Laryngeal response patterns to mechanical insufflation-exsufflation in healthy subjects

Mechanical insufflation-exsufflation (MI-E) is used to assist cough in patients with neuromuscular diseases. Clinically, application may be challenging in some patient groups, possibly related to laryngeal dysfunction. Before launching a study in patients, the authors investigated laryngeal responses to MI-E in healthy individuals.

Twenty healthy volunteers, aged 21-29 yrs, were studied with video-recorded flexible transnasal fiber-optic laryngoscopy while performing MI-E using the Cough Assist (Respironics, United States) according to a standardized protocol applying pressures of ±20 to ±50 cm H2O.

An initial abduction of the vocal folds was observed in all subjects, both during the insufflation and exsufflation phases. Nineteen of the 20 subjects adequately coordinated glottic closure when instructed to cough. When instructed simply to exhale during exsufflation, the glottis stayed open in a majority. Subsequent to an initial abduction during exsufflation and cough, various obstructive laryngeal movements were observed in some subjects, such as narrowing of the vocal folds, retroflexion of the epiglottis, hypopharyngeal constriction, and backward movement of the base of the tongue.

The larynx can be studied with transnasal laryngoscopy during MI-E in healthy individuals. Laryngeal responses to MI-E vary, and laryngoscopy may offer valuable clinical information when applying MI-E in patients with bulbar muscle weakness.