COMPARISON OF RESPONSIVENESS TO METHACHOLINE, HISTAMINE, AND EXERCISE IN SUBGROUPS OF ASTHMATIC-CHILDREN

  • 1 January 1984
    • journal article
    • research article
    • Vol. 129  (2) , 221-224
Abstract
Nonspecific bronchial reactivity, involving inhaled challenges with methacholine and histamine and treadmill exercise challenge, were compared in 2 groups of steroid-requiring asthmatic children (9 to 15 yr of age) distinguished on the basis of marked differences in their typical time course of clinical deterioration leading to in-hospital management. Group I patients (n = 8) had rapid clinical deterioration (occurring within 8 h from the onset of respiratory symptoms) while in group II patients (n = 7), clinical deterioration occurred relatively slowly (i.e., exceeding 24 h from the onset of respiratory symptoms). Pharmacologic bronchial sensitivity was evaluated as the log dose of the agonist producing a 20% fall in FEV1 [forced expiratory volume in 1 s] (PD20.cntdot.FEV1) and a 35% fall in specific conductance (PD35.cntdot.SGaw). Exercise-induced bronchospasm was evaluated in terms of the maximal decrease in FEV1 and SGaw after 6 min of steady-state treadmill exercise at 85% of the age-predicted maximal heart rate. Group 1 patients had near normal baseline FEV1 and SGaw while in group II patients, the baseline values of these parameters were significantly reduced (P < 0.02). Group I was more sensitive to methocholine than was group II, providing significantly lower mean values of PD20.cntdot.FEV1 (P < 0.003) and PD35.cntdot.SGaw (P < 0.001). The 2 groups were not significantly different with respect to their bronchial sensitivity to either histamine or exercise challenge. Thus, asthmatic children with marked differences in clinical presentation of bronchospasm may be further distinguished on the basis of methacholine sensitivity. Different pathophysiologic mechanisms of asthma may be involved in subgroups of asthmatic children.