Breath sound analyses of infants with respiratory syncytial virus-induced acute bronchiolitis

Abstract

Introduction: The reliability of breath sound analysis using an improved method in infants has been reported. Objective: Breath sounds of infants with respiratory syncytial virus (RSV)-induced acute bronchiolitis were analyzed to evaluate their specificity and examine their relationship with the severity. Subjects and methods: We evaluated the inspiratory and expiratory breath sound parameters of 33 infants (median age=2 months old) diagnosed with RSV-induced acute bronchiolitis. The sound powers of inspiration and expiration and the spectrum curve indices (ratio of the third and fourth area to the total area under the curve and ratio of the power and frequency at 50% and 75% of the highest frequency were evaluated at the acute phase and recovery phase. Furthermore, the relationship between the breath sound parameters and the clinical severity of acute bronchiolitis was examined. Results: Analyses of the breath sound spectrogram showed that the power of expiration at the acute phase was large, and was the expiration-to-inspiration sound power ratio in a mid-frequency range (E/I MF), with values decreased in the recovery phase. Data of the inspiratory sound spectrum curve showed the improvement of airway stenosis during the recovery period. Furthermore, there were significant relationships between the E/I MF and SpO2 and the severity score of acute bronchiolitis. Conclusion: In RSV-induced acute bronchiolitis, specificity of breath sounds was observed in the expiration sound and the reversible airway stenosis was evaluated. Breath sound analyses are expected to be useful for the diagnosis and clinical evaluation of the severity of acute bronchiolitis.