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Miserocchi G. Physiopathology of High-Altitude Pulmonary Edema. High Alt Med Biol 2024. [PMID: 39331568 DOI: 10.1089/ham.2024.0037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/29/2024] Open
Abstract
The air-blood barrier is well designed to accomplish the matching of gas diffusion with blood flow. This function is achieved by maintaining its thickness at ∼0.5 µm, a feature implying to keep extravascular lung water to the minimum. Exposure to hypobaric hypoxia, especially when associated with exercise, is a condition potentially leading to the development of the so-called high-altitude pulmonary edema (HAPE). This article presents a view of the physiopathology of HAPE by merging available data in humans exposed to high altitude with data from animal experimental approaches. A model is also presented to characterize HAPE nonsusceptible versus susceptible individuals based on the efficiency of alveolar-capillary oxygen uptake and estimated morphology of the air-blood barrier.
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Affiliation(s)
- Giuseppe Miserocchi
- Department of Medicine and Surgery, School of Medicine, University of Milano Bicocca, Monza, Italy
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2
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Hopkins SR, Stickland MK. The Pulmonary Vasculature. Semin Respir Crit Care Med 2023; 44:538-554. [PMID: 37816344 PMCID: PMC11192587 DOI: 10.1055/s-0043-1770059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/12/2023]
Abstract
The pulmonary circulation is a low-pressure, low-resistance circuit whose primary function is to deliver deoxygenated blood to, and oxygenated blood from, the pulmonary capillary bed enabling gas exchange. The distribution of pulmonary blood flow is regulated by several factors including effects of vascular branching structure, large-scale forces related to gravity, and finer scale factors related to local control. Hypoxic pulmonary vasoconstriction is one such important regulatory mechanism. In the face of local hypoxia, vascular smooth muscle constriction of precapillary arterioles increases local resistance by up to 250%. This has the effect of diverting blood toward better oxygenated regions of the lung and optimizing ventilation-perfusion matching. However, in the face of global hypoxia, the net effect is an increase in pulmonary arterial pressure and vascular resistance. Pulmonary vascular resistance describes the flow-resistive properties of the pulmonary circulation and arises from both precapillary and postcapillary resistances. The pulmonary circulation is also distensible in response to an increase in transmural pressure and this distention, in addition to recruitment, moderates pulmonary arterial pressure and vascular resistance. This article reviews the physiology of the pulmonary vasculature and briefly discusses how this physiology is altered by common circumstances.
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Affiliation(s)
- Susan R. Hopkins
- Department of Radiology, University of California, San Diego, California
| | - Michael K. Stickland
- Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta
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Berger MM, Luks AM. High Altitude. Semin Respir Crit Care Med 2023; 44:681-695. [PMID: 37816346 DOI: 10.1055/s-0043-1770063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/12/2023]
Abstract
With ascent to high altitude, barometric pressure declines, leading to a reduction in the partial pressure of oxygen at every point along the oxygen transport chain from the ambient air to tissue mitochondria. This leads, in turn, to a series of changes over varying time frames across multiple organ systems that serve to maintain tissue oxygen delivery at levels sufficient to prevent acute altitude illness and preserve cognitive and locomotor function. This review focuses primarily on the physiological adjustments and acclimatization processes that occur in the lungs of healthy individuals, including alterations in control of breathing, ventilation, gas exchange, lung mechanics and dynamics, and pulmonary vascular physiology. Because other organ systems, including the cardiovascular, hematologic and renal systems, contribute to acclimatization, the responses seen in these systems, as well as changes in common activities such as sleep and exercise, are also addressed. While the pattern of the responses highlighted in this review are similar across individuals, the magnitude of such responses often demonstrates significant interindividual variability which accounts for subsequent differences in tolerance of the low oxygen conditions in this environment.
