1
|
Zhang K, Li M, Liang H, Wang J, Yang F, Xu S, Abubakar A. Deep feature-domain matching for cardiac-related component separation from a chest electrical impedance tomography image series: proof-of-concept study. Physiol Meas 2022; 43. [PMID: 36265475 DOI: 10.1088/1361-6579/ac9c44] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 10/20/2022] [Indexed: 02/07/2023]
Abstract
Objectives.The cardiac-related component in chest electrical impedance tomography (EIT) measurement is of potential value to pulmonary perfusion monitoring and cardiac function measurement. In a spontaneous breathing case, cardiac-related signals experience serious interference from ventilation-related signals. Traditional cardiac-related signal-separation methods are usually based on certain features of signals. To further improve the separation accuracy, more comprehensive features of the signals should be exploited.Approach.We propose an unsupervised deep-learning method called deep feature-domain matching (DFDM), which exploits the feature-domain similarity of the desired signals and the breath-holding signals. This method is characterized by two sub-steps. In the first step, a novel Siamese network is designed and trained to learn common features of breath-holding signals; in the second step, the Siamese network is used as a feature-matching constraint between the separated signals and the breath-holding signals.Main results.The method is first tested using synthetic data, and the results show satisfactory separation accuracy. The method is then tested using the data of three patients with pulmonary embolism, and the consistency between the separated images and the radionuclide perfusion scanning images is checked qualitatively.Significance.The method uses a lightweight convolutional neural network for fast network training and inference. It is a potential method for dynamic cardiac-related signal separation in clinical settings.
Collapse
Affiliation(s)
- Ke Zhang
- Department of Electronic Engineering, Beijing National Research Center for Information Science and Technology (BNRist), Institute for Precision Medicine, Tsinghua University, Beijing 100084, People's Republic of China
| | - Maokun Li
- Department of Electronic Engineering, Beijing National Research Center for Information Science and Technology (BNRist), Institute for Precision Medicine, Tsinghua University, Beijing 100084, People's Republic of China
| | - Haiqing Liang
- TEDA International Cardiovascular Hospital, Tianjin 300457, People's Republic of China
| | - Juan Wang
- National Laboratory of Pattern Recognition (NLPR), Institute of Automation, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Fan Yang
- Department of Electronic Engineering, Beijing National Research Center for Information Science and Technology (BNRist), Institute for Precision Medicine, Tsinghua University, Beijing 100084, People's Republic of China
| | - Shenheng Xu
- Department of Electronic Engineering, Beijing National Research Center for Information Science and Technology (BNRist), Institute for Precision Medicine, Tsinghua University, Beijing 100084, People's Republic of China
| | - Aria Abubakar
- Schlumberger, Houston, TX 77056, United States of America
| |
Collapse
|
2
|
Jiang H, Han Y, Zheng X, Fang Q. Roles of electrical impedance tomography in lung transplantation. Front Physiol 2022; 13:986422. [PMID: 36407002 PMCID: PMC9669435 DOI: 10.3389/fphys.2022.986422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 10/25/2022] [Indexed: 11/06/2022] Open
Abstract
Lung transplantation is the preferred treatment method for patients with end-stage pulmonary disease. However, several factors hinder the progress of lung transplantation, including donor shortages, candidate selection, and various postoperative complications. Electrical impedance tomography (EIT) is a functional imaging tool that can be used to evaluate pulmonary ventilation and perfusion at the bedside. Among patients after lung transplantation, monitoring the graft’s pulmonary function is one of the most concerning issues. The feasible application of EIT in lung transplantation has been reported over the past few years, and this technique has gained increasing interest from multidisciplinary researchers. Nevertheless, physicians still lack knowledge concerning the potential applications of EIT in lung transplantation. We present an updated review of EIT in lung transplantation donors and recipients over the past few years, and discuss the potential use of ventilation- and perfusion-monitoring-based EIT in lung transplantation.
Collapse
Affiliation(s)
| | | | - Xia Zheng
- *Correspondence: Xia Zheng, ; Qiang Fang,
| | - Qiang Fang
- *Correspondence: Xia Zheng, ; Qiang Fang,
| |
Collapse
|
3
|
Brabant OA, Byrne DP, Sacks M, Moreno Martinez F, Raisis AL, Araos JB, Waldmann AD, Schramel JP, Ambrosio A, Hosgood G, Braun C, Auer U, Bleul U, Herteman N, Secombe CJ, Schoster A, Soares J, Beazley S, Meira C, Adler A, Mosing M. Thoracic Electrical Impedance Tomography-The 2022 Veterinary Consensus Statement. Front Vet Sci 2022; 9:946911. [PMID: 35937293 PMCID: PMC9354895 DOI: 10.3389/fvets.2022.946911] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 06/16/2022] [Indexed: 11/13/2022] Open
Abstract
Electrical impedance tomography (EIT) is a non-invasive real-time non-ionising imaging modality that has many applications. Since the first recorded use in 1978, the technology has become more widely used especially in human adult and neonatal critical care monitoring. Recently, there has been an increase in research on thoracic EIT in veterinary medicine. Real-time imaging of the thorax allows evaluation of ventilation distribution in anesthetised and conscious animals. As the technology becomes recognised in the veterinary community there is a need to standardize approaches to data collection, analysis, interpretation and nomenclature, ensuring comparison and repeatability between researchers and studies. A group of nineteen veterinarians and two biomedical engineers experienced in veterinary EIT were consulted and contributed to the preparation of this statement. The aim of this consensus is to provide an introduction to this imaging modality, to highlight clinical relevance and to include recommendations on how to effectively use thoracic EIT in veterinary species. Based on this, the consensus statement aims to address the need for a streamlined approach to veterinary thoracic EIT and includes: an introduction to the use of EIT in veterinary species, the technical background to creation of the functional images, a consensus from all contributing authors on the practical application and use of the technology, descriptions and interpretation of current available variables including appropriate statistical analysis, nomenclature recommended for consistency and future developments in thoracic EIT. The information provided in this consensus statement may benefit researchers and clinicians working within the field of veterinary thoracic EIT. We endeavor to inform future users of the benefits of this imaging modality and provide opportunities to further explore applications of this technology with regards to perfusion imaging and pathology diagnosis.
