Economic Consequences of an Implanted Neuroprosthesis in Subjects with Spinal Cord Injury for Restoration of an Effective Cough

Impact of the cough stimulation system on the care burden and life quality of caregivers of tetraplegics

OBJECTIVES

To determine caregiver burden and quality of life of primary family caregivers of participants with cervical SCI before and after use of the cough stimulation system (CSS).

DESIGN

Prospective assessment at four timepoints via questionnaire responses.

SETTING

Out-patient hospital, United States.

PARTICIPANTS

15 primary family caregivers of participants with cervical SCI completed questionnaires including a respiratory care burden index (n = 15) and a commonly employed caregiver burden inventory (n = 9), before and at the 6-month, 1-year and 2-year timepoints following use of the CSS.

RESULTS

SCI participants had significant clinical improvements in terms of restoration of an effective cough and ability to manage airway secretions with use of the CSS. Restoration of expiratory muscle function with use of the CSS also resulted in less caregivers (CG) stress, greater control of their participants' breathing problems, and improvement in quality of life. Results of the caregiver burden inventory demonstrated marked reductions in caregiver burden in development items, physical health and social relationship. Overall caregiver burden fell from 43.4 ± 13.8 pre-implant to 32.4 ± 7.9 (P = 0.06), 31.7 ± 10.5 (P = 0.05), and 26.5 ± 9.3 (P = 0.01) at the 6-month, 1-year and 2-year timepoints.

CONCLUSION

Use of the CSS by cervical SCI participants results in restoration of an effective cough with significant clinical benefits. While caregiver burden is very high in primary family caregivers, they derive marked improvement in caregiver burden and quality of life with implementation of this device.Trial registration: ClinicalTrials.gov identifier: NCT00116337.Trial registration: ClinicalTrials.gov identifier: NCT01659541.

Effects of restoration of cough via spinal cord stimulation on subject quality of life

Objectives

To determine participant quality of life before and after use of the cough stimulation system (Cough System).

Design

Prospective assessment of life quality at 4 timepoints via questionnaire responses.

Setting

Out-patient hospital, United States.

Participants

28 subjects with spinal cord injury (SCI) completed life quality assessment questionnaires before and at the 28- 40- and 52-week timepoints following use of the Cough System.

Results

Each subject demonstrated significant clinical improvements in terms of restoration of an effective cough and ability to manage airway secretions with use of the Cough System. Positive airway pressures and peak expiratory airflows approached values associated with a normal cough. Related to cough/secretion management, use of this system also resulted less interference with family life and daily activities, less financial difficulties, less requirement for caregiver assistance, less stress, less embarrassment and greater control of their breathing problems (p < 0.01), for each comparison). There also significant improvements in that their overall health and quality of life (p < 0.01, for each comparison). Subjects also reported greater ease in breathing, restored ability to sneeze and enhanced mobility. The incidence of acute respiratory tract infections fell from 1.3 ± 0.3 to 0.2 ± 0.1 events/subject year (p < 0.01). Ten subjects developed mild hemodynamic effects consistent with autonomic dysreflexia that abated completely with continued use of the Cough System. Some subjects experienced mild leg jerks during SCS, which were well tolerated and abated completely with reduction in stimulus amplitude, No subjects reported bowel or bladder leakage.

Conclusion

Use of the Cough System by SCI subjects is a safe and efficacious method which significantly improves life quality and has the potential to reduce the mortality and morbidity associated with SCI.

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

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.

Effects of Lower Thoracic Spinal Cord Stimulation on Bowel Management in Individuals With Spinal Cord Injury

OBJECTIVE

To systematically determine whether use of the spinal cord stimulation (SCS) system to restore cough may improve bowel management (BM) in individuals with spinal cord injury (SCI).

DESIGN

Experimental studies (clinical trial).

SETTING

Inpatient hospital setting for electrode insertion; outpatient setting for measurement of respiratory pressures; home setting for application of SCS.

PARTICIPANTS

Participants (N=5) with cervical SCI.

INTERVENTION

A fully implantable SCS cough system was surgically placed in each subject. SCS was applied at home, 2-3 times/d, on a chronic basis, every time bowel regimen was performed and as needed for secretion management. Stimulus parameters were set at values resulting in near maximum airway pressure generation, which was used as an index of expiratory muscle strength. Participants also used SCS during their bowel routine.

MAIN OUTCOME MEASURES

Airway pressure generation achieved with SCS. Weekly completion of Bowel Routine Log including BM time, mechanical measures, and medications used.

RESULTS

Mean pressure during spontaneous efforts was 30±8 cmH₂O. After a period of reconditioning, SCS resulted in pressure of 146±21 cmH₂O. The time required for BM routines was reduced from 118±34 minutes to 18±2 minutes (P<.05) and was directly related to the magnitude of pressure development during SCS. Mechanical methods for BM were completely eliminated in 4 patients. No patients experienced fecal incontinence as result of SCS. Each participant also reported marked overall improvement associated with BM.