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Affiliation(s)
- Marc Moritz Berger
- Department of Anesthesiology and Intensive Care Medicine, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - Andrew M Luks
- Division of Pulmonary, Critical Care and Sleep Medicine, University of Washington, Seattle, Washington
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4
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Miserocchi G. The impact of heterogeneity of the air-blood barrier on control of lung extravascular water and alveolar gas exchange. FRONTIERS IN NETWORK PHYSIOLOGY 2023; 3:1142245. [PMID: 37251706 PMCID: PMC10213913 DOI: 10.3389/fnetp.2023.1142245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 04/28/2023] [Indexed: 05/31/2023]
Abstract
The architecture of the air-blood barrier is effective in optimizing the gas exchange as long as it retains its specific feature of extreme thinness reflecting, in turn, a strict control on the extravascular water to be kept at minimum. Edemagenic conditions may perturb this equilibrium by increasing microvascular filtration; this characteristically occurs when cardiac output increases to balance the oxygen uptake with the oxygen requirement such as in exercise and hypoxia (either due to low ambient pressure or reflecting a pathological condition). In general, the lung is well equipped to counteract an increase in microvascular filtration rate. The loss of control on fluid balance is the consequence of disruption of the integrity of the macromolecular structure of lung tissue. This review, merging data from experimental approaches and evidence in humans, will explore how the heterogeneity in morphology, mechanical features and perfusion of the terminal respiratory units might impact on lung fluid balance and its control. Evidence is also provided that heterogeneities may be inborn and they could actually get worse as a consequence of a developing pathological process. Further, data are presented how in humans inter-individual heterogeneities in morphology of the terminal respiratory hinder the control of fluid balance and, in turn, hamper the efficiency of the oxygen diffusion-transport function.
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Spina S, Marrazzo F, Morais CA, Victor M, Forlini C, Guarnieri M, Bastia L, Giudici R, Bassi G, Xin Y, Cereda M, Amato M, Langer T, Berra L, Fumagalli R. Modulation of pulmonary blood flow in patients with acute respiratory failure. Nitric Oxide 2023; 136-137:1-7. [PMID: 37172929 DOI: 10.1016/j.niox.2023.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 04/19/2023] [Accepted: 05/08/2023] [Indexed: 05/15/2023]
Abstract
BACKGROUND Impairment of ventilation and perfusion (V/Q) matching is a common mechanism leading to hypoxemia in patients with acute respiratory failure requiring intensive care unit (ICU) admission. While ventilation has been thoroughly investigated, little progress has been made to monitor pulmonary perfusion at the bedside and treat impaired blood distribution. The study aimed to assess real-time changes in regional pulmonary perfusion in response to a therapeutic intervention. METHODS Single-center prospective study that enrolled adult patients with ARDS caused by SARS-Cov-2 who were sedated, paralyzed, and mechanically ventilated. The distribution of pulmonary perfusion was assessed through electrical impedance tomography (EIT) after the injection of a 10-ml bolus of hypertonic saline. The therapeutic intervention consisted in the administration of inhaled nitric oxide (iNO), as rescue therapy for refractory hypoxemia. Each patient underwent two 15-minute steps at 0 and 20 ppm iNO, respectively. At each step, respiratory, gas exchange, and hemodynamic parameters were recorded, and V/Q distribution was measured, with unchanged ventilatory settings. RESULTS Ten 65 [56-75] years old patients with moderate (40%) and severe (60%) ARDS were studied 10 [4-20] days after intubation. Gas exchange improved at 20 ppm iNO (PaO2/FiO2 from 86 ± 16 to 110 ± 30 mmHg, p = 0.001; venous admixture from 51 ± 8 to 45 ± 7%, p = 0.0045; dead space from 29 ± 8 to 25 ± 6%, p = 0.008). The respiratory system's elastic properties and ventilation distribution were unaltered by iNO. Hemodynamics did not change after gas initiation (cardiac output 7.6 ± 1.9 vs. 7.7 ± 1.9 L/min, p = 0.66). The EIT pixel perfusion maps showed a variety of patterns of changes in pulmonary blood flow, whose increase positively correlated with PaO2/FiO2 increase (R2 = 0.50, p = 0.049). CONCLUSIONS The assessment of lung perfusion is feasible at the bedside and blood distribution can be modulated with effects that are visualized in vivo. These findings might lay the foundations for testing new therapies aimed at optimizing the regional perfusion in the lungs.
