Immediate and late asthmatic responses induced by exercise in patients with reversible airflow limitation.

The existence and prevalence of late asthmatic responses to exercise in patients is uncertain. We investigated whether the late falls of peak expiratory flow rate (PEFR) after exercise challenge were still significant after comparison with the corresponding clocktime PEFR on a control day. We examined 86 patients with reversible airflow limitation, 79 with asthma and 7 with chronic obstructive pulmonary disease (COPD), all under regular treatment with bronchodilators and/or anti-inflammatory agents. Patients were randomized for a control day and an exercise day and PEFR was recorded hourly. On the exercise day, each patient underwent an 8 minute bicycle ride at 90% of predicted heart-rate. An early and a late asthmatic response to exercise were considered to occur when PEFR decreased by 10% or more on the exercise day compared to the corresponding clocktime PEFR on the control day. Thirty-three patients (38%) had a 10% or greater fall of PEFR at 4 to 13 hours after exercise when PEFR was compared with the corresponding clocktime on a control day. Seven (8%) had an isolated late asthmatic response, and 26 (30%) had a dual asthmatic response. We conclude that true late asthmatic responses develop after exercise in a significant number of patients with well controlled reversible airflow limitation.