Collapse
Affiliation(s)
- Olivia A. Brabant
- School of Veterinary Medicine, Murdoch University, Perth, WA, Australia
| | - David P. Byrne
- School of Veterinary Medicine, Murdoch University, Perth, WA, Australia
| | - Muriel Sacks
- School of Veterinary Medicine, Murdoch University, Perth, WA, Australia
| | | | - Anthea L. Raisis
- School of Veterinary Medicine, Murdoch University, Perth, WA, Australia
| | - Joaquin B. Araos
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, United States
| | - Andreas D. Waldmann
- Department of Anaesthesiology and Intensive Care Medicine, Rostock University Medical Centre, Rostock, Germany
| | - Johannes P. Schramel
- Department of Anaesthesiology and Perioperative Intensive Care Medicine, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Aline Ambrosio
- Department of Surgery, Faculty of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil
| | - Giselle Hosgood
- School of Veterinary Medicine, Murdoch University, Perth, WA, Australia
| | - Christina Braun
- Department of Anaesthesiology and Perioperative Intensive Care Medicine, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Ulrike Auer
- Department of Anaesthesiology and Perioperative Intensive Care Medicine, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Ulrike Bleul
- Clinic of Reproductive Medicine, Department of Farm Animals, Vetsuisse-Faculty University Zurich, Zurich, Switzerland
| | - Nicolas Herteman
- Clinic for Equine Internal Medicine, Equine Hospital, Vetsuisse-Faculty, University of Zurich, Zurich, Switzerland
| | - Cristy J. Secombe
- School of Veterinary Medicine, Murdoch University, Perth, WA, Australia
| | - Angelika Schoster
- Clinic for Equine Internal Medicine, Equine Hospital, Vetsuisse-Faculty, University of Zurich, Zurich, Switzerland
| | - Joao Soares
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States
| | - Shannon Beazley
- Department of Small Animal Clinical Sciences, Western College Veterinary Medicine, Saskatoon, SK, Canada
| | - Carolina Meira
- Department of Clinical Diagnostics and Services, Anaesthesiology, Vetsuisse-Faculty, University of Zurich, Zurich, Switzerland
| | - Andy Adler
- Department of Systems and Computer Engineering, Carleton University, Ottawa, ON, Canada
| | - Martina Mosing
- School of Veterinary Medicine, Murdoch University, Perth, WA, Australia
| |
Collapse
|
4
|
Effects of PEEP on the relationship between tidal volume and total impedance change measured via electrical impedance tomography (EIT). J Clin Monit Comput 2022; 36:325-334. [PMID: 33492490 PMCID: PMC7829490 DOI: 10.1007/s10877-021-00651-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 01/06/2021] [Indexed: 01/31/2023]
Abstract
Electrical impedance tomography (EIT) is used in lung physiology monitoring. There is evidence that EIT is linearly associated with global tidal volume (VT) in clinically healthy patients where no positive end-expiratory pressure (PEEP) is applied. This linearity has not been challenged by altering lung conditions. The aim of this study was to determine the effect of PEEP on VT estimation, using EIT technology and spirometry, and observe the stability of the relationship under changing lung conditions. Twelve male castrated cattle (Steer), mean age 7.8 months (SD ± 1.7) were premedicated with xylazine followed by anaesthesia induction with ketamine and maintenance with halothane in oxygen via an endotracheal tube. An EIT belt was applied around the thorax at the level of the fifth intercostal space. Volume controlled ventilation was used. PEEP was increased in a stepwise manner from 0 to 5, 10 and 15 cmH2O. At each PEEP, the VT was increased stepwise from 5 to 10 and 15 mL kg-1. After a minute of stabilisation, total impedance change (VTEIT), using EIT and VT measured by a spirometer connected to a flow-partitioning device (VTSpiro) was recorded for the following minute before changing ventilator settings. Data was analysed using linear regression and multi variable analysis. There was a linear relationship between VTEIT and VTSpiro at all levels of PEEP with an R2 of 0.71, 0.68, 0.63 and 0.63 at 0, 5, 10 and 15 cmH2O, respectively. The variance in VTEIT was best described by peak inspiratory pressure (PIP) and PEEP (adjusted R2 0.82) while variance in VTSpiro was best described by PIP and airway deadspace (adjusted R2 0.76). The relationship between VTEIT and VTSpiro remains linear with changes in tidal volume, and stable across altered lung conditions. This may have application for monitoring and assessment in vivo.
