University of Twente Student Theses


Quantifying diaphragm effort using diaphragm electromyography

Werff, L.C.M. van de (2019) Quantifying diaphragm effort using diaphragm electromyography.

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Abstract:Diaphragm dysfunction develops in the majority of mechanically ventilated critically ill patients on the intensive care unit (ICU), and is associated with adverse outcomes, including prolonged duration of weaning and increased mortality. Insufficient or excessive levels of ventilatory assist may result in diaphragm dysfunction. Monitoring diaphragm effort could help to create a diaphragm-protective ventilation strategy. The golden standard for measuring diaphragm effort, transdiaphragmatic pressure (Pdi), has certain difficulties, e.g. acquiring and interpreting Pdi, that limit the use in clinical care. An alternative technique could be the electrical activity of the diaphragm (EAdi), as it is already demonstrated EAdi strongly correlates with Pdi. EAdi has been used to quantify breathing effort in ICU patients before within a limited range of respiratory muscle effort. Therefore, our goal was to study the correlation between EAdi and Pdi in the entire physiological range of breathing effort in healthy subjects to be able to quantify diaphragm effort using EAdi. Mouth pressure (Pmo), Pdi and EAdi were recorded continuously in fifteen healthy subjects using nasogastric catheters. Different levels of inspiratory threshold loading were applied, ranging from 10% to 80% of maximal Pdi during an occlusion. The Pdi-EAdi relationship was assessed per subject using linear regression on all breaths or the breaths under a cutoff value for Pdi or EAdi. We tried to approximate the slope of the cutoff EAdi regression using Pmo/EAdi during different occlusions. On average, a moderate linear correlation was found between EAdi and Pdi within each subject (r2 of 0.66±0.16). In thirteen subjects, r2 improved significantly when the breaths above 60% of maximal Pdi, cutoff Pdi, were discarded (0.81±0.10, p < 0.05). An EAdi cutoff of ±70% of maximal EAdi resulted in an insignificant increase of r2 (0.68±0.16, p = 0.140). The slopes found by linear regression were very heterogeneous among subjects, ranging from 0.39 to 1.77 cmH2O/µV. No agreement was found between the slope and Pmo/EAdi during occlusions. A significant correlation exists between EAdi and Pdi, but the relationship does not seem to be linear as a Pdi cutoff value improves the fit significantly. The generation of Pdi may be influenced by other factors, such as the force-length and force-velocity relationships of the diaphragm. Further analysis of the data might improve the correlation between EAdi and Pdi per subject when fitting a nonlinear curve using multiple variables that reflect the force-length and the force-velocity relationship.
Item Type:Essay (Master)
Amsterdam UMC, location VUmc, Amsterdam, Netherlands
Faculty:TNW: Science and Technology
Subject:44 medicine
Programme:Technical Medicine MSc (60033)
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