1
|
Grune J, Tabuchi A, Kuebler WM. Alveolar dynamics during mechanical ventilation in the healthy and injured lung. Intensive Care Med Exp 2019; 7:34. [PMID: 31346797 PMCID: PMC6658629 DOI: 10.1186/s40635-019-0226-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 02/13/2019] [Indexed: 02/12/2023] Open
Abstract
Mechanical ventilation is a life-saving therapy in patients with acute respiratory distress syndrome (ARDS). However, mechanical ventilation itself causes severe co-morbidities in that it can trigger ventilator-associated lung injury (VALI) in humans or ventilator-induced lung injury (VILI) in experimental animal models. Therefore, optimization of ventilation strategies is paramount for the effective therapy of critical care patients. A major problem in the stratification of critical care patients for personalized ventilation settings, but even more so for our overall understanding of VILI, lies in our limited insight into the effects of mechanical ventilation at the actual site of injury, i.e., the alveolar unit. Unfortunately, global lung mechanics provide for a poor surrogate of alveolar dynamics and methods for the in-depth analysis of alveolar dynamics on the level of individual alveoli are sparse and afflicted by important limitations. With alveolar dynamics in the intact lung remaining largely a "black box," our insight into the mechanisms of VALI and VILI and the effectiveness of optimized ventilation strategies is confined to indirect parameters and endpoints of lung injury and mortality.In the present review, we discuss emerging concepts of alveolar dynamics including alveolar expansion/contraction, stability/instability, and opening/collapse. Many of these concepts remain still controversial, in part due to limitations of the different methodologies applied. We therefore preface our review with an overview of existing technologies and approaches for the analysis of alveolar dynamics, highlighting their individual strengths and limitations which may provide for a better appreciation of the sometimes diverging findings and interpretations. Joint efforts combining key technologies in identical models to overcome the limitations inherent to individual methodologies are needed not only to provide conclusive insights into lung physiology and alveolar dynamics, but ultimately to guide critical care patient therapy.
Collapse
Affiliation(s)
- Jana Grune
- Institute of Physiology, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
- DZHK (German Centre for Cardiovascular Research), partner site Berlin, 10117 Berlin, Germany
| | - Arata Tabuchi
- Institute of Physiology, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Wolfgang M. Kuebler
- Institute of Physiology, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
- DZHK (German Centre for Cardiovascular Research), partner site Berlin, 10117 Berlin, Germany
- The Keenan Research Centre for Biomedical Science at St. Michael’s, Toronto, Canada
- Departments of Surgery and Physiology, University of Toronto, Toronto, Canada
| |
Collapse
|
2
|
Airflow and Particle Deposition in Acinar Models with Interalveolar Septal Walls and Different Alveolar Numbers. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2018; 2018:3649391. [PMID: 30356402 PMCID: PMC6176334 DOI: 10.1155/2018/3649391] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 08/27/2018] [Indexed: 11/17/2022]
Abstract
Unique features exist in acinar units such as multiple alveoli, interalveolar septal walls, and pores of Kohn. However, the effects of such features on airflow and particle deposition remain not well quantified due to their structural complexity. This study aims to numerically investigate particle dynamics in acinar models with interalveolar septal walls and pores of Kohn. A simplified 4-alveoli model with well-defined geometries and a physiologically realistic 45-alveoli model was developed. A well-validated Lagrangian tracking model was used to simulate particle trajectories in the acinar models with rhythmically expanding and contracting wall motions. Both spatial and temporal dosimetries in the acinar models were analyzed. Results show that collateral ventilation exists among alveoli due to pressure imbalance. The size of interalveolar septal aperture significantly alters the spatial deposition pattern, while it has an insignificant effect on the total deposition rate. Surprisingly, the deposition rate in the 45-alveoli model is lower than that in the 4-alveoli model, indicating a stronger particle dispersion in more complex models. The gravity orientation angle has a decreasing effect on acinar deposition rates with an increasing number of alveoli retained in the model; such an effect is nearly negligible in the 45-alveoli model. Breath-holding increased particle deposition in the acinar region, which was most significant in the alveoli proximal to the duct. Increasing inhalation depth only slightly increases the fraction of deposited particles over particles entering the alveolar model but has a large influence on dispensing particles to the peripheral alveoli. Results of this study indicate that an empirical correlation for acinar deposition can be developed based on alveolar models with reduced complexity; however, what level of geometry complexity would be sufficient is yet to be determined.
