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Heines SJH, Becher TH, van der Horst ICC, Bergmans DCJJ. Clinical Applicability of Electrical Impedance Tomography in Patient-Tailored Ventilation: A Narrative Review. Tomography 2023; 9:1903-1932. [PMID: 37888742 PMCID: PMC10611090 DOI: 10.3390/tomography9050150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 10/05/2023] [Accepted: 10/16/2023] [Indexed: 10/28/2023] Open
Abstract
Electrical Impedance Tomography (EIT) is a non-invasive bedside imaging technique that provides real-time lung ventilation information on critically ill patients. EIT can potentially become a valuable tool for optimising mechanical ventilation, especially in patients with acute respiratory distress syndrome (ARDS). In addition, EIT has been shown to improve the understanding of ventilation distribution and lung aeration, which can help tailor ventilatory strategies according to patient needs. Evidence from critically ill patients shows that EIT can reduce the duration of mechanical ventilation and prevent lung injury due to overdistension or collapse. EIT can also identify the presence of lung collapse or recruitment during a recruitment manoeuvre, which may guide further therapy. Despite its potential benefits, EIT has not yet been widely used in clinical practice. This may, in part, be due to the challenges associated with its implementation, including the need for specialised equipment and trained personnel and further validation of its usefulness in clinical settings. Nevertheless, ongoing research focuses on improving mechanical ventilation and clinical outcomes in critically ill patients.
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Affiliation(s)
- Serge J. H. Heines
- Department of Intensive Care Medicine, Maastricht University Medical Centre+, 6229 HX Maastricht, The Netherlands; (I.C.C.v.d.H.); (D.C.J.J.B.)
| | - Tobias H. Becher
- Department of Anesthesiology and Intensive Care Medicine, Campus Kiel, University Medical Centre Schleswig-Holstein, 24118 Kiel, Germany;
| | - Iwan C. C. van der Horst
- Department of Intensive Care Medicine, Maastricht University Medical Centre+, 6229 HX Maastricht, The Netherlands; (I.C.C.v.d.H.); (D.C.J.J.B.)
- Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, 6229 HX Maastricht, The Netherlands
| | - Dennis C. J. J. Bergmans
- Department of Intensive Care Medicine, Maastricht University Medical Centre+, 6229 HX Maastricht, The Netherlands; (I.C.C.v.d.H.); (D.C.J.J.B.)
- School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University, 6229 ER Maastricht, The Netherlands
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Zamani M, Kallio M, Bayford R, Demosthenous A. Generation of Anatomically Inspired Human Airway Tree Using Electrical Impedance Tomography: A Method to Estimate Regional Lung Filling Characteristics. IEEE TRANSACTIONS ON MEDICAL IMAGING 2022; 41:1125-1137. [PMID: 34914583 DOI: 10.1109/tmi.2021.3136434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The purpose of lung recruitment is to improve and optimize the air exchange flow in the lungs by adjusting the respiratory settings during mechanical ventilation. Electrical impedance tomography (EIT) is a monitoring tool that permits measurement of regional pulmonary filling characteristics or filling index (FI) during ventilation. The conventional EIT system has limitations which compromise the accuracy of the FI. This paper proposes a novel and automated methodology for accurate FI estimation based on EIT images of recruitable regional collapse and hyperdistension during incremental positive end-expiratory pressure. It identifies details of the airway tree (AT) to generate a correction factor to the FIs providing an accurate measurement. Multi-scale image enhancement followed by identification of the AT skeleton with a robust and self-exploratory tracing algorithm is used to automatically estimate the FI. AT tracing was validated using phantom data on a ground-truth lung. Based on generated phantom EIT images, including an established reference, the proposed method results in more accurate FI estimation of 65% in all quadrants compared with the current state-of-the-art. Measured regional filling characteristics were also examined by comparing regional and global impedance variations in clinically recorded data from ten different subjects. Clinical tests on filling characteristics based on extraction of the AT from the resolution enhanced EIT images indicated a more accurate result compared with the standard EIT images.
