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Cabezudo Ballesteros S, Sanabria Carretero P, Reinoso Barbero F. Review of electrical impedance tomography in the pediatric patient. REVISTA ESPANOLA DE ANESTESIOLOGIA Y REANIMACION 2024:S2341-1929(24)00060-X. [PMID: 38458492 DOI: 10.1016/j.redare.2024.03.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 08/28/2023] [Indexed: 03/10/2024]
Abstract
Electrical impedance tomography (EIT) is a new method of monitoring non-invasive mechanical ventilation, at the bedside and useful in critically ill patients. It allows lung monitoring of ventilation and perfusion, obtaining images that provide information on lung function. It is based on the physical principle of impedanciometry or the body's ability to conduct an electrical current. Various studies have shown its usefulness both in adults and in pediatrics in respiratory distress syndrome, pneumonia and atelectasis in addition to pulmonary thromboembolism and pulmonary hypertension by also providing information on pulmonary perfusion, and may be very useful in perioperative medicine; especially in pediatrics avoiding repetitive imaging tests with ionizing radiation.
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Affiliation(s)
| | - P Sanabria Carretero
- Servicio de Anestesia y Reanimación, Hospital Universitario La Paz, Madrid, Spain
| | - F Reinoso Barbero
- Servicio de Anestesia y Reanimación, Hospital Universitario La Paz, Madrid, Spain
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Sacks M, Byrne DP, Herteman N, Secombe C, Adler A, Hosgood G, Raisis AL, Mosing M. Electrical impedance tomography to measure lung ventilation distribution in healthy horses and horses with left-sided cardiac volume overload. J Vet Intern Med 2021; 35:2511-2523. [PMID: 34347908 PMCID: PMC8478054 DOI: 10.1111/jvim.16227] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 07/01/2021] [Accepted: 07/13/2021] [Indexed: 12/24/2022] Open
Abstract
Background Left‐sided cardiac volume overload (LCVO) can cause fluid accumulation in lung tissue changing the distribution of ventilation, which can be evaluated by electrical impedance tomography (EIT). Objectives To describe and compare EIT variables in horses with naturally occurring compensated and decompensated LCVO and compare them to a healthy cohort. Animals Fourteen adult horses, including university teaching horses and clinical cases (healthy: 8; LCVO: 4 compensated, 2 decompensated). Methods In this prospective cohort study, EIT was used in standing, unsedated horses and analyzed for conventional variables, ventilated right (VAR) and left (VAL) lung area, linear‐plane distribution variables (avg‐max VΔZLine, VΔZLine), global peak flows, inhomogeneity factor, and estimated tidal volume. Horses with decompensated LCVO were assessed before and after administration of furosemide. Variables for healthy and LCVO‐affected horses were compared using a Mann‐Whitney test or unpaired t‐test and observations from compensated and decompensated horses are reported. Results Compared to the healthy horses, the LCVO cohort had significantly less VAL (mean difference 3.02; 95% confidence interval .77‐5.2; P = .02), more VAR (−1.13; −2.18 to −.08; P = .04), smaller avg‐max VΔZLLine (2.54; 1.07‐4.00; P = .003) and VΔZLLine (median difference 5.40; 1.71‐9.09; P = .01). Observation of EIT alterations were reflected by clinical signs in horses with decompensated LCVO and after administration of furosemide. Conclusions and Clinical Importance EIT measurements of ventilation distribution showed less ventilation in the left lung of horses with LCVO and might be useful as an objective assessment of the ventilation effects of cardiogenic pulmonary disease in horses.
