Relaxation differences using EIS through bronchoscopy of healthy and pathological lung tissue.

The use of electrical impedance spectroscopy for lung tissue differentiation is an opportunity for the improvement of clinical diagnosis. The aim of this work is to distinguish among different lung tissue states by evaluating the differences among impedance spectrum parameters between two separate frequencies (15 kHz and 307 kHz) in the beta dispersion region. In previous studies we have used single frequency measurements for tissue differentiation. Differences (P < 0.05) are found between those tissues that undergo an increase in tissue density (neoplasm and fibrosis) and those tissues that lead to tissue destruction (emphysema). Electrical impedance spectroscopy shows its utility for lung tissue differentiation for diagnosis improvement among pathologies with different tissue structure. Further studies are necessary for the differentiation among those tissue states that are more similar to each other.Clinical Relevance- Expand the diagnostic tools currently available in bronchoscopy by using minimally-invasive bioimpedance measurements to differentiate between lung patterns.

Differentiation using minimally-invasive bioimpedance measurements of healthy and pathological lung tissue through bronchoscopy.

Purpose: To use minimally-invasive transcatheter electrical impedance spectroscopy measurements for tissue differentiation among healthy lung tissue and pathologic lung tissue from patients with different respiratory diseases (neoplasm, fibrosis, pneumonia and emphysema) to complement the diagnosis at real time during bronchoscopic procedures. Methods: Multi-frequency bioimpedance measurements were performed in 102 patients. The two most discriminative frequencies for impedance modulus (|Z|), phase angle (PA), resistance (R) and reactance (Xc) were selected based on the maximum mean pair-wise Euclidean distances between paired groups. One-way ANOVA for parametric variables and Kruskal-Wallis for non-parametric data tests have been performed with post-hoc tests. Discriminant analysis has also been performed to find a linear combination of features to separate among tissue groups. Results: We found statistically significant differences for all the parameters between: neoplasm and pneumonia (p < 0.05); neoplasm and healthy lung tissue (p < 0.001); neoplasm and emphysema (p < 0.001); fibrosis and healthy lung tissue (p ≤ 0.001) and pneumonia and healthy lung tissue (p < 0.01). For fibrosis and emphysema (p < 0.05) only in |Z|, R and Xc; and between pneumonia and emphysema (p < 0.05) only in |Z| and R. No statistically significant differences (p > 0.05) are found between neoplasm and fibrosis; fibrosis and pneumonia; and between healthy lung tissue and emphysema. Conclusion: The application of minimally-invasive electrical impedance spectroscopy measurements in lung tissue have proven to be useful for tissue differentiation between those pathologies that leads increased tissue and inflammatory cells and those ones that contain more air and destruction of alveolar septa, which could help clinicians to improve diagnosis.

Minimally Invasive Real-Time Electrical Impedance Spectroscopy Diagnostic Tool for Lung Parenchyma Pathologies.

Electrical Impedance Spectroscopy has already demonstrated the ability to distinguish different tissues types, or tumors from normal tissue, or tissues displaying diverse degrees of pathology. When applying the technique, however, the necessity to make contact with the tissue often constitutes a practical limitation. Electrical Impedance Imaging (EIT), or in a broader sense, regional impedance assessment, struggle to assess different tissue conditions out of measurements from the surface of the body. But sensitivity is very small even for tissue a few centimeters under the skin, and in-vivo measurements are often not viable.The lung offer a third approximation by introducing a catheter though a bronchoscope, which is a routine clinical procedure. Measurements have been obtained by using 3 or 4-electrode techniques and allow us to distinguish, at least, fibrotic, emphysema or neoplastic regions from normal parenchyma. New instrumental developments, clinical measurements and preliminary results are presented and discussed.

Usefulness of bioelectrical impedance analysis for monitoring patients with refractory ascites