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Affiliation(s)
- Stefano Spina
- Department of Anaesthesia and Critical Care, ASST Grande Ospedale Metropolitano Niguarda, Milano, Italy
| | - Francesco Marrazzo
- Department of Anaesthesia and Critical Care, ASST Grande Ospedale Metropolitano Niguarda, Milano, Italy
| | - CaioC A Morais
- Division of Pneumology (Laboratory of Medical Investigation 09), Faculty of Medicine, University of São Paulo, São Paulo, Brazil
| | - Marcus Victor
- Division of Pneumology (Laboratory of Medical Investigation 09), Faculty of Medicine, University of São Paulo, São Paulo, Brazil
| | - Clarissa Forlini
- Department of Anaesthesia and Critical Care, ASST Grande Ospedale Metropolitano Niguarda, Milano, Italy
| | - Marcello Guarnieri
- Department of Anaesthesia and Critical Care, ASST Grande Ospedale Metropolitano Niguarda, Milano, Italy
| | - Luca Bastia
- Department of Anaesthesia and Critical Care, ASST Grande Ospedale Metropolitano Niguarda, Milano, Italy
| | - Riccardo Giudici
- Department of Anaesthesia and Critical Care, ASST Grande Ospedale Metropolitano Niguarda, Milano, Italy
| | - Gabriele Bassi
- Department of Anaesthesia and Critical Care, ASST Grande Ospedale Metropolitano Niguarda, Milano, Italy
| | - Yi Xin
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Maurizio Cereda
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Marcelo Amato
- Division of Pneumology (Laboratory of Medical Investigation 09), Faculty of Medicine, University of São Paulo, São Paulo, Brazil
| | - Thomas Langer
- Department of Anaesthesia and Critical Care, ASST Grande Ospedale Metropolitano Niguarda, Milano, Italy; School of Medicine and Surgery, University of Milano-Bicocca, Milano, Italy
| | - Lorenzo Berra
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
| | - Roberto Fumagalli
- Department of Anaesthesia and Critical Care, ASST Grande Ospedale Metropolitano Niguarda, Milano, Italy; School of Medicine and Surgery, University of Milano-Bicocca, Milano, Italy
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Subedi S, Regmi P, Bhandari SS, Dawadi S. Three rare presentations of high-altitude pulmonary edema at a high-altitude clinic in the Everest region (4371 m): A case series. Clin Case Rep 2023; 11:e7236. [PMID: 37113640 PMCID: PMC10126756 DOI: 10.1002/ccr3.7236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 03/22/2023] [Accepted: 04/04/2023] [Indexed: 04/29/2023] Open
Abstract
Diagnosis of HAPE can be challenging when the presentation deviates from usual natural history. Point of care ultrasonography serves as a great diagnostic tool in such settings. An umbrella treatment could be beneficial during such scenarios.
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Affiliation(s)
- Sachin Subedi
- Institute of Medicine, Tribhuvan UniversityMaharajgunjNepal
- Himalayan Rescue Association of NepalKathmanduNepal
| | | | - Sanjeeb S. Bhandari
- Himalayan Rescue Association of NepalKathmanduNepal
- Department of Emergency MedicineWestern Maryland Medical CenterCumberlandMarylandUSA
| | - Suvash Dawadi
- Himalayan Rescue Association of NepalKathmanduNepal
- CIWEC HospitalKathmanduNepal
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Zubieta-Calleja GR, Zubieta-DeUrioste N, de Jesús Montelongo F, Sanchez MGR, Campoverdi AF, Rocco PRM, Battaglini D, Ball L, Pelosi P. Morphological and functional findings in COVID-19 lung disease as compared to Pneumonia, ARDS, and High-Altitude Pulmonary Edema. Respir Physiol Neurobiol 2023; 309:104000. [PMID: 36460252 PMCID: PMC9707029 DOI: 10.1016/j.resp.2022.104000] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 11/18/2022] [Accepted: 11/27/2022] [Indexed: 12/03/2022]
Abstract
Coronavirus disease-2019 (COVID-19) may severely affect respiratory function and evolve to life-threatening hypoxia. The clinical experience led to the implementation of standardized protocols assuming similarity to severe acute respiratory syndrome (SARS-CoV-2). Understanding the histopathological and functional patterns is essential to better understand the pathophysiology of COVID-19 and then develop new therapeutic strategies. Epithelial and endothelial cell damage can result from the virus attack, thus leading to immune-mediated response. Pulmonary histopathological findings show the presence of Mallory bodies, alveolar coating cells with nuclear atypia, reactive pneumocytes, reparative fibrosis, intra-alveolar hemorrhage, moderate inflammatory infiltrates, micro-abscesses, microthrombus, hyaline membrane fragments, and emphysema-like lung areas. COVID-19 patients may present different respiratory stages from silent to critical hypoxemia, are associated with the degree of pulmonary parenchymal involvement, thus yielding alteration of ventilation and perfusion relationships. This review aims to: discuss the morphological (histopathological and radiological) and functional findings of COVID-19 compared to acute interstitial pneumonia, acute respiratory distress syndrome (ARDS), and high-altitude pulmonary edema (HAPE), four entities that share common clinical traits, but have peculiar pathophysiological features with potential implications to their clinical management.
