Complete Restoration of Respiratory Muscle Function in Three Subjects With Spinal Cord Injury: Pilot Interventional Clinical Trial

Abstract

Objectives: The aim of this study was to assess the safety and efficacy of complete restoration of respiratory muscle function in subjects with spinal cord injury.

Methods: This was an interventional study investigating three subjects maintained on a diaphragm pacing system who were implanted with the spinal cord stimulation system to restore cough. Peak expiratory airflow and airway pressure generation were the primary physiologic outcome measures; an assessment of the degree of difficulty in raising secretions was the primary clinical outcome measure.

Results: Mean peak expiratory airflow and airway pressure generation during spontaneous efforts were 1.7 ± 0.2 L/s and 31 ± 7 cmH2O, respectively. When spinal cord stimulation was applied after pacing volume associated with the subject's maximum inspiratory effort and synchronized with the subject's maximum expiratory effort, peak expiratory airflow and airway pressure generation were 9.0 ± 1.9 L/s and 90 ± 6 cmH2O, respectively (P < 0.05). Moreover, each subject experienced much greater ease in raising secretions and marked improvement in the ease in raising secretions compared with other methods.

Conclusions: Complete restoration of respiratory muscle function can be safely and effectively achieved in the same individuals with spinal cord injury. Spinal cord stimulation results in peak expiratory airflow and airway pressure generation characteristic of a normal cough, whereas diaphragm pacing was successful in maintaining patients off mechanical ventilation.

Trial registration: ClinicalTrials.gov NCT01659541.

Conflict of interest statement

Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.

Figures

FIGURE 1.

Schematic representation of internal and external components of the diaphragm pacing system to restore breathing and spinal cord stimulation system to activate the expiratory muscles to restore cough.

FIGURE 2.

Representative tracings of expiratory airflow and airway pressure in one subject. Spontaneous maximum expiratory effort after a paced breath (far left panel), SCS after a paced breath (maneuver #1), SCS after a maximum inspiratory effort during a paced breath (maneuver #2), and SCS after a maximum inspiratory effort during a paced breath and subsequent maximum expiratory effort in conjunction with SCS (maneuver #3). See text for further explanation.

FIGURE 3.

Mean peak airflow rate (upper panel) and mean airway pressure (lower panel) during pacing volume and subjects maximal spontaneous inspiratory and expiratory effort (gray bars) and also during synchronized SCS (black bars).

FIGURE 4.

Subject responses when asked to numerically rate their difficulty in raising secretions according to a scale between none and severe (upper panel). Compared with preimplant values, there was marked improvement in their difficulty in raising sputum. When asked to numerically rate the degree of improvement with regard to their ease in raising sputum compared with other methods, there was marked improvement postimplant (lower panel).