Reference intervals for end-tidal carbon monoxide of preterm neonates

OBJECTIVES We constructed reference intervals for end-tidal carbon monoxide (ETCOc) levels of neonates 28 0/7 to 34 6/7 weeks gestation in order to assess hemolytic rate. STUDY DESIGN This is a prospective four-NICU study in Bangkok, Thailand, and Utah, USA. RESULTS Of 226 attempted measurements, 92% were successful. Values from day 1 through 28 were charted and upper (>95th percentile) reference interval limits calculated. During the entire 28 days, the ETCOc upper reference intervals from babies in Bangkok were higher than those in Utah (p   0.1). Similar to term neonates, preterm neonates in Bangkok and Utah had higher ETCOc values during the first 48 h after birth than thereafter (p < 0.01). CONCLUSIONS Using this methodology, and the reference interval chart, the hemolytic rate of preterm infants ≥28 weeks can be assessed.