Correlation between tests of small airway function

Abstract

Cochrane, G. M., Benatar, S. R., Davis, J., Collins, J. V., and Clark, T. J. H. (1974.)Thorax,29, 172-178. Correlation between tests of small airway function. To compare and correlate tests of small airway function we have measured residual volume, frequency dependence of compliance, `closing volume', maximal expiratory flow rate at 50% and 25% of vital capacity, maximal expiratory flow rate at 50% of total lung capacity, and forced expired time in 10 health non-smoking male subjects and 10 non-smoking asthmatics who on the day of the study had no symptoms of airway obstruction. There was no evidence to suggest that any one particular test was more sensitive than others in detecting the presence of small airways obstruction. The closest correlation was between maximal expiratory flow rate at both 25% of vital capacity and 50% of total lung capacity and the forced expired time. It is argued that a prolonged forced expired time in the presence of normal dynamic lung volumes may be the most easily applicable screening test for early small airways obstruction.