Surface mechanomyography and electromyography provide non-invasive indices of inspiratory muscle force and activation in healthy subjects

Manuel Lozano-García,Leonardo Sarlabous,Raimon Jané,Caroline J Jolley,John Moxham,Gerrard F Rafferty,Abel Torres

doi:10.1038/s41598-018-35024-z

Abstract

The current gold standard assessment of human inspiratory muscle function involves using invasive measures of transdiaphragmatic pressure (Pdi) or crural diaphragm electromyography (oesEMGdi). Mechanomyography is a non-invasive measure of muscle vibration associated with muscle contraction. Surface electromyogram and mechanomyogram, recorded transcutaneously using sensors placed over the lower intercostal spaces (sEMGlic and sMMGlic respectively), have been proposed to provide non-invasive indices of inspiratory muscle activation, but have not been directly compared to gold standard Pdi and oesEMGdi measures during voluntary respiratory manoeuvres. To validate the non-invasive techniques, the relationships between Pdi and sMMGlic, and between oesEMGdi and sEMGlic were measured simultaneously in 12 healthy subjects during an incremental inspiratory threshold loading protocol. Myographic signals were analysed using fixed sample entropy (fSampEn), which is less influenced by cardiac artefacts than conventional root mean square. Strong correlations were observed between: mean Pdi and mean fSampEn |sMMGlic| (left, 0.76; right, 0.81), the time-integrals of the Pdi and fSampEn |sMMGlic| (left, 0.78; right, 0.83), and mean fSampEn oesEMGdi and mean fSampEn sEMGlic (left, 0.84; right, 0.83). These findings suggest that sMMGlic and sEMGlic could provide useful non-invasive alternatives to Pdi and oesEMGdi for the assessment of inspiratory muscle function in health and disease.

Highlights

The ability to measure respiratory muscle function is clinically important in the assessment of neuromuscular[1] and respiratory disease[2]
Inspiratory muscle fibre vibration can be recorded by mechanomyography, using skin-surface accelerometers positioned on the chest wall over the lower intercostal spaces, proximal to the zone of apposition of the diaphragm[13,14,15]
Very strong correlations were observed between non-invasive sEMGlic and invasive oesEMGdi measures

Summary

Introduction

The ability to measure respiratory muscle function is clinically important in the assessment of neuromuscular[1] and respiratory disease[2]. Accurate assessment of diaphragm pressure generation and activation, requires invasive procedures, such as the balloon-catheter technique, to measure transdiaphragmatic pressure (Pdi)[7], or crural diaphragm electromyography using a multipair oesophageal electrode (oesEMGdi)[2,8,9,10] These invasive tests can be uncomfortable for patients and require some skill from the operator involved. The use of sMMG to assess inspiratory muscle function has been relatively unexplored, and sMMGlic has not been compared with gold standard invasive measures of Pdi, during voluntary respiratory manoeuvres. Measurements of both sEMGlic and sMMGlic are, contaminated by cardiac artefacts, especially using the average rectified value or root mean square (RMS) as standard. We aimed to compare the utility of RMS- and fSampEn-based techniques to analyse oesEMGdi signals, hypothesizing that there would be a close positive relationship between RMS- and fSampEn-derived measures of oesEMGdi

Objectives

Results

Conclusion