Comparison of disc and wire electrodes to restore cough via lower thoracic spinal cord stimulation

Abstract

Objective: To compare the safety and effectiveness of wire (WE) vs. disc (DE) electrodes to restore cough in subjects with spinal cord injury (SCI).

Design: Clinical trials assessing the effectiveness and clinical outcomes associated with two electrode systems to activate the expiratory muscles.

Setting: Inpatient hospital setting for DE or WE electrode insertion; outpatient evaluation of cough efficacy and instructions for home use.

Participants: Twenty-nine subjects with SCI; 17 participants with DE and 12 with WE implants.

Intervention: Surgical implantation of WE or DE to restore cough. Daily application of spinal cord stimulation (SCS) at home.

Main outcome measure(s): Airway pressure (P) and peak airflow (F) generation achieved with SCS; clinical parameters including ease in raising secretions, incidence of acute respiratory tract infections (RTI) and side effects.

Results: P and F achieved with DE and WE were not significantly different. For example, at total lung capacity (TLC) with participant effort, P was 128 ± 12 cmH2O and 118 ± 14 cmH2O, with DE and WE, respectively. The degree of difficulty in raising secretions improved markedly in both groups. The incidence of RTI per year fell from 1.3 ± 0.3 and 1.3 ± 0.5-0.3 ± 0.1 and 0.1 ± 0.1 for DE and WE groups, respectively (P< 0.01 for both when compared to pre-implant values and NS between DE and WE groups). The only significant side effect i.e. short-term autonomic dysreflexia was also similar between groups.

Conclusions: The results of this investigation indicate that both DE and WE result in comparable degrees of expiratory muscle activation, clinical benefits and side effects. Importantly, SCS to restore cough can be achieved with use of WE which can be placed using minimally invasive techniques and associated reduction in cost, surgical time and overall risk.Trial registration: ClinicalTrials.gov identifier: NCT00116337., NCT01659541, FDA IDE: G980267.

Keywords: Cough; Rehabilitation; Respiratory muscles; Spinal cord injury; Tetraplegia.

Figures

Figure 1

The effects of SCS (50 Hz, 40 V, 0.2 ms) on peak airflow (upper panel) (F) and airway pressure (P) generation (lower panel) with the DE and WE in single subjects, following a reconditioning period. See text for further explanation.

Figure 2

Mean changes in F and P generation during spontaneous maximum subject efforts and during SCS (50 Hz, 40 V, 0.2 ms) with the DE and WE at (functional residual capacity (FRC), total lung capacity (TLC) and TLC with subject effort). Mean F and P were significantly higher during SCS compared to spontaneous efforts (P 

Figure 3

Mean relationships between P and F generation during SCS (50 Hz, 40 V, 0.2 ms) with the DE and WE at FRC, TLC and TLC with subject effort. See text for further explanation.

Figure 4

Subject responses to frequency of need for conventional means of secretion clearance, severity of cough episodes, difficulty in raising secretions, and ease in raising sputum. There were significant improvements in all parameters of secretion management at 1-year follow-up of use of either the DE or WE to restore cough (P 

Figure 5

There was a significant reduction in the incidence of acute respiratory tract infections after 1 year of use of either DE or WE cough stimulation system. Respiratory tract infections per year fell from an average of 1.3 ± 0.3 and 1.3 ± 0.5–0.3 ± 0.1 and 0.1 ± 0.1 for the DE and WE, respectively (P