CONCLUSIONS

Our results of this pilot study suggest that SCS to restore cough may be a useful method to improve BM and life quality for both patients with SCI and their caregivers. Our results indicate that the improvement in BM is secondary to restoration of intra-abdominal pressure development.

Activation of the expiratory muscles via lower thoracic high frequency spinal cord stimulation in awake animals

Lower thoracic spinal cord stimulation is an effective method of restoring an effective cough in participants with complete spinal cord injury. The high voltage requirements however significantly limits this application in subjects with intact lower chest wall sensation. In anesthetized animals, we have shown that the expiratory muscles can also be effectively activated with low stimulus currents (1 mA) but with high stimulus frequencies (HF-SCS -500 Hz). In 3 intact, awake pigs the responses to HF-SCS, were evaluated. HF-SCS was associated with marked expansion of the abdominal wall and external oblique EMG activity without any associated changes in heart rate or vocalization. During a terminal procedure under general anesthesia, responses to HF-SCS were re-assessed. Abdominal movement and EMG were similar to that observed in the awake state. HF-SCS (1.5 mA) resulted in an airway pressure of 65 ± 2cmH₂O. Our results indicate that lower thoracic HF-SCS may be a useful method to restore an effective cough in patients with intact chest wall sensation.

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

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.

Case report: Minimally invasive method to activate the expiratory muscles to restore cough

CONTEXT

Spinal cord stimulation (SCS) via disc electrodes surgically placed via laminotomy incisions has been shown to restore an effective cough in subjects with spinal cord injury (SCI). The purpose of this study was to evaluate a new method of expiratory muscle activation utilizing spinal cord wire leads, which can be implanted with minimally invasive techniques.

METHODS

In a subject with SCI, parallel wire leads with two electrode contacts were inserted percutaneously through a needle, advanced to the T9, T11 spinal levels and connected to an implanted radiofrequency receiver. Stimulus parameters were set at values resulting in near maximum airway pressure generation (Paw) (40V, 50Hz, 0.2ms). Paw was measured at functional residual capacity (FRC) and total lung capacity (TLC) as an index of expiratory muscle strength.

RESULTS

Paw during spontaneous efforts was 20 cmH₂O (8.6% predicted). Bipolar (T9-T11) SCS resulted in Paw of 84 and 103 cmH₂O, at FRC and TLC respectively. Monopolar (T9 only) SCS resulted in Paw of 61 and 86 cmH₂O, at FRC and TLC respectively. This subject experienced much greater ease in raising secretions with use of SCS and no longer required other methods of secretion management.

CONCLUSION

SCS via wire leads, which can be implanted using minimally invasive techniques, may provide a new useful method to restore an effective cough and possibly reduce the morbidity and mortality associated with respiratory tract infections in patients with SCI.

Effects of expiratory muscle activation via high-frequency spinal cord stimulation

In persons with spinal cord injury, lower thoracic low-frequency spinal cord stimulation (LF-SCS; 50 Hz, 15 mA) is a useful method to restore an effective cough. Unfortunately, the high-stimulus-amplitude requirements and potential activation of pain fibers significantly limit this application in persons with intact sensation. In this study, the mechanism of the expiratory muscle activation, via high-frequency SCS (HF-SCS; 500 Hz, 1 mA) was evaluated in dogs. In group 1, the effects of electrode placement on airway pressure generation (P) was evaluated. Maximal P occurred at the T9-T10 level with progressive decrements in P at more rostral and caudal levels for both LF-SCS and HF-SCS. In group 2, electromyographic (EMG) latencies of internal intercostal muscle (II) activation were evaluated before and after spinal root section and during direct motor root stimulation. Onset time of II EMG activity during HF-SCS was significantly longer (3.84 ± 1.16 ms) than obtained during direct motor root activation (1.61 ± 0.10 ms). In group 3, P and external oblique (EO) EMG activity, before and after sequential spinal section at the T11-T12 level, were evaluated. Bilateral dorsal column section significantly reduced EO EMG activity below the section and resulted in a substantial fall in P. Subsequent lateral funiculi section completely abolished those activities and resulted in further reductions in P. We conclude that 1) activation of the expiratory muscles via HF-SCS is dependent entirely on synaptic spinal cord pathways, and 2) HF-SCS at the T9 level produces a comparable level of muscle activation with that achieved with LF-SCS but with much lower stimulus amplitudes. NEW & NOTEWORTHY The findings in the present study suggest that lower thoracic high-frequency spinal cord stimulation with low stimulus currents results in sufficient activation of the expiratory muscles via spinal circuitry to produce large positive airway pressures sufficient to generate an effective cough mechanism. This method, therefore, may be applied in patient populations with intact sensation such as stroke and amyotrophic lateral sclerosis to restore an effective cough.