Dissertation submitted to the Faculty of Health Sciences, University of Witwatersrand in fulfillment of the Master of Science in Medicine in the School of Physiology / Introduction: The changing socio-economic landscape in Africa has brought with it unique health challenges previously uncommon in people of African ancestry. Noncommunicable diseases such as coronary artery disease and stroke have emerged as pressing public health concern highlighting the need to find more on-target diagnostic tools as well as therapeutic interventions. Although ambulatory blood pressure (AMBP) has in many studies conducted in the western world proved to be an independent predictor of carotid intima-media thickness (C-IMT), such results cannot outright be imputed to people of African ancestry living in Africa. That is because people of African ancestry living in Africa are not only of a different ethnicity but are still in the early phases of an epidemiological transition while people in the western countries who are mostly Caucasians, are believed to be in the middle to late phases of an epidemiological transition. Methods: The relationship between the intima-media thickness of the common carotid artery (SonoCalcTM IMT version 3.4) and AMBP (Space labs model 90207) was determined in 320 randomly selected participants of African descent living in an urban developing community in South Africa. Relationships were determined after adjustment for (clinic blood pressure) BPc, age, gender, alcohol and tobacco use, the presence or absence of diabetes mellitus or inappropriate blood glucose control measured by glycated hemoglobin (ghb), antihypertensive therapy and menopausal status. III Results: Mean age for the study population was 43.7± 16.0 years. Both BPc and AMBP parameters were strongly associated with C-IMT (p<0.001) in univariate analysis. In multivariate analysis with BPc. and AMBP entered into separate models and after adjusting for cofounders, BPc. and AMBP maintained significant associations with CIMT. [BPc (partial r=0.0648, p< 0.1612), systolic blood pressure 24 (SBP24) (partial r= 0.236, p< 0.001), systolic blood pressure day (SBPd) (partial r= 0.302, p<0.05), systolic blood pressure night (SBPn) (partial r= 0.0983, p<0.05)]. When adjustments were made with BPc. and SBP24 entered into the same model, BPc lost its association with C-IMT, [SBP24 (partial r=0.236, p<0.001) SBPd (partial r=0.149, p<0.05), SBPn (partial r=0.172, p<0.05)]. Importantly the relationship between SBP24 and C-IMT persisted independent of body mass index (BMI), BPc and age. SBP24 had the highest significant association with C-IMT. Conclusion: SBP24 independently predicts C-IMT even in a model that includes conventional systolic blood pressure (SBPc) leading to the conclusion that AMBP is a more effective tool at diagnosing C-IMT alterations while BPcdoes not have an independent relationship C-IMT.

Thesis--Lund University, 1992. / Added t.p. with thesis statval Includes bibliographical references.

Thesis--Lund University, 1992. / Added t.p. with thesis statval. Includes bibliographical references.

