A dissertation submitted to the Faculty of Engineering and the Built Environment, University of Witwatersrand in fulfilment of the requirements for the degree of Master of Science in Engineering. 2017 / The baroreceptor is a stretch receptor which detects changes in pressure in arterial blood vessels. Baroreceptor nerves inform the brainstem of changes in blood pressure, which then influences sympathetic and parasympathetic nervous activity to counteract that change. Due to the relationship between essential hypertension, sympathetic nervous activity and the baroreflex, there is some debate in the literature about whether the baroreflex can act as a long-term controller of blood pressure. This debate has increased in recent years, due to the high prevalence of essential hypertension in all societies and the introduction of new technologies to counteract drug-resistance hypertension. The baroreflex has become a source of debate due to the complex physiological feedback control that regulates blood pressure and due to new stimulating electrical devices, which have shown promising results in reducing drug-resistant essential hypertension. system. This is done through a literature survey extending through experimental and modelling research, where selected mathematical models of the baroreceptor are then analysed and simulated to find the best performing model, so that they may be simulated for an extended frequency response than what would be experimentally possible. The purpose of this investigation is to determine, through simulation, what the sensor static and dynamic characteristics are. Through this characterisation of the sensor behaviour of the baroreceptor in the baroreflex control loop, it is then possible to infer whether the baroreflex can act as a long-term controller of blood pressure. An overview of experimental and analytical investigations on the baroreceptor over the last 70 years is summarised. This overview includes mathematical models, which predict experimental results. A subset of four models from Srinivasen et al., Bugenhagen et al., Beard et al. and Mahdi et al. are selected. These models are implemented in MATLAB and Simulink. The parameters and experimental conditions are integrated into the Simulink models, and the simulated results are compared to the reported experimental data. In this way, each mathematical model is evaluated using secondary data for its ability to simulate the expected behaviour. Thereafter, all simulated models are compared under the same input conditions (a 0-230 mmHg step input over 12 s). These results are used to select the best performing models, based on how well they were parameterised and validated for experimental tests. The best performing models are those of Beard et al. and Bugenhagen et al. They are tested for a wide range of artificial inputs at different frequencies, with sinusoidal inputs which have periods that range from 0.1 s to 10 days and have a 100 mmHg operating point with a 1 mmHg peak amplitude. All modelling techniques studied show that the baroreceptor firing response resets due to the rate of change in strain in the visco-elastic arterial wall. Both tested model frequency responses, although parameterised for different species and for different major vessels, show high sensitivity to inputs in range from 1 s to 1 min 36 s (0.01 Hz 1Hz), and very low sensitivity for changes that are longer than 16 min 36s (0.001 Hz). This extrapolated simulation suggests a zero gain near DC. The simulated frequency response of the best performing baroreceptor models, which were validated against short-term experimental data, indicate that the baroreceptor is only able to sense changes that happen in less than 1 min 16s. The critical analysis of all the simulated baroreceptor models show that this characteristic of the baroreceptor is caused by the visco-elastic layers of the arterial wall, and is likely in all baroreceptors regardless of type or species. It also indicates that under electrical stimulation of the baroreceptor, the input signal from the electrical device bypasses the baroreceptor nerve ending (which is embedded in the arterial wall) and that the electrical signal of the baroreceptor is bypassed by the new stimulated electrical signal of the device. Furthermore, if the sensor can only detect short-term changes, then it is unlikely that the baroreceptor can inform the brainstem on longterm changes to mean arterial blood pressure. Therefore, based on the models examined in this study, this suggests that the baroreceptor is unlikely to be involved in long-term blood pressure control. This analysis of the best performing model is presented to show the limitations of the baroreflex in long term control of blood pressure. It serves as a simulated experiment to rationalise the contentious debate around the role of the baroreflex in long term blood pressure control, and to allow for future improvements that can be made on the baroreceptor model to allow for more extended modelling on sor characteristics. An improvement that could be applied to the best performing baroreceptor models, implemented in this study, is to examine the effects of ageing and inter-species variability on carotid sinus dimensions and visco-elastic wall properties. / CK2018

