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Gaertner VD, Waldmann AD, Davis PG, Bassler D, Springer L, Thomson J, Tingay DG, Rüegger CM. Lung volume distribution in preterm infants on non-invasive high-frequency ventilation. Arch Dis Child Fetal Neonatal Ed 2022; 107:551-557. [PMID: 35101993 DOI: 10.1136/archdischild-2021-322990] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 01/12/2022] [Indexed: 11/04/2022]
Abstract
INTRODUCTION Non-invasive high-frequency oscillatory ventilation (nHFOV) is an extension of nasal continuous positive airway pressure (nCPAP) support in neonates. We aimed to compare global and regional distribution of lung volumes during nHFOV versus nCPAP. METHODS In 30 preterm infants enrolled in a randomised crossover trial comparing nHFOV with nCPAP, electrical impedance tomography data were recorded in prone position. For each mode of respiratory support, four episodes of artefact-free tidal ventilation, each comprising 30 consecutive breaths, were extracted. Tidal volumes (VT) in 36 horizontal slices, indicators of ventilation homogeneity and end-expiratory lung impedance (EELI) for the whole lung and for four horizontal regions of interest (non-gravity-dependent to gravity-dependent; EELINGD, EELImidNGD, EELImidGD, EELIGD) were compared between nHFOV and nCPAP. Aeration homogeneity ratio (AHR) was determined by dividing aeration in non-gravity-dependent parts of the lung through gravity-dependent regions. MAIN RESULTS Overall, 228 recordings were analysed. Relative VT was greater in all but the six most gravity-dependent lung slices during nCPAP (all p<0.05). Indicators of ventilation homogeneity were similar between nHFOV and nCPAP (all p>0.05). Aeration was increased during nHFOV (mean difference (95% CI)=0.4 (0.2 to 0.6) arbitrary units per kilogram (AU/kg), p=0.013), mainly due to an increase in non-gravity-dependent regions of the lung (∆EELINGD=6.9 (0.0 to 13.8) AU/kg, p=0.028; ∆EELImidNGD=6.8 (1.2 to 12.4) AU/kg, p=0.009). Aeration was more homogeneous during nHFOV compared with nCPAP (mean difference (95% CI) in AHR=0.01 (0.00 to 0.02), p=0.0014). CONCLUSION Although regional ventilation was similar between nHFOV and nCPAP, end-expiratory lung volume was higher and aeration homogeneity was slightly improved during nHFOV. The aeration difference was greatest in non-gravity dependent regions, possibly due to the oscillatory pressure waveform. The clinical importance of these findings is still unclear.
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Affiliation(s)
- Vincent D Gaertner
- Newborn Research, Department of Neonatology, University Hospital and University of Zurich, Zurich, Switzerland
| | - Andreas D Waldmann
- Department of Anesthesiology and Intensive Care Medicine, Rostock University Medical Center, Rostock, Germany
| | - Peter G Davis
- Newborn Research Centre and Neonatal Services, The Royal Women's Hospital, Melbourne, Victoria, Australia.,Murdoch Children's Research Institute, Melbourne, Victoria, Australia.,University of Melbourne, Melbourne, Victoria, Australia
| | - Dirk Bassler
- Newborn Research, Department of Neonatology, University Hospital and University of Zurich, Zurich, Switzerland
| | - Laila Springer
- Department of Neonatology, University Children's Hospital Tubingen, Tubingen, Germany
| | - Jessica Thomson
- Murdoch Children's Research Institute, Melbourne, Victoria, Australia.,University of Melbourne, Melbourne, Victoria, Australia
| | - David Gerald Tingay
- Murdoch Children's Research Institute, Melbourne, Victoria, Australia.,University of Melbourne, Melbourne, Victoria, Australia.,Department of Neonatology, The Royal Children's Hospital Melbourne, Parkville, Victoria, Australia
| | - Christoph Martin Rüegger
- Newborn Research, Department of Neonatology, University Hospital and University of Zurich, Zurich, Switzerland
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Kramek-Romanowska K, Stecka AM, Zieliński K, Dorosz A, Okrzeja P, Michnikowski M, Odziomek M. Independent Lung Ventilation-Experimental Studies on a 3D Printed Respiratory Tract Model. MATERIALS 2021; 14:ma14185189. [PMID: 34576415 PMCID: PMC8472474 DOI: 10.3390/ma14185189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 08/30/2021] [Accepted: 08/31/2021] [Indexed: 12/04/2022]
Abstract
