Assessment of bronchodilator response in children with asthma. Dutch CNSLD Study Group

The bronchodilator response (BDR) in forced expiratory volume in one second (FEV1) is routinely assessed to estimate the reversibility of airways obstruction. However, there is no consensus on how the BDR should be expressed, and recommendations applying to children are lacking. Similarly, the relationship between BDR and nonspecific bronchial hyperresponsiveness to histamine (BHR) has not been elucidated. These questions were addressed in 116 children, 7-16 yrs of age, with stable after withdrawal of all pulmonary maintenance medication. Inclusion criteria were an initial FEV1 between 55-90% predicted, and/or FEV1/forced vital capacity )FVC) between 50-75%, as well as a fall in FEV1 of 20% or more when challenged with up to 150 mug histamine. The change in FEV1 (DELTAFEV1) 20 min after inhalation of 800 mug salbutamol was expressed in four ways: as an absolute difference (DELTAV1(l)), as a percentage of predicted FEV1 (DELTAFEV1%pred) or initial FEV1 (DELTAFEV1%init), and as a percentage of the deficit in FEV, (DELTAFEV1%(pred-init)).DELTAFEV1%init and DELTAFEV1%pred were not related to age and stature of the children; DELTAFEV1%(pred-init) was related to stature, whilst DELTAFEV1(l) was related to both age and stature. All indices correlated with initial FEV1. However, this is an artefact introduced by relating change to initial value, rather than to the mean of initial and final value. In fact, BDR, expressed as DELTAFEV1%pred, was only slightly greater in children with the lowest initial airway calibre (p=0.08), unlike DELTAFEV1%init. BDR was weakly related to BHR.We conclude that the BDR in children is best expressed as DELTAFEV1%pred, because this is not dependent on age, stature and initial FEV1. In addition, BDR should not be taken as a measure of bronchial responsiveness to bronchoconstricting stimuli.