A medida da pressão arterial é um procedimento fundamental para o diagnóstico e controle da hipertensão arterial. O objetivo do presente estudo foi identificar como é realizado o procedimento de medida indireta e registro da pressão arterial por profissionais de enfermagem. Trata-se de estudo quantitativo, observacional, de delineamento transversal. A amostra foi composta por 80 servidores lotados em cinco Unidades de Saúde do município de Londrina-Paraná, sendo 25 (31,3 %) enfermeiros, 24 (30%) técnicos de enfermagem e 31 (38,8 %) auxiliares de enfermagem. Para avaliar como os participantes realizam a medida indireta da pressão arterial, utilizamos como referência um instrumento formulado a partir das etapas para a medida da pressão descritas nas VI Diretrizes Brasileiras de Hipertensão. O registro do procedimento foi avaliado a partir de instrumento construído com base nas recomendações para registros de enfermagem do Conselho Regional de Enfermagem de São Paulo. Também identificamos a qualidade dos dispositivos utilizados para a medida da pressão arterial. Os resultados mostraram altos índices de \"não realização\" (93,8% a 100%) das etapas referentes ao preparo do paciente para a medida da pressão. As etapas relacionadas diretamente à obtenção do valor pressórico apresentaram índices de 3,8% a 100% na categoria \"incorreta\", sendo os piores resultados relacionados a inflação e deflação da bolsa de borracha. As etapas: \"obter a circunferência braquial no ponto médio do braço\" e \"selecionar manguito de tamanho adequado à circunferência do braço\" não foram realizadas por 100% e 96,3% dos participantes, respectivamente. Na sua totalidade, os profissionais se limitaram a registrar o valor da pressão arterial e, na maioria das anotações, não houve identificação do participante pelo registro profissional (96, 3%) ou pela assinatura (93,8%) e não há referência ao horário da anotação (70,9%). Em relação aos equipamentos, a calibração não é aferida na rotina dos serviços e não há disponibilidade de manguitos de tamanhos variados. Esses achados permitem concluir que há importantes lacunas relacionadas à prática adotada pela equipe de enfermagem para a medida da pressão arterial, indicando a necessidade de implementação de medidas educativas / Blood pressure measurement is an essential procedure to the diagnosis and control of hypertension. The aim of this study was to identify how the indirect measurement and recording of blood pressure was performed by members of the nursing profession. This is a quantitative, observational and cross-sectional study with a sample comprised of 80 professional workers from five different Health Centers in the municipality of Londrina, Paraná. Among these professional workers, twenty-five (31,1%) were nurses, 24 (30%) were nurse technicians and 31 (38,8%) were auxiliary nurses. In order to assess the way the participants performed the indirect measurement of blood pressure, a tool which is based on the steps proposed by the 6th Brazilian Guidelines for Hypertension for BP readings was used. In order to assess the recordings made by the workers, it was used a tool which is based on the recommendations put forward by the São Paulo Regional Board of Nursing for recordings in this field. The quality of the devices used for BP measurement was also inspected. The results of this study have showed that a large number of participants (93,8% to 100%) failed to follow the steps concerning the preparation of the patient for the reading. For the steps that were directly related to the measurement of the blood pressure itself, the percentages obtained for the \"incorrect\" category ranged from 3,8% to 100%. The worst results achieved in this case were those related to the inflation and deflation of the rubber bladder. Around 100% of the participants did not contemplate the step \"Obtaining the upper arm circumference at a middle point\" and 96,3% of them did not follow the step \"Choosing the appropriate cuff size for the upper arm circumference\". Most workers only recorded the blood pressure readings, therefore leaving out their professional registers (96,3), their signatures (93,8%) and the time the reading was done (70,9%). The calibration of the devices used in this procedure is not done on regular basis and there is only one size of cuff available. The findings of this study show that there are several important gaps that need to be filled in regard to the procedure adopted by the nursing staff when measuring blood pressure. They also indicate the need to implement professional training

Aortic baroreflex (ABR) control of blood pressure was examined in 7 untrained (UT) and 8 endurance exercise trained (EET) young men. ABR control of blood pressure was determined during a steady state phenylephrine infusion to increase mean arterial pressure 10-15 mmHg, combined with positive neck pressure to counteract the increased carotid sinus transmural pressure, and low levels of lower body negative pressure to counteract the increased central venous pressure. Functioning alone, the ABR was functionally adequate to control blood pressure. However, ABR control of HR was significantly diminished in the EET subjects due solely to the decrease in the ABR sensitivity. The persistent strain from an increased stroke volume resulting from endurance exercise training could be the responsible mechanism.