Collapse
|
5
|
Xu M, He H, Long Y. Lung Perfusion Assessment by Bedside Electrical Impedance Tomography in Critically Ill Patients. Front Physiol 2021; 12:748724. [PMID: 34721072 PMCID: PMC8548642 DOI: 10.3389/fphys.2021.748724] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 09/13/2021] [Indexed: 12/02/2022] Open
Abstract
As a portable, radiation-free imaging modality, electrical impedance tomography (EIT) technology has shown promise in the bedside visual assessment of lung perfusion distribution in critically ill patients. The two main methods of EIT for assessing lung perfusion are the pulsatility and conductivity contrast (saline) bolus method. Increasing attention is being paid to the saline bolus EIT method in the evaluation of regional pulmonary perfusion in clinical practice. This study seeks to provide an overview of experimental and clinical studies with the aim of clarifying the progress made in the use of the saline bolus EIT method. Animal studies revealed that the saline bolus EIT method presented good consistency with single-photon emission CT (SPECT) in the evaluation of lung regional perfusion changes in various pathological conditions. Moreover, the saline bolus EIT method has been applied to assess the lung perfusion in a pulmonary embolism and the effect of positive end-expiratory pressure (PEEP) on regional ventilation/perfusion ratio (V/Q) and acute respiratory distress syndrome (ARDS) in several clinical studies. The implementation of saline boluses, data analyses, precision, and cutoff values varied among different studies, and a consensus must be reached regarding the clinical application of the saline bolus EIT method. Further study is required to validate the impact of the described saline bolus EIT method on decision-making, therapeutic management, and outcomes in critically ill patients.
Collapse
Affiliation(s)
- Mengru Xu
- State Key Laboratory of Complex Severe and Rare Diseases, Department of Critical Care Medicine, Peking Union Medical College, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Huaiwu He
- State Key Laboratory of Complex Severe and Rare Diseases, Department of Critical Care Medicine, Peking Union Medical College, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Yun Long
- State Key Laboratory of Complex Severe and Rare Diseases, Department of Critical Care Medicine, Peking Union Medical College, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| |
Collapse
|
6
|
Abstract
PURPOSE OF REVIEW Among noninvasive lung imaging techniques that can be employed at the bedside electrical impedance tomography (EIT) and lung ultrasound (LUS) can provide dynamic, repeatable data on the distribution regional lung ventilation and response to therapeutic manoeuvres.In this review, we will provide an overview on the rationale, basic functioning and most common applications of EIT and Point of Care Ultrasound (PoCUS, mainly but not limited to LUS) in the management of mechanically ventilated patients. RECENT FINDINGS The use of EIT in clinical practice is supported by several studies demonstrating good correlation between impedance tomography data and other validated methods of assessing lung aeration during mechanical ventilation. Similarly, LUS also correlates with chest computed tomography in assessing lung aeration, its changes and several pathological conditions, with superiority over other techniques. Other PoCUS applications have shown to effectively complement the LUS ultrasound assessment of the mechanically ventilated patient. SUMMARY Bedside techniques - such as EIT and PoCUS - are becoming standards of the care for mechanically ventilated patients to monitor the changes in lung aeration, ventilation and perfusion in response to treatment and to assess weaning from mechanical ventilation.
Collapse
|
7
|
Hopkins SR. Ventilation/Perfusion Relationships and Gas Exchange: Measurement Approaches. Compr Physiol 2020; 10:1155-1205. [PMID: 32941684 DOI: 10.1002/cphy.c180042] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Ventilation-perfusion ( V ˙ A / Q ˙ ) matching, the regional matching of the flow of fresh gas to flow of deoxygenated capillary blood, is the most important mechanism affecting the efficiency of pulmonary gas exchange. This article discusses the measurement of V ˙ A / Q ˙ matching with three broad classes of techniques: (i) those based in gas exchange, such as the multiple inert gas elimination technique (MIGET); (ii) those derived from imaging techniques such as single-photon emission computed tomography (SPECT), positron emission tomography (PET), magnetic resonance imaging (MRI), computed tomography (CT), and electrical impedance tomography (EIT); and (iii) fluorescent and radiolabeled microspheres. The focus is on the physiological basis of these techniques that provide quantitative information for research purposes rather than qualitative measurements that are used clinically. The fundamental equations of pulmonary gas exchange are first reviewed to lay the foundation for the gas exchange techniques and some of the imaging applications. The physiological considerations for each of the techniques along with advantages and disadvantages are briefly discussed. © 2020 American Physiological Society. Compr Physiol 10:1155-1205, 2020.
Collapse
Affiliation(s)
- Susan R Hopkins
- Departments of Medicine and Radiology, University of California, San Diego, California, USA
| |
Collapse
|
8
|
Electrical Impedance Tomography for Cardio-Pulmonary Monitoring. J Clin Med 2019; 8:jcm8081176. [PMID: 31394721 PMCID: PMC6722958 DOI: 10.3390/jcm8081176] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 08/05/2019] [Accepted: 08/06/2019] [Indexed: 12/14/2022] Open
Abstract
Electrical impedance tomography (EIT) is a bedside monitoring tool that noninvasively visualizes local ventilation and arguably lung perfusion distribution. This article reviews and discusses both methodological and clinical aspects of thoracic EIT. Initially, investigators addressed the validation of EIT to measure regional ventilation. Current studies focus mainly on its clinical applications to quantify lung collapse, tidal recruitment, and lung overdistension to titrate positive end-expiratory pressure (PEEP) and tidal volume. In addition, EIT may help to detect pneumothorax. Recent studies evaluated EIT as a tool to measure regional lung perfusion. Indicator-free EIT measurements might be sufficient to continuously measure cardiac stroke volume. The use of a contrast agent such as saline might be required to assess regional lung perfusion. As a result, EIT-based monitoring of regional ventilation and lung perfusion may visualize local ventilation and perfusion matching, which can be helpful in the treatment of patients with acute respiratory distress syndrome (ARDS).
