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Bayat S, Fardin L, Cercos-Pita JL, Perchiazzi G, Bravin A. Imaging Regional Lung Structure and Function in Small Animals Using Synchrotron Radiation Phase-Contrast and K-Edge Subtraction Computed Tomography. Front Physiol 2022; 13:825433. [PMID: 35350681 PMCID: PMC8957951 DOI: 10.3389/fphys.2022.825433] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 02/14/2022] [Indexed: 11/13/2022] Open
Abstract
Synchrotron radiation offers unique properties of coherence, utilized in phase-contrast imaging, and high flux as well as a wide energy spectrum which allow the selection of very narrow energy bands of radiation, used in K-edge subtraction imaging (KES) imaging. These properties extend X-ray computed tomography (CT) capabilities to quantitatively assess lung morphology, and to map regional lung ventilation, perfusion, inflammation, aerosol particle distribution and biomechanical properties, with microscopic spatial resolution. Four-dimensional imaging, allows the investigation of the dynamics of regional lung functional parameters simultaneously with structural deformation of the lung as a function of time. These techniques have proven to be very useful for revealing the regional differences in both lung structure and function which is crucial for better understanding of disease mechanisms as well as for evaluating treatment in small animal models of lung diseases. Here, synchrotron radiation imaging methods are described and examples of their application to the study of disease mechanisms in preclinical animal models are presented.
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Affiliation(s)
- Sam Bayat
- Univ. Grenoble Alpes, Inserm UA07 STROBE Laboratory, University of Grenoble Alpes, Grenoble, France.,Department of Pulmonology and Clinical Physiology, Grenoble University Hospital, Grenoble, France
| | - Luca Fardin
- European Synchrotron Radiation Facility, Grenoble, France
| | - José Luis Cercos-Pita
- Hedenstierna Laboratory, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden
| | - Gaetano Perchiazzi
- Hedenstierna Laboratory, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden
| | - Alberto Bravin
- Department of Physics, University of Milano-Bicocca, Milan, Italy
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Schranc Á, Balogh ÁL, Diaper J, Südy R, Peták F, Habre W, Albu G. Flow-controlled ventilation maintains gas exchange and lung aeration in a pediatric model of healthy and injured lungs: A randomized cross-over experimental study. Front Pediatr 2022; 10:1005135. [PMID: 36160799 PMCID: PMC9500311 DOI: 10.3389/fped.2022.1005135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 08/24/2022] [Indexed: 11/30/2022] Open
Abstract
Flow-controlled ventilation (FCV) is characterized by a constant flow to generate active inspiration and expiration. While the benefit of FCV on gas exchange has been demonstrated in preclinical and clinical studies with adults, the value of this modality for a pediatric population remains unknown. Thus, we aimed at observing the effects of FCV as compared to pressure-regulated volume control (PRVC) ventilation on lung mechanics, gas exchange and lung aeration before and after surfactant depletion in a pediatric model. Ten anesthetized piglets (10.4 ± 0.2 kg) were randomly assigned to start 1-h ventilation with FCV or PRVC before switching the ventilation modes for another hour. This sequence was repeated after inducing lung injury by bronchoalveolar lavage and injurious ventilation. The primary outcome was respiratory tissue elastance. Secondary outcomes included oxygenation index (PaO2/FiO2), PaCO2, intrapulmonary shunt (Qs/Qt), airway resistance, respiratory tissue damping, end-expiratory lung volume, lung clearance index and lung aeration by chest electrical impedance tomography. Measurements were performed at the end of each protocol stage. Ventilation modality had no effect on any respiratory mechanical parameter. Adequate gas exchange was provided by FCV, similar to PRVC, with sufficient CO2 elimination both in healthy and surfactant-depleted lungs (39.46 ± 7.2 mmHg and 46.2 ± 11.4 mmHg for FCV; 36.0 ± 4.1 and 39.5 ± 4.9 mmHg, for PRVC, respectively). Somewhat lower PaO2/FiO2 and higher Qs/Qt were observed in healthy and surfactant depleted lungs during FCV compared to PRVC (p < 0.05, for all). Compared to PRVC, lung aeration was significantly elevated, particularly in the ventral dependent zones during FCV (p < 0.05), but this difference was not evidenced in injured lungs. Somewhat lower oxygenation and higher shunt ratio was observed during FCV, nevertheless lung aeration improved and adequate gas exchange was ensured. Therefore, in the absence of major differences in respiratory mechanics and lung volumes, FCV may be considered as an alternative in ventilation therapy of pediatric patients with healthy and injured lungs.
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Affiliation(s)
- Álmos Schranc
- Unit for Anesthesiological Investigations, Department of Anesthesiology, Pharmacology, Intensive Care and Emergency Medicine, University of Geneva, Geneva, Switzerland
| | - Ádám L Balogh
- Unit for Anesthesiological Investigations, Department of Anesthesiology, Pharmacology, Intensive Care and Emergency Medicine, University of Geneva, Geneva, Switzerland
| | - John Diaper
- Unit for Anesthesiological Investigations, Department of Anesthesiology, Pharmacology, Intensive Care and Emergency Medicine, University of Geneva, Geneva, Switzerland
| | - Roberta Südy
- Unit for Anesthesiological Investigations, Department of Anesthesiology, Pharmacology, Intensive Care and Emergency Medicine, University of Geneva, Geneva, Switzerland
| | - Ferenc Peták
- Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary
| | - Walid Habre
- Unit for Anesthesiological Investigations, Department of Anesthesiology, Pharmacology, Intensive Care and Emergency Medicine, University of Geneva, Geneva, Switzerland.,Pediatric Anesthesia Unit, Department of Anesthesiology, Pharmacology, Intensive Care and Emergency Medicine, University Hospitals of Geneva, Geneva, Switzerland
| | - Gergely Albu
- Unit for Anesthesiological Investigations, Department of Anesthesiology, Pharmacology, Intensive Care and Emergency Medicine, University of Geneva, Geneva, Switzerland.,Division of Anesthesiology, Department of Anesthesiology, Pharmacology, Intensive Care and Emergency Medicine, University Hospitals of Geneva, Geneva, Switzerland
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Fardin L, Broche L, Lovric G, Mittone A, Stephanov O, Larsson A, Bravin A, Bayat S. Imaging atelectrauma in Ventilator-Induced Lung Injury using 4D X-ray microscopy. Sci Rep 2021; 11:4236. [PMID: 33608569 PMCID: PMC7895928 DOI: 10.1038/s41598-020-77300-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 11/04/2020] [Indexed: 02/07/2023] Open
Abstract
Mechanical ventilation can damage the lungs, a condition called Ventilator-Induced Lung Injury (VILI). However, the mechanisms leading to VILI at the microscopic scale remain poorly understood. Here we investigated the within-tidal dynamics of cyclic recruitment/derecruitment (R/D) using synchrotron radiation phase-contrast imaging (PCI), and the relation between R/D and cell infiltration, in a model of Acute Respiratory Distress Syndrome in 6 anaesthetized and mechanically ventilated New-Zealand White rabbits. Dynamic PCI was performed at 22.6 µm voxel size, under protective mechanical ventilation [tidal volume: 6 ml/kg; positive end-expiratory pressure (PEEP): 5 cmH2O]. Videos and quantitative maps of within-tidal R/D showed that injury propagated outwards from non-aerated regions towards adjacent regions where cyclic R/D was present. R/D of peripheral airspaces was both pressure and time-dependent, occurring throughout the respiratory cycle with significant scatter of opening/closing pressures. There was a significant association between R/D and regional lung cellular infiltration (p = 0.04) suggesting that tidal R/D of the lung parenchyma may contribute to regional lung inflammation or capillary-alveolar barrier dysfunction and to the progression of lung injury. PEEP may not fully mitigate this phenomenon even at high levels. Ventilation strategies utilizing the time-dependence of R/D may be helpful in reducing R/D and associated injury.