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Baron R, Kadlecek S, Loza L, Xin Y, Amzajerdian F, Duncan I, Hamedani H, Rizi R. Deriving Regionally Specific Biomarkers of Emphysema and Small Airways Disease Using Variable Threshold Parametric Response Mapping on Volumetric Lung CT Images. Acad Radiol 2022; 29 Suppl 2:S127-S136. [PMID: 34272162 PMCID: PMC8755853 DOI: 10.1016/j.acra.2021.05.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 05/20/2021] [Accepted: 05/21/2021] [Indexed: 02/03/2023]
Abstract
PURPOSE This study aims to develop and validate a parametric response mapping (PRM) methodology to accurately identify diseased regions of the lung by using variable thresholds to account for alterations in regional lung function between the gravitationally-independent (anterior) and gravitationally-dependent (posterior) lung in CT images acquired in the supine position. METHODS 34 male Sprague-Dawley rats (260-540 g) were imaged, 4 of which received elastase injection (100 units/kg) as a model for emphysema (EMPH). Gated volumetric CT was performed at end-inspiration (EI) and end-expiration (EE) on separate groups of free-breathing (n = 20) and ventilated (n = 10) rats in the supine position. To derive variable thresholds for the new PRM methodology, voxels were first grouped into 100 bins based on the fractional distance along the anterior-to-posterior direction. Lower limits of normal (LLN) for x-ray attenuation in each bin were set by determining the smallest region that enclosed 98% of voxels from healthy, ventilated animals. RESULTS When utilizing fixed thresholds in the conventional PRM methodology, a distinct posterior-anterior gradient was seen, in which nearly the entire posterior region of the lung was identified as HEALTHY, while the anterior lung was labeled as significantly less so (t(29) = -3.27, p = 0.003). In both cohorts, %SAD progressively increased from posterior to anterior, while %HEALTHY lung decreased in the same direction. After applying our PRM methodology with variable thresholds to the same rat images, the posterior-anterior trend in %SAD quantification was removed from all rats and the significant increase of diseased lung in the anterior was removed. CONCLUSIONS The PRM methodology using variable thresholds provides regionally specific markers of %SAD and %EMPH by correcting for alterations in regional lung function associated with the naturally occurring vertical gradient of dependent vs. non-dependent lung density and compliance.
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Affiliation(s)
- Ryan Baron
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Steve Kadlecek
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Luis Loza
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Yi Xin
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Faraz Amzajerdian
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Ian Duncan
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Hooman Hamedani
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Rahim Rizi
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA
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Gu W, Darquenne C. Heterogeneity in lobar and near-acini deposition of inhaled aerosol in the mouse lung. JOURNAL OF AEROSOL SCIENCE 2021; 151:105642. [PMID: 32921804 PMCID: PMC7480823 DOI: 10.1016/j.jaerosci.2020.105642] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Laboratory animals are often used to derive health risk from environmental exposure or to assess the therapeutic effect of a drug delivered by inhaled therapy. Knowledge of the in-situ distribution of deposited particles on airway and alveolar surfaces is essential in any assessment of these effects. A unique database including both high-resolution lung anatomy and deposition data in four strains of laboratory mice have been recently made publicly available to the research community (https://doi.org/10.25820/9arg-9w56). Using these data, we investigated the effect of particle size on the distribution of deposited particles at the lobar and near-acini level. Analysis was performed on a total of 33 mice where 3, 16 and 14 animals were exposed to 0.5μm, 1μm and 2μm particles, respectively. Ratio of normalized deposition to normalized volume was calculated for each lobe (DV lobe ). At the near-acini level, the skew and standard deviation of the frequency distribution of particle deposition were calculated. Significant deviation above 1 was found for DV ratio in the cranial lobe (DV Cranial ). DV Middle , DV Caudal and DV Accessory were all significantly <1 and lower than DV left (p<0.01). At the near-acini level, skew and standard deviation were positively correlated with particle size and the presence of hot spots (high deposition) were mainly found in the apical region of the lung. These results highlight the uneven distribution of deposited particles in the mouse lung. Thus, depending on the lung sample location, individual analysis to determine overall deposition may either underestimate or overestimate total lung burden, at least for micron-sized particles.
