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Cardiovascular diseases (CVD) are the leading cause of death. It is also one of the major factors resulting sudden deaths in exercises. Blood pressure (BP) is one of the vital diagnostic parameters to reflect the functionality of cardiovascular system and evaluate the conditions of CVD. However, current BP measuring devices usually require the occlusion of cuff that causes inconvenience to users during measurement. They are neither suitable nor practical for long-term monitoring. Pulse transit time (PTT), the duration for a pressure pulse wave to travel from one arterial site to another, has been proposed as a potential parameter for cuffless BP measurement in recent decades. Because of its cuffless and non-invasive measuring features, the aim of the present study is to develop a novel PTT-based BP estimation for cuffless and non-invasive monitoring of BP under resting and exercise conditions. / The accuracy of proposed method for continuous BP monitoring has been evaluated on seventeen subjects during cycling. Brachial BP was measured by FinapresRTM (Fin. BP) and a trained nurse (Nur. BP). In approximate 22000 beats, the differences between predictions and Fin. BP were 1.3+/-13.0 mmHg for SBP and -1.5+/-6.1 mmHg for DBP respectively. The intermittent BP measurements using the proposed method were compared to the readings from FinapresRTM and nurse separately. The differences between proposed method and Nur. BP were 0.9+/-9.9 mmHg for SBP and -1.2+/-5.2 mmHg for DBP respectively. The differences between proposed method and Fin. BP were -0.1+/-12.6 mmHg for SBP and -1.4+/-5.9 mmHg for DBP respectively. The predictions using the proposed method were more consistent with the nurse readings. Furthermore, thorax impedance signal was proposed for cuffless BP estimation and it was examined on twenty-two subjects. The results illustrated that proposed parameters, measured from Q wave of electrocardiogram to the peaks of thorax impedance signal and its derivative, were highly correlated with BP. They were potential parameters to provide non-invasive and cuffless BP estimation. / To conclude, the accuracy of proposed method was comparable to the cuff-based approaches under resting and exercise conditions. This work is potential to solve the problems due to prevalence of CVD and rising aging population. (Abstract shortened by UMI.) / Wong, Yee Man. / Adviser: Y. T. Zhang. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3650. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / 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.

Liu, Yinbo. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 74-79). / Abstracts in English and Chinese. / Abstract --- p.i / List of Figures --- p.iv / List of Tables --- p.viii / Introduction --- p.1 / Chapter 1.1 --- Current status of Blood Pressure Management --- p.1 / Chapter 1.2 --- Current Status of Noninvasive Blood Pressure Measurement Techniques --- p.4 / Chapter 1.3 --- Motivations and Objectives of This Thesis --- p.9 / Chapter 1.4 --- Organization of This Thesis --- p.9 / Backgrounds --- p.11 / Chapter 2.1 --- Principle of the Pulse Transit Time-based Approach for BP Measurement --- p.11 / Chapter 2.1.1 --- General Descriptions --- p.11 / Chapter 2.1.2 --- Pressure Wave Propagation in Cylindrical Arteries --- p.13 / Chapter 2.1.3 --- Determining the PTT for BP Measurement --- p.14 / Chapter 2.2 --- Backgrounds for Pressure Related Elastic Properties of Artery --- p.17 / Chapter 2.2.1 --- Transmural Pressure and Its Components --- p.17 / Chapter 2.2.2 --- Volume-pressure Models --- p.19 / Chapter 2.2.3 --- Types and Structure of the Artery and Its Properties --- p.20 / Chapter 2.3 --- Literature Review on the Calibration Methods for Cuffless Blood Pressure Measurements --- p.22 / Chapter 2.4 --- Section Summary --- p.25 / Investigations on Factors Affecting PTT or BP --- p.26 / Chapter 3.1 --- The Effects of External Pressure --- p.26 / Chapter 3.1.1 --- Background --- p.26 / Chapter 3.1.2 --- Experimental protocol --- p.28 / Chapter 3.1.3 --- Analysis for the Effects of External Pressure on PTT --- p.30 / Chapter 3.1.4 --- Section Discussions --- p.31 / Chapter 3.2 --- The Effects of Hydrostatic Pressure --- p.32 / Chapter 3.2.1 --- Experimental protocol --- p.33 / Chapter 3.2.2 --- Analysis for the Effects of Hydrostatic Pressure on PTT --- p.34 / Chapter 3.2.3 --- Section Discussions --- p.37 / Chapter 3.2.4 --- Section Summary --- p.38 / Modeling the Effect of Hydrostatic Pressure on PTT for A Calibration Method --- p.39 / Chapter 4.1 --- Current Status of Hydrostatic Calibration Approaches --- p.39 / Chapter 4.2. --- Modeling Pulse Transit Time under the Effects of Hydrostatic Pressure for A Hydrostatic Calibration Method: --- p.40 / Chapter 4.2.1 --- Basic BP-PTT model --- p.40 / Chapter 4.2.2 --- V-P relationship Represented by a Sigmoid Curve --- p.40 / Chapter 4.2.3 --- Relating PTT with Hydrostatic Pressure --- p.41 / Chapter 4.2.4 --- Implementing the Hydrostatic Calibration Method for BP Estimation --- p.43 / Chapter 4.3. --- Preliminary Experiment --- p.44 / Chapter 4.3.1. --- Experimental Protocol and Methodology --- p.44 / Chapter 4.3.2. --- Experimental Analysis --- p.46 / Chapter 4.4. --- Section Discussions --- p.48 / Chapter 4.5. --- A Novel Implementation Algorithm of Hydrostatic Calibration Method for Cuffless BP Estimation --- p.49 / Chapter 4.6. --- Section Summary --- p.50 / Experimental Studies for the Hydrostatic Calibration Approach --- p.51 / Chapter 5.1 --- Experimental Analysis --- p.51 / Chapter 5.1.1 --- Experimental Protocol --- p.51 / Chapter 5.1.2 --- Methodology --- p.53 / Chapter 5.1.3 --- Preparations --- p.54 / Chapter 5.1.4 --- Experimental Results --- p.56 / Chapter 5.2 --- Section Discussions --- p.63 / Chapter 5.3 --- Section Summary --- p.70 / Conclusions and Suggestions for Future Works --- p.71 / Chapter 6.1 --- Conclusions --- p.71 / Chapter 6.2 --- Suggestions for Future Works --- p.72 / Reference --- p.71

