Respiratory complications account for significant morbidity and mortality in persons with spinal cord injury (SCI) due to their inability to cough an clear secretions. Consequently, they 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 and require trained personnel. These individuals lack an effective cough mechanism due to paralysis of their expiratory muscles. Since the spinal cord below the level of injury is intact in most subjects, th motoneurons of the spinal cord and peripheral neuromuscular apparatus remain functional. Therefore, the expiratory muscles are amenable to functional electrical stimulation techniques. In a single site, pilot study of 16 tetraplegics, we have recently shown that the expiratory muscles can be electrically activated by spinal cord stimulation (SCS) to restore an effective cough, a method which involves the surgical placement of disc electrodes through laminotomy incisions. We demonstrated that this method is successful in achieving an effective means of expiratory muscle activation, as demonstrated by the generation of large positive airway pressures and expiratory 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. While successful, electrode placement requires an invasive and costly procedure. Consequently, many individuals were unwilling to pursue this technique. Based upon the results of animal and human studies, it is our hypothesis that comparable activation of the expiratory muscles can be achieved with wire leads 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 significantly shorten surgical time, lessen the degree of surgery, shorten recovery time, reduce costs, and thereby, increase patient and physician acceptance of this technique. The purpose of this undertaking, therefore, is two-fold. First, the safety of chronic SCS with wire electrodes utilizing the proposed stimulus paradigm will be assessed in an animal model of SCI. Assuming a satisfactory safety analysis, the efficacy of SCS with wire leads will then be assessed in 16 subjects with SCI, in terms of the capacity of this method to activate the expiratory muscles, restore an effective cough mechanism and achieve significant clinical benefits related to secretion management. Given the significant heterogeneity of this orphan population, subjects will serve as their own controls to evaluate the success of this technique. If successful, the wire lead system will provide a minimally invasive method of restoring cough, and has the potential to significantly improve life quality. Ultimately, restoration of an effective cough with SCS has the potential to significantly improve the morbidity and mortality associated with respiratory complications in persons with SCI. This study will also provide the data necessary for a multi-center trial of this technique leading to eventual FDA approval.
Due to their inability to cough, respiratory complications such as pneumonia occur frequently and are a major cause of death and disability in persons 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 an effective cough utilizing spinal cord wire leads. This technique would likely have wide subject 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 population.