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Affiliation(s)
- Muriel Sacks
- School of Veterinary Medicine, Murdoch University, Perth, Australia
| | - David P Byrne
- School of Veterinary Medicine, Murdoch University, Perth, Australia
| | - Nicolas Herteman
- Equine Clinic, Department for Equine Medicine, Vetsuisse Faculty, University of Zurich, Zürich, Switzerland
| | - Cristy Secombe
- School of Veterinary Medicine, Murdoch University, Perth, Australia
| | - Andy Adler
- Systems and Computer Engineering, Carleton University, Ottawa, Canada
| | - Giselle Hosgood
- School of Veterinary Medicine, Murdoch University, Perth, Australia
| | - Anthea L Raisis
- School of Veterinary Medicine, Murdoch University, Perth, Australia
| | - Martina Mosing
- School of Veterinary Medicine, Murdoch University, Perth, Australia
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Frerichs I, Vogt B, Wacker J, Paradiso R, Braun F, Rapin M, Caldani L, Chételat O, Weiler N. Multimodal remote chest monitoring system with wearable sensors: a validation study in healthy subjects. Physiol Meas 2020; 41:015006. [DOI: 10.1088/1361-6579/ab668f] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Frerichs I, Zhao Z. Electrical impedance tomography for chest imaging in acute respiratory failure. Eur Respir J 2019; 54:54/4/1901497. [PMID: 31672905 DOI: 10.1183/13993003.01497-2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Accepted: 07/30/2019] [Indexed: 11/05/2022]
Affiliation(s)
- Inéz Frerichs
- Dept of Anaesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Zhanqi Zhao
- Dept of Biomedical Engineering, Fourth Military Medical University, Xi'an, China.,Institute of Technical Medicine, Furtwangen University, Villingen-Schwenningen, Germany
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Santos SA, Wembers CC, Horst K, Pfeifer R, Simon TP, Pape HC, Hildebrand F, Czaplik M, Leonhardt S, Teichmann D. Monitoring lung contusion in a porcine polytrauma model using EIT: an application study. Physiol Meas 2017. [DOI: 10.1088/1361-6579/aa7985] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Zhang J, Patterson R. Variability in EIT Images of Lung Ventilation as a Function of Electrode Planes and Body Positions. Open Biomed Eng J 2014; 8:35-41. [PMID: 25110529 PMCID: PMC4126188 DOI: 10.2174/1874120701408010035] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2013] [Revised: 04/24/2014] [Accepted: 04/25/2014] [Indexed: 11/22/2022] Open
Abstract
This study is aimed at investigating the variability in resistivity changes in the lung region as a function of air volume, electrode plane and body position. Six normal subjects (33.8 ± 4.7 years, range from 26 to 37 years) were studied using the Sheffield Electrical Impedance Tomography (EIT) portable system. Three transverse planes at the level of second intercostal space, the level of the xiphisternal joint, and midway between upper and lower locations were chosen for measurements. For each plane, sixteen electrodes were uniformly positioned around the thorax. Data were collected with the breath held at end expiration and after inspiring 0.5, 1.0, or 1.5 liters of air from end expiration, with the subject in both the supine and sitting position. The average resistivity change in five regions, two 8x8 pixel local regions in the right lung, entire right, entire left and total lung regions, were calculated. The results show the resistivity change averaged over electrode positions and subject positions was 7-9% per liter of air, with a slightly larger resistivity change of 10 % per liter air in the lower electrode plane. There was no significant difference (p>0.05) between supine and sitting. The two 8x8 regions show a larger inter individual variability (coefficient of variation, CV, is from 30% to 382%) compared to the entire left, entire right and total lung (CV is from 11% to 51%). The results for the global regions are more consistent. The large inter individual variability appears to be a problem for clinical applications of EIT, such as regional ventilation. The variability may be mitigated by choosing appropriate electrode plane, body position and region of interest for the analysis.
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Affiliation(s)
- Jie Zhang
- Division of Medical Physics, Department of Radiology, University of Kentucky, Lexington, KY 40536, USA
| | - Robert Patterson
- Department of Physical Medicine and Rehabilitation, University of Minnesota, Minneapolis, MN 55455, USA
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Skrabal F, Pichler GP, Gratze G, Holler A. Adding "hemodynamic and fluid leads" to the ECG. Part I: the electrical estimation of BNP, chronic heart failure (CHF) and extracellular fluid (ECF) accumulation. Med Eng Phys 2014; 36:896-904; discussion 896. [PMID: 24793409 DOI: 10.1016/j.medengphy.2014.03.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 03/12/2014] [Accepted: 03/25/2014] [Indexed: 11/28/2022]
Abstract
OBJECTIVES In primary care the diagnosis of CHF and ECF accumulation is no triviality. We aimed to predict plasma BNP, CHF and ECF accumulation with segmental impedance spectroscopy while using and extending the electrodes of the conventional electrocardiography. METHODS Three combined multiple electrodes were added to the 15 lead ECG for segmental impedance spectroscopy and for measuring the maximal rate of segmental fluid volume change with heart action at the thorax and the legs. The obtained signals were analyzed by partial correlation analyses in comparison with plasma BNP, CHF classes, ejection fraction by echocardiography and cardiac index by double gas re-breathing. 119 subjects (34 healthy volunteers, 50 patients with CHF, NYHA classes II to IV and 35 patients without CHF) were investigated. RESULTS The maximal rate of volume change with heart action at the thorax and at the legs, as well as the ECF/ICF ratio at the legs contribute equally and independently to the prediction of BNP and heart failure in an unknown test sample of 49 patients (multiple r=0.88, p<0.001). The ROC-curve for the predicted plasma BNP>400 pg/ml gave an AUC=0.93. The absence or the presence of heart failure could be predicted correctly by a binomial logistic regression in 92.9 and 87.5% of cases, respectively. CONCLUSION The methodology, which is based on inverse coupling of BNP release and of maximal blood acceleration and on sensitive detection of ECF overload, could enable the diagnosis of CHF with useful sensitivity and specificity while writing a routine-ECG.