Background: bioelectrical impedance analysis is a technique for the determination of the hydropic component. The hydropic component, determined by blood volume, could be a reflection of the hemodynamic situation. This study aimed to evaluate the usefulness of peripheral bioelectrical impedance analysis (BIA) for the prediction of hemodynamic changes in large-volume paracentesis and prognosis. Methods: this was a proof-of-concept prospective study of 14 patients with liver cirrhosis and refractory ascites. Peripheral bioimpedance was measured three times using a portable device, IVOL(R), before and after large-volume paracentesis, at different frequencies (5, 10, 20, 50, 100 and 200 kHz). Consequently, resistance, reactance and phase angle were obtained, both pre- and post-paracentesis (the difference between them was defined as Δ). Results: the mean age of patients was 62.2 +/- 9.6 years, the Child-Pugh was 8.4 +/- 1.3 and the MELD score was 15.2 +/- 3.9. A direct correlation between the extraction of ascitic fluid and Δresistance (10 kHz [r = 0.722; n = 12; p = 0.008], 20 kHz [r = 0.658; n = 12; p = 0.020] and 50 kHz [r = 0.519; n = 14; p = 0.057]) was observed. The presence of edema was related to lower values of both pre-paracentesis resistance (10 Hz [23.9 +/- 8 vs 32.2 +/- 4; p = 0.043]) and phase angle (5 kHz [-1.9+/- 2.8 vs 5.9 +/- 7.3; p = 0.032]). Pre-paracentesis phase angle was directly correlated with the decline in blood pressure after paracentesis at lower frequencies (5 kHz [r = 0.694; n = 13; p = 0.008] and 10 kHz [r = 0.661; n = 13; p = 0.014]). Lower frequencies of Δphase-angle impacted on patient prognosis (5 kHz [-8.6 +/- 5 vs -2.5 +/- 2.7; p = 0.021]), patients with Δphase-angle 5 kHz > -4 had a higher rate of mortality (83.3% [5/6] vs 0% [0/6]; logRank 7.306, p = 0.007). Δresistance values were associated with overt HE at six months (10 kHz [4.9 +/- 2.5 vs -0.4 +/- 4.7; p = 0.046]). Conclusions: in conclusion, a significant correlation between peripheral impedance and hemodynamic changes was found. Impedance was also significantly related to prognosis and overt hepatic encephalopathy

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Usefulness of bioelectrical impedance analysis for monitoring patients with refractory ascites.

BACKGROUND: bioelectrical impedance analysis is a technique for the determination of the hydropic component. The hydropic component, determined by blood volume, could be a reflection of the hemodynamic situation. This study aimed to evaluate the usefulness of peripheral bioelectrical impedance analysis (BIA) for the prediction of hemodynamic changes in large-volume paracentesis and prognosis. METHODS: this was a proof-of-concept prospective study of 14 patients with liver cirrhosis and refractory ascites. Peripheral bioimpedance was measured three times using a portable device, IVOL®, before and after large-volume paracentesis, at different frequencies (5, 10, 20, 50, 100 and 200 kHz). Consequently, resistance, reactance and phase angle were obtained, both pre- and post-paracentesis (the difference between them was defined as Δ). RESULTS: the mean age of patients was 62.2 ± 9.6 years, the Child-Pugh was 8.4 ± 1.3 and the MELD score was 15.2 ± 3.9. A direct correlation between the extraction of ascitic fluid and Δresistance (10 kHz [r = 0.722; n = 12; p = 0.008], 20 kHz [r = 0.658; n = 12; p = 0.020] and 50 kHz [r = 0.519; n = 14; p = 0.057]) was observed. The presence of edema was related to lower values of both pre-paracentesis resistance (10 Hz [23.9  8 vs 32.2  4; p = 0.043]) and phase angle (5 kHz [-1.9 2.8 vs 5.9  7.3; p = 0.032]). Pre-paracentesis phase angle was directly correlated with the decline in blood pressure after paracentesis at lower frequencies (5 kHz [r = 0.694; n = 13; p = 0.008] and 10 kHz [r = 0.661; n = 13; p = 0.014]). Lower frequencies of Δphase-angle impacted on patient prognosis (5 kHz [-8.6 ± 5 vs -2.5 ± 2.7; p = 0.021]), patients with Δphase-angle 5 kHz > -4 had a higher rate of mortality (83.3% [5/6] vs 0% [0/6]; logRank 7.306, p = 0.007). Δresistance values were associated with overt HE at six months (10 kHz [4.9  2.5 vs -0.4  4.7; p = 0.046]). CONCLUSIONS: in conclusion, a significant correlation between peripheral impedance and hemodynamic changes was found. Impedance was also significantly related to prognosis and overt hepatic encephalopathy.

Design and implementation of a microelectrode assembly for use on noncontact in situ electroporation of adherent cells.

