Teng Xiaofei. / "June 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Despite having the numerous evolved heart rate measuring devices and progress in their development over the years, there always remain the challenges of modern signal processing implementation by a comparatively small size wearable device. This thesis paper presents a wearable reflectance photoplethysmography (PPG) sensor system for measuring the heart rate of a user both in steady and moving states. The size and, power consumption of the device are considered while developing, to ensure an easy deployment of the unit at the measuring site and the ability to power the entire unit with a battery .The selection of both the electronic circuits and signal processing techniques is based on their sensitivity to PPG signals, robustness against noise inducing artifacts and miniaturization of the entire measuring unit. The entire signal chain operates in the discrete-time, which allows the entire signal processing to be implemented in firmware on an embedded microprocessor. The PPG sensor system is implemented on a single PCB that consumes around 7.5mW of power. Benchmarking tests with standard heart rate measuring devices reveal that the developed measurement unit (combination of the PPG sensor system, and inertial measurement unit (IMU) developed in-house at Acreo Swedish ICT, and a battery) is comparable to the devices in detecting heart rate even in motion artifacts environment. This thesis work is carried out in Acreo Swedish ICT, Gothenburg, Sweden in collaboration with MidSweden University, Sundsvall, Department of Electronics Design. This report can be used as ground work for future development of wearable heart rate measuring units at Acreo Swedish ICT.

Photoplethysmography (PPG) has become widely accepted as a valuable clinical tool for performing non-invasive biomedical monitoring. The dominant clinical application of PPG has been pulse oximetry, which uses spectral analysis of the peripheral blood supply to establish haemoglobin saturation. PPG has also found success in screening for venous dysfunction, though to a limited degree. Arterial Disease (AD) is a condition where blood flow in the arteries of the body is reduced,a condition known as ischaernia. Ischaernia can result in pain in the affected areas, such as chest pain for an ischearnic heart, but does not always produce symptoms. The most common form of AD is arteriosclerosis, which affects around 5% of the population over 50 years old. Arteriosclerosis, more commonly known as 'hardening of the arteries' is a condition that results in a gradual thickening, hardening and loss of elasticity in the walls of the arteries, reducing overall blood flow. This thesis investigates the possibility of employing PPG to perform vascular assessment, specifically arterial assessment, in two ways. PPG based perfusion monitoring may allow identification of ischaernia in the periphery. To further investigate this premise, prospective experimental trials are performed, firstly to assess the viability of PPG based perfusion monitoring and culminating in the development of a more objective method for determining ABPI using PPG based vascular assessment. A complex interaction between the heart and the connective vasculature, detected at the measuring site, generates the PPG signal. The haemodynamic properties of the vasculature will affect the shape of the PPG waveform, characterising the PPG signal with the properties of the intermediary vasculature. This thesis investigates the feasibility of deriving quantitative vascular parameters from the PPG signal. A quantitative approach allows direct identification of pathology, simplifying vascular assessment. Both forward and inverse models are developed in order to investigate this topic. Application of the models in prospective experimental trials with both normal subjects and subjects suffering PVD have shown encouraging results. It is concluded that the PPG signal contains information on the connective vasculature of the subject. PPG may be used to perform vascular assessment using either perfusion based techniques, where the magnitude of the PPG signal is of interest, or by directly assessing the connective vasculature using PPG, where the shape of the PPG signal is of interest. it is argued that PPG perfusion based techniques for performing the ABPI diagnosis protocol can offer greater sensitivity to the onset of PAD, compared to more conventional methods. It is speculated that the PPG based ABPI diagnosis protocol could provide enhanced PAD diagnosis, detecting the onset of the disease and allowing a treatmenpt lan to be formed soonert han was possible previously. The determination of quantitative vascular parameters using PPG shape could allow direct vascular diagnosis, reducing subjectivity due to interpretation. The prospective trials investigating PPG shape analysis concentrated on PVD diagnosis, but it is speculated that quantitative PPG shaped based vascular assessment could be a powerful tool in the diagnosis of many vascular based pathological conditions.

Information about the central venous pressure is important in evaluating several clinical conditions including cardiac failure and volume overload. The jugular veins serve as a primary route for the indirect estimation of the central venous pressure or waveform. The conventional methods for acquiring the central venous pressure in these veins have been through neck visualization and the insertion of catheters. Even though these procedures are effective if done properly, they have various downsides such as being invasive, inaccurate and time consuming. In this research, a sensor is proposed for the noninvasive detection of central venous waveforms within the jugular veins. The sensor is a reflectance configured probe which utilizes laser based on the photoplethysmography principle. The effectiveness of the sensor was tested in-vitro using a mock circulatory loop and was also tested on a single human subject. The results from the tests indicated a very good sensor response in estimating pressure waveforms.

