Rapid optical determination of salivary cortisol responses in individuals undergoing physiological and psychological stress.

Traditional methods for management of mental illnesses in the post-pandemic setting can be inaccessible for many individuals due to a multitude of reasons, including financial stresses and anxieties surrounding face-to-face interventions. The use of a point-of-care tool for self-management of stress levels and mental health status is the natural trajectory towards creating solutions for one of the primary contributors to the global burden of disease. Notably, cortisol is the main stress hormone and a key logical indicator of hypothalamic-pituitary adrenal (HPA) axis activity that governs the activation of the human stress system.

Monte Carlo simulation of the effect of melanin concentration on light-tissue interactions for transmittance pulse oximetry measurement.

Significance: Questions about the accuracy of pulse oximeters in measuring arterial oxygen saturation ( ) in individuals with darker skin pigmentation have resurfaced since the COVID-19 pandemic. This requires investigation to improve patient safety, clinical decision making, and research.

Aim: We aim to use computational modeling to identify the potential causes of inaccuracy in measurement in individuals with dark skin and suggest practical solutions to minimize bias.

Monte Carlo simulation of the effect of melanin concentration on light-tissue interactions in transmittance and reflectance finger photoplethysmography.

Photoplethysmography (PPG) uses light to detect volumetric changes in blood, and is integrated into many healthcare devices to monitor various physiological measurements. However, an unresolved limitation of PPG is the effect of skin pigmentation on the signal and its impact on PPG based applications such as pulse oximetry. Hence, an in-silico model of the human finger was developed using the Monte Carlo (MC) technique to simulate light interactions with different melanin concentrations in a human finger, as it is the primary determinant of skin pigmentation.

Multi-Modal Spectroscopic Assessment of Skin Hydration.

Human skin acts as a protective barrier, preserving bodily functions and regulating water loss. Disruption to the skin barrier can lead to skin conditions and diseases, emphasizing the need for skin hydration monitoring. The gold-standard sensing method for assessing skin hydration is the Corneometer, monitoring the skin's electrical properties.

A review of the effect of skin pigmentation on pulse oximeter accuracy.

. Pulse oximetry is a non-invasive optical technique used to measure arterial oxygen saturation (SpO) in a variety of clinical settings and scenarios. Despite being one the most significant technological advances in health monitoring over the last few decades, there have been reports on its various limitations.

The Impact of Acetic Acid on Measuring Ethanol Concentrations in Water and Human Serum Using Short-Wave Infrared Spectroscopy.

Ethanol intoxication, although an elemental part of life in many places around the world, still presents several issues associated with excessive consumption. These issues range from drunk driving, violence, and antisocial behavior to self-harm, all exerting an increased cost on the society. Monitoring of intoxication levels can help to limit the impact of these issues by preventing the use of automobiles or heavy machinery and personal monitoring.

A paper-based colorimetric method for monitoring of lithium therapeutic levels.

Lithium remains the "gold standard" for both acute and maintenance treatment of bipolar disorder (BD), a serious life-long condition characterised by recurrent episodes of depressed and manic mood states. However, lithium has a very narrow therapeutic range (0.4-1.

Measuring stress: a review of the current cortisol and dehydroepiandrosterone (DHEA) measurement techniques and considerations for the future of mental health monitoring.

Psychological stress and its inevitable trajectory toward mental health deteriorations such as clinical and major depression has become an unprecedented global burden. The diagnostic procedures involved in the characterization of mental illnesses commonly follow qualitative and subjective measures of stress, often leading to greater socioeconomic burdens due to misdiagnosis and poor understanding of the severity of such illnesses, further fueled by the stigmatization surrounding mental health. In recent years, the application of cortisol and stress hormone measurements has given rise to an alternative, quantifiable approach for the psychological evaluation of stress and depression.

Review of Advances in the Measurement of Skin Hydration Based on Sensing of Optical and Electrical Tissue Properties.

The presence of water in the skin is crucial for maintaining the properties and functions of the skin, in particular its outermost layer, known as the stratum corneum, which consists of a lipid barrier. External exposures can affect the skin's hydration levels and in turn, alter its mechanical and physical properties. Monitoring these alterations in the skin's water content can be applicable in clinical, cosmetic, athletic and personal settings.

Review of Ethanol Intoxication Sensing Technologies and Techniques.

