acquisition-semi-automated-analysis-respiratory-muscle-surface

Acquisition and Semi-Automated Analysis of Respiratory Muscle Surface Electromyography

Evaluating respiratory drive presents challenges due to the obtrusiveness and impracticality of current methods like functional magnetic resonance imaging ...

Unity Health Toronto

University of Toronto

Reverse triggering dyssynchrony is a frequent phenomenon recently recognized in sedated critically ill patients under controlled ventilation. It occurs in at least 30-55% of these patients and often occurs in the transition from fully passive to assisted mechanical ventilation. During reverse triggering, patient inspiratory efforts start after the passive insufflation by mechanical breaths. The most often referred mechanism is the entrainment of the patient's intrinsic respiratory rhythm from the brainstem respiratory centers to periodic mechanical insufflations from the ventilator. However, reverse triggering might also occur because of local reflexes without involving the respiratory rhythm generator in the brainstem. Reverse triggering is observed during the acute phase of the disease, when patients may be susceptible to potential deleterious consequences of injurious or asynchronous efforts. Diagnosing reverse triggering might be challenging and can easily be missed. Inspection of ventilator waveforms or more sophisticated methods, such as the electrical activity of the diaphragm or esophageal pressure, can be used for diagnosis. The occurrence of reverse triggering might have clinical consequences. On the basis of physiological data, reverse triggering might be beneficial or injurious for the diaphragm and the lung, depending on the magnitude of the inspiratory effort. Reverse triggering can cause breath-stacking and loss of protective lung ventilation when triggering a second cycle. Little is known about how to manage patients with reverse triggering; however, available evidence can guide management on the basis of physiological principles.

Reverse Triggering during Controlled Ventilation: From Physiology to Clinical Management.

Unilateral diaphragm dysfunction (UDD) is an underdiagnosed cause of dyspnoea. Inspiratory muscle training (IMT) is the only conservative treatment for UDD, but the mechanisms of improvement are unknown. We characterised the effects of IMT on dyspnoea, exercise tolerance and respiratory muscle function in people with UDD.

Effects of inspiratory muscle training on exertional breathlessness in patients with unilateral diaphragm dysfunction: a randomised trial.

Aerosol barrier enclosure systems have been designed to prevent airborne contamination, but their safety has been questioned. A vacuum tent was designed with active continuous suctioning to minimize risks of aerosol dispersion. We tested its efficacy, risk of rebreathing, and usability on a bench, in healthy volunteers, and in an ergonomic clinical assessment study.

An Individual Barrier Enclosure Actively Removing Aerosols for Airborne Isolation: A Vacuum Tent.

Potentially Injurious Patient-Ventilator Interactions, Challenges Beyond Excess Stress and Strain.

Prior studies of muscle blood flow and muscle-specific oxygen consumption have required invasive injection of dye and magnetic resonance imaging, respectively. Such measures have limited utility for continuous monitoring of the respiratory muscles. Frequency-domain near-infrared spectroscopy and diffuse correlation spectroscopy (FD-NIRS & DCS) can provide continuous surrogate measures of blood flow index (BF) and metabolic rate of oxygen consumption (MRO). This study aimed to validate sternocleidomastoid FD-NIRS & DCS outcomes against electromyography (EMG) and mouth pressure (Pm) during incremental inspiratory threshold loading (ITL). Six female and six male healthy adults (means ± SD; 30 ± 7 yr, maximum inspiratory pressure 118 ± 61 cmHO) performed incremental ITL starting at low loads (8 ± 2 cmHO) followed by 50-g increments every 2 min until task failure. FD-NIRS & DCS continuously measured sternocleidomastoid oxygenated and deoxygenated hemoglobin + myoglobin (oxy/deoxy[Hb + Mb]), tissue saturation of oxygen (StO), BF, and MRO. Ventilatory parameters including inspiratory Pm were also evaluated. Pm increased during incremental ITL ( < 0.05), reaching -47[-74 to -34] cmHO (median [IQR: 25%-75%]) at task failure. Ventilatory parameters were constant throughout ITL (all  > 0.05). Sternocleidomastoid BF and MRO increased from the start of the ITL (both  < 0.05). Deoxy[Hb + Mb] increased close to task failure, concomitantly with a constant increase in MRO, and decreased StO. Sternocleidomastoid deoxy[Hb + Mb], BF, StO, and MRO obtained during ITL via FD-NIRS & DCS correlated with sternocleidomastoid EMG (all  < 0.05). In healthy adults, FD-NIRS & DCS can provide continuous surrogate measures of respiratory BF and MRO. Increasing sternocleidomastoid oxygen consumption near task failure was associated with increased oxygen extraction and reduced tissue saturation. This study introduces a novel approach, frequency-domain near-infrared spectroscopy and diffuse correlation spectroscopy (FD-NIRS & DCS), for noninvasive continuous monitoring of respiratory muscle blood flow and metabolic rate of oxygen consumption. Unlike prior methods involving invasive dye injection and magnetic resonance imaging, FD-NIRS & DCS offers the advantage of continuous measurement without the need for invasive procedures. It holds promise for advancing muscle physiology understanding and opens avenues for real-time monitoring of respiratory muscles.