Collapse
|
9
|
Vasques F, Sanderson B, Barrett NA, Camporota L. Monitoring of regional lung ventilation using electrical impedance tomography. Minerva Anestesiol 2019; 85:1231-1241. [PMID: 30945516 DOI: 10.23736/s0375-9393.19.13477-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Among recent lung imaging techniques and devices, electrical impedance tomography (EIT) can provide dynamic information on the distribution regional lung ventilation. EIT images possess a high temporal and functional resolution allowing the visualization of dynamic physiological and pathological changes on a breath-by-breath basis. EIT detects changes in electric impedance (i.e., changes in gas/fluid ratio) and describes them in real time, both visually through images and waveforms, and numerically, allowing the clinician to monitor disease evolution and response to treatment. The use of EIT in clinical practice is supported by several studies demonstrating a good correlation between impedance tomography data and other validated methods of measuring lung volume. In this review, we will provide an overview on the rationale, basic functioning and most common applications of EIT in the management of mechanically ventilated patients.
Collapse
Affiliation(s)
- Francesco Vasques
- Department of Adult Critical Care, Guy's and St Thomas' NHS Foundation Trust, King's Health Partners, London, UK.,Division of Centre of Human Applied Physiological Sciences, King's College London, London, UK
| | - Barnaby Sanderson
- Department of Adult Critical Care, Guy's and St Thomas' NHS Foundation Trust, King's Health Partners, London, UK.,Division of Centre of Human Applied Physiological Sciences, King's College London, London, UK
| | - Nicholas A Barrett
- Department of Adult Critical Care, Guy's and St Thomas' NHS Foundation Trust, King's Health Partners, London, UK.,Division of Centre of Human Applied Physiological Sciences, King's College London, London, UK
| | - Luigi Camporota
- Department of Adult Critical Care, Guy's and St Thomas' NHS Foundation Trust, King's Health Partners, London, UK - .,Division of Centre of Human Applied Physiological Sciences, King's College London, London, UK
| |
Collapse
|
10
|
da Silva Ramos FJ, Hovnanian A, Souza R, Azevedo LCP, Amato MBP, Costa ELV. Estimation of Stroke Volume and Stroke Volume Changes by Electrical Impedance Tomography. Anesth Analg 2018; 126:102-110. [PMID: 28742775 DOI: 10.1213/ane.0000000000002271] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Electrical impedance tomography (EIT) is a noninvasive imaging method that identifies changes in air and blood volume based on thoracic impedance changes. Recently, there has been growing interest in EIT to measure stroke volume (SV). The objectives of this study are as follows: (1) to evaluate the ability of systolic impedance variations (ΔZsys) to track changes in SV in relation to a baseline condition; (2) to assess the relationship of ΔZsys and SV in experimental subjects; and (3) to identify the influence of body dimensions on the relationship between ΔZsys and SV. METHODS Twelve Agroceres pigs were instrumented with transpulmonary thermodilution catheter and EIT and were mechanically ventilated in a random order using different settings of tidal volume (VT) and positive end-expiratory pressure (PEEP): VT 10 mL·kg and PEEP 10 cm H2O, VT 10 mL·kg and PEEP 5 cm H2O, VT 6 mL·kg and PEEP 10 cm H2O, and VT 6 mL·kg and PEEP 5 cm H2O. After baseline data collection, subjects were submitted to hemorrhagic shock and successive fluid challenges. RESULTS A total of 204 paired measurements of SV and ΔZsys were obtained. The 4-quadrant plot showed acceptable trending ability with a concordance rate of 91.2%. Changes in ΔZsys after fluid challenges presented an area under the curve of 0.83 (95% confidence interval, 0.74-0.92) to evaluate SV changes. Conversely, the linear association between ΔZsys and SV was poor, with R from linear mixed model of 0.35. Adding information on body dimensions improved the linear association between ΔZsys and SV up to R from linear mixed model of 0.85. CONCLUSIONS EIT showed good trending ability and is a promising hemodynamic monitoring tool. Measurements of absolute SV require that body dimensions be taken into account.