Collapse
|
3
|
Xi J, Talaat K, Si XA. Deposition of bolus and continuously inhaled aerosols in rhythmically moving terminal alveoli. ACTA ACUST UNITED AC 2018. [DOI: 10.1177/1757482x18791891] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The particle dynamics in an oscillating alveolus under tidal breathing can be dramatically different from those in a static alveolus. Despite its close relevance to pulmonary drug delivery and health risk from airborne exposure, quantifications of alveolar deposition are scarce due to its inaccessibility to in vivo measurement instruments, tiny size to replicate in vitro, and dynamic wall motions to model. The objective of this study is to introduce a numerical method to quantify alveolar deposition with continuous particle release in a rhythmically oscillating alveolus by integrating the deposition curves for bolus aerosols and use this method to develop correlations applicable in assessing alveolar drug delivery efficiency or dosimetry of inhaled toxicants. An idealized blind-end terminal alveolus model was developed with rhythmically moving alveolar boundary conditions in phase with tidal breathing. The dynamic wall expansion mode and magnitude were based on experimentally measured chest wall motions and tidal volumes. A well-validated Lagrangian tracking model was used to simulate the transport and deposition of inhaled micrometer particles. Large differences were observed between dynamic and static alveoli in particle motion, deposition onset, and final alveolar deposition fraction. Alveolar deposition of bolus aerosols is highly sensitive to breath-holding duration, particle release time, and alveolar dimension. For 1 µm particles, there exists a cut-off release time (zero bolus deposition), which decreases with alveolar size (i.e., 1.0 s in a 0.2-mm-diameter alveolus and 0.56 s in a 0.8-mm-diameter alveolus). The cumulative alveolar deposition was predicted to be 39% for a 0.2-mm-diameter alveolus, 22% for a 0.4-mm-diameter alveolus, and 10% for a 0.8-mm-diameter alveolus. A cumulative alveolar deposition correlation was developed for inhalation delivery with a prescribed period of drug release and the second correlation for the time variation of alveolar deposition of ambient aerosols, both of which captured the relative dependence of the particle release time and alveolar dimension.
Collapse
Affiliation(s)
- Jinxiang Xi
- Department of Mechanical and Biomedical Engineering, California Baptist University, Riverside, CA, USA
| | - Khaled Talaat
- Department of Nuclear Engineering, The University of New Mexico, Albuquerque, NM, USA
| | - Xiuhua April Si
- Department of Mechanical and Biomedical Engineering, California Baptist University, Riverside, CA, USA
| |
Collapse
|
4
|
Lizal F, Jedelsky J, Morgan K, Bauer K, Llop J, Cossio U, Kassinos S, Verbanck S, Ruiz-Cabello J, Santos A, Koch E, Schnabel C. Experimental methods for flow and aerosol measurements in human airways and their replicas. Eur J Pharm Sci 2018; 113:95-131. [DOI: 10.1016/j.ejps.2017.08.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 08/14/2017] [Accepted: 08/17/2017] [Indexed: 12/29/2022]
|
5
|
Schnabel C, Jannasch A, Faak S, Waldow T, Koch E. Ex vivo 4D visualization of aortic valve dynamics in a murine model with optical coherence tomography. BIOMEDICAL OPTICS EXPRESS 2014; 5:4201-12. [PMID: 25574432 PMCID: PMC4285599 DOI: 10.1364/boe.5.004201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 10/24/2014] [Accepted: 10/24/2014] [Indexed: 05/03/2023]
Abstract
The heart and its mechanical components, especially the heart valves and leaflets, are under enormous strain and undergo fatigue, which impinge upon cardiac output. The knowledge about changes of the dynamic behavior and the possibility of early stage diagnosis could lead to the development of new treatment strategies. Animal models are suited for the development and evaluation of new experimental approaches and therefor innovative imaging techniques are necessary. In this study, we present the time resolved visualization of healthy and calcified aortic valves in an ex vivo artificially stimulated heart model with 4D optical coherence tomography and high-speed video microscopy.