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Affiliation(s)
- W. Gu
- Department of Medicine, University of California, San Diego, USA
| | - C. Darquenne
- Department of Medicine, University of California, San Diego, USA
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Zhao Z, He H, Luo J, Adler A, Zhang X, Liu R, Lan Y, Lu S, Luo X, Lei Y, Frerichs I, Huang X, Möller K. Detection of pulmonary oedema by electrical impedance tomography: validation of previously proposed approaches in a clinical setting. Physiol Meas 2019; 40:054008. [DOI: 10.1088/1361-6579/ab1d90] [Citation(s) in RCA: 7] [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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Ambrisko TD, Schramel JP, Auer U, Moens YPS. Impact of four different recumbencies on the distribution of ventilation in conscious or anaesthetized spontaneously breathing beagle dogs: An electrical impedance tomography study. PLoS One 2017; 12:e0183340. [PMID: 28922361 PMCID: PMC5603158 DOI: 10.1371/journal.pone.0183340] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 08/02/2017] [Indexed: 11/18/2022] Open
Abstract
The aim was to examine the effects of recumbency and anaesthesia on distribution of ventilation in beagle dogs using Electrical Impedance Tomography (EIT). Nine healthy beagle dogs, aging 3.7±1.7 (mean±SD) years and weighing 16.3±1.6 kg, received a series of treatments in a fixed order on a single occasion. Conscious dogs were positioned in right lateral recumbency (RLR) and equipped with 32 EIT electrodes around the thorax. Following five minutes of equilibration, two minutes of EIT recordings were made in each recumbency in the following order: RLR, dorsal (DR), left (LLR) and sternal (SR). The dogs were then positioned in RLR, premedicated (medetomidine 0.01, midazolam 0.1, butorphanol 0.1 mg kg-1 iv) and pre-oxygenated. Fifteen minutes later anaesthesia was induced with 1 mg kg-1 propofol iv and maintained with propofol infusion (0.1–0.2 mg kg-1 minute-1 iv). After induction, the animals were intubated and allowed to breathe spontaneously (FIO2 = 1). Recordings of EIT were performed again in four recumbencies similarly to conscious state. Centre of ventilation (COV) and global inhomogeneity (GI) index were calculated from the functional EIT images. Repeated-measures ANOVA and Bonferroni tests were used for statistical analysis (p < 0.05). None of the variables changed in the conscious state. During anaesthesia left-to-right COV increased from 46.8±2.8% in DR to 49.8±2.9% in SR indicating a right shift, and ventral-to-dorsal COV increased from 49.8±1.7% in DR to 51.8±1.1% in LLR indicating a dorsal shift in distribution of ventilation. Recumbency affected distribution of ventilation in anaesthetized but not in conscious dogs. This can be related to loss of respiratory muscle tone (e.g. diaphragm) and changes in thoracic shape. Changing position of thoraco-abdominal organs under the EIT belt should be considered as alternative explanation of these findings.
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Affiliation(s)
- Tamas D Ambrisko
- Anaesthesiology and Perioperative Intensive-Care Medicine, Department for Companion Animals and Horses, University of Veterinary Medicine, Vienna, Austria
| | - Johannes P Schramel
- Anaesthesiology and Perioperative Intensive-Care Medicine, Department for Companion Animals and Horses, University of Veterinary Medicine, Vienna, Austria
| | - Ulrike Auer
- Anaesthesiology and Perioperative Intensive-Care Medicine, Department for Companion Animals and Horses, University of Veterinary Medicine, Vienna, Austria
| | - Yves P S Moens
- Anaesthesiology and Perioperative Intensive-Care Medicine, Department for Companion Animals and Horses, University of Veterinary Medicine, Vienna, Austria
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Caruana LR, Barnett AG, Tronstad O, Paratz JD, Chang AT, Fraser JF. Global tidal variations, regional distribution of ventilation, and the regional onset of filling determined by electrical impedance tomography: reproducibility. Anaesth Intensive Care 2017; 45:235-243. [PMID: 28267946 DOI: 10.1177/0310057x1704500214] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The reproducibility of the regional distribution of ventilation and the timing of onset of regional filling as measured by electrical impedance tomography lacks evidence. This study investigated whether electrical impedance tomography measurements in healthy males were reproducible when electrodes were replaced between measurements. Part 1: Recordings of five volunteers lying supine were made using electrical impedance tomography and a pneumotachometer. Measurements were repeated at least three hours later. Skin marking ensured accurate replacement of electrodes. No stabilisation period was allowed. Part 2: Electrical impedance tomography recordings of ten volunteers; a 15 minute stabilisation period, extra skin markings, and time-averaging were incorporated to improve the reproducibility. Reproducibility was determined using the Bland-Altman method. To judge the transferability of the limits of agreement, a Pearson correlation was used for electrical impedance tomography tidal variation and tidal volume. Tidal variation was judged to be reproducible due to the significant correlation between tidal variation and tidal volume (r2 = 0.93). The ventilation distribution was not reproducible. A stabilisation period, extra skin markings and time-averaging did not improve the outcome. The timing of regional onset of filling was reproducible and could prove clinically valuable. The reproducibility of the tidal variation indicates that non-reproducibility of the ventilation distribution was probably a biological difference and not measurement error. Other causes of variability such as electrode placement variability or lack of stabilisation when accounted for did not improve the reproducibility of the ventilation distribution.