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Affiliation(s)
| | | | - Felipe de Jesús Montelongo
- Critical and Neurointensive Care Unit and Pathology Department, Hospital General de Ecatepec “Las Américas”, Instituto de Salud del Estado de México, México
| | - Manuel Gabriel Romo Sanchez
- Critical and Neurointensive Care Unit and Pathology Department, Hospital General de Ecatepec “Las Américas”, Instituto de Salud del Estado de México, México
| | | | - Patricia Rieken Macedo Rocco
- Laboratory of Pulmonary Investigation, Carlos Chagas Filho Institute of Biophysics, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil,COVID-19 Virus Network, Ministry of Science, Technology, and Innovation, Brasilia, Brazil
| | - Denise Battaglini
- Anesthesia and Intensive Care, San Martino Policlinico Hospital, IRCCS for Oncology and Neurosciences, Genoa, Italy,Corresponding author
| | - Lorenzo Ball
- Anesthesia and Intensive Care, San Martino Policlinico Hospital, IRCCS for Oncology and Neurosciences, Genoa, Italy,Department of Surgical Sciences and Integrated Diagnostics, University of Genoa, Genoa, Italy
| | - Paolo Pelosi
- Anesthesia and Intensive Care, San Martino Policlinico Hospital, IRCCS for Oncology and Neurosciences, Genoa, Italy,Department of Surgical Sciences and Integrated Diagnostics, University of Genoa, Genoa, Italy
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Hsia CCW, Bates JHT, Driehuys B, Fain SB, Goldin JG, Hoffman EA, Hogg JC, Levin DL, Lynch DA, Ochs M, Parraga G, Prisk GK, Smith BM, Tawhai M, Vidal Melo MF, Woods JC, Hopkins SR. Quantitative Imaging Metrics for the Assessment of Pulmonary Pathophysiology: An Official American Thoracic Society and Fleischner Society Joint Workshop Report. Ann Am Thorac Soc 2023; 20:161-195. [PMID: 36723475 PMCID: PMC9989862 DOI: 10.1513/annalsats.202211-915st] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Multiple thoracic imaging modalities have been developed to link structure to function in the diagnosis and monitoring of lung disease. Volumetric computed tomography (CT) renders three-dimensional maps of lung structures and may be combined with positron emission tomography (PET) to obtain dynamic physiological data. Magnetic resonance imaging (MRI) using ultrashort-echo time (UTE) sequences has improved signal detection from lung parenchyma; contrast agents are used to deduce airway function, ventilation-perfusion-diffusion, and mechanics. Proton MRI can measure regional ventilation-perfusion ratio. Quantitative imaging (QI)-derived endpoints have been developed to identify structure-function phenotypes, including air-blood-tissue volume partition, bronchovascular remodeling, emphysema, fibrosis, and textural patterns indicating architectural alteration. Coregistered landmarks on paired images obtained at different lung volumes are used to infer airway caliber, air trapping, gas and blood transport, compliance, and deformation. This document summarizes fundamental "good practice" stereological principles in QI study design and analysis; evaluates technical capabilities and limitations of common imaging modalities; and assesses major QI endpoints regarding underlying assumptions and limitations, ability to detect and stratify heterogeneous, overlapping pathophysiology, and monitor disease progression and therapeutic response, correlated with and complementary to, functional indices. The goal is to promote unbiased quantification and interpretation of in vivo imaging data, compare metrics obtained using different QI modalities to ensure accurate and reproducible metric derivation, and avoid misrepresentation of inferred physiological processes. The role of imaging-based computational modeling in advancing these goals is emphasized. Fundamental principles outlined herein are critical for all forms of QI irrespective of acquisition modality or disease entity.
