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Frerichs I, Schädler D, Becher T. Setting positive end-expiratory pressure by using electrical impedance tomography. Curr Opin Crit Care 2024; 30:43-52. [PMID: 38085866 DOI: 10.1097/mcc.0000000000001117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
PURPOSE OF REVIEW This review presents the principles and possibilities of setting positive end-expiratory pressure (PEEP) using electrical impedance tomography (EIT). It summarizes the major findings of recent studies where EIT was applied to monitor the effects of PEEP on regional lung function and to guide the selection of individualized PEEP setting. RECENT FINDINGS The most frequent approach of utilizing EIT for the assessment of PEEP effects and the PEEP setting during the time period from January 2022 till June 2023 was based on the analysis of pixel tidal impedance variation, typically acquired during stepwise incremental and/or decremental PEEP variation. The most common EIT parameters were the fraction of ventilation in various regions of interest, global inhomogeneity index, center of ventilation, silent spaces, and regional compliance of the respiratory system. The studies focused mainly on the spatial and less on the temporal distribution of ventilation. Contrast-enhanced EIT was applied in a few studies for the estimation of ventilation/perfusion matching. SUMMARY The availability of commercial EIT devices resulted in an increase in clinical studies using this bedside imaging technology in neonatal, pediatric and adult critically ill patients. The clinical interest in EIT became evident but the potential of this method in clinical decision-making still needs to be fully exploited.
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Affiliation(s)
- Inéz Frerichs
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
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Grasselli G, Calfee CS, Camporota L, Poole D, Amato MBP, Antonelli M, Arabi YM, Baroncelli F, Beitler JR, Bellani G, Bellingan G, Blackwood B, Bos LDJ, Brochard L, Brodie D, Burns KEA, Combes A, D'Arrigo S, De Backer D, Demoule A, Einav S, Fan E, Ferguson ND, Frat JP, Gattinoni L, Guérin C, Herridge MS, Hodgson C, Hough CL, Jaber S, Juffermans NP, Karagiannidis C, Kesecioglu J, Kwizera A, Laffey JG, Mancebo J, Matthay MA, McAuley DF, Mercat A, Meyer NJ, Moss M, Munshi L, Myatra SN, Ng Gong M, Papazian L, Patel BK, Pellegrini M, Perner A, Pesenti A, Piquilloud L, Qiu H, Ranieri MV, Riviello E, Slutsky AS, Stapleton RD, Summers C, Thompson TB, Valente Barbas CS, Villar J, Ware LB, Weiss B, Zampieri FG, Azoulay E, Cecconi M. ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies. Intensive Care Med 2023; 49:727-759. [PMID: 37326646 PMCID: PMC10354163 DOI: 10.1007/s00134-023-07050-7] [Citation(s) in RCA: 193] [Impact Index Per Article: 193.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 03/24/2023] [Indexed: 06/17/2023]
Abstract
The aim of these guidelines is to update the 2017 clinical practice guideline (CPG) of the European Society of Intensive Care Medicine (ESICM). The scope of this CPG is limited to adult patients and to non-pharmacological respiratory support strategies across different aspects of acute respiratory distress syndrome (ARDS), including ARDS due to coronavirus disease 2019 (COVID-19). These guidelines were formulated by an international panel of clinical experts, one methodologist and patients' representatives on behalf of the ESICM. The review was conducted in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement recommendations. We followed the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach to assess the certainty of evidence and grade recommendations and the quality of reporting of each study based on the EQUATOR (Enhancing the QUAlity and Transparency Of health Research) network guidelines. The CPG addressed 21 questions and formulates 21 recommendations on the following domains: (1) definition; (2) phenotyping, and respiratory support strategies including (3) high-flow nasal cannula oxygen (HFNO); (4) non-invasive ventilation (NIV); (5) tidal volume setting; (6) positive end-expiratory pressure (PEEP) and recruitment maneuvers (RM); (7) prone positioning; (8) neuromuscular blockade, and (9) extracorporeal life support (ECLS). In addition, the CPG includes expert opinion on clinical practice and identifies the areas of future research.
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Affiliation(s)
- Giacomo Grasselli
- Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
- Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy.
| | - Carolyn S Calfee
- Division of Pulmonary, Critical Care, Allergy and Sleep Medicine, Department of Medicine, University of California San Francisco, San Francisco, CA, USA
| | - Luigi Camporota
- Department of Adult Critical Care, Guy's and St Thomas' NHS Foundation Trust, London, UK
- Centre for Human and Applied Physiological Sciences, King's College London, London, UK
| | - Daniele Poole
- Operative Unit of Anesthesia and Intensive Care, S. Martino Hospital, Belluno, Italy
| | | | - Massimo Antonelli
- Department of Anesthesiology Intensive Care and Emergency Medicine, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
- Università Cattolica del Sacro Cuore, Rome, Italy
| | - Yaseen M Arabi
- Intensive Care Department, Ministry of the National Guard - Health Affairs, Riyadh, Kingdom of Saudi Arabia
- King Saud bin Abdulaziz University for Health Sciences, Riyadh, Kingdom of Saudi Arabia
- King Abdullah International Medical Research Center, Riyadh, Kingdom of Saudi Arabia
| | - Francesca Baroncelli
- Department of Anesthesia and Intensive Care, San Giovanni Bosco Hospital, Torino, Italy
| | - Jeremy R Beitler
- Center for Acute Respiratory Failure and Division of Pulmonary, Allergy and Critical Care Medicine, Columbia University, New York, NY, USA
| | - Giacomo Bellani
- Centre for Medical Sciences - CISMed, University of Trento, Trento, Italy
- Department of Anesthesia and Intensive Care, Santa Chiara Hospital, APSS Trento, Trento, Italy
| | - Geoff Bellingan
- Intensive Care Medicine, University College London, NIHR University College London Hospitals Biomedical Research Centre, London, UK
| | - Bronagh Blackwood
- Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, UK
| | - Lieuwe D J Bos
- Intensive Care, Amsterdam UMC, Location AMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Laurent Brochard
- Keenan Research Center, Li Ka Shing Knowledge Institute, Unity Health Toronto, Toronto, Canada
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada
| | - Daniel Brodie
- Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Karen E A Burns
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada
- Department of Medicine, Division of Critical Care, Unity Health Toronto - Saint Michael's Hospital, Toronto, Canada
- Li Ka Shing Knowledge Institute, St Michael's Hospital, Toronto, Canada
- Department of Health Research Methods, Evidence and Impact, McMaster University, Hamilton, Canada
| | - Alain Combes
- Sorbonne Université, INSERM, UMRS_1166-ICAN, Institute of Cardiometabolism and Nutrition, F-75013, Paris, France
- Service de Médecine Intensive-Réanimation, Institut de Cardiologie, APHP Sorbonne Université Hôpital Pitié-Salpêtrière, F-75013, Paris, France
| | - Sonia D'Arrigo
- Department of Anesthesiology Intensive Care and Emergency Medicine, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | - Daniel De Backer
- Department of Intensive Care, CHIREC Hospitals, Université Libre de Bruxelles, Brussels, Belgium
| | - Alexandre Demoule
- Sorbonne Université, INSERM, UMRS1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Paris, France
- AP-HP, Groupe Hospitalier Universitaire APHP-Sorbonne Université, site Pitié-Salpêtrière, Service de Médecine Intensive - Réanimation (Département R3S), Paris, France
| | - Sharon Einav
- Shaare Zedek Medical Center and Hebrew University Faculty of Medicine, Jerusalem, Israel
| | - Eddy Fan
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada
| | - Niall D Ferguson
- Department of Medicine, Division of Respirology and Critical Care, Toronto General Hospital Research Institute, University Health Network, Toronto, Canada
- Departments of Medicine and Physiology, Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Canada
| | - Jean-Pierre Frat
- CHU De Poitiers, Médecine Intensive Réanimation, Poitiers, France
- INSERM, CIC-1402, IS-ALIVE, Université de Poitiers, Faculté de Médecine et de Pharmacie, Poitiers, France
| | - Luciano Gattinoni
- Department of Anesthesiology, University Medical Center Göttingen, Göttingen, Germany
| | - Claude Guérin
- University of Lyon, Lyon, France
- Institut Mondor de Recherches Biomédicales, INSERM 955 CNRS 7200, Créteil, France
| | - Margaret S Herridge
- Critical Care and Respiratory Medicine, University Health Network, Toronto General Research Institute, Institute of Medical Sciences, Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada
| | - Carol Hodgson
- The Australian and New Zealand Intensive Care Research Center, School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia
- Department of Intensive Care, Alfred Health, Melbourne, Australia
| | - Catherine L Hough
- Division of Pulmonary, Allergy and Critical Care Medicine, Oregon Health and Science University, Portland, OR, USA
| | - Samir Jaber
- Anesthesia and Critical Care Department (DAR-B), Saint Eloi Teaching Hospital, University of Montpellier, Research Unit: PhyMedExp, INSERM U-1046, CNRS, 34295, Montpellier, France
| | - Nicole P Juffermans
- Laboratory of Translational Intensive Care, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Christian Karagiannidis
