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1
Hayes, Matthew J. "Artefact reduction in photoplethysmography." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/7094.
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The use of optical techniques in biomedical monitoring and diagnosis is becoming increasingly widespread, primarily because of the non-invasive nature of optically derived measurements. Physiological analysis is usually achieved by characterisation of the spectral or temporal properties of the interaction between light and the anatomy. Although some optical measurements require complex instrumentation and protocols, recent technological advances have resulted in robust and compact equipment that is now used routinely in a multitude of clinical contexts. Unfortunately, these measurements are inherently sensitive to corruption from dynamic physical conditions or external sources of light, inducing signal artefact. Artefact is the primary restriction in the applicability of many optical measurements, especially for ambulatory monitoring and tele-medicine. The most widely used optical measurement is photoplethysmography, a technique that registers dynamic changes in blood volume throughout the peripheral vasculature and can be used to screen for a number of venous disorders, as well as monitoring the cardio-vascular pulse wave. Although photoplethysmographic devices are now incorporated into many patient-monitoring systems, the prevalent application is a measurement known as pulse oximetry, which utilises spectral analysis of the peripheral blood to estimate the arterial haernoglobin oxygen saturation. Pulse oximetry is well established as an early warning for hypoxia and is now mandatory under anaesthesia in many countries. The problem of artefact is prominent in these continuous monitoring techniques, where it is often impossible to control the physical conditions during use. This thesis investigates the possibility of reducing artefact corruption of photoplethysmographic signals in real time, using an electronic processing methodology that is based upon inversion of a physical artefact model. The consequences of this non-linear artefact reduction technique for subsequent signal analysis are discussed, culminating in a modified formulation for pulse oximetry that not only has reduced sensitivity to artefact but also possesses increased generality. The design and construction of a practical electronic system is then used to explore both the implementation issues and the scope of this technique. The performance of artefact reduction obtained is then quantified under realistic experimental conditions, demonstrating that this methodology is successful in removing or reducing a large proportion of artefact encountered in clinically relevant situations. It is concluded that non-linear artefact reduction can be applied to any photoplethysmographic technology, reducing interpretation inaccuracies that would otherwise be induced by signal artefact. It is also speculated that this technology could enable the use of photoplethysmographic systems in applications that are currently precluded by the inherent severity of artefact.
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Shi, Ping. "Photoplethysmography in noninvasive cardiovascular assessment." Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/5399.
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The electro-optic technique of measuring the cardiovascular pulse wave known as photoplethysmography (PPG) is clinically utilised for noninvasive characterisation of physiological components by dynamic monitoring of tissue optical absorption. There has been a resurgence of interest in this technique in recent years, driven by the demand for a low cost, compact, simple and portable technology for primary care and community-based clinical settings, and the advancement of computer-based pulse wave analysis techniques. PPG signal provides a means of determining cardiovascular properties during the cardiac cycle and changes with ageing and disease. This thesis focuses on the photoplethysmographic signal for cardiovascular assessment. The contour of the PPG pulse wave is influenced by vascular ageing. Contour analysis of the PPG pulse wave provides a rapid means of assessing vascular tone and arterial stiffness. In this thesis, the parameters extracted from the PPG pulse wave are examined in young adults. The results indicate that the contour parameters of the PPG pulse wave could provide a simple and noninvasive means to study the characteristic change relating to arterial stiffness. The pulsatile component of the PPG signal is due to the pumping action of the heart, and thus could reveal the circulation changes of a specific vascular bed. Heart rate variability (HRV) represents one of the most promising quantitative markers of cardiovascular control. Calculation of HRV from the peripheral pulse wave using PPG, called pulse rate variability (PRV), is investigated. The current work has confirmed that the PPG signal could provide basic information about heart rate (HR) and its variability, and highly suggests a good alternative to understanding dynamics pertaining to the autonomic nervous system (ANS) without the use of an electrocardiogram (ECG) device. Hence, PPG measurement has the potential to be readily accepted in ambulatory cardiac monitoring due to its simplicity and comfort. Noncontact PPG (NPPG) is introduced to overcome the current limitations of contact PPG. As a contactless device, NPPG is especially attractive for physiological monitoring in ambulatory units, NICUs, or trauma centres, where attaching electrodes is either inconvenient or unfeasible. In this research, a prototype for noncontact reflection PPG (NRPPG) with a vertical cavity surface emitting laser (VCSEL) as a light source and a high-speed PiN photodiode as a photodetector is developed. The results from physiological experiments suggest that NRPPG is reliable to extract clinically useful information about cardiac condition and function. In summary, recent evidence demonstrates that PPG as a simple noninvasive measurement offers a fruitful avenue for noninvasive cardiovascular monitoring. Key words: Photoplethysmography (PPG), Cardiovascular assessment, Pulse wave contour analysis, Arterial stiffness, Heart rate (HR), Heart rate variability (HRV), Pulse rate variability (PRV), Autonomic nervous system (ANS), Electrocardiogram (ECG).
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Cheang, Peck-Yeng (Sharon). "Feasibility of non-contact photoplethysmography." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/34255.
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This thesis explores and investigates the feasibility of a non-contact photoplethysmography system operating in both transmission and reflection modes. Several issues are addressed in the implementation of the non-contact system, including the dynamic range of PPG signals, ambient artefacts and effects of direct coupling, which is light that is detected without any interaction with the measured tissue area. Plethysmography has been used in a range of biomedical applications to study blood volume changes. All current applications employ contact probes, where the transducers are positioned directly on the tissue surface. Non-contact measurements, where the transducers have no direct contact with the tissue surface, i.e. skin, are in demand for clinical benefits. Measurements by non-contact photoplethysmography can be obtained from any tissue since it is not probe limited, can be used on patients with bums as the probe does not touch the skin, and can reduce anxiety in patients, as they are not wired to any equipment.
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Zheng, Jia. "Opto-Physiological Modelling of Imaging Photoplethysmography." Thesis, Loughborough University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519660.
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Sun, Yu. "Imaging photoplethysmography : towards effective physiological measurements." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/9143.
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Since its conception decades ago, Photoplethysmography (PPG) the non-invasive opto-electronic technique that measures arterial pulsations in-vivo has proven its worth by achieving and maintaining its rank as a compulsory standard of patient monitoring. However successful, conventional contact monitoring mode is not suitable in certain clinical and biomedical situations, e.g., in the case of skin damage, or when unconstrained movement is required. With the advance of computer and photonics technologies, there has been a resurgence of interest in PPG and one potential route to overcome the abovementioned issues has been increasingly explored, i.e., imaging photoplethysmography (iPPG). The emerging field of iPPG offers some nascent opportunities in effective and comprehensive interpretation of the physiological phenomena, indicating a promising alternative to conventional PPG. Heart and respiration rate, perfusion mapping, and pulse rate variability have been accessed using iPPG. To effectively and remotely access physiological information through this emerging technique, a number of key issues are still to be addressed. The engineering issues of iPPG, particularly the influence of motion artefacts on signal quality, are addressed in this thesis, where an engineering model based on the revised Beer-Lambert law was developed and used to describe opto-physiological phenomena relevant to iPPG. An iPPG setup consisting of both hardware and software elements was developed to investigate its reliability and reproducibility in the context of effective remote physiological assessment. Specifically, a first study was conducted for the acquisition of vital physiological signs under various exercise conditions, i.e. resting, light and heavy cardiovascular exercise, in ten healthy subjects. The physiological parameters derived from the images captured by the iPPG system exhibited functional characteristics comparable to conventional contact PPG, i.e., maximum heart rate difference was <3 bpm and a significant (p < 0.05) correlation between both measurements were also revealed. Using a method for attenuation of motion artefacts, the heart rate and respiration rate information was successfully assessed from different anatomical locations even in high-intensity physical exercise situations. This study thereby leads to a new avenue for noncontact sensing of vital signs and remote physiological assessment, showing clear and promising applications in clinical triage and sports training. A second study was conducted to remotely assess pulse rate variability (PRV), which has been considered a valuable indicator of autonomic nervous system (ANS) status. The PRV information was obtained using the iPPG setup to appraise the ANS in ten normal subjects. The performance of the iPPG system in accessing PRV was evaluated via comparison with the readings from a contact PPG sensor. Strong correlation and good agreement between these two techniques verify the effectiveness of iPPG in the remote monitoring of PRV, thereby promoting iPPG as a potential alternative to the interpretation of physiological dynamics related to the ANS. The outcomes revealed in the thesis could present the trend of a robust non-contact technique for cardiovascular monitoring and evaluation.
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Crabtree, Vincent P. "Non-invasive vascular assessment using photoplethysmography." Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/7752.
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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.
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John, Gareth W. "Measurement of venous blood flow using photoplethysmography." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/54076/.
