This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Patients with cervical and thoracic spinal cord injuries often 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 the development of recurrent respiratory tract infections. Since the spinal cord below the level of injury is intact in most patients, the motor neurons of the spinal cord and peripheral neuromuscular system innervating the expiratory muscles are intact. These muscles, therefore, can be electrically activated by the electrical stimulation of the spinal roots to produce a functionally effective cough. It the hypothesis of the investigators that lower thoracic spinal cord stimulation (SCS) will result in the generation of large positive airway pressures and peak expiratory flow rates characteristic of a normal cough. This methodology, therefore, has the potential to produce an effective cough mechanism in spinal cord injured patients. Eighteen patients with spinal cord injury will be recruited into this study. A complete history and physical examination, chest x-ray and ECG will be performed. Patients initial testing will include measurement of spontaneous tidal volume, vital capacity and respiratory muscle strength as determined by maximum inspiratory and expiratory pressures. Spinal cord disc electrode and radiofrequency receiver will then be placed in the operating room. Stimulus parameters will be set very low initially and gradually increased. The effectiveness of spinal cord stimulation will be assessed by measurements of airway and gastric pressures, expired volume, expiratory flow rate, and abdominal EMG recordings. The full benefit of training usually requires a minimum of 6-8 weeks to optimize the function of other respiratory muscles.
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