Use of tracheal auscultation for the assessment of bronchial responsiveness in asthmatic children

Background - It can be difficult to assess bronchial responsiveness in children because of their inability to perform spirometric tests reliably. In bronchial challenges lung sounds could be used to detect the required 20% fall in the forced expiratory volume in one second (FEV(1)). A study was undertaken to determine whether a change in lung sounds corresponded with a 20% fall in FEV(1) after methacholine challenge, and whether the occurrence of wheeze was the most important change.Methods - Fifteen children with asthma (eight boys) of mean age 10.8 years (range 8-15) were studied. All had normal chest auscultation before the methacholine challenge test. Lung sounds were recorded over the trachea for one minute and stored on tape. They were analysed directly and also scored blindly from the tape recording by a second investigator. Wheeze, cough, increase in respiratory rate, and prolonged expiration were assessed.Results - The total cumulative methacholine dose causing a fall in FEV(1) of 20% or more (PD20) was detected in 12 children by a change in lung sounds - in four by wheeze and in eight by cough, increased respiratory rate, and/or prolonged expiration. In two subjects altered lung sounds were detectable one dose step before PD20 was reached. In three cases in whom no fall in FEV(1) occurred, no change in lung sounds could be detected at the highest methacholine dose.Conclusion - Changes in lung sounds correspond well with a 20% fall in FEV(1) after methacholine challenge. Wheeze is an insensitive indicator for assessing bronchial responsiveness. Cough, increase in respiratory rate, and prolonged expiration occurs more frequently.