Ultrafast Ultrasound Plane Wave Imaging As a Novel non-Invasive Technique to Assess Diaphragm Contractility in Response to Phrenic Nerve Magnetic Stimulation

Diaphragm monitoring relies on the measurement of trans diaphragmatic pressure (Pdi) during cervical magnetic stimulation (CMS). Specifically, twitch Pdi (Pditw) is measured using esophageal and gastric probes. Such probes are invasive and require a high level of expertise, and non-invasive methods to assess diaphragm function are necessary. Here we test how maximal diaphragm tissue velocity (Vdimax) is related to stimulation intensity and Pditw, during CMS. Ultrafast ultrasound of the diaphragm was performed in 13 healthy subjects at various intensity levels. We show that Vdimax is strongly related to stimulation intensity and Pditw, in all participants. Within-day reliability for Vdimax was strong and similar to that of Pditw. Our findings open prospects for the non-invasive monitoring of Pditw in clinical populations. Indeed, the relative changes in Pditw over time may be monitored by assessing the relative changes in Vdimax.