Independent lung ventilation (ILV) is a life-saving procedure in unilateral pulmonary pathologies. ILV is underused in clinical practice, mostly due to the technically demanding placement of a double lumen endotracheal tube (ETT). Moreover, the determination of ventilation parameters for each lung in vivo is limited. In recent years, the development of 3D printing techniques enabled the production of highly accurate physical models of anatomical structures used for in vitro research, considering the high risk of in vivo studies. The purpose of this study was to assess the influence of double-lumen ETT on the gas transport and mixing in the anatomically accurate 3D-printed model of the bronchial tree, with lung lobes of different compliances, using various ventilation modes. The bronchial tree was obtained from Respiratory Drug Delivery (RDD Online, Richmond, VA, USA), processed and printed by a dual extruder FFF 3D printer. The test system was also composed of left side double-lumen endotracheal tube, Siemens Test Lung 190 and anesthetic breathing bag (as lobes). Pressure and flow measurements were taken at the outlets of the secondary bronchus. The measured resistance increased six times in the presence of double-lumen ETT. Differences between the flow distribution to the less and more compliant lobe were more significant for the airways with double-lumen ETT. The ability to predict the actual flow distribution in model airways is necessary to conduct effective ILV in clinical conditions.
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Affiliation(s)
- Katarzyna Kramek-Romanowska
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Ks Trojdena 4, 02-109 Warsaw, Poland; (A.M.S.); (K.Z.); (P.O.); (M.M.)
- Faculty of Chemical and Process Engineering, Warsaw University of Technology, Waryńskiego 1, 00-645 Warsaw, Poland; (A.D.); (M.O.)
- Correspondence:
| | - Anna M. Stecka
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Ks Trojdena 4, 02-109 Warsaw, Poland; (A.M.S.); (K.Z.); (P.O.); (M.M.)
| | - Krzysztof Zieliński
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Ks Trojdena 4, 02-109 Warsaw, Poland; (A.M.S.); (K.Z.); (P.O.); (M.M.)
| | - Agata Dorosz
- Faculty of Chemical and Process Engineering, Warsaw University of Technology, Waryńskiego 1, 00-645 Warsaw, Poland; (A.D.); (M.O.)
| | - Piotr Okrzeja
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Ks Trojdena 4, 02-109 Warsaw, Poland; (A.M.S.); (K.Z.); (P.O.); (M.M.)
| | - Marcin Michnikowski
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Ks Trojdena 4, 02-109 Warsaw, Poland; (A.M.S.); (K.Z.); (P.O.); (M.M.)
| | - Marcin Odziomek
- Faculty of Chemical and Process Engineering, Warsaw University of Technology, Waryńskiego 1, 00-645 Warsaw, Poland; (A.D.); (M.O.)
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3
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Gaertner VD, Waldmann AD, Davis PG, Bassler D, Springer L, Thomson J, Tingay DG, Rüegger CM. Transmission of Oscillatory Volumes into the Preterm Lung during Noninvasive High-Frequency Ventilation. Am J Respir Crit Care Med 2021; 203:998-1005. [PMID: 33095994 DOI: 10.1164/rccm.202007-2701oc] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Rationale: There is increasing evidence for a clinical benefit of noninvasive high-frequency oscillatory ventilation (nHFOV) in preterm infants. However, it is still unknown whether the generated oscillations are effectively transmitted to the alveoli.Objectives: To assess magnitude and regional distribution of oscillatory volumes (VOsc) at the lung level.Methods: In 30 prone preterm infants enrolled in a randomized crossover trial comparing nHFOV with nasal continuous positive airway pressure, electrical impedance tomography recordings were performed. During nHFOV, the smallest amplitude to achieve visible chest wall vibration was used, and the frequency was set at 8 hertz.Measurements and Main Results: Thirty consecutive breaths during artifact-free tidal ventilation were extracted for each of the 228 electrical impedance tomography recordings. After application of corresponding frequency filters, Vt and VOsc were calculated. There was a signal at 8 and 16 Hz during nHFOV, which was not detectable during nasal continuous positive airway pressure, corresponding to the set oscillatory frequency and its second harmonic. During nHFOV, the mean (SD) VOsc/Vt ratio was 0.20 (0.13). Oscillations were more likely to be transmitted to the non-gravity-dependent (mean difference [95% confidence interval], 0.041 [0.025-0.058]; P < 0.001) and right-sided lung (mean difference [95% confidence interval], 0.040 [0.019-0.061]; P < 0.001) when compared with spontaneous Vt.Conclusions: In preterm infants, VOsc during nHFOV are transmitted to the lung. Compared with the regional distribution of tidal breaths, oscillations preferentially reach the right and non-gravity-dependent lung. These data increase our understanding of the physiological processes underpinning nHFOV and may lead to further refinement of this novel technique.