This thesis considers methods for extracting blood volume pulse (BVP) representations from video of the human face. Whereas most previous systems have been concerned with estimating vital signs such as average heart rate, this thesis addresses the more difficult problem of recovering BVP signal morphology. We present a new approach that is inspired by temporal encoder-decoder architectures that have been used for audio signal separation. As input, this system accepts a temporal sequence of RGB (red, green, blue) values that have been spatially averaged over a small portion of the face. The output of the system is a temporal sequence that approximates a BVP signal. In order to reduce noise in the recovered signal, a separate processing step extracts individual pulses and performs normalization and outlier removal. After these steps, individual pulse shapes have been extracted that are sufficiently distinct to support biometric authentication. Our findings demonstrate the effectiveness of our approach in extracting BVP signal morphology from facial videos, which presents exciting opportunities for further research in this area. The source code is available at https://github.com/Adleof/CVPM-2023-Temporal-Encoder-Decoder-iPPG / Master of Science / This thesis considers methods for extracting blood volume pulse (BVP) representations from video of the human face. We present a new approach that is inspired by the method that has been used for audio signal separation. The output of our system is an approximation of the BVP signal of the person in the video. Our method can extract a signal that is sufficiently distinct to support biometric authentication. Our findings demonstrate the effectiveness of our approach in extracting BVP signal morphology from facial videos, which presents exciting opportunities for further research in this area.

A low cost Heart Beat Monitoring device (HBMD) for detecting heart beat in beats per minute is presented in this thesis. An optical technique called “Photoplethysmography” is utilized by attaching to the base of the finger for monitoring beat to beat pulsation. Two major design issues addressed in this research is to achieve a strong and accurate PPG signal and simultaneously minimizing physiological artefacts and interference. In order to achieve the aim and objectives of the research, this thesis thoroughly explores two new signal conditioning hardware designs. Firstly is the design and fabrication of a low cost reflectance mode PPG heart monitor using parallel port interfacing and secondly are the design and development of a portable transmission mode PPG heart monitor using microcontroller PIC16F84A and PIC16F87. Both PPG heart monitor design is divided into three phases. First is the detection of weak pulses through the fingertip. The PPG signal is then amplified, filtered and digitized by the signal processing unit. Finally the heart rate is calculated, analyzed and displayed on the computer using parallel port interface and on the liquid crystal display using microcontroller PIC16F87. A comprehensive circuit design and analysis work was implemented verified by Proteus VSM circuit simulations and laboratory experiments. Data is presented from the method comparison study in which heart rates measured with the reflectance mode PPG and portable transmission mode PPG heart monitor were compared with those measured with standard techniques on 13 human subjects. Benchmarking tests with approved pulse oximeter and blood pressure monitor Omron M6 reveals that the PPG heart monitor is comparable to those devices in displaying the heart rate. It is also verified through experiments that both PPG heart monitor design fulfill the objectives, including achieving strong and accurate PPG signal, reduction in physiological artefacts and interference and financially low in cost. As the conclusion, the current version of the reflectance mode PPG and portable transmission mode PPG heart monitor successfully measure heart rates fast and reliably in most subjects in different body position. The PPG heart monitor proposed avoid the need to apply electrodes or other sensors in the correct position which directly minimizes the preparation time drastically. This makes the PPG heart monitor more attractive for heart monitoring purpose and its advantage should be explored further. / Ministry of Higher Education Malaysia (MOHE) and Universiti Tun Hussein Onn Malaysia (UTHM)

No description available.

We addressed two interesting video-based health measurements. First is video-based Heart Rate (HR) estimation, known as video-based Photoplethysmography (PPG) or videoplethysmography (VHR). We adapted an existing video-based HR estimation method to produce more robust and accurate results. Specifically, we removed periodic signals from the recording environment by identifying (and removing) frequency clusters that are present the face region and background. This adaptive passband filter generated more accurate HR estimates and allowed other applied filters to work more effectively. Measuring HR at the presence of motions is one of the most challenging problems in recent VHR studies. We investigated and described the motion effects in VHR in terms of the angle change of the subject’s skin surface in relation to the light source. Based on this understanding, we discussed the future work on how we can compensate for the motion artifacts. Another important health information addressed in this thesis is Videosomnography (VSG), a range of video-based methods used to record and assess sleep vs. wake states in humans. Traditional behavioral-VSG (B-VSG) labeling requires visual inspection of the video by a trained technician to determine whether a subject is asleep or awake. We proposed an automated VSG sleep detection system (auto-VSG) which employs motion analysis to determine sleep vs. wake states in young children. The analyses revealed that estimates generated from the proposed Long Short-term Memory (LSTM)-based method with long-term temporal dependency are suitable for automated sleep or awake labeling.

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.