- Department of Pneumology and Critical Care Medicine, Cologne-Merheim Hospital, ARDS and ECMO Centre, Kliniken Der Stadt Köln gGmbH, Witten/Herdecke University Hospital, Cologne, Germany
| | - Jozef Kesecioglu
- Department of Intensive Care Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Arthur Kwizera
- Makerere University College of Health Sciences, School of Medicine, Department of Anesthesia and Intensive Care, Kampala, Uganda
| | - John G Laffey
- Anesthesia and Intensive Care Medicine, School of Medicine, College of Medicine Nursing and Health Sciences, University of Galway, Galway, Ireland
- Anesthesia and Intensive Care Medicine, Galway University Hospitals, Saolta University Hospitals Groups, Galway, Ireland
| | - Jordi Mancebo
- Intensive Care Department, Hospital Universitari de La Santa Creu I Sant Pau, Barcelona, Spain
| | - Michael A Matthay
- Departments of Medicine and Anesthesia, Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA, USA
| | - Daniel F McAuley
- Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, UK
- Regional Intensive Care Unit, Royal Victoria Hospital, Belfast Health and Social Care Trust, Belfast, UK
| | - Alain Mercat
- Département de Médecine Intensive Réanimation, CHU d'Angers, Université d'Angers, Angers, France
| | - Nuala J Meyer
- University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
| | - Marc Moss
- Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado, School of Medicine, Aurora, CO, USA
| | - Laveena Munshi
- Interdepartmental Division of Critical Care Medicine, Sinai Health System, University of Toronto, Toronto, Canada
| | - Sheila N Myatra
- Department of Anesthesiology, Critical Care and Pain, Tata Memorial Hospital, Homi Bhabha National Institute, Mumbai, India
| | - Michelle Ng Gong
- Division of Pulmonary and Critical Care Medicine, Montefiore Medical Center, Bronx, New York, NY, USA
- Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York, NY, USA
| | - Laurent Papazian
- Bastia General Hospital Intensive Care Unit, Bastia, France
- Aix-Marseille University, Faculté de Médecine, Marseille, France
| | - Bhakti K Patel
- Section of Pulmonary and Critical Care, Department of Medicine, University of Chicago, Chicago, IL, USA
| | - Mariangela Pellegrini
- Anesthesia and Intensive Care Medicine, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden
| | - Anders Perner
- Department of Intensive Care, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Antonio Pesenti
- Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
- Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Lise Piquilloud
- Adult Intensive Care Unit, University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Haibo Qiu
- Jiangsu Provincial Key Laboratory of Critical Care Medicine, Department of Critical Care Medicine, Zhongda Hospital, Southeast University, Nanjing, 210009, China
| | - Marco V Ranieri
- Alma Mater Studiorum - Università di Bologna, Bologna, Italy
- Anesthesia and Intensive Care Medicine, IRCCS Policlinico di Sant'Orsola, Bologna, Italy
| | - Elisabeth Riviello
- Division of Pulmonary, Critical Care and Sleep Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Arthur S Slutsky
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada
- Li Ka Shing Knowledge Institute, St Michael's Hospital, Toronto, Canada
| | - Renee D Stapleton
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Vermont Larner College of Medicine, Burlington, VT, USA
| | - Charlotte Summers
- Department of Medicine, University of Cambridge Medical School, Cambridge, UK
| | - Taylor B Thompson
- Division of Pulmonary and Critical Care Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Carmen S Valente Barbas
- University of São Paulo Medical School, São Paulo, Brazil
- Hospital Israelita Albert Einstein, São Paulo, Brazil
| | - Jesús Villar
- Li Ka Shing Knowledge Institute, St Michael's Hospital, Toronto, Canada
- CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain
- Research Unit, Hospital Universitario Dr. Negrin, Las Palmas de Gran Canaria, Spain
| | - Lorraine B Ware
- Departments of Medicine and Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Björn Weiss
- Department of Anesthesiology and Intensive Care Medicine (CCM CVK), Charitè - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt Universität zu Berlin, Berlin, Germany
| | - Fernando G Zampieri
- Academic Research Organization, Albert Einstein Hospital, São Paulo, Brazil
- Department of Critical Care Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
| | - Elie Azoulay
- Médecine Intensive et Réanimation, APHP, Hôpital Saint-Louis, Paris Cité University, Paris, France
| | - Maurizio Cecconi
- Department of Biomedical Sciences, Humanitas University, Pieve Emanuele, Milan, Italy
- Department of Anesthesia and Intensive Care Medicine, IRCCS Humanitas Research Hospital, Rozzano, Milan, Italy
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Zhou C, Chase JG. Low-cost structured light imaging of regional volume changes for use in assessing mechanical ventilation. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2022; 226:107176. [PMID: 36228494 DOI: 10.1016/j.cmpb.2022.107176] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 09/21/2022] [Accepted: 10/04/2022] [Indexed: 06/16/2023]
Abstract
BACKGROUND Optimal setting of mechanical ventilators is critical for improving outcomes. Accurate, predictive lung mechanics models are effective in optimizing MV settings, but only at a global level as they cannot estimate regional lung volume ventilation to assess the potential of local distension or under-ventilation. This study presents a low-cost structured light system for non-contact high resolution chest motion measurement to estimate regional lung volume changes. METHODS The system consists of a structured light projector and two cameras. A new pattern is designed to extract motion from sub-regions of the chest surface, and an efficient feature is proposed to provide a fast and accurate correspondence matching between two views. Reconstruction of 3D surface points is based on the matched points and stereo method. Asymmetric distribution of tidal volume into left and right lungs is estimated based on reconstructed regional chest expansion. A proof-of-concept experiment using a dummy model and two test lungs connected to a ventilator to provide differential chest expansion is conducted under tidal volumes of 400 ml, 500 ml and 600 ml, with results compared to the widely-used SURF and ORB methods. RESULTS Compared to the SURF and ORB methods, the proposed method is more computationally efficient with ∼40% less computational time cost, and higher accuracy for dense point correspondence. Finally, the proposed method estimated the region lung volumes with the maximum error of 8 ml under 600 ml tidal volume, indicating a good accuracy. CONCLUSIONS Surface reconstruction results in a proof-of-concept experiment with differential chest expansion show good performance for the proposed pattern and method in extracting the key information for regional chest expansion. The proposed method is generalizable, with potential for use in other applications.
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Affiliation(s)
- Cong Zhou
- School of Civil Aviation, Northwestern Polytechnical University, China; Department of Mechanical Engineering, Centre for Bio-Engineering, University of Canterbury, Christchurch, New Zealand
| | - J Geoffrey Chase
- Department of Mechanical Engineering, Centre for Bio-Engineering, University of Canterbury, Christchurch, New Zealand.
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Frerichs I, Lasarow L, Strodthoff C, Vogt B, Zhao Z, Weiler N. Spatial Ventilation Inhomogeneity Determined by Electrical Impedance Tomography in Patients With Chronic Obstructive Lung Disease. Front Physiol 2021; 12:762791. [PMID: 34966289 PMCID: PMC8712108 DOI: 10.3389/fphys.2021.762791] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Accepted: 11/16/2021] [Indexed: 11/13/2022] Open
Abstract
The aim of this study was to examine whether electrical impedance tomography (EIT) could determine the presence of ventilation inhomogeneity in patients with chronic obstructive lung disease (COPD) from measurements carried out not only during conventional forced full expiration maneuvers but also from forced inspiration maneuvers and quiet tidal breathing and whether the inhomogeneity levels were comparable among the phases and higher than in healthy subjects. EIT data were acquired in 52 patients with exacerbated COPD (11 women, 41 men, 68 ± 11 years) and 14 healthy subjects (6 women, 8 men, 38 ± 8 years). Regional lung function parameters of forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), forced inspiratory vital capacity (FIVC), forced inspiratory volume in 1 s (FIV1), and tidal volume (V T ) were determined in 912 image pixels. The spatial inhomogeneity of the pixel parameters was characterized by the coefficients of variation (CV) and the global inhomogeneity (GI) index. CV and GI values of pixel FVC, FEV1, FIVC, FIV1, and VT were significantly higher in patients than in healthy subjects (p ≤ 0.0001). The ventilation distribution was affected by the analyzed lung function parameter in patients (CV: p = 0.0024, GI: p = 0.006) but not in healthy subjects. Receiver operating characteristic curves showed that CV and GI discriminated patients from healthy subjects with an area under the curve (AUC) of 0.835 and 0.852 (FVC), 0.845 and 0.867 (FEV1), 0.903 and 0.903 (FIVC), 0.891 and 0.882 (FIV1), and 0.821 and 0.843 (VT), respectively. These findings confirm the ability of EIT to identify increased ventilation inhomogeneity in patients with COPD.
