Evaluation of intercostal pacing to provide artificial ventilation in quadriplegics

The purpose of this study was to assess the utility of intercostal muscle pacing by spinal cord stimulation (SCS) to provide artificial ventilation in ventilator-dependent quadriplegic patients. Five ventilator-dependent quadriplegics with phrenic nerve injury (and therefore not candidates for phrenic nerve pacing) were studied. During an initial surgical procedure, a quadripolar epidural disc electrode was positioned on the ventral portion of the upper thoracic spinal cord via a hemilaminectomy and subsequently connected to a radiofrequency receiver implanted subcutaneously over the anterior rib cage. In four of the five patients, initial SCS stimulation resulted in inspired volumes between 150 and 240 ml. Stimulation resulted in no effect in one patient, due to probable cystic degeneration of the thoracic spinal cord. Reconditioning of the intercostal muscles caused substantial increases in inspired volume in three of four patients to 670 to 850 ml. In one patient, reconditioning resulted in a much smaller increase (to 470 ml). The maximum duration that ventilation could be sustained by low-frequency (13 Hz) intercostal pacing ranged between 20 min and 2 3/4 h. Our findings indicate that intercostal pacing via SCS does not result in sufficient inspired volume production to support ventilation for prolonged periods. However, this modality may be a useful adjunct to enhance tidal volume in patients with suboptimal inspired volume by phrenic nerve pacing.