Non-invasive electromagnetic phrenic nerve stimulation in critically ill patients - a feasibility study.

BACKGROUND: Electromagnetic stimulation of the phrenic nerve induces diaphragm contractions, but no coils for clinical use have been available. We recently demonstrated the feasibility of ventilation using bilateral transcutaneous non-invasive electromagnetic phrenic nerve stimulation (NEPNS) preoperatively in lung-healthy, normal-weight patients in a dose-dependent manner.

RESEARCH QUESTION: Is NEPNS feasible in critically ill patients in an ICU setting?

STUDY DESIGN AND METHODS: This feasibility non-randomized controlled study aimed to enroll patients within 36h of intubation, who were expected to remain ventilated for ≥72h. The intervention group received 15-minute bilateral transcutaneous NEPNS twice daily, while the control group received standard care. If sufficient, NEPNS was used without pressure support to ventilate the patient; pressure support was added if necessary to ventilate the patient adequately. The primary outcome was feasibility, measured as time to find the optimal stimulation position. Further endpoints were sessions performed according to the protocol or allowing a next-day catch-up session and tidal volume achieved with stimulation only reaching 3-6ml/kgIBW. A secondary endpoint was expiratory diaphragm thickness measured with ultrasound from Day 1 to 10 (or extubation).

RESULTS: The revised EU regulation mandated reapproval of medical devices, prematurely halting the study. Eleven patients (5 intervention, 6 control) were enrolled. The time to find an adequate stimulation position was 23 [12-62] seconds. The intervention twice daily was executed in 87% of cases, and 92% including a next-day catch-up session. Ventilation with 3-6ml/kgIBW was achieved in 732/1701 (43.0%) of stimulations with stimulation only and in 2511/4036 (62.2%) with additional pressure support. A decrease in diaphragm thickness was prevented by bilateral NEPNS (p=0.034) until day 10.

INTERPRETATION: Bilateral transcutaneous NEPNS was feasible in the ICU setting with the potential benefit of preventing diaphragm atrophy during mechanical ventilation; NEPNS ventilation effectiveness needs further assessment.