In situ electroporation of adherent cells provides significant advantages with respect to electroporation systems for suspension cells, such as causing minimal stress to cultured cells and simplifying and saving several steps within the process. In this study, a new electrode assembly design is shown and applied to in situ electroporate adherent cell lines growing in standard multiwell plates. We designed an interdigitated array of electrodes patterned on copper with printed circuit board technology and covered with nickel/gold. Small interelectrode distances were used to achieve effective electroporation with low voltages. Epoxy-based microseparators were constructed to avoid direct contact with the cells and to create more uniform electric fields. The device was successful in the electropermeabilization of two different adherent cell lines, C2C12 and HEK 293, as assessed by the intracellular delivery of the fluorescent dextran FD20S. Additionally, as a collateral effect, we observed cell electrofusion in HEK 293 cells, thus making this device also useful for performing cell fusion. In summary, we show the effectiveness of this minimally invasive device for electroporation of adherent cells cultured in standard multiwell plates. The cheap technologies used in the fabrication process of the electrode assembly indicate potential use as a low-cost, disposable device.

Automatic system for electroporation of adherent cells growing in standard multi-well plates.

In this study an automatic system is presented to perform electroporation, also known as electropermeabilization, on adherent cells. It is an intention of this system to apply electric field pulses directly to cells growing in standard multi-well plates as a step forward to include this technique in standard laboratory protocols. An interdigitated microelectrode assembly constructed with Printed Circuit Board (PCB) is placed closely above the cell monolayer, and in order to avoid direct contact with cells, small micro-separators were included in the structure. Additionally, distribution of current density was modified by filling the gap between adjacent electrodes with a non conductive material as predicted by electric field simulations. This modification helps to concentrate the electric field intensity in the region where cells are present. The device was tested using C2C12 cell line growing adhered in 24 multi-well plates and fluorescent labeled dextran FD20S as the molecule to be delivered. Successful transfection was observed with minimal invasiveness of the operation reducing the stress caused to cells.

Diagnóstico de rinosinusitis fúngica no invasiva en el Hospital General Docente Dr Agostinho Neto de Guantánamo / Diagnosis of fungal, noninvasive rhinosinusitis at the General Teaching Hospital Dr Agostinho Neto Guantanamo

Se revisan las historias clínicas de 6 pacientes con rinosinusitis maxilar fúngica crónica no invasiva pertenecientes al Hospital General Docente Dr Agostinho Neto de Guantánamo en el período comprendido entre enero de 2010 y diciembre de 2011, con el objetivo de evaluar: cuadro clínico, resultados imagenológicos, hallazgos quirúrgicos e histopatológicos para precisar la categoría diagnóstica y los resultados del seguimiento al alta. En el cuadro clínico de estos pacientes no se encuentran diferencias respecto a otras enfermedades crónicas rinosinusales. Las imágenes de calcificaciones y signos de masa expansiva sinusal vistos en la tomografía axial computarizada hicieron sospechar la enfermedad. El único patógeno resultó ser el Aspergillus y es aislado por histopatología en 4 pacientes. Se diagnostican 5 pacientes en la categoría de rinosinusitis fúngica alérgica y uno en bola fúngica o micetoma, todos evaluados de satisfactorio durante el seguimiento al alta hospitalaria (AU)

The medical records are reviewed by doctors ,6 patients with noninvasive ,fungal and chronic maxillary rhinosinusitis belonging to the Hospital Dr Agostinho Neto Guantanamo from January 2010 to December 2011, with the objective of assessing: clinical, imaging results, surgical and histopathologic findings to refine the diagnostic category and monitoring results at discharge. In the clinical manifestations of these patients are no differentiated from other chronic rhinosinusal. The images of calcifications and signs of sinus expansive mass seen on the CT scan made possible the observation of the disease. The only pathogen the Aspergillum is isolated by histopathology and in 4 patients. Five patients were diagnosed in the category of allergic fungal rhinosinusitis and one fungus ball or myeloma, all evaluated as satisfactory following to hospital discharge (AU)

Caracterización clínico-epidemiológica de roncadores habituales / Clinical and epidemiological characterization of habitual snorers

Se realiza una investigación en 55 roncadores habituales en el período comprendido entre enero y diciembre de 2011, en el servicio de Otorrinolaringología del Hospital General Docente Dr Agostinho Neto con el objetivo de caracterizar los aspectos clínicos y epidemiológicos de los mismos. Se contempló la edad, sexo, hábito de fumar, e índice de masa corporal, entre otras. Se determinaron características clínicas, tales como trastornos cognitivos, del sueño, sexuales; síntomas y examen físico otorrinolaringológicos y registros electrocardiográficos. Prevalece el grupo de edad de 51-60 años y el sexo masculino. Los síntomas más frecuentes son el ardor faríngeo y obstrucción nasal. En el examen físico predominaron: faringe, afecciones combinadas, y en fosas nasales, la desviación septal. Más de la mitad de los roncadores eran obesos con afecciones cardiovasculares. El hábito de fumar, ingestión de bebidas alcohólicas, psicofármacos y antihistamínicos no modificaron aparentemente los trastornos cognitivos ni los del sueño (AU)

