The expiration reflex from the trachea and bronchi

¹ Dept of Pathophysiology, Faculty of Medicine, Comenius University, 08753 Martin, Slovakia
² University of London , 116 Pepys Road, London SW20 8NY, UK

^* To whom correspondence should be addressed. E-mail: JohnWiddicombeJ{at}aol.com.

	Abstract

The expiration reflex (ER) is a forced expiratory effort against a closed glottis that subsequently opens to eject laryngeal debris and prevent aspiration of material. It is distinct from the cough reflex (CR). Its source is usually assumed to be restricted to the larynx and vocal folds, and its possible origin from the tracheobronchial (TB) tree has been suggested but never studied.

We have reanalysed some of our records with mechanical or chemical stimulation of the TB tree to see if an ER can consistently be elicited, and to see whether it has properties similar to that from the larynx and vocal folds. We have made a random review of some of the extensive literature on TB "cough" to see if this confirms our conclusions.The TBER was consistently seen in cats and rabbits, either alone or followed by cough. These results are consistent with many studies in other species, including humans. It was enhanced, relative to cough, by inflation of the lungs and by general anaesthesia.

The TBER occurs frequently with mechanical stimulation of the TB tree. It differs fundamentally from many of the properties of "true" cough. Its similar features to the laryngeal ER suggest that both should be labeled "expiration reflexes" and not "cough". Its existence should be taken into account in experimental, and possibly clinical, studies on TB "cough".