Bronchial lability in cystic fibrosis.

We investigated the airway's response to exercise in cystic fibrosis (CF). Due 
to the reported high incidence of allergy in CF we tried 
to demonstrate the well documented post-exercise bronchospasm of asthma in patients 
with CF. Subjects ran on a treadmill for 6 minutes at 
a speed of 3 miles per hour and a gradient of 
15 degrees. For the 12 controls studied, the mean % rise 
in peak expiratory flow rate (PEFR) during exercise was 4.7% and 
the mean % fall in PEFR during recovery was 0.7%. For 
the eight atopic asthmatics studied the mean % rise in PEFR 
was 12.2% and the mean % fall in PEFR was 33.7%. 
For the 29 patients with CF, the mean % rise in 
PEFR was 20.3% and the mean % fall in PEFR was 
3.1%. Patients with CF showed no statistically significant post-exercise constriction compared 
with controls, while asthmatic patients showed a post-exercise % fall in 
PEFR significantly greater than seen in controls (p < 0.001) or 
in CF patients (p < 0.001). No patient with CF showed 
post-exercise bronchospasm, nor was there any difference between patients with CF 
who had positive skin tests to common allergens and those who 
did not in their pattern of bronchial liability. It is suggested 
that the general desensitization therapy should not be instituted in patients 
with CF merely on the basis of positive skin tests, without 
more stringent criteria such as characteristic seasonal variation in respiratory symptomatology, 
family history of atopy and positive bronchial inhalation provocation tests. 