The field of alcohol intoxication sensing is over 100 years old, spanning the fields of medicine, chemistry, and computer science, aiming to produce the most effective and accurate methods of quantifying intoxication levels. This review presents the development and the current state of alcohol intoxication quantifying devices and techniques, separated into six major categories: estimates, breath alcohol devices, bodily fluid testing, transdermal sensors, mathematical algorithms, and optical techniques. Each of these categories was researched by analyzing their respective performances and drawbacks.

Advances in Therapeutic Monitoring of Lithium in the Management of Bipolar Disorder.

Since the mid-20th century, lithium continues to be prescribed as a first-line mood stabilizer for the management of bipolar disorder (BD). However, lithium has a very narrow therapeutic index, and it is crucial to carefully monitor lithium plasma levels as concentrations greater than 1.2 mmol/L are potentially toxic and can be fatal.

In-silico investigation towards the non-invasive optical detection of blood lactate.

This paper uses Monte Carlo simulations to investigate the interaction of short-wave infrared (SWIR) light with vascular tissue as a step toward the development of a non-invasive optical sensor for measuring blood lactate in humans. The primary focus of this work was to determine the optimal source-detector separation, penetration depth of light at SWIR wavelengths in tissue, and the optimal light power required for reliable detection of lactate. The investigation also focused on determining the non-linear variations in absorbance of lactate at a few select SWIR wavelengths.

Design and Analysis of a Continuous and Non-Invasive Multi-Wavelength Optical Sensor for Measurement of Dermal Water Content.

Dermal water content is an important biophysical parameter in preserving skin integrity and preventing skin damage. Traditional electrical-based and open-chamber evaporimeters have several well-known limitations. In particular, such devices are costly, sizeable, and only provide arbitrary outputs.

Comparison of Dual Beam Dispersive and FTNIR Spectroscopy for Lactate Detection.

Near Infrared (800-2500 nm) spectroscopy has been extensively used in biomedical applications, as it offers rapid, in vivo, bed-side monitoring of important haemodynamic parameters, which is especially important in critical care settings. However, the choice of NIR spectrometer needs to be investigated for biomedical applications, as both the dual beam dispersive spectrophotomer and the FTNIR spectrometer have their own advantages and disadvantages. In this study, predictive analysis of lactate concentrations in whole blood were undertaken using multivariate techniques on spectra obtained from the two spectrometer types simultaneously and results were compared.

Comparison of wavelength selection methods for in-vitro estimation of lactate: a new unconstrained, genetic algorithm-based wavelength selection.

Biochemical and medical literature establish lactate as a fundamental biomarker that can shed light on the energy consumption dynamics of the body at cellular and physiological levels. It is therefore, not surprising that it has been linked to many critical conditions ranging from the morbidity and mortality of critically ill patients to the diagnosis and prognosis of acute ischemic stroke, septic shock, lung injuries, insulin resistance in diabetic patients, and cancer. Currently, the gold standard for the measurement of lactate requires blood sampling.

Identification and Quantitative Determination of Lactate Using Optical Spectroscopy-Towards a Noninvasive Tool for Early Recognition of Sepsis.

Uninterrupted monitoring of serum lactate levels is a prerequisite in the critical care of patients prone to sepsis, cardiogenic shock, cardiac arrest, or severe lung disease. Yet there exists no device to continuously measure blood lactate in clinical practice. Optical spectroscopy together with multivariate analysis is proposed as a viable noninvasive tool for estimation of lactate in blood.

Investigations into the Effects of pH on Quantitative Measurements of Lactate in Biological Media Using ATR-FTIR Spectroscopy.

Quantification of lactate/lactic acid in critical care environments is essential as lactate serves as an important biochemical marker for the adequacy of the haemodynamic circulation in shock and of cell respiration at the onset of sepsis/septic shock. Hence, in this study, ATR-FTIR was explored as a potential tool for lactate measurement, as the current techniques depend on sample preparation and fails to provide rapid response. Moreover, the effects of pH on PBS samples (7.

Reflectance near-infrared measurements for determining changes in skin barrier function and scattering in relation to moisturizer application.

Skin moisture relates to the state of multiple skin constituents and aspects, but unfortunately, a device which could provide comprehensive and in vivo analysis is not available. Nevertheless, several reports have demonstrated accurate estimations of dermal water content using near-infrared spectroscopy (NIRS), and the potential of employing this technique in skin analysis. We aim to investigate whether NIRS could detect changes in skin barrier function through evaluation of skin water uptake in relation to moisturizer application.

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.