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This simple, non-invasive test will reduce the patient numbers requiring the more time-consuming ultrasound examination, by screening out a high proportion of individuals who definitely do not have lower limb DVT. However, further signal processing methods should be investigated to improve the specificity of the test.
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MacConachie, Middleton Paul. "Physiological and clinical implications of photoplethysmography waveforms." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525237.
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Trumpp, Alexander, Johannes Lohr, Daniel Wedekind, Martin Schmidt, Matthias Burghardt, Axel R. Heller, Hagen Malberg, and Sebastian Zaunseder. "Camera-based photoplethysmography in an intraoperative setting." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-234950.
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Background
Camera-based photoplethysmography (cbPPG) is a measurement technique which enables remote vital sign monitoring by using cameras. To obtain valid plethysmograms, proper regions of interest (ROIs) have to be selected in the video data. Most automated selection methods rely on specific spatial or temporal features limiting a broader application. In this work, we present a new method which overcomes those drawbacks and, therefore, allows cbPPG to be applied in an intraoperative environment.
Methods
We recorded 41 patients during surgery using an RGB and a near-infrared (NIR) camera. A Bayesian skin classifier was employed to detect suitable regions, and a level set segmentation approach to define and track ROIs based on spatial homogeneity.
Results
The results show stable and homogeneously illuminated ROIs. We further evaluated their quality with regards to extracted cbPPG signals. The green channel provided the best results where heart rates could be correctly estimated in 95.6% of cases. The NIR channel yielded the highest contribution in compensating false estimations.
Conclusions
The proposed method proved that cbPPG is applicable in intraoperative environments. It can be easily transferred to other settings regardless of which body site is considered.
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Butler, Matthew J. "Motion artefact reduction for reflection-mode photoplethysmography." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/52390/.
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Photoplethysmography (PPG) is a technique that uses light to measure the local changes in blood-volume in subjects (predominantly humans). Multiple useful statistics can be gained from such a measurement; heart-rate and it's variability, blood-oxygen saturation and even an estimation of blood pressure, to name but a few. Compared to other measurement techniques, photoplethysmography is favourable as it is both non-invasive, since nothing physical penetrates the subjects skin, and safe, as the subject is galvanically isolated from the test equipment (additional benefits also exist). Motion artefacts (errors in the measured signal caused by physical movement) are the largest source of error when photoplethysmographic measurements are made, and with the majority of applications involving some form of movement, a motion-tolerant PPG extraction technique would allow for more precise recordings/research/diagnosis etc. This thesis presents the development of an improved photoplethysmography technique that has increased resilience to motion. The developed technique uses multiple PPG measurements at different locations to reconstruct a single PPG signal. It is shown that despite the signals being taken in close proximity to each other (less than 3 cm separation between the farthest elements), the variation in the signals gives sufficient redundancy to extract the uncorrupted PPG to a much higher accuracy using Independent Component Analysis, achieving in the worst case, a 78% reduction in the calculated artefact presence (using quality calculating functions, also presented). As the vast majority of existing PPG systems use a single sensing element, it is hypothesised that such systems cannot be used to accurately and continuously detect the PPG for most motion types and severities. A working prototype of the developed system is demonstrated and directly compared to a single-channel system, showing its effectiveness.
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Allen, John. "Measurement and analysis of multi-site photoplethysmographic pulse waveforms in health and arterial disease." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247830.
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Zaunseder, Sebastian, Alexander Trumpp, Hannes Ernst, Michael Förster, and Hagen Malberg. "Spatio-temporal analysis of blood perfusion by imaging photoplethysmography." SPIE, 2018. https://tud.qucosa.de/id/qucosa%3A35157.
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Imaging photoplethysmography (iPPG) has attracted much attention over the last years. The vast majority of works focuses on methods to reliably extract the heart rate from videos. Only a few works addressed iPPGs ability to exploit spatio-temporal perfusion pattern to derive further diagnostic statements.
This work directs at the spatio-temporal analysis of blood perfusion from videos. We present a novel algorithm that bases on the two-dimensional representation of the blood pulsation (perfusion map). The basic idea behind the proposed algorithm consists of a pairwise estimation of time delays between photoplethysmographic signals of spatially separated regions. The probabilistic approach yields a parameter denoted as perfusion speed. We compare the perfusion speed versus two parameters, which assess the strength of blood pulsation (perfusion strength and signal to noise ratio).
Preliminary results using video data with different physiological stimuli (cold pressure test, cold face test) show that all measures are in fluenced by those stimuli (some of them with statistical certainty). The perfusion speed turned out to be more sensitive than the other measures in some cases. However, our results also show that the intraindividual stability and interindividual comparability of all used measures remain critical points.
This work proves the general feasibility of employing the perfusion speed as novel iPPG quantity. Future studies will address open points like the handling of ballistocardiographic effects and will try to deepen the understanding of the predominant physiological mechanisms and their relation to the algorithmic performance.
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Aniagyei-Mensah, Gideon. "Noninvasive Detection of Central Venous Waveform Using Photoplethysmography." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30711.
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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.
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Ravindranathan, Devi. "Photoplethysmography for the evaluation of diabetic autonomic neuropathy." Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54981/.
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The aim of this study was to determine if photoplethysmography (PPG) could be used to analyse the foot microvascular changes caused by diabetic autonomic neuropathy. The digital PPG signals were collected from 37 healthy volunteers (Group I), 35 diabetic patients (Group II), and 38 diabetic patients with sensory neuropathy (Group III) and analysed using MAT LAB. Prominent spectral peaks with sidebands were obtained at both the high frequency (HF) and the low frequency (LF) end of the Fourier spectrum of these PPG signals. Previous studies of microcirculation have shown that both are sympathetically and parasympathetically mediated and hence are a good measure of the autonomic activity. In the HF analysis, the heart rate (HR) response from 13 participants in Group III was severely reduced and significantly different from the responses obtained from the other two groups. However the responses from remaining 25 participants had similar characteristics to those of Group II. Hence the HF analyses failed to both statistically and objectively differentiate between the diabetics with and without neuropathy. The spectral density for the frequency bandwidth of 3-20 cpm was significantly reduced in the neuropathic group, compared to the other two groups. A Statistically significant difference was observed in the spectral densities calculated from Group II and III, though no difference could be established between Groups I and III. The LF analysis of this bandwidth differentiated between Groups II and III with a sensitivity of 84% and specificity of 61%. Activities at the LF end of the spectrum mostly represent the sympathetic control as opposed to the HR variability that is mostly a measure of the parasympathetic control. These results suggest that sympathetic dysfunction possibly precedes parasympathetic dysfunction and that PPG can assess the changes in the skin microcirculation due to sympathetic damage with moderate success.
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Soleimani, Vahid. "Remote depth-based photoplethysmography in pulmonary function testing." Thesis, University of Bristol, 2018. http://hdl.handle.net/1983/f6a6f7b6-943f-43f7-b684-1612161aee1a.
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This thesis introduces several novel, noninvasive lung function assessment approaches in which we incorporate computer vision techniques to remotely compute standard clinical Pulmonary Function Testing (PFT) measures. Using a single depth sensor, a dynamic 3-D model of a subject's chest is reconstructed and used to generate chest volume-time data by estimating the chest volume variation throughout a sequence. Following computation of multiple keypoints and calibration of volume-time data to present real volume of exchanged air, 7 Forced Vital Capacity (FVC) measures and 4 Slow Vital Capacity (SVC) measures are computed. Evaluation on a dataset of 85 patients (529 sequences), attending a respiratory outpatient service for spirometry, shows a high correlation between the proposed depth-based PFT measures and the measures from a spirometer. Trunk motion during PFT affects the accuracy of these results, so the natural reaction of the subject's body to maximal inhalation and exhalation, must be decoupled from the chest-surface breathing motion. We present an automatic, open source data acquisition and calibration pipeline in which two opposing depth sensors are calibrated and used to reconstruct a well-defined dynamic 3-D model of the trunk during PFT performance. Our proposed method is able to reconstruct dynamic 3-D models with accurate temporal frame synchronisation and spatial registration. Then, we propose a whole body depth-based photoplethysmography (dPPG) approach which allows subjects to perform PFT, as in routine spirometry, without restraining their natural trunk reactions. By decoupling the trunk movement and the chest-surface respiratory motion, dPPG obtains more accurate respiratory volume-time data which improves the accuracy of the estimated PFT measures. A dataset spanning 35 subjects (298 sequences) was collected and used to illustrate the superiority of the proposed dPPG method by comparing its measures to those provided by a spirometer and the single Kinect approach. Although dPPG is able to improve the PFT measures accuracy to a significant extent, it is not able to filter complex trunk motions, particularly at the deep forced inhalation-exhalation stage. To effectively correct trunk motion artifacts further, we propose an active trunk shape modelling approach by which the respiratory volume-time data is computed by performing principal component analysis on temporal 3-D geometrical features, extracted from the chest and posterior shape models in R3 space. We validate the method's accuracy at the signal level by computing several comparative metrics between the depth-based and spirometer volume-time data. Evaluating on the dPPG PFT dataset (300 PFT sequences), our trunk shape modelling approach outperforms the single Kinect and dPPG methods.
