Influence of Parameter Selection in Fixed Sample Entropy of Surface Diaphragm Electromyography for Estimating Respiratory Activity

Luis Estrada,Leonardo Sarlabous,Abel Torres,Raimon Jané

doi:10.3390/e19090460

Abstract

Fixed sample entropy (fSampEn) is a robust technique that allows the evaluation of inspiratory effort in diaphragm electromyography (EMGdi) signals, and has potential utility in sleep studies. To appropriately estimate respiratory effort, fSampEn requires the adjustment of several parameters. The aims of the present study were to evaluate the influence of the embedding dimension m, the tolerance value r, the size of the moving window, and the sampling frequency, and to establish recommendations for estimating the respiratory activity when using the fSampEn on surface EMGdi recorded for different inspiratory efforts. Values of m equal to 1 and r ranging from 0.1 to 0.64, and m equal to 2 and r ranging from 0.13 to 0.45, were found to be suitable for evaluating respiratory activity. fSampEn was less affected by window size than classical amplitude parameters. Finally, variations in sampling frequency could influence fSampEn results. In conclusion, the findings suggest the potential utility of fSampEn for estimating muscle respiratory effort in further sleep studies.

Highlights

Assessment of respiratory muscle function provides valuable information for the diagnosis and treatment capabilities of patients with respiratory muscle weakness [1], for instance, in specialties such as respiratory medicine [2,3,4,5], intensive care [6,7], and sleep medicine [8,9,10,11,12,13]
This technique has the advantage of avoiding excessive filtering of the EMGdi signal while preserving most of its spectral information [20,29]. fixed sample entropy (fSampEn) is based on the Sample entropy (SampEn) technique and quantifies the amplitude variation of the complex components of the EMGdi signal while being less sensitive to deterministic signals, such as ECG
We report that the fSampEn measurements were strongly dependent on the sampling frequency of the surface EMGdi signal

Summary

Introduction

Assessment of respiratory muscle function provides valuable information for the diagnosis and treatment capabilities of patients with respiratory muscle weakness [1], for instance, in specialties such as respiratory medicine [2,3,4,5], intensive care [6,7], and sleep medicine [8,9,10,11,12,13]. Analyzing electromyographic signals of the respiratory muscles in routine clinical studies can provide useful complementary information for measuring respiratory effort [1]. Diaphragm electromyography (EMGdi) presents valuable information as an indirect measurement of the load exerted by the respiratory muscles [2]. EMGdi signals can be invasively recorded using multiple pairs of esophageal electrodes [8,9]. This technique is unpleasant for patients and of limited use in clinical practice [2]. Surface electromyography has been used for the non-invasive assessment of respiratory muscle function [1,4,10,11,12,13,14]. It is possible to record surface EMGdi signals with electrodes placed on the chest wall surface, near the zone of apposition of the diaphragm, as described in [15]

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Discussion

Conclusion