Collapse
Affiliation(s)
- Christian Schnabel
- Technische Universität Dresden, Faculty of Medicine CGC, Department of Anesthesiology and Intensive Care Medicine and Clinical Sensoring and Monitoring, Germany ; Authors contributed equally to this paper
| | - Anett Jannasch
- Technische Universität Dresden, Faculty of Medicine CGC, Clinic for Cardiac Surgery, Germany ; Authors contributed equally to this paper
| | - Saskia Faak
- Technische Universität Dresden, Faculty of Medicine CGC, Department of Anesthesiology and Intensive Care Medicine and Clinical Sensoring and Monitoring, Germany ; Technische Universität Dresden, Faculty of Medicine CGC, Clinic for Cardiac Surgery, Germany ; Authors contributed equally to this paper
| | - Thomas Waldow
- Technische Universität Dresden, Faculty of Medicine CGC, Clinic for Cardiac Surgery, Germany
| | - Edmund Koch
- Technische Universität Dresden, Faculty of Medicine CGC, Department of Anesthesiology and Intensive Care Medicine and Clinical Sensoring and Monitoring, Germany
| |
Collapse
|
6
|
Burkhardt A, Kirsten L, Bornitz M, Zahnert T, Koch E. Investigation of the human tympanic membrane oscillation ex vivo by Doppler optical coherence tomography. JOURNAL OF BIOPHOTONICS 2014; 7:434-41. [PMID: 23225692 DOI: 10.1002/jbio.201200186] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Revised: 10/23/2012] [Accepted: 11/20/2012] [Indexed: 05/03/2023]
Abstract
Investigations of the tympanic membrane (TM) can have an important impact on understanding the sound conduction in the ear and can therefore support the diagnosis and treatment of diseases in the middle ear. High-speed Doppler optical coherence tomography (OCT) has the potential to describe the oscillatory behaviour of the TM surface in a phase-sensitive manner and additionally allows acquiring a three-dimensional image of the underlying structure. With repeated sound stimuli from 0.4 kHz to 6.4 kHz, the whole TM can be set in vibration and the spatially resolved frequency response functions (FRFs) of the tympanic membrane can be recorded. Typical points, such as the umbo or the manubrium of malleus, can be studied separately as well as the TM surface with all stationary and wave-like vibrations. Thus, the OCT methodology can be a promising technique to distinguish between normal and pathological TMs and support the differentiation between ossicular and membrane diseases.
Collapse
Affiliation(s)
- Anke Burkhardt
- Dresden University of Technology, Faculty of Medicine Carl Gustav Carus, Department Clinical Sensoring and Monitoring, Fetscherstraße 74, 01307 Dresden, Germany.
| | | | | | | | | |
Collapse
|
7
|
Namati E, Warger WC, Unglert CI, Eckert JE, Hostens J, Bouma BE, Tearney GJ. Four-dimensional visualization of subpleural alveolar dynamics in vivo during uninterrupted mechanical ventilation of living swine. BIOMEDICAL OPTICS EXPRESS 2013; 4:2492-506. [PMID: 24298409 PMCID: PMC3829543 DOI: 10.1364/boe.4.002492] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 08/24/2013] [Accepted: 08/28/2013] [Indexed: 05/04/2023]
Abstract
Pulmonary alveoli have been studied for many years, yet no unifying hypothesis exists for their dynamic mechanics during respiration due to their miniature size (100-300 μm dimater in humans) and constant motion, which prevent standard imaging techniques from visualizing four-dimensional dynamics of individual alveoli in vivo. Here we report a new platform to image the first layer of air-filled subpleural alveoli through the use of a lightweight optical frequency domain imaging (OFDI) probe that can be placed upon the pleura to move with the lung over the complete range of respiratory motion. This device enables in-vivo acquisition of four-dimensional microscopic images of alveolar airspaces (alveoli and ducts), within the same field of view, during continuous ventilation without restricting the motion or modifying the structure of the alveoli. Results from an exploratory study including three live swine suggest that subpleural alveolar air spaces are best fit with a uniform expansion (r (2) = 0.98) over a recruitment model (r (2) = 0.72). Simultaneously, however, the percentage change in volume shows heterogeneous alveolar expansion within just a 1 mm x 1 mm field of view. These results signify the importance of four-dimensional imaging tools, such as the device presented here. Quantification of the dynamic response of the lung during ventilation may help create more accurate modeling techniques and move toward a more complete understanding of alveolar mechanics.