A research is conducted in 55 habitual snorers from January to December 2011, in the Department of Otolaryngology, at the General Teaching Hospital Dr Agostinho Neto in order to characterize, clinical and epidemiological aspects. Variables were studied: the age, sex, smoking, and body mass index, among others. Clinical characteristics were determined, such as cognitive disorders, sleep, sex, symptoms , physical examination and electrocardiographic ENT, Prevailing age of group 51-60 years and males. The most common symptoms are a burning throat and nasal obstruction. On physical examination predominated: pharynx, diseases combined, and nostrils, septal deviation. Over half of the patients were obese snorers with cardiovascular disease. Smoking, alcohol consumption, psychiatric drugs and antihistamines not change apparently cognitive disorders nor sleep (AU)

Comparison of segmental with whole-body impedance measurements in peritoneal dialysis patients.

Segmental impedance measurements were obtained using nine electrode configurations in 21 male patients undergoing peritoneal dialysis PD before and after the fluid drainage. For each segment we analyzed the impedance Z and the impedance divided by the height H of the patient Z/H. Our objective was to compare different segmental measurements with whole-body measurements in peritoneal dialysis. The Wilcoxon test was used to analyze the change in impedance produced by a PD session. Pearson or Spearman correlation coefficients were used for continuous or discrete variables, respectively. Statistical significance was set at P<0.05. Similar results were obtained for Z and Z/H. The correlation coefficients between the real R and imaginary X(c) parts of segmental impedances after drainage were within the expected range for healthy population (0.46-0.70), but not before drainage for the abdomen (0.34) and the upper part of the leg (0.24). The correlation between the real part of whole-body and the real part of longitudinal segments in the limbs was high (r=0.807-0.879). Furthermore, the imaginary part of whole-body showed a high correlation with the imaginary part of all longitudinal segments (r=0.856-0.931). The high contribution of arm and leg impedances in the whole-body impedance produced high correlation between whole-body and segmental measurements in legs and arms. In agreement with other previous studies, a significant increase of the arm resistance was detected after fluid drainage. The drainage of fluids in PD patients produced significant changes in the measured real parts of impedance in all measured segments, but only the measurement in the abdomen showed a significant positive correlation (r=0.533) with the extracted fluid volume. This low correlation indicates that the individual assessment of fluid volumes using segmental measurements will be highly inaccurate.

Reconstruction of the shape of conductivity spectra using differential multi-frequency magnetic induction tomography.

Magnetic induction tomography (MIT) of biological tissue is used for the reconstruction of the complex conductivity distribution kappa inside the object under investigation. It is based on the perturbation of an alternating magnetic field caused by the object and can be used in all applications of electrical impedance tomography (EIT) such as functional lung monitoring and assessment of tissue fluids. In contrast to EIT, MIT does not require electrodes and magnetic fields can also penetrate non-conducting barriers such as the skull. As in EIT, the reconstruction of absolute conductivity values is very difficult because of the method's sensitivity to numerical errors and noise. To overcome this problem, image reconstruction in EIT is often done differentially. Analogously, this concept has been adopted for MIT. Two different methods for differential imaging are applicable. The first one is state-differential, for example when the conductivity change between inspiration and expiration in the lung regions is being detected. The second one is frequency-differential, which is of high interest in motionless organs like the brain, where a state-differential method cannot be applied. An equation for frequency-differential MIT was derived taking into consideration the frequency dependence of the sensitivity matrix. This formula is valid if we can assume that only small conductivity changes occur. In this way, the non-linear inverse problem of MIT can be approximated by a linear one (depending only on the frequency), similar to in EIT. Keeping this limitation in mind, the conductivity changes between one or more reference frequencies and several measurement frequencies were reconstructed, yielding normalized conductivity spectra. Due to the differential character of the method, these spectra do not provide absolute conductivities but preserve the shape of the spectrum. The validity of the method was tested with artificial data generated with a spherical perturbation within a conducting cylinder as well as for real measurement data. The measurement data were obtained from a potato immersed in saline. The resulting spectra were compared with reference measurements and the preservation of the shape of the spectra was analyzed.

Transmural versus nontransmural in situ electrical impedance spectrum for healthy, ischemic, and healed myocardium.