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Affiliation(s)
- Vincent D Gaertner
- Newborn Research, Department of Neonatology, University Hospital and University of Zürich, Zürich, Switzerland
| | - Andreas D Waldmann
- Department of Anesthesiology and Intensive Care Medicine, Rostock University Medical Center, Rostock, Germany
| | - Peter G Davis
- Newborn Research Centre and Neonatal Services, The Royal Women's Hospital, Melbourne, Victoria, Australia.,The University of Melbourne, Melbourne, Victoria, Australia.,Murdoch Children's Research Institute, Melbourne, Victoria, Australia
| | - Dirk Bassler
- Newborn Research, Department of Neonatology, University Hospital and University of Zürich, Zürich, Switzerland
| | - Laila Springer
- Department of Neonatology, University Children's Hospital, Tübingen, Germany; and
| | - Jessica Thomson
- The University of Melbourne, Melbourne, Victoria, Australia.,Murdoch Children's Research Institute, Melbourne, Victoria, Australia
| | - David G Tingay
- The University of Melbourne, Melbourne, Victoria, Australia.,Murdoch Children's Research Institute, Melbourne, Victoria, Australia.,Department of Neonatology, The Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Christoph M Rüegger
- Newborn Research, Department of Neonatology, University Hospital and University of Zürich, Zürich, Switzerland
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4
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Jacob C, Tingay DG, Leontini JS. The impact of steady streaming and conditional turbulence on gas transport during high-frequency ventilation. THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS 2021; 35:265-291. [PMID: 33612975 PMCID: PMC7883339 DOI: 10.1007/s00162-020-00559-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 12/29/2020] [Indexed: 06/12/2023]
Abstract
High-frequency ventilation is a type of mechanical ventilation therapy applied on patients with damaged or delicate lungs. However, the transport of oxygen down, and carbon dioxide up, the airway is governed by subtle transport processes which hitherto have been difficult to quantify. We investigate one of these mechanisms in detail, nonlinear mean streaming, and the impact of the onset of turbulence on this streaming, via direct numerical simulations of a model 1:2 bifurcating pipe. This geometry is investigated as a minimal unit of the fractal structure of the airway. We first quantify the amount of gas recirculated via mean streaming by measuring the recirculating flux in both the upper and lower branches of the bifurcation. For conditions modeling the trachea-to-bronchi bifurcation of an infant, we find the recirculating flux is of the order of 3-5% of the peak flux . We also show that for conditions modeling the upper generations, the mean recirculation regions extend a significant distance away from the bifurcation, certainly far enough to recirculate gas between generations. We show that this mean streaming flow is driven by the formation of longitudinal vortices in the flow leaving the bifurcation. Second, we show that conditional turbulence arises in the upper generations of the airway. This turbulence appears only in the flow leaving the bifurcation, and at a point in the cycle centered around the maximum instantaneous flow rate. We hypothesize that its appearance is due to an instability of the longitudinal-vortices structure.