壓力感受器在調節血壓的壓力感受性反射中的作用已是眾所周知。兩個動脈壓力感受器，分別為主動脈壓力感受器和頸動脈壓力感受器。它們作為重要的感應器以檢測主要動脈血壓，並和孤束核溝通，從而調節血壓。然而，壓力感受器的機械力敏感元件的分子身份仍是奧秘。因為機械敏感的陽離子通道受機械力刺激時會增加的神經元活動, 所以機械敏感的陽離子通道是合適的候選人。 / 在本研究中，通過使用膜片鉗和動作電位的測量，瞬时受体电位通道C5(TRPC5)被確定在主動脈壓力感受器的機械傳感器中。透過在壓力感受器神經元的鈣測量實驗，證實TRPC5參與由拉伸引起的鈣離子([Ca²⁺]i)上升。TRPC5基因敲除小鼠出現壓力感受器功能受損, 表明了TRPC5在血壓控制的重要性。 / 比較主動脈壓力感受器或頸動脈壓力感受器的不同敏感度現時存有不少爭論。在本研究中，我發現主動脈壓力感受器比頸動脈壓力感受器對於壓力變化更加敏感。此外，我還發現了主動脈壓力感受器神經元比頸動脈壓力感受器神經元有一個相對較高的瞬时受体电位通道V4(TRPV4)表達。鈣測量研究表明TRPV4通道在主動脈壓力感受器神經元的靈敏度可能發揮著重要作用。 / Baroreceptors have been well known for its role in the baroreflex regulation of blood pressure. Two arterial baroreceptors, aortic and carotid baroreceptors, serve as the important sensors to detect blood pressure in main arteries, and they communicate with the solitary nucleus tract for blood pressure regulation. However, the molecular identity of the mechano-sensitive components in the baroreceptors is still mysteries. Mechano-sensitive cation channels are the fascinating candidates as they increase neuronal activities when stimulated by stretch. In the present study, with the use of patch clamp and action potential measurement, TRPC5 channels were identified to be the mechanical sensor in the aortic baroreceptor. Calcium measurement studies demonstrated that TRPC5 was involved in the stretch-induced [Ca2+]i rise in baroreceptor neurons. The importance of TRPC5 in blood pressure control was also studied in TRPC5 knockout mice, which displayed an impaired baroreceptor function. / There have been controversies as to whether aortic baroreceptors or carotid baroreceptors are more sensitive to the change in blood pressure. In the present study, aortic baroreceptor was found to be more sensitive to the pressure change than the carotid baroreceptor. Furthermore, I also found a relative higher expression of TRPV4, a mechanosensitive channel, in the aortic baroreceptor neurons than in the carotid baroreceptor neurons. Moreover, calcium measurement studies showed that TRPV4 channels should play an important role in governing the differential pressure sensitivity in these two types of baroreceptor neurons. / Taken together, the present study provided novel information on the role of TRPC5 and TRPV4 in baroreceptor mechanosensing. In future, it will be of interest to explore whether TRPC5 and/or TRPV4 dysfunction could contribute to human diseases that are related to blood pressure control. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Lau, On Chai Eva. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 133-152). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / Declaration --- p.i / Abstract of the thesis entitled --- p.ii / Acknowledgement --- p.vii / Abbreviation --- p.ix / Table of content --- p.xii / List of figures --- p.xv / List of table --- p.xvii / Chapter Chapter 1: --- Introduction --- p.1 / Chapter 1.1 --- Baroreceptors --- p.1 / Chapter 1.1.2 --- Arterial baroreceptors --- p.2 / Chapter 1.1.2.1 --- Functions of arterial baroreceptors --- p.4 / Chapter 1.1.2.2 --- Sensitivity of the arterial baroreceptors --- p.6 / Chapter 1.1.3 --- Other baroreceptors --- p.8 / Chapter 1.1.4 --- The molecular identity of the mechanosensors in baroreceptor neurons --- p.9 / Chapter 1.2 --- Transient receptor potential ion channels (TRP channels) --- p.10 / Chapter 1.2.1 --- TRP channels superfamily --- p.10 / Chapter 1.2.2 --- Multimerization of TRP channels --- p.12 / Chapter 1.2.3 --- Physiological functions --- p.14 / Chapter 1.2.4 --- Mechanosensitive TRP channels --- p.16 / Chapter 1.2.5 --- Canonical transient receptor potential 5 (TRPC5) channels --- p.17 / Chapter 1.2.6 --- Vanilloid transient receptor potential 4 (TRPV4) channels Figures --- p.20 / Chapter