A new modality using breath sound analysis to evaluate the control level of asthma.

BACKGROUND Reliable symptom assessment is essential in asthma management. We developed new technology for analyzing breath sounds and assessed its clinical usefulness for monitoring asthmatic children. METHODS Eighty asthmatic children and 59 non-asthmatic children underwent breath sound analysis in an asymptomatic state. Their asthma control was assessed by the Asthma Control TestTM or Childhood ACTTM scores and divided into two groups, namely, well-controlled (perfect) (n = 19) and not well-controlled (not perfect) (n = 61). Breath sounds were recorded using two sensors, located on the right anterior chest and trachea. We calculated the acoustic transfer characteristics between the two points, which indicated the relationship between frequencies and attenuation during breath sound propagation. Two indices of sound parameters, the chest wall sound index (CWI) and the tracheal sound index (TRI), were calculated from the transfer characteristics and tracheal sounds. We also developed a new parameter, the breath sound index (BSI), on a 2-dimensional diagram of CWI and TRI and tried to determine whether BSI may clarify asthma control better than CWI or TRI alone. RESULTS There was a significant difference in TRI and BSI between asthmatic and non-asthmatic children (p = 0.007, p < 0.001). There was a significant difference in CWI and TRI between the well-controlled and not-well-controlled groups (p < 0.001). BSI discriminated between the two groups accurately (p < 0.001). The sensitivity and specificity of BSI for asthma control were 83.6% and 84.2%, respectively. CONCLUSIONS Asthma control could be evaluated using a new index calculated from breath sound analysis.