Laryngeal pacing in unilateral vocal cord paralysis. An experimental study.

In an attempt to remobilize a unilaterally paralyzed vocal cord, experiments were made in five adult dogs. Adduction of the paralyzed vocal cord for phonation in synchrony with the intact cord was achieved by electrical stimulation of the adductor muscles that was triggered by the signals from the cricothyroid muscle. The difference in the level of action potentials of the cricothyroid muscle between during phonation and during respiration was used for setting the threshold so as to differentiate phonation from respiration. Nearly synchronous movement of the two vocal cords thereby attained during phonation greatly improved the voice quality that was hoarse without the paced stimulation.