Cardio-respiratory responses to exercise following treatment of acute severe asthma.

Asthmatic patients are encouraged to adopt a normal and active life-style. However, following treatment of acute severe asthma, patients may ask for advice about taking exercise. Serial measurements of the cardio-respiratory responses to continuous work load exercise, were made in asthmatic patients convalescing following hospital treatment of an acute exacerbation. Eighteen asymptomatic patients, (seven male) aged 18-48 years, were studied. The first test was performed within 1 week of admission, when the mean (SD) peak expiratory flow rate (PEFR) was 88 (20)% predicted normal and the arterial oxygen tension (PaO2) was 13.1 (1.4) kPa. No significant differences in the mean cardio-respiratory responses, from the last minute of exercise, were found during the 4-week study. There were no significant differences in the four tests, between the resting PEFR, lowest post-exercise PEFR or % change in PEFR. Also, there were no significant differences in the pre-exercise, end of exercise and recovery (10 min after exercise) PaO2, between the four tests. However, taking the four tests as a whole, significant relationships were found between the recovery PaO2 and the lowest post-exercise PEFR, expressed in absolute terms (r = 0.515, P less than 0.001), and as a percentage of predicted normal (r = 0.533, P less than 0.001); and also between the recovery PaO2 and the % change in PEFR after exercise (r = 0.299, P less than 0.05). It is suggested that a formal exercise test should be performed in convalescent asthmatics wishing to participate in active sports. Patients with exercise-induced asthma may then be identified and treated appropriately.