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Affiliation(s)
- Chinthaka Jacob
- Faculty of Science, Engineering and Technology, Swinburne University of Technology, Melbourne, VIC 3122 Australia
| | - David G. Tingay
- Murdoch Children’s Research Institute, Melbourne, VIC 3052 Australia
- Neonatology, The Royal Children’s Hospital, Melbourne, VIC 3052 Australia
| | - Justin S. Leontini
- Faculty of Science, Engineering and Technology, Swinburne University of Technology, Melbourne, VIC 3122 Australia
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5
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Azarnoosh J, Sreenivas K, Arabshahi A. Numerical Simulation of Tidal Breathing Through the Human Respiratory Tract. J Biomech Eng 2020; 142:1072681. [PMID: 31956902 DOI: 10.1115/1.4046005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Indexed: 11/08/2022]
Abstract
The objective of this study is to explore the complexity of airflow through the human respiratory tract by carrying out computational fluid dynamics simulation. In order to capture the detailed physics of the flow in this complex system, large eddy simulation (LES) is performed. The crucial step in this analysis is to investigate the impact of breathing transience on the flow field. In this connection, simulations are carried out for transient breathing in addition to peak inspiration and expiration. To enable a fair comparison, the flowrates for constant inspiration/expiration are selected to be identical to the peak flowrates during the transient breathing. Physiologically appropriate regional ventilation for two different flowrates is induced. The velocity field and turbulent flow features are discussed for both flowrates. The airflow through the larynx is observed to be significantly complex with high turbulence level, recirculation, and secondary flow while the level of turbulence decreases through the higher bifurcations.
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Affiliation(s)
- Jamasp Azarnoosh
- Department of Mechanical Engineering, The University of Tennessee at Chattanooga, Chattanooga, TN 37403
| | - Kidambi Sreenivas
- Department of Mechanical Engineering, The University of Tennessee at Chattanooga, Chattanooga, TN 37403
| | - Abdollah Arabshahi
- SimCenter - Center of Excellence in Applied Computational Science and Engineering, The University of Tennessee at Chattanooga, Chattanooga, TN 37403
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Sera T, Kuninaga H, Fukasaku K, Yokota H, Tanaka M. The Effectiveness of An Averaged Airway Model in Predicting the Airflow and Particle Transport Through the Airway. J Aerosol Med Pulm Drug Deliv 2019; 32:278-292. [PMID: 30759039 DOI: 10.1089/jamp.2018.1500] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Background: In this study, we proposed an averaged airway model design based on four healthy subjects and numerically evaluated its effectiveness for predicting the airflow and particle transport through an airway. Methods: Direct-averaged models of the conducting airways of four subjects were restored by averaging the three-dimensional (3D) skeletons of four healthy airways, which were calculated using an inverse 3D thinning algorithm. We simulated the airflow and particle transport in the individual and the averaged airway models using computational fluid dynamics. Results: The bifurcation geometry differs even among healthy subjects, but the averaged model retains the typical geometrical characteristics of the airways. The Reynolds number of the averaged model varied within the range found in the individual subject models, and the averaged model had similar inspiratory flow characteristics as the individual subject models. The deposition fractions at almost all individual lobes ranged within the variation observed in the subjects, however, the deposition fraction was higher in only one lobe. The deposition distribution at the main bifurcation point differed among the healthy subjects, but the characteristics of the averaged model fell within the variation observed in the individual subject models. On the contrary, the deposition fraction of the averaged model was higher than that of the average of the individual subject models and deviated from the range observed in the subject models. Conclusion: These results indicate that the direct-averaged model may be useful for predicting the individual airflow and particle transport on a macroscopic scale.
