Introduction
During the COVID-19 epidemic, Japan experienced an unprecedented
outbreak of respiratory syncytial virus (RSV) in the summer of 2021 like
other nations1), and many infants who visited
hospitals were diagnosed with acute bronchiolitis. Acute bronchiolitis
caused by RSV is a common disease in infants, but some cases are turned
severe2). Furthermore, infants who have the
RSV-induced acute bronchiolitis suffer from subsequent episodes of
recurrent wheezes at a constant rate3). According to
the recent reports, RSV-induced acute bronchiolitis is considered to be
a trigger for the onset of childhood asthma4), and
there is some concern that it may have a significant impact on the
future respiratory function of patients5).
Of note, no specific treatment for acute bronchiolitis has been
established. Although the efficacy of inhaled β2agonists, adrenaline and hypertonic saline and systemic steroids
continues to be discussed6, 7), no satisfactory
conclusions with clinical efficacy have yet been obtained. One serious
problem concerning therapy for acute bronchiolitis is the difficulty of
assessing the severity of acute bronchiolitis in the acute
phase8), which is related to the difficulty in
performing objective lung function tests, such as a spirogram, due to
patient tolerance issues, as acute bronchiolitis typically has an onset
under two years of age9).
Recently, the utility of a breath sound analysis as a simple, safe and
non-invasive lung function test has been studied, and technological
progress in this field has been remarkable10, 11).
Clinically, current reports have suggested that new breath sound
analyses can be used in the clinical evaluation of airway
changes12), and have evaluated the lung function using
breath sound analyses in children13). The possibility
to objectively evaluate the airway condition in infants has also been
reported 14, 15). In the present study, we have
examined the characteristics of breath sounds in infants under two years
old with RSV-induced acute bronchiolitis and investigated the
relationship between various breath sound parameters and the severity
scores and clinical symptoms in these patients.