The value of extra-diaphragmatic inspiratory muscle surface electromyography during postural control tasks in patients with chronic obstructive pulmonary disease.

Concurrent dysfunctions in postural control and diaphragm are observed in patients with chronic obstructive pulmonary disease (COPD). Measuring diaphragm activation traditionally involves transesophageal diaphragm electromyography (EMGdi), which is costly and relatively invasive. Extra-diaphragmatic inspiratory muscle surface electromyography may serve as a useful physiological marker for EMGdi. This study compared EMGdi amplitude with surface EMG amplitude of other inspiratory muscles, including sternocleidomastoid (sEMGscm), scalene (sEMGscal), and parasternal intercostal muscles (sEMGic) during postural control tasks in nine patients with COPD (5 males; age: 65 ± 6 years; forced expiratory volume in the first second: 60 ± 27 % predicted). Simultaneous recordings of EMGdi, sEMGscm, sEMGscal, and sEMGic amplitudes were obtained during six postural control tasks involving upright standing with ballistic arm movements under different conditions of support surface (stable/foam), arm movement frequency (single/repetitive), and breathing modes (normal/breath-hold at end-expiration). EMG amplitudes were normalized to each muscle's maximum voluntary contraction. A linear mixed model with Bonferroni-Holm post-hoc tests and Bland-Altman analyses were performed. There was a significant EMG-by-task interaction (p = 0.0223). The amplitude of EMGdi was significantly lower than sEMGic across all tasks (p < 0.0001 to 0.0007), while no significant differences were observed between EMGdi and sEMGscm or EMGdi and sEMGscal after Bonferroni-Holm correction (p = 0.019-0.858). Bland-Altman analyses indicated reasonable agreement between EMGdi and both sEMGscm and sEMGscal (mean biases: 1.8 % and -3.7 %), while sEMGic had a significantly higher overall bias of -20.7 %. These findings suggest that both sEMGscal and sEMGscm can serve as useful physiological markers for EMGdi in postural control assessments in patients with COPD. NEW & NOTEWORTHY. This study highlights the potential of extra-diaphragmatic inspiratory muscle surface electromyography as a physiological marker for transesophageal diaphragm electromyography during postural control tasks in patients with COPD, thereby reducing the need for costly and invasive measurements.