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Yu JZ, Granberg T, Shams R, Petersson S, Sköld M, Nyrén S, Lundberg J. Lung perfusion disturbances in nonhospitalized post-COVID with dyspnea-A magnetic resonance imaging feasibility study. J Intern Med 2022; 292:941-956. [PMID: 35946904 PMCID: PMC9539011 DOI: 10.1111/joim.13558] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
BACKGROUND Dyspnea is common after COVID-19. Though the underlying mechanisms are largely unknown, lung perfusion abnormalities could contribute to lingering dyspnea. OBJECTIVES To detect pulmonary perfusion disturbances in nonhospitalized individuals with the post-COVID condition and persistent dyspnea 4-13 months after the disease onset. METHODS Individuals with dyspnea and matched healthy controls were recruited for dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), a 6-min walk test, and an assessment of dyspnea. The DCE-MRI was quantified using two parametric values: mean time to peak (TTP) and TTP ratio, reflecting the total lung perfusion resistance and the fraction of lung with delayed perfusion, respectively. RESULTS Twenty-eight persons with persistent dyspnea (mean age 46.5 ± 8.0 years, 75% women) and 22 controls (mean age 44.1 ± 10.8 years, 73% women) were included. There was no systematic sex difference in dyspnea. The post-COVID group had no focal perfusion deficits but had higher mean pulmonary TTP (0.43 ± 0.04 vs. 0.41 ± 0.03, p = 0.011) and TTP ratio (0.096 ± 0.052 vs. 0.068 ± 0.027, p = 0.032). Post-COVID males had the highest mean TTP of 0.47 ± 0.02 and TTP ratio of 0.160 ± 0.039 compared to male controls and post-COVID females (p = 0.001 and p < 0.001, respectively). Correlations between dyspnea and perfusion parameters were demonstrated in males (r = 0.83, p < 0.001 for mean TTP; r = 0.76, p = 0.003 for TTP ratio), but not in females. CONCLUSIONS DCE-MRI demonstrated late contrast bolus arrival in males with post-COVID dyspnea, suggestive of primary vascular lesions or secondary effects of hypoxic vasoconstriction. Since this effect was not regularly observed in female patients, our findings suggest sex differences in the mechanisms underlying post-COVID dyspnea, which warrants further investigation in dedicated trials.
