Involvement of Respiratory Muscles During the Timed Inspiratory Effort Index Measurement With Surface Electromyography

Abstract

BACKGROUND: Mechanical ventilation is a life-support therapy that can be associated with respiratory muscle dysfunction that may perturb the weaning process. The timed inspiratory effort (TIE) index is a recently proposed weaning index that has been reported to be effective in predicting successful weaning. We sought to analyze the respiratory muscle groups involved with the TIE index measurement utilizing the surface electromyography (sEMG). METHODS: We conducted a prospective observational study including 46 mechanically ventilated subjects. The variable analyzed with sEMG was the root mean square (RMS) for correlation with the degree of recruitment of motor units and strength. The data were obtained along the 60 s of the TIE index measurement and analyzed in each one of the 3 20-s intervals. Pooled and individual muscle RMS values were analyzed comparing success and failure groups. P < .05 was considered significant. RESULTS: The median (interquartile range) age of the participants was 80 (71-87) y. The pooled sEMG data showed that muscle strength increased over time, following the profile observed for maximum inspiratory pressure, irrespective of the analyzed group. However, in line with the findings regarding maximum inspiratory pressure, the RMS medians were statistically higher at every 20-s interval in the success group. Diaphragm strength increased over time, with values reaching statistically significant differences at the end of the observation period, but only in the success group. In addition, diaphragm strength was statistically higher during the whole test in the success group. Finally, there was a substantial increase in sternocleidomastoid strength over time after 40 s of observation, which was not observed in the scalene muscles. CONCLUSIONS: Subjects succeeding in a weaning trial had higher muscle strength, confirmed in the pooled and the individual sEMG analysis. A vigorous diaphragm with low fatigue potential seems essential for successful weaning; the sternocleidomastoid may also be of importance in this regard.

Surface electromyography signal processing and evaluation on respiratory muscles of critically ill patients: A systematic review

“…Table 2 shows the processing data for the sEMG analysis. Sampling rate was mentioned in twelve studies (75%) obtaining variations between 500 and 10,000 Hz [ 6 , 17 – 19 , 21 , 23 – 27 , 29 , 30 ], Bandpass filters were reported in 10 studies (62.5%) with variations between 0–1,000 Hz [ 6 , 17 , 19 , 21 , 22 , 24 – 27 , 31 ]. Only one study (6.25%) reported high-pass and low-pass filters for EMG signal processing details [ 26 ].…”

“…Gain was mentioned in three studies (18.75%) with variations between 20–1,000 times [ 6 , 26 , 27 ]. EMG data acquisition recording reported by twelve studies (75%) varied from 60 through 1.200 seconds [ 17 , 19 – 22 , 24 – 27 , 29 – 31 ] Table 2 .…”

“…Regarding the sEMG signal units, five papers (31.25%) [ 6 , 17 , 18 , 20 , 22 ] presented them in microvolts (μV), four studies (25%) [ 21 , 26 , 27 , 31 ] in percentages, and eight studies (50%) did not inform any unit [ 19 , 23 – 25 , 28 – 31 ]. The obtained variables were presented as simple mean RMS/EMG signal usually rectified or normalized [ 6 , 17 – 20 , 22 – 24 , 26 , 27 , 29 ] or integrated RMS/EMG signals—the difference between the maximum amplitude of RMS signal and its baseline (EMG MAX ), area under the EMG signal curve (EMG AUC ), peak of muscle activity during inspiration (EMG PEAK ), and end of muscle activity per breath (EMG AUC/min ) [ 19 , 21 , 28 , 30 , 31 ] Table 2 .…”

“…According to the objectives of the included studies, the applicability of sEMG used in mechanically ventilated patients can be summarized to the following categories, description muscles activation in different settings [ 17 , 21 – 23 , 28 , 31 ], testing of reliability and correlation to other respiratory muscles assessment techniques [ 6 , 18 , 20 , 24 – 27 ] and assessment of therapy response [ 19 , 29 , 30 ]. These studies have found that sEMG was feasible and resourceful tool for prognosis purposes [ 17 , 22 ] treatment guidance [ 19 , 26 , 27 , 29 – 31 ], reliable monitoring under stable conditions [ 20 , 23 , 28 ] and as surrogate measure [ 6 , 18 , 21 , 24 , 25 ] Table 3 .…”

“…The mechanically ventilated patients’ scenarios for sEMG assessment employment were either in the elective or emergency invasive procedures [ 18 , 20 , 23 , 25 , 26 ] or in acute health conditions [ 6 , 17 , 19 , 21 , 22 , 24 , 27 – 30 ] Table 3 .…”