Relation between bronchial and cardiac vagal tone in healthy humans.

A generally increased vagal nervous activity was suggested to exist in bronchial asthma; however, this contention has never been fully tested. Before studying vagal activity in asthma, we raised the question if there existed any relation between vagal outflows to different target organs in the physiologic state. The specific aim of this study was to determine the relation between the resting level of bronchial and cardiac vagal activity in healthy volunteers. Bronchial and cardiac vagal tone were measured in 12 subjects as the change of airway resistance (Raw) and heart period (HP) in response to complete cholinergic blockade. It was found that after intravenous atropine administration, Raw was reduced from 1.30 +/- 0.41 cm H2O/L/s to 0.51 +/- 0.22 cm H2O/L/s and HP was reduced from 789 +/- 84 ms to 506 +/- 41 ms. All the values are given as mean +/- SD. Both the bronchial and cardiac responses exhibited considerable interindividual variability, but there was no significant correlation between them (R = 0.22, p = 0.50). It was concluded that under resting conditions, vagal control of bronchial tone and HP were not related in healthy human subjects.