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Effects of pleural effusion drainage in the mechanically ventilated patient as monitored by electrical impedance tomography and end-expiratory lung volume: A pilot study. J Crit Care 2020; 59:76-80. [DOI: 10.1016/j.jcrc.2020.06.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 04/25/2020] [Accepted: 06/01/2020] [Indexed: 12/17/2022]
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Segmental Bioelectrical Impedance Spectroscopy to Monitor Fluid Status in Heart Failure. Sci Rep 2020; 10:3577. [PMID: 32109235 PMCID: PMC7046702 DOI: 10.1038/s41598-020-60358-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 02/05/2020] [Indexed: 01/10/2023] Open
Abstract
Bioelectrical impedance spectroscopy (BIS) measures body composition, including fluid status. Acute decompensated heart failure (ADHF) is associated with fluid overload in different body compartments. This investigation aimed to evaluate the feasibility of measuring and monitoring fluid accumulation in patients with ADHF using BIS. The extracellular impedance as a surrogate marker for fluid accumulation was measured in 67 participants (25 healthy reference volunteers and 42 patients admitted with ADHF) using BIS in the “transthoracic”, “foot-to-foot”, “whole-body” and “hand-to-hand” segments. At baseline, BIS showed significantly lower extracellular resistance values for the “whole-body” (P < 0.001), “foot-to-foot” (P = 0.03), “hand-to-hand” (P < 0.001) and “transthoracic” (P = 0.014) segments in patients with ADHF than the reference cohort, revealing a specific pattern for peripheral, central and general fluid accumulation. The “foot-to-foot” (AUC = 0.8, P < 0.001) and “hand-to-hand” (AUC = 0.74, P = 0.04) segments indicated compartments of fluid accumulation with good prediction. During cardiac recompensation, BIS values changed significantly and were in line with routine parameters for monitoring ADHF. Mean bodyweight change per day correlated moderately to good with BIS values in the “whole-body” (r = −0.4), “foot-to-foot” (r = −0.8) and “transthoracic” (r = −0.4) segments. Based on our analysis, we conclude that measuring and monitoring fluid accumulation in ADHF using segmental BIS is feasible and correlates with clinical parameters during recompensation.
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Ngo C, Spagnesi S, Munoz C, Lehmann S, Vollmer T, Misgeld B, Leonhardt S. Assessing regional lung mechanics by combining electrical impedance tomography and forced oscillation technique. ACTA ACUST UNITED AC 2019; 63:673-681. [PMID: 28850542 DOI: 10.1515/bmt-2016-0196] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 07/17/2017] [Indexed: 11/15/2022]
Abstract
There is a lack of noninvasive pulmonary function tests which can assess regional information of the lungs. Electrical impedance tomography (EIT) is a radiation-free, non-invasive real-time imaging that provides regional information of ventilation volume regarding the measurement of electrical impedance distribution. Forced oscillation technique (FOT) is a pulmonary function test which is based on the measurement of respiratory mechanical impedance over a frequency range. In this article, we introduce a new measurement approach by combining FOT and EIT, named the oscillatory electrical impedance tomography (oEIT). Our oEIT measurement system consists of a valve-based FOT device, an EIT device, pressure and flow sensors, and a computer fusing the data streams. Measurements were performed on five healthy volunteers at the frequencies 3, 4, 5, 6, 7, 8, 10, 15, and 20 Hz. The measurements suggest that the combination of FOT and EIT is a promising approach. High frequency responses are visible in the derivative of the global impedance index ΔZeit(t,fos). $\Delta {Z_{{\text{eit}}}}(t,{f_{{\text{os}}}}).$ The oEIT signals consist of three main components: forced oscillation, spontaneous breathing, and heart activity. The amplitude of the oscillation component decreases with increasing frequency. The band-pass filtered oEIT signal might be a new tool in regional lung function diagnostics, since local responses to high frequency perturbation could be distinguished between different lung regions.