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Affiliation(s)
- Luca Fardin
- European Synchrotron Radiation Facility, Grenoble, France.,Hedenstierna Laboratory, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden.,Synchrotron Radiation for Biomedicine Laboratory (STROBE, INSERM UA7), Grenoble, France
| | - Ludovic Broche
- European Synchrotron Radiation Facility, Grenoble, France
| | - Goran Lovric
- Center for Biomedical Imaging, EPFL, Lausanne, Switzerland.,Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland
| | | | - Olivier Stephanov
- Department of Pathology, Grenoble University Hospital, Grenoble, France
| | - Anders Larsson
- Hedenstierna Laboratory, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden
| | - Alberto Bravin
- European Synchrotron Radiation Facility, Grenoble, France.,Synchrotron Radiation for Biomedicine Laboratory (STROBE, INSERM UA7), Grenoble, France
| | - Sam Bayat
- Synchrotron Radiation for Biomedicine Laboratory (STROBE, INSERM UA7), Grenoble, France. .,Department of Pulmonology and Physiology, Grenoble University Hospital, Bd. Du Maquis du Grésivaudan, 38700, La Tronche, France.
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Dos Santos Rocha A, Fodor GH, Kassai M, Degrugilliers L, Bayat S, Petak F, Habre W. Physiologically variable ventilation reduces regional lung inflammation in a pediatric model of acute respiratory distress syndrome. Respir Res 2020; 21:288. [PMID: 33129315 PMCID: PMC7602830 DOI: 10.1186/s12931-020-01559-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 10/26/2020] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Benefits of variable mechanical ventilation based on the physiological breathing pattern have been observed both in healthy and injured lungs. These benefits have not been characterized in pediatric models and the effect of this ventilation mode on regional distribution of lung inflammation also remains controversial. Here, we compare structural, molecular and functional outcomes reflecting regional inflammation between PVV and conventional pressure-controlled ventilation (PCV) in a pediatric model of healthy lungs and acute respiratory distress syndrome (ARDS). METHODS New-Zealand White rabbit pups (n = 36, 670 ± 20 g [half-width 95% confidence interval]), with healthy lungs or after induction of ARDS, were randomized to five hours of mechanical ventilation with PCV or PVV. Regional lung aeration, inflammation and perfusion were assessed using x-ray computed tomography, positron-emission tomography and single-photon emission computed tomography, respectively. Ventilation parameters, blood gases and respiratory tissue elastance were recorded hourly. RESULTS Mechanical ventilation worsened respiratory elastance in healthy and ARDS animals ventilated with PCV (11 ± 8%, 6 ± 3%, p < 0.04), however, this trend was improved by PVV (1 ± 4%, - 6 ± 2%). Animals receiving PVV presented reduced inflammation as assessed by lung normalized [18F]fluorodeoxyglucose uptake in healthy (1.49 ± 0.62 standardized uptake value, SUV) and ARDS animals (1.86 ± 0.47 SUV) compared to PCV (2.33 ± 0.775 and 2.28 ± 0.3 SUV, respectively, p < 0.05), particularly in the well and poorly aerated lung zones. No benefit of PVV could be detected on regional blood perfusion or blood gas parameters. CONCLUSIONS Variable ventilation based on a physiological respiratory pattern, compared to conventional pressure-controlled ventilation, reduced global and regional inflammation in both healthy and injured lungs of juvenile rabbits.
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Affiliation(s)
- Andre Dos Santos Rocha
- Unit for Anaesthesiological Investigations, Department of Acute Medicine, University Hospitals of Geneva and University of Geneva, rue Willy Donzé 6, 1205, Geneva, Switzerland.
| | - Gergely H Fodor
- Unit for Anaesthesiological Investigations, Department of Acute Medicine, University Hospitals of Geneva and University of Geneva, rue Willy Donzé 6, 1205, Geneva, Switzerland.,Department of Medical Physics and Informatics, University of Szeged, 9 Korányi fasor, Szeged, 6720, Hungary
| | - Miklos Kassai
- Unit for Anaesthesiological Investigations, Department of Acute Medicine, University Hospitals of Geneva and University of Geneva, rue Willy Donzé 6, 1205, Geneva, Switzerland
| | - Loic Degrugilliers
- Department of Pediatric Intensive Care, Amiens University Hospital, Amiens, France
| | - Sam Bayat
- Inserm UA7 STROBE Laboratory &, Department of Clinical Physiology, Sleep and Exercise, Grenoble University Hospital, Boulevard de La Chantourne, 38700, Grenoble, La Tronche, France
| | - Ferenc Petak
- Department of Medical Physics and Informatics, University of Szeged, 9 Korányi fasor, Szeged, 6720, Hungary
| | - Walid Habre
- Unit for Anaesthesiological Investigations, Department of Acute Medicine, University Hospitals of Geneva and University of Geneva, rue Willy Donzé 6, 1205, Geneva, Switzerland
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Functional lung imaging with synchrotron radiation: Methods and preclinical applications. Phys Med 2020; 79:22-35. [PMID: 33070047 DOI: 10.1016/j.ejmp.2020.10.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 09/30/2020] [Accepted: 10/03/2020] [Indexed: 01/05/2023] Open
Abstract
Many lung disease processes are characterized by structural and functional heterogeneity that is not directly appreciable with traditional physiological measurements. Experimental methods and lung function modeling to study regional lung function are crucial for better understanding of disease mechanisms and for targeting treatment. Synchrotron radiation offers useful properties to this end: coherence, utilized in phase-contrast imaging, and high flux and a wide energy spectrum which allow the selection of very narrow energy bands of radiation, thus allowing imaging at very specific energies. K-edge subtraction imaging (KES) has thus been developed at synchrotrons for both human and small animal imaging. The unique properties of synchrotron radiation extend X-ray computed tomography (CT) capabilities to quantitatively assess lung morphology, and also to map regional lung ventilation, perfusion, inflammation and biomechanical properties, with microscopic spatial resolution. Four-dimensional imaging, allows the investigation of the dynamics of regional lung functional parameters simultaneously with structural deformation of the lung as a function of time. This review summarizes synchrotron radiation imaging methods and overviews examples of its application in the study of disease mechanisms in preclinical animal models, as well as the potential for clinical translation both through the knowledge gained using these techniques and transfer of imaging technology to laboratory X-ray sources.
