Determination of the Optimal Conditions for Laryngeal Pacing with the Itrel Ii Implantable Stimulator

OBJECTIVE: To determine the optimal stimulus paradigm, electrode orientation, and configuration of an implantable stimulator used to reanimate the posterior-cricoarytenoid (PCA) muscle in case of bilateral vocal fold paralysis (BVFP). STUDY DESIGN: Acute studies were conducted on 13 canines implanted with Itrel II systems with or without PCA innervation. PCA stimulus-response characteristics were obtained by measuring stimulated vocal fold displacement endoscopically. RESULTS: The denervated PCA was only 10% to 25% as responsive to stimulation as the innervated PCA. However, the response could be increased to 38% and 61% if the Itrel was modified to deliver 1 and 2 msec pulses, respectively. Stimuli delivered centrally to the muscle 5 mm from the median raphe improved performance. CONCLUSION AND SIGNIFICANCE: The optimal stimulus paradigm identified in this study (1 msec pulses delivered at 30 to 40 Hz and 2 to 8.5 mA) has been applied to implanted BVFP patients and improved outcome. Information regarding optimal electrode orientation could also be important to future clinical trials.