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Impedance Tomography (impedance + tomography)

Distribution by Scientific Domains
Medical Sciences66%
Mathematics and Statistics20%

Kinds of Impedance Tomography

  • electrical impedance tomography
    		•

    Selected Abstracts

    Effects of restricted thoracic movement on the regional distribution of ventilation

    ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 6 2010
    S. PULLETZ
    Background: Restricted thoracic movement is often encountered in patients, necessitating mechanical ventilation during surgery or intensive care treatment. High intraabdominal pressure, obesity or thorax rigidity and deformity reduce the chest distensibility and deteriorate the lung function. They render the selection of proper ventilator settings difficult and complicate the weaning process. Electrical impedance tomography (EIT) is currently being proposed as a bedside imaging method for monitoring regional lung ventilation. The objective of our study was to establish whether the effects of decreased chest compliance on regional lung ventilation can be determined by EIT. Methods: Ten healthy male volunteers were studied in our pilot study under three conditions: (1) unrestricted breathing and (2) restricted breathing by abdominal and (3) lower rib cage strapping. The subjects were followed during spontaneous tidal breathing in five postures (sitting, supine, prone, left and right side). EIT and spirometry data were acquired in each condition. Results: The distribution of ventilation in subjects with unrestricted breathing corresponded with the physiologically expected values. In the left and right lateral postures, abdominal and thoracic cage restrictions reduced the ventilation in the dependent lung areas; the non-dependent areas were unaffected. In the prone position, the ventilation of the dependent and non-dependent areas was reduced. The effects of strapping were least pronounced in the supine posture. Conclusions: We conclude that EIT is able to measure changes in the regional distribution of ventilation induced by restricted chest movement and has the potential for optimising artificial ventilation in patients with limited chest compliance of different origins. [source]

    Electrical impedence tomography and heterogeneity of pulmonary perfusion and ventilation in porcine acute lung injury

    ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 10 2009
    A. FAGERBERG
    Background: The heterogeneity of pulmonary ventilation (V), perfusion (Q) and V/Q matching impairs gas exchange in an acute lung injury (ALI). This study investigated the feasibility of electrical impedance tomography (EIT) to assess the V/Q distribution and matching during an endotoxinaemic ALI in pigs. Methods: Mechanically ventilated, anaesthetised pigs (n=11, weight 30,36 kg) were studied during an infusion of endotoxin for 150 min. Impedance changes related to ventilation (ZV) and perfusion (ZQ) were monitored globally and bilaterally in four regions of interest (ROIs) of the EIT image. The distribution and ratio of ZV and ZQ were assessed. The alveolar,arterial oxygen difference, venous admixture, fractional alveolar dead space and functional residual capacity (FRC) were recorded, together with global and regional lung compliances and haemodynamic parameters. Values are mean±standard deviation (SD) and regression coefficients. Results: Endotoxinaemia increased the heterogeneity of ZQ but not ZV. Lung compliance progressively decreased with a ventral redistribution of ZV. A concomitant dorsal redistribution of ZQ resulted in mismatch of global (from ZV/ZQ 1.1±0.1 to 0.83±0.3) and notably dorsal (from ZV/ZQ 0.86±0.4 to 0.51±0.3) V and Q. Changes in global ZV/ZQ correlated with changes in the alveolar,arterial oxygen difference (r2=0.65, P<0.05), venous admixture (r2=0.66, P<0.05) and fractional alveolar dead space (r2=0.61, P<0.05). Decreased end-expiratory ZV correlated with decreased FRC (r2=0.74, P<0.05). Conclusions: EIT can be used to assess the heterogeneity of regional pulmonary ventilation and perfusion and V/Q matching during endotoxinaemic ALI, identifying pivotal pathophysiological changes. [source]

    Monitoring pulmonary perfusion by electrical impedance tomography: an evaluation in a pig model

    ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 2 2009
    A. FAGERBERG
    Background: Electrical impedance tomography (EIT) is a non-invasive technique that generates images of impedance distribution. Changes in the pulmonary content of air and blood are major determinants of thoracic impedance. This study was designed to evaluate EIT in monitoring pulmonary perfusion in a wide range of cardiac output. Methods: Eight anaesthetised, mechanically ventilated pigs were fitted with a 16-electrode belt at the mid-thoracic level to generate EIT images that were analysed to determine pulse-synchronous systolic changes in impedance (,Zsys). Stroke volume (SV) was derived using a pulmonary artery catheter. Reductions in cardiac pre-load, and thus pulmonary perfusion, were induced either by inflating the balloon of a Fogarty catheter positioned in the inferior caval vein or by increasing the positive end-expiratory pressure (PEEP). All measurements were performed in a steady state during a short apnoea. Results: Pulse-synchronous changes in ,Zsys were easily discernable during apnoea. Balloon inflation reduced SV to 36% of the baseline, with a corresponding decrease in ,Zsys to 45% of baseline. PEEP reduced SV and ,Zsys to 52% and 44% of the baseline, respectively. Significant correlations between SV and ,Zsys were demonstrated during all measurements (,=0.62) as well as during balloon inflation (,=0.73) and increased PEEP (,=0.40). A Bland,Altman comparison of relative changes in SV and ,Zsys demonstrated a bias of ,7%, with 95% limits of agreement at ,51% and 36%. Conclusions: EIT provided beat-to-beat approximations of pulmonary perfusion that significantly correlated to a wide range of SV values achieved during both extra and intrapulmonary interventions to change cardiac output. [source]