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Yehya N. Lessons learned in acute respiratory distress syndrome from the animal laboratory. ANNALS OF TRANSLATIONAL MEDICINE 2019; 7:503. [PMID: 31728356 DOI: 10.21037/atm.2019.09.33] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Since the description of the acute respiratory distress syndrome (ARDS) in 1967, investigators have struggled to reproduce the syndrome in the animal laboratory. While several different models of experimental acute lung injury (ALI) have been developed, none completely capture the inciting etiologies, initial inflammation, heterogeneity, and resolution of human ARDS. This potentially has contributed to the poor translation of potential therapeutics between animal ALI models and human ARDS. It was only recently that standardized criteria were suggested for what makes an ALI model comparable to human ARDS. Nevertheless, despite model heterogeneity, these models have contributed substantially to our understanding of the syndrome. From the initial studies identifying the risks of mechanical ventilation to the identification of potentially targetable inflammatory mediators, to modern studies focusing on regional heterogeneity and novel molecular pathways, animal models continue to inform our understanding of ARDS. This review will cover several major lessons learned from animal models of ALI, and provide some direction for future studies in this field.
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Affiliation(s)
- Nadir Yehya
- Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia and University of Pennsylvania, Philadelphia, PA, USA
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7
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Individual Airway Closure Characterized In Vivo by Phase-Contrast CT Imaging in Injured Rabbit Lung*. Crit Care Med 2019; 47:e774-e781. [DOI: 10.1097/ccm.0000000000003838] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Fodor GH, Bayat S, Albu G, Lin N, Baudat A, Danis J, Peták F, Habre W. Variable Ventilation Is Equally Effective as Conventional Pressure Control Ventilation for Optimizing Lung Function in a Rabbit Model of ARDS. Front Physiol 2019; 10:803. [PMID: 31297064 PMCID: PMC6607923 DOI: 10.3389/fphys.2019.00803] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 06/06/2019] [Indexed: 11/24/2022] Open
Abstract
Background Introducing mathematically derived variability (MVV) into the otherwise monotonous conventional mechanical ventilation has been suggested to improve lung recruitment and gas exchange. Although the application of a ventilation pattern based on variations in physiological breathing (PVV) is beneficial for healthy lungs, its value in the presence of acute respiratory distress syndrome (ARDS) has not been characterized. We therefore aimed at comparing conventional pressure-controlled ventilation with (PCS) or without regular sighs (PCV) to MVV and PVV at two levels of positive end-expiratory pressure (PEEP) in a model of severe ARDS. Methods Anesthetised rabbits (n = 54) were mechanically ventilated and severe ARDS (PaO2/FiO2 ≤ 150 mmHg) was induced by combining whole lung lavage, i.v. endotoxin and injurious ventilation. Rabbits were then randomly assigned to be ventilated with PVV, MVV, PCV, or PCS for 5 h while maintaining either 6 or 9 cmH2O PEEP. Ventilation parameters, blood gas indices and respiratory mechanics (tissue damping, G, and elastance, H) were recorded hourly. Serum cytokine levels were assessed with ELISA and lung histology was analyzed. Results Although no progression of lung injury was observed after 5 h of ventilation at PEEP 6 cmH2O with PVV and PCV, values for G (58.8 ± 71.1[half-width of 95% CI]% and 40.8 ± 39.0%, respectively), H (54.5 ± 57.2%, 50.7 ± 28.3%), partial pressure of carbon-dioxide (PaCO2, 43.9 ± 23.8%, 46.2 ± 35.4%) and pH (−4.6 ± 3.3%, −4.6 ± 2.2%) worsened with PCS and MVV. Regardless of ventilation pattern, application of a higher PEEP improved lung function and precluded progression of lung injury and inflammation. Histology lung injury scores were elevated in all groups with no difference between groups at either PEEP level. Conclusion At moderate PEEP, variable ventilation based on a pre-recorded physiological breathing pattern protected against progression of lung injury equally to the conventional pressure-controlled mode, whereas mathematical variability or application of regular sighs caused worsening in lung mechanics. This outcome may be related to the excessive increases in peak inspiratory pressure with the latter ventilation modes. However, a greater benefit on respiratory mechanics and gas exchange could be obtained by elevating PEEP, compared to the ventilation mode in severe ARDS.
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Affiliation(s)
- Gergely H Fodor
- Unit for Anesthesiological Investigations, Geneva University Hospitals - University of Geneva, Geneva, Switzerland
| | - Sam Bayat
- Unit for Anesthesiological Investigations, Geneva University Hospitals - University of Geneva, Geneva, Switzerland.,Inserm UA7 STROBE Laboratory, Department of Clinical Physiology, Sleep and Exercise, Grenoble University Hospital, Grenoble, France
| | - Gergely Albu
- Unit for Anesthesiological Investigations, Geneva University Hospitals - University of Geneva, Geneva, Switzerland
| | - Na Lin
- Unit for Anesthesiological Investigations, Geneva University Hospitals - University of Geneva, Geneva, Switzerland.,Department of Anesthesiology, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Aurélie Baudat
- Unit for Anesthesiological Investigations, Geneva University Hospitals - University of Geneva, Geneva, Switzerland
| | - Judit Danis
- MTA-SZTE Dermatological Research Group, University of Szeged, Szeged, Hungary
| | - Ferenc Peták
- Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary
| | - Walid Habre
- Unit for Anesthesiological Investigations, Geneva University Hospitals - University of Geneva, Geneva, Switzerland
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Motta-Ribeiro G, Winkler T, Hashimoto S, Vidal Melo MF. Spatial Heterogeneity of Lung Strain and Aeration and Regional Inflammation During Early Lung Injury Assessed with PET/CT. Acad Radiol 2019; 26:313-325. [PMID: 30057194 PMCID: PMC6612262 DOI: 10.1016/j.acra.2018.02.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 01/20/2018] [Accepted: 02/27/2018] [Indexed: 12/23/2022]
Abstract
INTRODUCTION Spatial heterogeneity of lung aeration and strain (change volume/resting volume) occurs at microscopic levels and contributes to lung injury. Yet, it is mostly assessed with histograms or large regions-of-interest. Spatial heterogeneity could also influence regional gene expression. We used positron emission tomography (PET)/computed tomography (CT) to assess the contribution of different length-scales to mechanical heterogeneity and to direct lung injury biological pathway identification. MATERIALS AND METHODS Sheep exposed to mild (n = 5, supine and n = 3, prone) and moderate (n = 6, supine) systemic endotoxemia were protectively ventilated. At baseline, 6 hours and 20 hours length-scale analysis was applied to aeration in CT (mild groups) and PET transmission (moderate group) scans; and voxel-level strain derived from image registration of end-inspiratory and end-expiratory CTs (mild). 2-deoxy-2-[(18)F]fluoro-d-glucose (18F-FDG)-PET kinetics parameters in ventral and dorsal regions were correlated with tissue microarray gene expression (moderate). RESULTS While aeration and strain heterogeneity were highest at 5-10 mm length-scales, larger length-scales contained a higher fraction of strain than aeration heterogeneity. Contributions of length-scales >5-10 mm to aeration and strain heterogeneity increased as lung injury progressed (p < 0.001) and were higher in supine than prone animals. Genes expressed with regional correlation to 18F-FDG-PET kinetics (|r| = 0.81 [0.78-0.85]) yielded pathways associated with immune system activation and fluid clearance. CONCLUSION Normal spatial heterogeneity of aeration and strain suggest larger anatomical and functional determinants of lung strain than aeration heterogeneity. Lung injury and supine position increase the contribution of larger length-scales. 18F-FDG-PET-based categorization of gene expression results in known and novel biological pathways relevant to lung injury.