Continuous measurements of respiratory muscle blood flow and oxygen consumption using noninvasive frequency-domain near-infrared spectroscopy and diffuse correlation spectroscopy.

During mechanical ventilation, post-insufflation diaphragm contractions (PIDCs) are non-physiologic and could be injurious. PIDCs could be frequent during reverse-triggering, where diaphragm contractions follow the ventilator rhythm. Whether PIDCs happens with different modes of assisted ventilation is unknown. In mechanically ventilated patients with hypoxemic respiratory failure, we aimed to examine whether PIDCs are associated with ventilator settings, patients' characteristics or both.

Post-insufflation diaphragm contractions in patients receiving various modes of mechanical ventilation.

Past observational studies have reported the association between patient-ventilator asynchronies and poor clinical outcomes, namely longer duration of mechanical ventilation and higher mortality. But causality has remained undetermined. During the era of lung and diaphragm protective ventilation, should we revolutionize our clinical practice to detect and treat dyssynchrony?

Does patient-ventilator asynchrony really matter?

Assessing and treating respiratory muscle dysfunction is crucial for patients with both acute and chronic respiratory failure. Respiratory muscle dysfunction can contribute to the onset of respiratory failure and may also worsen due to interventions aimed at treatment. Evaluating respiratory muscle function is particularly valuable for diagnosing, phenotyping and assessing treatment efficacy in these patients. This review outlines established methods, such as measuring respiratory pressures, and explores novel techniques, including respiratory muscle neurophysiology assessments using electromyography and imaging with ultrasound.Additionally, we review various treatment strategies designed to support and alleviate the burden on overworked respiratory muscles or to enhance their capacity through training interventions. These strategies range from invasive and noninvasive mechanical ventilation approaches to specialised respiratory muscle training programmes. By summarising both established techniques and recent methodological advancements, this review aims to provide a comprehensive overview of the tools available in clinical practice for evaluating and treating respiratory muscle dysfunction. Our goal is to present a clear understanding of the current capabilities and limitations of these diagnostic and therapeutic approaches. Integrating advanced diagnostic methods and innovative treatment strategies should help improve patient management and outcomes. This comprehensive review serves as a resource for clinicians, equipping them with the necessary knowledge to effectively diagnose and treat respiratory muscle dysfunction in both acute and chronic respiratory failure scenarios.

Respiratory muscle dysfunction in acute and chronic respiratory failure: how to diagnose and how to treat?

Predicting complete liberation from mechanical ventilation (MV) is still challenging. Electrical impedance tomography (EIT) offers a non-invasive measure of regional ventilation distribution and could bring additional information.

Ventilation distribution during spontaneous breathing trials predicts liberation from mechanical ventilation: the VISION study.

In patients with acute hypoxemic respiratory failure (AHRF) under mechanical ventilation, the change in pressure slope during a low-flow insufflation indicates a global airway opening pressure (AOP) needed to reopen closed airways and may be used for titration of positive end-expiratory pressure.

Article	Year
Reverse Triggering during Controlled Ventilation: From Physiology to Clinical Management. American journal of respiratory and critical care medicine\| PubMed ID: 36470240	2023
Effects of inspiratory muscle training on exertional breathlessness in patients with unilateral diaphragm dysfunction: a randomised trial. ERJ open research\| PubMed ID: 37868146	2023
An Individual Barrier Enclosure Actively Removing Aerosols for Airborne Isolation: A Vacuum Tent. Respiratory care\| PubMed ID: 38538026	2024
Potentially Injurious Patient-Ventilator Interactions, Challenges Beyond Excess Stress and Strain. Critical care medicine\| PubMed ID: 38619344	2024
Continuous measurements of respiratory muscle blood flow and oxygen consumption using noninvasive frequency-domain near-infrared spectroscopy and diffuse correlation spectroscopy. Journal of applied physiology (Bethesda, Md. : 1985)\| PubMed ID: 38867669	2024
Post-insufflation diaphragm contractions in patients receiving various modes of mechanical ventilation. Critical care (London, England)\| PubMed ID: 39294653	2024
Does patient-ventilator asynchrony really matter? Current opinion in critical care\| PubMed ID: 39445589	2025
Respiratory muscle dysfunction in acute and chronic respiratory failure: how to diagnose and how to treat? European respiratory review : an official journal of the European Respiratory Society\| PubMed ID: 39631928	2024
Ventilation distribution during spontaneous breathing trials predicts liberation from mechanical ventilation: the VISION study. Critical care (London, England)\| PubMed ID: 39773268	2025
Distribution of airway pressure opening in the lungs measured with electrical impedance tomography (POET): a prospective physiological study. Critical care (London, England)\| PubMed ID: 39819779	2025

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