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Affiliation(s)
- Falko Skrabal
- Institute for Cardiovascular and Metabolic Medicine, Mariatrosterstrasse 67, A8043 Graz, Austria.
| | - Georg P Pichler
- Institute for Cardiovascular and Metabolic Medicine, Mariatrosterstrasse 67, A8043 Graz, Austria
| | - Gerfried Gratze
- Krankenhaus Barmherzige Brüder, Marschallgasse, Teaching Hospital Medical University Graz, Austria
| | - Albert Holler
- Krankenhaus Barmherzige Brüder, Marschallgasse, Teaching Hospital Medical University Graz, Austria
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Wi H, Sohal H, McEwan AL, Woo EJ, Oh TI. Multi-frequency electrical impedance tomography system with automatic self-calibration for long-term monitoring. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2014; 8:119-128. [PMID: 24681925 DOI: 10.1109/tbcas.2013.2256785] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Electrical Impedance Tomography (EIT) is a safe medical imaging technology, requiring no ionizing or heating radiation, as opposed to most other imaging modalities. This has led to a clinical interest in its use for long-term monitoring, possibly at the bedside, for ventilation monitoring, bleeding detection, gastric emptying and epilepsy foci diagnosis. These long-term applications demand auto-calibration and high stability over long time periods. To address this need we have developed a new multi-frequency EIT system called the KHU Mark2.5 with automatic self-calibration and cooperation with other devices via a timing signal for synchronization with other medical instruments. The impedance measurement module (IMM) for flexible configuration as a key component includes an independent constant current source, an independent differential voltmeter, and a current source calibrator, which allows automatic self-calibration of the current source within each IMM. We installed a resistor phantom inside the KHU Mark2.5 EIT system for intra-channel and inter-channel calibrations of all voltmeters in multiple IMMs. We show the deterioration of performance of an EIT system over time and the improvement due to automatic self-calibration. The system is able to maintain SNR of 80 dB for frequencies up to 250 kHz and below 0.5% reciprocity error over continuous operation for 24 hours. Automatic calibration at least every 3 days is shown to maintain SNR above 75 dB and reciprocity error below 0.7% over 7 days at 1 kHz. A clear degradation in performance results with increasing time between automatic calibrations allowing the tailoring of calibration to suit the performance requirements of each application.
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Chuen MJNK, Lip GYH, MacFadyen RJ. Repeated assessment of physical biomeasures or blood biomarkers for the definition of volume status and cardiac loading in LVSD. Biomark Med 2012; 1:355-74. [PMID: 20477380 DOI: 10.2217/17520363.1.3.355] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The application of biomarker technology can be usefully implemented in areas where current techniques are inadequate and where a clinical issue, which affects outcome, can be defined. The definition of the loading status of the heart where there is pre-existent impairment of contractile function is a key target. Heart failure is a complex clinical presentation with many varied etiologies, but at the essence of its successful management is the reliable definition of cardiac volume loading. Traditional and many current technological measures are applied to define this relationship, yet their accuracy and performance in individual patients is either basically inadequate or poorly understood and applied. There is a wide range of both physical measurements and blood biomarkers that can be considered to better define this key issue in patients with ventricular systolic impairment. Their performance is considered in detail in this review.
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Balparda JK, Gallo JA, McEwen JG, Ochoa JE, Aristizábal D. Evaluación hemodinámica no invasiva con cardiografía de impedancia: aplicaciones en falla cardíaca y en hipertensión arterial. REVISTA COLOMBIANA DE CARDIOLOGÍA 2012. [DOI: 10.1016/s0120-5633(12)70111-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Anand IS, Doan AD, Ma KW, Toth JA, Geyen KJ, Otterness S, Chakravarthy N, Katra RP, Libbus I. Monitoring Changes in Fluid Status With a Wireless Multisensor Monitor: Results From the Fluid Removal During Adherent Renal Monitoring (FARM) Study. ACTA ACUST UNITED AC 2011; 18:32-6. [DOI: 10.1111/j.1751-7133.2011.00271.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Riera J, Riu PJ, Casan P, Masclans JR. [Electrical impedance tomography in acute lung injury]. Med Intensiva 2011; 35:509-17. [PMID: 21680060 DOI: 10.1016/j.medin.2011.05.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 05/01/2011] [Accepted: 05/03/2011] [Indexed: 01/18/2023]
Abstract
Electrical impedance tomography has been described as a new method of monitoring critically ill patients on mechanical ventilation. It has recently gained special interest because of its applicability for monitoring ventilation and pulmonary perfusion. Its bedside and continuous implementation, and the fact that it is a non-ionizing and non-invasive technique, makes it an extremely attractive measurement tool. Likewise, given its ability to assess the regional characteristics of lung structure, it could be considered an ideal monitoring tool in the heterogeneous lung with acute lung injury. This review explains the physical concept of bioimpedance and its clinical application, and summarizes the scientific evidence published to date with regard to the implementation of electrical impedance tomography as a method for monitoring ventilation and perfusion, mainly in the patient with acute lung injury, and other possible applications of the technique in the critically ill patient. The review also summarizes the limitations of the technique and its potential areas of future development.
