LUNG-FUNCTION AND BRONCHIAL CHALLENGES IN INFANTS - REPEATABILITY OF HISTAMINE AND COMPARISON WITH METHACHOLINE CHALLENGES

Limited information exists regarding the repeatability of lung functio n and bronchial challenge tests using the rapid thoracic compression t echnique (RTC) in infants. Aims: To determine the repeatability of lun g function and histamine challenge test results using the RTC techniqu e and to compare the results obtained for bronchial challenges using h istamine (H) and methacholine (M). Methods: Twelve infants [7 healthy, 5 with cystic fibrosis (CF) had pairs of H challenges 1 week apart. E leven infants (7 healthy, 4 CF) had one H and one M challenge a week a part. The provocative concentration of H or M to cause a 40% fall in m aximum flow at functional residual capacity (PC40) was determined usin g the RTC technique. Twenty-three comparisons were possible between ma ximal expiratory flow at functional residual capacity (V(maxFRC)) meas urements made 1 week apart. Results: The mean difference between pairs of V(maxFRC) measurements was 6.4% of baseline, and the coefficient o f repeatability was 31.1% of baseline. The mean difference between PC4 0(H) measurements was 0.163 doubling concentrations, with a coefficien t of repeatability of 1.66 doubling concentrations. The mean differenc e between PC40(H) and PC40(M) was 0.75 doubling concentrations, with 9 5% of PC40(H) between -0.18 to 1.69 doubling concentrations of the PC4 0(M). Conclusions: Although the repeatability of V(maxFRC) using the R TC technique is less than for voluntary forced expiratory flow paramet ers in older children, similar results were obtained for infants as ob served in older subjects for repeatability of H challenges and agreeme nt between measures of bronchial responsiveness using H or M. (C) 1993 Wiley-Liss, Inc.