12 research outputs found
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Theory of dynamic pulsatile spectroscopy for photoplethysmographic signals analysis
Photoplethysmography (PPG) is a technique that uses light to non-invasively obtain a volumetric measurement of an organ with each cardiac cycle. Pulse Oximetry (PO) is an empirical technique which allows the arterial blood oxygen saturation (SpO2) evaluation from the PPG signals. There have been many reports in the literature suggesting that other arterial blood chemical components can be evaluated from the PPG signals. Most attempts to perform such evaluation on empirical bases have failed, especially for components concentrations. This paper introduces a non-empirical rational theory called Dynamic Pulsatile Spectroscopy (DPS) which can be used to analytically investigate the phenomena of PPG. The DPS theory provides the mathematically rigid method of how PPG signals can be used for arterial blood analysis to evaluate its chemical component concentrations and molar fractions spectroscopically and transcutaneously. It also highlights what other signals might be required for such evaluation. DPS opens the possibility of extending PPG application for blood analysis beyond conventional PO. The DPS basic principles are introduced in this paper
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Design and Development of a Modular, Multichannel Photoplethysmography System
In this paper, we present the design, development, and validation of a `modular photoplethysmography (PPG) system called ZenPPG. This portable, dual-channel system has the capability to produce ``raw'' PPG signals at two different wavelengths using commercial and/or custom-made PPG sensors. The system consists of five modules, each consisting of circuitry required to perform specific tasks, and are all interconnected by a system bus. The ZenPPG system also facilitates the acquisition of other physiological signals on-demand including electrocardiogram (ECG), respiration, and temperature signals. This report describes the technical details and the evaluation of the ZenPPG along with results from a pilot in vivo study on healthy volunteers. The results from the technical evaluations demonstrate the superiority and flexibility of the system. Also, the systems' compatibility with commercial pulse oximetry sensors such as the Masimo reusable sensors was demonstrated, where good quality raw PPG signals were recorded with the signal-to-noise ratio (SNR) of 50.65 dB. The estimated arterial oxygen saturation (SpO & #x2082;) values from the system were also in close agreement with commercial pulse oximeters, although the accuracy of the reported SpO & #x2082; value is dependent on the calibration function used. Future work is targeted toward the development of variations of each module, including the laser driver and fiber optic module, onboard data acquisition and signal processing modules. The availability of this system will help researchers from a wide range of disciplines to customize and integrate the ZenPPG system to their research needs and will most definitely enhance research in related fields
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MyCare Card Development: Portable GUI Framework for the Personal Electronic Health Record Device
In most emergency situations, health professionals rely on patients to provide information about their medical history. However, in some cases patients might not be able to communicate this information, and in most countries an online integrated patient record system has not been adopted yet. Therefore, in order to address this issue the ongoing project MyCare Card (MyC2, www.myc2.org) has been established. The aim of this project is to design, implement, and evaluate a prototype patient held electronic health record device. Due to the wide range of user requirements, the device, its communication interface, and its software have to be compatible with many common platforms and operating systems. Thus, this paper is addressing one of the software compatibility matters-the cross-platform GUI implementation. It introduces a portable object-oriented GUI framework, suitable for a declarative layout definition, components customization, and fine model-view code separation. It also rationalizes the hardware and software solutions selected for this project implementation
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Design and development of a novel multi-channel photoplethysmographic research system
Photoplethysmography (PPG) is a technique that uses light to non-invasively obtain a volumetric measurement of an organ with each cardiac cycle. Pulse Oximetry (PO) is an empirical technique which allows the arterial blood oxygen saturation (SpO2) evaluation from the PPG signals. There have been many reports in the literature suggesting that other arterial blood chemical components can be evaluated from the PPG signals. Most attempts to perform such evaluation on empirical bases have failed, especially for components concentrations. This paper introduces a non-empirical rational theory called Dynamic Pulsatile Spectroscopy (DPS) which can be used to analytically investigate the phenomena of PPG. The DPS theory provides the mathematically rigid method of how PPG signals can be used for arterial blood analysis to evaluate its chemical component concentrations and molar fractions spectroscopically and transcutaneously. It also highlights what other signals might be required for such evaluation. DPS opens the possibility of extending PPG application for blood analysis beyond conventional PO. The DPS basic principles are introduced in this paper
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Beer-Lambert law along non-linear mean light pathways for the rational analysis of Photoplethysmography
