Assessment of inspiratory muscle activation using surface mechanomyography in COPD patients with comorbid heart failure

Abstract

Introduction: The muscle mechanomyogram (sMMG) quantifies the lateral oscillations of contracting muscle fibres. There is a close relationship between lower intercostal space sMMG (sMMGlic) and inspiratory muscle force during inspiratory threshold loading (ITL) in healthy subjects. We hypothesized that the slope of relationship between sMMGlic and inspiratory muscle force during ITL would be similar in chronic obstructive pulmonary disease (COPD) and in COPD-heart failure overlap (COPD-HF). Methods: Bilateral sMMGlic was recorded simultaneous with mouth pressure (Pmo) in 11 COPD (9 male, 66 (64-77) years, FEV1 44.7 (37.6-61.0) %pred, maximal inspiratory mouth pressure (PImax) 56.4 (49.7-74.8) cmH2O), and in 4 COPD-HF patients (3 male, 82 (72-82) years, FEV1 51.0 (41.2-70.8) %pred, PImax 35.9 (23.9-57.4) cmH2O) during ITL to 36% of PImax. sMMGlic signals were analysed using fixed sample entropy (fSampEn). Relationships between area under the curve of fSampEn sMMGlic and Pmo were assessed by correlation analysis. Results: Similar positive relationships between sMMGlic and Pmo in both COPD and COPD-HF groups (Fig. 1) were observed. Conclusions: These data suggest the potential value of sMMGlic as a novel index of inspiratory muscle activation in both COPD and COPD-HF. Further quantitative analysis of sMMGlic in COPD and COPD-HF in larger cohorts of these patients is required.