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Affiliation(s)
- L R Caruana
- Physiotherapist, The Critical Care Research Group, The Prince Charles Hospital, The University of Queensland School of Medicine, Brisbane, Queensland
| | - A G Barnett
- Associate Professor, The Critical Care Research Group, The Prince Charles Hospital, School of Public Health & Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland
| | - O Tronstad
- Clinical Lead Physiotherapist, The Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland
| | - J D Paratz
- Physiotherapist, The Critical Care Research Group, The Prince Charles Hospital, Burns, Trauma and Critical Research Centre, School of Medicine, University of Queensland, Brisbane, Griffith University, Southport, Queensland
| | - A T Chang
- Physiotherapist, The Critical Care Research Group, The Prince Charles Hospital, School of Health and Rehabilitation Sciences, University of Queensland, Brisbane, Queensland
| | - J F Fraser
- Director, The Critical Care Research Group, The Prince Charles Hospital, Professor, School of Health and Rehabilitation Sciences, University of Queensland, Brisbane, Queensland
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Yerworth RJ, Frerichs I, Bayford R. Analysis and compensation for errors in electrical impedance tomography images and ventilation-related measures due to serial data collection. J Clin Monit Comput 2016; 31:1093-1101. [PMID: 27534624 PMCID: PMC5599443 DOI: 10.1007/s10877-016-9920-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 08/09/2016] [Indexed: 12/27/2022]
Abstract
Electrical impedance tomography (EIT) is increasingly being used as a bedside tool for monitoring regional lung ventilation. However, most clinical systems use serial data collection which, if uncorrected, results in image distortion, particularly at high breathing rates. The objective of this study was to determine the extent to which this affects derived parameters. Raw EIT data were acquired with the GOE-MF II EIT device (CareFusion, Höchberg, Germany) at a scan rate of 13 images/s during both spontaneous breathing and mechanical ventilation. Boundary data for periods of undisturbed tidal breathing were corrected for serial data collection errors using a Fourier based algorithm. Images were reconstructed for both the corrected and original data using the GREIT algorithm, and parameters describing the filling characteristics of the right and left lung derived on a breath by breath basis. Values from the original and corrected data were compared using paired t-tests. Of the 33 data sets, 23 showed significant differences in filling index for at least one region, 11 had significant differences in calculated tidal impedance change and 12 had significantly different filling fractions (p = 0.05). We conclude that serial collection errors should be corrected before image reconstruction to avoid clinically misleading results.
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Affiliation(s)
- Rebecca J Yerworth
- Medical Physics and Biomedical Engineering Department, University College London, London, WC1E 6BT, England, UK.
| | - Inéz Frerichs
- Department of Anaesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Richard Bayford
- Department of Natural Sciences, Middlesex University, London, England, UK
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9
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Darquenne C, Borja MG, Oakes JM, Breen EC, Olfert IM, Scadeng M, Prisk GK. Increase in relative deposition of fine particles in the rat lung periphery in the absence of gravity. J Appl Physiol (1985) 2014; 117:880-6. [PMID: 25170069 PMCID: PMC4199993 DOI: 10.1152/japplphysiol.00298.2014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 08/21/2014] [Indexed: 11/22/2022] Open
Abstract
While it is well recognized that pulmonary deposition of inhaled particles is lowered in microgravity (μG) compared with gravity on the ground (1G), the absence of sedimentation causes fine particles to penetrate deeper in the lung in μG. Using quantitative magnetic resonance imaging (MRI), we determined the effect of gravity on peripheral deposition (DEPperipheral) of fine particles. Aerosolized 0.95-μm-diameter ferric oxide particles were delivered to spontaneously breathing rats placed in plethysmographic chambers both in μG aboard the NASA Microgravity Research Aircraft and at 1G. Following exposure, lungs were perfusion fixed, fluid filled, and imaged in a 3T MR scanner. The MR signal decay rate, R2*, was measured in each voxel of the left lung from which particle deposition (DEP) was determined based on a calibration curve. Regional deposition was assessed by comparing DEP between the outer (DEPperipheral) and inner (DEPcentral) areas on each slice, and expressed as the central-to-peripheral ratio. Total lung deposition tended to be lower in μG compared with 1G (1.01 ± 0.52 vs. 1.43 ± 0.52 μg/ml, P = 0.1). In μG, DEPperipheral was larger than DEPcentral (P < 0.03), while, in 1G, DEPperipheral was not significantly different from DEPcentral. Finally, central-to-peripheral ratio was significantly less in μG than in 1G (P ≤ 0.05). These data show a larger fraction of fine particles depositing peripherally in μG than in 1G, likely beyond the large- and medium-sized airways. Although not measured, the difference in the spatial distribution of deposited particles between μG and 1G could also affect particle retention rates, with an increase in retention for particles deposited more peripherally.
