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

The purpose of this thesis was to investigate the effect of corneal swelling on the accuracy of Goldmann tonometry estimates of intraocular pressure (IOP). In the first experiment, central corneal thickness (CCT, ultrasonic pachymetry), IOP (Goldmann tonometry) and corneal curvature (keratometry) was measured in one eye of 25 subjects every two hours for 24 hours, except for 8 hours overnight (no measurements taken), and for the first two hours after awakening (measurement frequency 20 minutes). CCT (+20.1??10.9 pm) and IOP (+3.1??2.4 mmHg) peaked on eye opening, and then decreased at a similar rate (r=0.967, p<0.001) for the next two hours. Corneal swelling may have influenced the accuracy of Goldmann IOP measurements during this time. In the second and third studies, the CCT, IOP and corneal curvature were measured in both eyes of two groups of 25 subjects before and after the induction of corneal swelling, resulting from two hours of monocular closed eye contact lens wear. The increase in IOP was correlated to the increase in CCT at a rate of 0.33 to 0.48 mmHg per 10 pm, which signified an overestimation error in Goldmann IOP measurement. However, the change in IOP could not be accounted for solely by the change in CCT. In the fourth study, CCT, IOP and corneal curvature were used in conjunction with the Orssengo-Pye algorithm to determine the range of Young's modulus in the normal population, which was 0.29??0.06 MPa. Physiological variations in Young's modulus had a similar effect on Goldmann tonometry to CCT. In the fifth study, the data collected for studies 2 and 3 was used to calculate the Young's modulus changes associated with corneal swelling, again with the assistance of the Orssengo-Pye algorithm. No systematic change in Young's modulus was recorded after contact lens wear, but the model suggested that corneal biomechanical changes were responsible for the remainder of the change in IOP. All experimental results were combined to develop a model to calculate the diurnal variation of Goldmann IOP errors. The likely error in IOP due to overnight corneal swelling was 0.6 to 1.4 mmHg, which may explain as much as 45% (1.4 mmHg) of the 3.1 mmHg diurnal variation of IOP. In summary, small amounts of corneal swelling were shown to have a clinically significant impact on the accuracy of Goldmann tonometry. This may interfere with the measurement of the diurnal variation of IOP, particularly if measurements are taken prior to the resolution of overnight corneal swelling.

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.

The purpose of this thesis was to investigate the effect of corneal swelling on the accuracy of Goldmann tonometry estimates of intraocular pressure (IOP). In the first experiment, central corneal thickness (CCT, ultrasonic pachymetry), IOP (Goldmann tonometry) and corneal curvature (keratometry) was measured in one eye of 25 subjects every two hours for 24 hours, except for 8 hours overnight (no measurements taken), and for the first two hours after awakening (measurement frequency 20 minutes). CCT (+20.1??10.9 pm) and IOP (+3.1??2.4 mmHg) peaked on eye opening, and then decreased at a similar rate (r=0.967, p<0.001) for the next two hours. Corneal swelling may have influenced the accuracy of Goldmann IOP measurements during this time. In the second and third studies, the CCT, IOP and corneal curvature were measured in both eyes of two groups of 25 subjects before and after the induction of corneal swelling, resulting from two hours of monocular closed eye contact lens wear. The increase in IOP was correlated to the increase in CCT at a rate of 0.33 to 0.48 mmHg per 10 pm, which signified an overestimation error in Goldmann IOP measurement. However, the change in IOP could not be accounted for solely by the change in CCT. In the fourth study, CCT, IOP and corneal curvature were used in conjunction with the Orssengo-Pye algorithm to determine the range of Young's modulus in the normal population, which was 0.29??0.06 MPa. Physiological variations in Young's modulus had a similar effect on Goldmann tonometry to CCT. In the fifth study, the data collected for studies 2 and 3 was used to calculate the Young's modulus changes associated with corneal swelling, again with the assistance of the Orssengo-Pye algorithm. No systematic change in Young's modulus was recorded after contact lens wear, but the model suggested that corneal biomechanical changes were responsible for the remainder of the change in IOP. All experimental results were combined to develop a model to calculate the diurnal variation of Goldmann IOP errors. The likely error in IOP due to overnight corneal swelling was 0.6 to 1.4 mmHg, which may explain as much as 45% (1.4 mmHg) of the 3.1 mmHg diurnal variation of IOP. In summary, small amounts of corneal swelling were shown to have a clinically significant impact on the accuracy of Goldmann tonometry. This may interfere with the measurement of the diurnal variation of IOP, particularly if measurements are taken prior to the resolution of overnight corneal swelling.

