Comparison of impulse oscillometry and spirometry for detection of airway hyperresponsiveness to methacholine, mannitol, and eucapnic voluntary hyperventilation in children

Background Forced expiratory maneuvers are usually difficult in young children. Impulse oscillometry (IOS) requires no active cooperation, is noninvasive, rapid, and easy to perform. This study aimed to compare IOS indexes and forced expiratory volume in 1 second (FEV1) in children for the assessment of bronchial hyperreactivity to methacholine, mannitol, and eucapnic voluntary hyperventilation (EVH). Materials Children aged 3-14 years (mean 10.0 +/- 3.1) with symptoms suggestive of asthma were recruited. IOS measurements were taken before spirometry. Methacholine, mannitol, and EVH tests were performed without a specific order. Results We included 190 children, whose mean age was 10.0 +/- 3.1 years. Changes in FEV1 correlated significantly with variation in IOS indexes (P < .05). The indexes with the greatest discriminative capacity were Z5, R5, and X5. Optimal cut-offs were: for methacholine tests, >= 22% in R5, >= 82% for reactance area (AX), and <= 41% for X5; for the mannitol test, >= 18% in R5, >= 40% in AX, and <= 21% for X5. In the EVH test, >= 23% for R5, >= 40% for AX, and a fall of 29% for X5. When using the optimal cut-off points obtained from IOS, the mean number of steps and doses required for methacholine and mannitol tests to induce significant bronchoconstriction were significantly lower compared with spirometry (P < .05). Conclusions The effectiveness of R5, X5, and AX indexes were comparable to FEV1 in assessing bronchial obstruction during bronchial challenge testing. Therefore, IOS may be useful in assessing bronchial obstruction in children who cannot reliably perform spirometric maneuvers during bronchial challenge testing.