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Affiliation(s)
- Chuong Ngo
- Philips Chair of Medical Information Technology, Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Pauwelsstr. 20, 52074 Aachen, Germany
| | - Sarah Spagnesi
- Philips Chair of Medical Information Technology, Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Pauwelsstr. 20, 52074 Aachen, Germany
| | - Carlos Munoz
- Philips Chair of Medical Information Technology, Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Pauwelsstr. 20, 52074 Aachen, Germany
| | - Sylvia Lehmann
- Department of Pediatric Pulmonology, University Hospital RWTH Aachen, Pauwelsstr. 30, 52074 Aachen, Germany
| | - Thomas Vollmer
- Philips GmbH Innovative Technologies Aachen, Pauwelsstr. 17, 52074 Aachen, Germany
| | - Berno Misgeld
- Philips Chair of Medical Information Technology, Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Pauwelsstr. 20, 52074 Aachen, Germany
| | - Steffen Leonhardt
- Philips Chair of Medical Information Technology, Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Pauwelsstr. 20, 52074 Aachen, Germany
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Frerichs I, Golisch W, Hahn G, Michael K, Burchardi H, Hellige G. Heterogeneous Distribution of Pulmonary Ventilation in Intensive Care Patients Detected by Functional Electrical Impedance Tomography. J Intensive Care Med 2016. [DOI: 10.1177/088506669801300404] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Electrical impedance tomography (EIT) is a new noninvasive imaging technique which utilizes the different electrical properties of biological tissues to produce cross-sectional images of selected parts of the body. When applied on the thorax, the cyclic fluctuations of electrical impedance of the lung tissue, associated with different air contents of the lungs in the course of the respiratory cycle, can be used to generate derived EIT tomograms which represent the spatial distribution of ventilation in the chosen transverse plane. The corresponding evaluation technique, the functional EIT, was used for the first time to follow the regional ventilation in three intensive care patients. The method was shown (1) to identify the redistribution of inspired air in the lungs associated with controlled ventilation in a patient undergoing elective laparotomy, (2) to follow the improvement of locally impaired lung ventilation in the course of severe pneumonia, and (3) to detect regional reduction of ventilation due to lobar atelectasis with stasis pneumonia in a patient with bronchial carcinoma.
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Affiliation(s)
- Inéz Frerichs
- Department of Anesthesiological Research, University of Göttingen, Göttingen, Germany
| | - Wolfgang Golisch
- Department of Anesthesiological Research, University of Göttingen, Göttingen, Germany
| | - Günter Hahn
- Department of Anesthesiological Research, University of Göttingen, Göttingen, Germany
| | - Kurpitz Michael
- Department of Anesthesiological Research, University of Göttingen, Göttingen, Germany
| | - Hilmar Burchardi
- Department of Anesthesiological Research, University of Göttingen, Göttingen, Germany
| | - Gerhard Hellige
- Department of Anesthesiological Research, University of Göttingen, Göttingen, Germany
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5
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Feasibility of bioelectrical impedance spectroscopy measurement before and after thoracentesis. BIOMED RESEARCH INTERNATIONAL 2015; 2015:810797. [PMID: 25861647 PMCID: PMC4377452 DOI: 10.1155/2015/810797] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2014] [Accepted: 02/19/2015] [Indexed: 11/30/2022]
Abstract
Background. Bioelectrical impedance spectroscopy is applied to measure changes in tissue composition. The aim of this study was to evaluate its feasibility in measuring the fluid shift after thoracentesis in patients with pleural effusion. Methods. 45 participants (21 with pleural effusion and 24 healthy subjects) were included. Bioelectrical impedance was analyzed for “Transthoracic,” “Foot to Foot,” “Foot to Hand,” and “Hand to Hand” vectors in low and high frequency domain before and after thoracentesis. Healthy subjects were measured at a single time point. Results. The mean volume of removed pleural effusion was 1169 ± 513 mL. The “Foot to Foot,” “Hand to Hand,” and “Foot to Hand” vector indicated a trend for increased bioelectrical impedance after thoracentesis. Values for the low frequency domain in the “Transthoracic” vector increased significantly (P < 0.001). A moderate correlation was observed between the amount of removed fluid and impedance change in the low frequency domain using the “Foot to Hand” vector (r = −0.7). Conclusion. Bioelectrical impedance changes in correlation with the thoracic fluid level. It was feasible to monitor significant fluid shifts and loss after thoracentesis in the “Transthoracic” vector by means of bioelectrical impedance spectroscopy. The trial is registered with Registration Numbers IRB EK206/11 and NCT01778270.