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Affiliation(s)
- Gabriel Motta-Ribeiro
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit St, Boston, MA 02114.
| | - Tilo Winkler
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit St, Boston, MA 02114.
| | - Soshi Hashimoto
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit St, Boston, MA 02114.
| | - Marcos F Vidal Melo
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit St, Boston, MA 02114.
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Schittny JC. How high resolution 3-dimensional imaging changes our understanding of postnatal lung development. Histochem Cell Biol 2018; 150:677-691. [PMID: 30390117 PMCID: PMC6267404 DOI: 10.1007/s00418-018-1749-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/19/2018] [Indexed: 12/24/2022]
Abstract
During the last 10 + years biologically and clinically significant questions about postnatal lung development could be answered due to the application of modern cutting-edge microscopic and quantitative histological techniques. These are in particular synchrotron radiation based X-ray tomographic microscopy (SRXTM), but also 3Helium Magnetic Resonance Imaging, as well as the stereological estimation of the number of alveoli and the length of the free septal edge. First, the most important new finding may be the following: alveolarization of the lung does not cease after the maturation of the alveolar microvasculature but continues until young adulthood and, even more important, maybe reactivated lifelong if needed to rescue structural damages of the lungs. Second, the pulmonary acinus represents the functional unit of the lung. Because the borders of the acini could not be detected in classical histological sections, any investigation of the acini requires 3-dimensional (imaging) methods. Based on SRXTM it was shown that in rat lungs the number of acini stays constant, meaning that their volume increases by a factor of ~ 11 after birth. The latter is very important for acinar ventilation and particle deposition.
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Affiliation(s)
- Johannes C Schittny
- Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3012, Bern, Switzerland.
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11
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Walesa M, Bayat S, Albu G, Baudat A, Petak F, Habre W. Comparison between neurally-assisted, controlled, and physiologically variable ventilation in healthy rabbits. Br J Anaesth 2018; 121:918-927. [DOI: 10.1016/j.bja.2018.01.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 01/08/2018] [Accepted: 01/25/2018] [Indexed: 10/17/2022] Open
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12
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Thomlinson W, Elleaume H, Porra L, Suortti P. K-edge subtraction synchrotron X-ray imaging in bio-medical research. Phys Med 2018; 49:58-76. [DOI: 10.1016/j.ejmp.2018.04.389] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Revised: 04/12/2018] [Accepted: 04/16/2018] [Indexed: 11/26/2022] Open
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13
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Porra L, Dégrugilliers L, Broche L, Albu G, Strengell S, Suhonen H, Fodor GH, Peták F, Suortti P, Habre W, Sovijärvi ARA, Bayat S. Quantitative Imaging of Regional Aerosol Deposition, Lung Ventilation and Morphology by Synchrotron Radiation CT. Sci Rep 2018; 8:3519. [PMID: 29476086 PMCID: PMC5824954 DOI: 10.1038/s41598-018-20986-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 01/29/2018] [Indexed: 01/02/2023] Open
Abstract
To understand the determinants of inhaled aerosol particle distribution and targeting in the lung, knowledge of regional deposition, lung morphology and regional ventilation, is crucial. No single imaging modality allows the acquisition of all such data together. Here we assessed the feasibility of dual-energy synchrotron radiation imaging to this end in anesthetized rabbits; both in normal lung (n = 6) and following methacholine (MCH)-induced bronchoconstriction (n = 6), a model of asthma. We used K-edge subtraction CT (KES) imaging to quantitatively map the regional deposition of iodine-containing aerosol particles. Morphological and regional ventilation images were obtained, followed by quantitative regional iodine deposition maps, after 5 and 10 minutes of aerosol administration. Iodine deposition was markedly inhomogeneous both in normal lung and after induced bronchoconstrition. Deposition was significantly reduced in the MCH group at both time points, with a strong dependency on inspiratory flow in both conditions (R2 = 0.71; p < 0.0001). We demonstrate for the first time, the feasibility of KES CT for quantitative imaging of lung deposition of aerosol particles, regional ventilation and morphology. Since these are among the main factors determining lung aerosol deposition, we expect this imaging approach to bring new contributions to the understanding of lung aerosol delivery, targeting, and ultimately biological efficacy.
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Affiliation(s)
- L Porra
- Department of Physics, University of Helsinki, Helsinki, Finland.,Helsinki University Central Hospital Medical Imaging Center, Helsinki, Finland
| | - L Dégrugilliers
- Department of Pediatric Intensive Care, Amiens University Hospital, Amiens, France
| | - L Broche
- Hedenstierna Laboratory, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden
| | - G Albu
- Anesthesiological Investigations Unit, University Hospitals of Geneva, Geneva, Switzerland
| | - S Strengell
- Department of Physics, University of Helsinki, Helsinki, Finland.,Helsinki University Central Hospital Medical Imaging Center, Helsinki, Finland
| | - H Suhonen
- Department of Physics, University of Helsinki, Helsinki, Finland
| | - G H Fodor
- Anesthesiological Investigations Unit, University Hospitals of Geneva, Geneva, Switzerland
| | - F Peták
- Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary
| | - P Suortti
- Department of Physics, University of Helsinki, Helsinki, Finland
| | - W Habre
- Anesthesiological Investigations Unit, University Hospitals of Geneva, Geneva, Switzerland
| | - A R A Sovijärvi
- Department of Clinical Physiology and Nuclear Medicine, Helsinki University Central Hospital and University of Helsinki, Helsinki, Finland
| | - S Bayat
- University of Grenoble EA-7442 RSRM Laboratory and Department of Clinical Physiology, Sleep and Exercise, Grenoble University Hospital, Grenoble, France.