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Patterson, James. "A photoplethysmography system optimised for pervasive cardiac monitoring." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11110.
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Photoplethysmography is a non-invasive sensing technique which infers instantaneous cardiac function from an optical measurement of blood vessels. This thesis presents a photoplethysmography based sensor system that has been developed speci fically for the requirements of a pervasive healthcare monitoring system. Continuous monitoring of patients requires both the size and power consumption of the chosen sensor solution to be minimised to ensure the patients will be willing to use the device. Pervasive sensing also requires that the device be scalable for manufacturing in high volume at a build cost that healthcare providers are willing to accept. System level choice of both electronic circuits and signal processing techniques are based on their sensitivity to cardiac biosignals, robustness against noise inducing artefacts and simplicity of implementation. Numerical analysis is used to justify the implementation of a technique in hardware. Circuit prototyping and experimental data collection is used to validate a technique's application. The entire signal chain operates in the discrete-time domain which allows all of the signal processing to be implemented in firmware on an embedded processor which minimised the number of discrete components while optimising the trade-off between power and bandwidth in the analogue front-end. Synchronisation of the optical illumination and detection modules enables high dynamic range rejection of both AC and DC independent light sources without compromising the biosignal. Signal delineation is used to reduce the required communication bandwidth as it preserves both amplitude and temporal resolution of the non-stationary photoplethysmography signals allowing more complicated analytical techniques to be performed at the other end of communication channel. The complete sensing system is implemented on a single PCB using only commercial-off -the-shelf components and consumes less than 7.5mW of power. The sensor platform is validated by the successful capture of physiological data in a harsh optical sensing environment.
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Chatterjee, Subhasri. "Monte Carlo investigation of light-tissue interaction in photoplethysmography." Thesis, City, University of London, 2018. http://openaccess.city.ac.uk/21266/.
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Photoplethysmography (PPG) is a non-invasive photometric technique which measures changes in the volume of blood in the biological tissue. PPG is well-known for its application in pulse oximetry used for the continuous monitoring of arterial blood oxygen saturation (SpO2). Over the past decade, there has been a plethora of research in the field of PPG, with potential applications beyond pulse oximetry and heart rate monitoring. Such applications explore the utilisation of PPG for the assessment of various bio-markers relating to vascular mechanics, haemodynamics and many others. With the growing research interest in the field of PPG, a comprehensive understanding of the light-tissue interaction-based working principle underlying the technique is essential. This thesis is focussed on the investigation of the fundamental light-tissue interactions in PPG using the Monte Carlo method. Tissue models have been developed in this thesis which were characterised by the optical properties (e.g., wavelength- dependent coefficients of scattering and absorption etc.), the anatomical features (e.g., stratification and dimension of tissue layers and sublayers etc.), and the physiological parameters (water and blood content in tissue layers etc.). The Monte Carlo strategy was verified, and was initially implemented to model the light propagation through a monolayer perfused dermal tissue volume in a reflective mode PPG at the red and near-infrared wavelengths, usually used in pulse oximetry. Results illustrated the distribution of the scattering-absorption interaction events, and quantified the optical pathlength, penetration depth and detected reflectance with the variable sensor geometry (i.e., source-detector separation) and physiological states (i.e., the volume of blood and oxygen saturation) of the tissue. The monolayer model was also employed to produce the plot resembling the 'calibration curve' used in pulse oximetry. With the knowledge gained from the monolayer-model study, a similar investigation was performed on a heterogeneous tissue structure of a human finger which was executed in both reflective and transmissive geometrical settings. The calibration curves produced from the detected reflectance and transmittance exhibited a high correlation. The absorbances of red and near-infrared light by individual layers of the finger were quantified at systole and diastole. To the relative absorbance, the contributions of dermis and bone were the maximum and the minimum, respectively. The dependence of the optical pathlength on the source-detector separation and the operating wavelength was quantified by the Differential Pathlength Factor (DPF), which was assessed for the reflective mode PPG by simulating light propagation through a human forearm tissue volume. The DPF values were used in experimentally obtained PPG signal in order to determine the time-change in the concentration of oxyhaemoglobin and deoxyhaemoglobin. Cross-talk and absolute errors were calculated between the simulated and approximated DPFs. The results presented in the thesis contribute greatly to the understanding on PPG light-tissue interaction. Such knowledge could also greatly contribute to the development of the new generation PPG sensors for various applications.
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Abay, Tomas. "Reflectance photoplethysmography for non-invasive monitoring of tissue perfusion." Thesis, City, University of London, 2016. http://openaccess.city.ac.uk/16923/.
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Monitoring blood perfusion and oxygenation changes is of vital importance and for this reason many different techniques have been developed over the decades. Photoplethysmography (PPG) is an optical technique that measures blood volume variations in vascular tissue and it is well known for its utilisation in pulse oximetry for the estimation of arterial blood oxygen saturation (SpO2). In pulse oximetry, mainly the pulsatile component of the signal (AC PPG) is used while the continuous DC component is mostly excluded. Near Infrared Spectroscopy (NIRS) is another optical technique that measures changes in the concentration of oxygenated (ΔHbO2), deoxygenated (ΔHHb), and total haemoglobin (ΔtHb) from the variations in light attenuations at different wavelengths. The main motivation of this research is to explore the capability of Photoplethysmography in assessing tissue perfusion and oxygenation similarly as NIRS. The hypothesis underlining this research is that the DC component of the PPG signal contains information on the overall absorbed light and this part of the PPG signal, acquired at least two wavelengths, may be used to obtain ΔHbO2, ΔHHb, and ΔtHb as performed in NIRS. Therefore, DC PPG attenuations may be related to haemoglobin concentrations by the modified Beer-Lambert law (MBLL). In order to investigate this, novel reflectance, custom-made PPG sensors and measurement systems, including advanced signal processing algorithms, have been developed for the acquisition and analysis of raw PPG signals (AC + DC) from different anatomical locations. Three in vivo studies on healthy volunteers were carried out in order to investigate if ΔHbO2, ΔHHb, and ΔtHb estimated from PPG could indicate changes in blood perfusion and oxygenation. The studies consisted of vascular occlusions on the forearm, negative bed tilting, and whole body cold exposure. Raw PPG signals were acquired from different locations such as the forearm, fingers, and forehead, whereas simultaneous NIRS signals were used as a reference. The results showed that ΔHbO2, ΔHHb, and ΔtHb could be effectively estimated from PPG signals. These parameters indicated the changes in blood volumes and/or oxygenation, whereas comparison with NIRS signals showed good levels of correlation and trending. These promising results showed that DC PPG signals could be used to monitor changes in blood perfusion and oxygenation, extending the range of applications of Photoplethysmography.
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Nilsson, Lena. "Respiratory monitoring using reflection mode photoplethysmography : clinical and physiological aspects /." Linköping : Dept. of Medicine and Care, Univ, 2005. http://www.bibl.liu.se/liupubl/disp/disp2005/med898s.pdf.
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Roald, Nikolai Grov. "Estimation of Vital Signs from Ambient-Light Non-Contact Photoplethysmography." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-20869.
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Abstract In this thesis we have investigated different aspects of non-contact photoplethysmography (PPG) using only ambient lighting. We have investigated how to develop a functional, automatic system based on this to detect heart rate. We have also investigated how to use the concept of non-contact PPG to acquire further relevant medical information from a human subject. Abstract We have investigated different color spaces and found that the Hue and Saturation channels from HSL and HSV color spaces are far superior to the Green channel of the RGB color space, which has previously been used. Especially under circumstances with much noise, are these channels superior and more robust against noise. Abstract The concept of independent component analysis (ICA) has been investigated as a method of improving results. It is found to improve some channels and color spaces, but the best ICA channel does not have better performance than the best non-ICA channel. Abstract The phase of, and difference between, PPG signals has been investigated as a means of acquiring medical information. The phase measurements are highly vulnerable to noise, but there are indications that occlusion can induce a phase difference between different limbs. This difference can be used to calculate change in blood pressure. Abstract We have synchronized ECG and PPG data, and found that there is a high correlation between the two. Pulse transit time (PTT) from the heart to the measurement site can be calculated using this synchronized information. Abstract Further have different motion compensation algorithms and signal processing techniques been investigated with the goal of improving the PPG signal and a programs ability to automatically detect heart rate.
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Qin, Dong. "HAND-ARM VIBRATION EXPOSURE MONITORING WITH SKIN TEMPERATURE AND PHOTOPLETHYSMOGRAPHY." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1492098556166678.