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Affiliation(s)
- Inéz Frerichs
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Kiel, Germany
| | - Livia Lasarow
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Kiel, Germany
| | - Claas Strodthoff
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Kiel, Germany
| | - Barbara Vogt
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Kiel, Germany
| | - Zhanqi Zhao
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China.,Institute of Technical Medicine, Furtwangen University, Villingen-Schwenningen, Germany
| | - Norbert Weiler
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Kiel, Germany
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Mistry S, Das A, Hardman JG, Bates DG, Scott TE. Pre-hospital continuous positive airway pressure after blast lung injury and hypovolaemic shock: a modelling study. Br J Anaesth 2021; 128:e151-e157. [PMID: 34863511 DOI: 10.1016/j.bja.2021.10.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 10/14/2021] [Accepted: 10/14/2021] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND In non-traumatic respiratory failure, pre-hospital application of CPAP reduces the need for intubation. Primary blast lung injury (PBLI) accompanied by haemorrhagic shock is common after mass casualty incidents. We hypothesised that pre-hospital CPAP is also beneficial after PBLI accompanied by haemorrhagic shock. METHODS We performed a computer-based simulation of the cardiopulmonary response to PBLI followed by haemorrhage, calibrated from published controlled porcine experiments exploring blast injury and haemorrhagic shock. The effect of different CPAP levels was simulated in three in silico patients who had sustained mild, moderate, or severe PBLI (10%, 25%, 50% contusion of the total lung) plus haemorrhagic shock. The primary outcome was arterial partial pressure of oxygen (Pao2) at the end of each simulation. RESULTS In mild blast lung injury, 5 cm H2O ambient-air CPAP increased Pao2 from 10.6 to 12.6 kPa. Higher CPAP did not further improve Pao2. In moderate blast lung injury, 10 cm H2O CPAP produced a larger increase in Pao2 (from 8.5 to 11.1 kPa), but 15 cm H2O CPAP produced no further benefit. In severe blast lung injury, 5 cm H2O CPAP inceased Pao2 from 4.06 to 8.39 kPa. Further increasing CPAP to 10-15 cm H2O reduced Pao2 (7.99 and 7.90 kPa, respectively) as a result of haemodynamic impairment resulting from increased intrathoracic pressures. CONCLUSIONS Our modelling study suggests that ambient air 5 cm H2O CPAP may benefit casualties suffering from blast lung injury, even with severe haemorrhagic shock. However, higher CPAP levels beyond 10 cm H2O after severe lung injury reduced oxygen delivery as a result of haemodynamic impairment.
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Affiliation(s)
- Sonal Mistry
- School of Engineering, University of Warwick, Coventry, UK
| | - Anup Das
- School of Engineering, University of Warwick, Coventry, UK
| | - Jonathan G Hardman
- Anaesthesia and Critical Care, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, Nottingham, UK
| | - Declan G Bates
- School of Engineering, University of Warwick, Coventry, UK.
| | - Timothy E Scott
- Academic Department of Military Anaesthesia and Critical Care, Royal Centre for Defence Medicine, ICT Centre, Birmingham, UK.
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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.
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Synchronized Inflations Generate Greater Gravity-Dependent Lung Ventilation in Neonates. J Pediatr 2021; 228:24-30.e10. [PMID: 32827530 DOI: 10.1016/j.jpeds.2020.08.043] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 08/05/2020] [Accepted: 08/14/2020] [Indexed: 12/13/2022]
Abstract
OBJECTIVE To describe the regional distribution patterns of tidal ventilation within the lung during mechanical ventilation that is synchronous or asynchronous with an infant's own breathing effort. STUDY DESIGN Intubated infants receiving synchronized mechanical ventilation at The Royal Children's Hospital neonatal intensive care unit were studied. During four 10-minute periods of routine care, regional distribution of tidal volume (VT; electrical impedance tomography), delivered pressure, and airway flow (Florian Respiratory Monitor) were measured for every inflation. Post hoc, each inflation was then classified as synchronous or asynchronous from video data of the ventilator screen, and the distribution of absolute VT and delivered ventilation characteristics determined. RESULTS In total, 2749 inflations (2462 synchronous) were analyzed in 19 infants; mean (SD) age 28 (30) days, gestational age 35 (5) weeks. Synchronous inflations were associated with a shorter respiratory cycle (P = .004) and more homogenous VT (center of ventilation) along the right (0%) to left (100%) lung plane; 45.3 (8.6)% vs 48.8 (9.4)% (uniform ventilation 46%). The gravity-dependent center of ventilation was a mean (95% CI) 2.1 (-0.5, 4.6)% toward the dependent lung during synchronous inflations. Tidal ventilation relative to anatomical lung size was more homogenous during synchronized inflations in the dependent lung. CONCLUSIONS Synchronous mechanical ventilator lung inflations generate more gravity-dependent lung ventilation and more uniform right-to-left ventilation than asynchronous inflations.
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Scaramuzzo G, Spinelli E, Spadaro S, Santini A, Tortolani D, Dalla Corte F, Pesenti A, Volta CA, Grasselli G, Mauri T. Gravitational distribution of regional opening and closing pressures, hysteresis and atelectrauma in ARDS evaluated by electrical impedance tomography. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2020; 24:622. [PMID: 33092607 PMCID: PMC7579854 DOI: 10.1186/s13054-020-03335-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 10/06/2020] [Indexed: 01/26/2023]
Abstract
Background The physiological behavior of lungs affected by the acute respiratory distress syndrome (ARDS) differs between inspiration and expiration and presents heterogeneous gravity-dependent distribution. This phenomenon, highlighted by the different distribution of opening/closing pressure and by the hysteresis of the pressure–volume curve, can be studied by CT scan, but the technique expose the patient to radiations, cannot track changes during time and is not feasible at the bedside. Electrical impedance tomography (EIT) could help in assessing at the bedside regional inspiratory and expiratory mechanical properties. We evaluated regional opening/closing pressures, hysteresis and atelectrauma during inspiratory and expiratory low-flow pressure–volume curves in ARDS using electrical impedance tomography. Methods Pixel-level inspiratory and expiratory PV curves (PVpixel) between 5 and 40 cmH2O were constructed integrating EIT images and airway opening pressure signal from 8 ARDS patients. The lower inflection point in the inspiratory and expiratory PVpixel were used to find opening (OPpixel) and closing (CPpixel) pressures. A novel atelectrauma index (AtI) was calculated as the percentage of pixels opening during the inspiratory and closing during the expiratory PV curves. The maximal hysteresis (HysMax) was calculated as the maximal difference between normalized expiratory and inspiratory PV curves. Analyses were conducted in the global, dependent and non-dependent lung regions. Results Gaussian distribution was confirmed for both global OPpixel (r2 = 0.90) and global CPpixel (r2 = 0.94). The two distributions were significantly different with higher values for OPpixel (p < 0.0001). Regional OPpixel and CPpixel distributions were Gaussian, and in the dependent lung regions, both were significantly higher than in the non-dependent ones (p < 0.001). Both AtI and the HysMax were significantly higher in the dependent regions compared to the non-dependent ones (p < 0.05 for both). Conclusions Gravity impacts the regional distribution of opening and closing pressure, hysteresis and atelectrauma, with higher values in the dorsal lung. Regional differences between inspiratory and expiratory lung physiology are detectable at the bedside using EIT and could allow in-depth characterization of ARDS phenotypes and guide personalized ventilation settings. Graphic abstract ![]()
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Affiliation(s)
- Gaetano Scaramuzzo
- Department of Morphology, Surgery and Experimental Medicine, Intensive Care Unit, Azienda Ospedaliera Universitaria Sant'Anna Hospital, Ferrara, Italy
| | - Elena Spinelli
- Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Via F. Sforza 35, 20122, Milan, Italy
| | - Savino Spadaro
- Department of Morphology, Surgery and Experimental Medicine, Intensive Care Unit, Azienda Ospedaliera Universitaria Sant'Anna Hospital, Ferrara, Italy
| | - Alessandro Santini
- Department of Anaesthesia and Intensive Care Medicine, Humanitas Clinical and Research Centre-IRCCS, Rozzano, Milan, Italy
| | - Donatella Tortolani
- Department of Morphology, Surgery and Experimental Medicine, Intensive Care Unit, Azienda Ospedaliera Universitaria Sant'Anna Hospital, Ferrara, Italy
| | - Francesca Dalla Corte
- Department of Morphology, Surgery and Experimental Medicine, Intensive Care Unit, Azienda Ospedaliera Universitaria Sant'Anna Hospital, Ferrara, Italy
| | - Antonio Pesenti
- Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Via F. Sforza 35, 20122, Milan, Italy.,Department of Pathophysiology and Transplant, University of Milan, Milan, Italy
| | - Carlo Alberto Volta
- Department of Morphology, Surgery and Experimental Medicine, Intensive Care Unit, Azienda Ospedaliera Universitaria Sant'Anna Hospital, Ferrara, Italy
| | - Giacomo Grasselli
- Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Via F. Sforza 35, 20122, Milan, Italy.,Department of Pathophysiology and Transplant, University of Milan, Milan, Italy
| | - Tommaso Mauri
- Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Via F. Sforza 35, 20122, Milan, Italy. .,Department of Pathophysiology and Transplant, University of Milan, Milan, Italy.
