Lung Ultrasonography Score to Evaluate Oxygenation and Surfactant Need in Neonates Treated With Continuous Positive Airway Pressure

Abstract

Importance: Lung ultrasonography (LUS) is a bedside technique useful to diagnose neonatal respiratory problems, but, to our knowledge, no data are available about its use for monitoring lung function or eventually guiding surfactant therapy.

Objective: To determine the diagnostic accuracy of a neonatal-adapted LUS score to evaluate oxygenation and predict need for surfactant administration.

Design, setting, and participants: Prospective diagnostic accuracy study following STARD (Standards for the Reporting of Diagnostic Accuracy Studies) guidelines at a tertiary level academic neonatal intensive care unit in 2014. All neonates admitted to the neonatal intensive care unit with signs of respiratory distress were eligible, and 130 neonates were enrolled. The LUS score was calculated in the first hours of life under continuous positive airway pressure. The transcutaneous partial pressure of oxygen (Ptco2) to fraction of inspired oxygen (Fio2) ratio, alveolar-arterial gradient, oxygenation index, and arterial to alveolar ratio were calculated within 30 minutes from LUS, using transcutaneous blood gas monitoring. Surfactant was administered according to 2013 European guidelines.

Main outcomes and measures: Correlation between LUS score and indices of oxygenation and prediction of surfactant administration.

Results: Among the 130 neonates in this study, the LUS score was significantly correlated with all indices of oxygenation, independent from gestational age (GA) (Ptco2 to Fio2 ratio: GA ≥ 34 weeks: ρ = -0.57; GA <34 weeks: ρ = -0.62; P < .001; alveolar-arterial gradient: GA ≥ 34 weeks: ρ = 0.62; GA <34 weeks: ρ = 0.59; P < .001; oxygenation index: GA ≥ 34 weeks: ρ = 0.63; GA <34 weeks: ρ = 0.69; P < .001; and arterial to alveolar ratio: GA ≥ 34 weeks: ρ = -0.60; GA <34 weeks: ρ = -0.56; P < .001). The LUS score predicted the need for surfactant better in preterm babies with a GA less than 34 weeks (area under the curve = 0.93; 95% CI, 0.86-0.99; P < .001) than in term and late-preterm neonates with a GA of 34 weeks or greater (area under the curve = 0.71; 95% CI, 0.54-0.90; P = .02); the areas under the curve for these 2 GA subgroups are significantly different (P = .02). In babies with a GA less than 34 weeks, a LUS score cutoff of 4 predicted surfactant administration with 100% sensitivity and 61% specificity, yielding a posttest probability of 72%.

Conclusions and relevance: The LUS score is well correlated with oxygenation status in both term and preterm neonates, and it shows good reliability to predict surfactant administration in preterm babies with a GA less than 34 weeks under continuous positive airway pressure.