Bagnall Hare, Hasana (2023) Understanding the neural baroreflex: Pulsatility, baroreflex sensitivity and system identification - experimentation and analysis. PhD thesis, National University of Ireland Maynooth.

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Abstract

Blood pressure is a dynamic measurement that continuously changes based on a variety of physiological needs. Adequate blood pressure is crucial for a variety of reasons, such as organ perfusion, oxygen circulation, and the excretion of harmful toxins. Prolonged periods of blood pressure abnormalities, such as hypotension and hypertension, can lead to an array of adverse events, including myocardial infarction and stroke. Understanding blood pressure dynamics can aid the early diagnosis and slow the development of adverse cardiovascular conditions. This thesis aims to provide additional information about the neural baroreflex, the short term regulator of blood pressure. A protocol to characterise the neural baroreflex from data recorded, where the baroreceptors remain intact, is presented. The method allows for both time- and frequency- domain model identification that accurately represent the neural baroreflex. Mayer waves, or low-frequency oscillations, are observed in blood pressure readings, occurring at approximately 0.1Hz in humans. The origin and prognostic value of these waves are currently being explored. In this thesis, a baroreflex model is extended to include compliance and pulsatility. This model is then used to determine the conditions under which low-frequency oscillations occur, with a focus on the effect of blood pressure pulsatility on their presence. The analysis suggests that as pulsatility decreases, the incidence of Mayer waves increases. This hypothesis is then examined experimentally. The functionality of the baroreflex is evaluated through baroreflex sensitivity estimation. A decrease in baroreflex sensitivity has been proven to be a reliable indicator of adverse cardiovascular events. The current gold standard is the Oxford method, an invasive procedure that cannot be performed in routine clinical settings. Hence, there is a need for a non-invasive alternative. This thesis examines the viability of sequence methods, a popular non-invasive alternative, as a reliable estimation method. This thesis explores a collection of studies which, individually, have their own unique contributions. However, collectively the studies work to increase the understanding of blood pressure regulation, providing insight to aid the development of baroreflex assessment methods and potentially aid the identification of potential sources of baroreflex dysregulation.

Item Type:	Thesis (PhD)
Keywords:	neural baroreflex; Pulsatility; baroreflex sensitivity; system identification; experimentation and analysis;
Academic Unit:	Faculty of Science and Engineering > Electronic Engineering
Item ID:	18625
Depositing User:	IR eTheses
Date Deposited:	10 Jun 2024 11:18
URI:
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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