Stable Microbubble Test on Tracheal Aspirate for the Diagnosis of Respiratory Distress Syndrome

Abstract

Background: Exogenous surfactant should be used as early as possible in the presence of respiratory distress syndrome (RDS), but diagnosis may only become clear late in the course of the disease. The stable microbubble test (SMT) in the tracheal aspirates could help in the decision to give early surfactant to preterm babies with respiratory distress. Objectives: The objective of this study was to evaluate the accuracy of the SMT on tracheal aspirate for the diagnosis of RDS in newborns requiring mechanical ventilation. Methods: The test was performed on specimens obtained from 74 infants requiring mechanical ventilation, through routine suctioning. Results: Patients with RDS and meconium aspiration syndrome (MAS) had a significantly lower stable microbubble count than non-RDS and non-MAS patients. Preterm infants without RDS had a significantly higher microbubble count than preterm babies with RDS and a similar count to that of term babies. Considering a cutoff point of 120 microbubbles/mm² for the diagnosis of RDS, the sensitivity of the microbubble test was 96.3% (95% CI: 79.1–99.8) and the specificity 97.6% (95% CI: 85.9–99.9). Conclusions: The SMT on tracheal aspirates is accurate for RDS diagnosis and may be useful to support the decision to give surfactant to newborns on mechanical ventilation.