Abdominal Stimulation to Improve Cough After Spinal Cord Injury (COUFES)

Spinal cord injury (SCI) at the cervical or high thoracic level impairs the abdominal and intercostal muscles, reducing expiratory muscle strength and cough effectiveness. An impaired cough leads to secretion retention and respiratory complications, which are the leading cause of morbidity and mortality in the first year following SCI. Current standard-of-care techniques such as manually assisted coughing and mechanical insufflation-exsufflation can augment assisted cough but do not directly improve a patient's voluntary, unassisted cough function.

Abdominal functional electrical stimulation (FES) uses transcutaneous neuromuscular electrical stimulation (NMES) applied to the abdominal wall muscles in synchrony with the expiratory phase of breathing. This approach can recruit the abdominal muscles in the absence of voluntary or automatic muscle activation, making it particularly suited for use after SCI. Prior investigator-initiated studies and pilot randomized controlled trials have demonstrated that abdominal FES is safe and feasible in this population, and that repeated training with abdominal FES can produce longitudinal improvements in respiratory function including cough peak flow (CPF), forced vital capacity (FVC), and peak expiratory flow (PEF).

This is a prospective, randomized, single-blind (observer-blinded), multicenter superiority trial enrolling adults with a new non-progressive SCI at neurological levels C1-T5 (AIS A-C) who are in the inpatient rehabilitation phase of care and have a CPF below 160 L/min. Approximately 150 participants will be enrolled at up to 20 sites in North America and randomized 1:1 to active treatment or control. Randomization is stratified by site and injury level.

Participants in the active group receive abdominal FES during 3 sets of 10 coughs followed by 30 minutes of quiet breathing, 5 days per week, for up to 6 weeks or until hospital discharge. Stimulation is delivered at 30 Hz / 350 µs during quiet breathing and 50 Hz / 400 µs during coughing, with amplitude titrated to achieve a strong visible abdominal wall contraction. Participants in the control group perform 3 sets of 10 supervised volitional coughs per day, 5 days per week, for the same duration, with no active stimulation.

The primary endpoint is CPF measured 4 weeks post-randomization. Secondary endpoints include additional respiratory function measures (FVC, FEV1, PEF, MIP, MEP), effectiveness of cough (proportion achieving CPF >160 L/min), respiratory complications, bowel function (Neurogenic Bowel Dysfunction Score), quality of life (SF-36ww), global impression of benefit, and mortality. All respiratory function measurements follow ATS/ERS guidelines. Outcome assessors and radiographers are blinded to treatment allocation.

The sample size of 150 participants (75 per group) provides 90% power to detect a 42 L/min between-group difference in CPF improvement from baseline, assuming a standard deviation of 72 L/min and a one-sided significance level of 0.025, with 15% attrition allowance.