Collapse
Affiliation(s)
- Fernando José da Silva Ramos
- From the Department of Intensive Care and Anesthesiology Research Laboratory, Research and Education Institute, Hospital Sírio-Libanês, São Paulo, Brazil
| | - André Hovnanian
- From the Department of Intensive Care and Anesthesiology Research Laboratory, Research and Education Institute, Hospital Sírio-Libanês, São Paulo, Brazil.,Respiratory Intensive Care Unit, University of São Paulo School of Medicine, São Paulo, Brazil
| | - Rogério Souza
- Respiratory Intensive Care Unit, University of São Paulo School of Medicine, São Paulo, Brazil
| | - Luciano C P Azevedo
- From the Department of Intensive Care and Anesthesiology Research Laboratory, Research and Education Institute, Hospital Sírio-Libanês, São Paulo, Brazil
| | - Marcelo B P Amato
- Respiratory Intensive Care Unit, University of São Paulo School of Medicine, São Paulo, Brazil
| | - Eduardo L V Costa
- From the Department of Intensive Care and Anesthesiology Research Laboratory, Research and Education Institute, Hospital Sírio-Libanês, São Paulo, Brazil.,Respiratory Intensive Care Unit, University of São Paulo School of Medicine, São Paulo, Brazil
| |
Collapse
|
11
|
Electrical impedance tomography: Amplitudes of cardiac related impedance changes in the lung are highly position dependent. PLoS One 2017; 12:e0188313. [PMID: 29145478 PMCID: PMC5690592 DOI: 10.1371/journal.pone.0188313] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Accepted: 11/03/2017] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Electrical impedance tomography (EIT) is used on the thorax to measure impedance changes due to the presence of air and blood in the lung. This experimental study was performed to investigate the effect of posture on cardiac and respiratory related impedance changes. METHODS EIT measurements were performed on 14 healthy subjects in left-, right lateral, prone, supine and upright positions. Simultaneously, tidal volume was recorded with an ultrasonic flowmeter. For image reconstruction, the classic Sheffield back-projection and three variants of the modern GREIT algorithm were applied with two different reference frames. Amplitudes of cardiac- and respiratory impedance changes were extracted and compared between the positions. RESULTS We found significant differences in both cardiac and respiratory amplitudes between postures. Especially, supine and upright positions showed dramatic changes in amplitude. These differences between postures were unaffected by the change of reference frames in all reconstruction methods except of the classic Sheffield back projection. Possible sources that explain the observed posture dependency are discussed. CONCLUSION Researchers and clinicians need to be aware of this phenomenon when comparing EIT amplitudes in different body positions.
Collapse
|
12
|
Hochhausen N, Dohmeier H, Rossaint R, Czaplik M. Monitoring of cardiac output and lung ventilation by Electrical Impedance Tomography in a porcine model of acute lung injury. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2017:352-355. [PMID: 29059883 DOI: 10.1109/embc.2017.8036835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Adequate medical treatment of the Acute Respiratory Distress Syndrome is still challenging since patient-individual aspects have to be taken into account. Lung protective ventilation and hemodynamic stability have always been two of the most crucial aims of intensive care therapy. For both aspects, a continuous - preferably non-invasive - monitoring is desirable that is available at the bedside. Unfortunately, there is no technique clinically established yet, that provides both measurement of cardiac stroke volume and ventilation dynamics in real-time. Electrical Impedance Tomography (EIT) is a promising technique to close this gap. The aim of the study was to investigate if stroke volume can be estimated by a self-developed software using EIT-based image analysis. In addition, two EIT-derived parameters, namely Global Inhomogeneity Index (GII) and Impedance Ratio (IR), were calculated to evaluate homogeneity of air distribution. Experimental acute lung injury (ALI) was provoked in seven female pigs (German Landrace) by lipopolysaccharide (LPS). All animals suffered from experimental ALI 3 to 4 hours after LPS infusion. At defined time points, respiratory and hemodynamic parameters, blood gas analyses and EIT-recordings were performed. Eight hours after ALI, animals were euthanized. Stroke volume, derived from pulmonary artery catheter (PAC), decreased continuously up to four hours after ALI. Then, stroke volume increased slightly. Stroke volume, derived from the self-developed tool, showed the same characteristics (p=0.047, r = 0.365). In addition to the GII and IR individually, both classified scores showed a high correlation with the Horowitz Index, defined as paO2/FiO2. To conclude, EIT-derived measures enabled a reliable estimation of cardiac stroke volume and regional distribution of ventilation.
Collapse
|
13
|
Trepte CJC, Phillips CR, Solà J, Adler A, Haas SA, Rapin M, Böhm SH, Reuter DA. Electrical impedance tomography (EIT) for quantification of pulmonary edema in acute lung injury. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2016; 20:18. [PMID: 26796635 PMCID: PMC4722629 DOI: 10.1186/s13054-015-1173-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 12/13/2015] [Indexed: 01/19/2023]
Abstract
Background Assessment of pulmonary edema is a key factor in monitoring and guidance of therapy in critically ill patients. To date, methods available at the bedside for estimating the physiologic correlate of pulmonary edema, extravascular lung water, often are unreliable or require invasive measurements. The aim of the present study was to develop a novel approach to reliably assess extravascular lung water by making use of the functional imaging capabilities of electrical impedance tomography. Methods Thirty domestic pigs were anesthetized and randomized to three different groups. Group 1 was a sham group with no lung injury. Group 2 had acute lung injury induced by saline lavage. Group 3 had vascular lung injury induced by intravenous injection of oleic acid. A novel, noninvasive technique using changes in thoracic electrical impedance with lateral body rotation was used to measure a new metric, the lung water ratioEIT, which reflects total extravascular lung water. The lung water ratioEIT was compared with postmortem gravimetric lung water analysis and transcardiopulmonary thermodilution measurements. Results A significant correlation was found between extravascular lung water as measured by postmortem gravimetric analysis and electrical impedance tomography (r = 0.80; p < 0.05). Significant changes after lung injury were found in groups 2 and 3 in extravascular lung water derived from transcardiopulmonary thermodilution as well as in measurements derived by lung water ratioEIT. Conclusions Extravascular lung water could be determined noninvasively by assessing characteristic changes observed on electrical impedance tomograms during lateral body rotation. The novel lung water ratioEIT holds promise to become a noninvasive bedside measure of pulmonary edema.