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Botina, Monsalve Deivid. "Remote photoplethysmography measurement and filtering using deep learning based methods." Electronic Thesis or Diss., Bourgogne Franche-Comté, 2022. http://www.theses.fr/2022UBFCK061.
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RPPG est une technique développée pour mesurer le signal du pouls et ensuite estimer les données physiologiques telles que la fréquence cardiaque, la fréquence respiratoire et la variabilité du pouls.En raison des multiples sources de bruit qui détériorent la qualité du signal RPPG, les filtres conventionnels sont couramment utilisés. Cependant, certaines altérations demeurent, alors qu'un œil expérimenté peut facilement les identifier. Dans la première partie de cette thèse, nous proposons le réseau LSTMDF (Long Short-Term Memory Deep-Filter) pour réaliser le filtrage du signal RPPG. Nous utilisons différents protocoles pour analyser les performances de la méthode. Nous démontrons comment le réseau peut être entraîné efficacement avec un nombre limité de signaux. Notre étude démontre expérimentalement la supériorité du filtre basé sur le LSTM par rapport aux filtres conventionnels. Le réseau est ainsi peu sensible rapport signal/bruit moyen des signaux RPPG.Les approches basées sur les réseaux convolutifs tels que les 3DCNN ont récemment surpassé les méthodes manuelles traditionnelles dans la tâche de mesure du RPPG. Cependant, il est connu que les grands modèles 3DCNN ont des coûts de calcul élevés et peuvent être inadaptés aux applications en temps réel. Comme deuxième contribution de cette thèse, nous proposons une étude d'une architecture 3DCNN, trouvant le meilleur compromis entre la précision de la mesure du pouls et le temps d'inférence. Nous utilisons une étude d'ablation où nous diminuons la taille de l'entrée, proposons une fonction de perte personnalisée, et évaluons l'impact de différents espaces de couleur d'entrée. Le résultat est le RPPG en temps réel (RTRPPG), un outil de mesure du RPPG de bout en bout qui peut être utilisé sur GPU et CPU. Nous avons également proposé une méthode d'augmentation des données qui vise à améliorer les performances des réseaux d'apprentissage profond lorsque la base de données présente des caractéristiques spécifiques (par exemple, les mouvements de type fitness) et lorsque les données disponibles sont peu nombreuses<br>RPPG is a technique developed to measure the blood volume pulse signal and then estimate physiological data such as pulse rate, breathing rate, and pulse rate variability.Due to the multiple sources of noise that deteriorate the quality of the RPPG signal, conventional filters are commonly used. However, some alterations remain, but interestingly, an experienced eye can easily identify them. In the first part of this thesis, we propose the Long Short-Term Memory Deep-Filter (LSTMDF) network in the RPPG filtering task. We use different protocols to analyze the performance of the method. We demonstrate how the network can be efficiently trained with a few signals. Our study demonstrates experimentally the superiority of the LSTM-based filter compared with conventional filters. We found a network sensitivity related to the average signal-to-noise ratio on the RPPG signals.Approaches based on convolutional networks such as 3DCNNs have recently outperformed traditional hand-crafted methods in the RPPG measurement task. However, it is well known that large 3DCNN models have high computational costs and may be unsuitable for real-time applications. As the second contribution of this thesis, we propose a study of a 3DCNN architecture, finding the best compromise between pulse rate measurement precision and inference time. We use an ablation study where we decrease the input size, propose a custom loss function, and evaluate the impact of different input color spaces. The result is the Real-Time RPPG (RTRPPG), an end-to-end RPPG measurement framework that can be used in GPU and CPU. We also proposed a data augmentation method that aims to improve the performance of deep learning networks when the database has specific characteristics (e.g., fitness movement) and when there is not enough data available
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Almond, Nicholas Edward. "A fibre-optic laser Doppler flowmeter system and its application to the study of the skin microcirculation in humans." Thesis, Queen Mary, University of London, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389908.
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Wenngren, Wilhelm Sven Ingemar. "Local pulse wave velocity detection over an arterial segment using photoplethysmography." University of British Columbia, 2017. http://hdl.handle.net/2429/63867.
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The goal of this thesis is to determine the validity of using photoplethysmography (the detection of changes of blood volume using light) to measure pulse wave velocity as part of a continuous and non-disruptive blood pressure monitor. There has been a limited advancement over the years in technologies to monitor personal blood pressure, which have rendered at-home monitoring still relatively intrusive. The main method for at-home blood pressure monitoring is the use of an inflating cuff that obstructs the artery to detect pressure. This system suffers from inherit drawbacks, such as limitations on recording accuracy if insufficient time has passed between samples and the restrictive nature of the cuff which can induce pain on a user. An alternative device that can monitor continuously would thus benefit people who are sensitive or need 24-hour monitoring. Ideally this would be a system that can be worn without discomfort and does not interfere with the user in any way. The ideal device would also allow continuous blood pressure monitoring throughout the cardiac cycle, independent of the level of physical activity of the user. Furthermore, this type of device would allow athletes to measure blood pressure during activity.
To this end, a model is developed to describe blood pressure by measuring the arterial diameter on the radial artery and the pulse wave velocity (PWV) through it. Research suggests that these two metrics, along with the elasticity of an artery, can be used as a means to measure blood pressure non-invasively. This thesis focuses on the measurement of pulse wave velocity. The system design, including the hardware, is covered. The analysis techniques used to obtain raw signals, as well as the methods used to determine the PWV, will be discussed. The measurement location is described in detail. The results are shown to be comparable to values found in literature. However, due to lack of comparable measurement techniques, no direct comparisons between methods could be performed.<br>Applied Science, Faculty of<br>Engineering, School of (Okanagan)<br>Graduate
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Shaltis, Phillip Andrew. "A wearable blood pressure sensor using oscillometric photoplethysmography and micro accelerometers." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40363.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.<br>Includes bibliographical references (leaves 119-124).<br>Monitoring arterial blood pressure (ABP) with a sensor virtually imperceptible to the wearer, for continuous periods of weeks, months, or years, could prove revolutionary in the diagnosis and treatment of chronic hypertension and heart failure, as well as a monitoring tool for convalescing individuals, and individuals in hazardous duty (such as firefighters or soldiers). To this end, a miniaturizable, non-invasive blood pressure sensor is designed and validated. A solid, coin-sized cuff-less photoplethysmography (PPG) sensor worn over a palpable artery is utilized to measure arterial blood pressure. Measurements are obtained through a modified oscillometric technique which eliminates the need for a high pressure cuff and instead, takes advantage of natural hydrostatic pressure changes caused by raising and lowering the subject's arm. In this work, the principle of hydrostatic oscillometry is first detailed. To better understand the internal mechanisms of pressure propagation within the tissue, a comprehensive non-linear finite element model of the finger base is constructed and validated using a combination of magnetic resonance imaging and experimental tissue stiffness measurements.<br>(cont.) A prototype finger blood pressure monitor is designed and constructed in combination with a novel accelerometer-based height sensor. The 95% confidence interval for a Bland-Altman comparison between the proposed sensor's mean arterial pressure (MAP) measurements and the simultaneous Finapres MAP measurements is [+919, -283] Pa ([+6.91, -9.04] mmHg). The percent difference between the two methods is shown to be 3.0%. A method for continuous MAP measurements utilizing the sensor system is proposed and is shown to be capable of providing reliable measurements for several minutes.<br>by Phillip Andrew Shaltis.<br>Ph.D.
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Njoum, H. "Investigations of photoplethysmography in the assessment of haemodynamics, vascular mechanics and haemorheology." Thesis, City, University of London, 2017. http://openaccess.city.ac.uk/17837/.