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Affiliation(s)
- Toshihiro Sera
- Department of Mechanical Engineering, Kyushu University, Fukuoka, Japan
| | - Hiroaki Kuninaga
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Osaka, Japan
| | - Kazuaki Fukasaku
- Image Processing Research Team, Center for Advanced Photonics, RIKEN, Saitama, Japan
| | - Hideo Yokota
- Image Processing Research Team, Center for Advanced Photonics, RIKEN, Saitama, Japan
| | - Masao Tanaka
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Osaka, Japan
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7
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Copploe A, Vatani M, Amini R, Choi JW, Tavana H. Engineered Airway Models to Study Liquid Plug Splitting at Bifurcations: Effects of Orientation and Airway Size. J Biomech Eng 2018; 140:2683661. [PMID: 30029232 DOI: 10.1115/1.4040456] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2017] [Indexed: 11/08/2022]
Abstract
Delivery of biological fluids, such as surfactant solutions, into lungs is a major strategy to treat respiratory disorders including respiratory distress syndrome that is caused by insufficient or dysfunctional natural lung surfactant. The instilled solution forms liquid plugs in lung airways. The plugs propagate downstream in airways by inspired air or ventilation, continuously split at airway bifurcations to smaller daughter plugs, simultaneously lose mass from their trailing menisci, and eventually rupture. A uniform distribution of the instilled biofluid in lung airways is expected to increase the treatments success. The uniformity of distribution of instilled liquid in the lungs greatly depends on the splitting of liquid plugs between daughter airways, especially in the first few generations from which airways of different lobes of lungs emerge. To mechanistically understand this process, we developed a bioengineering approach to computationally design three-dimensional bifurcating airway models using morphometric data of human lungs, fabricate physical models, and examine dynamics of liquid plug splitting. We found that orientation of bifurcating airways has a major effect on the splitting of liquid plugs between daughter airways. Changing the relative gravitational orientation of daughter tubes with respect to the horizontal plane caused a more asymmetric splitting of liquid plugs. Increasing the propagation speed of plugs partially counteracted this effect. Using airway models of smaller dimensions reduced the asymmetry of plug splitting. This work provides a step toward developing delivery strategies for uniform distribution of therapeutic fluids in the lungs.
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Affiliation(s)
- Antonio Copploe
- Department of Biomedical Engineering, The University of Akron, Akron, OH 44325
| | - Morteza Vatani
- Department of Mechanical Engineering, The University of Akron, Akron, OH 44325
| | - Rouzbeh Amini
- Department of Biomedical Engineering, The University of Akron, Akron, OH 44325
| | - Jae-Won Choi
- Department of Mechanical Engineering, The University of Akron, Akron, OH 44325
| | - Hossein Tavana
- Department of Biomedical Engineering, The University of Akron, 260 S. Forge St., Akron, OH 44325 e-mail:
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8
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Collier GJ, Kim M, Chung Y, Wild JM. 3D phase contrast MRI in models of human airways: Validation of computational fluid dynamics simulations of steady inspiratory flow. J Magn Reson Imaging 2018; 48:1400-1409. [DOI: 10.1002/jmri.26039] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 03/20/2018] [Indexed: 12/19/2022] Open
Affiliation(s)
- Guilhem J. Collier
- POLARIS, Unit of Academic Radiology, Department of Infection; Immunity and Cardiovascular Disease, University of Sheffield; Sheffield UK
| | - Minsuok Kim
- School of Engineering and Centre for Scientific Computing; University of Warwick; Coventry UK
| | - Yongmann Chung
- School of Engineering and Centre for Scientific Computing; University of Warwick; Coventry UK
| | - Jim M. Wild
- POLARIS, Unit of Academic Radiology, Department of Infection; Immunity and Cardiovascular Disease, University of Sheffield; Sheffield UK
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9
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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]
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10
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Han B, Hirahara H. Effect of Gas Oscillation-Induced Irreversible Flow in Transitional Bronchioles of Human Lung. ACTA ACUST UNITED AC 2016. [DOI: 10.4236/jfcmv.2016.44015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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11
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Bates AJ, Doorly DJ, Cetto R, Calmet H, Gambaruto AM, Tolley NS, Houzeaux G, Schroter RC. Dynamics of airflow in a short inhalation. J R Soc Interface 2015; 12:20140880. [PMID: 25551147 PMCID: PMC4277078 DOI: 10.1098/rsif.2014.0880] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
During a rapid inhalation, such as a sniff, the flow in the airways accelerates and decays quickly. The consequences for flow development and convective transport of an inhaled gas were investigated in a subject geometry extending from the nose to the bronchi. The progress of flow transition and the advance of an inhaled non-absorbed gas were determined using highly resolved simulations of a sniff 0.5 s long, 1 l s⁻¹ peak flow, 364 ml inhaled volume. In the nose, the distribution of airflow evolved through three phases: (i) an initial transient of about 50 ms, roughly the filling time for a nasal volume, (ii) quasi-equilibrium over the majority of the inhalation, and (iii) a terminating phase. Flow transition commenced in the supraglottic region within 20 ms, resulting in large-amplitude fluctuations persisting throughout the inhalation; in the nose, fluctuations that arose nearer peak flow were of much reduced intensity and diminished in the flow decay phase. Measures of gas concentration showed non-uniform build-up and wash-out of the inhaled gas in the nose. At the carina, the form of the temporal concentration profile reflected both shear dispersion and airway filling defects owing to recirculation regions.