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Paula LF, Wellman TJ, Winkler T, Spieth PM, Güldner A, Venegas JG, Gama de Abreu M, Carvalho AR, Vidal Melo MF. Regional tidal lung strain in mechanically ventilated normal lungs. J Appl Physiol (1985) 2016; 121:1335-1347. [PMID: 27445302 PMCID: PMC5206384 DOI: 10.1152/japplphysiol.00861.2015] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 07/05/2016] [Indexed: 01/12/2023] Open
Abstract
Parenchymal strain is a key determinant of lung injury produced by mechanical ventilation. However, imaging estimates of volumetric tidal strain (ε = regional tidal volume/reference volume) present substantial conceptual differences in reference volume computation and consideration of tidally recruited lung. We compared current and new methods to estimate tidal volumetric strains with computed tomography, and quantified the effect of tidal volume (VT) and positive end-expiratory pressure (PEEP) on strain estimates. Eight supine pigs were ventilated with VT = 6 and 12 ml/kg and PEEP = 0, 6, and 12 cmH2O. End-expiratory and end-inspiratory scans were analyzed in eight regions of interest along the ventral-dorsal axis. Regional reference volumes were computed at end-expiration (with/without correction of regional VT for intratidal recruitment) and at resting lung volume (PEEP = 0) corrected for intratidal and PEEP-derived recruitment. All strain estimates demonstrated vertical heterogeneity with the largest tidal strains in middependent regions (P < 0.01). Maximal strains for distinct estimates occurred at different lung regions and were differently affected by VT-PEEP conditions. Values consistent with lung injury and inflammation were reached regionally, even when global measurements were below critical levels. Strains increased with VT and were larger in middependent than in nondependent lung regions. PEEP reduced tidal-strain estimates referenced to end-expiratory lung volumes, although it did not affect strains referenced to resting lung volume. These estimates of tidal strains in normal lungs point to middependent lung regions as those at risk for ventilator-induced lung injury. The different conditions and topography at which maximal strain estimates occur allow for testing the importance of each estimate for lung injury.
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Affiliation(s)
- Luis Felipe Paula
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts
- Laboratory of Respiration Physiology, Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Tyler J Wellman
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts
| | - Tilo Winkler
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts
| | - Peter M Spieth
- Pulmonary Engineering Group, Department of Anesthesiology and Intensive Care Therapy, University Hospital Carl Gustav Carus, Dresden, Germany; and
| | - Andreas Güldner
- Pulmonary Engineering Group, Department of Anesthesiology and Intensive Care Therapy, University Hospital Carl Gustav Carus, Dresden, Germany; and
| | - Jose G Venegas
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts
| | - Marcelo Gama de Abreu
- Pulmonary Engineering Group, Department of Anesthesiology and Intensive Care Therapy, University Hospital Carl Gustav Carus, Dresden, Germany; and
| | - Alysson R Carvalho
- Laboratory of Respiration Physiology, Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
- Pulmonary Engineering Group, Department of Anesthesiology and Intensive Care Therapy, University Hospital Carl Gustav Carus, Dresden, Germany; and
- Laboratory of Pulmonary Engineering, Alberto Luiz Coimbra Institute of Post-Graduation and Research in Engineering, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Marcos F Vidal Melo
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts;
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16
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Dhanani J, Fraser JF, Chan HK, Rello J, Cohen J, Roberts JA. Fundamentals of aerosol therapy in critical care. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2016; 20:269. [PMID: 27716346 PMCID: PMC5054555 DOI: 10.1186/s13054-016-1448-5] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Drug dosing in critically ill patients is challenging due to the altered drug pharmacokinetics–pharmacodynamics associated with systemic therapies. For many drug therapies, there is potential to use the respiratory system as an alternative route for drug delivery. Aerosol drug delivery can provide many advantages over conventional therapy. Given that respiratory diseases are the commonest causes of critical illness, use of aerosol therapy to provide high local drug concentrations with minimal systemic side effects makes this route an attractive option. To date, limited evidence has restricted its wider application. The efficacy of aerosol drug therapy depends on drug-related factors (particle size, molecular weight), device factors, patient-related factors (airway anatomy, inhalation patterns) and mechanical ventilation-related factors (humidification, airway). This review identifies the relevant factors which require attention for optimization of aerosol drug delivery that can achieve better drug concentrations at the target sites and potentially improve clinical outcomes.
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Affiliation(s)
- Jayesh Dhanani
- Burns, Trauma and Critical Care Research Centre, The University of Queensland, Brisbane, Australia. .,Department of Intensive Care Medicine, Royal Brisbane and Women's Hospital, Level 3, Ned Hanlon Building, Herston, 4029, QLD, Australia.
| | - John F Fraser
- Department of Intensive Care Medicine, The Prince Charles Hospital, Brisbane, Australia.,Critical Care Research Group, The University of Queensland, Brisbane, Australia
| | - Hak-Kim Chan
- Advanced Drug Delivery Group, Faculty of Pharmacy, The University of Sydney, Sydney, NSW, Australia
| | - Jordi Rello
- Critical Care Department, Hospital Vall d'Hebron, Barcelona, Spain.,CIBERES, Vall d'Hebron Institut of Research, Barcelona, Spain.,Department of Medicine, Universitat Autonoma de Barcelona, Barcelona, Spain
| | - Jeremy Cohen
- Burns, Trauma and Critical Care Research Centre, The University of Queensland, Brisbane, Australia.,Department of Intensive Care Medicine, Royal Brisbane and Women's Hospital, Level 3, Ned Hanlon Building, Herston, 4029, QLD, Australia
| | - Jason A Roberts
- Burns, Trauma and Critical Care Research Centre, The University of Queensland, Brisbane, Australia.,Department of Intensive Care Medicine, Royal Brisbane and Women's Hospital, Level 3, Ned Hanlon Building, Herston, 4029, QLD, Australia.,Pharmacy Department, Royal Brisbane and Women's Hospital, Herston, Brisbane, Australia.,School of Pharmacy, The University of Queensland, Brisbane, Australia
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17
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Pressure-regulated volume control vs. volume control ventilation in healthy and injured rabbit lung. Eur J Anaesthesiol 2016; 33:767-75. [DOI: 10.1097/eja.0000000000000485] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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18
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Borges JB, Porra L, Pellegrini M, Tannoia A, Derosa S, Larsson A, Bayat S, Perchiazzi G, Hedenstierna G. Zero expiratory pressure and low oxygen concentration promote heterogeneity of regional ventilation and lung densities. Acta Anaesthesiol Scand 2016; 60:958-68. [PMID: 27000315 PMCID: PMC5071663 DOI: 10.1111/aas.12719] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 01/20/2016] [Accepted: 02/11/2016] [Indexed: 12/26/2022]
Abstract
Background It is not well known what is the main mechanism causing lung heterogeneity in healthy lungs under mechanical ventilation. We aimed to investigate the mechanisms causing heterogeneity of regional ventilation and parenchymal densities in healthy lungs under anesthesia and mechanical ventilation. Methods In a small animal model, synchrotron imaging was used to measure lung aeration and regional‐specific ventilation (sV̇). Heterogeneity of ventilation was calculated as the coefficient of variation in sV̇ (CVsV̇). The coefficient of variation in lung densities (CVD) was calculated for all lung tissue, and within hyperinflated, normally and poorly aerated areas. Three conditions were studied: zero end‐expiratory pressure (ZEEP) and FIO2 0.21; ZEEP and FIO2 1.0; PEEP 12 cmH2O and FIO21.0 (Open Lung‐PEEP = OLP). Results The mean tissue density at OLP was lower than ZEEP‐1.0 and ZEEP‐0.21. There were larger subregions with low sV̇ and poor aeration at ZEEP‐0.21 than at OLP: 12.9 ± 9.0 vs. 0.6 ± 0.4% in the non‐dependent level, and 17.5 ± 8.2 vs. 0.4 ± 0.1% in the dependent one (P = 0.041). The CVsV̇ of the total imaged lung at PEEP 12 cmH2O was significantly lower than on ZEEP, regardless of FIO2, indicating more heterogeneity of ventilation during ZEEP (0.23 ± 0.03 vs. 0.54 ± 0.37, P = 0.049). CVD changed over the different mechanical ventilation settings (P = 0.011); predominantly, CVD increased during ZEEP. The spatial distribution of the CVD calculated for the poorly aerated density category changed with the mechanical ventilation settings, increasing in the dependent level during ZEEP. Conclusion ZEEP together with low FIO2 promoted heterogeneity of ventilation and lung tissue densities, fostering a greater amount of airway closure and ventilation inhomogeneities in poorly aerated regions.