Piezoprobes of design Phillips-Curzon 1 mm in diameter have been calibrated in the pressure range 0.2 to 35 atm. Step pressure pulses for the calibration were produced with plane shock waves in the range 0.2-1 atm, and with plane detonations in Acetylene-Oxygen in the range 2-35 atm. The calibrated probes were used to measure the space-time pressure profiles in I) concentric detonations II) radiation fronts behind windows and III) pressure waves induced by an intense light source. The measurements supported existing models of the dynamics of these pulsed discharges. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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

A kinetic model was applied to vapor pressure data obtained by a variable flow method. The vapor pressures of benzoic acid, naphthalene, benzophenone, and phenylhydrazine were measured at temperatures of 293K to 307K. The data are summarized in the data table on the following page. These data were obtained by passing air over a sample of the substance in a tube. The air stream was combusted, and a flame ionization detector was used to measure the mass of CO2 so obtained. Several different flow rates were used at each temperature with each substance.

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.

Xiang Xiaoyan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background of Hypertension --- p.1 / Chapter 1.1.1 --- Definition of Blood Pressure --- p.1 / Chapter 1.1.2 --- Hypertension and Its Prevalence --- p.2 / Chapter 1.2 --- Blood Pressure Measurement Techniques --- p.5 / Chapter 1.2.1 --- Invasive Blood Pressure Measurement Techniques --- p.5 / Chapter 1.2.2 --- Non-invasive Blood Pressure Measurement Techniques --- p.6 / Chapter 1.3 --- Accurate BP Measurements --- p.12 / Chapter 1.3.1 --- Error Source for BP Measurement by Conventional Techniques --- p.12 / Chapter 1.3.2 --- Accurate BP Measurement --- p.13 / Chapter 1.4 --- Objectives of the Thesis --- p.15 / Chapter 1.5 --- Organization of the Thesis --- p.16 / References --- p.17 / Chapter Chapter 2 --- Current Standards for the Conventional Blood Pressure Measurement Devices --- p.20 / Chapter 2.1 --- Introduction --- p.20 / Chapter 2.2 --- Current Standards for the Cuff-based BP Measurement Devices --- p.21 / Chapter 2.2.1 --- AAMI Standard --- p.21 / Chapter 2.2.2 --- BHS Protocol --- p.22 / Chapter 2.2.3 --- Other Protocols --- p.23 / Chapter 2.3 --- Comparison of the 2002 AAMI and 1993 BHS Protocols - Protocol Setup --- p.25 / Chapter 2.4 --- Comparison of the 2002 AAMI and 1993 BHS Protocols 一 Accuracy Criteria --- p.29 / Chapter 2.5 --- Relationship between the AAMI Accuracy Criteria and the BHS Grading System --- p.31 / Chapter 2.5.1 --- Theoretical Mapping Relationship --- p.31 / Chapter 2.5.2 --- Application of the Mapping Model: Estimate the BHS Grades from the Reported Sample ME and SD --- p.34 / Chapter 2.5.3 --- Application of the Mapping Model: Explain the Evaluation of the Results from the Clinical Survey by the ESH --- p.36 / Chapter 2.6 --- Discussion --- p.36 / References --- p.40 / Chapter Chapter 3 --- Distribution Analysis of the Blood Pressure Measurement Errors --- p.42 / Chapter 3.1 --- Introduction --- p.42 / Chapter 3.2 --- Error Distribution Estimated from the Published Data --- p.43 / Chapter 3.2.1 --- Methodology --- p.43 / Chapter 3.2.2 --- Data Analysis --- p.44 / Chapter 3.2.3 --- Session Summary --- p.46 / Chapter 3.3 --- Error Distribution Estimated from the Experimental Data --- p.46 / Chapter 3.3.1 --- BP Measurement Error Obtained from Automatic BP Meter --- p.46 / Chapter 3.3.2 --- Distribution Analysis by the Normal Quantile-Quantile Plot --- p.47 / Chapter 3.3.3 --- Background of Student's t Distribution --- p.48 / Chapter 3.3.4 --- Parameter Estimation - Maximum Likelihood Method --- p.50 / Chapter 3.3.5 --- Goodness-of-fit Test - Kolmogorov-Smirnov Test --- p.53 / Chapter 3.3.6 --- Goodness-of-fit Test ´ؤ Chi-Square Test --- p.56 / Chapter 3.4 --- Discussion --- p.63 / References --- p.65 / Chapter Chapter 4 --- A Model Based Study of the Parameters Used by Existing Standards --- p.67 / Chapter 4.1 --- Introduction --- p.67 / Chapter 4.2 --- Background of Method Comparison Study --- p.68 / Chapter 4.2.1 --- Four Areas in Method Comparison Study --- p.68 / Chapter 4.2.2 --- Analysis of Previous Methodology and Statistical Parameters --- p.70 / Chapter 4.3 --- Theoretical Mapping Relationship: Based on the General t Distribution --- p.72 / Chapter 4.3.1 --- "Relationship among CP5, CP10 and CP15 in Each Grade for the 1993 BHS Protocol" --- p.76 / Chapter 4.3.2 --- Relationships between the Criteria in Each Grade for the 1993 BHS Protocol and the AAMI Standard --- p.77 / Chapter 4.3.3 --- Comparison of Parameters --- p.80 / Chapter 4.4 --- Mean of the Absolute Errors (MAE) and Its Estimation --- p.81 / Chapter 4.4.1 --- The Relationship between MAE and Other Parameters --- p.81 / Chapter 4.4.2 --- Analysis of the Example Data --- p.84 / Chapter 4.4.3 --- Estimation of MAEt --- p.84 / Chapter 4.5 --- Discussion --- p.88 / References --- p.90 / Chapter Chapter 5 --- Experimental Study and an Evaluation Protocol Proposed for the Wearable BP Measurement Devices --- p.92 / Chapter 5.1 --- Introduction --- p.92 / Chapter 5.2 --- Description of the Experiment --- p.93 / Chapter 5.3 --- Data Analysis --- p.95 / Chapter 5.3.1 --- Data Used for the Study --- p.95 / Chapter 5.3.2 --- Error Distribution Analysis --- p.96 / Chapter 5.3.3 --- Evaluation of the Automatic BP Meter and the PTT-Based BP Measurement Device by AAMI and 1993 BHS Standards --- p.99 / Chapter 5.3.4 --- Evaluation the Automatic BP Meter and the PTT-Based BP Measurement Device by the Proposed Parameter --- p.101 / Chapter 5.4 --- Proposed Evaluation Procedure --- p.101 / Chapter 5.4.1 --- Introduction --- p.101 / Chapter 5.4.2 --- Determination of Parameters and Criteria --- p.102 / Chapter 5.4.3 --- Proposed Evaluation Procedure --- p.103 / Chapter 5.5 --- Discussion --- p.105 / References --- p.108 / Chapter Chapter 6 --- Conclusion and Future Work --- p.110 / Chapter 6.1 --- Conclusion and Major Contributions --- p.110 / Chapter 6.2 --- Future Works --- p.113 / References --- p.115 / Appendix A Deviation of Some Equations --- p.116 / Chapter A.1 --- CP for Certain Limit of L as a Function of ME and SD --- p.116 / Chapter A.2 --- MAE as a Function of Location and Scale Parameters --- p.119 / Chapter A.3 --- "Relationship between ME, MAE and Root Mean Squared Error (RMSE) if the error distribution is unknown" --- p.121 / Appendix B List of Publications and Awards Related to This Study --- p.123