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

Abdominal Function Electrical Stimulation to Improve Cough Peak Flow After Spinal Cord Injury: A Multicenter Randomized Controlled Trial

The goal of this clinical trial is to learn if abdominal functional electrical stimulation (FES) using the VentFree Respiratory Muscle Stimulator improves cough strength in adults with a new spinal cord injury (SCI). It will also learn about the safety of abdominal FES in this population. The main questions it aims to answer are:

Does abdominal FES improve cough peak flow (a measure of cough strength) compared to cough training alone? Does abdominal FES reduce the number of respiratory complications (such as pneumonia or atelectasis)? What medical problems do participants have when receiving abdominal FES?

Researchers will compare abdominal FES (active treatment) to supervised cough training without stimulation (control) to see if abdominal FES improves cough function after spinal cord injury.

Participants will:

Receive abdominal FES or perform supervised cough training 5 days per week for up to 6 weeks during inpatient rehabilitation Have cough strength and breathing function measured at the start of the study and every week during treatment Complete quality of life and bowel function questionnaires at multiple time points Have a follow-up visit or phone call 4 weeks after completing treatment

Study Overview

• Status: Not yet recruiting
• Conditions: Respiratory Insufficiency; Spinal Cord Injuries (SCI)
• Intervention / Treatment: Device: Respiratory Muscle Stimulator; Behavioral: Supervised Cough Training

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Estimated): 150
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Director of Clinical Operations; Phone Number: 833-203-4663; Email: senen@liberatemedical.com
• Study Contact Backup: Name: Head of Clinical Affairs; Phone Number: 833-203-4663; Email: christopher@liberatemedical.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Adults (≥ 22 years of age) admitted to rehabilitation with a new SCI.
2. New non-progressive SCI occurring in the past 3 to 8 weeks.
3. Neurological level of injury of C1-T5.
4. American Spinal Injuries Association Impairment Scale A to C.
5. CPF of <160 L/min (Note: A CPF of <270 L/min has been shown to be associated with decreased secretion clearance and increased respiratory complications, while a CPF of <160 L/min has been shown to lead to an ineffective cough).
6. Not dependent on mechanical ventilation (people dependent on mechanical ventilation are at greatly increased risk of respiratory complications and are excluded due to this heterogeneity).
7. Able to sit upright.
8. Expected to remain in rehabilitation for at least another 3 weeks.

Exclusion Criteria:

1. Respiratory complications in previous 24 hours (screening out iatrogenic complications).
2. Chronic respiratory disease.
3. No contraction of the abdominal wall muscles in response to abdominal NMES.
4. Open abdominal surgery ≤ 4 weeks prior to enrollment.
5. Have yet to undergo spinal surgery to stabilize injury, where required.
6. Body mass index >40 kg/m2.
7. Pacemaker (external or internal) or implanted electronic device (e.g., a defibrillator).
8. Known or expected to be pregnant.
9. Placed on a palliative/supportive care only pathway.

10. Receiving any of the following as standard of care:

    • Abdominal FES
    • Inspiratory or Expiratory muscle training
    • Transcutaneous or implanted thoracolumbar spinal stimulation

