Abdominal Functional Electrical Stimulation to Assist Ventilator Weaning in Acute Tetraplegia: A Cohort Study

Abstract

Background: Severe impairment of the major respiratory muscles resulting from tetraplegia reduces respiratory function, causing many people with tetraplegia to require mechanical ventilation during the acute stage of injury. Abdominal Functional Electrical Stimulation (AFES) can improve respiratory function in non-ventilated patients with sub-acute and chronic tetraplegia. The aim of this study was to investigate the clinical feasibility of using an AFES training program to improve respiratory function and assist ventilator weaning in acute tetraplegia.

Methods: AFES was applied for between 20 and 40 minutes per day, five times per week on four alternate weeks, with 10 acute ventilator dependent tetraplegic participants. Each participant was matched retrospectively with a ventilator dependent tetraplegic control, based on injury level, age and sex. Tidal Volume (VT) and Vital Capacity (VC) were measured weekly, with weaning progress compared to the controls.

Results: Compliance to training sessions was 96.7%. Stimulated VT was significantly greater than unstimulated VT. VT and VC increased throughout the study, with mean VC increasing significantly (VT: 6.2 mL/kg to 7.8 mL/kg VC: 12.6 mL/kg to 18.7 mL/kg). Intervention participants weaned from mechanical ventilation on average 11 (sd: ± 23) days faster than their matched controls.

Conclusion: The results of this study indicate that AFES is a clinically feasible technique for acute ventilator dependent tetraplegic patients and that this intervention may improve respiratory function and enable faster weaning from mechanical ventilation.

Trial registration: ClinicalTrials.gov NCT02200393.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1. CONSORT flow diagram.

Fig 2. Study time line.

Fig 3. Schematic diagram of electrode placement.

Fig 4. Sensors used to record respiratory activity.

Black lines indicate direction of data.

Fig 5. Weight corrected tidal volume.

A. Group weight corrected tidal volume (VT /kg) (mean ± standard deviation) for 9 participants, recorded at 9 weekly assessment sessions. A black line represents stimulated, and a blue line unstimulated, breaths. A black X indicates stimulated VT /kg was statistically significantly different to unstimulated VT /kg. B. Unstimulated VT /kg of nine participants, recorded at nine weekly assessment sessions. Participant 7, who was the only participant not to wean from ventilation within the study duration, is represented by a blue line. A VT /kg of 5 mL/kg is represented by a dashed black line, with this value possibly serving as an indicator of weaning success. A solid black line along the bottom of both plots represents one week of AFES training.

Fig 6. Weight corrected vital capacity.

A. Group weight corrected vital capacity (VC/kg) (mean ± standard deviation) for 9 participants, recorded at 9 weekly assessment sessions. A black line represents stimulated, and a blue line unstimulated, breaths. Black * and blue * indicate that stimulated and unstimulated mean was statistically significantly different to the mean at first assessment, respectively. B. Unstimulated VC/kg of nine participants, recorded at nine weekly assessment sessions. Participant 7, who was the only participant not to wean from ventilation within the study duration, is represented by a blue line. A solid black line along the bottom of both plots represents one week of AFES training.