Agreement between spirometry and tracheal auscultation in assessing bronchial responsiveness in asthmatic children

We have recently found that changes in lung sounds correspond well with a 2 0% fall in the forced expiratory volume in 1 s (FEV1) after methacholine ch allenge in asthmatic children. Up to now, little was known about the agreem ent between a 20% fall in FEV1 and a change in lung sounds after repeated b ronchial challenge. In this study we investigated the agreement between the total cumulative hi stamine dose causing a fall in FEV1 of 20% or more (PD20) and the detection of a change in lung sounds (PDlung sounds) after two bronchial challenges on different occasions in asthmatic children. Fifteen asthmatic children (nine boys), mean age 10.8 years (range 9-15), w ere studied. All performed two histamine challenge tests on 2 days, with a 24 h to 1 week interval. Lung sounds were recorded over the trachea for 1 m in and stored on tape. Lung sounds were analysed directly and also scored f rom the tape-recording by a blinded second investigator. Wheeze, cough, and an increase in respiratory rate were assessed. The relationship between PD 20 and PDlung sounds was calculated by Bland and Altman's measurement of ag reement. Eleven children had a positive challenge test (PD20 less than or equal to 1 6.0 mg ml(-1)) on both test days; four had a positive challenge on one test day. In 24 out of 26 positive challenges, wheeze, cough, prolonged expirat ion and/or increased respiratory rate were detected one dose-step before, o r at the dose-step of histamine that induced a fall in FEV1 of 20% or more. In two challenges, PD20 was not detected by a change in lung sounds. In fo ur out of four negative challenges (PD20 less than or equal to 16.0 mg ml(- 1)) no change in lung sounds could be detected. Good agreement between the logarithm of PD20 and the logarithm of PDlung sounds was found on both test days. The mean difference was 0.04 and the limits of agreement (d +/- 2 SD of the differences) were 0.04 +/- 0.41. A good agreement was found between the total cumulative histamine dose caus ing a fall in FEV1 of 20% or more and the detection of a change in lung sou nds after two bronchial challenges on different occasions in asthmatic chil dren.