EditorialBioimpedance Sensors: Instrumentation,Models, and Applications

David Naranjo-Hernández ,1 Javier Reina-Tosina ,1

Rubén Buend-a ,2 andMart Min 3

1University of Seville, Seville, Spain2University of Boras, Boras, Sweden3Tallinn University of Technology, Tallinn, Estonia

Correspondence should be addressed to David Naranjo-Hernandez; dnaranjo@us.es

Received 13 June 2019; Accepted 18 June 2019; Published 16 July 2019

Copyright © 2019 David Naranjo-Hernandez et al. �is is an open access article distributed under the Creative CommonsAttribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work isproperly cited.

Population aging and the consequent increase in chronicpatients are driving research and development of multiplebiomedical sensor technologies.�ese allow for better moni-toring of people’s health status as well as improved diagnosis,which anticipate a more personalized, preventive, and proac-tive healthcare. Bioimpedance technology offers valuableinformation about tissue/cell physiology and pathology. �isway bioimpedance sensors technology is becoming the basisof novel and noninvasive medical diagnostic devices.

Considering the frequency response of bioimpedanceand the dielectric/conductive properties of the differenttissues it is possible to estimate the diverse compartmentsof the human body, i.e., intracellular and extracellular water,lean mass, fat mass, etc. �e clinical usefulness of bodycomposition analysis by bioimpedance techniques (BIA) hasbeen demonstrated in multiple clinical areas: nephrology,for the optimal management of renal patient excess fluid;nutrition, for a better control of the patient’s nutritionalstatus; also during pregnancy and lactation, as a marker ordirect cause of diseases; during the decision-making processabout a disease, as a complement to the diagnosis andmonitoring of conditions related to the cardiovascular systemor in oncology, among others. Body composition analysis isalso useful in chronic diseases, such as chronic obstructivepulmonary disease, where the loss of body weight and thedecrease in muscle mass are risk factors associated with

increased morbidity and mortality and deterioration in thequality of life.

Changes in fluids and volumes in the thoracic cavityas result of cardiac hemodynamics also produce changes inthe thoracic impedance which allow estimating parametersrelated to themechanical function of the heart such as cardiacoutput, stroke volume, systolic time ratio, and the time ofejection of the le� ventricle or the preejection period. �eapplication of bioimpedance technology in the monitoring ofcardiac parameters is called impedance cardiography (ICG),which has been proven very useful in the diagnosis ofcardiovascular diseases as well as in trauma emergencies.

Bioimpedance measurements allow for the characteri-zation of biological media and organic tissues and havebeen used for detection of edema, diagnosis of skin-relateddiseases, detection of cancerous tissues, and monitoringof ischemia during the transplant process and even as anoninvasive and nonobstructive estimation of blood pressureand blood glucose level. Bioimpedance techniques are alsothe basis of some laboratory devices for themonitoring of cellcultures and the study of the mechanical properties of cells(population, motility, viability, etc.).

�e application of bioimpedance to obtain medicalimages of the inside of the human body using the techniqueknown as electrical impedance tomography (EIT) is aswell noteworthy. Despite the low resolution of the images

HindawiJournal of SensorsVolume 2019, Article ID 5078209, 2 pageshttps://doi.org/10.1155/2019/5078209

2 Journal of Sensors

obtained, EIT has other advantages. It is particularly usefulfor monitoring lung function because lung tissue resistivity isfive times higher than most other so� tissues in the thorax.

Despite the enormous potential of bioimpedance technol-ogy, its application to the clinical practice is still limited anda significant research effort is required to address the futurechallenges: electrodes for continuous monitoring, miniatur-ization of bioimpedance devices, reduction of energy con-sumption, improvement of sensitivity and specificity, detec-tion and correction of artifacts, and application in implants,biosensors, and Lab-on-Chip technologies. �is special issueis aimed at surveying recent advances in bioimpedance sen-sors, devices, and applications. Out of sixteen submissions,five articles were accepted a�er a thorough and rigorous peer-review process. A brief introduction of the published articlesfollows.

