A Quantitative Comparison of Electrode Positions for Respiratory Surface EMG

Respiratory surface electromyography (sEMG) is a promising physiological signal for analyzing respiratory effort, patient-ventilator asynchrony, and respiratory training. In clinical research, a wide variety of different setups are used and no consensus has yet been reached on the positioning of electrodes. Therefore, this work aims to quantitatively compare both unilateral and bilateral bipolar electrode leads.

Recordings of diaphragmatic and intercostal muscle activity were performed in 20 young and healthy adults using a setup with 64 electrodes placed in relation to prominent anatomical lines. Subjects completed three breathing maneuvers: 300 s quiet breathing, 5 maximum inspiratory pressure (MIP) trials, and 15 breaths of resistance breathing at 20 % of the MIP. To quantify the performance of differential electrode leads, three metrics were determined: the ratio between inspiratory muscle activity and (1) baseline noise (SNR_base), (2) expiratory muscle activity (SNR_exp), and (3) ECG interference (SNR_EMG-ECG).

The study revealed considerable differences between bipolar electrode positions. Our results support the use of bilateral positions on the midclavicular line and parasternal line for measuring diaphragm and intercostal activity. For intercostal muscles, there is a high flexibility in positioning electrodes more lateral or medial, if necessary. Unilateral leads do not appear to outperform the bilateral configuration as SNR metrics were consistently smaller.

This study provides recommendations for electrode placements and is a first step towards standardization of respiratory sEMG measurements.

This electrode lead standardization will be essential to increase clinical acceptance in the future.