Neural Respiratory Drive and Respiratory Muscle Function During CO2 Stimulation
Date
2022-06-15
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Abstract
Background. The use of EMG of the respiratory muscles as a surrogate of the central neural respiratory drive is gaining clinical popularity. Currently, the clinical EMG recording of the crural diaphragm by an esophageal electrodes probe (EAdi) is promoted as a “gold standard”. Additionally, other inspiratory muscles have been investigated as a less invasive alternative, especially the surface EMG of parasternal intercostal. Now there is major clinical interest focusing on the EMG of abdominal muscle as indicator of diaphragm weakness. However, all these clinical applications rely on physiological and technical assumptions that are not fully elucidated. Theme. The focus of this thesis is to address the following questions: 1) do crural and costal diaphragm share an identical neural-mechanical profile during inspiration? 2) does crural and costal diaphragm activity extend into, and contribute identically, during expiration? 3) does the parasternal intercostal share a similar neural activation with the diaphragm during inspiration? 4) is the current clinical technique, recording the surface EMG of parasternal intercostal? 5) is the expiratory phase a passive physiologic process, so that the activation of the abdominal muscles is a pathological indicator? Projects. This thesis is organized as a series of related projects, corresponding to individual chapters addressing each physiological question. The successful execution of this thesis work relied upon a model of a large, normal, intact mammals group, with intact airways, awake without anesthetic, at rest during spontaneous breathing. And, we did further measurements during progressive chemical stimulation by hypercapnia. Summary. We found that the crural and costal diaphragm each exhibit a distinct neural mechanical profile during inspiration, and the differentiation in their operational role extends into the early phase of expiration. Therefore, the clinical assumption that the crural diaphragm is representative of the whole diaphragm is not supported. Our results support the use of parasternal intercostal as a surrogate of neural respiratory drive. However, we confirmed that the current technique based on surface EMG is not reliable due to intrinsic physiologic limitations. Finally, our findings reinforce the concept that expiration is not a passive process but actively contributes to inspiration.
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RESPIRATORY MUSCLES, HYPERCAPNIA, EMG, SONOMICROMETRY, NEURAL RESPIRATORY DRIVE, DIAPHRAGM, PARASTERNAL INTERCOSTAL, TRANSVERSUS ABDOMINIS, COSTAL DIAPHRAGM, CRURAL DIAPHRAGM
Citation
Tagliabue, G. (2022). Neural Respiratory Drive and Respiratory Muscle Function During CO2 Stimulation (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.