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9
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Sang L, Zhao Z, Yun PJ, Frerichs I, Möller K, Fu F, Liu X, Zhong N, Li Y. Qualitative and quantitative assessment of pendelluft: a simple method based on electrical impedance tomography. ANNALS OF TRANSLATIONAL MEDICINE 2020; 8:1216. [PMID: 33178748 PMCID: PMC7607126 DOI: 10.21037/atm-20-4182] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Background Pendelluft, defined as asynchronous alveolar ventilation, is caused by different regional time constants or dynamic pleural pressure variations. The aim of the present study was to propose a simple method to evaluate pendelluft based on electrical impedance tomography (EIT). The efficacy of this method was demonstrated in well-known pendelluft scenarios in 6 patients. Methods Two patients with flail chest after accidents, two patients with acute respiratory distress syndrome (ARDS) and two patients with acutely exacerbated obstructive lung disease were prospectively included. EIT measurements were performed before and after surgery (in patients with flail chest, who had video-assisted thoracoscopic surgery with ribs fixation), or at two different levels of positive end-expiratory pressure (PEEP; ARDS patients), or two different time points (obstructive lung disease). Pendelluft was assessed by regional phase shift (defined as time difference between global and regional impedance-time curves) and amplitude differences (defined as the impedance difference between sum of all regional tidal variation and the global tidal variation). Results In patients with flail chest, pendelluft diminished several days after surgery (pendelluft amplitude normalized to tidal impedance variation reduced from 88% to 2% in one patient, 12% to 2% in the other). Increased PEEP reduced the amplitude of pendelluft (from 3% to 0% in one patient, 20% to 2% in the other) but not necessarily the phase shifts (average time differences were <0.1 second for both patients for both ins- and expiration) in ARDS patients. Pendelluft assessment in obstructive lung diseases reflected the change in airway resistance (from 5% to 1% in one patient after broncholytic medication administration, as airway resistance fell from 15 to 11 cmH2O/L/s; from 9% to 35% in the other patient with acute exacerbation, the corresponding airway resistance increased from 15 to 22 cmH2O/L/s). Conclusions The proposed EIT-based method can be used to evaluate the degree of pendelluft in dimension of phase shift and amplitude difference.
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Affiliation(s)
- Ling Sang
- Department of Critical Care Medicine, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou Medical University, State Key Lab of Respiratory Diseases, Guangzhou Institute of Respiratory Health, Guangzhou, China
| | - Zhanqi Zhao
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China.,Institute of Technical Medicine, Furtwangen University, Villingen-Schwenningen, Germany
| | - Po-Jen Yun
- Division of Thoracic Surgery, Department of Surgery, Tri-Service General Hospital, Taipei
| | - Inéz Frerichs
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center of Schleswig-Holstein Campus Kiel, Kiel, Germany
| | - Knut Möller
- Institute of Technical Medicine, Furtwangen University, Villingen-Schwenningen, Germany
| | - Feng Fu
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - Xiaoqing Liu
- Department of Critical Care Medicine, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou Medical University, State Key Lab of Respiratory Diseases, Guangzhou Institute of Respiratory Health, Guangzhou, China
| | - Nanshan Zhong
- Department of Critical Care Medicine, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou Medical University, State Key Lab of Respiratory Diseases, Guangzhou Institute of Respiratory Health, Guangzhou, China
| | - Yimin Li
- Department of Critical Care Medicine, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou Medical University, State Key Lab of Respiratory Diseases, Guangzhou Institute of Respiratory Health, Guangzhou, China
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10
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Muders T, Hentze B, Simon P, Girrbach F, Doebler MRG, Leonhardt S, Wrigge H, Putensen C. A Modified Method to Assess Tidal Recruitment by Electrical Impedance Tomography. J Clin Med 2019; 8:E1161. [PMID: 31382559 PMCID: PMC6723902 DOI: 10.3390/jcm8081161] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 07/29/2019] [Accepted: 08/01/2019] [Indexed: 12/11/2022] Open
Abstract
Avoiding tidal recruitment and collapse during mechanical ventilation should reduce the risk of lung injury. Electrical impedance tomography (EIT) enables detection of tidal recruitment by measuring regional ventilation delay inhomogeneity (RVDI) during a slow inflation breath with a tidal volume (VT) of 12 mL/kg body weight (BW). Clinical applicability might be limited by such high VTs resulting in high end-inspiratory pressures (PEI) during positive end-expiratory pressure (PEEP) titration. We hypothesized that RVDI can be obtained with acceptable accuracy from reduced slow inflation VTs. In seven ventilated pigs with experimental lung injury, tidal recruitment was quantified by computed tomography at PEEP levels changed stepwise between 0 and 25 cmH2O. RVDI was measured by EIT during slow inflation VTs of 12, 9, 7.5, and 6 mL/kg BW. Linear correlation of tidal recruitment and RVDI was excellent for VTs of 12 (R2 = 0.83, p < 0.001) and 9 mL/kg BW (R2 = 0.83, p < 0.001) but decreased for VTs of 7.5 (R2 = 0.76, p < 0.001) and 6 mL/kg BW (R2 = 0.71, p < 0.001). With any reduction in slow inflation VT, PEI decreased at all PEEP levels. Receiver-Operator-Characteristic curve analyses revealed that RVDI-thresholds to predict distinct amounts of tidal recruitment differ when obtained from different slow inflation VTs. In conclusion, tidal recruitment can sufficiently be monitored by EIT-based RVDI-calculation with a slow inflation of 9 mL/kg BW.
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Affiliation(s)
- Thomas Muders
- Department of Anesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn 53127, Germany.
| | - Benjamin Hentze
- Department of Anesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn 53127, Germany
- Chair for Medical Information Technology, RWTH Aachen University, Aachen 52074, Germany
| | - Philipp Simon
- Department of Anesthesiology and Intensive Care Medicine, University of Leipzig, Leipzig 04103, Germany
| | - Felix Girrbach
- Department of Anesthesiology and Intensive Care Medicine, University of Leipzig, Leipzig 04103, Germany
| | - Michael R G Doebler
- Department of Anesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn 53127, Germany
| | - Steffen Leonhardt
- Chair for Medical Information Technology, RWTH Aachen University, Aachen 52074, Germany
| | - Hermann Wrigge
- Department of Anesthesiology, Intensive Care and Emergency Medicine, Pain Therapy, Bergmannstrost Hospital Halle, Halle 06112, Germany
| | - Christian Putensen
- Department of Anesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn 53127, Germany
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11
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Vogt B, Deuß K, Hennig V, Zhao Z, Lautenschläger I, Weiler N, Frerichs I. Regional lung function in nonsmokers and asymptomatic current and former smokers. ERJ Open Res 2019; 5:00240-2018. [PMID: 31321224 PMCID: PMC6628636 DOI: 10.1183/23120541.00240-2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 05/01/2019] [Indexed: 11/05/2022] Open
Abstract
Electrical impedance tomography (EIT) is able to detect rapid lung volume changes during breathing. The aim of our observational study was to characterise the heterogeneity of regional ventilation distribution in lung-healthy adults by EIT and to detect the possible impact of tobacco consumption. A total of 219 nonsmokers, asymptomatic ex-smokers and current smokers were examined during forced full expiration using EIT. Forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and FEV1/FVC were determined in 836 EIT image pixels for the analysis of spatial and temporal ventilation distribution. Coefficients of variation (CVs) of these pixel values were calculated. Histograms and medians of FEV1/FVCEIT and times required to exhale 50%, 75%, 90% of FVCEIT (t50, t75 and t90) were generated. CV of FEV1/FVCEIT distinguished among all groups (mean±sd: nonsmokers 0.43±0.05, ex-smokers 0.52±0.09, smokers 0.62±0.16). Histograms of FEV1/FVCEIT differentiated between nonsmokers and the other groups (p<0.0001). Medians of t50, t75 and t90 showed the lowest values in nonsmokers. Median t90 separated all groups (median (interquartile range): nonsmokers 0.82 (0.67-1.15), ex-smokers 1.41 (1.03-2.21), smokers 1.91 (1.33-3.53)). EIT detects regional ventilation heterogeneity during forced expiration in healthy nonsmokers and its increase in asymptomatic former and current smokers. Therefore, EIT-derived reference values should only be collected from nonsmoking lung-healthy adults.