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Affiliation(s)
- J Riera
- Servicio de Medicina Intensiva, Hospital Universitario Vall d'Hebron, Vall d'Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, España.
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Shochat M, Shotan A, Trachtengerts V, Blondheim DS, Kazatsker M, Gurovich V, Asif A, Shochat I, Rozenman Y, Meisel SR. A novel radiological score to assess lung fluid content during evolving acute heart failure in the course of acute myocardial infarction. ACTA ACUST UNITED AC 2011; 13:81-6. [DOI: 10.3109/17482941.2011.567279] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Arad M, Zlochiver S, Davidson T, Shovman O, Shoenfeld Y, Adunsky A, Abboud S. Estimating pulmonary congestion in elderly patients using bio-impedance technique: Correlation with clinical examination and X-ray results. Med Eng Phys 2009; 31:959-63. [DOI: 10.1016/j.medengphy.2009.05.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2008] [Revised: 03/12/2009] [Accepted: 05/19/2009] [Indexed: 11/27/2022]
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Arad M, Zlochiver S, Davidson T, Shoenfeld Y, Adunsky A, Abboud S. The detection of pleural effusion using a parametric EIT technique. Physiol Meas 2009; 30:421-8. [DOI: 10.1088/0967-3334/30/4/006] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Sokolovsky RE, Zlochiver S, Abboud S. Stroke volume estimation in heart failure patients using bioimpedance: a realistic simulation of the forward problem. Physiol Meas 2008; 29:S139-49. [DOI: 10.1088/0967-3334/29/6/s12] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
Electrical impedance tomography (EIT) is a non-invasive technique that aims to reconstruct images of internal impedance values of a volume of interest, based on measurements taken on the external boundary. Since most reconstruction algorithms rely on model-based approximations, it is important to ensure numerical accuracy for the model being used. This work demonstrates and highlights the importance of accurate modelling in terms of model discretization (meshing) and shows that although the predicted boundary data from a forward model may be within an accepted error, the calculated internal field, which is often used for image reconstruction, may contain errors, based on the mesh quality that will result in image artefacts.
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Freimark D, Arad M, Sokolover R, Zlochiver S, Abboud S. Monitoring lung fluid content in CHF patients under intravenous diuretics treatment using bio-impedance measurements. Physiol Meas 2007; 28:S269-77. [PMID: 17664641 DOI: 10.1088/0967-3334/28/7/s20] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A pulmonary edema monitoring system (PulmoTrace, CardioInspect, Tel-Aviv University, Israel) was evaluated for tracking lung resistivity during diuretics treatment in congestive heart failure (CHF) patients. The system incorporates a bio-impedance measurement algorithm and enables, by employing an eight-electrode thoracic belt, the assessment of both the left- and right-lung resistivity values. A clinical study was conducted on a group of 13 CHF patients under intravenous diuretics treatment. The group was measured twice-before the beginning of treatment and following a period of a couple of hours. An increase of 8% of the mean lung resistivity (median value) was found between the two measuring sessions, which indicates a dehydration of the lungs, and a significant correlation (R=0.73, p=0.004) was found between the lung resistivity change and the urine output. In conjunction with previously reported results, which demonstrated the system's reproducibility and long-term monitoring capabilities, this study further supports the diagnostics value of the system.
