The effect of tracheostomy on the laryngeal closure reflex.

The clinical observation of aspiration following prolonged tracheostomy prompted a neurophysiologic investigation of the glottic closure reflex in dogs longitudinally evaluated after permanent tracheostomy. The data support significant alterations in the central organization of the protective closure reflex heretofore considered phylogenetically primitive and therefore physiologically stable over wide ranges of functional demand. The data indicate that chronic upper airway bypass results in: 1. increased threshold of the evoked adductor response; 2. random shifts in its latency; 3. rapid attenuation of the primary evoked response to repetitive SLN stimulation; and 4. reduced after-discharge activity, all of which contribute to a weakened, ill-coordinated closure respons.