Acute airway changes induced by coughing.

The effects of voluntary coughs on specific conductance measurements were studied in normal, atopic and asthmatic subjects before and after bronchoconstriction with histamine. The responses were variable, the most frequent change being temporary bronchodilation in the 30 seconds after a voluntary cough in the presence of histamine-induced bronchoconstriction. The effects of the two components of coughing, namely a full inhalation and a cough without a preceding deep inhalation, were studied in a similar manner. After challenge with histamine had reduced specific conductance by approximately 50%, full inhalations produced a temporary increase in conductance. Modified coughs without deep inhalation after histamine most often resulted in a temporary small decrease in conductance. One atopic subject showed marked, prolonged airway narrowing after a single full inhalation before histamine. We conclude that the major effects on airway smooth muscle produced by coughs result from the deep inhalation. In challenge studies coughs may affect subsequent airways resistance measurements. Such brief changes are not clinically important but may affect the results of inhalation challenge studies. Occasionally individuals show more prolonged bronchoconstriction after such manoeuvres.