11. Participating in any of the following:

    • A study with the same or similar primary endpoint
    • A study investigating electrical stimulation or respiratory muscle therapy
    • Any study in which the investigator determines may interfere with the results of this study
12. Unable or unwilling to comply with protocol requirements, including assessments, tests, and follow-up visits including facial or dental trauma.
13. Any other medical condition which in the opinion of the Investigator will make participation medically unsafe or interfere with the study results.
14. Unable to provide informed consent.
15. Unwilling to provide informed consent.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Abdominal Functional Electrical Stimulation (Active Treatment); Participants receive abdominal FES using the VentFree Respiratory Muscle Stimulator 5 days per week for up to 6 weeks or until hospital discharge, whichever comes first. Abdominal FES is applied during 3 sets of 10 coughs (approximately 7 seconds between each cough, 3 to 5 minutes between sets) followed by 30 minutes of quiet breathing. 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 without discomfort. Treatment is delivered at the participant's bedside with the participant sitting upright. Active treatment is applied as an adjunct to standard of care.	Device: Respiratory Muscle Stimulator; Transcutaneous neuromuscular electrical stimulation (NMES) device that applies abdominal functional electrical stimulation (FES) to the abdominal wall muscles in synchrony with the expiratory phase of breathing. The device consists of a control unit, nasal-oral cannula (used to detect breathing phase), disposable transcutaneous stimulation electrodes, and power supply. Electrodes are placed posterolaterally to activate the transversus abdominis and internal and external oblique muscles. Stimulation parameters are 30 Hz / 350 µs during quiet breathing and 50 Hz / 400 µs during coughing. Stimulation amplitude is titrated per session to achieve a strong visible abdominal wall contraction without discomfort, expected to be between 50 mA and 100 mA. Stimulation electrodes and nasal-oral cannula are replaced every five days of treatment.
Active Comparator: Supervised Cough Training (Control); Participants perform 3 sets of 10 supervised volitional coughs per day (approximately 7 seconds between each cough, 3 to 5 minutes between sets), 5 days per week for up to 6 weeks or until hospital discharge, whichever comes first. No active stimulation is applied. Training is delivered at the participant's bedside with the participant sitting upright. Control treatment is applied as an adjunct to standard of care.	Behavioral: Supervised Cough Training; Supervised volitional cough training performed without any active stimulation or device assistance. Participants perform 3 sets of 10 coughs per day with approximately 7 seconds between each cough and 3 to 5 minutes between sets, delivered by a trained research team member at the participant's bedside with the participant sitting upright.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Cough Peak Flow (CPF)	Cough peak flow measured in liters per minute (L/min) using the PneumotracTM (Vitalograph; Lenexa, KS) bedside respiratory muscle strength system, following European Respiratory Society (ERS) guidelines. Measurements are recorded with the participant seated upright in a chair/wheelchair or at 90 degrees in bed, breathing through a mouthpiece or tracheostomy valve piece with a nose clip in place. The participant is instructed to breathe in deeply to total lung capacity then cough as hard as possible. The test is performed 3 times and the greatest value is used for analysis. A CPF of less than 160 L/min indicates an ineffective cough, and a CPF of less than 270 L/min has been shown to be associated with decreased secretion clearance and increased respiratory complications in spinal cord injury.	baseline and weekly post randomization for 6 weeks or until hospital discharge, whatever comes first.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Effectiveness of Cough	Proportion of participants achieving a cough peak flow greater than 160 L/min, measured using the PneumotracTM (Vitalograph; Lenexa, KS), indicating attainment of an effective cough threshold.	At 6 weeks or hospital discharge, whatever comes first
Number of Participants with Respiratory Complications	roportion of participants sustaining a respiratory complication, defined as meeting 2 out of 3 of the following criteria: symptoms and signs suggestive of infection; respiratory symptoms or signs consistent with acute respiratory infection; chest X-ray infiltrates if available; AND receiving therapy for respiratory infection. Includes atelectasis, pneumonia, pleural effusion, and respiratory failure requiring mechanical ventilation. Extracted from medical records during treatment and through participant self-reporting at follow-up.	From enrollment to the end of the 4 week follow-up visit
Forced Vital Capacity (FVC)	Forced vital capacity measured in liters using the PneumotracTM (Vitalograph; Lenexa, KS) with the participant seated upright, following ATS/ERS guidelines. Three reproducible maneuvers within 10% of each other are required and the greatest value is used for analysis.	At 6 weeks or hospital discharge, whatever comes first
Forced Expiratory Volume in One Second (FEV1)	Forced expiratory volume in one second measured in liters using the PneumotracTM (Vitalograph; Lenexa, KS) with the participant seated upright, following ATS/ERS guidelines. Three reproducible maneuvers within 10% of each other are required and the greatest value is used for analysis.	At 6 weeks or hospital discharge, whatever comes first
Peak Expiratory Flow (PEF)	Peak expiratory flow measured in liters per minute using the PneumotracTM (Vitalograph; Lenexa, KS) with the participant seated upright, following ATS/ERS guidelines. Three reproducible maneuvers within 10% of each other are required and the greatest value is used for analysis.	At 6 weeks or hospital discharge, whatever comes first
Maximum Expiratory Pressure (MEP)	Maximum expiratory pressure measured in cmH2O using the PneumotracTM (Vitalograph; Lenexa, KS) with the participant seated upright. The participant breathes in to total lung capacity then performs a maximum forceful expiration, maintained for at least 1.5 seconds. Three reproducible maneuvers within 10% of each other are required and the greatest value is used for analysis.	At 6 weeks or hospital discharge, whatever comes first
Maximum Inspiratory Pressure (MIP)	Maximum inspiratory pressure measured in cmH2O using the PneumotracTM (Vitalograph; Lenexa, KS) with the participant seated upright. The participant performs a maximum forceful inspiration after an expiration to residual volume, maintained for at least 1.5 seconds. Three reproducible maneuvers within 10% of each other are required and the greatest value is used for analysis.	At 6 weeks or hospital discharge, whatever comes first
Quality of Life as Assessed by the SF-36	Health-related quality of life measured using the Short Form Health Survey modified and validated for wheelchair users (SF-36ww). The SF-36ww assesses eight health domains and produces physical and mental component summary scores. Higher scores indicate better health-related quality of life.	At 6 weeks or hospital discharge, whatever comes first, and 4 week follow-up visit
Bowel Function as Assessed by the Neurogenic Bowel Dysfunction Score	Bowel function measured using the Neurogenic Bowel Dysfunction Score, a validated 10-item self-report questionnaire evaluating severity of bowel dysfunction in spinal cord injury patients. Scores range from 0 to 47, with higher scores indicating more severe bowel dysfunction.	At baseline and weekly post randomization for 6 weeks or until hospital discharge, whatever comes first, and at 4-week follow-up
Global Impression of Benefit from Intervention	Participant-reported global impression of change assessed using an 8-point scale, with 0 representing no change and 7 representing a very much improved cough, to evaluate the perceived benefit of the intervention.	At the end of 6 weeks of treatment or hospital discharge, whatever comes first
Mortality	All-cause mortality. For any participant who dies before the 4-week post-intervention follow-up, time post injury and cause of death will be obtained from the participant's clinician.	At 6 weeks or hospital discharge, whatever comes first, and 4 week follow-up visit

