Approximately 40% of patients who receive invasive ventilation require more than four days of ventilator support. Every additional day of mechanical ventilation results in increased patient morbidity and mortality and increased economic cost. Mechanically ventilated patients often develop expiratory muscle weakness, which has been linked to failed extubation and weaning. Neuromuscular electrical stimulation (NMES) uses electrical pulses to induce a muscle contraction and has been shown to reduce or retard muscle atrophy. NMES applied to the abdominal wall muscles has been shown to improve respiratory function and assist ventilator weaning in spinal cord injury. Liberate Medical has previously shown that NMES applied to the abdominal wall muscles in synchrony with exhalation is feasible in patients receiving invasive mechanical ventilation. This study is a pivotal evaluation of the efficacy of exhalation synchronized abdominal NMES to assist ventilator weaning in critically ill patients. Active abdominal stimulation will be applied for 30 minutes twice per day (minimum of four hours between stimulation sessions), five days per week, for 28 days or ICU discharge, whichever comes first. In the VentFree treatment group, abdominal functional electrical stimulation (FES) will be applied with a frequency of 30 hertz (Hz) and a pulse width of 350µs to cause a strong visible or palpable muscle contraction. The stimulation amplitude will be set to 90% of the participant's maximum tolerable level that does not cause discomfort to the participant. Participant discomfort will be measured using a visual analog pain scale (VAS) with pain ratings from zero (no pain) to ten (worst pain). For participants who are unable to communicate their level of pain, the Behavioral Pain Scale (BPS) will be used. The stimulation will be titrated for each participant and each stimulation session. After the stimulation has been titrated, a visible or palpable contraction of the abdominal wall will be confirmed. The stimulation will be evaluated every 10(± 2) minutes after the start of each stimulation session and adjusted as necessary so that no discomfort is caused to the participant.

Public Health:

The objective of this study is to evaluate the efficacy of the VentFree Respiratory Muscle Stimulator (VentFree) in critically ill adult patients who require invasive mechanical ventilation, when compared to sham. This work has the potential to liberate patients more reliably from mechanical ventilation.

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