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Real‐time cardiovascular assessment is vital for monitoring patients at an early stage of cardiovascular diseases (CVDs), at risk of reoccurrence of heart attacks and strokes and during pharmacological and non‐pharmacological treatments. Blood Pressure (BP), Arterial Stiffness (AS) and Blood Viscosity (BV) are three essential parameters that can provide a reliable assessment of hypertension, atherosclerosis, and hyperviscosity associated with the development and progression of cardiovascular pathologies to complex stages. The currently available methods designed for evaluation of such parameters incur limitations and challenges that stand as an obstacle to the development of non‐invasive, portable and reliable all‐in‐one device intended for personal use. This project engaged in novel fundamental and rigorous in vivo and in vitro investigations in an effort to shed more light on the photoplethysmographic signals (AC and DC) during induced changes of BP, AS, and BV. The underlying hypothesis is to show for the first time that Photoplethysmography (PPG) has the potential to non‐invasively assess, in a qualifying and quantifying manner, the above parameters. Positives outcomes from such approach will establish the potential of the PPG as a preferential monitoring (screening and possible diagnosis) technique for the assessment of CVDs. Novel miniature PPG sensors were developed along with a state of the art PPG processing unit, a data acquisition system and a customised manuscript for offline signal analyses. ECG and temperature processing systems were also designed and developed for use in the in vivo investigations. State of the art in vitro experimental rig was developed to mimic the human circulation under a wide range of flow conditions. A pilot volunteer investigation highlighted the effect of a cold pressor test in one hand on the PPG signals from both hands. The results indicated that there are changes in flow regulation mechanisms and hemodynamics besides the expected vasoconstriction effects of local cooling. These findings led to the controlled in vitro experiments. The in vitro investigations were completed in four stages where the potential of the PPG to provide a measure of blood pressure values, volume elastic modulus (Ev) and to detect fluid viscosity and haemorheological changes. Results from the in vitro investigations highlighted that Adjusted Pulse Volume (APV) was found to be the optimum method for measuring BP values using Red (R) and Infrared (IR) wavelengths as validated under a range of BP values simulating hypotensive to hypertensive scenarios. The correlation was significant with Rsquare ranging between 0.96 and 0.99 for different arterial models and circulating fluids. Moreover, a proposed mathematical derivation allowed the PPG to provide a direct measure of AS using Ev. The method showed strong agreement with the gold standard measurement of material testings, the Instron device, with a percent error of 0.26% and 1.9% for different arterial models. Furthermore, the PPG signals also responded to changes in rheological characteristics in relation to fluid viscosities, the presence of the red blood cells, changes in shear rates and blood clotting. These results strongly suggest that PPG has the potential to be used as a non‐invasive and continuous method for the assessment of cardiovascular disease markers such as blood pressure, arterial stiffness and blood viscosity.
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Cherif, Safa. "Effective signal processing methods for robust respiratory rate estimation from photoplethysmography signal." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2018. http://www.theses.fr/2018IMTA0094/document.
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Le photopléthysmogramme (PPG) est un signal optique acquis à partir de l’oxymètre de pouls, dont l’usage principal consiste à mesurer la saturation en oxygène. Avec le développement des technologies portables, il est devenu la technique de base pour la surveillance de l’activité cardio-respiratoire des patients et la détection des anomalies. En dépit de sa simplicité d'utilisation, le déploiement de cette technique reste encore limité pour deux principales raisons : 1. L’extrême sensibilité du signal aux distorsions. 2. La non-reproductibilité entre les sujets et pour les mêmes sujets, en raison de l'âge et des conditions de santé. L’objectif de cette thèse est le développement de méthodes robustes et universelles afin d’avoir une estimation précise de la fréquence respiratoire (FR) indépendamment de la variabilité intra et interindividuelle du PPG. Plusieurs contributions originales en traitement statistiques du signal PPG sont proposées. En premier lieu, une méthode adaptative de détection des artefacts basée sur la comparaison de modèle a été développée. Des tests par la technique Random Distortion Testing sont introduits pour détecter les pulses de PPG avec des artefacts. En deuxième lieu, une analyse de plusieurs méthodes spectrales d’estimation de la FR est proposée. Afin de mettre en évidence la robustesse des méthodes proposées face à la variabilité du signal, plusieurs tests ont été effectués sur deux bases de données avec de différentes tranches d'âge et des différents modes respiratoires. En troisième lieu, un indice de qualité respiratoire spectral (SRQI) est conçu dans le but de communiquer au clinicien que les valeurs fiables de la FR avec un certain degré de confiance<br>One promising area of research in clinical routine involves using photoplethysmography (PPG) for monitoring respiratory activities. PPG is an optical signal acquired from oximeters, whose principal use consists in measuring oxygen saturation. Despite its simplicity of use, the deployment of this technique is still limited because of the signal sensitivity to distortions and the non-reproducibility between subjects, but also for the same subject, due to age and health conditions. The main aim of this work is to develop robust and universal methods for estimating accurate respiratory rate regardless of the intra- and inter-individual variability that affects PPG features. For this purpose, firstly, an adaptive artefact detection method based on template matching and decision by Random Distortion Testing is introduced for detecting PPG pulses with artefacts. Secondly, an analysis of several spectral methods for Respiratory Rate (RR) estimation on two different databases, with different age ranges and different respiratory modes, is proposed. Thirdly, a Spectral Respiratory Quality Index (SRQI) is attributed to respiratory rate estimates, in order that the clinician may select only RR values with a large confidence scale. Promising results are found for two different databases
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Chan, Gregory Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Early detection of blood loss using a noninvasive finger photoplethysmographic pulse oximetry waveform." Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2008. http://handle.unsw.edu.au/1959.4/42593.
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Delayed control of haemorrhage or blood loss has been recognised as a major contributor to preventable trauma deaths, but early detection of internal bleeding is difficult due to unreliability of heart rate (HR) and blood pressure (BP) as markers of volume status. This thesis explores a novel method of early blood loss detection using a noninvasive finger photoplethysmographic (PPG) pulse oximetry waveform that is normally utilised in pulse oximeters for estimating arterial oxygen saturation. Graded head-up tilt (n = 13) and blood donation (n = 43) in human volunteers were selected as experimental models of mild to moderate blood loss. From the tilt study, a novel method for automatically detecting left ventricular ejection time (LVET) from the finger PPG waveform has been developed and verified by comparison with the LVET measured from aortic flow velocity. PPG waveform derived LVET (LVETp) and pulse transit time (PTT) were strongly correlated with aortic LVET and pre-ejection period respectively (median r = 0.954 and 0.964) and with the decrease in central blood volume indicated by the sine of the tilt angle (median r = -0.985 and 0.938), outperforming R-R interval (RRI) and BP in detecting mild central hypovolaemia. In the blood donation study, progressive blood loss was characterised by falling LVETp and rising PTT (p < 0.01). A new way of identifying haemorrhagic phases by monitoring changes and trends in LVETp, PTT and RRI has been proposed based on the results from the two studies. The utility of frequency spectrum analysis of PPG waveform variability (PPGV) in characterising blood loss has also been examined. A new technique of PPGV analysis by computing the coherence-weighted cross-spectrum has been proposed. It has been shown that the spectral measures of finger PPGV exhibited significant changes (p < 0.01) with blood donation and were mildly correlated with systemic vascular resistance in intensive care unit patients (r from 0.53 to 0.59, p < 0.0001), therefore may be useful for identification of different haemorrhagic phases. In conclusion, this thesis has established finger PPG waveform as a potentially useful noninvasive tool for early detection of blood loss.
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Rustand, Åsmund. "Ambient-light Photoplethysmography : - How can I tell your pulse from looking at your face?" Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18848.
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This thesis is an attempt to explore certain aspects of the subject called non-contact, ambient-light photoplethysmography, where we hope to reveal benecialproperties the technique may have. We have a clear focus on technical possibilitybut the medical relevance of it is also discussed and conrmed.Conclusions from previous work are exemplied { the ability we have with thismethod to compute an exact heart rate estimate, from the skin surface both onour face and in the palm of our hand, with and without the subject moving duringrecording; the presence of signal uctuations akin to those of breathing. Moreover,that the pulsations are strong enough to enable subdivision into smaller segmentsand a mapping of how the pulse amplitude is distributed among them.Other information is obtained: the phase information contained in the signalis robust enough that not only the average heart rate over some time but also itsshort time variability can be seen with more than a minimum of detail resolution.From a recording where both face and hand is in view, we further substantiate theclaim of phase robustness by estimating the phase delay, i.e. the dierence in bloodpressure wave travel time between forehead and palm.The concept of Independent Component Analysis has been suggested as a way ofimproving the output of the method|a procedure we investigate and nd limitedsupport for. Other, more simplistic signal processing approaches are found to havepositive traits in achieving overall signal clarity.
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Mateus, Jaime (Pereira de Mateus Silva). "Photoplethysmography for non-invasive measurement of bone hemodynamic responses to changes in external pressure." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67174.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 123-135).<br>Adequate blood supply and circulation in bones is required to maintain a healthy skeleton, and inadequate blood perfusion is associated with numerous bone pathologies and a decrease in bone mineral density (BMD). Bone hemodynamics remains poorly understood and loss of BMD is still one of the limiting factors to long duration human spaceflight. Developments in photoplethysmography (PPG) hardware have made it a promising tool for non-invasive bone hemodynamic measurements. The aims of this thesis are to: 1) validate the use of PPG as a tool for non-invasive bone hemodynamic measurements, 2) characterize bone hemodynamic responses to changes in external pressure, and 3) identify the predominant mechanisms regulating bone hemodynamic responses to pressure changes. A new PPG device capable of measuring bone hemodynamic responses was designed and tested. It represents the state-of-the-art in deep-tissue PPG instrumentation. Validation experiments including arterial occlusion, cold exposure, skin occlusion and nitroglycerin exposure were performed. Single-limb pressure chamber experiments were performed over a range of pressures from -50 to +50 mmHg to characterize the responses to changes in external pressure and to identify the predominant control mechanisms. Our results support the use of PPG as a valid tool for measuring bone hemodynamic responses. Bone hemodynamic responses to changes in external pressure have been characterized for the first time. We also present the first report of a myogenic response in bone and show that the myogenic effect is the predominant control mechanism in bone over a wide range of pressure levels. Myogenic-induced vasoconstriction is observed at all negative pressure levels, with increasing vasoconstriction at the more extreme pressure differences. At positive pressures we observed an initial myogenic-induced vasodilation followed by activation of the intramuscular pressure receptors at +30 mmHg which overrides the initial response and causes vasoconstriction at the highest positive pressure. The availability of a new tool for non-invasive bone hemodynamic measurements opens the door to several new research opportunities with clinical, Earth-based as well as human spaceflight applications.<br>by Jaime Mateus.<br>Ph.D.
