Simulation of Diaphragmatic Motor Unit Action Potentials Throughout the Respiratory Cycle Using a Dynamic Breathing Model.

Surface electromyography (sEMG) is a noninvasive measurement technique recording the temporal and spatial superposition of active motor units (MU) during muscle contraction. sEMG of the respiratory muscles is a promising method for measuring breathing effort and for quantifying patient-ventilator interactions. In the past, several mathematical sEMG models have been developed for isometric muscle contractions. However, these are not yet capable of representing the highly dynamic movement of breathing. To fill this gap, we developed a pipeline for simulating diaphragmatic MU action potentials (MUAPs) throughout the respiratory cycle. Our approach involved image registration between end-expiratory and end-inspiratory MRI data, discretization of the inspiratory phase into six finite element models, automated generation of muscle fiber pathways, and computation of MUAPs. A simulation of a linear electrode array produced plausible MUAP waveforms, which change across the breathing cycle due to muscle fiber pathway shortening and lateral shifts in electrode source distance. The modeling approach establishes a foundation for dynamic sEMG simulations of respiratory muscles.Clinical relevance— The proposed modeling pipeline for myoelectric simulations of the diaphragm across the respiratory cycle will enable physiological insights, the investigation of measurement parameters, and the analysis of signal processing algorithms in the context of respiratory sEMG.