A non-invasive, in vitro method of estimating mean pulmonary artery pressure (PAP) was developed. This information was obtained by establishing a relationship between the pneumatic right drive pressure (RDP) and PAP waveforms. The RDP-PAP relationship was formalized into a series of multiple-linear regression equations for TAH cardiac cycles of known fill volume (FV). Correlation of computed estimates of PAP to actual measurements showed that these equations were greater than 92% accurate within 1.84 mmHg. In addition, while the RDP-PAP relationships were wholly dependent on FV, it was shown that they are independent of the manner in which FV was obtained. This method proved useful over the clinical operating range of the pneumatic heart driver, as well as over the normal physiological range of PAP in the human. Effectiveness of this method in vivo needs to be demonstrated.

This study was designed to determine which method of measuring the systolic blood pressure is more accurate when determining the ankle/brachial index (ABI), which is an important tool in assessing graft patency for patients who have had peripheral vascular surgery. The accuracy of the stethoscope diaphragm was compared with the stethoscope bell and Doppler methods used to measure the brachial systolic pressure. These pressures were then used in the calculation of the ABI and then the ABI was compared by method and time since surgery. The theoretical framework for this study was drawn from theories on sound generation, transmission and measurement. This study used a two-repeated measures design in which the subjects served as their own control. The results were then analyzed using an ANOVA specific to a two-repeated measures design. The sample consisted of 31 subjects which comprised 80% of all peripheral vascular surgery patients admitted over a two month period to a large tertiary care hospital in Western Canada. The subjects ranged in age from 47 to 82 years, the majority had at least one other medical condition in addition to peripheral vascular disease, were on a variety of medications, and 35% had had previous vascular surgery. The subjects had their brachial systolic blood pressure measured by the three methods on the third, fourth and fifth postoperative day. At the same time they also had their dorsalis pedis and posterior tibial pressures measured by the Doppler method. There was no significant difference in the brachial systolic blood pressure related to the methods used to take the blood pressure, the postoperative day that the blood pressure was measured, nor was there any interaction between method and occasion. Also, there was no significant difference in either the dorsalis pedis or posterior tibial ankle/brachial indices related to method used to measure the brachial systolic blood pressure, the postoperative day the measurement was taken, nor any interaction between method and occasion. The findings suggest that peripheral vascular surgery patients often have systolic pressures that differ between the right and left arm which would make a major difference in the calculation of the ABI. Therefore, the pressures should be measured in both arms, followed by documentation and consistent use of the arm with the highest pressure when determining the ABI. The findings also suggest that inservice education and periodic skill checking be implemented when the nurse is required to employ the Doppler method owing to the number of variables to consider when operating this instrument. / Applied Science, Faculty of / Nursing, School of / Graduate