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Kiehl, Zachary Adam. "Measuring Pulse Rate Variability During Motion Artifact with a Non-Contact, Multi-Imager Photoplethysmography System." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1430403954.
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Dall'Olio, Lorenzo. "Estimation of biological vascular ageing via photoplethysmography: a comparison between statistical learning and deep learning." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21687/.
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This work aims to exploit the biological ageing phenomena which affects human blood vessels. The analysis is performed starting from a database of photoplethysmographic signals acquired through smartphones. The further step involves a preprocessing phase, where the signals are detrended using a central moving average filter, demoduled using the envelope of the analytic signal obtained from the Hilbert transform, denoised using the central moving average filter over the envelope. After the preprocessing we compared two different approaches. The first one regards Statistical Learning, which involves feature extraction and selection through the usage of statistics and machine learning algorithms. This in order to perform a classification supervised task over the chronological age of the individual, which is used as a proxy for healthy/non healthy vascular ageing. The second one regards Deep Learning, which involves the realisation of a convolutional neural network to perform the same task, but avoiding the feature extraction/selection step and so possible bias introduced by such phases. Doing so we obtained comparable outcomes in terms of area under the curve metrics from a 12 layers ResNet convolutional network and a support vector machine using just covariates together with a couple of extracted features, acquiring clues regarding the possible usage of such features as biomarkers for the vascular ageing process. The two mentioned features can be related with increasing arterial stiffness and increasing signal randomness due to ageing.
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Schäck, Tim [Verfasser], Abdelhak M. [Akademischer Betreuer] Zoubir, D. Robert [Akademischer Betreuer] Iskander, and Michael [Akademischer Betreuer] Muma. "Photoplethysmography-Based Biomedical Signal Processing / Tim Schäck ; Abdelhak M. Zoubir, D. Robert Iskander, Michael Muma." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/1176702009/34.
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McGuinness, Abdollahi Zahra. "Intra-operative optical monitoring of bowel tissue viability based on photoplethysmography and laser Doppler flowmetry." Thesis, City University London, 2015. http://openaccess.city.ac.uk/13684/.
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Determination of bowel viability in patients undergoing bowel resection is essential in gastrointestinal surgery. One of the most common operations in gastrointestinal surgery is bowel resection for patients who have different kinds of bowel cancer or any other occlusion in which anastomosis has to be carried out following the removal of an unhealthy segment of the bowel. Monitoring blood flow in abdominal surgery especially intraoperatively would be a valuable tool for prevention of a postoperative anastomosis complication (e.g. anastomotic leak, which is the main complication after colorectal resection). The development of a continuous method for monitoring perfusion of bowel tissue would assist in early detection of inadequate blood supply which then help to reduce the occurrence of an anastomosis complication. Although various monitoring techniques have been proposed to assess intestinal viability intraoperatively, none of these techniques have proved to be reliable enough to replace visual observation. Therefore, to date there is no widely accepted and readily available intraoperative technique to reliably assess the viability of bowel tissue. The aim of this study was to combine the established techniques, laser Doppler flowmetry (LDF) and Photoplethysmography (PPG), into one probe intended for assessment of perfusion in abdominal tissue during bowel resection intraoperatively. In PPG, changes in transmission of light through tissue due to pulsation of small arteries can be monitored whereas in LDF microcirculatory blood cell velocity and flux can be studied. Such a probe could alert the surgeon immediately of any compromise in blood flow so further investigation and, if necessary, therapeutic steps can be applied immediately to prevent severe consequences. Therefore, custom reflectance PPG along with LDF sensor was designed and built in the form of a probe to investigate the changes in blood volume, blood flow and arterial oxygen saturation in patients undergoing bowel resection. The instrumentation was designed successfully and the data was saved for the further analysis. Twenty-four patients undergoing bowel resection were recruited for monitoring of perfusion and blood flow intraoperatively; twenty had undergone laparoscopy and the remainder had a laparotomy operation. Eight different measurements were performed during each trial. The results revealed that the probe could be an indicator of evaluating perfusion and blood flow changes at different stages of the surgery. The results also suggest that laser Doppler is more sensitive to artefact compared to PPG. Differences in amplitude of PPG between different measurements reveal that the sensor does detect changes in blood volume and flow confirming that it has the ability to verify that pulsatile flow is being preferentially preserved at the last step of the resection procedure (at the edges of the anastomosis sites after anastomosis has been constructed).
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Patancheru, Govardhan Reddy. "Wearable Heart Rate Measuring Unit." Thesis, Mittuniversitetet, Avdelningen för elektronikkonstruktion, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-23351.
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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.
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Ramli, Nur Ilyani Binti. "Design and development of a low cost heart best monitor device using finger photoplethysmography technique :|bcircuit design and fabrication of a non-invasive heart beat monitoring device that employs reflectance and transmission mode photoplethysmography using parallel port interface and microcontroller PIC16F84A." Thesis, University of Bradford, 2014. http://hdl.handle.net/10454/7291.
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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.<br>Ministry of Higher Education Malaysia (MOHE) and Universiti Tun Hussein Onn Malaysia (UTHM)
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Shafique, Muhammad. "Investigation of photoplethysmography and arterial blood oxygen saturation during artificially induced peripheral hypoperfusion utilising multimode photometric sensors." Thesis, City University London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531784.
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Ramli, Nur Ilyani Binti. "Design and development of a low cost heart best monitor device using finger photoplethysmography technique : circuit design and fabrication of a non-invasive heart beat monitoring device that employs reflectance and transmission mode photoplethysmography using parallel port interface and microcontroller PIC16F84A." Thesis, University of Bradford, 2014. http://hdl.handle.net/10454/7291.
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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.
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Hilmersson, Anette. "Multisensor Stress Monitoring For Non-Stationary Subjects." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-28340.
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Monitoring stress in real-time, in a non-laboratory environment can be benecial in several applications. One of these, which have been the motivation for this thesis, is to to perform this measurement during Attention decit hyperactivity disorder (ADHD) diagnosis. Monitoring several physiological responses to internal or external stimuli in a single soft-real-time system is nota solution widely used in an application like this. The thesis starts by studying several stress related responses in detail. Sensors for all of the responses are not implemented nor is it possible toimplement in to the desired system. After the study is was decided to implement two measurement modules. The first a Photo-plethysmogrophy (PPG) measurement module to measure heart rate and also estimate breathing. This module is prepared for estimating arterial blood oxygen levels but the calculation or verification have not been done. The second is Skin Conductance (SC) measurement module and in to both ofthese add a temperature sensor to measure the temperature of the skin. Time constraints limit the SC module to only be presented in theory. The PPG module on the other hand have been realisedin a prototype. This prototype performs the measurement in transmissive mode on the left earlobe, which leaves the hands free and it does not affect the hearing on that ear. The prototype giveout acceptable signal quality when good contact with the measurement site is achieved. The signalinterpretation, such as performing the signal analysis to count the beats per minute, is outside thescope of this thesis and will therefore not be presented but the signals can be seen in figures.<br>Att mäta stress i realtid i verkliga situationer kan vara fördelaktigt för flera applikationer. Det som har legat som grund för denna uppsats är att kunna mäta stress under ADHD diagnostisering. Genom att kombinera de vanliga testerna med stressnivåer hos patienten hoppas man kunna utveckla nya metoder för diagnostisering. Att mäta fera parametrar samtidigt i realtid är inte något ofta utförs idag. För att komma igång har fera kroppsliga funktioner som påverkas på olika sätt av stress studerats. Alla dessa funktioner kan inte inkluderas i det system som önskas konstrueras antingen på grund av systemets karaktär eller på grund tidsbrist. Efter att undersökningen var klar beslutades det att konstruera två moduler. Den första använder en mätteknik som kallas PPG och används för att mäta hjärtfrekvens, även andningsfrekvensen estimeras och modulen är förberedd för att estimera blodsyre nivåa men signalbehandling och validering för detta är inte gjord. Den andra modulen mäter resistans i huden. I dessa moduler lades även till en temperatur sensor för att mäta hudtemperaturen. Tidsbrist har gjort att endast en av dem två modulerna kunnat realiserats. Den som realiserat är PPG modulen och modulen för hudresistans presenteras endast teoretiskt. PPG modulen genomför matningen med en transmissiv teknik på vänster öra och ger ut en acceptabel signal kvalité om sensorn får bra kontakt. Arbetet är avgränsat och inkluderar inte signalanalysen av signalen däremot visualiseras signalen i figurer.
