Lung sound analysis in infants with risk factors for asthma development

Background and objectives Using a lung sound analysis, the prognosis of asthma was investigated in infants with risk factors for asthma development by a long-term observation. Methods A total of 268 infants were included (median age: 8 months old). The lung sound parameters (the ratio of the third and fourth area to the total area under the curve [A(3)/A(T) and B-4/A(T)], and the ratio of power and frequency at 50% and 75% of the highest frequency [RPF50 and RPF75]) were evaluated at the first visit. At 3 years old, using a questionnaire, we examined the relationship between the lung sound parameters and risk factors of asthma development. Results Among the 268 infants, 175 infants were in good health and 93 had a history of acute respiratory infection (ARI) within 7 days at the first visit. Among the 3- to 12-month-old infants with an ARI, the A(3)/A(T), B-4/A(T) values in those with a history of asthma/asthmatic bronchitis, atopic dermatitis, and atopy were smaller than in the infants without such histories. Among the 13- to 24-month-old infants with an ARI, the A(3)/A(T) and B-4/A(T) values in those with a wheezing history were larger than in the infants without such a history. Conclusions The characteristics of the lung sounds in infants with risk factors for asthma development were demonstrated over long-term follow-up. Lung sound analyses may be useful for assessing the airway condition of infants.