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Affiliation(s)
- Barbara Vogt
- Dept of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Kathinka Deuß
- Dept of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Victoria Hennig
- Dept of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Zhanqi Zhao
- Dept of Biomedical Engineering, Fourth Military Medical University, Xi'an, China.,Dept of Biomedical Engineering, Furtwangen University, Villingen-Schwenningen, Germany
| | - Ingmar Lautenschläger
- Dept of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Norbert Weiler
- Dept of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Inéz Frerichs
- Dept of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
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12
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Becher T, van der Staay M, Schädler D, Frerichs I, Weiler N. Calculation of mechanical power for pressure-controlled ventilation. Intensive Care Med 2019; 45:1321-1323. [PMID: 31101961 DOI: 10.1007/s00134-019-05636-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/02/2019] [Indexed: 11/24/2022]
Affiliation(s)
- Tobias Becher
- Department of Anesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3, Haus 12, 24105, Kiel, Germany.
| | | | - D Schädler
- Department of Anesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3, Haus 12, 24105, Kiel, Germany
| | - I Frerichs
- Department of Anesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3, Haus 12, 24105, Kiel, Germany
| | - N Weiler
- Department of Anesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3, Haus 12, 24105, Kiel, Germany
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13
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Victor M, Melo J, Roldán R, Nakamura M, Tucci M, Costa E, Amato M, Yoneyama T, Tanaka H. Modelling approach to obtain regional respiratory mechanics using electrical impedance tomography and volume-dependent elastance model. Physiol Meas 2019; 40:045001. [PMID: 30921784 DOI: 10.1088/1361-6579/ab144a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE This paper presents a method for breath-by-breath estimation of regional respiratory mechanics without the need for special manoeuvres (such as inspiratory pause or low-flow inflation) using electrical impedance tomography (EIT) associated with pressure/airflow waveforms. APPROACH We developed a method to estimate regional parameters using the regional impedance fraction, by multiplying it by global flow and volume waveforms. A volume-dependent elastance model was used to obtain compliance, resistance, volume-independent (E 1), and volume-dependent (E 2) components. Three swine under invasive mechanical ventilation were used to assess internal consistency and illustrate potential applications of our method. One animal (case 1) was ventilated with a broad range of tidal volumes to compare the consistency between regional and global resistances and compliances. Two other animals (cases 2 and 3) had respiratory compliance decreased, respectively, by overdistension and collapse as quantified by x-ray computed tomography. MAIN RESULTS In case 1, derived global estimates obtained from the independent regional estimates were strongly associated with direct measurements of global mechanics (correlation coefficients of 0.9976 and 0.9981 for compliances and resistances, respectively), suggesting consistency of our modelling. In cases 2 and 3, the development of lung overdistension and collapse over time was captured by regional estimates. CONCLUSIONS Using EIT and pressure/airflow waveforms, regional respiratory parameters can be obtained cycle-by-cycle, refining lung function monitoring. SIGNIFICANCE The method allows real-time monitoring of regional parameters and their trends over time, which might be helpful to differentiate deterioration in lung compliance due to overdistension or collapse.
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Affiliation(s)
- M Victor
- Electronics Engineering Department, Aeronautics Institute of Technology, São Paulo, Brazil
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14
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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.
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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
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15
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Karagiannidis C, Waldmann AD, Róka PL, Schreiber T, Strassmann S, Windisch W, Böhm SH. Regional expiratory time constants in severe respiratory failure estimated by electrical impedance tomography: a feasibility study. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2018; 22:221. [PMID: 30236123 PMCID: PMC6148957 DOI: 10.1186/s13054-018-2137-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 07/27/2018] [Indexed: 01/17/2023]
Abstract
Background Electrical impedance tomography (EIT) has been used to guide mechanical ventilation in ICU patients with lung collapse. Its use in patients with obstructive pulmonary diseases has been rare since obstructions could not be monitored on a regional level at the bedside. The current study therefore determines breath-by-breath regional expiratory time constants in intubated patients with chronic obstructive pulmonary disease (COPD) and acute respiratory distress syndrome (ARDS). Methods Expiratory time constants calculated from the global impedance EIT signal were compared to the pneumatic volume signals measured with an electronic pneumotachograph. EIT-derived expiratory time constants were additionally determined on a regional and pixelwise level. However, regional EIT signals on a single pixel level could in principle not be compared with similar pneumatic changes since these measurements cannot be obtained in patients. For this study, EIT measurements were conducted in 14 intubated patients (mean Simplified Acute Physiology Score II (SAPS II) 35 ± 10, mean time on invasive mechanical ventilation 36 ± 26 days) under four different positive end-expiratory pressure (PEEP) levels ranging from 10 to 17 cmH2O. Only patients with moderate-severe ARDS or COPD exacerbation were included into the study, preferentally within the first days following intubation. Results Spearman’s correlation coefficient for comparison between EIT-derived time constants and those from flow/volume curves was between 0.78 for tau (τ) calculated from the global impedance signal up to 0.83 for the mean of all pixelwise calculated regional impedance changes over the entire PEEP range. Furthermore, Bland-Altman analysis revealed a corresponding bias of 0.02 and 0.14 s within the limits of agreement ranging from − 0.50 to 0.65 s for the aforementioned calculation methods. In addition, exemplarily in patients with moderate-severe ARDS or COPD exacerbation, different PEEP levels were shown to have an influence on the distribution pattern of regional time constants. Conclusions EIT-based determination of breath-by-breath regional expiratory time constants is technically feasible, reliable and valid in invasively ventilated patients with severe respiratory failure and provides a promising tool to individually adjust mechanical ventilation in response to the patterns of regional airflow obstruction. Trial registration German Trial Register DRKS 00011650, registered 01/31/17. Electronic supplementary material The online version of this article (10.1186/s13054-018-2137-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Christian Karagiannidis
- Department of Pneumology and Critical Care Medicine, Cologne-Merheim Hospital, Kliniken der Stadt Köln gGmbH, Witten/Herdecke University Hospital, Ostmerheimer Strasse 200, D-51109, Cologne, Germany.
| | - Andreas D Waldmann
- Department of Pneumology and Critical Care Medicine, Cologne-Merheim Hospital, Kliniken der Stadt Köln gGmbH, Witten/Herdecke University Hospital, Ostmerheimer Strasse 200, D-51109, Cologne, Germany.,Swisstom AG, Schulstrasse 1, 7302, Landquart, Switzerland
| | - Péter L Róka
- Budapest University of Technology and Economics, Budapest, Hungary
| | - Tina Schreiber
- Department of Pneumology and Critical Care Medicine, Cologne-Merheim Hospital, Kliniken der Stadt Köln gGmbH, Witten/Herdecke University Hospital, Ostmerheimer Strasse 200, D-51109, Cologne, Germany
| | - Stephan Strassmann
- Department of Pneumology and Critical Care Medicine, Cologne-Merheim Hospital, Kliniken der Stadt Köln gGmbH, Witten/Herdecke University Hospital, Ostmerheimer Strasse 200, D-51109, Cologne, Germany
| | - Wolfram Windisch
- Department of Pneumology and Critical Care Medicine, Cologne-Merheim Hospital, Kliniken der Stadt Köln gGmbH, Witten/Herdecke University Hospital, Ostmerheimer Strasse 200, D-51109, Cologne, Germany
| | - Stephan H Böhm
- Klinik und Poliklinik für Anästhesiologie und Intensivtherapie, Universitätsmedizin Rostock, Schillingallee 35, D-18057, Rostock, Germany
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Affiliation(s)
- Mojdeh Monjezi
- Chronic Respiratory Diseases Research Center, National Research Institute of Tuberculosis and Lung Diseases, Shahid Beheshti University of Medical Sciences , Tehran , Iran
| | - Hamidreza Jamaati
- Chronic Respiratory Diseases Research Center, National Research Institute of Tuberculosis and Lung Diseases, Shahid Beheshti University of Medical Sciences , Tehran , Iran
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18
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Becher T, Rostalski P, Kott M, Adler A, Schädler D, Weiler N, Frerichs I. Global and regional assessment of sustained inflation pressure-volume curves in patients with acute respiratory distress syndrome. Physiol Meas 2017; 38:1132-1144. [PMID: 28339394 DOI: 10.1088/1361-6579/aa6923] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
OBJECTIVE Static or quasi-static pressure-volume (P-V ) curves can be used to determine the lung mechanical properties of patients suffering from acute respiratory distress syndrome (ARDS). According to the traditional interpretation, lung recruitment occurs mainly below the lower point of maximum curvature (LPMC) of the inflation P-V curve. Although some studies have questioned this assumption, setting of positive end-expiratory pressure 2 cmH2O above the LPMC was part of a 'lung-protective' ventilation strategy successfully applied in several clinical trials. The aim of our study was to quantify the amount of unrecruited lung at different clinically relevant points of the P-V curve. APPROACH P-V curves and electrical impedance tomography (EIT) data from 30 ARDS patients were analysed. We determined the regional opening pressures for every EIT image pixel and fitted the global P-V curves to five sigmoid model equations to determine the LPMC, inflection point (IP) and upper point of maximal curvature (UPMC). Points of maximal curvature and IP were compared between the models by one-way analysis of variance (ANOVA). The percentages of lung pixels remaining closed ('unrecruited lung') at LPMC, IP and UPMC were calculated from the number of lung pixels exhibiting regional opening pressures higher than LPMC, IP and UPMC and were also compared by one-way ANOVA. MAIN RESULTS As results, we found a high variability of LPMC values among the models, a smaller variability of IP and UPMC values. We found a high percentage of unrecruited lung at LPMC, a small percentage of unrecruited lung at IP and no unrecruited lung at UPMC. SIGNIFICANCE Our results confirm the notion of ongoing lung recruitment at pressure levels above LPMC for all investigated model equations and highlight the importance of a regional assessment of lung recruitment in patients with ARDS.