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Affiliation(s)
- J. B. Borges
- Hedenstierna Laboratory Department of Surgical Sciences Section of Anaesthesiology & Critical Care Uppsala University Uppsala Sweden
- Pulmonary Divison Heart Institute (Incor) Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo Brazil
| | - L. Porra
- Department of Physics University of Helsinki Helsinki Finland
- Helsinki University Central Hospital Helsinki Finland
| | - M. Pellegrini
- Department of Emergency and Organ Transplant Bari University Italy
| | - A. Tannoia
- Department of Emergency and Organ Transplant Bari University Italy
| | - S. Derosa
- Department of Emergency and Organ Transplant Bari University Italy
| | - A. Larsson
- Hedenstierna Laboratory Department of Surgical Sciences Section of Anaesthesiology & Critical Care Uppsala University Uppsala Sweden
| | - S. Bayat
- Inserm UMR1105 and Pediatric Lung Function Laboratory CHU Amiens Université de Picardie Jules Verne Amiens France
| | - G. Perchiazzi
- Hedenstierna Laboratory Department of Surgical Sciences Section of Anaesthesiology & Critical Care Uppsala University Uppsala Sweden
- Department of Emergency and Organ Transplant Bari University Italy
| | - G. Hedenstierna
- Hedenstierna Laboratory Department of Medical Sciences Clinical Physiology Uppsala University Uppsala Sweden
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Abstract
BACKGROUND Mechanical ventilation worsens acute respiratory distress syndrome, but this secondary "ventilator-associated" injury is variable and difficult to predict. The authors aimed to visualize the propagation of such ventilator-induced injury, in the presence (and absence) of a primary underlying lung injury, and to determine the predictors of propagation. METHODS Anesthetized rats (n = 20) received acid aspiration (hydrochloric acid) followed by ventilation with moderate tidal volume (V(T)). In animals surviving ventilation for at least 2 h, propagation of injury was quantified by using serial computed tomography. Baseline lung status was assessed by oxygenation, lung weight, and lung strain (V(T)/expiratory lung volume). Separate groups of rats without hydrochloric acid aspiration were ventilated with large (n = 10) or moderate (n = 6) V(T). RESULTS In 15 rats surviving longer than 2 h, computed tomography opacities spread outward from the initial site of injury. Propagation was associated with higher baseline strain (propagation vs. no propagation [mean ± SD]: 1.52 ± 0.13 vs. 1.16 ± 0.20, P < 0.01) but similar oxygenation and lung weight. Propagation did not occur where baseline strain was less than 1.29. In healthy animals, large V(T) caused injury that was propagated inward from the lung periphery; in the absence of preexisting injury, propagation did not occur where strain was less than 2.0. CONCLUSIONS Compared with healthy lungs, underlying injury causes propagation to occur at a lower strain threshold and it originates at the site of injury; this suggests that tissue around the primary lesion is more sensitive. Understanding how injury is propagated may ultimately facilitate a more individualized monitoring or management.
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20
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Cereda M, Xin Y, Hamedani H, Clapp J, Kadlecek S, Meeder N, Zeng J, Profka H, Kavanagh BP, Rizi RR. Mild loss of lung aeration augments stretch in healthy lung regions. J Appl Physiol (1985) 2015; 120:444-54. [PMID: 26662053 DOI: 10.1152/japplphysiol.00734.2015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 12/07/2015] [Indexed: 11/22/2022] Open
Abstract
Inspiratory stretch by mechanical ventilation worsens lung injury. However, it is not clear whether and how the ventilator damages lungs in the absence of preexisting injury. We hypothesized that subtle loss of lung aeration during general anesthesia regionally augments ventilation and distension of ventilated air spaces. In eight supine anesthetized and intubated rats, hyperpolarized gas MRI was performed after a recruitment maneuver following 1 h of volume-controlled ventilation with zero positive end-expiratory pressure (ZEEP), FiO2 0.5, and tidal volume 10 ml/kg, and after a second recruitment maneuver. Regional fractional ventilation (FV), apparent diffusion coefficient (ADC) of (3)He (a measurement of ventilated peripheral air space dimensions), and gas volume were measured in lung quadrants of ventral and dorsal regions of the lungs. In six additional rats, computed tomography (CT) images were obtained at each time point. Ventilation with ZEEP decreased total lung gas volume and increased both FV and ADC in all studied regions. Increases in FV were more evident in the dorsal slices. In each lung quadrant, higher ADC was predicted by lower gas volume and by increased mean values (and heterogeneity) of FV distribution. CT scans documented 10% loss of whole-lung aeration and increased density in the dorsal lung, but no macroscopic atelectasis. Loss of pulmonary gas at ZEEP increased fractional ventilation and inspiratory dimensions of ventilated peripheral air spaces. Such regional changes could help explain a propensity for mechanical ventilation to contribute to lung injury in previously uninjured lungs.
