Bronchomotor tone and the slope of phase III of the N2-test.

To determine the influence of bronchomotor tone on the slope of phase III of the N2-test, we studied subjects with reversible airflow limitation, who inhaled a standard dose of salbutamol. The design of the study allowed separation and comparison of the effects on the slope of phase III of changes in bronchomotor tone and in preinspiratory volume. The study shows that in subjects with a substantial reversibility of airflow limitation changes in the slope of phase III induced by salbutamol are related more to a change in preinspiratory volume than to a change in bronchomotor tone per se.