Chapter 2: --- Objectives --- p.34 / Chapter Chapter 3: --- Materials and Methods --- p.35 / Chapter 3.1 --- Materials --- p.35 / Chapter 3.1.1 --- Chemicals and reagents --- p.35 / Chapter 3.1.2 --- Solutions --- p.36 / Chapter 3.1.2.1 --- Solutions for calcium imaging --- p.36 / Chapter 3.1.2.2 --- Solutions for electrophysiology study --- p.38 / Chapter 3.1.2.3 --- Solutions for agarose gel electrophoresis --- p.41 / Chapter 3.1.3 --- Primers for RT-PCR --- p.42 / Chapter 3.1.4 --- Animals --- p.43 / Chapter 3.2 --- Methods --- p.43 / Chapter 3.2.1 --- Total RNA isolation and RT-PCR --- p.43 / Chapter 3.2.2 --- Immunohistochemistry --- p.44 / Chapter 3.2.3 --- Neuron labeling by DiI --- p.45 / Chapter 3.2.4 --- Neuron culture --- p.46 / Chapter 3.2.5 --- [Ca²⁺]i measurement --- p.47 / Chapter 3.2.6 --- Electrophysiology --- p.48 / Chapter 3.2.7 --- Evaluation of baroreflex response --- p.49 / Chapter 3.2.8 --- Telemetric measurement of blood pressure --- p.50 / Chapter 3.2.9 --- Statistical analysis --- p.51 / Figures --- p.52 / Chapter Chapter 4: --- Functional role of TRPC5 channels in aortic baroreceptor --- p.56 / Chapter 4.1 --- Introduction --- p.56 / Chapter 4.2 --- Materials and Methods --- p.59 / Chapter 4.2.1 --- Animals --- p.59 / Chapter 4.2.2 --- Immunohistochemistry --- p.59 / Chapter 4.2.3 --- Neuron labeling by DiI --- p.61 / Chapter 4.2.4 --- Neuron culture --- p.62 / Chapter 4.2.5 --- [Ca²⁺]i measurement --- p.63 / Chapter 4.2.6 --- Electrophysiology --- p.63 / Chapter 4.2.7 --- Evaluation of baroreflex response --- p.64 / Chapter 4.2.8 --- Telemetric measurement of blood pressure --- p.66 / Chapter 4.2.9 --- Statistical analysis --- p.67 / Chapter 4.3 --- Results --- p.67 / Chapter 4.3.1 --- Endogenous expression of TRPC5 channels in aortic baroreceptor neurons --- p.67 / Chapter 4.3.2 --- Characterization on the pressure-sensitive component in aortic baroreceptors --- p.68 / Chapter 4.3.3 --- Involvement of TRPC5 in [Ca²⁺]i response in aortic baroreceptor neurons --- p.69 / Chapter 4.3.4 --- Participation of TRPC5 in pressure-induced action potential firing in cultured aortic baroreceptor neurons --- p.70 / Chapter 4.3.5 --- Role of TRPC5 in baroreceptor sensory nerve activity and baroreflex regulation --- p.71 / Chapter 4.3.6 --- Importance of TRPC5 in baroreceptor function --- p.72 / Chapter 4.4 --- Discussions --- p.74 / Figures --- p.79 / Table --- p.98 / Chapter Chapter --- 5: TRPV4 channels and baroreceptor sensitivity --- p.99 / Chapter 5.1 --- Introduction --- p.99 / Chapter 5.2 --- Materials and Methods --- p.101 / Chapter 5.2.1 --- Animals --- p.101 / Chapter 5.2.2 --- Neuron labeling by DiI --- p.101 / Chapter 5.2.3 --- Neuron culture --- p.102 / Chapter 5.2.4 --- Electrophysiology --- p.103 / Chapter 5.2.5 --- Immunohistochemistry --- p.104 / Chapter 5.2.6 --- [Ca²⁺]i measurement --- p.105 / Chapter 5.2.7 --- Statistical analysis --- p.105 / Chapter 5.3 --- Results --- p.106 / Chapter 5.3.1 --- Properties of the aortic and carotid baroreceptor neurons --- p.106 / Chapter 5.3.2 --- Stretch sensitivity of aortic and carotid baroreceptor neurons --- p.108 / Chapter 5.3.3 --- mRNA expression of mechanosensitive TRP channels in aortic and carotid baroreceptor neurons --- p.109 / Chapter 5.3.4 --- Protein expression of TRPV4 channels in aortic and carotid baroreceptor neurons --- p.109 / Chapter 5.3.5 --- Involvement of TRPV4 in stretch-induced [Ca²⁺]i response in baroreceptor neurons --- p.110 / Chapter 5.4 --- Discussions --- p.111 / Figures --- p.116 / Chapter Chapter 6: --- General conclusions and future directions --- p.124 / Figures --- p.128 / References --- p.133

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.

