Respiratory Stimulation for Cough Using a 12-Channel Neuroprosthetic Platform with Intramuscular Mapping and Permaloc® Electrodes: Acute Studies in Adult Canines

Abstract

Objective: Optimal methods of combined abdominal, upperthoracic and diaphragm muscles stimulation for cough were studied using a 12-Channel Neuroprosthetic Platform and intramuscular Mapping and Permaloc® electrodes. Methods: Large respiratory volumes were induced in six, adult, respiratory-apneic canines. Optimal abdominal stimulation used three or four bilateral sets of Mapping electrodes just dorsal to the abdominal lateral line, upper-thoracic optimization included two or three sets of these electrodes implanted ventral to the axilla, and diaphragm stimulation used two bilateral sets of Permaloc® implanted lateral to the central tendon. Combined muscle stimulation tests followed testing in individual muscles and included brief periods of tracheal tube clamping as a model of glottal closure to increase flow. For upper-thorax stimulation a safety factor was determined, to avoid the induction of heart arrhythmia, as the ratio of the highest total current with 12 sets of electrodes in the upper-thorax that did not induce arrhythmia, or the maximal current of 1,200 mA, to the optimized total current for a maximal inspiration.

Results: Maximal abdominal expiration was 257 + 31 ml, upperthorax inspiration was 409 + 91 (n = 6) ml, and diaphragm stimulation was 377 ± 39 ml (n = 6). Combined muscles stimulation was additive; upper-thorax followed immediately by abdominal stimulation increased the volume to 673 ± 118 while further adding the diaphragm resulted in 914 ± 77 ml. Peak flow was significantly increased for combined extradiaphragmatic stimulation from 1,582 ± 205 ml/s by the glottal closure maneuver to1,217 ± 189 ml/s (n =6). Safety from heart arrhythmia for upper-thorax stimulation was 5 for one animal where arrhythmia occurred and great than 16.4 ± 0.9 for four other animals with no arrhythmia. Conclusions: In a respiratory apneic canine model, combined respiratory muscles stimulation with the 12-Channel Neuroprosthetic Platform produced respiratory volumes adequate for cough. The safety and success of this platform in the canine model warrants further study with the long-term goal of providing assistive technology for respiration and cough for individuals with SCI. Key Words: spinal cord injury, respiration, electrical stimulation, functional electrical stimulation, respiratory distress Abbreviations SCI spinal cord injury rpm respirations per minute bpm beats per minute