Collapse
Affiliation(s)
- Eman Namati
- Harvard Medical School and Massachusetts General Hospital, Wellman Center for Photomedicine, 40 Blossom St., BAR-714, Boston, MA 02114 USA
- Co-first authors. These authors contributed equally to this work
| | - William C. Warger
- Harvard Medical School and Massachusetts General Hospital, Wellman Center for Photomedicine, 40 Blossom St., BAR-714, Boston, MA 02114 USA
- Co-first authors. These authors contributed equally to this work
| | - Carolin I. Unglert
- Harvard Medical School and Massachusetts General Hospital, Wellman Center for Photomedicine, 40 Blossom St., BAR-714, Boston, MA 02114 USA
- Air Liquide Centre de Recherche Claude-Delorme, Medical Gases Group, 1 Chemin de la Porte des Loges, Les-Loges-en-Josas, France
| | - Jocelyn E. Eckert
- Harvard Medical School and Massachusetts General Hospital, Wellman Center for Photomedicine, 40 Blossom St., BAR-714, Boston, MA 02114 USA
| | | | - Brett E. Bouma
- Harvard Medical School and Massachusetts General Hospital, Wellman Center for Photomedicine, 40 Blossom St., BAR-714, Boston, MA 02114 USA
- Harvard-MIT Division of Health Sciences and Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 USA
| | - Guillermo J. Tearney
- Harvard Medical School and Massachusetts General Hospital, Wellman Center for Photomedicine, 40 Blossom St., BAR-714, Boston, MA 02114 USA
- Harvard-MIT Division of Health Sciences and Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 USA
- Department of Pathology, Massachusetts General Hospital, Boston, MA 02114 USA
| |
Collapse
|
8
|
Schneider C, Kirsten L, Meissner S, Hurtado A, Koch E, Hampel R. Small scale boiling experiments using two-dimensional imaging with high-speed camera and optical coherence tomography. KERNTECHNIK 2013. [DOI: 10.3139/124.110314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
To investigate boiling processes, a test facility has been constructed, which allows the use of optical techniques for the detection of individual vapor bubbles. Demineralized water was used as working fluid at ambient pressure whereat temperature, flow rate and heat flux density can be varied. The growth of individual vapor bubbles was recorded by high-speed camera and analyzed by digital image processing (DIP). Optical coherence tomography (OCT) enabled the visualization of steam bubbles in cross-sections perpendicular to the heated surface.
Collapse
Affiliation(s)
- C. Schneider
- University of Applied Sciences Zittau/Görlitz, Institute of Process Technology, Process Automation and Measuring Technology (IPM), Theodor-Koerner-Allee 16, 02763 Zittau
| | - L. Kirsten
- Dipl.-Phys. Lars Kirsten, E-mail:
- Dresden University of Technology, Faculty of Medicine Carl Gustav Carus, Clinical Sensoring and Monitoring, Fetscherstraße 74, 01307 Dresden
| | - S. Meissner
- Dr. rer. medic. Dipl.-Ing. (FH) Sven Meissner, E-mail:
- Dresden University of Technology, Faculty of Medicine Carl Gustav Carus, Clinical Sensoring and Monitoring, Fetscherstraße 74, 01307 Dresden
| | - A. Hurtado
- Prof. Dr.-Ing. habil. Antonio Hurtado, E-mail: , Dresden University of Technology, Faculty of Mechanical Engineering, Chair of hydrogen and nuclear energy technology, George-Bähr-Straße 3b, 01069 Dresden
| | - E. Koch
- Prof. Dr. rer. nat. Edmund Koch, E-mail:
- Dresden University of Technology, Faculty of Medicine Carl Gustav Carus, Clinical Sensoring and Monitoring, Fetscherstraße 74, 01307 Dresden
| | - R. Hampel
- Prof. Dr.-Ing. habil. Rainer Hampel, E-mail:
- University of Applied Sciences Zittau/Görlitz, Institute of Process Technology, Process Automation and Measuring Technology (IPM), Theodor-Koerner-Allee 16, 02763 Zittau
| |
Collapse
|
9
|
Unglert CI, Warger WC, Hostens J, Namati E, Birngruber R, Bouma BE, Tearney GJ. Validation of two-dimensional and three-dimensional measurements of subpleural alveolar size parameters by optical coherence tomography. JOURNAL OF BIOMEDICAL OPTICS 2012; 17:126015. [PMID: 23235834 PMCID: PMC3519489 DOI: 10.1117/1.jbo.17.12.126015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Optical coherence tomography (OCT) has been increasingly used for imaging pulmonary alveoli. Only a few studies, however, have quantified individual alveolar areas, and the validity of alveolar volumes represented within OCT images has not been shown. To validate quantitative measurements of alveoli from OCT images, we compared the cross-sectional area, perimeter, volume, and surface area of matched subpleural alveoli from microcomputed tomography (micro-CT) and OCT images of fixed air-filled swine samples. The relative change in size between different alveoli was extremely well correlated (r>0.9, P<0.0001), but OCT images underestimated absolute sizes compared to micro-CT by 27% (area), 7% (perimeter), 46% (volume), and 25% (surface area) on average. We hypothesized that the differences resulted from refraction at the tissue-air interfaces and developed a ray-tracing model that approximates the reconstructed alveolar size within OCT images. Using this model and OCT measurements of the refractive index for lung tissue (1.41 for fresh, 1.53 for fixed), we derived equations to obtain absolute size measurements of superellipse and circular alveoli with the use of predictive correction factors. These methods and results should enable the quantification of alveolar sizes from OCT images in vivo.