Title: What explains variability in blood pressure readings? Multilevel analysis of data from 8,731 older adults in 20 Ontario Communities Objectives: Despite universal healthcare and drug coverage for adults aged 65 and over in Ontario, hypertension, a treatable condition, remains uncontrolled among many older adults. Moreover, there are geographic disparities in blood pressure and hypertension within and across Canadian provinces and territories. Using baseline data collected on 8,731 older adults participating in the Cardiovascular Health Awareness Program (CHAP) in 20 randomly selected Ontario communities, we investigated associations between systolic blood pressure (SBP) and individual- and community-level characteristics, controlling for self-reported use of blood pressure medications. Method: Older adults were recruited via invitation by local family physicians, public advertising and word of mouth to attend community pharmacy sessions. During the sessions, trained older adult volunteers assisted participants to complete a cardiovascular disease risk factor questionnaire and blood pressure assessments using an automated blood pressure measuring device. The Postal Code Conversion File Plus was used to confirm residence within one of the 20 study communities. A multilevel linear regression analysis with participants nested within communities was used to determine which individual- and/or community-level characteristics were associated with measured systolic blood pressure level controlling for self-reported use of blood pressure medication. Results: 4,706 participants (53.9%) reported the use of blood pressure medication. Mean systolic blood pressure (SBP) levels varied among the 20 communities from 128.1 mmHg to 134.7 mmHg for participants not using blood pressure medication and from 131.9 mmHg to 139.0 mmHg for participants using blood pressure medication. The intraclass correlation coefficients were very small: less than 0.2% of the total variance was between communities. Among participants not using blood pressure medication, SBP was associated with the following individual- level characteristics: age, sex, body mass index , smoking, physical activity, stress, fruit/vegetable intake, and alcohol consumption and the following community-level characteristics: community size, community growth and the Rurality Index. Among participants using blood pressure medication, SBP was associated with the following individual-level characteristics: age, sex, body mass index, diabetes, fruit/vegetable intake, alcohol intake and one community-level characteristic: community size. The significance and magnitude of these associations were modified by the use of blood pressure medication. Conclusion: The majority of the variability in blood pressure occurs at the individual-level. There are specific individual- and community-level factors that explain variability in blood pressure readings among communities. These results can be used to inform health promotion strategies to decrease mean levels of blood pressure among older adults.

Title: What explains variability in blood pressure readings? Multilevel analysis of data from 8,731 older adults in 20 Ontario Communities Objectives: Despite universal healthcare and drug coverage for adults aged 65 and over in Ontario, hypertension, a treatable condition, remains uncontrolled among many older adults. Moreover, there are geographic disparities in blood pressure and hypertension within and across Canadian provinces and territories. Using baseline data collected on 8,731 older adults participating in the Cardiovascular Health Awareness Program (CHAP) in 20 randomly selected Ontario communities, we investigated associations between systolic blood pressure (SBP) and individual- and community-level characteristics, controlling for self-reported use of blood pressure medications. Method: Older adults were recruited via invitation by local family physicians, public advertising and word of mouth to attend community pharmacy sessions. During the sessions, trained older adult volunteers assisted participants to complete a cardiovascular disease risk factor questionnaire and blood pressure assessments using an automated blood pressure measuring device. The Postal Code Conversion File Plus was used to confirm residence within one of the 20 study communities. A multilevel linear regression analysis with participants nested within communities was used to determine which individual- and/or community-level characteristics were associated with measured systolic blood pressure level controlling for self-reported use of blood pressure medication. Results: 4,706 participants (53.9%) reported the use of blood pressure medication. Mean systolic blood pressure (SBP) levels varied among the 20 communities from 128.1 mmHg to 134.7 mmHg for participants not using blood pressure medication and from 131.9 mmHg to 139.0 mmHg for participants using blood pressure medication. The intraclass correlation coefficients were very small: less than 0.2% of the total variance was between communities. Among participants not using blood pressure medication, SBP was associated with the following individual- level characteristics: age, sex, body mass index , smoking, physical activity, stress, fruit/vegetable intake, and alcohol consumption and the following community-level characteristics: community size, community growth and the Rurality Index. Among participants using blood pressure medication, SBP was associated with the following individual-level characteristics: age, sex, body mass index, diabetes, fruit/vegetable intake, alcohol intake and one community-level characteristic: community size. The significance and magnitude of these associations were modified by the use of blood pressure medication. Conclusion: The majority of the variability in blood pressure occurs at the individual-level. There are specific individual- and community-level factors that explain variability in blood pressure readings among communities. These results can be used to inform health promotion strategies to decrease mean levels of blood pressure among older adults.

