Patients with cervical and thoracic spinal cord injuries have paralysis of a major portion of their expiratory muscles and therefore, lack a normal cough mechanism. Consequently, most of these patients suffer from a markedly reduced ability to clear airway secretions, a factor which contributes to their development of recurrent respiratory tract infections and atelectasis and attendant high morbidity and mortality. Since the spinal cord below the level of injury is intact in most patients, the motoneurons of the spinal cord and peripheral neuromuscular system innervating the expiratory muscles are intact. These muscles, therefore, can theoretically be electrically activated to produce a functionally effective cough mechanism. Recent animal studies (performed in our laboratory) indicate that a major portion of the expiratory muscles can be activated by lower thoracic spinal cord stimulation (SCS). By this method, SCS results in the generation of large positive airway pressures and peak expiratory flow rates characteristic of a normal cough. It is our hypothesis that lower thoracic SCS, when applied in patients with spinal cord injury, will also result in generalized expiratory muscle contraction and produce an effective cough mechanism. We plan to apply this technique to patients with spinal cord injury who have paralysis of a major portion of their expiratory muscles. More specifically, we will evaluate patients with a) high cervical spinal cord injury (C1- C4) and consequently ventilator dependent, b) patients with low cervical spinal cord injury (C4-C8), most of whom are able to breathe spontaneously due to normal diaphragm function and, c) patients with thoracic spinal cord injury. The NDI Medical LLC (Cleveland, Ohio) expiratory muscle stimulator and NeuroControl Corp. (Cleveland, OH) electrodes will be employed to activate the expiratory muscles via SCS. Functional electrical stimulation of the expiratory muscles should be capable of producing an effective cough mechanism on demand via independent patient control and obviate the need for frequent patient suctioning which often requires the constant presence of trained personnel. This method will improve patient quality of life due to a greater sense of well being and less stressful method of secretion removal. Moreover, this technique should provide spinal cord injured patients the capacity to clear their secretions more readily and thereby reduce the incidence of respiratory complications and associated morbidity and mortality. ? ?