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Affiliation(s)
- T Becher
- Department of Anaesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Campus Kiel, Kiel, Germany
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Frerichs I, Amato MBP, van Kaam AH, Tingay DG, Zhao Z, Grychtol B, Bodenstein M, Gagnon H, Böhm SH, Teschner E, Stenqvist O, Mauri T, Torsani V, Camporota L, Schibler A, Wolf GK, Gommers D, Leonhardt S, Adler A. Chest electrical impedance tomography examination, data analysis, terminology, clinical use and recommendations: consensus statement of the TRanslational EIT developmeNt stuDy group. Thorax 2016; 72:83-93. [PMID: 27596161 PMCID: PMC5329047 DOI: 10.1136/thoraxjnl-2016-208357] [Citation(s) in RCA: 490] [Impact Index Per Article: 61.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 07/12/2016] [Accepted: 07/16/2016] [Indexed: 11/04/2022]
Abstract
Electrical impedance tomography (EIT) has undergone 30 years of development. Functional chest examinations with this technology are considered clinically relevant, especially for monitoring regional lung ventilation in mechanically ventilated patients and for regional pulmonary function testing in patients with chronic lung diseases. As EIT becomes an established medical technology, it requires consensus examination, nomenclature, data analysis and interpretation schemes. Such consensus is needed to compare, understand and reproduce study findings from and among different research groups, to enable large clinical trials and, ultimately, routine clinical use. Recommendations of how EIT findings can be applied to generate diagnoses and impact clinical decision-making and therapy planning are required. This consensus paper was prepared by an international working group, collaborating on the clinical promotion of EIT called TRanslational EIT developmeNt stuDy group. It addresses the stated needs by providing (1) a new classification of core processes involved in chest EIT examinations and data analysis, (2) focus on clinical applications with structured reviews and outlooks (separately for adult and neonatal/paediatric patients), (3) a structured framework to categorise and understand the relationships among analysis approaches and their clinical roles, (4) consensus, unified terminology with clinical user-friendly definitions and explanations, (5) a review of all major work in thoracic EIT and (6) recommendations for future development (193 pages of online supplements systematically linked with the chief sections of the main document). We expect this information to be useful for clinicians and researchers working with EIT, as well as for industry producers of this technology.
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Affiliation(s)
- Inéz Frerichs
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Marcelo B P Amato
- Pulmonary Division, Heart Institute (InCor), Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Anton H van Kaam
- Department of Neonatology, Emma Children's Hospital, Academic Medical Center, Amsterdam, The Netherlands
| | - David G Tingay
- Neonatal Research, Murdoch Childrens Research Institute, Parkville, Victoria, Australia
| | - Zhanqi Zhao
- Institute of Technical Medicine, Furtwangen University, Villingen-Schwenningen, Germany
| | - Bartłomiej Grychtol
- Fraunhofer Project Group for Automation in Medicine and Biotechnology PAMB, Mannheim, Germany
| | - Marc Bodenstein
- Department of Anesthesiology, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany
| | - Hervé Gagnon
- Department of Systems and Computer Engineering, Carleton University, Ottawa, Ontario, Canada
| | | | | | - Ola Stenqvist
- Department of Anesthesiology and Intensive Care Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Tommaso Mauri
- Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Vinicius Torsani
- Pulmonary Division, Heart Institute (InCor), Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Luigi Camporota
- Department of Adult Critical Care, Guy's and St Thomas' NHS Foundation Trust, London, UK
| | - Andreas Schibler
- Paediatric Critical Care Research Group, Mater Research University of Queensland, South Brisbane, Australia
| | - Gerhard K Wolf
- Children's Hospital Traunstein, Ludwig Maximilian's University, Munich, Germany
| | - Diederik Gommers
- Department of Adult Intensive Care, Erasmus MC, Rotterdam, The Netherlands
| | - Steffen Leonhardt
- Philips Chair for Medical Information Technology, Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University, Aachen, Germany
| | - Andy Adler
- Department of Systems and Computer Engineering, Carleton University, Ottawa, Ontario, Canada
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Schullcke B, Krueger-Ziolek S, Gong B, Mueller-Lisse U, Moeller K. Compensation for large thorax excursions in EIT imaging. Physiol Meas 2016; 37:1605-23. [PMID: 27531053 DOI: 10.1088/0967-3334/37/9/1605] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Besides the application of EIT in the intensive care unit it has recently also been used in spontaneously breathing patients suffering from asthma bronchiole, cystic fibrosis (CF) or chronic obstructive pulmonary disease (COPD). In these cases large thorax excursions during deep inspiration, e.g. during lung function testing, lead to artifacts in the reconstructed images. In this paper we introduce a new approach to compensate for image artifacts resulting from excursion induced changes in boundary voltages. It is shown in a simulation study that boundary voltage change due to thorax excursion on a homogeneous model can be used to modify the measured voltages and thus reduce the impact of thorax excursion on the reconstructed images. The applicability of the method on human subjects is demonstrated utilizing a motion-tracking-system. The proposed technique leads to fewer artifacts in the reconstructed images and improves image quality without substantial increase in computational effort, making the approach suitable for real-time imaging of lung ventilation. This might help to establish EIT as a supplemental tool for lung function tests in spontaneously breathing patients to support clinicians in diagnosis and monitoring of disease progression.
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Affiliation(s)
- B Schullcke
- Institute of Technical Medicine, Furtwangen University, VS-Schwenningen, Germany. Department of Radiology, University of Munich, Munich, Germany
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Kobylianskii J, Murray A, Brace D, Goligher E, Fan E. Electrical impedance tomography in adult patients undergoing mechanical ventilation: A systematic review. J Crit Care 2016; 35:33-50. [PMID: 27481734 DOI: 10.1016/j.jcrc.2016.04.028] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 04/25/2016] [Accepted: 04/27/2016] [Indexed: 01/20/2023]
Abstract
PURPOSE The purpose of the study is to systematically review and summarize current literature concerning the validation and application of electrical impedance tomography (EIT) in mechanically ventilated adult patients. MATERIALS AND METHODS An electronic search of MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials, and the Web of Science was performed up to June 2014. Studies investigating the use of EIT in an adult human patient population treated with mechanical ventilation (MV) were included. Data extracted included study objectives, EIT details, interventions, MV protocol, validation and comparators, population characteristics, and key findings. RESULTS Of the 67 included studies, 35 had the primary objective of validating EIT measures including regional ventilation distribution, lung volume, regional respiratory mechanics, and nonventilatory parameters. Thirty-two studies had the primary objective of applying EIT to monitor the response to therapeutic MV interventions including change in ventilation mode, patient repositioning, endotracheal suctioning, recruitment maneuvers, and change in positive end-expiratory pressure. CONCLUSIONS In adult patients, EIT has been successfully validated for assessing ventilation distribution, measuring changes in lung volume, studying regional respiratory mechanics, and investigating nonventilatory parameters. Electrical impedance tomography has also been demonstrated to be useful in monitoring regional respiratory system changes during MV interventions, although existing literature lacks clinical outcome evidence.
