Related Experiment Video
Updated: Sep 28, 2025
Acquisition and Semi-Automated Analysis of Respiratory Muscle Surface Electromyography
Published on: January 24, 2025
Accessory and Expiratory Muscles Activation During Spontaneous Breathing Trial: A Physiological Study by Surface
Matteo Pozzi1,2, Emanuele Rezoagli1, Alfio Bronco1,2
1Department of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy.
Background:
The physiological and prognostical significance of accessory and expiratory muscles activation is unknown during a spontaneous breathing trial (SBT). We hypothesized that, in patients experiencing weaning failure, accessory and expiratory muscles are activated to cope with an increased respiratory workload.
Purpose:
To describe accessory and expiratory muscle activation non-invasively by surface electromyography (sEMG) during an SBT and to assess differences in electrical activity (EA) of the inspiratory and expiratory muscles in successful vs. failing weaning patients.
Methods:
Intubated patients on mechanical ventilation for more than 48 h undergoing an SBT were enrolled in a medical and surgical third-level ICU of the University Teaching Hospital. Baseline characteristics and physiological variables were recorded in a crossover physiologic prospective clinical study.
Results:
Of 37 critically ill mechanically ventilated patients, 29 (78%) patients successfully passed the SBT. Rapid shallow breathing index (RSBI) was higher in patients who failed SBT compared with the successfully weaned patients at baseline and over time (group-by-time interaction p < 0.001). EA of both the diaphragm (EAdisurf) and of accessory muscles (ACCsurf) was higher in failure patients compared with success (group-by-time interaction p = 0.0174 and p < 0.001, respectively). EA of expiratory muscles (ESPsurf) during SBT increased more in failure than in weaned patients (group-by-time interaction p < 0.0001).
Conclusion:
Non-invasive respiratory muscle monitoring by sEMG was feasible during SBT. Respiratory muscles EA increased during SBT, regardless of SBT outcome, and patients who failed the SBT had a higher increase of all the inspiratory muscles EA compared with the patients who passed the SBT. Recruitment of expiratory muscles-as quantified by sEMG-is associated with SBT failure.
Related Concept Videos
01:21Mechanism of Breathing III: The Accessory Muscles
The respiratory system is a complex network that relies on primary respiratory muscles like the diaphragm, but also involves accessory muscles to enhance lung expansion and airflow during both inhalation and exhalation.
Enhancing Inhalation with Accessory Muscles:
Accessory muscles such as the sternocleidomastoid, scalene, intercostal, and abdominal muscles are crucial when additional respiratory effort is required, such as during deep...
01:30Assessment of Airway, Skin Color, and Use of Accessory Muscles
Introduction
The initial evaluation of a patient's respiratory system...