Collapse
Affiliation(s)
- Constantin J C Trepte
- Department of Anaesthesiology, Center for Anaesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, D-20246, Hamburg, Germany.
| | - Charles R Phillips
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Center for Intensive Care Research, Oregon Health & Science University, Portland, OR, USA.
| | - Josep Solà
- CSEM Centre Suisse d'Electronique et de Microtechnique SA, Neuchâtel, Switzerland.
| | - Andy Adler
- Systems and Computer Engineering, Carleton University, Ottawa, ON, Canada.
| | - Sebastian A Haas
- Department of Anaesthesiology, Center for Anaesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, D-20246, Hamburg, Germany.
| | - Michael Rapin
- CSEM Centre Suisse d'Electronique et de Microtechnique SA, Neuchâtel, Switzerland.
| | | | - Daniel A Reuter
- Department of Anaesthesiology, Center for Anaesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, D-20246, Hamburg, Germany.
| |
Collapse
|
14
|
Pikkemaat R, Lundin S, Stenqvist O, Hilgers RD, Leonhardt S. Recent Advances in and Limitations of Cardiac Output Monitoring by Means of Electrical Impedance Tomography. Anesth Analg 2014; 119:76-83. [DOI: 10.1213/ane.0000000000000241] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
15
|
LI Y, TESSELAAR E, BORGES JB, BÖHM SH, SJÖBERG F, JANEROT-SJÖBERG B. Hyperoxia affects the regional pulmonary ventilation/perfusion ratio: an electrical impedance tomography study. Acta Anaesthesiol Scand 2014; 58:716-25. [PMID: 24762189 DOI: 10.1111/aas.12323] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/13/2014] [Indexed: 12/13/2022]
Abstract
BACKGROUND The way in which hyperoxia affects pulmonary ventilation and perfusion is not fully understood. We investigated how an increase in oxygen partial pressure in healthy young volunteers affects pulmonary ventilation and perfusion measured by thoracic electrical impedance tomography (EIT). METHODS Twelve semi-supine healthy male volunteers aged 21-36 years were studied while breathing room air and air-oxygen mixtures (FiO2) that resulted in predetermined transcutaneous oxygen partial pressures (tcPO2) of 20, 40 and 60 kPa. The magnitude of ventilation (ΔZv) and perfusion (ΔZQ)-related changes in cyclic impedance variations, were determined using an EIT prototype equipped with 32 electrodes around the thorax. Regional changes in ventral and dorsal right lung ventilation (V) and perfusion (Q) were estimated, and V/Q ratios calculated. RESULTS There were no significant changes in ΔZv with increasing tcPO2 levels. ΔZQ in the dorsal lung increased with increasing tcPO2 (P = 0.01), whereas no such change was seen in the ventral lung. There was a simultaneous decrease in V/Q ratio in the dorsal region during hyperoxia (P = 0.04). Two subjects did not reach a tcPO2 of 60 kPa despite breathing 100% oxygen. CONCLUSION These results indicate that breathing increased concentrations of oxygen induces pulmonary vasodilatation in the dorsal lung even at small increases in FiO2. Ventilation remains unchanged. Local mismatch of ventilation and perfusion occurs in young healthy men, and the change in ventilation/perfusion ratio can be determined non-invasively by EIT.
Collapse
Affiliation(s)
- Y. LI
- Department of Anesthesiology; Shaoxing People's Hospital of Zhejiang University; Shaoxing City China
- Department of Clinical and Experimental Medicine; Linköping University; Linköping Sweden
| | - E. TESSELAAR
- Department of Clinical and Experimental Medicine; Linköping University; Linköping Sweden
| | - J. B. BORGES
- Hedenstierna Laboratory; Department of Surgical Sciences; Section of Anesthesiology & Critical Care; Uppsala University; Uppsala Sweden
- Laboratório de Pneumologia LIM-09; Disciplina de Pneumologia; Heart Institute (Incor); Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo; São Paulo Brazil
| | | | - F. SJÖBERG
- Department of Clinical and Experimental Medicine; Linköping University; Linköping Sweden
- Department of Hand; Plastic Surgery and Intensive Care; Linköping University Hospital; Linköping Sweden
| | - B. JANEROT-SJÖBERG
- Department of Clinical Science; Intervention and Technology; Karolinska Institutet; Stockholm Sweden
- Department of Clinical Physiology; Karolinska University Hospital; Stockholm Sweden
- School of Technology and Health; KTH; Royal Institute of Technology; Stockholm Sweden
| |
Collapse
|
16
|
Moens Y, Schramel JP, Tusman G, Ambrisko TD, Solà J, Brunner JX, Kowalczyk L, Böhm SH. Variety of non-invasive continuous monitoring methodologies including electrical impedance tomography provides novel insights into the physiology of lung collapse and recruitment – case report of an anaesthetized horse. Vet Anaesth Analg 2014; 41:196-204. [DOI: 10.1111/vaa.12098] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
17
|
Caruana LR, Paratz J, Chang AT, Fraser JF. Electrical impedance tomography in the clinical assessment of lung volumes following recruitment manoeuvres. PHYSICAL THERAPY REVIEWS 2013. [DOI: 10.1179/1743288x10y.0000000021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
|
18
|
|
19
|
Electrical impedance tomography: the holy grail of ventilation and perfusion monitoring? Intensive Care Med 2012; 38:1917-29. [DOI: 10.1007/s00134-012-2684-z] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 08/08/2012] [Indexed: 01/08/2023]
|
20
|
Abstract
Several methods allow regional gas exchange to be inferred from imaging of regional ventilation and perfusion (V/Q) ratios. Each method measures slightly different aspects of gas exchange and has inherent advantages and drawbacks that are reviewed. Single photon emission computed tomography can provide regional measure of ventilation and perfusion from which regional V/Q ratios can be derived. PET methods using inhaled or intravenously administered nitrogen-13 provide imaging of both regional blood flow, shunt, and ventilation. Electric impedance tomography has recently been refined to allow simultaneous measurements of both regional ventilation and blood flow. MRI methods utilizing hyperpolarized helium-3 or xenon-129 are currently being refined and have been used to estimate local PaO(2) in both humans and animals. Microsphere methods are included in this review as they provide measurements of regional ventilation and perfusion in animals. One of their advantages is their greater spatial resolution than most imaging methods and the ability to use them as gold standards against which new imaging methods can be tested. In general, the reviewed methods differ in characteristics such as spatial resolution, possibility of repeated measurements, radiation exposure, availability, expensiveness, and their current stage of development.