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Affiliation(s)
- Jane Kobylianskii
- School of Medicine, Queen's University, Kingston, Canada; Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada
| | - Alistair Murray
- Schulich School of Medicine & Dentistry, Western University, London, Canada; Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada
| | - Debbie Brace
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada
| | - Ewan Goligher
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada
| | - Eddy Fan
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada.
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Use of basis functions within a non-linear autoregressive model of pulmonary mechanics. Biomed Signal Process Control 2016. [DOI: 10.1016/j.bspc.2016.01.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Becher T, Vogt B, Kott M, Schädler D, Weiler N, Frerichs I. Functional Regions of Interest in Electrical Impedance Tomography: A Secondary Analysis of Two Clinical Studies. PLoS One 2016; 11:e0152267. [PMID: 27010320 PMCID: PMC4806869 DOI: 10.1371/journal.pone.0152267] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 03/13/2016] [Indexed: 11/19/2022] Open
Abstract
Introduction Patients with acute respiratory distress syndrome (ARDS) typically show a high degree of ventilation inhomogeneity, which is associated with morbidity and unfavorable outcomes. Electrical impedance tomography (EIT) is able to detect ventilation inhomogeneity, but it is unclear which method for defining the region of interest (ROI) should be used for this purpose. The aim of our study was to compare the functional region of interest (fROI) method to both the lung area estimation method (LAEM) and no ROI when analysing global parameters of ventilation inhomogeneity. We assumed that a good method for ROI determination would lead to a high discriminatory power for ventilation inhomogeneity, as defined by the area under the receiver operating characteristics curve (AUC), comparing patients suffering from ARDS and control patients without pulmonary pathologies. Methods We retrospectively analysed EIT data from 24 ARDS patients and 12 control patients without pulmonary pathology. In all patients, a standardized low-flow-pressure volume maneuver had been performed and was used for EIT image generation. We compared the AUC for global inhomogeneity (GI) index and coefficient of variation (CV) between ARDS and control patients using all EIT image pixels, the fROI method and the LAEM for ROI determination. Results When analysing all EIT image pixels, we found an acceptable AUC both for the GI index (AUC = 0.76; 95% confidence interval (CI) 0.58–0.94) and the CV (AUC = 0.74; 95% CI 0.55–0.92). With the fROI method, we found a deteriorating AUC with increasing threshold criteria. With the LAEM, we found the best AUC both for the GI index (AUC = 0.89; 95% CI 0.78–1.0) and the CV (AUC = 0.89; 95% CI 0.78–1.0) using a threshold criterion of 50% of the maximum tidal impedance change. Conclusion In the assessment of ventilation inhomogeneity with EIT, functional regions of interest obscure the difference between patients with ARDS and control patients without pulmonary pathologies. The LAEM is preferable to the fROI method when assessing ventilation inhomogeneity.
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Affiliation(s)
- Tobias Becher
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3, Haus 12, 24105, Kiel, Germany
- * E-mail:
| | - Barbara Vogt
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3, Haus 12, 24105, Kiel, Germany
| | - Matthias Kott
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3, Haus 12, 24105, Kiel, Germany
| | - Dirk Schädler
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3, Haus 12, 24105, Kiel, Germany
| | - Norbert Weiler
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3, Haus 12, 24105, Kiel, Germany
| | - Inéz Frerichs
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3, Haus 12, 24105, Kiel, Germany
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Gong B, Krueger-Ziolek S, Moeller K, Schullcke B, Zhao Z. Electrical impedance tomography: functional lung imaging on its way to clinical practice? Expert Rev Respir Med 2015; 9:721-37. [DOI: 10.1586/17476348.2015.1103650] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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liu D, Kolehmainen V, Siltanen S, Laukkanen AM, Seppänen A. Estimation of conductivity changes in a region of interest with electrical impedance tomography. ACTA ACUST UNITED AC 2015. [DOI: 10.3934/ipi.2015.9.211] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Zhao Z, Pulletz S, Frerichs I, Müller-Lisse U, Möller K. The EIT-based global inhomogeneity index is highly correlated with regional lung opening in patients with acute respiratory distress syndrome. BMC Res Notes 2014; 7:82. [PMID: 24502320 PMCID: PMC3922336 DOI: 10.1186/1756-0500-7-82] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Accepted: 02/04/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The electrical impedance tomography (EIT)-based global inhomogeneity (GI) index was introduced to quantify tidal volume distribution within the lung. Up to now, the GI index was evaluated for plausibility but the analysis of how it is influenced by various physiological factors is still missing. The aim of our study was to evaluate the influence of proportion of open lung regions measured by EIT on the GI index. METHODS A constant low-flow inflation maneuver was performed in 18 acute respiratory distress syndrome (ARDS) patients (58 ± 14 years, mean age ± SD) and 8 lung-healthy patients (41 ± 12 years) under controlled mechanical ventilation. EIT raw data were acquired at 25 scans/s and reconstructed offline. Recruited lung regions were identified as those image pixels of the lung regions within the EIT scans where local impedance amplitudes exceeded 10% of the maximum amplitude during the maneuver. A series of GI indices was calculated during mechanical lung inflation, based on the differential images obtained between different time points. Respiratory system elastance (Ers) values were calculated at 10 lung volume levels during low-flow maneuver. RESULTS The GI index decreased during low-flow inflation, while the percentage of open lung regions increased. The values correlated highly in both ARDS (r2 = 0.88 ± 0.08, p < 0.01) and lung-healthy patients (r2 = 0.92 ± 0.05, p < 0.01). Ers and GI index were also significantly correlated in 16 out of 18 ARDS (r2 = 0.84 ± 0.13, p < 0.01) and in 6 out of 8 lung-healthy patients (r2 = 0.84 ± 0.07, p < 0.01). Significant differences were found in GI values between two groups (0.52 ± 0.21 for ARDS and 0.41 ± 0.04 for lung-healthy patients, p < 0.05) as well in Ers values (0.017 ± 0.008 cmH2O/ml for ARDS and 0.009 ± 0.001 cmH2O/ml for lung-healthy patients, p < 0.01). CONCLUSIONS We conclude that the GI index is a reliable measure of ventilation heterogeneity highly correlated with lung recruitability measured with EIT. The GI index may prove to be a useful EIT-based index to guide ventilation therapy.
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Affiliation(s)
- Zhanqi Zhao
- Institute of Technical Medicine, Furtwangen University, Jakob-Kienzle Straße 17, D-78054 VS-Schwenningen, Germany.
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Elke G, Fuld MK, Halaweish AF, Grychtol B, Weiler N, Hoffman EA, Frerichs I. Quantification of ventilation distribution in regional lung injury by electrical impedance tomography and xenon computed tomography. Physiol Meas 2013; 34:1303-18. [DOI: 10.1088/0967-3334/34/10/1303] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Effect of PEEP and tidal volume on ventilation distribution and end-expiratory lung volume: a prospective experimental animal and pilot clinical study. PLoS One 2013; 8:e72675. [PMID: 23991138 PMCID: PMC3750001 DOI: 10.1371/journal.pone.0072675] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 07/18/2013] [Indexed: 11/19/2022] Open
Abstract
Introduction Lung-protective ventilation aims at using low tidal volumes (VT) at optimum positive end-expiratory pressures (PEEP). Optimum PEEP should recruit atelectatic lung regions and avoid tidal recruitment and end-inspiratory overinflation. We examined the effect of VT and PEEP on ventilation distribution, regional respiratory system compliance (CRS), and end-expiratory lung volume (EELV) in an animal model of acute lung injury (ALI) and patients with ARDS by using electrical impedance tomography (EIT) with the aim to assess tidal recruitment and overinflation. Methods EIT examinations were performed in 10 anaesthetized pigs with normal lungs ventilated at 5 and 10 ml/kg body weight VT and 5 cmH2O PEEP. After ALI induction, 10 ml/kg VT and 10 cmH2O PEEP were applied. Afterwards, PEEP was set according to the pressure-volume curve. Animals were randomized to either low or high VT ventilation changed after 30 minutes in a crossover design. Ventilation distribution, regional CRS and changes in EELV were analyzed. The same measures were determined in five ARDS patients examined during low and high VT ventilation (6 and 10 (8) ml/kg) at three PEEP levels. Results In healthy animals, high compared to low VT increased CRS and ventilation in dependent lung regions implying tidal recruitment. ALI reduced CRS and EELV in all regions without changing ventilation distribution. Pressure-volume curve-derived PEEP of 21±4 cmH2O (mean±SD) resulted in comparable increase in CRS in dependent and decrease in non-dependent regions at both VT. This implied that tidal recruitment was avoided but end-inspiratory overinflation was present irrespective of VT. In patients, regional CRS differences between low and high VT revealed high degree of tidal recruitment and low overinflation at 3±1 cmH2O PEEP. Tidal recruitment decreased at 10±1 cmH2O and was further reduced at 15±2 cmH2O PEEP. Conclusions Tidal recruitment and end-inspiratory overinflation can be assessed by EIT-based analysis of regional CRS.