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Lung Reaeration and Reventilation after Aspiration of Pleural Effusions. A Study Using Electrical Impedance Tomography. Ann Am Thorac Soc 2014; 11:186-91. [DOI: 10.1513/annalsats.201306-142oc] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Reifferscheid F, Elke G, Pulletz S, Gawelczyk B, Lautenschläger I, Steinfath M, Weiler N, Frerichs I. Regional ventilation distribution determined by electrical impedance tomography: reproducibility and effects of posture and chest plane. Respirology 2011; 16:523-31. [PMID: 21261780 DOI: 10.1111/j.1440-1843.2011.01929.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND AND OBJECTIVE Reliable assessment of regional lung ventilation and good reproducibility of electrical impedance tomography (EIT) data are the prerequisites for the future application of EIT in a clinical setting. The aims of our study were to determine (i) the reproducibility of repeated EIT measurements and (ii) the effect of the studied transverse chest plane on ventilation distribution in different postures. METHODS Ten healthy adult subjects were studied in three postures on two separate days. EIT and spirometric data were obtained during tidal breathing and slow vital capacity (VC) manoeuvres. EIT data were acquired in two chest planes at 13 scans/s. Reproducibility of EIT findings was assessed by Bland-Altman analysis and Pearson correlation in 16 regions of interest in each plane. Regional ventilation distribution during tidal breathing and deep expiration was determined as fractional ventilation in four quadrants of the studied chest cross-sections. RESULTS Our study showed a good reproducibility of EIT measurements repeated after an average time interval of 8 days. Global tidal volumes and VCs determined by spirometry on separate days were not significantly different. Regional ventilation in chest quadrants assessed by EIT was also unaffected. Posture exerted a significant effect on ventilation distribution among the chest quadrants during spontaneous breathing and deep expiration in both planes. The spatial distribution patterns in the two planes were not identical. CONCLUSIONS We conclude that regional EIT ventilation findings are reproducible and recommend that the EIT examination location on the chest is carefully chosen especially during repeated measurements and follow-up.
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Affiliation(s)
- Florian Reifferscheid
- Department of Anaesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein-Campus Kiel, Kiel, Germany
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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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Dai T, Gómez-Laberge C, Adler A. Reconstruction of conductivity changes and electrode movements based on EIT temporal sequences. Physiol Meas 2008; 29:S77-88. [PMID: 18544802 DOI: 10.1088/0967-3334/29/6/s07] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Electrical impedance tomography (EIT) reconstructs a conductivity change image within a body from electrical measurements on the body surface; while it has relatively low spatial resolution, it has a high temporal resolution. One key difficulty with EIT measurements is due to the movement and position uncertainty of the electrodes, especially due to breathing and posture change. In this paper, we develop an approach to reconstruct both the conductivity change image and the electrode movements from the temporal sequence of EIT measurements. Since both the conductivity change and electrode movement are slow with respect to the data frame rate, there are significant temporal correlations which we formulate as priors for the regularized image reconstruction model. Image reconstruction is posed in terms of a regularization matrix and a Jacobian matrix which are augmented for the conductivity change and electrode movement, and then further augmented to concatenate the d previous and future frames. Results are shown for simulation, phantom and human data, and show that the proposed algorithm yields improved resolution and noise performance in comparison to a conventional one-step reconstruction method.
