Abstract

As minute volume increases with age, a study was carried out to determine whether the measurement of bronchial responsiveness to pharmacological agents with the tidal breathing technique in children might be influenced by age. Bronchial responsiveness to histamine administered by tidal breathing was therefore compared with that produced with a dosimeter in 25 children with asthma aged 5-18 years. Bronchial responsiveness was defined as the concentration of histamine that caused a 40% rise in pulmonary resistance (PC40) measured by random noise forced oscillation at 6 Hz. Values of PC40 measured by the tidal breathing method were lower than those obtained with the dosimeter method, presumably owing to differences in the dose administered and variations in the pattern of breathing. The difference between the two methods was not related to age, however. It is concluded that the tidal breathing and the dosimeter methods are both suitable for the measurement of bronchial responsiveness in children of various ages and that both can be used in longitudinal studies.