Ventilatory capacity, working capacity and exercise-induced bronchoconstriction in a population sample of subjects with bronchial asthma or chronic bronchitis.

We have studied a representative population sample comprising 185 persons, aged 35-54 years, having certain respiratory symptoms and considered to have chronic bronchitis and/or bronchial asthma. There were 86 with bronchial asthma (without chronic bronchitis), 69 with chronic bronchitis (without asthma) and 30 with both chronic bronchitis and bronchial asthma. Fifty-one of the 116 asthmatics had reaginic bronchial allergy. In the groups with chronic bronchitis or bronchial asthma, the mean ventilatory capacities were slightly below the normal, being 89 and 91%, respectively, of the predicted values for FEV1 and 85 and 87% of those for MVV40. In the group of persons with both diseases, the mean FEV1 was 77% and the mean MVV40 84% of that predicted. Of the 21 persons with a mean FEV1 below 70% of that predicted 10 had both asthma and bronchitis. Exercise-induced bronchoconstriction, defined as a 15% fall of PEF after exercise, occurred in 22 of the 116 asthmatics and in one of the 69 persons with chronic bronchitis without bronchial asthma. In the asthmatics there was a significant correlation between resting PEF or the difference in PEF before and after orciprenaline inhalation on the one hand, and exercise-induced bronchoconstriction on the other hand. This was taken as an indication of increased bronchial hyperreactivity.