2. A modified model of heart-arterial system was proposed for describing the timing of the second heart sound as a result of the heart-arterial interaction. Simulation results suggest that RS2 bears a significant negative correlation with both SBP and DBP as heart rate, cardiac contractility and peripheral resistance varies. The hypothesis was supported by the experimental data. To our knowledge, it is the first study describing the relation of the timing of S2 to BP by both the model-based study and experimental data. / 3. As a preliminary study, a linear predication model using RS2 with a novel calibration scheme was proposed for BP estimation and it has been evaluated in clinical test on 85 volunteers including 18 hypertensives. The results indicate that the approach has the potential to achieve the accuracy required for medical diagnosis. / Cuffless BP measurement has been proposed as a new concept in recent years to realize the continuous monitoring of BP. This research focuses on the investigation of cuffless BP monitoring technique using heart sound information. Specifically, the thesis proposes a new cuffless technique based on the timing of the second heart sound (S2), which will enable a novel wearable design of BP monitor, for instance, a multifunctional electronic stethoscope. / Finally, based on the findings on both theoretical and experimental studies, a linear prediction model with a novel calibration scheme has been proposed to estimate the BP using 1/RS2. The proposed method was evaluated in a clinical test on 85 volunteers aged 40+/-13 years, including 18 hypertensives. The average of BP measured by simultaneous ausculatory and oscillometric approaches was used as a reference. The results of clinical test shows that the RS2 based approach can estimate SBP and DBP within the 2.1+/-7.4 mmHg and 0.8+/-6.6 mmHg of the reference respectively, indicating the approach has the potential to achieve the accuracy required for medical diagnosis according to AAMI standard (mean error within +/-5mmHg and SD less than 8mmHg) and BHS protocol. / First, a mathematical model has been developed to investigate the effects of aortic BP on the aortic component (A2) in S2 produced by the vibration of the closed aortic valve. The nonlinear elasticity of aortic wall has been introduced to the model, reflecting the nature of aortic wall tissue and extending the model to the applications involving wide BP variations. The results of simulation show that the fundamental frequency and amplitude of A2 increases as aortic systolic blood pressure (SBP) is elevated, which is able to explain the 'accentuated S2' usually heard in the hypertensives. Nevertheless, the possibility of BP measurement using spectral information of externally recorded heart sounds still needs a careful examination because the frequency characteristics tends to be blurred during sound transmission. / Hypertension, known as 'a silent killer', is an important public health challenge, afflicting approximately 1 billion adults around the world. The monitoring of blood pressure (BP) is vitally important in order to identify hypertension and treat it earlier before serious health problems are developed. The conventional BP measurement provides only intermittent BP and causes circulatory interference if the cuff is inflated frequently. There is an urgent need to develop new devices which are fully wearable and unobtrusive for noninvasive and continuous monitoring of arterial BP in daily life. / Second, a modified model of heart-arterial system has been proposed in this thesis for describing the timing of aortic valve closure as a result of heart-arterial interaction. A timing parameter, RS2, was defined as the time delay from the peak of ECG R wave to the onset of S2. The study has investigated the relation between RS2 and aortic BP under varying peripheral resistance, arterial compliance, heart rate, cardiac contractility and preload. Based on the simulation results of parametric analysis, it is hypothesized that RS2 bears a significant negative correlation with both SBP and diastolic blood pressure (DBP) as the peripheral resistance, heart rate or cardiac contractility varies. / Third, in order to verify the findings of the model-based study, three experiments were carried out to explore the relationship between RS2 and BP. The alterations of RS2 in the dynamic-exercise experiments are mainly attributable to the interactive effect of the changes in heart rate, cardiac contractility and peripheral resistance, and the effect of heart rate is dominant. In two dynamic-exercise experiments, the timing parameter, RS2, exhibited a close inverse correlation with SBP (r =0.892 and r =0.845, p&lt;0.05 in both experiments) and a moderate inverse correlation with diastolic blood pressure (DBP) (r = 0.687, p&lt;0.05 and r =0.660, p>0.05). The correlations are comparable to those of PTT-based parameters. However, due to the restricted range of the BP variation, there was no significant correlation observed in long-term rest monitoring experiment. Moreover, the standard deviation (SD) of the errors for SBP and DBP estimated by linear fitting of 1/RS2 is close to that of PTT-based estimation. The results also suggest that the ability of RS2 on BP estimation is as good as that of the PTT based parameters. / To summarize, the original contributions of the thesis are: 1. By the introduction of the nonlinear elasticity of aortic wall, a mathematical model for the vibration of the closed aortic valve was improved and extended to the applications involving wide variations of BP To my knowledge, this represents the first study to look into the effects of aortic BP on the frequency characteristic of S2 from the theoretical point of view. / Zhang Xin-Yu. / "September 2006." / Adviser: Yuan-Ting Zhang. / Source: Dissertation Abstracts International, Volume: 68-09, Section: B, page: 6125. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Thesis (M.S.)--University of Michigan, 2002. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 51-61).