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Affiliation(s)
- Chantal Darquenne
- Department of Medicine, University of California, San Diego, La Jolla, California;
| | - Maria G Borja
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California; and
| | - Jessica M Oakes
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California; and
| | - Ellen C Breen
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - I Mark Olfert
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - Miriam Scadeng
- Department of Radiology, University of California, San Diego, La Jolla, California
| | - G Kim Prisk
- Department of Medicine, University of California, San Diego, La Jolla, California; Department of Radiology, University of California, San Diego, La Jolla, California
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10
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Darquenne C. Aerosol deposition in the human lung in reduced gravity. J Aerosol Med Pulm Drug Deliv 2014; 27:170-7. [PMID: 24870702 PMCID: PMC4088354 DOI: 10.1089/jamp.2013.1079] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 09/12/2013] [Indexed: 10/25/2022] Open
Abstract
The deposition of aerosol in the human lung occurs mainly through a combination of inertial impaction, gravitational sedimentation, and diffusion. For 0.5- to 5-μm-diameter particles and resting breathing conditions, the primary mechanism of deposition in the intrathoracic airways is sedimentation, and therefore the fate of these particles is markedly affected by gravity. Studies of aerosol deposition in altered gravity have mostly been performed in humans during parabolic flights in both microgravity (μG) and hypergravity (~1.6G), where both total deposition during continuous aerosol mouth breathing and regional deposition using aerosol bolus inhalations were performed with 0.5- to 3-μm particles. Although total deposition increased with increasing gravity level, only peripheral deposition as measured by aerosol bolus inhalations was strongly dependent on gravity, with central deposition (lung depth<200 mL) being similar between gravity levels. More recently, the spatial distribution of coarse particles (mass median aerodynamic diameter≈5 μm) deposited in the human lung was assessed using planar gamma scintigraphy. The absence of gravity caused a smaller portion of 5-μm particles to deposit in the lung periphery than in the central region, where deposition occurred mainly in the airways. Indeed, 5-μm-diameter particles deposit either by inertial impaction, a mechanism most efficient in the large and medium-sized airways, or by gravitational sedimentation, which is most efficient in the distal lung. On the contrary, for fine particles (~1 μm), both aerosol bolus inhalations and studies in small animals suggest that particles deposit more peripherally in μG than in 1G, beyond the reach of the mucociliary clearance system.
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Affiliation(s)
- Chantal Darquenne
- Department of Medicine, University of California , San Diego, La Jolla, CA
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Chemonges S, Shekar K, Tung JP, Dunster KR, Diab S, Platts D, Watts RP, Gregory SD, Foley S, Simonova G, McDonald C, Hayes R, Bellpart J, Timms D, Chew M, Fung YL, Toon M, Maybauer MO, Fraser JF. Optimal management of the critically ill: anaesthesia, monitoring, data capture, and point-of-care technological practices in ovine models of critical care. BIOMED RESEARCH INTERNATIONAL 2014; 2014:468309. [PMID: 24783206 PMCID: PMC3982457 DOI: 10.1155/2014/468309] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 01/21/2014] [Accepted: 02/10/2014] [Indexed: 12/18/2022]
Abstract
Animal models of critical illness are vital in biomedical research. They provide possibilities for the investigation of pathophysiological processes that may not otherwise be possible in humans. In order to be clinically applicable, the model should simulate the critical care situation realistically, including anaesthesia, monitoring, sampling, utilising appropriate personnel skill mix, and therapeutic interventions. There are limited data documenting the constitution of ideal technologically advanced large animal critical care practices and all the processes of the animal model. In this paper, we describe the procedure of animal preparation, anaesthesia induction and maintenance, physiologic monitoring, data capture, point-of-care technology, and animal aftercare that has been successfully used to study several novel ovine models of critical illness. The relevant investigations are on respiratory failure due to smoke inhalation, transfusion related acute lung injury, endotoxin-induced proteogenomic alterations, haemorrhagic shock, septic shock, brain death, cerebral microcirculation, and artificial heart studies. We have demonstrated the functionality of monitoring practices during anaesthesia required to provide a platform for undertaking systematic investigations in complex ovine models of critical illness.
