Non-Invasive In-situ Measurement of Blood Lactate using Microwave Sensors.

GOAL: This paper reports the use of a novel electromagnetic sensor technique for real-time non-invasive monitoring of blood lactate in human subjects. METHODS: The technique was demonstrated on 34 participants who undertook a cycling regime, with rest period before and after, to produce a rising and falling lactate response curve. Sensors attached to the arm and legs of participants gathered spectral data, blood samples were measured using a Lactate Pro V2, as well as temperature and heart rate data were collected. RESULTS: Pairwise mutual information and neural networks are used to produce a predictive model. The model shows a good correlation (R = 0.78) between the standard invasive and novel non-invasive electromagnetic wave based blood lactate measurements, with an error of 13.4% in the range of 0 - 12 mmol/L. CONCLUSION: The work demonstrates that electromagnetic wave sensors are capable of determining blood lactate level without the need for invasive blood sampling. SIGNIFICANCE: Measurement of blood metabolites, such as blood lactate, in real-time and non-invasively in hospital environments will reduce the risk of infection, increase the frequency of measurement and ensure timely intervention only when necessary. In sports situations, such tools will enhance training of athletes, and enable more effecting training regimes to be prescribed

Evaluating the Possibility of Translating Technological Advances in Non-Invasive Continuous Lactate Monitoring into Critical Care.

Lactate is widely measured in critically ill patients as a robust indicator of patient deterioration and response to treatment. Plasma concentrations represent a balance between lactate production and clearance. Analysis has typically been performed with the aim of detecting tissue hypoxia. However, there is a diverse range of processes unrelated to increased anaerobic metabolism that result in the accumulation of lactate, complicating clinical interpretation. Further, lactate levels can change rapidly over short spaces of time, and even subtle changes can reflect a profound change in the patient’s condition. Hence, there is a significant need for frequent lactate monitoring in critical care. Lactate monitoring is commonplace in sports performance monitoring, given the elevation of lactate during anaerobic exercise. The desire to continuously monitor lactate in athletes has led to the development of various technological approaches for non-invasive, continuous lactate measurements. This review aims firstly to reflect on the potential benefits of non-invasive continuous monitoring technology within the critical care setting. Secondly, we review the current devices used to measure lactate non-invasively outside of this setting and consider the challenges that must be overcome to allow for the translation of this technology into intensive care medicine. This review will be of interest to those developing continuous monitoring sensors, opening up a new field of research

Sensors for foetal hypoxia and metabolic acidosis: a review

This article reviews existing clinical practices and sensor research undertaken to monitor fetal well-being during labour. Current clinical practices that include fetal heart rate monitoring and fetal scalp blood sampling are shown to be either inadequate or time-consuming. Monitoring of lactate in blood is identified as a potential alternative for intrapartum fetal monitoring due to its ability to distinguish between different types of acidosis. A literature review from a medical and technical perspective is presented to identify the current advancements in the field of lactate sensors for this application. It is concluded that a less invasive and a more continuous monitoring device is required to fulfill the clinical needs of intrapartum fetal monitoring. Potential specifications for such a system are also presented in this paper

Electromagnetic Wearable Sensors: A Solution to Non-Invasive Real-Time Monitoring of Biological Markers during Exercise

Wearable sensing technology enables greater insights into the performance and health status of athletes during training and competition, which are currently unattainable through traditional laboratory-based techniques. The process of collecting accurate data from complex metabolic parameters usually requires the use of specialised equipment and methods that are often expensive and invasive. This research proposes the novel use of a purpose-built electromagnetic (EM) sensor to non-invasively detect biological markers in humans during exercise. Three parameters were selected for investigation: sweat sodium, blood lactate, and skeletal muscle glycogen. Each of these parameters were selected based on their significance to athletic performance monitoring, as well as their current methods of analysis being impractical for real-time monitoring during exercise. Four human studies and two in-vitro sample-based studies were conducted, accumulating in 140 sweat samples, 523 blood lactate samples, and 21 glycogen samples, collected from a combined total of 71 participants, 56 males, and 15 females. The research presented within this thesis demonstrated that a hairpin EM sensor operating at microwave frequencies could detect and measure changes in sodium concentration within human sweat samples at 1.6 GHz (R2 = 0.862). Further sensor development is required for on-subject monitoring of sweat sodium during exercise (R2 = 0.149), findings suggest this was a result of the microwave sensor’s design, rather than sensing capabilities. Additionally, the sensor was shown to measure blood lactate concentration in untrained participants at 3.4-3.6 GHz (R2 = 0.78), and within endurance-trained participants at 3.2-3.8 GHz (R2 = 0.757). Furthermore, results showed that the sensor could detect changes in glycogen sample concentration at 2.11 GHz (R2 = 0.87) and monitor skeletal muscle glycogen in humans when concentrations were grouped into exercise specific ranges at 2.0-2.25 GHz (R2 = 0.91). This research presents an accurate, cost-effective, and efficient method of detecting biological markers non-invasively and continuously during exercise. With future research and development, a single microwave sensor could ultimately lead to improvements in human performance monitoring, enabling individualised and real-time fuelling strategies during training and competition. Further assessment of this technology is needed within a real-world setting to understand if this remains a feasible solution outside of a controlled environment

