University of Twente Student Theses


Respiratory muscle physiology during assisted mechanical ventilation from a technological view

Holleboom, Minke (2021) Respiratory muscle physiology during assisted mechanical ventilation from a technological view.

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Abstract:Introduction: Mechanical ventilation is often needed in critically ill patients, to improve gas exchange and reduce the work of breathing. While mechanical ventilation is life-saving, it can also be harmful for the lung tissue as well as the diaphragm. The optimal strategy for maintaining breathing effort in mechanical ventilation is a double-edged sword, aiming to prevent the development of atrophy due to over-assistance as well as muscle injury due to under-assistance. Research mainly has focused on the diaphragm as main inspiratory muscle, but the expiratory muscles and the expiratory phase of breathing are often neglected. The coordination between inspiratory and expiratory muscles is complex, and the prevalence of respiratory muscle activity during pressure support ventilation is largely unknown. Methods: In a observational clinical study, patients are measured during a spontaneous breathing trial, with the aim to assess functional and timing coordination of the respiratory muscles, focused on the expiratory phase of breathing. Functional coordination parameters included pressure swings, work of breathing and pressure-time-product parameters. Timing coordination parameters included phase angle analysis of starting and end points of pressure (Pes, Pga, Pdi) and EMG signals. Using data of 15 subjects from a clinical trial, the prevalence and level of commonly known and newly defined pressure-derived (expiration) parameters are analysed. In the reliability study, the intra class correlation of echogenicity measurements of the diaphragm is assessed. Results: The observational clinical study shows preliminary results of two subjects, of whom one subject failed the SBT and the second subject succeeded. The failing subject did not show significant expiration effort, while the successful subject did. Analysis of functional as well as timing coordination analysis, per interval of the SBT, showed to be feasible. The additional data analysis showed significant expiration effort (∆Pga,exp >2 cmH2O and PTPga,exp >40 cmH2O) in one third of the analysed patients. The reliability of echogenicity measurements was found to have good agreements (ICC values from 0.75 for interrater to 0.88 for intrarater). Discussion: Further inclusion of subjects should provide clarification in whether the notable results in the observational clinical study are exceptions. The newly defined expiration parameters give additional insight in the respiratory mechanics, but their purpose should be investigated in future research. Future studies should focus on technical improvements such as filtering of pressure signals and automated ROI selection. Several clinical questions remain. What causes expiration effort in which patient population? Is expiratory muscle recruitment beneficial for these patients?
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:44 medicine, 50 technical science in general
Programme:Technical Medicine MSc (60033)
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