significantly higher for infants breathing 40% oxygen. Adjusting for possible confounding factors did not substantially alter these findings. Apgar scores increased more rapidly in the 40% oxygen group, but there was no difference 10 minutes after birth. A significant association was found between 100% oxygen treatment and a 5-minute Apgar score below 7; the odds ratio was 1.5. No significant differences between the treatment strategies were found in rates of neonatal death, hypoxic ischemic encephalopathy, or seizures. The study findings did not change when infants with meconium aspiration, sepsis, or pneumonia were excluded from analysis.
Resuscitating severely depressed term infants with 40% oxygen proved to be as efficient as using pure oxygen in this population-based register study. In addition, Apgar scores recovered more rapidly with 40% oxygen.