Collapse
Affiliation(s)
- Johan Petersson
- Department of Anesthesiology and Intensive Care, Karolinska University Hospital Solna, Stockholm, Sweden.
| | | |
Collapse
|
21
|
Adler A, Amato MB, Arnold JH, Bayford R, Bodenstein M, Böhm SH, Brown BH, Frerichs I, Stenqvist O, Weiler N, Wolf GK. Whither lung EIT: Where are we, where do we want to go and what do we need to get there? Physiol Meas 2012; 33:679-94. [DOI: 10.1088/0967-3334/33/5/679] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
22
|
Nguyen DT, Jin C, Thiagalingam A, McEwan AL. A review on electrical impedance tomography for pulmonary perfusion imaging. Physiol Meas 2012; 33:695-706. [DOI: 10.1088/0967-3334/33/5/695] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
23
|
Leonhardt S, Pikkemaat R, Stenqvist O, Lundin S. Electrical Impedance Tomography for hemodynamic monitoring. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2012:122-125. [PMID: 23365847 DOI: 10.1109/embc.2012.6345886] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Electrical Impedance Tomography (EIT) is a known technique to monitor impedance changes in a cross-section of a body segment, which recently gained increasing interest for regional ventilation monitoring. In this paper, we focus on hemodynamic monitoring using EIT. Past and ongoing research activities to obtain cardiac related signals and regional perfusion information from EIT image streams are summarized. Finally, we present some preliminary results on stroke volume estimation using EIT.
Collapse
Affiliation(s)
- Steffen Leonhardt
- Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University, D-52074 Aachen, Germany
| | | | | | | |
Collapse
|
24
|
Borges JB, Suarez-Sipmann F, Bohm SH, Tusman G, Melo A, Maripuu E, Sandström M, Park M, Costa ELV, Hedenstierna G, Amato M. Regional lung perfusion estimated by electrical impedance tomography in a piglet model of lung collapse. J Appl Physiol (1985) 2011; 112:225-36. [PMID: 21960654 DOI: 10.1152/japplphysiol.01090.2010] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The assessment of the regional match between alveolar ventilation and perfusion in critically ill patients requires simultaneous measurements of both parameters. Ideally, assessment of lung perfusion should be performed in real-time with an imaging technology that provides, through fast acquisition of sequential images, information about the regional dynamics or regional kinetics of an appropriate tracer. We present a novel electrical impedance tomography (EIT)-based method that quantitatively estimates regional lung perfusion based on first-pass kinetics of a bolus of hypertonic saline contrast. Pulmonary blood flow was measured in six piglets during control and unilateral or bilateral lung collapse conditions. The first-pass kinetics method showed good agreement with the estimates obtained by single-photon-emission computerized tomography (SPECT). The mean difference (SPECT minus EIT) between fractional blood flow to lung areas suffering atelectasis was -0.6%, with a SD of 2.9%. This method outperformed the estimates of lung perfusion based on impedance pulsatility. In conclusion, we describe a novel method based on EIT for estimating regional lung perfusion at the bedside. In both healthy and injured lung conditions, the distribution of pulmonary blood flow as assessed by EIT agreed well with the one obtained by SPECT. The method proposed in this study has the potential to contribute to a better understanding of the behavior of regional perfusion under different lung and therapeutic conditions.