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Affiliation(s)
- Maurizio Cereda
- Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, Pennsylvania;
| | - Yi Xin
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania; and
| | - Hooman Hamedani
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania; and
| | - Justin Clapp
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania; and
| | - Stephen Kadlecek
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania; and
| | - Natalie Meeder
- Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Johnathan Zeng
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania; and
| | - Harrilla Profka
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania; and
| | - Brian P Kavanagh
- Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Rahim R Rizi
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania; and
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21
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Bayat S, Porra L, Broche L, Albu G, Malaspinas I, Doras C, Strengell S, Peták F, Habre W. Effect of surfactant on regional lung function in an experimental model of respiratory distress syndrome in rabbit. J Appl Physiol (1985) 2015; 119:290-8. [DOI: 10.1152/japplphysiol.00047.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 05/14/2015] [Indexed: 11/22/2022] Open
Abstract
We assessed the changes in regional lung function following instillation of surfactant in a model of respiratory distress syndrome (RDS) induced by whole lung lavage and mechanical ventilation in eight anaesthetized, paralyzed, and mechanically ventilated New Zealand White rabbits. Regional specific ventilation (sV̇) was measured by K-edge subtraction synchrotron computed tomography during xenon washin. Lung regions were classified as poorly aerated (PA), normally aerated (NA), or hyperinflated (HI) based on regional density. A functional category was defined within each class based on sV̇ distribution (High, Normal, and Low). Airway resistance (Raw), respiratory tissue damping (G), and elastance (H) were measured by forced oscillation technique at low frequencies before and after whole lung saline lavage-induced (100 ml/kg) RDS, and 5 and 45 min after intratracheal instillation of beractant (75 mg/kg). Surfactant instillation improved Raw, G, and H ( P < 0.05 each), and gas exchange and decreased atelectasis ( P < 0.001). It also significantly improved lung aeration and ventilation in atelectatic lung regions. However, in regions that had remained normally aerated after lavage, it decreased regional aeration and increased sV̇ ( P < 0.001) and sV̇ heterogeneity. Although surfactant treatment improved both central airway and tissue mechanics and improved regional lung function of initially poorly aerated and atelectatic lung, it deteriorated regional lung function when local aeration was normal prior to administration. Local mechanical and functional heterogeneity can potentially contribute to the worsening of RDS and gas exchange. These data underscore the need for reassessing the benefits of routine prophylactic vs. continuous positive airway pressure and early “rescue” surfactant therapy in very immature infants.
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Affiliation(s)
- Sam Bayat
- Université de Picardie Jules Verne, Inserm U1105 and Pediatric Lung Function Laboratory, Amiens University Hospital, Amiens, France
| | - Liisa Porra
- Department of Physics, University of Helsinki, and Helsinki University Central Hospital, Helsinki, Finland
| | - Ludovic Broche
- Université de Picardie Jules Verne, Inserm U1105 and Pediatric Lung Function Laboratory, Amiens University Hospital, Amiens, France
- European Synchrotron Radiation Facility, Biomedical Beamline-ID17, Grenoble, France
| | - Gergely Albu
- Anesthesiological Investigation Unit, University of Geneva, Geneva, Switzerland
| | - Iliona Malaspinas
- Anesthesiological Investigation Unit, University of Geneva, Geneva, Switzerland
| | - Camille Doras
- Anesthesiological Investigation Unit, University of Geneva, Geneva, Switzerland
| | - Satu Strengell
- Department of Physics, University of Helsinki, and Helsinki University Central Hospital, Helsinki, Finland
| | - Ferenc Peták
- Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary; and
| | - Walid Habre
- Anesthesiological Investigation Unit, University of Geneva, Geneva, Switzerland
- Geneva Children's Hospital, University Hospitals of Geneva and Geneva University, Geneva, Switzerland
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22
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Doras C, Le Guen M, Peták F, Habre W. Cardiorespiratory effects of recruitment maneuvers and positive end expiratory pressure in an experimental context of acute lung injury and pulmonary hypertension. BMC Pulm Med 2015; 15:82. [PMID: 26228052 PMCID: PMC4521467 DOI: 10.1186/s12890-015-0079-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 07/20/2015] [Indexed: 01/17/2023] Open
Abstract
Background Recruitment maneuvers (RM) and positive end expiratory pressure (PEEP) are the cornerstone of the open lung strategy during ventilation, particularly during acute lung injury (ALI). However, these interventions may impact the pulmonary circulation and induce hemodynamic and respiratory effects, which in turn may be critical in case of pulmonary hypertension (PHT). We aimed to establish how ALI and PHT influence the cardiorespiratory effects of RM and PEEP. Methods Rabbits control or with monocrotaline-induced PHT were used. Forced oscillatory airway and tissue mechanics, effective lung volume (ELV), systemic and right ventricular hemodynamics and blood gas were assessed before and after RM, during baseline and following surfactant depletion by whole lung lavage. Results RM was more efficient in improving respiratory elastance and ELV in the surfactant-depleted lungs when PHT was concomitantly present. Moreover, the adverse changes in respiratory mechanics and ELV following ALI were lessened in the animals suffering from PHT. Conclusions During ventilation with open lung strategy, the role of PHT in conferring protection from the adverse respiratory consequences of ALI was evidenced. This finding advocates the safety of RM and PEEP in improving elastance and advancing lung reopening in the simultaneous presence of PHT and ALI.
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Affiliation(s)
- Camille Doras
- Anesthesiological Investigation, University Medical Centre, University of Geneva, Geneva, Switzerland.
| | - Morgan Le Guen
- Department of Anesthesiology, Hospital Foch, University Versailles Saint-Quentin en Yvelines, Suresnes, France.
| | - Ferenc Peták
- Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary.
| | - Walid Habre
- Anesthesiological Investigation, University Medical Centre, University of Geneva, Geneva, Switzerland. .,Pediatric Anesthesia Unit, Geneva Children's Hospital, Rue Willy Donzé 6, 1205, Geneva, Switzerland.
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23
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Relationship between surfactant proteins B and C and obstructive sleep apnea: is serum SP-B concentration a potential biomarker of obstructive sleep apnea? Sleep Breath 2015; 20:25-31. [DOI: 10.1007/s11325-015-1179-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 03/25/2015] [Accepted: 04/06/2015] [Indexed: 11/26/2022]
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24
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Cereda M, Xin Y, Kadlecek S, Hamedani H, Rajaei J, Clapp J, Rizi RR. Hyperpolarized gas diffusion MRI for the study of atelectasis and acute respiratory distress syndrome. NMR IN BIOMEDICINE 2014; 27:1468-78. [PMID: 24920074 PMCID: PMC4232982 DOI: 10.1002/nbm.3136] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 04/03/2014] [Accepted: 04/21/2014] [Indexed: 06/03/2023]
Abstract
Considerable uncertainty remains about the best ventilator strategies for the mitigation of atelectasis and associated airspace stretch in patients with acute respiratory distress syndrome (ARDS). In addition to several immediate physiological effects, atelectasis increases the risk of ventilator-associated lung injury, which has been shown to significantly worsen ARDS outcomes. A number of lung imaging techniques have made substantial headway in clarifying the mechanisms of atelectasis. This paper reviews the contributions of computed tomography, positron emission tomography, and conventional MRI to understanding this phenomenon. In doing so, it also reveals several important shortcomings inherent to each of these approaches. Once these shortcomings have been made apparent, we describe how hyperpolarized (HP) gas MRI--a technique that is uniquely able to assess responses to mechanical ventilation and lung injury in peripheral airspaces--is poised to fill several of these knowledge gaps. The HP-MRI-derived apparent diffusion coefficient (ADC) quantifies the restriction of (3) He diffusion by peripheral airspaces, thereby obtaining pulmonary structural information at an extremely small scale. Lastly, this paper reports the results of a series of experiments that measured ADC in mechanically ventilated rats in order to investigate (i) the effect of atelectasis on ventilated airspaces, (ii) the relationship between positive end-expiratory pressure (PEEP), hysteresis, and the dimensions of peripheral airspaces, and (iii) the ability of PEEP and surfactant to reduce airspace dimensions after lung injury. An increase in ADC was found to be a marker of atelectasis-induced overdistension. With recruitment, higher airway pressures were shown to reduce stretch rather than worsen it. Moving forward, HP MRI has significant potential to shed further light on the atelectatic processes that occur during mechanical ventilation.
