Exercise challenge in patients with asthma whose peak expiratory flow values are controlled within the green zone

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Recent guidelines for the management of asthma recommend that peak expiratory flow (PEF) should be measured to monitor the level of airflow limitation and to maintain PEF values within the green zone (80-100% of the patient's highest PEF value). Because no studies have evaluated the efficacy of PEF zone management on the basis of patients' physical activity, we studied the appearance of exercise-induced asthma (EIA) using treadmill exercise challenging in asthma patients whose PEF values had been maintained in the green zone for at least 3 months. Exercise-induced asthma was induced in nine of 44 (20.5%) asthma patients. The acetylcholine concentration required to cause a 20% fall in forced expiratory volume in 1 s (log PC₂₀) was significantly lower in patients with EIA (2.39 ± 0.21 µg/mL) compared with patients without EIA (3.22 ± 0.12 µg/mL; P < 0.03). These results suggest that PEF green zone management alone does not ensure the ability to perform vigorous physical activity, especially in patients whose airway reactivity remains enhanced. Therefore, airway reactivity should be considered for asthma management.