Cough threshold and reactivity to mechanical stimulation of the trachea in the rabbit preliminary observations.

OBJECTIVES

The aim of the study was to characterise mechanically induced cough threshold and reactivity by exposing the trachea to stimuli of variable duration in rabbit.

BACKGROUND

Long lasting mechanical stimulation is widely used in experimental protocols studying cough reflex. The cough threshold and reactivity to chemical agents is known to change due to e.g. airway inflammation but similar evidence for mechanical stimulation has not been reported.

METHODS

The tracheal provocation was realized in two anesthetized tracheotomized rabbits with a rotating probe actuated by a small electrical motor with mechanical stimulus times (ST) lasting 50, 150, 300 and 600 ms. Cough reflex was evaluated from tidal volume and airflow signals.

RESULTS

The incidence of cough reflex (single or multiple) increased from 8% (ST 50 ms) to 84% (ST 600 ms). With the lengthening of stimulus, the rate of multiple responses increases.

CONCLUSION

The technique developed here may prove useful to standardize the protocols of mechanical cough in the experimental animal using an approach similar to chemical tussigenic agents. The cough threshold could be defined as minimal ST (STmin) capable to elicit 1 cough and cough reactivity obtained by interpolation as ST that provokes 50 % of cough responses (STso) (Tab. 1, Fig. 3, Ref. 27).