Gastric shake test and pharyngeal lecithin/sphingomyelin ratios in new born infants.

: Gastric shake test and pharyngeal lecithin/sphingomyelin ratios were measured in newborn infants with respiratory difficulties, and in low birth weight infants in the immediate neonatal period. Both tests were useful in distinguishing infants with idioathic respiratory distress syndrome from those with respiratory difficulty due to other causes. However, in six infants with idiopathic respiratory distress syndrome, the pharyngeal lecithin/sphingomyelin ratio indicated mature lungs, and in three of these, the gastric shake test showed the presence of surfactant. Five of these six infants had been delivered by emergency lower segment caesarean section because of maternal complications, which might account for the discrepancy between the laboratory results and the clinical condition of the patient.