Collaborators and Investigators

• Sponsor: Liberate Medical
• Collaborators: United States Department of Defense
• Investigators: Principal Investigator: Angus Mclachlan, PhD, Liberate Medical

Study record dates

Study Major Dates

• Study Start (Estimated): August 1, 2026
• Primary Completion (Estimated): June 1, 2028
• Study Completion (Estimated): June 1, 2028

Study Registration Dates

• First Submitted: May 29, 2026
• First Submitted That Met QC Criteria: May 29, 2026
• First Posted (Actual): June 4, 2026

Study Record Updates

• Last Update Posted (Actual): June 4, 2026
• Last Update Submitted That Met QC Criteria: May 29, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Rehabilitation; Muscle Strength; Abdominal Muscles; Tetraplegia; Functional Electrical Stimulation; Spinal Cord Injuries; Respiratory Muscles; Cough Peak Flow
• Additional Relevant MeSH Terms: Neurologic Manifestations; Central Nervous System Diseases; Nervous System Diseases; Wounds and Injuries; Respiratory Tract Diseases; Respiration Disorders; Trauma, Nervous System; Spinal Cord Diseases; Paralysis; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Respiratory Insufficiency; Spinal Cord Injuries; Quadriplegia
• Other Study ID Numbers: LM-SCI-P1; HT9425-25-1-0187 (Other Grant/Funding Number: United States Department of Defense (DoD))

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: Yes