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Frerichs I, Dargaville PA, Rimensberger PC. Regional respiratory inflation and deflation pressure–volume curves determined by electrical impedance tomography. Physiol Meas 2013; 34:567-77. [DOI: 10.1088/0967-3334/34/6/567] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Boyle A, Adler A, Lionheart WRB. Shape deformation in two-dimensional electrical impedance tomography. IEEE TRANSACTIONS ON MEDICAL IMAGING 2012; 31:2185-2193. [PMID: 22711769 DOI: 10.1109/tmi.2012.2204438] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Electrical impedance tomography (EIT) uses measurements from surface electrodes to reconstruct an image of the conductivity of the contained medium. However, changes in measurements result from both changes in internal conductivity and changes in the shape of the medium relative to the electrode positions. Failure to account for shape changes results in a conductivity image with significant artifacts. Previous work to address shape changes in EIT has shown that in some cases boundary shape and electrode location can be uniquely determined for isotropic conductivities; however, for geometrically conformal changes, this is not possible. This prior work has shown that the shape change problem can be partially addressed. In this paper, we explore the limits of compensation for boundary movement in EIT using three approaches. First, a theoretical model was developed to separate a deformation vector field into conformal and nonconformal components, from which the reconstruction limits may be determined. Next, finite element models were used to simulate EIT measurements from a domain whose boundary has been deformed. Finally, an experimental phantom was constructed from which boundary deformation measurements were acquired. Results, both in simulation and with experimental data, suggest that some electrode movement and boundary distortions can be reconstructed based on conductivity changes alone while reducing image artifacts in the process.
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Affiliation(s)
- Alistair Boyle
- Department of Systems and Computer Engineering, Carleton University, Ottawa, ON, K1S 5B6 Canada.
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Pulletz S, Kott M, Elke G, Schädler D, Vogt B, Weiler N, Frerichs I. Dynamics of regional lung aeration determined by electrical impedance tomography in patients with acute respiratory distress syndrome. Multidiscip Respir Med 2012; 7:44. [PMID: 23153321 PMCID: PMC3528404 DOI: 10.1186/2049-6958-7-44] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Accepted: 10/31/2012] [Indexed: 11/10/2022] Open
Abstract
UNLABELLED BACKGROUND Lung tissue of patients with acute respiratory distress syndrome (ARDS) is heterogeneously damaged and prone to develop atelectasis. During inflation, atelectatic regions may exhibit alveolar recruitment accompanied by prolonged filling with air in contrast to regions with already open alveoli with a fast increase in regional aeration. During deflation, derecruitment of injured regions is possible with ongoing loss in regional aeration. The aim of our study was to assess the dynamics of regional lung aeration in mechanically ventilated patients with ARDS and its dependency on positive end-expiratory pressure (PEEP) using electrical impedance tomography (EIT). METHODS Twelve lung healthy and twenty ARDS patients were examined by EIT during sustained step increases in airway pressure from 0, 8 and 15 cm H2O to 35 cm H2O and during subsequent step decrease to the corresponding PEEP. Regional EIT waveforms in the ventral and dorsal lung regions were fitted to bi-exponential equations. Regional fast and slow respiratory time constants and the sizes of the fast and slow compartments were subsequently calculated. RESULTS ARDS patients exhibited significantly lower fast and slow time constants than the lung healthy patients in ventral and dorsal regions. The time constants were significantly affected by PEEP and differed between the regions. The size of the fast compartment was significantly lower in ARDS patients than in patients with healthy lung under all studied conditions. CONCLUSION These results show that regional lung mechanics can be assessed by EIT. They reflect the lower respiratory system compliance of injured lungs and imply more pronounced regional recruitment and derecruitment in ARDS patients.
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Affiliation(s)
- Sven Pulletz
- Department of Anaesthesiology and Intensive Care Medicine, Klinikum Osnabrück, Am Finkenhügel 1, 49076 Osnabrück, Germany.
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Chiew YS, Chase JG, Lambermont B, Janssen N, Schranz C, Moeller K, Shaw GM, Desaive T. Physiological relevance and performance of a minimal lung model: an experimental study in healthy and acute respiratory distress syndrome model piglets. BMC Pulm Med 2012; 12:59. [PMID: 22999004 PMCID: PMC3511291 DOI: 10.1186/1471-2466-12-59] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 09/19/2012] [Indexed: 11/10/2022] Open
Abstract
Background Mechanical ventilation (MV) is the primary form of support for acute respiratory distress syndrome (ARDS) patients. However, intra- and inter- patient-variability reduce the efficacy of general protocols. Model-based approaches to guide MV can be patient-specific. A physiological relevant minimal model and its patient-specific performance are tested to see if it meets this objective above. Methods Healthy anesthetized piglets weighing 24.0 kg [IQR: 21.0-29.6] underwent a step-wise PEEP increase manoeuvre from 5cmH2O to 20cmH2O. They were ventilated under volume control using Engström Care Station (Datex, General Electric, Finland), with pressure, flow and volume profiles recorded. ARDS was then induced using oleic acid. The data were analyzed with a Minimal Model that identifies patient-specific mean threshold opening and closing pressure (TOP and TCP), and standard deviation (SD) of these TOP and TCP distributions. The trial and use of data were approved by the Ethics Committee of the Medical Faculty of the University of Liege, Belgium. Results and discussions 3 of the 9 healthy piglets developed ARDS, and these data sets were included in this study. Model fitting error during inflation and deflation, in healthy or ARDS state is less than 5.0% across all subjects, indicating that the model captures the fundamental lung mechanics during PEEP increase. Mean TOP was 42.4cmH2O [IQR: 38.2-44.6] at PEEP = 5cmH2O and decreased with PEEP to 25.0cmH2O [IQR: 21.5-27.1] at PEEP = 20cmH2O. In contrast, TCP sees a reverse trend, increasing from 10.2cmH2O [IQR: 9.0-10.4] to 19.5cmH2O [IQR: 19.0-19.7]. Mean TOP increased from average 21.2-37.4cmH2O to 30.4-55.2cmH2O between healthy and ARDS subjects, reflecting the higher pressure required to recruit collapsed alveoli. Mean TCP was effectively unchanged. Conclusion The minimal model is capable of capturing physiologically relevant TOP, TCP and SD of both healthy and ARDS lungs. The model is able to track disease progression and the response to treatment.
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Affiliation(s)
- Yeong Shiong Chiew
- Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
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Schranz C, Docherty PD, Chiew YS, Chase JG, Möller K. Structural identifiability and practical applicability of an alveolar recruitment model for ARDS patients. IEEE Trans Biomed Eng 2012; 59:3396-404. [PMID: 22955868 DOI: 10.1109/tbme.2012.2216526] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Patient-specific mathematical models of respiratory mechanics can offer substantial insight into patient state and pulmonary dynamics that are not directly measurable. Thus, they offer significant potential to evaluate and guide patient-specific lung protective ventilator strategies for acute respiratory distress syndrome (ARDS) patients. To assure bedside applicability, the model must be computationally efficient and identifiable from the limited available data, while also capturing dominant dynamics and trends observed in ARDS patients. In this study, an existing static recruitment model is enhanced by considering alveolar distension and implemented in a novel time-continuous dynamic respiratory mechanics model. The model was tested for structural identifiability and a hierarchical gradient descent approach was used to fit the model to low-flow test responses of 12 ARDS patients. Finally, a comprehensive practical identifiability analysis was performed to evaluate the impact of data quality on the model parameters. Identified parameter values were physiologically plausible and very accurately reproduced the measured pressure responses. Structural identifiability of the model was proven, but practical identifiability analysis of the results showed a lack of convexity on the error surface indicating that successful parameter identification is currently not assured in all test sets. Overall, the model presented is physiologically and clinically relevant, captures ARDS dynamics, and uses clinically descriptive parameters. The patient-specific models show the ability to capture pulmonary dynamics directly relevant to patient condition and clinical guidance. These characteristics currently cannot be directly measured or established without such a validated model.
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Affiliation(s)
- Christoph Schranz
- Institute of Technical Medicine, Furtwangen University, D-78054 Villingen-Schwenningen, Germany.
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