This is a continuation proposal in respiratory care of the upper-level SCI individual investigating effective stimulatory devices and methods. Stimulation of extradiaphragmatic muscles, abdominal and upper-thorax, in conjunction with diaphragmatic activation is proposed. Based upon our recent findings of robust respiratory responses with four bilateral sets of surface and implanted PermalocTM electrodes in both extradiaphragmatic muscles, further research is warranted. Five areas of investigations are proposed.
Aim 1, Abdominal Stimulation for Cough: Demonstrate maximal abdominal expiratory flow and volume responses to stimulation using (A) surface and (B) implanted PermalocTM Mapping electrodes by conducting parameter-response tests in the areas of current, electrode numbers and locations, stimulating frequency, electrode configurations and electrode stimulation staggering.
Aim 2, Upper-Thorax Stimulation for Cough: Elucidate large upper-thoracic inspiratory flow and volume responses without more than slight forelimb movement using (A) surface and (B) implanted Permaloc(r) Mapping electrodes by conducting parameter-response testing in the areas of current, electrode numbers and locations, stimulation frequencies, electrode configurations and electrode stimulation staggering.
Aim 3, Combined Extra Diaphragmatic Muscles for Cough: Compare stimulation of extradiaphragmatic muscles alone (Aims 1 and 2) to combined methods using surface and implanted electrodes for maximal airway flow and volume.
Aim 4, Combined Extradiaphragmatic Muscles for Ventilation: Ascertain effective methods of extended pacing of extradiaphragmatic muscles alone and in combination using surface and implanted electrodes based on low O2 utilization and CO2 production during constant minute-ventilation protocols by conducting parameter-response tests.
Aim 5, Combined Diaphragm and Extradiaphragmatic muscles for (A) Cough (B) Ventilation and (C) 12- Channel Stimulation: A. Cough, using effective combined methods from Aim 3 for surface and implanted electrodes, add maximal diaphragm stimulation to induce high airway flow and volume. B. Ventilation, using effective methods for surface and implanted electrodes from Aim 4, add diaphragm stimulation to demonstrate low O2 utilization and CO2 production using constant minute-ventilation protocol by conducting diaphragm current-response tests with adjusted extradiaphragmatic muscles stimulation to obtain constant minute ventilation. Methods: Ten canines under acute anesthesia will be studied during this one-year investigation. During periods of respiratory apnea following hyperventilation, respiratory pacing studies will be conducted. Different PermalocR and surface electrodes will be tested. To model cough, stimulation for maximal airway expiratory responses will be carried out. For minute ventilation, the primary outcome measure will be low O2 utilization and CO2 production. Individual and combined respiratory muscle stimulation tests will be conducted. Stimulation testing will include duplicate testing. Implantable PermalocTM Multi-Lead-Cables placed through the skin with implanted Permaloc connectors and electrodes will be documented by photography during autopsy. ANOVAs with Student-Neuman-Keuls post-hoc analysis will be used to elucidate statistical significance; all data will be presented as mean + SEM.
Respiratory problems continue to be a primary concern for individuals with upper-level cervical spinal cord injury (SCI) that usually requires ventilator support; mortality is most often attributd to pneumonia. As an alternative to mechanical ventilation, stimulation of the phrenic nerve with electrodes implanted in the diaphragm is gaining acceptance. There is a need, however, to add abdominal and upper-thorax intercostal muscle stimulation for improved respiration and cough. In this study, we will test in new devices including implantable PermalocTM mapping and Multi-lead electrodes, surface electrodes and alternative respiratory pacing methods. Oxygen CO2 partial pressures during ventilatory pacing will be measured to optimize stimulation. Respiratory response will also be enhanced by using a 12- channel PermalocTM Respiratory Pacer-Trainer. Results of these tests are expected to contribute to the plan for technology transfer for improved respiratory management devices for SCI veteran patients.
