Validation of a Monte Carlo platform for the optical modelling of pulse oximetry

A custom Monte Carlo (MC) platform has been established to generate opto-physiological models of mechanisms in pulse oximetry. The current research is an exploration of the process of empirically validating such a platform. With the growing availability and accuracy of tissue optical properties in literatures, MC simulation of light-tissue interaction is providing increasingly valuable information for optical bio-monitoring research. However, the extent of the validity of results from such simulations depends heavily on its agreement with empirical data. The use of images captured from a CMOS camera for the construction of intensity distributions of light transmitted through the human finger has been investigated to compare with corresponding distributions produced in the MC simulations

A comparative study of physiological monitoring with a wearable opto-electronic patch sensor (OEPS) for motion reduction

This paper presents a comparative study in physiological monitoring between a wearable opto-electronic patch sensor (OEPS) comprising a three-axis Microelectromechanical systems (MEMs) accelerometer (3MA) and commercial devices. The study aims to effectively capture critical physiological parameters, for instance, oxygen saturation, heart rate, respiration rate and heart rate variability, as extracted from the pulsatile waveforms captured by OEPS against motion artefacts when using the commercial probe. The protocol involved 16 healthy subjects and was designed to test the features of OEPS, with emphasis on the effective reduction of motion artefacts through the utilization of a 3MA as a movement reference. The results show significant agreement between the heart rates from the reference measurements and the recovered signals. Significance of standard deviation and error of mean yield values of 2.27 and 0.65 beats per minute, respectively; and a high correlation (0.97) between the results of the commercial sensor and OEPS. T, Wilcoxon and Bland-Altman with 95% limit of agreement tests were also applied in the comparison of heart rates extracted from these sensors, yielding a mean difference (MD: 0.08). The outcome of the present work incites the prospects of OEPS on physiological monitoring during physical activities

A Monte Carlo platform for the optical modeling of pulse oximetry

We investigated a custom Monte Carlo (MC) platform in the generation of opto-physiological models of motion artefact and perfusion in pulse oximetry. With the growing availability and accuracy of tissue optical properties in literatures, MC simulation of light-tissue interaction is providing increasingly valuable information for optical bio-monitoring research. Motion-induced artefact and loss of signal quality during low perfusion are currently the primary limitations in pulse oximetry. While most attempts to circumvent these issues have focused on signal post-processing techniques, we propose the development of improved opto-physiological models to include the characterisation of motion artefact and low perfusion. In this stage of the research, a custom MC platform is being developed for its use in determining the effects of perfusion, haemodynamics and tissue-probe optical coupling on transillumination at different positions of the human finger. The results of MC simulations indicate a useful and predictable output from the platform

A high performance biometric signal and image processing method to reveal blood perfusion towards 3D oxygen saturation mapping

Non-contact imaging photoplethysmography (PPG) is a recent development in the field of physiological data acquisition, currently undergoing a large amount of research to characterize and define the range of its capabilities. Contact-based PPG techniques have been broadly used in clinical scenarios for a number of years to obtain direct information about the degree of oxygen saturation for patients. With the advent of imaging techniques, there is strong potential to enable access to additional information such as multi-dimensional blood perfusion and saturation mapping. The further development of effective opto-physiological monitoring techniques is dependent upon novel modelling techniques coupled with improved sensor design and effective signal processing methodologies. The biometric signal and imaging processing platform (bSIPP) provides a comprehensive set of features for extraction and analysis of recorded iPPG data, enabling direct comparison with other biomedical diagnostic tools such as ECG and EEG. Additionally, utilizing information about the nature of tissue structure has enabled the generation of an engineering model describing the behaviour of light during its travel through the biological tissue. This enables the estimation of the relative oxygen saturation and blood perfusion in different layers of the tissue to be calculated, which has the potential to be a useful diagnostic tool

A novel yet effective motion artefact reduction method for continuous physiological monitoring

This study presents a non-invasive and wearable optical technique to continuously monitor vital human signs as required for personal healthcare in today’s increasing ageing population. The study has researched an effective way to capture human critical physiological parameters, i.e., oxygen saturation (SaO2%), heart rate, respiration rate, body temperature, heart rate variability by a closely coupled wearable opto-electronic patch sensor (OEPS) together with real-time and secure wireless communication functionalities. The work presents the first step of this research; an automatic noise cancellation method using a 3-axes MEMS accelerometer to recover signals corrupted by body movement which is one of the biggest sources of motion artefacts. The effects of these motion artefacts have been reduced by an enhanced electronic design and development of self-cancellation of noise and stability of the sensor. The signals from the acceleration and the opto-electronic sensor are highly correlated thus leading to the desired pulse waveform with rich bioinformatics signals to be retrieved with reduced motion artefacts. The preliminary results from the bench tests and the laboratory setup demonstrate that the goal of the high performance wearable opto-electronics is viable and feasible