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Affiliation(s)
- Jimmy Z. Yu
- Department of Radiology SolnaKarolinska University HospitalStockholmSweden
- Department of Molecular Medicine and SurgeryKarolinska InstitutetStockholmSweden
| | - Tobias Granberg
- Department of NeuroradiologyKarolinska University HospitalStockholmSweden
- Department of Clinical NeuroscienceKarolinska InstitutetStockholmSweden
| | - Roya Shams
- Department of NeuroradiologyKarolinska University HospitalStockholmSweden
| | - Sven Petersson
- Department of Clinical NeuroscienceKarolinska InstitutetStockholmSweden
- Department of Medical Radiation Physics and Nuclear MedicineKarolinska University HospitalStockholmSweden
| | - Magnus Sköld
- Department of Respiratory Medicine and AllergyKarolinska University HospitalStockholmSweden
- Department of Medicine SolnaKarolinska InstitutetStockholmSweden
| | - Sven Nyrén
- Department of Radiology SolnaKarolinska University HospitalStockholmSweden
- Department of Molecular Medicine and SurgeryKarolinska InstitutetStockholmSweden
| | - Johan Lundberg
- Department of NeuroradiologyKarolinska University HospitalStockholmSweden
- Department of Clinical NeuroscienceKarolinska InstitutetStockholmSweden
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10
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Tetzlaff K, Swenson ER, Bärtsch P. An update on environment-induced pulmonary edema – “When the lungs leak under water and in thin air”. Front Physiol 2022; 13:1007316. [PMID: 36277204 PMCID: PMC9585243 DOI: 10.3389/fphys.2022.1007316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 09/08/2022] [Indexed: 11/16/2022] Open
Abstract
Acute pulmonary edema is a serious condition that may occur as a result of increased hydrostatic forces within the lung microvasculature or increased microvascular permeability. Heart failure or other cardiac or renal disease are common causes of cardiogenic pulmonary edema. However, pulmonary edema may even occur in young and healthy individuals when exposed to extreme environments, such as immersion in water or at high altitude. Immersion pulmonary edema (IPE) and high-altitude pulmonary edema (HAPE) share some morphological and clinical characteristics; however, their underlying mechanisms may be different. An emerging understanding of IPE indicates that an increase in pulmonary artery and capillary pressures caused by substantial redistribution of venous blood from the extremities to the chest, in combination with stimuli aggravating the effects of water immersion, such as exercise and cold temperature, play an important role, distinct from hypoxia-induced vasoconstriction in high altitude pulmonary edema. This review aims at a current perspective on both IPE and HAPE, providing a comparative view of clinical presentation and pathophysiology. A particular emphasis will be on recent advances in understanding of the pathophysiology and occurrence of IPE with a future perspective on remaining research needs.
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Affiliation(s)
- Kay Tetzlaff
- Medical Clinic, Department of Sports Medicine, University of Tübingen, Tübingen, Germany
- *Correspondence: Kay Tetzlaff,
| | - Erik R. Swenson
- Department of Medicine, University of Washington, Seattle, WA, United States
- Division of Pulmonary Medicine and Critical Care, University of Washington, Seattle, WA, United States
| | - Peter Bärtsch
- Department of Internal Medicine, University of Heidelberg, Heidelberg, Germany
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11
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Berger MM, Sareban M, Schiefer LM, Swenson KE, Treff F, Schäfer L, Schmidt P, Schimke MM, Paar M, Niebauer J, Cogo A, Kriemler S, Schwery S, Pickerodt PA, Mayer B, Bärtsch P, Swenson ER. Effects of acetazolamide on pulmonary artery pressure and prevention of high altitude pulmonary edema after rapid active ascent to 4,559 m. J Appl Physiol (1985) 2022; 132:1361-1369. [PMID: 35511718 DOI: 10.1152/japplphysiol.00806.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Acetazolamide prevents acute mountain sickness (AMS) by inhibition of carbonic anhydrase. Since it reduces acute hypoxic pulmonary vasoconstriction (HPV), it may also prevent high-altitude pulmonary edema (HAPE) by lowering pulmonary artery pressure. We tested this hypothesis in a randomized, placebo-controlled, double-blind study. Thirteen healthy, non-acclimatized lowlanders with a history of HAPE ascended (<22h) from 1,130 to 4,559m with one overnight stay at 3,611m. Medications started 48h before ascent (acetazolamide: n=7, 250mg 3x/d; placebo: n=6, 3x/d). HAPE was diagnosed by chest radiography, and pulmonary artery pressure by measurement of right ventricular to atrial pressure gradient (RVPG) by transthoracic echocardiography. AMS was evaluated with the Lake Louise Score (LLS) and AMS-C Score. Incidence of HAPE was 43% vs. 67% (acetazolamide vs. placebo, p=0.39). Ascent to altitude increased RVPG from 20±5 to 43±10mmHg (p<0.001) without a group difference (p=0.68). Arterial PO2 fell to 36±9mmHg (p<0.001) and was 8.5mmHg higher with acetazolamide at high altitude (p=0.025). At high altitude, the LLS and AMS-C score remained lower in those taking acetazolamide (both p<0.05). Although acetazolamide reduced HAPE incidence by 35%, this effect was not statistically significant, and considerably less than reductions of about 70-100% with prophylactic dexamethasone, tadalafil, and nifedipine performed with the same ascent profile at the same location. We could not demonstrate a reduction in RVPG compared to placebo treatment despite reductions in AMS severity and better arterial oxygenation. Limited by a small sample size, our data do not support recommending acetazolamide for prevention of HAPE in mountaineers ascending rapidly to over 4,500m.