Electrical properties of myocardial tissue are anisotropic due to the complex structure of the myocardial fiber orientation and the distribution of gap junctions. For this reason, measured myocardial impedance may differ depending on the current distribution and direction with respect to myocardial fiber orientation and, consequently, according to the measurement method. The objective of this study is to compare the specific impedance spectra of the myocardium measured using two different methods. One method consisted of transmural measurements using an intracavitary catheter and the other method consisted of nontransmural measurements using a four-needle probe inserted into the epicardium. Using both methods, we provide the in situ specific impedance spectrum (magnitude and phase angle) of normal, ischemic, and infarcted pig myocardium tissue from 1 kHz to 1 MHz. Magnitude spectra showed no significant differences between the measurement techniques. However, the phase angle spectra showed significant differences for normal and ischemic tissues according to the measurement technique. The main difference is encountered after 60 min of acute ischeimia in the phase angle spectrum. Healed myocardial tissue showed a small and flat phase angle spectrum in both methods due tothe low content of cells in the transmural infarct scar. In conclusion, both transmural and nontransmural measurements of phase angle spectrum allow the differentiation among normal, ischemic, and infarcted tissue.

Biological tissue characterization by magnetic induction spectroscopy (MIS): requirements and limitations.

Magnetic induction spectroscopy (MIS) aims at the contactless measurement of the passive electrical properties (PEP) sigma, epsilon, and mu of biological tissues via magnetic fields at multiple frequencies. Whereas previous publications focus on either the conductive or the magnetic aspect of inductive measurements, this article provides a synthesis of both concepts by discussing two different applications with the same measurement system: 1) monitoring of brain edema and 2) the estimation of hepatic iron stores in certain pathologies. We derived the equations to estimate the sensitivity of MIS as a function of the PEP of biological objects. The system requirements and possible systematic errors are analyzed for a MIS-channel using a planar gradiometer (PGRAD) as detector. We studied 4 important error sources: 1) moving conductors near the PGRAD; 2) thermal drifts of the PGRAD-parameters; 3) lateral displacements of the PGRAD; and 4) phase drifts in the receiver. All errors were compared with the desirable resolution. All errors affect the detected imaginary part (mainly related to sigma) of the measured complex field much less than the real part (mainly related to epsilon and mu). Hence, the presented technique renders possible the resolution of (patho-) physiological changes of the electrical conductivity when applying highly resolving hardware and elaborate signal processing. Changes of the magnetic permeability and permittivity in biological tissues are more complicated to deal with and may require chopping techniques, e.g., periodic movement of the object.

Propagation of measurement noise through backprojection reconstruction in electrical impedance tomography.

A framework to analyze the propagation of measurement noise through backprojection reconstruction algorithms in electrical impedance tomography (EIT) is presented. Two measurement noise sources were considered: noise in the current drivers and in the voltage detectors. The influence of the acquisition system architecture (serial/semi-parallel) is also discussed. Three variants of backprojection reconstruction are studied: basic (unweighted), weighted and exponential backprojection. The results of error propagation theory have been compared with those obtained from simulated and experimental data. This comparison shows that the approach provides a good estimate of the reconstruction error variance. It is argued that the reconstruction error in EIT images obtained via backprojection can be approximately modeled as a spatially nonstationary Gaussian distribution. This methodology allows us to develop a spatial characterization of the reconstruction error in EIT images.

Sensitivity maps for low-contrast perturbations within conducting background in magnetic induction tomography.

Magnetic induction tomography (MIT) is a contactless method for mapping the electrical conductivity of tissue by measuring the perturbation of an alternating magnetic field with appropriate receiver coils. Reconstruction algorithms so far suggested for biomedical applications are based on weighted backprojection, hence requiring tube-shaped zones of sensitivity between excitation coils and receiving coils, the sensitivity being essentially zero outside this 'projection beam'. This condition is met for conducting perturbations in empty space and for some special configurations of insulators in saline. In biological structures, however, perturbations with low conductivity contrast are embedded into a bulk conductor. The respective sensitivity distribution was investigated and quantified theoretically and experimentally by displacing a conducting (agar, 8 S m(-1)) and an insulating sphere within a saline tank (4 S m(-1)). In contrast to the case in the empty space the sensitivity is not confined to a tube but even increases outside the 'projection beam'. The difference can be explained by the interaction of bulk currents with the perturbing object. This effect invalidates backprojection and hence the solution of the complete inverse eddy-current problem is suggested.