Correlation of surface respiratory electromyography with esophageal diaphragm electromyography.

OBJECTIVES: To assess the correlation between surface respiratory electromyography(sEMG) and esophageal diaphragm electromyography(EMGdi) at different levels of neural respiratory drive (NRD).

DESIGN: Randomised parallel design controlled trial.

SETTING: The First Affiliated Hospital of Guangzhou Medical University.

PARTICIPANTS: 15 healthy subjects and 1 severe to very severe stable COPD patients were studied.

INTERVENTIONS: 15 healthy subjects performed incremental inspiratory threshold loading (ILT) and 15 stable COPD patients underwent noninvasive positive pressure ventilation (NPPV).The correlation between EMGdi and sEMG at different NRD levels was analyzed. EMGdi was performed with a multi-pair esophageal electrode catheter; sEMG were was performed by surface diaphragm EMG(located in right anterior axillary line and left anterior axillary line respectively expressed as sEMGdi(r) andsEMGdi(l))、surface parasternal EMG(sEMGpara),and surface sternocleidomastoid EMG(sEMGsc).Signals were normalized using the peak EMG expressed as EMG%max.

PRIMARY AND SECONDARY OUTCOME MEASURES: The mean ± standard deviation resting EMGdi%max was higher in patients with COPD than in healthy subjects (57.26%±15.45% vs13.64% ±4.96%, respectively; p < 0.001).During ILT and NPPV, EMGdi was correlated with sEMGdi (r), sEMGdi (1), sEMGpara and sEMGsc (r = 0.90, 0.87, 0.90, 0.90 and r = 0.92, 0.83, 0.92 and 0.71, respectively; all P < 0.001).

CONCLUSION: A strong relationship is present between NRD measured by EMGdi%max and NRD measured by sEMG%max. sEMG%max serves as a non-invasive marker of NRD.