[Effect of output from jet nebulizers on PC20 values in asthmatic children]

This study aimed to assess the effects of two different nebulizer outputs on airway responsiveness to methacholine in asthmatic children. Twenty-seven atopic asthmatic children aged 6 to 14 years inhaled methacholine according to the Cockroft method until FEV1% had decreased 20% with respect to saline inhalation (PC20). The bronchial challenge tests were performed using two different types of jet nebulizer: Ava Neb 1780 and Hudson UP Draft II 1730, the outputs of which were 205 +/- 13 mg/min and 356 +/- 31 mg/min, respectively (p < 0.05). For 9 out of 27 patients (33%) the PC20 values were significantly different (one or more double concentrations) for the two nebulizers. However, 7 of those 9 children showed significantly lower bronchial responsiveness when the challenge tests were conducted with the low output jet nebulizer. This study suggests that using jet nebulizers with different outputs can markedly influence the results of methacholine challenge tests in asthmatic children. Such an influence could introduce significant bias in the assessment of bronchial responsiveness in comparative measurements in a single individual or in populations.