Non-contact reflection photoplethysmography towards effective human physiological monitoring

A non-contact reflection photoplethysmography (NRPPG) with its engineering model was created to access human physiological information. The NRPPG engineering setup with a vertical cavity surface emitting laser (VCSEL) as a light source and a high-speed PiN photodiode as a photodetector was configured based upon the principles of light-tissue interaction and Beer-Lambert’s law. In this paper, we present three aspects of the NRPPG performance: (1) photonics engineering work to capture photoplethysmographic signals with a non-contact manner in an optimal setup of the NRPPG; (2) a 5-minute protocol with 22 participants to determine a good agreement between NRPPG and contact photoplethysmography (CPPG) by means of Bland-Altman statistical analysis and Pearson’s correlation coefficient; and (3) a physiological experiment designed for cardiac-physiological monitoring utilizing NRPPG. The experimental results suggest that clean PPG signal can be obtained between 30-110 mm. The outcome from agreement study indicates that the performance of NRPPG is compatible with CPPG. The NRPPG technique has great potential in cardiac-physiological assessment in a required clinical circumstance

A multi-channel opto-electronic sensor to accurately monitor heart rate against motion artefact during exercise

This study presents the use of a multi-channel opto-electronic sensor (OEPS) to effectively monitor critical physiological parameters whilst preventing motion artefact as increasingly demanded by personal healthcare. The aim of this work was to study how to capture the heart rate (HR) efficiently through a well-constructed OEPS and a 3-axis accelerometer with wireless communication. A protocol was designed to incorporate sitting, standing, walking, running and cycling. The datasets collected from these activities were processed to elaborate sport physiological effects. t-test, Bland-Altman Agreement (BAA), and correlation to evaluate the performance of the OEPS were used against Polar and Mio-Alpha HR monitors. No differences in the HR were found between OEPS, and either Polar or Mio-Alpha (both p > 0.05); a strong correlation was found between Polar and OEPS (r: 0.96, p < 0.001); the bias of BAA 0.85 bpm, the standard deviation (SD) 9.20 bpm, and the limits of agreement (LOA) from −17.18 bpm to +18.88 bpm. For the Mio-Alpha and OEPS, a strong correlation was found (r: 0.96, p < 0.001); the bias of BAA 1.63 bpm, SD 8.62 bpm, LOA from −15.27 bpm to +18.58 bpm. These results demonstrate the OEPS to be capable of carrying out real time and remote monitoring of heart rate

Opto-physiological sensor and method [2524919]

The present invention relates to a method of controlling an opto-physiological sensor and a method of selecting which wavelengths of light to use in an opto-physiological sensor, and corresponding apparatus for carrying out the methods

Opto-physiological sensor and method: selecting a wavelength for a PPG sensor [2527974]

Selecting a wavelength of light to use in an opto-physiological sensor, the sensor comprising multiple light source channels wherein each channel comprises two or more light sources which are configures to generate light at the same wavelength, comprises; setting a channel quality value for a channel to zero; determining for each light source whether the source is enabled; incrementing the channel quality value for the channel by one for each source that is determined to be enabled within the channel; comparing the channel quality value to a predetermined threshold; and disabling the channel if the quality value does not exceed the predetermined threshold. Determining the signal quality value may comprise measuring AC signal amplitude, DC signal amplitude, the time interval between peaks or troughs in the signals, and/or the AC/DC ratio

A study of opto-physiological modeling to quantify tissue absorbance in imaging photoplethysmography

This paper presents an opto-physiological model (OPM) to quantify the absorbance of multi-layered tissue in imaging photoplethysmography (IPPG). The approach used to generate such a model is to revise the path length of the Beer Lambert law through the Monte Carlo (MC) simulation of multi-layered tissue. The OPM can mathematically quantify the effect of optical properties on the absorbance of multilayered tissue. Subsequently, the absorbance measured from homogeneous, multi-layered tissue phantoms compares with model predictions. To this end, the model is validated to predict the widest range of experimental outcomes while maintaining the highest possible level of accuracy. This study brings a new approach to understand the principle of IPPG