What Is Left for Real-Life Lactate Monitoring? Current Advances in Electrochemical Lactate (Bio)Sensors for Agrifood and Biomedical Applications

Monitoring of lactate is spreading from the evident clinical environment, where its role as a biomarker is notorious, to the agrifood ambit as well. In the former, lactate concentration can serve as a useful indicator of several diseases (e.g., tumour development and lactic acidosis) and a relevant value in sports performance for athletes, among others. In the latter, the spotlight is placed on the food control, bringing to the table meaningful information such as decaying product detection and stress monitoring of species. No matter what purpose is involved, electrochemical (bio)sensors stand as a solid and suitable choice. However, for the time being, this statement seems to be true only for discrete measurements. The reality exposes that real and continuous lactate monitoring is still a troublesome goal. In this review, a critical overview of electrochemical lactate (bio)sensors for clinical and agrifood situations is performed. Additionally, the transduction possibilities and different sensor designs approaches are also discussed. The main aim is to reflect the current state of the art and to indicate relevant advances (and bottlenecks) to keep in mind for further development and the final achievement of this highly worthy objective

Evaluating the Possibility of Translating Technological Advances in Non-Invasive Continuous Lactate Monitoring into Critical Care

Lactate is widely measured in critically ill patients as a robust indicator of patient deterioration and response to treatment. Plasma concentrations represent a balance between lactate production and clearance. Analysis has typically been performed with the aim of detecting tissue hypoxia. However, there is a diverse range of processes unrelated to increased anaerobic metabolism that result in the accumulation of lactate, complicating clinical interpretation. Further, lactate levels can change rapidly over short spaces of time, and even subtle changes can reflect a profound change in the patient’s condition. Hence, there is a significant need for frequent lactate monitoring in critical care. Lactate monitoring is commonplace in sports performance monitoring, given the elevation of lactate during anaerobic exercise. The desire to continuously monitor lactate in athletes has led to the development of various technological approaches for non-invasive, continuous lactate measurements. This review aims firstly to reflect on the potential benefits of non-invasive continuous monitoring technology within the critical care setting. Secondly, we review the current devices used to measure lactate non-invasively outside of this setting and consider the challenges that must be overcome to allow for the translation of this technology into intensive care medicine. This review will be of interest to those developing continuous monitoring sensors, opening up a new field of research

Development of electrochemical biosensors and sensors for the determination of interest analytes

Se han puesto a punto varios métodos electroquímicos para la determinación de varios analitos de interés, como lactato, cloruro, bromuro y yoduro utilizando sistemas electródicos serigrafiados (SPEs). Su bajo costo, tamaño pequeño, portabilidad para aplicaciones in situ, así como su facilidad de modificación, les confiere gran versatilidad, para ser usados como transductores en sensores y biosensores electroquímicos con gran precisión y sensibilidad en distintas matrices. Concretamente, se ha desarrollado un biosensor amperométrico para la determinación de lactato, basado en la utilización de la enzima lactato oxidasa. El biosensor ha permitido la determinación de este ácido orgánico en líquidos biológicos como saliva y sudor y en productos alimentarios como vinos. Se incluyen también estudios de los mecanismos de inhibición de las enzimas utilizadas en los biosensores. También se han puesto a punto sensores para la determinación de haluros, que han mostrado su aplicabilidad para su cuantificación en varios tipos de muestras

Rapid Non-Destructive Prediction of Water Activity in Dry-Cured Meat

Water activity (aw) describes the amount of free water available in a matrix for growth of microbiological pathogens and spoilage flora. It is used to predict the safety of food products, and has particular importance for dry-cured meat manufacturers. Results from tests on dry-cured pork (n = 83) demonstrate a high degree of correlation (R2 = 0.909) with current industry standard equipment. System accuracy at the 95% confidence interval (0.0125) is comparable with existing equipment available to industry. However, the added advantage of the microwave sensor to enable rapid and non-destructive measurement means that it could be used for day-to-day monitoring and optimization of products within the dry-cured meat value chain. This would reduce per-product operating costs and waste, in addition to facilitating recipe development (e.g., reduced salt)