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Affiliation(s)
- Saul Chemonges
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia ; Medical Engineering Research Facility (MERF), Queensland University of Technology, Brisbane, QLD 4001, Australia
| | - Kiran Shekar
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia ; Bond University, Gold Coast, QLD 4226, Australia
| | - John-Paul Tung
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; Research and Development, Australian Red Cross Blood Service, Kelvin Grove, Brisbane, QLD 4059, Australia
| | - Kimble R Dunster
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD 4001, Australia
| | - Sara Diab
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia
| | - David Platts
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia
| | - Ryan P Watts
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; Department of Emergency Medicine, Princess Alexandra Hospital, 199 Ipswich Road, Woolloongabba, QLD 4102, Australia
| | - Shaun D Gregory
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia ; Innovative Cardiovascular Engineering and Technology Laboratory, The Prince Charles Hospital, Chermside, Brisbane, QLD 4032, Australia
| | - Samuel Foley
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia
| | - Gabriela Simonova
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia
| | - Charles McDonald
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia
| | - Rylan Hayes
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia
| | - Judith Bellpart
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia
| | - Daniel Timms
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; Innovative Cardiovascular Engineering and Technology Laboratory, The Prince Charles Hospital, Chermside, Brisbane, QLD 4032, Australia
| | - Michelle Chew
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia
| | - Yoke L Fung
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia
| | - Michael Toon
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia
| | - Marc O Maybauer
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia
| | - John F Fraser
- Critical Care Research Group Laboratory, The Prince Charles Hospital, Rode Road, Chermside, Brisbane, QLD 4032, Australia ; The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia ; Innovative Cardiovascular Engineering and Technology Laboratory, The Prince Charles Hospital, Chermside, Brisbane, QLD 4032, Australia
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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]
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Dunster KR, Friese MEJ, Fraser JF, Galloway GJ, Cowin GJ, Schibler A. Ventilation distribution in rats: Part 2--A comparison of electrical impedance tomography and hyperpolarised helium magnetic resonance imaging. Biomed Eng Online 2012; 11:68. [PMID: 22966835 PMCID: PMC3497860 DOI: 10.1186/1475-925x-11-68] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 08/22/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Hyperpolarised helium MRI (He3 MRI) is a new technique that enables imaging of the air distribution within the lungs. This allows accurate determination of the ventilation distribution in vivo. The technique has the disadvantages of requiring an expensive helium isotope, complex apparatus and moving the patient to a compatible MRI scanner. Electrical impedance tomography (EIT) a non-invasive bedside technique that allows constant monitoring of lung impedance, which is dependent on changes in air space capacity in the lung. We have used He3MRI measurements of ventilation distribution as the gold standard for assessment of EIT. METHODS Seven rats were ventilated in supine, prone, left and right lateral position with 70% helium/30% oxygen for EIT measurements and pure helium for He3 MRI. The same ventilator and settings were used for both measurements. Image dimensions, geometric centre and global in homogeneity index were calculated. RESULTS EIT images were smaller and of lower resolution and contained less anatomical detail than those from He3 MRI. However, both methods could measure positional induced changes in lung ventilation, as assessed by the geometric centre. The global in homogeneity index were comparable between the techniques. CONCLUSION EIT is a suitable technique for monitoring ventilation distribution and inhomgeneity as assessed by comparison with He3 MRI.
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Affiliation(s)
- Kimble R Dunster
- Paediatric Critical Care Research Group, Paediatric Intensive Care Unit, Mater Children's Hospital, South Brisbane, 4101, QLD, Australia.