The overall aim of this thesis was to elucidate and investigate psychophysiological aspects and effects of acupuncture and needle stimulation. Within this framework emphasis was directed toward the effects of needle stimulation (acupuncture) on muscle blood flow in the tibialis anterior and trapezius muscles in healthy subjects and patients suffering from chronic muscle pain. This study also included evaluation of a new application of photoplethysmography in noninvasive monitoring of muscle blood flow. The evaluation was based on experiments known to provocate skin or muscle blood flow. The psychological aspects studied comprised the effects of manual acupuncture on pain in fibromyalgia patients and the effects of electro-acupuncture on psychological distress and vasomotor symptoms in postmenopausal women in the clinical context. The results showed that photoplethysmography have potential to noninvasively monitor muscle blood flow and to discriminate between blood flow in skin and muscle, although some considerations still have to be accounted for. It was further shown that muscle blood flow change in response to needle stimulation differed between healthy subjects and patients. Deep needle stimulation in the muscle of healthy subjects consistently increased muscle blood flow more than subcutaneous needle stimulation. In the painful trapezius muscle of FMS patients, however, subcutaneous needling was equal or even more effective in increasing muscle blood flow than deep intramuscular stimulation. Generally, needle stimuli had weak effect on blood flow in the trapezius muscle of the severely affected trapezius myalgia patients, possibly depending on older age and lesser number of patients included in the study. The different patterns of blood flow response to needle stimulation between healthy subjects and patients with chronic muscle pain might be a manifestation of altered somatosensory processing in the patients. The clinical studies showed that best pain relief of acupuncture in FMS patients was achieved in the neck-shoulder region, while the effect on the generalised symptoms was of short duration. Well-being and sleep was found to best predict treatment outcome. The results suggest that acupuncture treatment may be used for the alleviation of neck-shoulder pain, primarily, but it is not an alternative as the sole treatment. Electro-acupuncture, significantly decreased psychological distress and climacteric symptoms in postmenopausal women, but not better than a (near-) placebo control, implying pronounced non-specific effects. / Akupunktur ingår som en del i traditionell kinesisk medicin (TCM) och har använts i över 2000 år för att lindra sjukdom och symptom. I Sverige blev akupunktur godkänd som smärtlindringsmetod inom Hälso- och Sjukvården 1984. Sedan nästan 10 år är akupunktur jämställd med övrig behandling i sjukvården vilket innebär, att akupunktur kan användas även för behandling av annat än smärta. Förutsättningen är emellertid, att det finns tillräckligt med vetenskapliga belägg, s.k. evidens, för detta. I de allra flesta fall saknas det idag. För att säkerställa att evidens föreligger krävs omfattande forskning om effekter av akupunktur. Syftet med de olika studierna i avhandlingen var att belysa och studera psykologiska och fysiologiska aspekter och effekter av akupunktur och nålstimulering. Effekt på blodflöde i hud och muskel undersöktes på friska personer och på patienter med kronisk muskelsmärta. Normalt krävs ett mindre kirurgiskt ingrepp för att mäta blodflöde i muskel, men i dessa studier användes en mätmetod, som enkelt och utan ingrepp (icke-invasivt) i normala fall används för att mäta blodflöde i huden, s.k. fotopletysmografi (PPG, eng.). Med hjälp av ny teknik användes PPG i dessa studier för att mäta även muskelblodflöde. En studie för utvärdering av den nya PPG-tekniken ingick också i avhandlingen. Utvärderingen av mätmetoden visade goda möjligheter att mäta muskelblodflöde icke-invasivt med hjälp av PPG. Hos friska personer blev effekten på blodflödet störst vid djup stimulering i muskeln och där den s.k. DeQi-känslan framkallades (som vid klassisk akupunktur). Hos patienter med fibromyalgi var nålstimulering i huden lika, eller t.o.m. mer, effektiv att öka muskelblodflödet i skuldran än den djupa nålstimuleringen. De olika mönstren av blodflödesökning mellan de friska personerna och patienterna kan bero på ett förändrat reaktionssätt i nervsystemet som svar på smärtsam stimulering. I två kliniska studier studerades den smärtlindrande effekten av manuell akupunktur vid fibromyalgi och effekten av elektroakupunktur på stress och klimakteriebesvär hos kvinnor i övergångsåldern. Akupunktur vid fibromyalgi visade sig ha bäst smärtlindrande effekt i nack-skulderområdet, medan effekten på de generella symptomen var kortvarig. Patienter som mådde och sov relativt bra erhöll bäst effekt. Efter en behandlingsserie, bestående av elektroakupunktur, minskade stress och klimakteriebesvär påtagligt hos kvinnorna i övergångsåldern, men inte mer än hos en grupp kvinnor, som fick en kontrollbehandling bestående av mycket ytligt placerade nålar i huden. Detta tyder på att en betydlig del av behandlingsresultatet utgjordes av ospecifika effekter eller, s.k. eller placeboeffekter.