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Affiliation(s)
- D Freimark
- Department of Cardiology, Sheba Medical Center, Ramat-Gan, Israel
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Nebuya S, Noshiro M, Yonemoto A, Tateno S, Brown BH, Smallwood RH, Milnes P. Study of the optimum level of electrode placement for the evaluation of absolute lung resistivity with the Mk3.5 EIT system. Physiol Meas 2006; 27:S129-37. [PMID: 16636404 DOI: 10.1088/0967-3334/27/5/s11] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Inter-subject variability has caused the majority of previous electrical impedance tomography (EIT) techniques to focus on the derivation of relative or difference measures of in vivo tissue resistivity. Implicit in these techniques is the requirement for a reference or previously defined data set. This study assesses the accuracy and optimum electrode placement strategy for a recently developed method which estimates an absolute value of organ resistivity without recourse to a reference data set. Since this measurement of tissue resistivity is absolute, in Ohm metres, it should be possible to use EIT measurements for the objective diagnosis of lung diseases such as pulmonary oedema and emphysema. However, the stability and reproducibility of the method have not yet been investigated fully. To investigate these problems, this study used a Sheffield Mk3.5 system which was configured to operate with eight measurement electrodes. As a result of this study, the absolute resistivity measurement was found to be insensitive to the electrode level between 4 and 5 cm above the xiphoid process. The level of the electrode plane was varied between 2 cm and 7 cm above the xiphoid process. Absolute lung resistivity in 18 normal subjects (age 22.6 +/- 4.9, height 169.1 +/- 5.7 cm, weight 60.6 +/- 4.5 kg, body mass index 21.2 +/- 1.6: mean +/- standard deviation) was measured during both normal and deep breathing for 1 min. Three sets of measurements were made over a period of several days on each of nine of the normal male subjects. No significant differences in absolute lung resistivity were found, either during normal tidal breathing between the electrode levels of 4 and 5 cm (9.3 +/- 2.4 Omega m, 9.6 +/- 1.9 Omega m at 4 and 5 cm, respectively: mean +/- standard deviation) or during deep breathing between the electrode levels of 4 and 5 cm (10.9 +/- 2.9 Omega m and 11.1 +/- 2.3 Omega m, respectively: mean +/- standard deviation). However, the differences in absolute lung resistivity between normal and deep tidal breathing at the same electrode level are significant. No significant difference was found in the coefficient of variation between the electrode levels of 4 and 5 cm (9.5 +/- 3.6%, 8.5 +/- 3.2% at 4 and 5 cm, respectively: mean +/- standard deviation in individual subjects). Therefore, the electrode levels of 4 and 5 cm above the xiphoid process showed reasonable reliability in the measurement of absolute lung resistivity both among individuals and over time.
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Affiliation(s)
- S Nebuya
- Department of Clinical Engineering, Kitasato University, Sagamihara 228-8555, Japan.
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Zlochiver S, Arad M, Radai MM, Barak-Shinar D, Krief H, Engelman T, Ben-Yehuda R, Adunsky A, Abboud S. A portable bio-impedance system for monitoring lung resistivity. Med Eng Phys 2006; 29:93-100. [PMID: 16546432 DOI: 10.1016/j.medengphy.2006.02.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2005] [Revised: 01/26/2006] [Accepted: 02/07/2006] [Indexed: 10/24/2022]
Abstract
The principles of a hybrid bio-impedance technique are implemented in a novel, lung resistivity monitoring system ("CardioInspect" Tel-Aviv University, Israel). The system is to be utilized in the clinic or at home, for daily monitoring of patients suffering from pulmonary edema. The developed system consists of an eight-electrode belt worn around the thorax, an electronic unit containing analog and digital boards, and a stand-alone DSP based system with a designated software to analyze the data. A Newton-Raphson algorithm based on the finite-volume method is employed for the optimization of the left and right lung resistivity values, making use of the voltage measurements retrieved from opposite current injections. In this preliminary study, 33 healthy volunteers were measured with the system during tidal respiration, yielding symmetric mean left and right lung resistivity values of (1205+/-163, 1200+/-165) (Omega cm). The system reproducibility was better than 2% for both within and between tests measurements, and no dependency between the reconstructed values and various anthropometric parameters was found.