Photoplethysmography (PPG) is a technique that uses light to noninvasively obtain a volumetric measurement of an organ with each cardiac cycle. A PPG-based system emits monochromatic light through the skin and measures the fraction of the light power which is transmitted through a vascular tissue and detected by a photodetector. Part of thereby transmitted light power is modulated by the vascular tissue volume changes due to the blood circulation induced by the heart beating. This modulated light power plotted against time is called the PPG signal. Pulse Oximetry is an empirical technique which allows the arterial blood oxygen saturation (SpO2 – molar fraction) evaluation from the PPG signals. There have been many reports in the literature suggesting that other arterial blood chemical components molar fractions and concentrations can be evaluated from the PPG signals. Most attempts to perform such evaluation on empirical bases have failed, especially for components concentrations. This paper introduces a non-empirical physical model which can be used to analytically investigate the phenomena of PPG signal. Such investigation would result in simplified engineering models, which can be used to design validating experiments and new types of spectroscopic devices with the potential to assess venous and arterial blood chemical composition in both molar fractions and concentrations non-invasively
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Investigation of finger reflectance photoplethysmography in volunteers undergoing a local sympathetic stimulation
Optical sensors used in clinical applications have gained great popularity over the last few decades, especially the photoplethysmographic (PPG) technique used in estimating arterial blood oxygen saturation in the well-known medical devices called pulse oximeters. In this study we investigate the photoplethysmogram further in an effort to understand its origin better, as there is a significant void in the current knowledge on the PPG quantitative measurement. The photoplethysmographic signal provides a heart rhythm pulsating AC component, and a non-pulsating DC component. The signal is commonly believed to originate from tissue volume changes only and hasn't been investigated intensively. This in vivo study examines the source of the PPG signal in relation to pulse amplitude and pulse rhythm while volunteers undergo a right hand ice immersion. It was found that the PPG signal is sensitive in detecting the sympathetic stimulation which corresponds to volumetric and heart rate changes. During the immersion, AC pulse amplitudes (PA) from both hands decreased significantly, while DC levels increased significantly in the right hand and non-significantly in the left hand. Also, a significant decrease in the pulse repetition time (PRT) was observed. Using blood pressure-flow theories, these results suggest that there are possibly other factors in the blood flow regulation that alter the blood optical density which contributes to the detected signal. Further studies need to investigate PPGs in relation to blood optical density and the dynamics of the pulsatile flow effects besides volumetric changes. Such investigations might explore further applications of the PPG in medicine
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The human ear canal: investigation of its suitability for monitoring photoplethysmographs and arterial oxygen saturation
For the last two decades, pulse oximetry has been used as a standard procedure for monitoring arterial oxygen saturation (SpO2). However, SpO2 measurements made from extremities such as the finger, ear lobe and toes become susceptible to inaccuracies when peripheral perfusion is compromised. To overcome these limitations, the external auditory canal has been proposed as an alternative monitoring site for estimating SpO2, on the hypothesis that this central site will be better perfused. Therefore, a dual wavelength optoelectronic probe along with a processing system was developed to investigate the suitability of measuring photoplethysmographic (PPG) signals and SpO2 in the human auditory canal. A pilot study was carried out in 15 healthy volunteers to validate the feasibility of measuring PPGs and SpO2 from the ear canal (EC), and comparative studies were performed by acquiring the same signals from the left index finger (LIF) and the right index finger (RIF) in conditions of induced peripheral vasoconstriction (right hand immersion in ice water). Good quality baseline PPG signals with high signal-to-noise ratio were obtained from the EC, the LIF and the RIF sensors. During the ice water immersion, significant differences in the amplitude of the red and infrared PPG signals were observed from the RIF and the LIF sensors. The average drop in amplitude of red and infrared PPG signals from the RIF was 52.7% and 58.3%. Similarly, the LIF PPG signal amplitudes have reduced by 47.52% and 46.8% respectively. In contrast, no significant changes were seen in the red and infrared EC PPG amplitude measurements, which changed by +2.5% and -1.2% respectively. The RIF and LIF pulse oximeters have failed to estimate accurate SpO2 in seven and four volunteers respectively, while the EC pulse oximeter has only failed in one volunteer. These results suggest that the EC may be a suitable site for reliable monitoring of PPGs and SpO2s even in the presence of peripheral vasoconstriction
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A systematic approach for the accurate non-invasive estimation of blood glucose utilizing a novel light-tissue interaction adaptive modelling scheme
Diabetes is one of the biggest health challenges of the 21st century. The obesity epidemic, sedentary lifestyles and an ageing population mean prevalence of the condition is currently doubling every generation. Diabetes is associated with serious chronic ill health, disability and premature mortality. Long-term complications including heart disease, stroke, blindness, kidney disease and amputations, make the greatest contribution to the costs of diabetes care. Many of these long-term effects could be avoided with earlier, more effective monitoring and treatment. Currently, blood glucose can only be monitored through the use of invasive techniques. To date there is no widely accepted and readily available non-invasive monitoring technique to measure blood glucose despite the many attempts. This paper challenges one of the most difficult non-invasive monitoring techniques, that of blood glucose, and proposes a new novel approach that will enable the accurate, and calibration free estimation of glucose concentration in blood. This approach is based on spectroscopic techniques and a new adaptive modelling scheme. The theoretical implementation and the effectiveness of the adaptive modelling scheme for this application has been described and a detailed mathematical evaluation has been employed to prove that such a scheme has the capability of extracting accurately the concentration of glucose from a complex biological media