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

Abstract

We have recently found that changes in lung sounds correspond well with a 20% fall in the forced expiratory volume in 1 s (FEV 1) after methacholine challenge in asthmatic children. Up to now, little was known about the agreement between a 20% fall in FEV 1 and a change in lung sounds after repeated bronchial challenge. In this study we investigated the agreement between the total cumulative histamine dose causing a fall in FEV 1 of 20% or more (PD 20) and the detection of a change in lung sounds (PD lung sounds) after two bronchial challenges on different occasions in asthmatic children. Fifteen asthmatic children (nine boys), mean age 10·8 years (range 9–15), were 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 min and stored on tape. Lung sounds were analysed directly and also scored from the tape-recording by a blinded second investigator. Wheeze, cough, and an increase in respiratory rate were assessed. The relationship between PD 20 and PD lung sounds was calculated by Bland and Altman's measurement of agreement. Eleven children had a positive challenge test (PD 20 ≤ 16·0 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 expiration and/or increased respiratory rate were detected one dose-step before, or at the dose-step of histamine that induced a fall in FEV 1 of 20% or more. In two challenges, PD 20 was not detected by a change in lung sounds. In four out of four negative challenges (PD 20 >16·0 mg ml −1) no change in lung sounds could be detected. Good agreement between the logarithm of PD 20 and the logarithm of PD lung 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 causing a fall in FEV 1 of 20% or more and the detection of a change in lung sounds after two bronchial challenges on different occasions in asthmatic children.