Thesis (M.S.)--University of Michigan, 2002. / Includes bibliographical references (leaves 51-61).

Finally, the effects of external physical factors, such as temperature and contact force, on BP estimation based on m-NHA, were discussed and verified by experiments. Especially, a computational efficient algorithm was developed based on an optical model for motion resistant BP estimation, as well as the estimation of blood oxygen saturation (SaO2). We first developed an optical model with motion effect based on the photon-diffusion analysis, instead of the Beer-Lambert's law, which generally describes the light absorption but fails to account for light scattering in tissue. Based on the optical model, a novel motion resistant algorithm, minimum correlation discreet saturation transform (MCDST), was proposed for the estimation of arterial BP and SaO 2 as well. The novel algorithm is based on the time and time-delayed independence of the "true" signal and motion noise by use of dual PPGs (pulse oximeter). Experimental results indicate that MCDST has a comparable performance in SaO2 estimation and m-NHA calculation, as compared to another clinically verified motion-resistant algorithm---discreet saturation transform (DST). Most importantly, MCDST is much more computationally efficient than DST, because the former only uses simple linear algebra, while the latter uses the adaptive filter. It indicates that MCDST can reduce the required power consumption and circuit complexity of the implementation. It is vitally important for wearable devices, where the small physical size and long battery life are crucial. / First of all, a modified left-ventricle (LV) arterial coupling model was developed by incorporating a nonlinear pressure dependent compliance and two resistances for valve stenosis. A modified LV-arterial coupling model with pressure dependent compliance and taking into account the hypertensives with valve stenosis is quite necessary for proper description of the BP regulation for hypertensives with mitral and/or aortic stenosis, as well as normal people. / Hypertension is the most common cardiovascular disease and is a major public health problem in both developed and developing countries. As hypertension is often asymptomatic, continuous monitoring of blood pressure (BP) for the initiate treatment before the onset of organ damage is of vital importance for home healthcare. However, most of current BP meters, such as sphygmomanometer, are not suitable for the targeted applications because they provide only intermittent blood pressure readings and may cause circulatory interference with the usage of cuff. Moreover, they are not applicable in mobile environment due to the bulky design and the lack of efficient motion resistant algorithms. The objective of this research is to propose a motion resistant method for noninvasive and continuous BP measurement using dual photoplethysmograms (PPG), which could be potentially embedded in the portable or wearable devices for long term BP monitoring. / In summary, the research in this thesis not only covers the fundamental work, such as the modification of heart-arterial system coupling model and the proposal of a novel signal processing method MCDST, but also includes the practical techniques for the estimation of arterial BP as well as oxygen saturation. Expectations for further studies are suggested at the end of this thesis. / Secondly, based on the modified model, a novel parameter, normalized harmonic area (NHA), was proposed for BP estimation by quantifying the frequency distribution in the simulated aortic pressure waveforms. The excellent relationship between NHA and BP was verified by the simulation results. To establish a measurable parameter corresponding to NHA, PPG is investigated because it is widely used for the peripheral circulation monitoring and can be easily obtained at any location on the skin surface. Based on the assumption of quadratic transfer function from aortic pressure to PPG at fingertip, the discreet period transform (DPT) was applied on PPG signal to produce a modified NHA (m-NHA) for BP estimation. For the clinical tests on 85 subjects, the difference between the estimated and the measured blood pressure by m-NHA is 0.97+/-7.9mmHg for systolic blood pressure (SBP) and 0.40+/-4.5mmHg for diastolic blood pressure (DBP), respectively. This result is as good as that (0.73+/-7.6mmHg for SBP, and 0.40+/-4.5mmHg for DBP) from the widely reported pulse transit time (PTT) approach. / Yan Yongsheng. / "November 2005." / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6561. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Thesis (Ph. D.)--University of Florida, 2003. / Title from title page of source document. Includes vita. Includes bibliographical references.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [216]-217).