Reliability of the diaphragmatic compound muscle action potential evoked by cervical magnetic stimulation and recorded via chest wall surface EMG.

INTRODUCTION: Stimulation of the phrenic nerve via cervical magnetic stimulation (CMS) elicits a compound muscle action potential (CMAP) that allows for assessment of diaphragm activation. The reliability of CMS to evoke the CMAP recorded by chest wall surface EMG has yet to be comprehensively examined.

METHODS: CMS was performed on healthy young males (n=10) and females (n=10). Surface EMG electrodes were placed on the right and left hemi-diaphragm between the 6-8th intercostal spaces. CMAPs were analysed for: latency, duration, peak-to-peak amplitude, and area. Reliability within and between experimental sessions was assessed using intraclass correlation coefficients (ICC). Bilateral (right-left) and sex-based (male-female) comparisons were also made (independent samples t-test).

RESULTS: All CMAP characteristics demonstrated high reproducibility within (ICCs>0.96) and between (ICCs>0.89) experimental sessions. No statistically significant bilateral or sex-based differences were found (p>0.05).

DISCUSSION: CMS is a reliable and non-invasive method to evaluate phrenic nerve conduction.