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Chen Z, Hu Z, Zhong M, Deng L, Tao J, Song Y. Potential effect of pulmonary fluid viscosity on positive end-expiratory pressure and regional distribution of lung ventilation in acute respiratory distress syndrome. Clin Biomech (Bristol, Avon) 2021; 87:105407. [PMID: 34214731 PMCID: PMC9756214 DOI: 10.1016/j.clinbiomech.2021.105407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 02/03/2021] [Accepted: 06/03/2021] [Indexed: 02/07/2023]
Abstract
BACKGROUND Computational fluid dynamic simulations have showed that the elevated viscosity of pulmonary fluids may increase the likelihood of airway closure, thus exacerbating inhomogeneity of regional lung ventilation. Unfortunately, there have been few studies directed toward measurements of viscosity of pulmonary fluids and its effect on airway opening pressure and regional distribution of lung ventilation in acute respiratory distress syndrome. METHODS In this study, pulmonary fluids from 8 ARDS patients were measured using a cone and plate rheometer on days 1, 3, 7 and 14 in the treatment of the disorder. Ventilator settings were simultaneously recorded, including tidal volume, positive end-expiratory pressure, fraction of inspired oxygen (FiO2), and so on. The regional distribution of lung ventilation was monitored by a bedside electrical impedance tomography system. FINDINGS The results showed that rheological properties of pulmonary fluids behaved as either Newtonian or non-Newtonian across all patients studied. Significant intersubject and intrasubject variations in measured viscosities were observed, spanning ranges from approximately 1 cP to 7 × 104 cP at shear rates between 0.075-750 s-1. The product of the positive end-expiratory airway pressure and fraction of inspired oxygen was well correlated with fluid viscosity in patients with high viscosity pulmonary fluids. Furthermore, lung ventilation in these patients was highly inhomogeneous and influenced by rheology of pulmonary fluids. INTERPRETATION The current findings provided the direct clinical data for theoretical models of airway reopening and may have important clinical implications in explaining inhomogeneity of lung ventilation and selecting initial levels of positive end-expiratory pressure in mechanically ventilated patients.
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Affiliation(s)
- Zhenglong Chen
- School of Medical Instrumentation, Shanghai University of Medicine & Health Sciences, Shanghai, China,NMPA Key Laboratory for Respiratory and Anaesthetic Equipment, Shanghai, China
| | - Zhaoyan Hu
- School of Medical Instrumentation, Shanghai University of Medicine & Health Sciences, Shanghai, China,NMPA Key Laboratory for Respiratory and Anaesthetic Equipment, Shanghai, China
| | - Ming Zhong
- Department of Critical Care Medicine, Zhongshan Hospital, Fudan University, Shanghai, China,Corresponding author at: Department of Critical Care Medicine, Zhongshan Hospital, Fudan University, 180 Fenglin Road, Xuhui District 200032, Shanghai, China
| | - Linhong Deng
- Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, China
| | - Jiale Tao
- Department of Critical Care Medicine, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Yuanlin Song
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan University, Shanghai, China,Corresponding author
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Munir B, Xu Y. The steady motion of microbubbles in bifurcating airways: Role of shear-thinning and surface tension. Respir Physiol Neurobiol 2021; 290:103675. [PMID: 33915302 DOI: 10.1016/j.resp.2021.103675] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 04/21/2021] [Indexed: 12/11/2022]
Abstract
Mucous fluid is non-Newtonian secretions in the lower lung airways that accumulates when the alveolar-capillary membrane ruptures during acute respiratory distress syndrome. The mucus fluid has, therefore, different types of non-Newtonian properties like shear-thinning, viscoelasticity, and non-zero yield stress. In this paper, we numerically solved the steady Stokes equations along with arbitrary Eulerian-Lagrangian moving mesh techniques to study the microbubble propagation in a two-dimensional asymmetric bifurcating airway filled with non-Newtonian fluid where the fluid has shear-thinning behavior described by the power-law model. Numerical results show that both shear-thinning and surface tension characterized by the behavior index (n) and Capillary number (Ca), respectively, had a significant impact on microbubble flow patterns and the magnitude of the pressure gradient. At low values of both n and Ca, the microbubble leaves a thin film-thickness with the airway wall while a large and sharp peak of the pressure gradient near the thin bubble tip. Interestingly, increasing both n and Ca, leads to an increase in film thickness and a decrease in the pressure gradient magnitude in both the daughter airway walls. It is observed the magnitude of the pressure gradient is more sensitive to Ca compared to n. We concluded that shear-thinning and surface tension not only significantly impact the patterns of microbubble propagation but also the hydrodynamic stress magnitudes at the airway wall.