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Dunster KR, Friese M, Fraser JF, Cowin GJ, Schibler A. Ventilation distribution in rats: Part I--The effect of gas composition as measured with electrical impedance tomography. Biomed Eng Online 2012; 11:64. [PMID: 22947026 PMCID: PMC3497876 DOI: 10.1186/1475-925x-11-64] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 08/22/2012] [Indexed: 11/17/2022] Open
Abstract
Abstract The measurement of ventilation distribution is currently performed using inhaled tracer gases for multiple breath inhalation studies or imaging techniques to quantify spatial gas distribution. Most tracer gases used for these studies have properties different from that of air. The effect of gas density on regional ventilation distribution has not been studied. This study aimed to measure the effect of gas density on regional ventilation distribution. Methods Ventilation distribution was measured in seven rats using electrical impedance tomography (EIT) in supine, prone, left and right lateral positions while being mechanically ventilated with either air, heliox (30% oxygen, 70% helium) or sulfur hexafluoride (20% SF6, 20% oxygen, 60% air). The effect of gas density on regional ventilation distribution was assessed. Results Gas density did not impact on regional ventilation distribution. The non-dependent lung was better ventilated in all four body positions. Gas density had no further impact on regional filling characteristics. The filling characteristics followed an anatomical pattern with the anterior and left lung showing a greater impedance change during the initial phase of the inspiration. Conclusion It was shown that gas density did not impact on convection dependent ventilation distribution in rats measured with EIT.
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Affiliation(s)
- Kimble R Dunster
- Paediatric Critical Care Research Group, Paediatric Intensive Care Unit, Mater Children's Hospital, South Brisbane, QLD, Australia.
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Schnidrig S, Casaulta C, Schibler A, Riedel T. Influence of end-expiratory level and tidal volume on gravitational ventilation distribution during tidal breathing in healthy adults. Eur J Appl Physiol 2012; 113:591-8. [PMID: 22872368 DOI: 10.1007/s00421-012-2469-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Accepted: 07/25/2012] [Indexed: 10/27/2022]
Abstract
Our understanding of regional filling of the lung and regional ventilation distribution is based on studies using stepwise inhalation of radiolabelled tracer gases, magnetic resonance imaging and positron emission tomography. We aimed to investigate whether these differences in ventilation distribution at different end-expiratory levels (EELs) and tidal volumes (V (T)s) held also true during tidal breathing. Electrical impedance tomography (EIT) measurements were performed in ten healthy adults in the right lateral position. Five different EELs with four different V (T)s at each EEL were tested in random order, resulting in 19 combinations. There were no measurements for the combination of the highest EEL/highest V (T). EEL and V (T) were controlled by visual feedback based on airflow. The fraction of ventilation directed to different slices of the lung (VENT(RL1)-VENT(RL8)) and the rate of the regional filling of each slice versus the total lung were analysed. With increasing EEL but normal tidal volume, ventilation was preferentially distributed to the dependent lung and the filling of the right and left lung was more homogeneous. With increasing V (T) and maintained normal EEL (FRC), ventilation was preferentially distributed to the dependent lung and regional filling became more inhomogeneous (p < 0.05). We could demonstrate that regional and temporal ventilation distribution during tidal breathing was highly influenced by EEL and V (T).
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Affiliation(s)
- Silvia Schnidrig
- Division of Paediatric and Neonatal Intensive Care Medicine, Department of Paediatrics, Inselspital, University Children's Hospital and University of Bern, 3010 Bern, Switzerland
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Abstract
PURPOSE OF REVIEW Electrical impedance tomography (EIT) is an attractive method of monitoring patients during mechanical ventilation because it can provide a noninvasive continuous image of pulmonary impedance, which indicates the distribution of ventilation. This article will discuss ongoing research on EIT, with a focus on methodological aspects and limitations and novel approaches in terms of pathophysiology, diagnosis and therapeutic advancements. RECENT FINDINGS EIT enables the detection of regional distribution of alveolar ventilation and, thus, the quantification of local inhomogeneities in lung mechanics. By detecting recruitment and derecruitment, a positive end-expiratory pressure level at which tidal ventilation is relatively homogeneous in all lung regions can be defined. Additionally, different approaches to characterize the temporal local behaviour of lung tissue during ventilation have been proposed, which adds important information. SUMMARY There is growing evidence that supports EIT usage as a bedside measure to individually optimize ventilator settings in critically ill patients in order to prevent ventilator-induced lung injury. A standardization of current approaches to analyse and interpret EIT data is required in order to facilitate the clinical implementation.
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