Introduction:The reliability of a breath sound analysis using an objective method in infants has been reported.Objective: Breath sounds of infants with respiratory syncytial virus (RSV) acute bronchiolitis were analyzed via a breath sound spectrogram to evaluate their characteristics and examine their relationship with the severity. Subjects and Methods:We evaluated the inspiratory and expiratory breath sound parameters of 33 infants diagnosed with RSV acute bronchiolitis. The sound powers of inspiration and expiration were evaluated at the acute phase and recovery phase of infection. 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 as well as the expiration-to-inspiration sound ratio in the mid-frequency (E/I MF) was increased in the acute phase and decreased during the recovery phase.The E/I MF was inversely correlated with the SpO 2 and positively correlated with the severity score. Conclusion:In infants with RSV acute bronchiolitis, the sound power of respiration was large at the acute phase, significantly decreasing in the recovery phase. In 61% of participants, nonuniform, granular bands were shown in the low-pitched region of the expiratory spectrogram.

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