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Affiliation(s)
- S Zlochiver
- Department of Biomedical Engineering, Tel-Aviv University, Israel
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Shochat M, Charach G, Meyler S, Kazatzker M, Mosseri M, Frimerman A, Rabinovich P, Shotan A, Meisel S. Internal thoracic impedance monitoring: a novel method for the preclinical detection of acute heart failure. CARDIOVASCULAR REVASCULARIZATION MEDICINE 2006; 7:41-5. [PMID: 16513522 DOI: 10.1016/j.carrev.2005.10.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2005] [Accepted: 10/12/2005] [Indexed: 10/25/2022]
Abstract
BACKGROUND Acute heart failure (AHF) evolves through two phases. In the first phase, there is interstitial congestion with no clinical sign of edema (preclinical phase); the second, during which lung alveoli begin to fill with fluid, manifests as clinically overt alveolar edema. Treatment of AHF at its preclinical phase can alleviate its clinical impact. Presently, there is no technique that detects the interstitial phase of AHF. We used a device based on a new method of lung bioimpedance measurement. The device measures internal thoracic impedance (ITI), which nearly equals inherent lung bioimpedance. This method can detect small changes in lung fluid that occur during the interstitial stage of AHF. AIM The objective of this study was to assess the feasibility and efficacy of the said new method in detecting preclinical AHF. METHODS Internal thoracic impedance and pertinent clinical parameters were monitored for 72 h in 403 patients hospitalized for an acute coronary syndrome without evidence of AHF at study entry. RESULTS Seventy patients developed AHF during monitoring. Internal thoracic impedance decreased in these patients by 16.4% (95% CI=-12.2% to -20.6%; P<.0001) from the baseline level at 44+/-15.1 min prior to the onset of lung rales. The other 333 patients had no clinical sign of AHF, and their ITI declined only by 4.5% (95% CI=2.5% to -11.5%; P=.3) compared with the baseline level. CONCLUSION The new method for ITI measurement is sufficiently sensitive in detecting AHF at its preclinical stage. An ITI decrease of more than 12% heralds the appearance of clinically overt AHF and, thus, allows earlier therapy.
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Affiliation(s)
- Michael Shochat
- Heart Institute, Hillel Yaffe Medical Center (affiliated to the Rappaport School of Medicine, The Technion, Haifa, Israel), Hadera 38100, Israel.
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Zlochiver S, Radai MM, Barak-Shinar D, Ben-Gal T, Yaari V, Strasberg B, Abboud S. Monitoring Lung Resistivity Changes in Congestive Heart Failure Patients Using the Bioimpedance Technique. ACTA ACUST UNITED AC 2005; 11:289-93. [PMID: 16330903 DOI: 10.1111/j.1527-5299.2005.04459.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The feasibility of a novel, dedicated system for monitoring lung resistivity in congestive heart failure patients, implementing a hybrid approach of the bioimpedance technique, was assessed in this preliminary study. Thirty-three healthy volunteers and 34 congestive heart failure patients were measured with the PulmoTrace system (CardioInspect, Tel Aviv University, Tel Aviv, Israel) during tidal respiration, and the ability to monitor the respective lung resistivity values was assessed. Mean left and right lung resistivity values of 1205+/-163 and 1200+/-165 ohm.cm for the control group and 888+/-193 and 943+/-187 ohm.cm for the congestive heart failure group were found, indicating a significant (p<2.10(-7)) difference between the two groups. The results of long-term monitoring of two patients during medical treatment are also shown. This hybrid approach system is believed to improve diagnostic capabilities and help physicians to better adjust medication dosage on a frequent basis.
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Affiliation(s)
- Sharon Zlochiver
- Department of Biomedical Engineering, Tel Aviv University, Ramat Aviv, Israel
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24
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Summers RL. Emerging diagnostics: impedance cardiography in the assessment and management of acute heart failure. Crit Pathw Cardiol 2005; 4:134-139. [PMID: 18340199 DOI: 10.1097/01.hpc.0000174911.92565.16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Affiliation(s)
- Richard L Summers
- Department of Emergency Medicine, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA.
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Yu CM, Wang L, Chau E, Chan RHW, Kong SL, Tang MO, Christensen J, Stadler RW, Lau CP. Intrathoracic impedance monitoring in patients with heart failure: correlation with fluid status and feasibility of early warning preceding hospitalization. Circulation 2005; 112:841-8. [PMID: 16061743 DOI: 10.1161/circulationaha.104.492207] [Citation(s) in RCA: 537] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Patients with heart failure are frequently hospitalized for fluid overload. A reliable method for chronic monitoring of fluid status is therefore desirable. We evaluated an implantable system capable of measuring intrathoracic impedance to identify potential fluid overload before heart failure hospitalization and to determine the correlation between intrathoracic impedance and standard measures of fluid status during hospitalization. METHODS AND RESULTS Thirty-three patients with NYHA class III and IV heart failure were implanted with a special pacemaker in the left pectoral region and a defibrillation lead in the right ventricle. Intrathoracic impedance was regularly measured and recorded between the lead and the pacemaker case. During hospitalizations, pulmonary capillary wedge pressure and fluid status were monitored. Ten patients were hospitalized for fluid overload 25 times over 20.7+/-8.4 months. Intrathoracic impedance decreased before each admission by an average of 12.3+/-5.3% (P<0.001) over an average of 18.3+/-10.1 days. Impedance reduction began 15.3+/-10.6 days (P<0.001) before the onset of worsening symptoms. There was an inverse correlation between intrathoracic impedance and pulmonary capillary wedge pressure (r=-0.61, P<0.001) and between intrathoracic impedance and net fluid loss (r=-0.70, P<0.001) during hospitalization. Automated detection of impedance decreases was 76.9% sensitive in detecting hospitalization for fluid overload, with 1.5 false-positive (threshold crossing without hospitalization) detections per patient-year of follow-up. CONCLUSIONS Intrathoracic impedance is inversely correlated with pulmonary capillary wedge pressure and fluid balance and decreased before the onset of patient symptoms and before hospital admission for fluid overload. Regular monitoring of impedance may provide early warning of impending decompensation and diagnostic information for titration of medication.
