Eight anesthetized tracheotomized rabbits were stimulated in the trachea by 150 ms probing before and after methacholine inhalation (248 tests). CR and ER were evaluated from tidal volume and expiratory flow.
The overall incidence of responses was larger in inspiration than expiration (p < 0.0001). A majority of responses were single CR or ER, also strongly related to breathing: 93 % CR occurred with the stimulus in inspiration and 78 % ER with the stimulus in expiration (p = 0.001). Bronchoconstriction did not change the incidence of single efforts, increased that of mixed responses and decreased the amplitude of preparatory and expulsive phases of CR.
The study demonstrates the strong dependence of CR and ER on the phase of breathing and adds to the current evidence that regulating mechanisms clearly differ for each reflex.