1,720,978 research outputs found
Optical and Electrical Characterization of Biocompatible Polymeric Lines for Hemodialysis Applications
Full text linkDuring hemodialysis (HD), blood is circulated through an extracorporeal tubing system (bloodline) made of medical-grade polymeric material. Sensors of various types that do not come into contact with blood (optical, electromagnetic, etc.) are applied directly across the bloodline for clinical purposes and for therapy customization. Thus, a detailed knowledge of the bloodline’s physical properties is useful for the development of next-generation HD sensors. In this work, we performed a novel comparative analysis of the materials used by the manufacturers of the bloodlines. We focused on signals and characterization techniques matching those of the abovementioned sensors; consequently, this is an application-specific study of the optical and electrical characterization of bloodline material. Such properties are analyzed and compared for bloodlines from seven different manufacturers by optical absorbance spectroscopy and electrical impedance spectroscopy (EIS). Absorbance spectrum measurements are carried out in the VIS-NIR range. Absorbance spectra are pre-processed and data from both types of analyses are normalized with respect to sample thickness. Optical analysis shows that all bloodlines except one have similarly shaped spectra with slight quantitative differences. In all optical spectra, we find a decreasing trend of specific absorption from 0.14 mm−1 at 400 nm to 0.06 mm−1 at 1000 nm, with an absorption peak at 915 nm. In one case, a large absorption peak centered at ≃600 nm is found. Electrical analysis shows that all bloodlines have the electrical properties of a constant-phase element (CPE), with statistically significant differences in parameters’ values. Estimation of electrical CPE parameters for all bloodline returns a range of 0.942–0.957 for parameter n and a range of 12.41–16.64 for parameter Q0’. In conclusion, we find that, although some statistically significant differences are present, bloodlines from a representative group of manufacturers share similar electrical and optical properties. Therefore, contactless sensing devices developed for HD will work on different bloodlines if a simple recalibration is performed
Lock-in admittance sensor for contactless estimation of fluid conductivity in biocompatible polymeric lines
No full textA New Method for Continuous Relative Blood Volume and Plasma Sodium Concentration Estimation during Hemodialysis
No full textNon-invasive sensing and reliable estimation of physiological parameters are important features of hemodialysis machines, especially for therapy customization (biofeedback). In this work, we present a new method for joint estimation of two important hemodialysis-related physiological parameters: relative blood volume and plasma sodium concentration. Methods: Our method makes use of a non-invasive sensor setup and of a mathematical estimator. The estimator, based on the Kalman filter, allows to merge data from multiple sensors, newly-designed as well as on-board, with modeling knowledge about the hemodialysis process. The system was validated on in-vitro hemodialysis sessions using bovine blood. Results: The estimation error we obtained (0.97±0.73% on relative blood volume and 0.47±0.19 mM on plasmatic sodium) proved to be comparable with that of reference data for both parameters: the system is sufficiently accurate to be relevant in a clinical context. Conclusion: Our system has the potential to provide accurate and important information on the state of a patient undergoing hemodialysis, while only low-cost modifications to the existing on-board sensors are required. Significance: Through improved knowledge of blood parameters during hemodialysis, our method will allow better patient monitoring and therapy customization in hemodialysis
Non-Invasive Estimation of Plasma Sodium Concentration During Hemodialysis via Capacitively-Coupled Electrical Impedance Spectroscopy
Full text linkThis paper presents a compact, low-cost, and non-invasive system for real-time estimation of plasma sodium concentration ([Na]Pl) during a hemodialysis (HD) session with state-of-the-art accuracy. It is based on electrical impedance spectroscopy (EIS) performed with a capacitively-coupled impedance sensing cell and a high-frequency measurement device, both custom-built. The EIS data are processed to infer the resistance of the liquid inside the cell, which is used together with an optical hemoglobin sensor to estimate the [Na]Pl. Validation of the EIS was performed by estimating the conductivity of blood-mimicking fluid (BMF). The complete method was validated using whole bovine blood, comparing the results to those obtained with standard instruments. The system was able to estimate the [Na]Pl with sufficient accuracy (RMS error of 3.0 mol/m3 with respect to reference data) to provide clinically useful information. The proof-of-concept hardware can be converted to a cheap an
Finite-element modeling of time-dependent sodium exchange across the hollow fiber of a hemodialyzer by coupling with a blood pool model
No full textINTRODUCTION:
Hollow fiber models describe the exchange of solutes between blood and dialysate across the membrane of a single fiber of the hemodialysis filter (hemodialyzer). This work aims to develop a new approach to simulate the solute exchange in a hollow fiber in a dynamic and realistic way. Sodium was chosen as our solute of interest due to its importance in hemodialysis as an osmotic regulator.
METHODS:
A 2-dimensional (2D) hollow fiber model based on the finite element method (FEM) is coupled to a simple blood pool model to dynamically update the concentration of the solute entering the dialyzer. The resulting coupled model maintains the geometrical detail of the 2D fiber representation and gains a dynamic, blood-side inlet solute concentration. In vitro dialysis sessions were carried out for model validation, by implementing a combination of blood volume loss and/or sodium concentration steps. Plasmatic sodium concentration was recorded by blood gas sampling. Dialysate inlet and outlet conductivities were continuously recorded.
RESULTS:
Simulated plasmatic sodium concentration was compared with data from the blood gas samples. A mean error of 1.76 ± 1.03 mM was found for the complete dataset, along with a 3.87 mM maximum error. The simulated outlet dialysate sodium concentration was compared with the recorded outlet dialysate conductivity: a very high correlation was found on the whole dataset (R2 = 0.992).
CONCLUSIONS:
Coupling our FEM hollow fiber model to a simple blood pool model proved to be an effective approach for dynamical analysis of the properties of the hemodialyzer
Non-invasive measurement of electrical conductivity of liquids in biocompatible polymeric lines for hemodialysis applications
No full textA non-invasive impedimetric sensing system measuring electrical conductivity of liquids in hemodialysis machines for continuous monitoring applications is introduced. Starting from the typical architecture of the capacitively coupled contactless conductivity approach, we developed an easy-to-use impedance spectroscopy model based on the constant phase element to quantitatively measure the conductivity ofliquids in polymeric lines. We also show the experimental setup to determine the parameters of such a model to better cope with the application constraints. We demonstrated that this approach could be used to design conductivity sensing systems to be fit into the typical dimensions of the standard instrumentation for hemodialysis. Experimental results on saline solutions and blood-mimicking fluid report estimated conductivities with root-mean-square error of ≃0.05 mS/cm, corresponding to about 0.5% of the full scale
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A Differential Optical Sensor for Non-Invasive Real-Time Monitoring of Ultrafiltration Rate in Hemofiltration Therapies
Full text linkHemofiltration (HF) is a group of blood purification therapies used to treat patients with kidney injury. HF works using a process called ultrafiltration (UF) that removes excess liquid accumulated in the patient’s body caused by lack of excretion. UF progress is monitored by the HF machine, but the state-of-the-art method is cumbersome and could be more accurate. In this work, a system composed by two optical sensors is proposed for real-time non-invasive estimation of ultrafiltration rate. This new system is simple, rugged, low-cost and operates on sound theoretical foundations. The sensor system has been tested with two different experimental protocols and showed good correlation between its output and the reference value of the ultrafiltration rate (R2=0.97), as well as improved accuracy compared to the available commercial machine (≃12ml/h). This system also has the potential to simplify the architecture required by critical care blood purification machines to perform UF control
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