Mobile health (mHealth) promises a paradigm shift towards digital medicine where biomarkers in individuals are continuously monitored with wearable biosensors in decentralized locations to facilitate improved diagnosis and treatment of disease. Despite recent progress, the impact of wearables in health monitoring remains limited due to the lack of devices that measure meaningful health data and are accurate, minimally invasive, and unobtrusive. Therefore, next-generation biosensors must be developed to realize the vision of mHealth. To that end, in this dissertation, we develop wearable biochemical and biophysical sensors for health monitoring that can serve as platforms for future mHealth devices. First, we developed a skin patch biosensor for minimally invasive quantification of endogenous biochemical analytes in dermal interstitial fluid. The patch consisted of a polyacrylamide hydrogel microfilament array with covalently-tethered fluorescent aptamer sensors. Compared to prior approaches for hydrogel-based sensing, the microfilaments enable in situ sensing without invasive injection or removal. The patch was fabricated via replica molding with high-percentage polyacrylamide that provided high elastic modulus in the dehydrated state and optical transparency in the hydrated state. The microfilaments could penetrate the skin with low pain and without breaking, elicited minimal inflammation upon insertion, and were easily removed from the skin. To enable functional sensing, the polyacrylamide was co-polymerized with acrydite-modified aptamer sensors for phenylalanine that demonstrated reversible sensing with fast response time in vitro. In the future, hydrogel microfilaments could be integrated with a wearable fluorometer to serve as a platform for continuous, minimally invasive monitoring of intradermal biomarkers. Next, we shift focus to biophysical signals and the required signal processing, particularly towards the development of cuffless blood pressure (BP) monitors. Cuffless BP measurement could enable early detection and treatment of abnormal BP patterns and improved cardiovascular disease risk stratification. However, the accuracy of emerging cuffless monitoring methods is compromised by arm movement due to variations in hydrostatic pressure, limiting their clinical utility. To overcome this limitation, we developed a method to correct hydrostatic pressure errors in noninvasive BP measurements. The method tracks arm position using wearable inertial sensors at the wrist and a deep learning model that estimates parameterized arm-pose coordinates; arm position is then used for analytical hydrostatic pressure compensation. We demonstrated the approach with BP measurements derived from pulse transit time, one of the most well-studied modalities for cuffless BP measurement. Across hand heights of 25 cm above or below the heart, mean errors for diastolic and systolic BP were 0.7 ± 5.7 mmHg and 0.7 ± 4.9 mmHg, respectively, and did not differ significantly across arm positions. This method for correcting hydrostatic pressure may facilitate the development of cuffless devices that can passively monitor BP during everyday activities. Finally, towards a fully integrated device suitable for ambulatory BP monitoring, we developed a deep learning model for BP prediction from photoplethysmography waveforms acquired at a single measurement site. In contrast to competing methods that require thousands of measurements for adaptation to new users, our proposed approach enables accurate BP prediction following calibration with a single reference measurement. The model uses a convolutional neural network with temporal attention for feature extraction and a Siamese architecture for effective calibration. To prevent overfitting to person-specific variations that fail to generalize, we introduced an adversarial patient classification task to encourage the learning of patient-invariant features. Following calibration, the model accurately predicted diastolic and systolic BP over 24 hours, with mean errors of -0.07 ± 3.86 mmHg and -0.94 ± 7.32 mmHg, respectively, which meets the accuracy criteria for clinical validation. The proposed deep learning model could integrate with wearable photoplethysmography sensors, such as those in smartwatches, to enable cuffless ambulatory BP monitoring. Underlying this work is the development of minimally invasive biosensors that can integrate with wearable mHealth devices to facilitate passive monitoring of health parameters. The proliferation of mHealth wearables will enable the widespread collection of meaningful health data that provide actionable insights and a more comprehensive understanding of patient health. In a step towards this vision, we leveraged innovations in materials, multi-sensor fusion, and data-driven signal processing to develop sensors for measuring biochemical and biophysical markers. Overall, this work serves as an example of how the adoption of new technologies can facilitate the development of next-generation wearable biosensors.

MSc (Nursing), Faculty of Health Sciences, University of the Witwatersrand / The purpose of the study was to describe and compare the limits of agreement between invasive blood pressure (IBP) and non-invasive blood pressure (NIBP) readings obtained on patients in the adult critical care units (CCU) of a tertiary health care institution, to describe the factors that affect accuracy of both techniques, to describe the difference in terms of accuracy and sensitivity and the reasons given by the clinical practitioners for their choice of blood pressure measurement technique. A non-experimental descriptive comparative, prospective design was utilized in this two part study. The sample comprised of CCU patients (n = 80) in five adult critical care units over a 3-month period. Non-probability purposive sampling was utilized to obtain the desired sample in part one of the study. Data collection was via IBP and NIBP measurements obtained by the researcher and a record review of the patient’s critical care charts. Part two of the study comprised of clinical practitioners (n=50) and convenience sampling method was utilized. Descriptive and inferential statistics were used to analyse data. At the 95% confidence interval, the limits of agreements were found to be in range of ± 35 mmhg of IBP and NIBP systolic, ± 19.5 mmHg of IBP and NIBP diastolic and ±19.3 mmhg IBP and NIBP of mean arterial pressure. In practical terms this means that IBP and NIBP can not be used interchangeably in CCUs as the two methods did not consistently provide similar measurements because there was a high level of disagreement that included clinically important discrepancy of more than 10 mmhg which is the cut off acceptable reference in terms of discrepancy between the two BP techniques and add to the growing literature suggesting that IBP remains the gold standard technique for measuring the blood pressure in critical care setting. Factors such as Inotropic/ vasopressor support, sedation / analgesia, mechanical ventilation and severity of illness (APACHE II score) did not show significant influence on the discrepancy of the two BP techniques. In the second part of the study, more than 80 % of the sample of clinical practitioners acknowledged that the IBP technique remains the gold standard.