    Positive end-expiratory pressure optimization using electric impedance tomography in morbidly obese patients during laparoscopic gastric bypass surgery

    ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 7 2006
    K. Erlandsson
    Background:, Morbidly obese patients have an increased risk for peri-operative lung complications and develop a decrease in functional residual capacity (FRC). Electric impedance tomography (EIT) can be used for continuous, fast-response measurement of lung volume changes. This method was used to optimize positive end-expiratory pressure (PEEP) to maintain FRC. Methods:, Fifteen patients with a body mass index of 49 ± 8 kg/m2 were studied during anaesthesia for laparoscopic gastric bypass surgery. Before induction, 16 electrodes were placed around the thorax to monitor ventilation-induced impedance changes. Calibration of the electric impedance tomograph against lung volume changes was made by increasing the tidal volume in steps of 200 ml. PEEP was titrated stepwise to maintain a horizontal baseline of the EIT curve, corresponding to a stable FRC. Absolute FRC was measured with a nitrogen wash-out/wash-in technique. Cardiac output was measured with an oesophageal Doppler method. Volume expanders, 1 ± 0.5 l, were given to prevent PEEP-induced haemodynamic impairment. Results:, Impedance changes closely followed tidal volume changes (R2 > 0.95). The optimal PEEP level was 15 ± 1 cmH2O, and FRC at this PEEP level was 1706 ± 447 ml before and 2210 ± 540 ml after surgery (P < 0.01). The cardiac index increased significantly from 2.6 ± 0.5 before to 3.1 ± 0.8 l/min/m2 after surgery, and the alveolar dead space decreased. PaO2/FiO2, shunt and compliance remained unchanged. Conclusion:, EIT enables rapid assessment of lung volume changes in morbidly obese patients, and optimization of PEEP. High PEEP levels need to be used to maintain a normal FRC and to minimize shunt. Volume loading prevents circulatory depression in spite of a high PEEP level. [source]

    Regional pulmonary pressure volume curves in mechanically ventilated patients with acute respiratory failure measured by electrical impedance tomography

    ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 3 2006
    J. Hinz
    Background:, We hypothized, that in mechanically ventilated patients with acute respiratory failure, regional pressure volume curves differ markedly from conventional global pressure volume curves of the whole lung. Methods:, In nine mechanically ventilated patients with acute respiratory failure during an inspiratory low-flow manoeuvre, conventional global pressure volume curves were registered by spirometry and regional pressure volume curves in up to 912 regions were assessed simultaneously using electrical impedance tomography. We compared the lower (LIP) and upper (UIP) inflection points obtained from the conventional global pressure volume curve and regional pressure volume curves. Results:, We identified from the conventional global pressure volume curves LIP [3,11 (8) cmH2O] in eight patients and UIP [31,39 (33) cmH2O] in three patients. Using electrical impedance tomography (EIT), LIP [3,18 (8) cmH2O] in 54,264 (180) regions and UIP [23,42 (36) cmH2O] in 149,324 (193) regions (range and median) were identified. Lung mechanics measured by conventional global pressure volume curves are similar to the median of regional pressure volume curves obtained by EIT within the tomographic plane. However, single regional pressure volume curves differ markedly with a broad heterogeneity of lower and upper inflection points. Conclusion:, Lower and upper inflection points obtained from conventional global pressure volume curves are not representative of all regions of the lungs. [source]

    The asymptotic behaviour of weak solutions to the forward problem of electrical impedance tomography on unbounded three-dimensional domains

    MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 2 2009
    Michael Lukaschewitsch
    Abstract The forward problem of electrical impedance tomography on unbounded domains can be studied by introducing appropriate function spaces for this setting. In this paper we derive the point-wise asymptotic behaviour of weak solutions to this problem in the three-dimensional case. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    The factorization method for a class of inverse elliptic problems

