Evaluation of Wire Electrodes to Activate the Expiratory Muscles to Restore Cough

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DESCRIPTION (provided by applicant): This application addresses broad Challenge Area (06) Enabling Technologies and Specific Challenge Topic, 06-NS-104: Developing and validating assistive neuro-technologies. Respiratory complications account for significant morbidity and mortality in patients with spinal cord injury due to their inability to cough and clear secretions. These individuals lack an effective cough mechanism due to the fact that their injury often results in paralysis of virtually all of their expiratory muscles. Consequently these patients are dependent upon caregiver assistance for the application of manual suctioning, assisted coughing maneuvers or other methods of airway management. These methods are cumbersome, generally uncomfortable, require trained personnel and often restrict patient mobility. Since the spinal cord below the level of injury is intact in most patients, the motoneurons of the spinal cord and peripheral neuromuscular apparatus remain functional. Therefore, the expiratory muscles should be amenable to functional electrical stimulation techniques to restore an effective cough mechanism. In a single site, pilot study in tetraplegic subjects, we have recently shown that the expiratory muscles can be electrically activated by spinal cord stimulation, a method which involves the surgical placement of disc electrodes through laminotomy incisions. Electrodes are positioned in the dorsal epidural space at the lower thoracic and upper lumbar spinal levels. The results of this study indicate that this method is successful in achieving an effective means of expiratory muscle activation, as demonstrated by the generation of large airway pressures and peak airflow rates. Importantly, this technique facilitates secretion removal, reduces the need for caregiver support, reduces the incidence of respiratory tract infections and improves life quality. This technique therefore has the potential to reduce health care costs and improve survival in spinal cord injured subjects. While successful, many individuals with spinal cord injury are reluctant to pursue this technique due to the invasive procedure required for electrode placement. It is our hypothesis however that comparable activation of the expiratory muscles can be achieved with wire electrodes which can be inserted percutaneously through a needle, eliminating the need for the invasive laminotomy procedure and can be performed on an out-patient basis. This latter procedure would increase patient and physician acceptance of this technique, shorten recovery times and significantly reduce costs. The purpose of this undertaking therefore is to directly compare the efficacy of wire electrodes vs the previously employed disc electrodes. In 6 patients undergoing permanent implantation of disc electrodes to restore cough, we plan to directly compare the degree of expiratory muscle activation achieved with temporary placement of several different wire electrode systems with the disc electrodes. The degree of expiratory muscle activation will be compared by monitoring the changes in airway pressure and peak airflow rate generation achieved during electrical stimulation with different electrode systems in the Operating Room. The results of this trial will provide a) critically important data concerning the size and stimulus configuration of wire electrodes resulting in optimal expiratory muscle activation, b) the framework for additional human studies utilizing minimally invasive techniques to restore cough and c) necessary data for a possible amendment of our Investigational Device Exemption (IDE) to restore cough via spinal cord stimulation, with regard to use of wire electrodes. PUBLIC HEALTH RELEVANCE: Due to their inability to cough, respiratory complications such as pneumonia are a major cause of disability and death in subjects with spinal cord injury. The purpose of the proposed study is to evaluate a minimally invasive method of electrical activation of the expiratory muscles to restore cough utilizing spinal cord wire electrodes which can be inserted percutaneously. This technique would likely have wide patient and physician acceptance, significantly reduce the need for caregiver support, facilitate management of respiratory secretions, reduce the incidence of respiratory tract infections, reduce costs and improve life quality in this patient population.