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Affiliation(s)
- Marc Moritz Berger
- Department of Anesthesiology and Intensive Care Medicine, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - Mahdi Sareban
- University Institute of Sports Medicine, Prevention and Rehabilitation, Paracelsus Medical University, Salzburg, Austria; Research Institute of Molecular Sports Medicine and Rehabilitation, Paracelsus Medical University, Salzburg, Austria
| | - Lisa Maria Schiefer
- Department of Anesthesiology, Critical Care and Pain Medicine, University Hospital Salzburg, Paracelsus Medical University, Salzburg, Austria
| | - Kai Erik Swenson
- Division of Pulmonary and Critical Care Medicine, Massachusetts General Hospital, Boston, MA, United States
| | - Franziska Treff
- Department of Anesthesiology, Critical Care and Pain Medicine, University Hospital Salzburg, Paracelsus Medical University, Salzburg, Austria
| | - Larissa Schäfer
- Department of Anesthesiology, Critical Care and Pain Medicine, University Hospital Salzburg, Paracelsus Medical University, Salzburg, Austria
| | - Peter Schmidt
- Department of Anesthesiology, Critical Care and Pain Medicine, University Hospital Salzburg, Paracelsus Medical University, Salzburg, Austria
| | - Magdalena M Schimke
- Department of Anesthesiology, Critical Care and Pain Medicine, University Hospital Salzburg, Paracelsus Medical University, Salzburg, Austria
| | - Michael Paar
- Department of Radiology, Paracelsus Medical University, Salzburg, Austria
| | - Josef Niebauer
- University Institute of Sports Medicine, Prevention and Rehabilitation, Paracelsus Medical University, Salzburg, Austria; Research Institute of Molecular Sports Medicine and Rehabilitation, Paracelsus Medical University, Salzburg, Austria
| | - Annalisa Cogo
- Biomedical Sport Studies Center, University of Ferrara, Ferrara, Italy
| | - Susi Kriemler
- Epidemiology, Biostatistics and Public Health Institute, University of Zürich, Zurich, Switzerland
| | | | - Philipp Andreas Pickerodt
- Department of Anesthesiology and Operative Intensive Care Medicine, Campus Charité Mitte and Virchow-Klinikum, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Benjamin Mayer
- Institute for Epidemiology and Medical Biometry, Ulm University, Ulm, Germany
| | - Peter Bärtsch
- Department of Internal Medicine, University of Heidelberg, Heidelberg, Germany
| | - Erik R Swenson
- Pulmonary, Critical Care and Sleep Medicine, VA Puget Sound Health Care System, University of Washington, Seattle, WA, United States
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12
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Buxton RB, Prisk GK, Hopkins SR. A novel nonlinear analysis of blood flow dynamics applied to the human lung. J Appl Physiol (1985) 2022; 132:1546-1559. [PMID: 35421317 DOI: 10.1152/japplphysiol.00715.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The spatial/temporal dynamics of blood flow in the human lung can be measured noninvasively with magnetic resonance imaging (MRI) using arterial spin labeling (ASL). We report a novel data analysis method using nonlinear prediction to identify dynamic interactions between blood flow units (image voxels), potentially providing a probe of underlying vascular control mechanisms. The approach first estimates the linear relationship (predictability) of one voxel time series with another using correlation analysis, and after removing the linear component estimates the nonlinear relationship with a numerical mutual information approach. Dimensionless global metrics for linear prediction (FL) and nonlinear prediction (FNL) represent the average amplitude of fluctuations in one voxel estimated by another voxel, as a percentage of the global average voxel flow. A proof-of-principle test of this approach analyzed experimental data from a study of high-altitude pulmonary edema (HAPE), providing two groups exhibiting known differences in vascular reactivity. Subjects were mountaineers divided into HAPE-susceptible (S, n=4) and HAPE-resistant (R, n=5) groups based on prior history at high altitude. Dynamic ASL measurements in the lung in normoxia (N, FIO2=0.21) and hypoxia (H, FIO2=0.13±0.01) were compared. The nonlinear prediction metric FNL decreased with hypoxia (7.4±1.3(N) vs. 6.3±0.7(H), P=0.03) and was significantly different between groups (7.4±1.2 (R) vs. 6.2±14.1 (S), P=0.03). This proof-of-principle test demonstrates that this nonlinear analysis approach applied to ASL data is sensitive to physiological effects even in small subject cohorts, and potentially can be used in a wide range of studies in health and disease in the lung and other organs.