The purpose of the present study was to explore the relationship between internalized racism, stereotype threat, self-handicapping, test performance, and cardiovascular responses in Black individuals. Stereotype threat, or apprehension about confirming a negative stereotype, has been shown to lead to self-handicapping, poor academic performance, as well as increased cardiovascular reactivity. Internalized racism, or the acceptance of negative stereotypes about one's group, is a factor that may moderate these relationships. One-hundred nine (84% female, 16% male) Black undergraduates participated in a laboratory study. Half of the participants were put in a stereotype-threatened condition and the other half were in a neutral condition. The participants were permitted unlimited time in which to practice for a verbal test and then were tested on their verbal ability while their blood pressure was monitored. Results indicated that internalized racism moderates the relationship between stereotype threat and systolic blood pressure, but not diastolic blood pressure or heart rate. However, the moderating effect of internalized racism in the relationship between stereotype threat and self-handicapping or test performance was not significant. It seems that individuals who do not accept the negative stereotypes about Blacks as a group experienced increased systolic blood pressure responses in stereotype-threatened situations compared to Black individuals who do accept the negative stereotypes. The implication is that Black individuals who challenge negative stereotypes will feel more stress when placed in situations where they are at risk of confirming those negative stereotypes. This study provides insight into reasons for the variability of cardiovascular disease among Black Americans, who typically experience a higher incidence overall compared to other ethnic groups.

Title: What explains variability in blood pressure readings? Multilevel analysis of data from 8,731 older adults in 20 Ontario Communities Objectives: Despite universal healthcare and drug coverage for adults aged 65 and over in Ontario, hypertension, a treatable condition, remains uncontrolled among many older adults. Moreover, there are geographic disparities in blood pressure and hypertension within and across Canadian provinces and territories. Using baseline data collected on 8,731 older adults participating in the Cardiovascular Health Awareness Program (CHAP) in 20 randomly selected Ontario communities, we investigated associations between systolic blood pressure (SBP) and individual- and community-level characteristics, controlling for self-reported use of blood pressure medications. Method: Older adults were recruited via invitation by local family physicians, public advertising and word of mouth to attend community pharmacy sessions. During the sessions, trained older adult volunteers assisted participants to complete a cardiovascular disease risk factor questionnaire and blood pressure assessments using an automated blood pressure measuring device. The Postal Code Conversion File Plus was used to confirm residence within one of the 20 study communities. A multilevel linear regression analysis with participants nested within communities was used to determine which individual- and/or community-level characteristics were associated with measured systolic blood pressure level controlling for self-reported use of blood pressure medication. Results: 4,706 participants (53.9%) reported the use of blood pressure medication. Mean systolic blood pressure (SBP) levels varied among the 20 communities from 128.1 mmHg to 134.7 mmHg for participants not using blood pressure medication and from 131.9 mmHg to 139.0 mmHg for participants using blood pressure medication. The intraclass correlation coefficients were very small: less than 0.2% of the total variance was between communities. Among participants not using blood pressure medication, SBP was associated with the following individual- level characteristics: age, sex, body mass index , smoking, physical activity, stress, fruit/vegetable intake, and alcohol consumption and the following community-level characteristics: community size, community growth and the Rurality Index. Among participants using blood pressure medication, SBP was associated with the following individual-level characteristics: age, sex, body mass index, diabetes, fruit/vegetable intake, alcohol intake and one community-level characteristic: community size. The significance and magnitude of these associations were modified by the use of blood pressure medication. Conclusion: The majority of the variability in blood pressure occurs at the individual-level. There are specific individual- and community-level factors that explain variability in blood pressure readings among communities. These results can be used to inform health promotion strategies to decrease mean levels of blood pressure among older adults.

Thesis (M.S.)--University of Michigan, 1987.