Exercise induced bronchial (EIB) constriction is a common and highly specific feature of pediatric asthma and should be diagnosed with an exercise challenge test (ECT). The impact of EIB in asthmatic children's daily lives is immense, considering the effects on both physical and psychosocial development. Monitoring childhood asthma by ECT's can provide insight into daily life disease burden and the control of asthma. Current guidelines for bronchoprovocation tests restrict both the use of reliever and maintenance asthma medication before an exercise challenge to prevent false-negative testing, as both have significant acute bronchoprotective properties. However, restricting maintenance medication before an ECT may be less appropiate to evaluate EIB symptoms in daily life when a diagnosis of asthma is well established. Rigorous of maintenance medication before an ECT according to guidelines may lead to overestimation of the real, daily life asthma burden and lead to an inappropiate step-up in therapy. The protection against EIB offered by the combined acute and chronic bronchoprotective effects of maintenance medication can be properly assessed whilst maintaining them. This may aid in achieving the goal of unrestricted participation of children in daily play and sports activities with their peers without escalation of therapy. When considering a step down in medication, a strategic wash-out of maintenance medication before an ECT aids in providing objective support of potential discontinuation of maintenance medication.

Background Asthma is one of the most common chronic diseases in childhood, occurring in up to 10% of all children. Exercise-induced bronchoconstriction (EIB) is indicative of uncontrolled asthma and can be assessed using an exercise challenge test (ECT). However, this test requires children to undergo demanding repetitive forced breathing manoeuvres. We aimed to study the electrical activity of the diaphragm using surface electromyography (EMG) as an alternative measure to assess EIB. Methods Forty-two children suspected of EIB performed an ECT wearing a portable EMG amplifier. EIB was defined as a fall in FEV1 of more than 13%. Children performed spirometry before exercise, and at 1, 3 and 6 min after exercise until the nadir FEV1 was attained and after the use of a bronchodilator. EMG measurements were obtained between spirometry measurements. Results Twenty out of 42 children were diagnosed with EIB. EMG peak amplitudes measured at the diaphragm increased significantly more in children with EIB; 4.85 μV (1.82–7.84), compared to children without EIB; 0.20 μV (−0.10–0.54), (p<0.001) at the lowest FEV1 post-exercise. Furthermore, the increase in EMG peak amplitude could accurately distinguish between EIB and non-EIB using a cut-off of 1.15 μV (sensitivity 95%, specificity 91%). Conclusion EMG measurements of the diaphragm are strongly related to the FEV1 and can accurately identify EIB. EMG measurements are a less invasive, effort-independent measure to assess EIB and could be an alternative when spirometry is not feasible.

Rationale - Asthma is one of the most common chronic diseases in childhood, occurring in up to 10% of all children. Exercise induced bronchoconstriction (EIB) is indicative of uncontrolled asthma and can be assessed by means of an exercise challenge test (ECT). These tests however draw heavily on healthcare resources and require demanding repetitive forced breathing manoeuvres of children. In this study the electric activity of the respiratory muscles was measured as a tool to assess EIB. Methods - Children suspected of exercise induced respiratory symptoms performed an ECT wearing a portable EMG amplifier (Dipha-16, Demcon Macawi respiratory systems, Enschede, the Netherlands). EIB was defined as a fall in FEV1 of greater than 13%. Electrodes were placed bilaterally at the diaphragm and accessory breathing (intercostal-, sternocleidomastoid- and trapezoid) muscles. A single reference electrode was placed at the sternum. Children were asked to sit still for 30 seconds after each spirometry measurement to obtain EMG measurements. Data was pre-processed and analyzed in Matlab. Results - 20 Out of 43 children were diagnosed with EIB. Peak amplitude measured at the diaphragm increased significantly more in children with EIB than in children without EIB; 4.85uV (1.82 - 7.84), compared to 0.20uV (-0.10 - 0.54); (P < 0.001) at the point of maximal bronchoconstriction. Increases in EMG peak heights at the diaphragm can accurately distinguish between EIB and non-EIB (Sensitivity 95%, Specificity 91%, AUC 0.973). Increase in activity at the diaphragm is related to the decrease in pulmonary function (Pearson's R = 0:77; R2 = 0.58; P < 0.001). Accessory breathing muscles were often not measurable at baseline, therefore accurate assessment of the changes in activity in response to exercise could not be attained. Conclusion - These results imply that EMG measurements of the diaphragm can be used to accurately distinguish between EIB and non-EIB in children. Larger increases in peak amplitude suggest an increased work of breathing as is expected in children with EIB. Moreover, we found a relation between the decrease in pulmonary function and the increase of EMG peak activity. This technique provides opportunities to non-obtrusively measure bronchoconstriction when spirometry is not feasible or available and may be applied in the clinical setting, such as emergency medicine or in hospital- or home monitoring