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Affiliation(s)
- A. J. Bates
- Department of Aeronautics, Imperial College London, London SW7 2AZ, UK
- e-mail:
| | - D. J. Doorly
- Department of Aeronautics, Imperial College London, London SW7 2AZ, UK
| | - R. Cetto
- Department of Aeronautics, Imperial College London, London SW7 2AZ, UK
- Department of Otolaryngology, St Mary's Hospital, Imperial College Healthcare Trust, London W2 1NY, UK
| | - H. Calmet
- Computer Applications in Science and Engineering, Barcelona Supercomputing Center (BSC-CNS), Barcelona 08034, Spain
| | - A. M. Gambaruto
- Computer Applications in Science and Engineering, Barcelona Supercomputing Center (BSC-CNS), Barcelona 08034, Spain
| | - N. S. Tolley
- Department of Otolaryngology, St Mary's Hospital, Imperial College Healthcare Trust, London W2 1NY, UK
| | - G. Houzeaux
- Computer Applications in Science and Engineering, Barcelona Supercomputing Center (BSC-CNS), Barcelona 08034, Spain
| | - R. C. Schroter
- Department of Bioengineering, Imperial College London, London SW7 2AZ, UK
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12
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Alzahrany M, Banerjee A, Salzman G. Flow transport and gas mixing during invasive high frequency oscillatory ventilation. Med Eng Phys 2014; 36:647-58. [PMID: 24656889 DOI: 10.1016/j.medengphy.2014.01.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 12/14/2013] [Accepted: 01/30/2014] [Indexed: 11/25/2022]
Abstract
A large Eddy simulation (LES) based computational fluid dynamics study was performed to investigate gas transport and mixing in patient specific human lung models during high frequency oscillatory ventilation. Different pressure-controlled waveforms (sinusoidal, exponential and square) and ventilator frequencies (15, 10 and 6Hz) were used (tidal volume=50mL). The waveforms were created by solving the equation of motion subjected to constant lung wall compliance and flow resistance. Simulations were conducted with and without endotracheal tube to understand the effect of invasive management device. Variation of pressure-controlled waveform and frequency exhibits significant differences on counter flow pattern, which could lead to a significant impact on the gas mixing efficiency. Pendelluft-like flow was present for the sinusoidal waveform at all frequencies but occurred only at early inspiration for the square waveform at highest frequency. The square waveform was most efficient for gas mixing, resulting in the least wall shear stress on the lung epithelium layer thereby reducing the risk of barotrauma to both airways and the alveoli for patients undergoing therapy.
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Affiliation(s)
- Mohammed Alzahrany
- Department of Mechanical Engineering & Mechanics, Lehigh University, Bethlehem, PA 18015, United States
| | - Arindam Banerjee
- Department of Mechanical Engineering & Mechanics, Lehigh University, Bethlehem, PA 18015, United States.
| | - Gary Salzman
- Respiratory and Critical Care Medicine, University of Missouri-Kansas City School of Medicine, Kansas City, MO 64108, United States
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13
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Abstract
Local characteristics of airflow and its global distribution in the lung are determined by interaction between resistance to flow through the airways and the compliance of the tissue, with tissue compliance dominating flow distribution in the healthy lung. Current understanding is that conceptualizing the airways of the lung as a system of smooth adjoined cylinders through which air traverses laminarly is insufficient for understanding flow and energy dissipation and is particularly poor for predicting physiologically realistic transport of particles by the airflow. With rapid advances in medical imaging, computer technologies, and computational techniques, computational fluid dynamics is now becoming a viable tool for providing detailed information on the mechanics of airflow in the human respiratory tract. Studies using such techniques have shown that the upper airway (specifically its development of a turbulent laryngeal jet in the trachea), airway geometry, branching and rotation angle, and the pattern of joining of successive bifurcations are important in determining airflow structures. It is now possible to compute airflow in physical domains that are anatomically accurate and subject specific, enabling comparisons among intersubjects, that among subjects of different ages, and that among different species.