Collapse
Affiliation(s)
- João Batista Borges
- Department of Surgical Sciences, Section of Anaesthesiology and Critical Care, Uppsala University, Uppsala, Sweden.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Grant CA, Pham T, Hough J, Riedel T, Stocker C, Schibler A. Measurement of ventilation and cardiac related impedance changes with electrical impedance tomography. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2011; 15:R37. [PMID: 21266025 PMCID: PMC3222074 DOI: 10.1186/cc9985] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2010] [Revised: 11/03/2010] [Accepted: 01/25/2011] [Indexed: 11/10/2022]
Abstract
INTRODUCTION Electrical impedance tomography (EIT) has been shown to be able to distinguish both ventilation and perfusion. With adequate filtering the regional distributions of both ventilation and perfusion and their relationships could be analysed. Several methods of separation have been suggested previously, including breath holding, electrocardiograph (ECG) gating and frequency filtering. Many of these methods require interventions inappropriate in a clinical setting. This study therefore aims to extend a previously reported frequency filtering technique to a spontaneously breathing cohort and assess the regional distributions of ventilation and perfusion and their relationship. METHODS Ten healthy adults were measured during a breath hold and while spontaneously breathing in supine, prone, left and right lateral positions. EIT data were analysed with and without filtering at the respiratory and heart rate. Profiles of ventilation, perfusion and ventilation/perfusion related impedance change were generated and regions of ventilation and pulmonary perfusion were identified and compared. RESULTS Analysis of the filtration technique demonstrated its ability to separate the ventilation and cardiac related impedance signals without negative impact. It was, therefore, deemed suitable for use in this spontaneously breathing cohort.Regional distributions of ventilation, perfusion and the combined ΔZV/ΔZQ were calculated along the gravity axis and anatomically in each position. Along the gravity axis, gravity dependence was seen only in the lateral positions in ventilation distribution, with the dependent lung being better ventilated regardless of position. This gravity dependence was not seen in perfusion.When looking anatomically, differences were only apparent in the lateral positions. The lateral position ventilation distributions showed a difference in the left lung, with the right lung maintaining a similar distribution in both lateral positions. This is likely caused by more pronounced anatomical changes in the left lung when changing positions. CONCLUSIONS The modified filtration technique was demonstrated to be effective in separating the ventilation and perfusion signals in spontaneously breathing subjects. Gravity dependence was seen only in ventilation distribution in the left lung in lateral positions, suggesting gravity based shifts in anatomical structures. Gravity dependence was not seen in any perfusion distributions.
Collapse
Affiliation(s)
- Caroline A Grant
- Paediatric Critical Care Research Group, Paediatric Intensive Care Unit, Mater Children's Hospital, 550 Stanley Street, South Brisbane, Queensland 4101, Australia.
| | | | | | | | | | | |
Collapse
|
26
|
Fagerberg A, Söndergaard S, Karason S, Aneman A. Electrical impedance tomography and heterogeneity of pulmonary perfusion and ventilation in porcine acute lung injury. Acta Anaesthesiol Scand 2009; 53:1300-9. [PMID: 19719814 DOI: 10.1111/j.1399-6576.2009.02103.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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 (Z(V)) and perfusion (Z(Q)) were monitored globally and bilaterally in four regions of interest (ROIs) of the EIT image. The distribution and ratio of Z(V) and Z(Q) 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 Z(Q) but not Z(V). Lung compliance progressively decreased with a ventral redistribution of Z(V). A concomitant dorsal redistribution of Z(Q) resulted in mismatch of global (from Z(V)/Z(Q) 1.1+/-0.1 to 0.83+/-0.3) and notably dorsal (from Z(V)/Z(Q) 0.86+/-0.4 to 0.51+/-0.3) V and Q. Changes in global Z(V)/Z(Q) correlated with changes in the alveolar-arterial oxygen difference (r(2)=0.65, P<0.05), venous admixture (r(2)=0.66, P<0.05) and fractional alveolar dead space (r(2)=0.61, P<0.05). Decreased end-expiratory Z(V) correlated with decreased FRC (r(2)=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.
Collapse
Affiliation(s)
- A Fagerberg
- Department of Anaesthesiology and Intensive Care, Sahlgrenska University Hospital, Blå Stråket 5, Gothenburg, Sweden
| | | | | | | |
Collapse
|
27
|
Fagerberg A, Stenqvist O, Aneman A. Electrical impedance tomography applied to assess matching of pulmonary ventilation and perfusion in a porcine experimental model. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2009; 13:R34. [PMID: 19265527 PMCID: PMC2689466 DOI: 10.1186/cc7741] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Revised: 11/27/2008] [Accepted: 03/05/2009] [Indexed: 11/10/2022]
Abstract
INTRODUCTION Electrical impedance tomography (EIT) can be used to measure impedance changes related to the thoracic content of air and blood. Few studies, however, have utilised EIT to make concurrent measurements of ventilation and perfusion. This experimental study was performed to investigate the feasibility of EIT to describe ventilation/perfusion (V/Q) matching after acute changes of pulmonary perfusion and aeration. METHODS Six mechanically ventilated, anaesthetised pigs in the supine position were studied at baseline, after inflation of a balloon in the inferior caval vein (Binfl) to reduce cardiac output and after an increased positive end-expiratory pressure (PEEP) of 20 cmH2O (PEEP20) to increase pulmonary aeration. EIT measurements were performed at the mid-thoracic level to measure the amplitude of impedance changes related to ventilation (ZV) and perfusion (ZQ), both globally and in four defined regions of interest (ROI) extending from the ventral to dorsal distance. RESULTS A largely parallel distribution of ZV and ZQ in all four ROIs during baseline conditions corresponded to a bell-shaped frequency distribution of ZV/ZQ ratios with only moderate scatter. Binfl and PEEP20 with unchanged tidal volumes significantly increased the mismatch of regional ZV and ZQ, the scatter of ZV/ZQ ratios and the heterogeneity of the ZV/ZQ frequency distribution. Significant positive and negative correlations were demonstrated between fractional alveolar dead space (r2 = 0.63 [regression coefficient]) and venous admixture (r2 = 0.48), respectively, and the global ZV/ZQ ratio. CONCLUSIONS EIT may be used to monitor the distribution of pulmonary ventilation and perfusion making detailed studies of V/Q matching possible.
Collapse
Affiliation(s)
- Anneli Fagerberg
- Department of Anaesthesiology and Intensive Care, The Sahlgrenska Academy, Bla Straket 5, Gothenburg, SE 413 45, Sweden
| | | | | |
Collapse
|