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Affiliation(s)
- Bacha Munir
- School of Natural and Applied Sciences, Department of Applied Mathematics, Northwestern Polytechnical University, Xi'an, Shaanxi, 710029, People's Republic of China.
| | - Yong Xu
- School of Natural and Applied Sciences, Department of Applied Mathematics, Northwestern Polytechnical University, Xi'an, Shaanxi, 710029, People's Republic of China
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Chen Z, Zhong M, Jiang L, Chen N, Tu S, Wei Y, Sang L, Zheng X, Zhang C, Tao J, Deng L, Song Y. Effects of the Lower Airway Secretions on Airway Opening Pressures and Suction Pressures in Critically Ill COVID-19 Patients: A Computational Simulation. Ann Biomed Eng 2020; 48:3003-3013. [PMID: 33078367 PMCID: PMC7571532 DOI: 10.1007/s10439-020-02648-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 10/03/2020] [Indexed: 02/06/2023]
Abstract
In patients with critically ill COVID-19 pneumonia, lower airways are filled with plenty of highly viscous exudates or mucus, leading to airway occlusion. The estimation of airway opening pressures and effective mucus clearance are therefore two issues that clinicians are most concerned about during mechanical ventilation. In this study we retrospectively analyzed respiratory data from 24 critically ill patients with COVID-19 who received invasive mechanical ventilation and recruitment maneuver at Jinyintan Hospital in Wuhan, China. Among 24 patients, the mean inspiratory plateau pressure was 52.4 ± 4.4 cmH2O (mean ± [SD]). Particularly, the capnograms presented an upward slope during the expiratory plateau, indicting the existence of airway obstruction. A computational model of airway opening was subsequently introduced to investigate possible fluid dynamic mechanisms for the extraordinarily high inspiratory plateau pressures among these patients. Our simulation results showed that the predicted airway opening pressures could be as high as 40-50 cmH2O and the suction pressure could exceed 20 kPa as the surface tension and viscosity of secretion simulants markedly increased, likely causing the closures of the distal airways. We concluded that, in some critically ill patients with COVID-19, limiting plateau pressure to 30 cmH2O may not guarantee the opening of airways due to the presence of highly viscous lower airway secretions, not to mention spontaneous inspiratory efforts. Active airway humidification and effective expectorant drugs are therefore strongly recommended during airway management.
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Affiliation(s)
- Zhenglong Chen
- School of Medical Instrumentation, Shanghai University of Medicine & Health Sciences, 257 Tianxiong Road, Shanghai, 201318, China
| | - Ming Zhong
- Department of Intensive Care Medicine, Zhongshan Hospital, Fudan University, 180 Fenglin Road, Shanghai, 200032, China.
| | - Li Jiang
- Department of Critical Care Medicine, Xuanwu Hospital, Capital Medical University, 45 Changchun Street, Xicheng District, Beijing, 100053, China
| | - Nanshan Chen
- Department of Respiratory and Critical Care Medicine, Wuhan Jinyintan Hospital, 1 Yintan Road, Dongxihu District, Wuhan, 430023, China
| | - Shengjin Tu
- Department of Respiratory and Critical Care Medicine, Wuhan Jinyintan Hospital, 1 Yintan Road, Dongxihu District, Wuhan, 430023, China
| | - Yuan Wei
- Department of Respiratory and Critical Care Medicine, Wuhan Jinyintan Hospital, 1 Yintan Road, Dongxihu District, Wuhan, 430023, China
| | - Ling Sang
- Department of Critical Care Medicine, GuangZhou Institute of Respiratory Health, The First Affiliated Hospital of GuangZhou Medical University, 151 Yanjiangxi Road, Guangzhou, 510120, China
| | - Xia Zheng
- Department of Critical Care Medicine, The First Affiliated Hospital of Zhejiang University, Hangzhou, 310003, Zhejiang, China
| | - Chunyuan Zhang
- NMPA Key Laboratory for Respiratory and Anaesthetic Equipment, 1 Jinyinhua Road, Shanghai, 201321, China
| | - Jiale Tao
- Department of Intensive Care Medicine, Zhongshan Hospital, Fudan University, 180 Fenglin Road, Shanghai, 200032, China
| | - Linhong Deng
- Changzhou Key Laboratory of Respiratory Medical Engineering, Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, 213164, Jiangsu, China
| | - Yuanlin Song
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan University, 180 Fenglin Road, Xuhui District, Shanghai, 200032, China
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Horsley A, Siddiqui S. Putting lung function and physiology into perspective: cystic fibrosis in adults. Respirology 2014; 20:33-45. [PMID: 25219816 DOI: 10.1111/resp.12382] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 07/22/2014] [Accepted: 07/23/2014] [Indexed: 11/30/2022]
Abstract
Adult cystic fibrosis (CF) is notable for the wide heterogeneity in severity of disease expression, both between patients and within the lungs of individuals. Although CF airways disease appears to start in the small airways, in adults there is typically widespread bronchiectasis, increased airway secretions, and extensive obstruction and inflammation of the small airways. The complexity and heterogeneity of airways disease in CF means that although there are many different methods of assessing and describing lung 'function', none of these single-dimensional tests is able to provide a comprehensive assessment of lung physiology across the spectrum seen in adult CF. The most widely described measure, the forced expiratory volume in 1 s, remains a useful and simple clinical tool, but is insensitive to early changes and may be dissociated from other more detailed assessments of disease severity such as computed tomography. In this review, we also discuss the use of more sensitive novel assessments such as multiple breath washout tests and impulse oscillometry, as well as the role of cardiopulmonary exercise testing. In the future, hyperpolarized gas magnetic resonance imaging techniques that combine regional structural and functional information may help us to better understand these measures, their applications and limitations.
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Affiliation(s)
- Alex Horsley
- Respiratory Research Group, Institute of Inflammation and Repair, University of Manchester, Manchester, UK; Manchester Adult Cystic Fibrosis Centre, North West Lung Centre, University Hospital of South Manchester, Manchester, UK
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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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