The Diagnostic Value of Impulse Oscillometry and Plethysmography for the Assessment of Exercise-Induced Bronchoconstriction in Asthmatic Children

Exercise-induced bronchoconstriction (EIB) is a key clinical problem for asthmatic children. Exercise challenge tests, used to confirm EIB, are time consuming and require patient cooperation. The aim of this study was to investigate the diagnostic values of fractional exhaled nitric oxide (FeNO), impulse oscillometry (IOS), and plethysmography for prediction of EIB in children with well-controlled asthma. Fifty-nine children with allergic asthma aged 6–18 years were included in the study. FeNO was measured and all patients underwent spirometry, IOS, and plethysmography. An exercise challenge test was performed to assess EIB. EIB was confirmed with an exercise challenge test in 20 (33.9%) patients. Baseline FeNO levels were significantly higher in the group with EIB ( P = 0.003). Resistance at 5 Hz (R5) and frequency dependence of resistance (R5–R20) in IOS and total specific airway resistance (SRtot), residual volume (RV), and the ratio of RV to total lung capacity in plethysmography were significantly higher in the group with EIB. In the logistic regression analysis, the higher baseline FeNO, R5–R20, and SRtot values were found to be significantly related to EIB [Odds ratios (OR):1.35 and P = 0.046, OR:1.80, and P = 0.016, and OR:1.10, P = 0.035, respectively]. To differentiate asthmatic children with EIB from those without EIB, the optimal cutoff point for FeNO was 28 ppb [negative predictive value (NPV):86% and positive predictive value (PPV):52%]. An SRtot level lower than 207.6% (NPV:96% and PPV:54%) can be used to exclude EIB. R5–R20 values higher than 15.5% (NPV: 81% and PPV:71%) were associated with EIB in asthmatic children. Baseline SRtot in plethysmography provided the best sensitivity, whereas the baseline R5–R20 in IOS offered the best specificity for EIB. This study suggested that FeNO, IOS, and plethysmography are valuable tools for the assessment of EIB in children with controlled asthma and EIB is strongly correlated to small airway disease markers.