Evaluation of surfactant function at birth determined by the stable microbubble test in term and near term infants with respiratory distress.

UNLABELLED: Surfactant function using the stable microbubble test (SMT) was investigated in term or near term infants with respiratory distress. Newborn infants > or = 34 weeks gestation with an initial clinical hypothesis of transient tachypnoea of the newborn (TTN) needing supplemental oxygen and controls were included. Gastric aspirates were collected immediately after birth for SMT. The first chest X-ray films were examined by three independent radiologists and according to their interpretation the babies were divided into a TTN, a respiratory distress syndrome of the newborn (RDS), or a poorly-defined X-ray group. A total of 32 infants with respiratory distress and 32 controls with similar gestational age and birth weight were studied. The median and interquartile range (IQR) of the stable microbubble (SMB) count was significantly lower (P < 0.001) for the respiratory distress group than for the control group (17; range 6-33 versus 120; range 79-275). The proportion of babies with less than 35 stable microbubbles/mm2 (SMB/mm2) was significantly different for the whole respiratory distress group (24/32-75%) and for the TTN (9/13-69%), the RDS (5/5-100%), and the poorly-defined (10/12-83%) groups as compared with the controls (2/32-6%; P < 0.05). A total of 24/26 babies (92%) who needed oxygen for > or = 24 h but only 1/6 (17%) of them who needed < 24 h had a bubble count of less than 35 SMB/mm2 (P < 0.05).

CONCLUSION: the results suggest that deficiency or dysfunction of the surfactant system is involved in the majority of cases of respiratory distress in near term and possibly term babies. The stable microbubble test can enable clinicians to take an earlier decision to give surfactant to term or near term infants with more severe and progressive respiratory distress.