Prediction of respiratory distress syndrome by the microbubble stability test on gastric aspirates in newborns of less than 32 weeks' gestation

Aim: There is a need for a rapid method to identify infants who will develop respiratory distress syndrome (RDS) soon after birth, to allow early treatment of affected infants with surfactant. The microbubble stability test (MST) may be one such method, but clinical experience is sparse. Methods: The MST was performed on gastric aspirates from 188 infants with a mean gestational age of 29 (range 23-31) wk. Results: 87 infants developed moderate to severe RDS, corresponding to a prevalence of 46%. The sensitivity, specificity and predictive values for identification of infants with moderate to severe RDS were determined for the average diameter of bubbles, the proportion of microbubbles with different diameters and the total number of microbubbles. The proportion of microbubbles with diameters <20 or 25 put gave the best prediction, with a sensitivity of 78-79%, a specificity of 57-58%, a positive predictive value of 62% and a negative predictive value of 76%. Early treatment with nasal continuous positive airway pressure probably mitigated the development of RDS in some infants with a low-degree surfactant deficiency and this may explain the relatively low specificity. Conclusion: In infants of <32 wk gestation RDS can be predicted by computerized image analysis of the size distribution of microbubbles generated in gastric aspirates.