�e paper “Orthogonal Multitone Electrical ImpedanceSpectroscopy (OMEIS) for the Study of Fibrosis Induced byActive Cardiac Implants” by E. De Roux et al. is devoted tothe development and implementation of the simultaneousmultitone impedance spectroscopy for detection as well ascharacterization of tissue modifications (fibrosis) around theimplanted electrodes. Such electrodes are in use for both,stimulation and sensing, in implantable cardiac rhythmman-agement devices (pacemakers and defibrillators), includingalso the data acquisition in implantable cardiac monitors.Because the fibrosis reduces susceptibility to stimulation(pacing) and sensibility for sensing, the methods for earlydetection of fibrosis are of great importance.

�e paper “Electrical Impedance-BasedMethodology forLocating Carcinoma Emulators on Breast Models” by M.Gutierrez-Lopez et al. describes the Anomaly Tracking Circlealgorithm. �is is a novel method to estimate the presenceand location of breast carcinoma based on bioimpedancemeasurements through eight Ag/AgCl electrodes uniformlydistributed in a ring configuration. Whereas all differenttechnologies for breast tumor diagnosis have pros and cons,bioimpedance promises a painless, minimally invasive diag-nosis at a low cost. Despite the method being in an early stage(it was evaluated on experimental agar breast models), resultsshow great promise.

A key issue for bioimpedance-based measurement sys-tems is the electrode configuration andmaterial. In the paper“�e Influence of Blood Glucose Meter Resistance Variationon the Performance of a Biosensor with a Gold-CoatedCircuit Board” by K.-Y. Kim et al. the authors present a noveltest strip for blood glucose measurement. �eir contributionis based on the analysis of the effects of glucose oxidase in thereaction zone of gold-coated test strips, which provides a wayof tuning the anodic and reductive peaks, thereby adjustingthe resistance of the electrochemical reaction. To validatetheir approach, an experimental study was conducted inwhich glucose oxidase was combined with standard solutionswith different concentrations and the corresponding currentchanges were measured. Results reveal that the accuracy ofblood glucose measurement can be influenced by adjustingthe resistance of the electrode test strip.

�e work entitled “Simultaneous Recording of ICGand ECG Using Z-RPI Device with Minimum Number of

Electrodes” by A. Hadif et al. describes a device and aprocedure to monitor ICG and electrocardiogram (ECG)signals simultaneously using the same electrodes for bothmeasurements, as opposed to the commonmethodology thatuses separate electrode configurations. �e results presentedshow the viability of the proposed scheme, constituting a stepforward to the development of portable biomedical sensortechnologies.

Last but not least, the paper titled “Fundamentals, RecentAdvances, and Future Challenges in Bioimpedance Devicesfor Healthcare Applications” by D. Naranjo-Hernandez etal. performs a complete review of bioimpedance technologyand its applications in biomedical sensors. A strength of thisstudy is that it provides the reader with a complete view ofthe technology, from the physical and physiological basis ofbioimpedance, through the different mathematical modelsproposed in the literature, to the main instrumentationschemes.�emain problems of bioimpedancemeasurementsare also analyzed, such as the electrode issues or the noiseand artifacts. Since bioimpedance is a very broad and hetero-geneous concept, the fundamentals and results of the mainapplications of bioimpedance are shown in a structured wayin separate sections: BIA, ICG, IET, transthoracic impedancepneumography, skin conductance, and biosensors. A finalsection analyzes recent advances and challenges and futureapplications of bioimpedance.

It is exciting to present this special issue on recentadvances in bioimpedance technology and we hope that thearticles published will promote discussions and inspire newinnovations towards the improvement of people’s health andquality of life.

Conflicts of Interest

�e editors declare that they have no conflicts of interestregarding the publication of this special issue.

Acknowledgments

We would like to thank all the authors for their excellentcontributions and also the reviewers for their valuable helpand constructive criticism.

David Naranjo-HernandezJavier Reina-Tosina

Ruben BuendıaMart Min

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