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KUO, CHUN-HUNG, and 郭俊宏. "Blood Pressure Estimation Using Photoplethysmography." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/3qt8p6.
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碩士<br>國立中正大學<br>電機工程研究所<br>104<br>In this study, we proposed a blood pressure estimation system. We estimated systolic and diastolic blood pressure by using Photoplethysmography (PPG).
The database collected by the projects supported by the grants from Ministry of Science and Technology (NSC 102-2410-H-194-022) to Chia-Ying Weng. The system contained five parts, namely data classification, physiological signal acquisition, feature points detection, feature extraction, and blood pressure estimation. In the data classification part, data were divided into four categories including healthy students, hypertensive patients with medication, and hypertensive patients without medication and people but might have other diseases with normal blood pressure. Each of the categories had four stages: baseline, recall, description, and recovery. In the physiological signal acquisition part, we acquired physiological signal and detected important feature points from different categories of signals. And then totally 65 features, including the features of time, amplitude, waveform, HRV, gender, and age were calculated. In the estimation part, we used the back-propagation neural network (BPNN). The parameters were empirically set as follows: 2 hidden layers, transfer function of log-sigmoid, and 130 neurons in the hidden layer.
The results showed that the error in each case was always limited within 3 mmHg by using all-train-all-test validation. When the signals were acquired from healthy students and people with normal blood pressure but might have other diseases and only the more stable three stages, including baseline, recall, and recovery were considered the errors in systolic and diastolic blood pressure were 8.598 mmHg and 6.89 mmHg, respectively, by using leave one out cross-validation. On the other hand, when the data contained the same two categories mentioned above and only the baseline stage was considered, the systolic and diastolic blood pressure errors were reduced to 7.746 mmHg, 6.81 mmHg, respectively.
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Schäck, Tim. "Photoplethysmography-Based Biomedical Signal Processing." Phd thesis, 2019. https://tuprints.ulb.tu-darmstadt.de/8411/1/2019-01-24_Sch%C3%A4ck_Tim.pdf.
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In this dissertation, photoplethysmography-based biomedical signal processing methods are developed and analyzed. The developed methods solve problems concerning the estimation of the heart rate during physical activity and the monitoring of cardiovascular health. For the estimation of heart rate during physical activity, two methods are presented that are very accurate in estimating the instantaneous heart rate at the wrist and, at the same time, are computationally efficient so that they can easily be integrated into wearables. In the context of cardiovascular health monitoring, a method for the detection of atrial fibrillation using the video camera of a smartphone is proposed that achieves a high detection rate of atrial fibrillation (AF) on a clinical pre-study data set. Further monitoring of cardiovascular parameters includes the estimation of blood pressure (BP), pulse wave velocity (PWV), and vascular age index (VAI), for which an approach is presented that requires only a single photoplethysmographic (PPG) signal.
Heart rate estimation during physical activity using PPG signals constitutes an important research focus of this thesis. In this work, two computationally efficient algorithms are presented that estimate the heart rate from two PPG signals using a three axis accelerometer. In the first approach, adaptive filters are applied to estimate motion artifacts that severely deteriorate the signal quality. The non-stationary relationship between the measured acceleration signals and the artifacts is modeled as a linear system. The outputs of the adaptive filters are combined to further enhance the signal quality and a constrained heart rate tracker follows the most probable high energy continuous line in the spectral domain. The second approach is modest in computational complexity and very fast in execution compared to existing approaches. It combines correlation-based fundamental frequency indicating functions and spectral combination to enhance the correlated useful signal and suppress uncorrelated noise. Additional harmonic noise damping further reduces the impact of strong motion artifacts and a spectral tracking procedure uses a linear least squares prediction. Both approaches are modest in computational complexity and especially the second approach is very fast in execution, as it is shown on a widely used benchmark data set and compared to state-of-the-art methods.
The second research focus and a further major contribution of this thesis lies in the monitoring of the cardiovascular health with a single PPG signal. Two methods are presented, one for detection of AF and one for the estimation of BP, PWV, and VAI. The first method is able to detect AF based on a smartphone filming the finger placed on the video camera. The algorithm transforms the video into a PPG signal and extracts features which are then used to discriminate between AF and normal sinus rhythm (NSR). Perfect detection of AF is already achieved on a data set of 326 measurements (including 20 with AF) that were taken at a clinical pre-study using an appropriate pair of features whereby a decision is formed through a simple linear decision equation. The second method aims at estimating cardiovascular parameters from a single PPG signal without the conventional use of an additional electrocardiogram (ECG). The proposed method extracts a large number of features from the PPG signal and its first and second order difference series, and reconstructs missing features by the use of matrix completion. The estimation of cardiovascular parameters is based on a nonlinear support vector regression (SVR) estimator and compared to single channel PPG based estimators using a linear regression model and a pulse arrival time (PAT) based method. If the training data set contains the person for whom the cardiovascular parameters are to be determined, the proposed method can provide an accurate estimate without further calibration.
All proposed algorithms are applied to real data that we have either recorded ourselves in our biomedical laboratory, that have been recorded by a clinical research partner, or that are freely available as benchmark data sets.
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Huang, Fu-Hsuan, and 黃福塤. "Analysis of Reflectance Photoplethysmography Sensor." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/18410700934549786797.
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碩士<br>中原大學<br>醫學工程研究所<br>97<br>Photoplethysmography is an easy method for measuring blood volume change in tissue. It's detect signals include: the vasoconstriction low frequency signal and the pulse's high frequency signal.Since the transmission type of measurement is limited to only a few specific positions that have a short pathlength.The reflectance type can be more convenient to apply on most part of body surface.This study is to analyze the factors that determine the quality of light reflectance signal. These factors include: the emitter-detector distance, wavelength, light intensity, and optical properties of skin tissue.
In this study, light emitting diodes (LEDs) with four visible wavelengths were used as the light emitters, and a phototransistor was used as the light detector. A micro translation stage can adjust the emitter-detector distance from 2 mm to 15 mm. The reflective photoplethysmograph signals were measure on finger, forearm, and forehead.
The optimal emitter-detector distance should be chosen to have a large dynamic range for low frequency drifting without signal saturation and a high perfusion index (AC-to-DC ratio).Among the four wavelengths, the yellowish green (571nm) light with 3.2 mm of emitter-detection distance is most suitable for obtaining a steady and reliable reflective photoplethysmograph signal.
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HUANG, YEN-TING, and 黃彥庭. "Attention Level Recognition Based on Photoplethysmography." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/u8sk88.
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碩士<br>國立中正大學<br>電機工程研究所<br>104<br>In this research, we proposed an attention recognition system based on physiological signals. We used Photoplethysmography (PPG) to recognize different attention level so three attention level combination settings were analyzed. The first combination included attention, minor attention, and non-attention. The second combination included two levels, one was non-attention and the other was the combination of attention and minor attention. The third combination contained attention and non-attention levels.
In our study, the attention recognition system was composed of data acquisition, features calculation, features normalization, features selection, and classification. First, in the data acquisition part, 10 subjects, including 8 males and 2 females participated in this study. In order to induce attention, we used visual test called the Continuous Performance Test (CPT), and recorded the participants’ responses. Second, in the data acquisition part, we calculated 4 categories of features from every 60 seconds of PPG signals segments. In order to reduce the influence of individual difference, we calculated the difference features from the four categories of features from the induced and baseline PPG signals. Third, we normalized our feature set to the same level. Fourth, in order to increase the recognition rate, we used Genetic Algorithm (GA) to select the most effective feature set. Finally, we used BPNN and SVM to classify attention by using leave-one-out cross validation. The problem of unequal sample numbers in each class was discussed. By using BPNN, the accuracy of the first combination achieved 45%. The accuracy of the second combination achieved 89%. The accuracy of the third combination achieved 89%. By using SVM, the accuracy of the first combination achieved 45.6%. The accuracy of the second combination achieved 74.07%. The accuracy of the third combination achieved 67.5%. With feature selection using GA, the accuracies of the three combination rose to 45.6%, 80.7% and 80% respectively. The results demonstrated the capability of using individual differences features and GA feature selector to promote the recognition rate.
As on the android platform, we implemented a real-time attention recognition system base on PPG. This system included a Pulse Sensor, an Arduino Nano micro-controller and transferred to the cellphone by OTG. The system can distinguish between attention and non-attention, with an accuracy of 83.33%.
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Jan, Hao-Yu, and 詹皓羽. "Applications of Photoplethysmography for Cardiovascular diagnosis." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/99t2x8.
