4,598 research outputs found
Recommended from our members
A review of machine learning techniques in photoplethysmography for the non-invasive cuff-less measurement of blood pressure
Hypertension or high blood pressure is a leading cause of death throughout the world and a critical factor for increasing the risk of serious diseases, including cardiovascular diseases such as stroke and heart failure. Blood pressure is a primary vital sign that must be monitored regularly for the early detection, prevention and treatment of cardiovascular diseases. Traditional blood pressure measurement techniques are either invasive or cuff-based, which are impractical, intermittent, and uncomfortable for patients. Over the past few decades, several indirect approaches using photoplethysmogram (PPG) have been investigated, namely, pulse transit time, pulse wave velocity, pulse arrival time and pulse wave analysis, in an effort to utilise PPG for estimating blood pressure. Recent advancements in signal processing techniques, including machine learning and artificial intelligence, have also opened up exciting new horizons for PPG-based cuff less and continuous monitoring of blood pressure. Such a device will have a significant and transformative impact in monitoring patients’ vital signs, especially those at risk of cardiovascular disease. This paper provides a comprehensive review for non-invasive cuff-less blood pressure estimation using the PPG approach along with their challenges and limitations
Recommended from our members
Estimation of Venous oxygenation saturation using the finger Photoplethysmograph (PPG) waveform
In this study, finger photoplethysmograph data obtained from twelve patients undergoing cardiothoracic surgery were analyzed in order to estimate the venous saturation utilizing the modulations created by the positive pressure ventilation in the AC Photoplethysmograph (PPG) signals. The PPG signals were analyzed in the time-domain using a conventional pulse oximetry algorithm to produce estimations of arterial oxygen saturation. The instantaneous arterial and venous saturations were estimated by utilizing time-frequency analysis technique of Smoothed-pseudo Wigner-Ville Distribution (SPWVD). The results showed that there was no significant difference in the traditionally-derived (time-domain) arterial saturation and the instantaneous arterial saturation. However, the instantaneous venous saturation was found to be significantly lower than the time-domain estimated and instantaneous arterial saturation (P=<;0.001)
Recommended from our members
Development and in vitro evaluation of an artificial spinal disc loading cell
One of the common diseases for chronic low back pain is Disc Degeneration Disease (DDD). In this disease, spinal intervertebral disc loses its ability to safely handle the mechanical stresses. The knowledge of the in-vivo loading on the spinal disk is of great importance in the understanding of low back pain. In this study a loading cell has been developed utilizing an artificial spinal disc which was loaded with strain gauges and piezoresistive sensors in an effort to investigate the behavior of the sensors during in vitro loading of the disc. The artificial disc with all sensors was loaded in a laboratory environment. The in vitro loading produced reliable and repeatable results and therefore suggesting that such approach might aid in the development of an artificial intelligent disc which will contribute in the better understanding of the in vivo loading of the human spine
Recommended from our members
A Multilayer Monte Carlo Model for the Investigation of Optical Path and Penetration Depth at Different Perfusion States of the Colon
There is a great interest in monitoring the oxygen supply delivered to the colon. Insufficient oxygen delivery may lead to hypoxia, sepsis, multiorgan dysfunction and death. For assessing colonic perfusion, more information and understanding is required relating to the light-interaction within the colonic tissue. A multilayer Monte Carlo model of a healthy human colon has been developed to investigate the light-tissue behavior during different perfusion states within the mucosal layer of the colon. Results from a static multilayer model of optical path and reflectance at two wavelengths, 660 nm and 880 nm, through colon tissue, containing different volume fractions of blood with a fixed oxygen saturation are presented. The effect on the optical path and penetration depth with varying blood volumes within the mucosa for each wavelength has been demonstrated. The simulation indicated both wavelengths of photons penetrated similar depths, entering the muscularis layer
Recommended from our members
Temperature sensor technology
Human body temperature is of vital importance to the well being of the person and therefore it is routinely monitored to indicate the state of the person’s health. Despite the fact that temperature measurement in humans seems so simple, a wide variety of devices are available to record a temperature from skin, oral or rectal mucosa or the tympanic membrane. The choice of clinical thermometers for health professionals and parents has never been so complicated.
