Functional magnetic stimulation for restoring cough in patients with tetraplegia.

OBJECTIVE To evaluate the usefulness of functional magnetic stimulation (FMS) as a noninvasive method for assisting cough in patients with tetraplegia. DESIGN A prospective before-after trial. SETTING The functional magnetic stimulation laboratory of a spinal cord injury (SCI) service. PARTICIPANTS Thirteen male SCI patients, with injury levels between C4 and C7. INTERVENTION A commercially available magnetic stimulator with a round magnetic coil (MC) was used. Expiratory muscle activation was achieved by placing the MC along the lower thoracic spine. MAIN OUTCOME MEASURE The planned major outcome measures were the maximal expired pressure (MEP), expiratory reserve volume (ERV), and forced expiratory flow rate (FEF) by FMS compared with voluntary maximal efforts. Another outcome was the optimal MC placement and stimulation intensity that would result in highest expired pressure. RESULTS The mean (+/-SEM) MEP, ERV, and FEF generated by FMS were 66.40 +/- 6.69 cmH2O, .77 +/- .14 L, and 5.28 +/- .42 L/sec, respectively. They were 118%, 169%, and 110% of voluntary maximum efforts. MC placement at the T10 to T11 spinous process and stimulation intensity at 80% produced the highest MEP and FEF. CONCLUSION FMS of the expiratory muscles produced significant expired pressures, volumes, and flow rates when compared with voluntary maximum efforts; therefore, FMS can be used as an effective method to restore cough in tetraplegic patients.