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Affiliation(s)
- Tao Dai
- Systems and Computer Engineering, Carleton University, Ottawa, Canada
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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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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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12
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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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13
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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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14
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Frerichs I. Electrical impedance tomography (EIT) in applications related to lung and ventilation: a review of experimental and clinical activities. Physiol Meas 2000; 21:R1-21. [PMID: 10847187 DOI: 10.1088/0967-3334/21/2/201] [Citation(s) in RCA: 172] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This review article is a summary of the publications dealing with the pulmonary applications of electrical impedance tomography (EIT). Original papers on EIT lung imaging published over 15 years are analysed and several aspects of the performed EIT measurements summarized. Information on the type of the EIT device and electrodes used, the studied transverse thoracic planes, the data acquisition rate, the number of studied animals, normal subjects or patients, the kind of lung pathology, the performed ventilatory manoeuvres and other interventions, as well as the applied reference techniques, is given. The type of the generated pulmonary EIT images and the quantitative analysis of the EIT data are described. Finally, the major results achieved are presented, followed by an analysis of the perspectives of EIT in clinical applications. A comparative analysis of the EIT hardware and the quality of the evaluation tools was not performed.
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Affiliation(s)
- I Frerichs
- Department of Anaesthesiological Research, Centre of Anaesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Germany.
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Frerichs I, Hahn G, Hellige G. Thoracic electrical impedance tomographic measurements during volume controlled ventilation-effects of tidal volume and positive end-expiratory pressure. IEEE TRANSACTIONS ON MEDICAL IMAGING 1999; 18:764-773. [PMID: 10571381 DOI: 10.1109/42.802754] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The aim of the study was to analyze thoracic electrical impedance tomographic (EIT) measurements accomplished under conditions comparable with clinical situations during artificial ventilation. Multiple EIT measurements were performed in pigs in three transverse thoracic planes during the volume controlled mode of mechanical ventilation at various tidal volumes (V(T)) and positive end-expiratory pressures (PEEP). The protocol comprised following ventilatory patterns: 1) V(T)(400, 500, 600, 700 ml) was varied in a random order at various constant PEEP levels and 2) PEEP (2, 5, 8, 11, 14 cm H2O) was randomly modified during ventilation with a constant V(T). The EIT technique was used to generate cross-sectional images of 1) regional lung ventilation and 2) regional shifts in lung volume with PEEP. The quantitative analysis was performed in terms of the tidal amplitude of the impedance change, reflecting the volume of delivered gas at various preset V(T) and the end-expiratory impedance change, revealing the variation of the lung volume at various PEEP levels. The results showed: 1) an increase in the tidal amplitude of the impedance change, proportional to the delivered V(T) at all constant PEEP levels, 2) a rising end-expiratory impedance change, with PEEP reflecting an increase in gas volume, and 3) a PEEP-dependent redistribution of the ventilated gas between the planes. The generated images and the quantitative results indicate the ability of EIT to identify regional changes in V(T) and lung volume during mechanical ventilation.
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Affiliation(s)
- I Frerichs
- Department of Anesthesiological Research, Center of Anesthesiology, Emergency, and Intensive Care Medicine, University of Göttingen, FRG
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Zerahn B, Jensen BV, Olsen F, Petersen JR, Kanstrup IL. The effect of thoracentesis on lung function and transthoracic electrical bioimpedance. Respir Med 1999; 93:196-201. [PMID: 10464878 DOI: 10.1016/s0954-6111(99)90008-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This study aimed to determine the relationship between improvement in lung function and changes in transthoracic electrical bioimpedance (TEB) after thoracentesis in patients with pleural effusions. Fifteen patients with pleural effusions due to either malignant (n = 8) or cardiac (n = 7) diseases were included. Pulmonary function was assessed before and after thoracentesis. During thoracentesis the patients were monitored with TEB. Using linear correlation analysis, the increases for each litre of aspirated thoracic fluid were: forced expiratory volume in 1 s (FEV1) 0.261; forced vital capacity (FVC) 0.331; total lung capacity (TLC) 0.58; and the lung diffusing capacity (DLCO); 2.4 ml min-1 mmHg-1. Baseline impedance increased by 2.3 Ohm l-1 aspirated thoracic fluid. The relative increase in baseline impedance was twice as high for patients with cancer as for patients with heart failure (P < 0.05). We found only minor changes in systolic blood pressure and mean arterial pressure. The improvements in diffusing capacity, airflow, and lung volumes after thoracentesis are correlated to an increase in baseline impedance, but changes are dependent on the primary disease.