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碩士<br>中原大學<br>電機工程研究所<br>92<br>The aim of this study is to <a href="http://www.ntsearch.com/search.php?q=design&v=56">design</a> and develop a simultaneous measuring SaO2 and ECG system based on double wavelength-infrared and red light optic system and simple physiological electric signal detection device.
This system could measure real-time SaO2 signal and ECG signal simultaneously. When combine with SaO2 signal and ECG signal, we can go deep to analyze cardiovascular parameters.
In this study, we use three channel signal-- Infrared PPG, Red PPG and ECG signals to obtain every subject’s Heart Rate (HR), SaO2,Pulse Wave velocity (PWV), vascular stiffness index (SI), vascular reflection index (RI). Through HR, PWV, SI and RI parameter, we can estimate cardiovascular conditions. With SaO2 parameter, we can estimate cardiopulmonary function. The study also discussed the relationships between age and cardiovascular physiology functions based on statistics.
This paper brings up the total solution of integrating optical measurements with electrical analysis to achieve the goal of <a href="http://www.ntsearch.com/search.php?q=home&v=56">home</a> cardiovascular function monitoring. The development of this system has great potential in <a href="http://www.ntsearch.com/search.php?q=home&v=56">home</a> care.
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HUANG, HSIAO-YU, and 黃筱玉. "Optical characteristics and structural analysis of Photoplethysmography." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/18363078547815253675.
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碩士<br>聖約翰科技大學<br>電子工程系碩士班<br>104<br>Photoplethysmogram (PPG) using light illuminate into the skin, light will be through the biological tissues, the vascular caliber changes caused by heart beats, after irradiation of light by refraction, to produce a continuous variation waveform signal received by the receiver, can achieve non-invasive measurement of the amount of the purpose of the application in the human body and physiological signals measured. Nowadays people are more health conscious, many wearable devices are toward the development of health care, in which the optical heart rate monitors have been widely used, but the majority of the market with optical sensor product performance not as good as chest-worn heart rate sensing device, there are a lot of literature that related to PPG heart rate measurement instability. Because PPG Sensor is fragile, so we add a layer of the lens to prevent the water and protect the PPG Sensor, but it will affect the reception result PPG Sensor, so add a different lens material to do the test. In this study, the main characteristics of the light source and the difference between structural changes PPG used to explore, The results were received from the PPG Sensor distance between the LED and, together with the material and thickness of the lens to achieve the best signal reception.
Keyword：Photoplethysmogram (PPG)、Electrocardiography(ECG)、Sensor、Source characteristics
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Ting-YuKuo and 郭庭瑀. "The Analysis of the Photoplethysmography Signal Characteristic." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/75658534438529179755.
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碩士<br>國立成功大學<br>工程科學系<br>104<br>This thesis serves to find the characteristics of light sensors for PPG sensing. Though the light sensors are convenient to employ, the quality of the PPG signal is usually affected by noises and motion artifacts. Therefore, it is essential to know the PPG signal features under different conditions.
The PPG signal can be obtained by light sensors of different wavelengths; this study uses three kinds of LEDs to implement for examination, including green (525 nm), red (660 nm), infrared (950 nm) lights. The penetration depth varies with respect to wavelengths, the distribution of blood vessels and capillaries is different for each measurement site. Moreover, different skin colors have distinct absorption of light wavelengths. Experiments are designed to examine the relationship between light wavelengths and measurement sites. Heart rate information is deduced by Fourier transform; the frequency of the highest peak indicates the subject’s heart rate.
The experimental results show that the infrared light emitting diode provides the strongest signal magnitude among all measurement sites. The subject who has deep color skin causes reduction on the signal magnitude. The changes of the highest peak position is visible before and after physical exercise. Furthermore, the motion artifact can be evidently observed in the frequency domain. The magnitude decreases after exercise for each subject.
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Chang, Chao-Feng, and 張肇峰. "Analysis natural heart rate variability using photoplethysmography." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/61496551429946367984.
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碩士<br>中原大學<br>醫學工程研究所<br>96<br>This innovation is related to measuring the heart rate under unawareness of subject to extract the true nature heart rate variability. The Heart Rate Variability (HRV) is an important index that could be used for long term monitor of cardiac function. The low variability of heart rate indicates that the cardiac rhythm could not be regulated by autonomic nerve system. It is not a healthy condition for regular daily activities. This innovation has devised a portable photo-plethysmo-graphy (PPG) through an ear plug appliance.
The PPG signal was acquired and analyzed using a simple microcontroller with a MP3 data decoder. In this way, the user of MP3 player could has option of monitoring and recording his or her heart rate and heart rate variability regularly and unaware. The prototype system was also including functions of data display with color LCD, data storage with CF card, data communication with USB. An off-line PC window program was also provided for reviewing the recorded PPG and analyzed HRV.
The system was used to assess the psychophysic effect of heart beat monitoring over four circumstances. That were the situation of monitoring the ECG without listening to music, assessing the PPG without listening to music, listening to music with monitoring the ECG, and listening to music with the assessment of PPG. Four types of HRV parameters were analysed among named four circumstances using Student’s T-TEST. It were to examine the impact of heart beat monitoring methods on users. While examining the HRV frequency spectrum against each testing situation, the parasympathetic tone was found activated much earlier using PPG to assessing heart beat than the using ECG. This result demonstrated that the subjects’s heat rate and their natural heart rate variability could be monitored unconsciously using PPG while listening to music.
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Shen, Ta-Yu, and 沈大祐. "Recognition of Serious Arrhythmia Using Electrocardiogram and Photoplethysmography." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/farv99.
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碩士<br>國立中正大學<br>電機工程研究所<br>104<br>In this study, we proposed a serious arrhythmia recognition system based on two physiological signals. Electrocardiogram (ECG) and Photoplethysmprgraphy (PPG) were used to recognize four kinds of disease, including bradycardia, tachycardia, ventricular tachycardia, and asystole.
The proposed method was divided into two parts. The first part was the direct identification method that recognized serious arrhythmias by a continuous heart rate and pulse width characteristics. The second part used direct identification combined with a classifier for recognition. Two classifiers, support vector machine (SVM) and back-propagation neural network (BPNN) were used. For the feature extraction, we discovered that when the disease occurred, the waveform and amplitude of the ECG signal and PPG signal would change. Therefore, we hope to use the waveform relevant features to improve the accuracy. The results showed that the waveform relevant features proposed in this study raised the overall recognition rate. Moreover, in order to more effevtively enhance the overall accuracy and reduce the recognition time, we proposed multi-level classification methods that combined direct recognition method (D) and classifier recognition method (C), including DC, DDC, and DCC. We also employed leave-one-out scheme for cross validation. According to the results, regardless of signal combination, DDC system with BPNN classifier had best the accuracy. The accuracy was 99.24% when using two signals, 99.24% when using ECG signal alone, 94.66% when using PPG signal alone for recognition.
According to the result, although the use of two signals and ECG signal with DDC system have the best performance, our final goal is to use PPG signal alone for serious arrhythmia recognition. The accuracy could reach 94.66% when using PPG signal alone with DDC system for recognition, and the average time was about 0.11 seconds to recognize one record. The result demonstrated the high-capability and real-time recognition feasibility of the proposed serious arrhythmia recognition system.
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Chen, Yuwei, and 陳昱維. "Study on photoplethysmography signal measurements of respiratory rate." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/68349212714129687672.
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碩士<br>聖約翰科技大學<br>電子工程系碩士班<br>100<br>The advantage of Photoplethysmography measurement easy to set up, PPG contains many physiological parameters such as heart rate, respiratory rate, arterial stiffness index, and easy to use and low cost.
This study is based on measurement of respiratory rate, the architecture consist of software and hardware, hardware by the high-pass filter, an inverting amplifier, low pass filter combination, is mainly responsible for the PPG of signal acquisition, filtering and signal amplification software by MATLAB finite impulse response filter (FIR) with zero phase shift to the end grab the peak respiratory signal envelope ,this architecture to mention the measurement of respiratory rate in order to facilitate medical staff diagnosis.
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Yang, Tzong-Lin, and 楊宗霖. "Noninvasive estimation of continuous arterial blood pressure using Photoplethysmography." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/70710518567518363683.
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碩士<br>國立臺灣大學<br>醫學工程學研究所<br>98<br>Continuous Blood pressure is one of the most important vital signs to evaluate cardiac-vascular system conditions especially monitoring in intensive care units and operation zones. However, the usage of arterial-line is the most common method of continuous blood pressure measurement. It is measuring real-time blood pressure variations and waveforms directly and reliably, but it neither sets up complex nor is an invasive procedure to induce the risks, like infection or embolism. Photoplethysmography is a non-invasive technology to measure the change of tissue vessel volume concerned with cardiac-vascular system. The aim of research is to find the possibility of developing an easy use, stable, noninvasive, and long term measurement of blood pressure by photoplethysmography.