Acute Relief of Exercise-Induced Bronchoconstriction by Inhaled Formoterol in Children With Persistent Asthma: Statistics
Spirometry was performed and results accepted as per American Thoracic Society (ATS) standards (Jaeger MasterScreen; E Jaeger GmbH; Wurzburg, Germany) with the children in a sitting position wearing a nose clip. FEV1 and maximal mid-expiratory flow (MMEF25-75) were recorded before exercise (baseline), after exercise (1 min, 3 min, and 5 min), and after administration of study drug (1 min, 3 min, 5 min, 10 min, 15 min, 20 min, 30 min, and 60 min) [Fig 1]. Baseline spirometry was performed in triplicate. Baseline FEV1 (the highest of three measurements) should be at least 70% of predicted normal value and was not allowed to vary > 15% between study days. Asthma symptoms were not recorded.
Exhaled nitric oxide (FeNO) was measured at baseline (Aero-crine NO System; Aerocrine; Stockholm, Sweden) according to ATS/European Respiratory Journal recommendations, and data on the predictive value of FeNO screening for EIB are reported separately. add comment
The exercise test was performed according to the ATS guide-lines, consisting of a standardized treadmill test, breathing absolutely dry, room temperature air from a facemask with a septum preventing nasal breathing. Workload was adjusted until submaximal pulse (180 ± 5 beats/min) as monitored by radio telemetry. The decline in lung function values after exercise was calculated as the change from baseline to the minimum value within 5 min after exercise in percentage of the baseline value. Study medication was administered 5 min after exercise but only if the child showed at least a 15% drop in FEV1 after exercise (Fig 1). Otherwise, FEV1 was monitored at 10 min and 15 min after exercise. If the drop then was at least 10%, the visit was rescheduled. If the drop in FEV1 also at the subsequent visit was < 15%, the child was withdrawn from the study (Fig 1).
The primary outcome parameter was FEV1 5 min after drug administration. FEV1 and MMEF25-75 from different time points (3 min, 5 min, 10 min, and 60 min after drug administration) were compared between the treatments using analysis of variance models with treatment, period, and patient as factors. Data were log-transformed prior to analysis. Each time point was analyzed separately.
Figure 1. Study design.