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Affiliation(s)
- Cheuk-Man Yu
- Division of Cardiology, Department of Medicine and Therapeutics, Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong.
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Dehghani H, Soni N, Halter R, Hartov A, Paulsen KD. Excitation patterns in three-dimensional electrical impedance tomography. Physiol Meas 2005; 26:S185-97. [PMID: 15798231 DOI: 10.1088/0967-3334/26/2/018] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Electrical impedance tomography (EIT) is a non-invasive technique that aims to reconstruct images of internal electrical properties of a domain, based on electrical measurements on the periphery. Improvements in instrumentation and numerical modeling have led to three-dimensional (3D) imaging. The availability of 3D modeling and imaging raises the question of identifying the best possible excitation patterns that will yield to data, which can be used to produce the best image reconstruction of internal properties. In this work, we describe our 3D finite element model of EIT. Through singular value decomposition as well as examples of reconstructed images, we show that for a homogenous female breast model with four layers of electrodes, a driving pattern where each excitation plane is a sinusoidal pattern out-of-phase with its neighboring plane produces better qualitative images. However, in terms of quantitative imaging an excitation pattern where all electrode layers are in phase produces better results.
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Affiliation(s)
- Hamid Dehghani
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA
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27
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Mayer M, Brunner P, Merwa R, Scharfetter H. Monitoring of lung edema using focused impedance spectroscopy: a feasibility study. Physiol Meas 2005; 26:185-92. [PMID: 15798294 DOI: 10.1088/0967-3334/26/3/004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Currently only ionizing or invasive methods are used in clinical applications for the monitoring of extracellular lung water. Alternatively a method called focused conductivity spectroscopy (FCS) is suggested, which aims at reconstructing a pulmonary edema index (PEIX) by measuring the electrical conductivity of the region of interest (ROI) at several frequencies. In contrast to electrical impedance tomography (EIT) a minimum number of strategically placed electrodes is used. The goals of this study were the analysis of the sensitivity for the PEIX, an estimate of the optimal electrode configuration and the determination of the required frequencies. In order to calculate the solution of the FCS forward problem a realistic 3D model of a human torso was developed containing both lungs, the heart, the liver and the thorax musculature. The bioelectrical properties for each compartment were described with appropriate tissue models which relate the conductivity spectra to physiological parameters. The PEIX was defined as the interstitial volume fraction of the alveolar septa. Furthermore the model includes 48 electrodes subdivided into three layers. The optimal electrode configuration was selected by minimizing the number of electrodes, among certain subsets of these electrodes. The analysis shows that eight to ten electrodes and six frequencies are theoretically sufficient to obtain a coefficient of variation.
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Affiliation(s)
- Michael Mayer
- Institute for Medical Engineering, Graz University of Technology, Krenngasse 37, 8010 Graz, Austria.
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28
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Patterson RP, Zhang J. Evaluation of an EIT reconstruction algorithm using finite difference human thorax models as phantoms. Physiol Meas 2003; 24:467-75. [PMID: 12812430 DOI: 10.1088/0967-3334/24/2/357] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A finite difference model of the human thorax with 113,400 control volumes (nodes) based on ECG gated MRI images was used to evaluate the Sheffield DAS-01P EIT system. Sixteen simulated electrode positions equally spaced around the thorax model at approximately the fourth intercostals space level were selected. Pairs of adjacent positions were excited sequentially by injecting current in a manner similar to that used by the Sheffield DAS-01P EIT system. The resulting voltages on the non-excited electrode positions were calculated and used to reconstruct the image using the Sheffield filtered back projection algorithm. By changing the resistivities of the lungs, the ventricles and the atria over a range of 1% to 40%, the resulting changes in the images were quantified by measuring the average resistivity change over a region defined automatically by two thresholds, 40% or 80% of the average of the first four pixels with the largest change. The results show that the changes observed in the images are consistently less than the changes in the model, but changed in a nearly linear manner as a function of resistivity in the model. For 40% resistivity changes in the model for right lung, right ventricle and right atrium, the observed resistivity changes in the region of interest (ROI, defined by the 80% threshold) of the images are 32% for the right lung, 11% for the right ventricle and 5.5% for the right atrium, which suggests strong volume dependence of EIT imaging. The effect of structural (size) change between end diastole and end systole was also studied, which showed large resistivity changes caused in the heart region of the constructed image. The study demonstrates that the Sheffield DAS-01P EIT reconstruction algorithm tracks the change occurring in the lungs most closely and with proper scaling may be used to observe physiological changes.