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Affiliation(s)
- B Zerahn
- Department of Clinical Physiology and Nuclear Medicine, Herlev Hospital, University of Copenhagen, Denmark.
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Korsten HH, Roos AN. Noninvasive monitoring by electrical impedance techniques: Will it ever be an accepted clinical tool? Crit Care Med 1998; 26:425. [PMID: 9504562 DOI: 10.1097/00003246-199803000-00004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Boone K, Barber D, Brown B. Imaging with electricity: report of the European Concerted Action on Impedance Tomography. J Med Eng Technol 1997; 21:201-32. [PMID: 9429132 DOI: 10.3109/03091909709070013] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- K Boone
- University College, London, UK
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Griffiths H, Tucker MG, Sage J, Herrenden-Harker WG. An electrical impedance tomography microscope. Physiol Meas 1996; 17 Suppl 4A:A15-24. [PMID: 9001598 DOI: 10.1088/0967-3334/17/4a/004] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A circular array of 16 electrodes has been constructed for use as an electrical impedance tomography (EIT) microscope. The electrodes were made from 60 microns diameter gold wires anchored to a printed circuit board. The internal diameter of the array was 0.9 mm giving a theoretical spatial resolution of about 100 microns. For EIT imaging, the array was connected to an imaging system operating at 82 kHz. Static images of conducting and insulating filaments (cooper wire and human hair) in saline solution were obtained as well as dynamic imaging sequences of glass microspheres migrating through the array. The interelectrode impedance was typically 5 k omega and the transimpedances ranged from 14 to 210 omega.
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Affiliation(s)
- H Griffiths
- Department of Medical Physics and Bioengineering, University Hospital of Wales, Heath Park, Cardiff, UK
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Hahn G, Sipinková I, Baisch F, Hellige G. Changes in the thoracic impedance distribution under different ventilatory conditions. Physiol Meas 1995; 16:A161-73. [PMID: 8528115 DOI: 10.1088/0967-3334/16/3a/016] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The present study was performed with the aim of checking the suitability of EIT in imaging regional thoracic impedance variations during lung ventilation under predefined conditions and to compare EIT with established reference techniques. A new technique of functional EIT imaging designed to visualize physiologically relevant information from the sequentially registered series of thoracic distributions was introduced. Experiments were performed on five spontaneously breathing healthy subjects and on 12 anaesthetized supine pigs. 16 electrodes were placed around the thorax and consecutive transthoracic impedance distributions were measured at a rate of 1 Hz (Sheffield APT system mark I, IBEES, Sheffield, UK). Several voluntary breathing manoeuvres were performed in human subjects and the tracings of local impedance were compared with standard spirometry. In animal experiments EIT was applied during artificial ventilation at different ventilation rates and during stepwise passive emptying and filling of either one or both lungs while the respiratory muscles were relaxes. Further, selective blockade of lung regions resulting in regionally reduced ventilation was performed and the capability of EIT to follow and differentiate local ventilatory disturbances was checked by reference techniques (x-ray and staining methods). The experiments revealed an overall agreement between the spirometric and impedance data in all breathing patterns performed. A linear relationship between changes of the air content of the lungs and the regional thoracic impedance was shown (intraindividual correlation coefficient range, 0.986-0.999; n = 12 animals). The functional images of the impedance distribution across the thorax reproduced adequately the typical anatomical characteristics of the pig and the human thorax. The spatial resolution of EIT functional images was sufficient to differentiate lung areas corresponding to approximately 20 ml tissue volume. EIT with the additional evaluation procedure of functional imaging was shown to be a suitable and reliable method of imaging different ventilatory conditions with the potential to become a useful tool for monitoring respiratory function.
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Affiliation(s)
- G Hahn
- Department of Anaesthesiological Research, University of Göttingen, Germany
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