    MATHEMATISCHE NACHRICHTEN, Issue 3 2005
    Andreas Kirsch
    Abstract In this paper the factorization method from inverse scattering theory and impedance tomography is extended to a class of general elliptic differential equations in divergence form. The inverse problem is to determine the interface ,, of an interior change of the material parameters from the Neumann-Dirichlet map. Since absorption is allowed a suitable combination of the real and imaginary part of the Neumann-Dirichlet map is needed to explicitely characterize , by the data. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    3D EIT for breast cancer imaging: System, measurements, and reconstruction

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008
    Gang Ye
    Abstract Electrical impedance tomography (EIT) is a developing imaging modality for early detection of breast cancer. In an EIT system, a low-frequency current is applied sequentially between different electrode pairs while voltage measurements are made at other electrodes to arrive at the electrical impedance values. The set of impedance measurement data is then computed to produce a 3D electrical conductivity map of the volume to be imaged. In this work, the design, measurements, and inversion of a full 3D EIT system are discussed. Experimentally determined EIT images of phantom objects are presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3261,3271, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23932 [source]

    2D EIT for biomedical imaging: Design, measurement, simulation, and image reconstruction

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2007
    Kim Hwa Lim
    Abstract A 2D electrical impedance tomography (EIT) system has been developed at Duke University as an experimental system to test the forward and inverse algorithms for EIT application. The forward model is based on the 2nd-order finite element method (FEM), while the image reconstruction is based on the distorted Born iterative method (DBIM). The major contributions of this work are the application of the higher-order FEM as a forward solver, and the DBIM as an inverse solver to the integrated EIT system. The forward model has been validated with the measured data to within 0.5% accuracy. Excellent images have been reconstructed with these collected EIT data sets. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2989,2998, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22938 [source]

    Regional ventilation distribution in non-sedated spontaneously breathing newborns and adults is not different

    PEDIATRIC PULMONOLOGY, Issue 9 2009
    Andreas Schibler MD
    Abstract Background: In adults, ventilation is preferentially distributed towards the dependent lung. A reversal of the adult pattern has been observed in infants using radionuclide ventilation scanning. But these results have been obtained in infants and children with lung disease. In this study we investigate whether healthy infants have a similar reverse pattern of ventilation distribution. Study Design: Measurement of regional ventilation distribution in healthy newborn infants during non-REM sleep in comparison to adults. Methods: Twenty-four healthy newborns and 13 adults were investigated with electrical impedance tomography (EIT) in supine and prone position. Regional ventilation distribution was assessed with profiles of relative impedance change. The phase lag between dependent and non-dependent ventilation was calculated as a measure of asynchronous ventilation. Results: In newborns and adults the geometric center of ventilation was centrally located in the lung at 52.2,±,6.2% from anterior to posterior and at 50.5,±,14.7%, respectively. Using impedance profiles, ventilation was equally distributed to the dependent and non-dependent lung regions in newborns. Ventilation distribution in adults was similar. Phase lag characteristics of the impedance signal showed that infants had slower emptying of the dependent lung than adults. Conclusion: The speculated reverse pattern of regional ventilation distribution in healthy infants compared to adults could not be demonstrated. Gravity had little effect on ventilation distribution in both infants and adults measured in supine and prone position. Pediatr Pulmonol. 2009; 44:851,858. © 2009 Wiley-Liss, Inc. [source]

    Lung Function Tests in Neonates and Infants with Chronic Lung Disease: Global and Regional Ventilation Inhomogeneity

    PEDIATRIC PULMONOLOGY, Issue 2 2006
    J. Jane Pillow FRACP
    Abstract This review considers measurement of global and regional ventilation inhomogeneity (VI) in infants and young children with acute neonatal respiratory disorders and chronic lung disease of infancy (CLDI). We focus primarily on multiple-breath inert gas washout (MBW) and electrical impedance tomography (EIT). The literature is critically reviewed and the relevant methods, equipment, and studies are summarized, including the limitations and strengths of individual techniques, together with the availability and appropriateness of any reference data. There has been a recent resurgence of interest in using MBW to monitor lung function within individuals and between different groups. In the mechanically ventilated, sedated, and paralyzed patient, VI indices can identify serial changes occurring following exogenous surfactant. Similarly, global VI indices appear to be increased in infants with CLDI and to differentiate between infants without lung disease and those with mild, moderate, and severe lung disease following preterm birth. While EIT is a relatively new technique, recent studies suggest that it is feasible in newborn infants, and can quantitatively identify changes in regional lung ventilation following alterations to ventilator settings, positive end expiratory pressure (PEEP), and administration of treatments such as surfactant. As such, EIT represents one of the more exciting prospects for continuous bedside pulmonary monitoring. For both techniques, there is an urgent need to establish guidelines regarding data collection, analysis, and interpretation in infants both with and without CLDI. © 2005 Wiley-Liss, Inc. [source]