The reproducibility of oscillometric assessment of central haemodynamics and the efficacy of acute and chronic physical activity interventions in an older population and after stroke

Abstract

Non-invasive measures of central blood pressure through pulse wave analysis may be key to future management of cardiovascular disease risk in currently healthy and clinical populations. One device that can non-invasively estimate central blood pressure is the SphygmoCor XCEL. The validity of this device has been demonstrated compared to invasive measures, but the reliability has previously only been demonstrated in younger, non-clinical populations. In day-to-day life, blood pressure measures are taken in a variety of postures and fasting states depending on user preference, clinician preference, time of day and environment. The acute effects of posture and fasting state on these central measures have not been widely investigated. Therefore the purpose of the first and second studies in this thesis was to focus on a) reporting the between-day reliability of the SphygmoCor XCEL in an older, non-clinical sample (age >50y) and a hyper-acute stroke sample, and b) report the individual and combined effects of posture and fasting state on a variety of peripheral and central blood pressure measures in these populations. The SphygmoCor XCEL was demonstrated to have generally excellent between-day reliability (using an intra-class correlation coefficient > 0.75 as the criterion excellence value) in fasted and non-fasted, and seated and supine states in both populations. Posture had a significant effect on diastolic pressures in both populations (p < .05), whereas fasting state had a significant effect on the majority of peripheral and central systolic and diastolic pressures, as well as measures of arterial stiffness (Augmentation Index, Augmentation Index at a heart rate of 75 b·min-1; p < .05). These studies demonstrate that the SphygmoCor XCEL is a reliable tool for use in population demographics where its findings are particularly pertinent (those over the age of 50 or those suffering from stroke), and that posture and fasting state should both be taken into consideration when interpreting peripheral and central blood pressure measures. Increased levels of sedentary time and reduced physical activity are common after stroke, potentially due to the perception that sedentary time is a normal and an important way of relaxing after stroke. The third study in this thesis investigated the effects of sedentary time on peripheral and central blood pressure measures and measures of arterial stiffness, thereby investigating whether low level physical activity (intermittent heel raises) could prevent this damaging process. Three hours of sedentary time was sufficient to cause significant increases in peripheral and central blood pressure (p < .05). Intermittent heel raises significantly mitigated this damage but did not prevent it (increases of 10.7 mmHg peripheral systolic blood pressure and 9.6 mmHg central blood pressure in the three-hour sedentary condition compared with increases of 5.2 mmHg and 5.6 mmHg respectively in the three-hour heel raise condition). Due to the significant effects observed in study 3, a pilot ‘heel raise intervention’ trial was undertaken (the fourth study of this thesis). Participants completed a heel raise protocol on six days per week for ten weeks to determine whether the acute effects demonstrated in the third study could be replicated chronically. This study found no significant improvements in any body composition, central and peripheral haemodynamic, arterial stiffness or cognitive variables (p > .05). This thesis has demonstrated the reliability of the SphygmoCor XCEL in new populations and demonstrated the effect of posture and fasting state on peripheral and central measures. It has also reported that three hours of sedentary time is sufficient to cause significant increases in BP but this can be mitigated through lower limb physical activity. Although this lower limb physical activity causes acute improvements in blood pressure, this does not translate into chronic improvements over the course of a ten-week exercise programme, although these findings must be interpreted with caution due to the small sample size.

Date of Award	17 Jul 2019
Original language	English
Awarding Institution	University of Winchester
Supervisor	James Faulkner (Supervisor), Simon Jobson (Supervisor) & Danielle Lambrick (Supervisor)