Utility of Lung Ultrasound in Diagnosis of Respiratory Distress Syndrome in Neonates: A Cross-sectional Study

Introduction: Respiratory Distress Syndrome (RDS) is one of the most common conditions leading to significant morbidity and mortality. Early diagnosis with a non-invasive imaging tool such as ultrasound, with no radiation hazard will be beneficial for timely intervention in neonates. Aim: To evaluate the utility of Lung Ultrasound (LUS) in diagnosing RDS in neonates and to compare it with chest X-ray (CXR). Materials and Methods: A cross-sectional study was conducted at a tertiary care hospital in Department of Pediatrics, AJ Institute of Medical Sciences, Mangalore, Karnataka, India, from June 2017 to December 2018. Forty neonates (preterm and term) admitted to Neonatal Intensive Care Unit (NICU) with symptoms of respiratory distress within six hours of life and fulfilling clinical criteria of RDS were included in the study. CXR and LUS were performed and interpreted by the same radiologist. The disease was graded as mild and severe by LUS based on the indices like B (Beam like comet-tail pattern) lines, alveolar consolidation, air bronchogram and white lung and it was compared with CXR in terms of sensitivity and specificity to diagnose RDS. Data were statistically analysed using Kendall’s tau-b test. Results: Eighteen (45%) neonates were <32 weeks, 19 (47%), between 32-34 weeks and 3 (7.5%) were >34 weeks of gestation. Twenty-six (65%) were males and 14 (35%) were females. Mean gestational age of the study cohort was 32±2 weeks. Mean birth weight in the study group was 1.7±0.5 kg. 14 out of the 40 neonates (65%) received steroids prior to delivery. LUS detected signs of RDS in all the 40 cases (100% sensitivity). Sixteen out of 40 (40%) neonates were graded as mild RDS and 24 out of 40 neonates (60%) as severe RDS. The sensitivity to detect severe cases was 100% when compared to CXR but specificity to detect mild cases was found to be 59%. The Positive Predictability Value (PPV) was found to be 54% and the Negative Predictable Value (NPV) was found to be 100%. Conclusion: LUS can be used as a reliable, bed side screening tool for the early diagnosis of RDS in NICU without side-effects of radiation.