This chapter makes an attempt to provide an overview of temperature sensing technologies in medicine. The introductory sections give a brief and general description of temperature and its effect on the human body. A synoptic historical review on the evolution of the thermometer including the clinical thermometer is given in section 3. Section 4 describes the main sensors/transducers used in the development of clinical thermometers, such as thermocouples, thermistors, Resistance Temperature Detectors (RTDs), semiconductor temperature sensors, liquid crystal temperature sensors, and infra-red radiation sensors. These thermometers have been designed and developed for application in various parts of the body such as the rectum, the mouth, the axilla, the esophagus, the bladder, the ear, the temporal artery, the skin, and this will be the content of section 5. It will be almost impossible for this chapter to cover every possible application and evaluation study relating to different thermometers; however an effort is made in section 6 to provide an integrative review of studies comparing selected invasive and non-invasive temperature measurement methods
Recommended from our members
Development of a Reflectance Fibre-Optic Pulse Oximetry Probe for Use in Abdominal Organs
The early detection of inadequate splanchnic tissue oxygenation would reduce the risk of hypoperfusion, severe ischaemia, and multiple organ failure [1]. None of the currently available methods provide continuous monitoring of splanchnic perfusion pre-operatively, operatively and post-operatively. In an attempt to overcome these limitations, a new fibre-optic probe utilizing the principle of reflectance pulse oximetry was developed. The separation distance between the source and detector fibres of the probe has a direct impact on the quality of the photoplethysmographic (PPG) signal and the accurate estimation of blood oxygen saturation (SpO2) [2]. Prior to finalising the probe design, an investigation was conducted to establish the optimum source-detector separation
Recommended from our members
Investigation of photoplethysmography and arterial blood oxygen saturation from the ear-canal and the finger under conditions of artificially induced hypothermia
Pulse oximeters relay on the technique of photoplethysmography (PPG) to estimate arterial oxygen saturation (SpO2). In conditions of poor peripheral perfusion such as hypotension, hypothermia, and vasoconstriction, pulse oximeters become inaccurate or provide no reading. This is due to the poor quality of the PPG signals detected at that instance. In order to overcome this problem, the ear canal has been proposed as a alternative measurement site for measuring reliable SpO2. Hence, an ear canal PPG sensor was developed along with a PPG processing system. The performance of the sensor was evaluated by measuring the red and infrared PPGs and SpO2 from 10 healthy volunteers undergoing artificially induced hypothermia. The results from the ear canal sensor were compared with simultaneously acquired results from the finger. Hypothermia was induced by exposing the volunteers to cold temperatures of 10 ± 1°C. The results acquired suggest that the ear canal pulse oximeter endures more in estimating SpO2 values accurately when compared with the more common finger pulse oximeter
Recommended from our members
Use of reflectance near-infrared spectroscopy to investigate the effects of daily moisturizer application on skin optical response and barrier function
A number of noninvasive techniques and instruments have emerged over the years allowing much progress toward clarifying the structure and function of human skin and studying the effects of various applied substances. All of this research has provided great insight into the interactions between skin and various products through quantitative and qualitative measurements. Such methods include near-infrared spectroscopy (NIRS), a technique which has gained popularity over the years and has often been employed to accurately determine the moisture levels and water content of skin based on its sensitivity to hydrogen bonding. NIRS has also been applied in many studies to report the efficacy of moisturizing products and assess their benefits to the skin. However, many of these studies have reported an increase in skin water content following moisturizer application while some have challenged the benefits of long-term moisturizer use, particularly on normal skin, and even suggested that it can increase the skin’s susceptibility to irritants. This paper reports the results of a pilot in vivo study carried out on the skin of 20 healthy volunteers, categorized into groups depending on their skin type and frequency of moisturizer use, in order to investigate the optical response of human skin after direct short-term contact with water followed by application of a moisturizer. The measurements were obtained using a highly advanced spectrophotometer in the region of 900 to 2100 nm equipped with a customized reflectance fiber optic handheld probe. Scatter graphs of group results and second derivative spectra have shown an interesting pattern between frequent users of moisturizers and individuals who do not use moisturizers, suggesting that long-term daily moisturization may have an effect on skin barrier function. The results also raise some questions regarding the optical characteristics of different skin types, as well as the varying response between different water bands in the NIR region. Future work will focus on gaining more knowledge about these subjects and obtaining results from a larger population, as well as performing statistical analysis through regression methods in order to further improve optical skin measurements
Recommended from our members
Near infrared spectrometric investigation of lactate in a varying pH buffer
Lactic acidosis is commonly observed in various disease states in critical care and can be adopted as a hemodynamic biomarker, as well as a target for therapy. pH is the main biomarker for the diagnosis of acid–base disorders and is currently measured utilizing invasive blood sampling techniques. Therefore, there is a need for a non-invasive and continuous technology for the measurement of pH and lactate levels. In this work, near infrared spectroscopy is explored as a technique for investigating lactic acidosis. In-vitro studies on 20 isotonic phosphate buffer solutions of varying pH with constant lactate concentration (2 mmol/L) were performed. The whole near infrared spectrum (800–2600 nm) was then divided into four parts for analysis: (a) water absorption peaks, (b) 1000–1250 nm, (c) 1700–1760 nm, and (d) 2200–2400 nm. The water absorption peaks showed a linear variation with the changes in pH in the spectra. The range from 1700–1760 nm showed good correlation with calculated values for lactate ionization, with the changes in pH. However, the region from 2200–2400 nm showed a reverse correlation with respect to the concentration changes of lactate and a distinction could be made from pH 6–7 and 7–8. This study successfully identifies wavelengths (1233 nm, 1710 nm, 1750 nm, 2205 nm, 2319 nm, and 2341 nm) which can be directly correlated to lactic acidosis. Knowledge from this study will contribute toward the development of lactate-based pH monitoring optical sensor for critical care
Recommended from our members
Accuracy of reflectance photoplethysmography on detecting cuff-induced vascular occlusions
Photoplethysmography (PPG) is a noninvasive optical technique, which can also be used to derive important parameters other than arterial oxygen saturation (SpO2). In this work, the accuracy of the technique on detecting changes in blood perfusion during different levels of vascular occlusions has been explored. A dual-wavelength, reflectance PPG probe was applied on the left forearm of 10 healthy volunteers and raw PPG signals were acquired by a research PPG processing system. The raw PPG signals were separated into pulsatile AC and continuous DC PPG components. The signals were used to estimate SpO2 and changes in concentration of oxygenated, deoxygenated, and total haemoglobin. Different levels of occlusions, from 20 mmHg to total occlusion were induced by a pressure-cuff on the left arm. The system was able to indicate all the occlusions. In particular, the haemoglobin concentration changes estimated from PPG were in high agreement with Near Infrared Spectroscopy measurements
- …