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Affiliation(s)
- Merryn H Tawhai
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
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14
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Lizal F, Elcner J, Hopke PK, Jedelsky J, Jicha M. Development of a realistic human airway model. Proc Inst Mech Eng H 2011; 226:197-207. [DOI: 10.1177/0954411911430188] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Numerous models of human lungs with various levels of idealization have been reported in the literature; consequently, results acquired using these models are difficult to compare to in vivo measurements. We have developed a set of model components based on realistic geometries, which permits the analysis of the effects of subsequent model simplification. A realistic digital upper airway geometry except for the lack of an oral cavity has been created which proved suitable both for computational fluid dynamics (CFD) simulations and for the fabrication of physical models. Subsequently, an oral cavity was added to the tracheobronchial geometry. The airway geometry including the oral cavity was adjusted to enable fabrication of a semi-realistic model. Five physical models were created based on these three digital geometries. Two optically transparent models, one with and one without the oral cavity, were constructed for flow velocity measurements, two realistic segmented models, one with and one without the oral cavity, were constructed for particle deposition measurements, and a semi-realistic model with glass cylindrical airways was developed for optical measurements of flow velocity and in situ particle size measurements. One-dimensional phase doppler anemometry measurements were made and compared to the CFD calculations for this model and good agreement was obtained.
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Affiliation(s)
- Frantisek Lizal
- Faculty of Mechanical Engineering, Brno University of Technology, Czech Republic
| | - Jakub Elcner
- Faculty of Mechanical Engineering, Brno University of Technology, Czech Republic
| | - Philip K Hopke
- Center for Air Resources Engineering and Science, Clarkson University, USA
| | - Jan Jedelsky
- Faculty of Mechanical Engineering, Brno University of Technology, Czech Republic
| | - Miroslav Jicha
- Faculty of Mechanical Engineering, Brno University of Technology, Czech Republic
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Numerical study of high-frequency oscillatory air flow and convective mixing in a CT-based human airway model. Ann Biomed Eng 2010; 38:3550-71. [PMID: 20614248 DOI: 10.1007/s10439-010-0110-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 06/18/2010] [Indexed: 12/19/2022]
Abstract
High-frequency oscillatory ventilation (HFOV) is considered an efficient and safe respiratory technique to ventilate neonates and patients with acute respiratory distress syndrome. HFOV has very different characteristics from normal breathing physiology, with a much smaller tidal volume and a higher breathing frequency. In this study, the high-frequency oscillatory flow is studied using a computational fluid dynamics analysis in three different geometrical models with increasing complexity: a straight tube, a single-bifurcation tube model, and a computed tomography (CT)-based human airway model of up to seven generations. We aim to understand the counter-flow phenomenon at flow reversal and its role in convective mixing in these models using sinusoidal waveforms of different frequencies and Reynolds (Re) numbers. Mixing is quantified by the stretch rate analysis. In the straight-tube model, coaxial counter flow with opposing fluid streams is formed around flow reversal, agreeing with an analytical Womersley solution. However, counter flow yields no net convective mixing at end cycle. In the single-bifurcation model, counter flow at high Re is intervened with secondary vortices in the parent (child) branch at end expiration (inspiration), resulting in an irreversible mixing process. For the CT-based airway model three cases are considered, consisting of the normal breathing case, the high-frequency-normal-Re (HFNR) case, and the HFOV case. The counter-flow structure is more evident in the HFNR case than the HFOV case. The instantaneous and time-averaged stretch rates at the end of two breathing cycles and in the vicinity of flow reversal are computed. It is found that counter flow contributes about 20% to mixing in HFOV.
