Pulmonary Function Screening Tests In Bronchial Asthma

¹ The Veterans Administration Hospital and the University of Wisconsin Medical School, Madison, Wisconsin.

(1) It is recommended that asthmatic patients be given the following routine pulmonary function screening tests: Vital capacity, timed vital capacity, maximum breathing capacity by the spirographic method and the single breath O₂ test with determination also of the terminal rise.

(2) If possible it is urged that asthmatic patients be tested with a bronchial dilator drug on admission to the hospital in order to demonstrate the degree of bronchial spasm. After the patients have been under treatment for several days the changes become less marked.

(3) Bronchial dilator drugs usually increase the vital capacity but the improvement may be greater in the maximum breathing capacity. Bronchial dilator drugs given to asthmatic patients do not have a significant effect on air trapping as demonstrated in the maximum breathing capacity spirogram.

(4) Bronchial dilator drugs appear to have little effect on the timed vital capacity if recorded in percentage values. Nevertheless, examination of the expiratory curve will show an increase in the volume per second and improvement in maximum expiratory flow.

(5) Bronchial dilator drugs may cause the single breath O₂ test to show worsening of the intrapulmonary mixing of gases. It is suggested that this change may be due to the opening of more poorly ventilated portions of the lung following bronchial dilitation.

(6) It is recommended that these screening tests be utilized to recognize the early development of emphysema so that preventive measures may be taken as soon as possible.