First non-invasive magnetic phrenic nerve and diaphragm stimulation in anaesthetized patients: a proof-of-concept study

Alessandro Panelli; Hermann Georges Bartels; Sven Krause; Michael André Verfuß; Aline Michèle Grimm; Niklas Martin Carbon; Julius J Grunow; Diego Stutzer; Thomas Niederhauser; Laurent Brochard; Steffen Weber-Carstens; Stefan J Schaller

doi:10.1186/s40635-023-00506-6

First non-invasive magnetic phrenic nerve and diaphragm stimulation in anaesthetized patients: a proof-of-concept study

Intensive Care Med Exp. 2023 Apr 21;11(1):20. doi: 10.1186/s40635-023-00506-6.

Affiliations

¹ Department of Anesthesiology and Operative Intensive Care Medicine (CVK, CCM), Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität Zu Berlin, Charitéplatz 1, 10117, Berlin, Germany.
² Institute for Human Centered Engineering, Bern University of Applied Sciences, Biel, Switzerland.
³ Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, Unity Health Toronto, Toronto, ON, Canada.
⁴ Interdepartmental Division of Critical Care, University of Toronto, Toronto, Canada.
⁵ Department of Anesthesiology and Operative Intensive Care Medicine (CVK, CCM), Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität Zu Berlin, Charitéplatz 1, 10117, Berlin, Germany. stefan.schaller@charite.de.
⁶ Department of Anesthesiology and Intensive Care, School of Medicine, Klinikum Rechts Der Isar, Technical University of Munich, Munich, Germany. stefan.schaller@charite.de.

Abstract

Background: Mechanical ventilation has side effects such as ventilator-induced diaphragm dysfunction, resulting in prolonged intensive care unit length of stays. Artificially evoked diaphragmatic muscle contraction may potentially maintain diaphragmatic muscle function and thereby ameliorate or counteract ventilator-induced diaphragm dysfunction. We hypothesized that bilateral non-invasive electromagnetic phrenic nerve stimulation (NEPNS) results in adequate diaphragm contractions and consecutively in effective tidal volumes.

Results: This single-centre proof-of-concept study was performed in five patients who were 30 [IQR 21-33] years old, 60% (n = 3) females and undergoing elective surgery with general anaesthesia. Following anaesthesia and reversal of muscle relaxation, patients received bilateral NEPNS with different magnetic field intensities (10%, 20%, 30%, 40%); the stimulation was performed bilaterally with dual coils (connected to one standard clinical magnetic stimulator), specifically designed for bilateral non-invasive electromagnetic nerve stimulation. The stimulator with a maximal output of 2400 Volt, 160 Joule, pulse length 160 µs at 100% intensity was limited to 50% intensity, i.e. each single coil had a maximal output of 0.55 Tesla and 1200 Volt. There was a linear relationship between dosage (magnetic field intensity) and effect (tidal volume, primary endpoint, p < 0.001). Mean tidal volume was 0.00, 1.81 ± 0.99, 4.55 ± 2.23 and 7.43 ± 3.06 ml/kg ideal body weight applying 10%, 20%, 30% and 40% stimulation intensity, respectively. Mean time to find an initial adequate stimulation point was 89 (range 15-441) seconds.

Conclusions: Bilateral non-invasive electromagnetic phrenic nerve stimulation generated a tidal volume of 3-6 ml/kg ideal body weight due to diaphragmatic contraction in lung-healthy anaesthetized patients. Further perspectives in critically ill patients should include assessment of clinical outcomes to confirm whether diaphragm contraction through non-invasive electromagnetic phrenic nerve stimulation potentially ameliorates or prevents diaphragm atrophy.

Keywords: Artificial; Magnetic field therapy; Mechanical ventilation weaning; Muscle weakness; Phrenic nerve; Respiration.