A Lung Sound Analysis in Infants with Risk Factors for Asthma During Acute Respiratory Infection

The parameters of lung sounds have been suggested as biomarkers of airway changes. Using a commercially available lung sound analyzer, we investigated the characteristics of the lung sounds in infants with acute respiratory infection (ARI). Infants with ARI who were 6 to 18 months of age were included in this study. The lung sound parameters, the ratio of the third area and fourth areas to the total area under the curve of the sound spectrum (A₃/A_T and B₄/A_T), and the ratio of power and frequency at 75% and 50% of the highest frequency of the power spectrum (RPF₇₅ and RPF₅₀) were evaluated. With an original Japanese questionnaire based on American Thoracic Society-Division of Lung Disease, the risk factors of asthma development in infants were examined. One hundred ten infants with ARI and 248 infants in good health for comparison were included. All infants were completely analyzed, and then divided into 2 age groups for a stratification analysis (6-12 and 13-18 months). In the overall analysis, among infants with a history of wheezing, recurrent wheezing, allergy, and atopic dermatitis, the values of RPF₅₀ of infants with ARI were significantly lower compared with those without ARI. In the 6- to 12-month-old group, the RPF₅₀ values of atopy-positive infants with ARI were lower compared with those without ARI (P = 0.003). The lung sounds of the infants with asthma-developing risk factors were more affected by ARI than those of infants without risk factors. Analyzing the changes in the lung sounds induced by ARI may be useful for evaluating the characteristics of the airways in infants.