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Affiliation(s)
- Maurizio Cereda
- Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, PA, USA
| | - Yi Xin
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Stephen Kadlecek
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Hooman Hamedani
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Jennia Rajaei
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Justin Clapp
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Rahim R. Rizi
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
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25
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Strengell S, Keyriläinen J, Suortti P, Bayat S, Sovijärvi ARA, Porra L. Radiation dose and image quality in K-edge subtraction computed tomography of lung in vivo. JOURNAL OF SYNCHROTRON RADIATION 2014; 21:1305-1313. [PMID: 25343799 DOI: 10.1107/s160057751401697x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 07/23/2014] [Indexed: 06/04/2023]
Abstract
K-edge subtraction computed tomography (KES-CT) allows simultaneous imaging of both structural features and regional distribution of contrast elements inside an organ. Using this technique, regional lung ventilation and blood volume distributions can be measured experimentally in vivo. In order for this imaging technology to be applicable in humans, it is crucial to minimize exposure to ionizing radiation with little compromise in image quality. The goal of this study was to assess the changes in signal-to-noise ratio (SNR) of KES-CT lung images as a function of radiation dose. The experiments were performed in anesthetized and ventilated rabbits using inhaled xenon gas in O2 at two concentrations: 20% and 70%. Radiation dose, defined as air kerma (Ka), was measured free-in-air and in a 16 cm polymethyl methacrylate phantom with a cylindrical ionization chamber. The dose free-in-air was varied from 2.7 mGy to 8.0 Gy. SNR in the images of xenon in air spaces was above the Rose criterion (SNR > 5) when Ka was over 400 mGy with 20% xenon, and over 40 mGy with 70% xenon. Although in human thorax attenuation is higher, based on these findings it is estimated that, by optimizing the imaging sequence and reconstruction algorithms, the radiation dose could be further reduced to clinically acceptable levels.
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Affiliation(s)
- S Strengell
- Department of Physics, University of Helsinki, Helsinki 00370, Finland
| | - J Keyriläinen
- Department of Oncology, Helsinki University Central Hospital, Helsinki, Finland
| | - P Suortti
- Department of Physics, University of Helsinki, Helsinki 00370, Finland
| | - S Bayat
- Université de Picardie Jules Verne, Inserm U1105 and CHU Amiens, France
| | - A R A Sovijärvi
- Department of Clinical Physiology and Nuclear Medicine, Helsinki University Central Hospital, Helsinki, Finland
| | - L Porra
- Department of Physics, University of Helsinki, Helsinki 00370, Finland
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26
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Albu G, Petak F, Zand T, Hallbäck M, Wallin M, Habre W. Lung volume assessments in normal and surfactant depleted lungs: agreement between bedside techniques and CT imaging. BMC Anesthesiol 2014; 14:64. [PMID: 25143759 PMCID: PMC4134664 DOI: 10.1186/1471-2253-14-64] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Accepted: 07/01/2014] [Indexed: 01/17/2023] Open
Abstract
Background Bedside assessment of lung volume in clinical practice is crucial to adapt ventilation strategy. We compared bedside measures of lung volume by helium multiple-breath washout technique (EELVMBW,He) and effective lung volume based on capnodynamics (ELV) to those assessed from spiral chest CT scans (EELVCT) under different PEEP levels in control and surfactant-depleted lungs. Methods Lung volume was assessed in anaesthetized mechanically ventilated rabbits successively by measuring i) ELV by analyzing CO2 elimination traces during the application of periods of 5 consecutive alterations in inspiratory/expiratory ratio (1:2 to 1.5:1), ii) measuring EELVMBW,He by using helium as a tracer gas, and iii) EELVCT from CT scan images by computing the normalized lung density. All measurements were performed at PEEP of 0, 3 and 9 cmH2O in random order under control condition and following surfactant depletion by whole lung lavage. Results Variables obtained with all techniques followed sensitively the lung volume changes with PEEP. Excellent correlation and close agreement was observed between EELVMBW,He and EELVCT (r = 0.93, p < 0.0001). ELV overestimated EELVMBW,He and EELVCT in normal lungs, whereas this difference was not evidenced following surfactant depletion. These findings resulted in somewhat diminished but still significant correlations between ELV and EELVCT (r = 0.58, p < 0.001) or EELVMBW,He (0.76, p < 0.001) and moderate agreements. Conclusions Lung volume assessed with bedside techniques allow the monitoring of the changes in the lung aeration with PEEP both in normal lungs and in a model of acute lung injury. Under stable pulmonary haemodynamic condition, ELV allows continuous lung volume monitoring, whereas EELVMBW,He offers a more accurate estimation, but intermittently.
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Affiliation(s)
- Gergely Albu
- Pathophysiological Experimental Platform, Department of Anaesthesiology, Pharmacology and Intensive Care, University of Geneva, 1 Rue Michel Servet, CH-1205 Geneva, Switzerland
| | - Ferenc Petak
- Department of Medical Physics and Informatics, University of Szeged, 9 Koranyi fasor, H-6720 Szeged, Hungary
| | - Tristan Zand
- Paediatric Radiology Unit, Department of Radiology and Nuclear Medicine, University Hospitals of Geneva, 6 rue Willy Donzé, CH-1205 Geneva, Switzerland
| | - Magnus Hallbäck
- Maquet Critical Care AB, Röntgenvägen 2, 17154 Solna, Sweden
| | - Mats Wallin
- Maquet Critical Care AB, Röntgenvägen 2, 17154 Solna, Sweden
| | - Walid Habre
- Pathophysiological Experimental Platform, Department of Anaesthesiology, Pharmacology and Intensive Care, University of Geneva, 1 Rue Michel Servet, CH-1205 Geneva, Switzerland ; Paediatric Anaesthesia Unit, Geneva Children's Hospital, University Hospitals of Geneva, 6, Rue Willy Donzé, CH-1205 Geneva, Switzerland
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In Reply. Anesthesiology 2014; 120:779-80. [DOI: 10.1097/aln.0000000000000105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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