Correlation and compatibility between surface respiratory electromyography and transesophageal diaphragmatic electromyography measurements during treadmill exercise in stable patients with COPD

Figures & data

Figure 1 Schematic diagram of the position of the multipair esophageal electrode and surface electrode.

Notes: EMGdi,es: this was measured using a multipair esophageal electrode consisting of nine consecutive coils composed of five electrode pairs positioned in the esophagus and traversing the cardia. EMGdi,sur: the surface detecting electrode couple were separately placed at the intersection point of the sixth and eight intercostal space and at the anterior axillary line, at a distance of 5 cm. EMGpara: the surface detecting electrodes were placed bilaterally in the second intercostal space, about 3 cm parasternal and a reference ground electrode was placed at the sternum sternal angle. EMGsc: surface detecting electrodes were placed at 1/3 and 2/3 of the overall length of sternocleidomastoid and a reference ground electrode was placed at the suprasternal fossa.
Abbreviations: EMGdi,es, transesophageal diaphragmatic electromyogram activity; EMGdi,sur, surface diaphragmatic electromyogram activity; EMGpara, surface electromyogram activity of the parasternal intercostal muscles; EMGsc, surface electromyogram activity of the sternocleidomastoid muscles.

Table 1 Variance of transesophageal diaphragmatic electromyogram activity (EMGdi,es) and surface inspiratory electromyogram activity during treadmill exercise

Exercise stage (% of maximal exercise time)	RMSdi,es	p-value	RMSdi,sur	p-value	RMSpara	p-value	RMSsc	p-value
0%	8.35±0.49		14.10±0.72		8.75±0.44		8.35±0.59
10%	8.25±0.55		17.05±1.00	*	9.45±0.60		7.75±0.44
20%	11.65±0.67	*	18.35±0.99	*	11.60±0.75	*	7.70±0.47
30%	15.35±0.93	*	27.70±1.26	*	13.20±0.62	*	8.90±0.55
40%	14.95±0.83	*	27.90±1.41	*	14.40±0.68	*	10.05±0.51
50%	24.70±0.98	*	32.20±1.01	*	14.70±0.73	*	11.05±0.51	*
60%	44.60±2.26	*	62.75±2.84	*	43.05±1.96	*	14.85±0.59	*
70%	56.20±2.17	*	69.85±2.98	*	62.20±1.85	*	22.40±1.14	*
80%	59.90±2.15	*	65.60±2.93	*	64.70±3.60	*	28.50±1.54	*
90%	79.30±3.80	*	82.65±3.88	*	69.20±3.00	*	75.90±4.52	*
100%	83.15±4.04	*	84.70±5.08	*	83.95±4.17	*	95.30±2.54	*

Notes:

* Significantly increased compared to 0% exercise stage. Blank p-value spaces indicate no significant increase compared to 0% exercise stage.

Abbreviations: RMS, root mean square; RMSdi,es, RMS of transesophageal diaphragmatic electromyogram activity; RMSdi,sur, RMS of the surface electromyogram activity of the diaphragm; RMSpara, RMS of the surface electromyogram activity of the parasternal intercostal muscles; RMSsc, RMS of the surface electromyogram activity of the sternocleidomastoid muscles.

Figure 2 Waveform of esophageal pressure, transesophageal diaphragmatic electromyogram activity, and surface inspiratory electromyogram activity.

Abbreviations: EMGdi1, first transesophageal diaphragmatic electromyogram; EMGdi2, second transesophageal diaphragmatic electromyogram; EMGdi3, third transesophageal diaphragmatic electromyogram; EMGdi4, fourth transesophageal diaphragmatic electromyogram; EMGdi5, fifth transesophageal diaphragmatic electromyogram; EMGdi,sur, surface diaphragmatic electromyogram activity; EMGpara, surface electromyogram activity of the parasternal intercostal muscles; EMGsc, surface electromyogram activity of the sternocleidomastoid muscles; Pes, esophageal pressure.

Figure 3 Changing characteristics of RMSdi,es and surface inspiratory electromyogram activity during increased treadmill exercise capacity.

Notes: (A) Changing characteristics of RMSdi,es, (B) RMSdi,sur, (C) RMSpara, (D) and RMSsc.
Abbreviations: RMS, root mean square; RMSdi,es, RMS of transesophageal diaphragmatic electromyogram activity; RMSdi,sur, RMS of the surface electromyogram activity of the diaphragm; RMSpara, RMS of the surface electromyogram activity of the parasternal intercostal muscles; RMSsc, RMS of the surface electromyogram activity of the sternocleidomastoid muscles.

Figure 4 Scatter plot for correlation between RMSdi,es and RMS of the surface inspiratory muscles EMG.

Notes: EMG measurements were made during increased treadmill exercise capacity. (A) Scatter plots for correlation analysis between the RMSdi,es and the RMSdi,sur, (B) the RMSdi,es and the RMSpara, (C) and the RMSdi,es and the RMSsc.
Abbreviations: RMS, root mean square; EMG, electromyogram; RMSdi,es, RMS of transesophageal diaphragmatic electromyogram activity; RMSdi,sur, RMS of the surface electromyogram activity of the diaphragm; RMSpara, RMS of the surface electromyogram activity of the parasternal intercostal muscles; RMSsc, RMS of the surface electromyogram activity of the sternocleidomastoid muscles.

Figure 5 Bland-Altman plots for reliability of estimation between RMSdi,es and RMS of surface inspiratory muscles EMG.

Notes: EMG measurements were made during increased treadmill exercise capacity. (A) Bland-Altman plots for absolute reliability (means vs differences) between the RMSdi,es and the RMSdi,sur; (B) the RMSdi,es and the RMSpara; (C) and the RMSdi,es and the RMSsc.
Abbreviations: RMS, root mean square; EMG, electromyogram; RMSdi,es, transesophageal diaphragmatic electromyogram activity; RMSdi,sur, RMS of the surface electromyogram activity of the diaphragm; RMSpara, RMS of the surface electromyogram activity of the parasternal intercostal muscles; RMSsc, RMS of the surface electromyogram activity of the sternocleidomastoid muscles.