Collapse
Affiliation(s)
- Carolin I Unglert
- Harvard Medical School and Massachusetts General Hospital, Wellman Center for Photomedicine, 40 Parkman Street, RSL 160, Boston, Massachusetts 02114, USA.
| | | | | | | | | | | | | |
Collapse
|
10
|
Tschernig T, Thrane L, Jørgensen TM, Thommes J, Pabst R, Yelbuz TM. An elegant technique for ex vivo imaging in experimental research-Optical coherence tomography (OCT). Ann Anat 2012; 195:25-7. [PMID: 22947371 DOI: 10.1016/j.aanat.2012.07.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 06/26/2012] [Accepted: 07/18/2012] [Indexed: 11/16/2022]
Abstract
Optical coherence tomography (OCT) is an elegant technology for imaging of tissues and organs and has been established for clinical use for around a decade. Thus, it is used in vivo but can also serve as a valuable ex vivo imaging tool in experimental research. Here, a brief overview is given with a focus on an ex vivo application of OCT. Image and video examples of freshly obtained murine lungs are included. The main advantage of OCT for ex vivo analysis is the non-contact, non-invasive, and non-destructive fast acquisition of a three-dimensional data set with micrometer-resolution.
Collapse
Affiliation(s)
- T Tschernig
- Institute of Anatomy and Cell Biology, Saarland University, Homburg, Saar, Germany.
| | | | | | | | | | | |
Collapse
|
11
|
Gaertner M, Cimalla P, Meissner S, Kuebler WM, Koch E. Three-dimensional simultaneous optical coherence tomography and confocal fluorescence microscopy for investigation of lung tissue. JOURNAL OF BIOMEDICAL OPTICS 2012; 17:071310. [PMID: 22894471 DOI: 10.1117/1.jbo.17.7.071310] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Although several strategies exist for a minimal-invasive treatment of patients with lung failure, the mortality rate of acute respiratory distress syndrome still reaches 30% at minimum. This striking number indicates the necessity of understanding lung dynamics on an alveolar level. To investigate the dynamical behavior on a microscale, we used three-dimensional geometrical and functional imaging to observe tissue parameters including alveolar size and length of embedded elastic fibers during ventilation. We established a combined optical coherence tomography (OCT) and confocal fluorescence microscopy system that is able to monitor the distension of alveolar tissue and elastin fibers simultaneously within three dimensions. The OCT system can laterally resolve a 4.9 μm line pair feature and has an approximately 11 μm full-width-half-maximum axial resolution in air. confocal fluorescence microscopy visualizes molecular properties of the tissue with a resolution of 0.75 μm (laterally), and 5.9 μm (axially) via fluorescence detection of the dye sulforhodamine B specifically binding to elastin. For system evaluation, we used a mouse model in situ to perform lung distension by application of different constant pressure values within the physiological regime. Our method enables the investigation of alveolar dynamics by helping to reveal basic processes emerging during artificial ventilation and breathing.
Collapse
Affiliation(s)
- Maria Gaertner
- Dresden University of Technology, Clinical Sensoring and Monitoring, Faculty of Medicine Carl Gustav Carus, Fetscherstrasse 74, 01307 Dresden, Germany
| | | | | | | | | |
Collapse
|