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Affiliation(s)
- Robert P Patterson
- Biomedical Engineering Institute, and Department of Physical Medicine and Rehabilitation, University of Minnesota, Minneapolis, MN 55455, USA.
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Brown BH, Primhak RA, Smallwood RH, Milnes P, Narracott AJ, Jackson MJ. Neonatal lungs--can absolute lung resistivity be determined non-invasively? Med Biol Eng Comput 2002; 40:388-94. [PMID: 12227624 DOI: 10.1007/bf02345070] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The electrical resistivity of lung tissue can be related to the structure and composition of the tissue and also to the air content. Conditions such as pulmonary oedema and emphysema have been shown to change lung resistivity. However, direct access to the lungs to enable resistivity to be measured is very difficult. We have developed a new method of using electrical impedance tomographic (EIT) measurements on a group of 142 normal neonates to determine the absolute resistivity of lung tissue. The methodology involves comparing the measured EIT data with that from a finite difference model of the thorax in which lung tissue resistivity can be changed. A mean value of 5.7 +/- 1.7 omega(m) was found over the frequency range 4 kHz to 813 kHz. This value is lower than that usually given for adult lung tissue but consistent with the literature on the composition of the neonatal lung and with structural modelling.
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Affiliation(s)
- B H Brown
- Medical Physics and Clinical Engineering, University of Sheffield, Royal Hallamshire Hospital, UK.
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Wilson AJ, Milnes P, Waterworth AR, Smallwood RH, Brown BH. Mk3.5: a modular, multi-frequency successor to the Mk3a EIS/EIT system. Physiol Meas 2001; 22:49-54. [PMID: 11236889 DOI: 10.1088/0967-3334/22/1/307] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This paper describes the Sheffield Mk3.5 EIT/EIS system which measures both the real and imaginary part of impedance at 30 frequencies between 2 kHz and 1.6 MHz. The system uses eight electrodes with an adjacent drive/receive electrode data acquisition protocol. The system is modular, containing eight identical data acquisition boards, which contain DSPs to generate the drive frequencies and to perform the FFT used for demodulation. The current drive is in three sequentially applied packets, where each packet contains ten summed sine waves. The data acquisition system is interfaced to a host PC through an optically isolated high speed serial link (RS485) running at 2 Mbaud (2 Mbits s(-1)). Measurements on a saline filled tank show that the average signal to noise performance of the system is 40 dB measured across all frequencies and that this figure is independent of frequency of measurement. These results suggest that the current system is 10 dB better in absolute terms than the previous Sheffield (Mk3a) system.
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Affiliation(s)
- A J Wilson
- Department of Medical Physics and Clinical Engineering, Royal Hallamshire Hospital, Sheffield, UK
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Noble TJ, Harris ND, Morice AH, Milnes P, Brown BH. Diuretic induced change in lung water assessed by electrical impedance tomography. Physiol Meas 2000; 21:155-63. [PMID: 10720011 DOI: 10.1088/0967-3334/21/1/319] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Monitoring patients with left ventricular failure can be difficult. Electrical impedance tomography (EIT) produces cross-sectional images of changes in the impedance of the thorax. We measured changes in the electrical impedance of the lung in nine volunteers following a diuretic challenge. The hypothesis was that lung impedance would increase with diuretic induced fluid loss. Heart rate, blood pressure and urine output were also recorded. After diuretic the mean urine output was 1220 ml compared with 187 ml after placebo. Following diuretic administration, mean thoracic impedance increased by 13.6% (p < 0.01) and lung impedance increased by 7.8% (p < 0.05). Taken as a group there was a correlation between overall impedance change and total urine output. However, for each individual, the time course of change in impedance and urine output did not correlate significantly. Our findings show that EIT may offer a better guide to the response of the lung to diuretic treatment than simply measuring urine output. The urine output is neither specific nor sensitive in the assessment of lung water. Mean lung impedance, however, is largely determined by lung water. The study showed that lung impedance can be recorded at supra-normal values. EIT may help in the management of patients with excess lung water.
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Affiliation(s)
- T J Noble
- Pulmonary Medicine, University of Sheffield, UK
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