Glottic closure reflex: control mechanisms.

Reflex glottic closure is a dominant and stable reflex produced by stimulation of the superior laryngeal nerve. Its precise execution is basic to successful sphincteric protection of the lower airway. In exaggerated form, it produces life-threatening laryngospasm. Clearly, reflex glottic closure and laryngospasm are facilitated by: a) expiratory phase; b) decreased arterial partial pressure of carbon dioxide (pCO2); c) increased arterial partial presure of oxygen (pO2); and d) negative intrathoracic pressure. On the other hand, both reflex glottic closure and laryngospasm are inhibited by; a) inspiratory phase; b) increased arterial pCO2; c) decreased arterial pO2; and d) positive intrathoracic pressure. A clear understanding of laryngeal adductor control is an essential first step in the therapeutic modification of abnormal laryngeal closure and laryngospasm.