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Heraty KB, Laffey JG, Quinlan NJ. Fluid Dynamics of Gas Exchange in High-Frequency Oscillatory Ventilation: In Vitro Investigations in Idealized and Anatomically Realistic Airway Bifurcation Models. Ann Biomed Eng 2008; 36:1856-69. [DOI: 10.1007/s10439-008-9557-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Accepted: 08/25/2008] [Indexed: 11/24/2022]
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Fresconi FE, Prasad AK. Secondary Velocity Fields in the Conducting Airways of the Human Lung. J Biomech Eng 2007; 129:722-32. [PMID: 17887898 DOI: 10.1115/1.2768374] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
An understanding of flow and dispersion in the human respiratory airways is necessary to assess the toxicological impact of inhaled particulate matter as well as to optimize the design of inhalable pharmaceutical aerosols and their delivery systems. Secondary flows affect dispersion in the lung by mixing solute in the lumen cross section. The goal of this study is to measure and interpret these secondary velocity fields using in vitro lung models. Particle image velocimetry experiments were conducted in a three-generational, anatomically accurate model of the conducting region of the lung. Inspiration and expiration flows were examined under steady and oscillatory flow conditions. Results illustrate secondary flow fields as a function of flow direction, Reynolds number, axial location with respect to the bifurcation junction, generation, branch, phase in the oscillatory cycle, and Womersley number. Critical Dean number for the formation of secondary vortices in the airways, as well as the strength and development length of secondary flow, is characterized. The normalized secondary velocity magnitude was similar on inspiration and expiration and did not vary appreciably with generation or branch. Oscillatory flow fields were not significantly different from corresponding steady flow fields up to a Womersley number of 1 and no instabilities related to shear were detected on flow reversal. These observations were qualitatively interpreted with respect to the simple streaming, augmented dispersion, and steady streaming convective dispersion mechanisms.
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Affiliation(s)
- Frank E Fresconi
- Department of Mechanical Engineering, University of Delaware, Newark, Delaware 19716, USA.
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Sera T, Satoh S, Horinouchi H, Kobayashi K, Tanishita K. Respiratory flow in a realistic tracheostenosis model. J Biomech Eng 2003; 125:461-71. [PMID: 12968570 DOI: 10.1115/1.1589775] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The possible mechanism of wheeze generation in tracheostenosis was identified by measuring inspiratory and expiratory flow in a "morphological and distensible" realistic tracheostenosis model. The shape of the model was based on CT (Computed Tomography) images of a patient that had tracheostenosis. A trachea consists of tracheal cartilage rings and smooth muscle. Spatial variation of wall distensibility was achieved in the model by varying the wall thickness based on the elastic modulus measured in pig airways. The spatial variation influenced the flow in the airway and the turbulence production rate decreased faster at smooth muscles. Using the model, we investigated the mechanism of wheeze generation by focusing on the turbulence intensity. The turbulence intensity in expiratory flow was about twice that in inspiratory flow, and larger vortices existed in post-stenosis in expiratory flow, and thus might contribute to wheeze generation.
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Affiliation(s)
- Toshihiro Sera
- Center for Life Science and Technology, School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, 223-8522, Japan.
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Abstract
The field of respiratory flow and transport has experienced significant research activity over the past several years. Important contributions to the knowledge base come from pulmonary and critical care medicine, surgery, physiology, environmental health sciences, biophysics, and engineering. Several disciplines within engineering have strong and historical ties to respiration including mechanical, chemical, civil/environmental, aerospace and, of course, biomedical engineering. This review draws from a wide variety of scientific literature that reflects the diverse constituency and audience that respiratory science has developed. The subject areas covered include nasal flow and transport, airway gas flow, alternative modes of ventilation, nonrespiratory gas transport, aerosol transport, airway stability, mucus transport, pulmonary acoustics, surfactant dynamics and delivery, and pleural liquid flow. Within each area are a number of subtopics whose exploration can provide the opportunity of both depth and breadth for the interested reader.
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Affiliation(s)
- J B Grotberg
- Biomedical Engineering Department, University of Michigan, 3304 G.G. Brown Bldg., 2350 Hayward St., Ann Arbor, MI 48109-2125, USA.
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