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Affiliation(s)
| | | | - Susan Roberta Hopkins
- Department of Radiology, University of California San Diego.,Department of Medicine, University of California San Diego
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13
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Miserocchi G, Beretta E, Rivolta I, Bartesaghi M. Role of the Air-Blood Barrier Phenotype in Lung Oxygen Uptake and Control of Extravascular Water. Front Physiol 2022; 13:811129. [PMID: 35418875 PMCID: PMC8996119 DOI: 10.3389/fphys.2022.811129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 02/24/2022] [Indexed: 11/23/2022] Open
Abstract
The air blood barrier phenotype can be reasonably described by the ratio of lung capillary blood volume to the diffusion capacity of the alveolar membrane (Vc/Dm), which can be determined at rest in normoxia. The distribution of the Vc/Dm ratio in the population is normal; Vc/Dm shifts from ∼1, reflecting a higher number of alveoli of smaller radius, providing a high alveolar surface and a limited extension of the capillary network, to just opposite features on increasing Vc/Dm up to ∼6. We studied the kinetics of alveolar-capillary equilibration on exposure to edemagenic conditions (work at ∼60% maximum aerobic power) in hypoxia (HA) (PIO2 90 mmHg), based on an estimate of time constant of equilibration (τ) and blood capillary transit time (Tt). A shunt-like effect was described for subjects having a high Vc/Dm ratio, reflecting a longer τ (>0.5 s) and a shorter Tt (<0.8 s) due to pulmonary vasoconstriction and a larger increase in cardiac output (>3-fold). The tendency to develop lung edema in edemagenic conditions (work in HA) was found to be directly proportional to the value of Vc/Dm as suggested by an estimate of the mechanical properties of the respiratory system with the forced frequency oscillation technique.
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14
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West CM, Wearing OH, Rhem RG, Scott GR. Pulmonary hypertension is attenuated and ventilation-perfusion matching is maintained during chronic hypoxia in deer mice native to high altitude. Am J Physiol Regul Integr Comp Physiol 2021; 320:R800-R811. [PMID: 33826424 DOI: 10.1152/ajpregu.00282.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Hypoxia at high altitude can constrain metabolism and performance and can elicit physiological adjustments that are deleterious to health and fitness. Hypoxic pulmonary hypertension is a particularly serious and maladaptive response to chronic hypoxia, which results from vasoconstriction and pathological remodeling of pulmonary arteries, and can lead to pulmonary edema and right ventricle hypertrophy. We investigated whether deer mice (Peromyscus maniculatus) native to high altitude have attenuated this maladaptive response to chronic hypoxia and whether evolved changes or hypoxia-induced plasticity in pulmonary vasculature might impact ventilation-perfusion (V-Q) matching in chronic hypoxia. Deer mouse populations from both high and low altitudes were born and raised to adulthood in captivity at sea level, and various aspects of lung function were measured before and after exposure to chronic hypoxia (12 kPa O2, simulating the O2 pressure at 4,300 m) for 6-8 wk. In lowlanders, chronic hypoxia increased right ventricle systolic pressure (RVSP) from 14 to 19 mmHg (P = 0.001), in association with thickening of smooth muscle in pulmonary arteries and right ventricle hypertrophy. Chronic hypoxia also impaired V-Q matching in lowlanders (measured at rest using SPECT-CT imaging), as reflected by increased log SD of the perfusion distribution (log SDQ) from 0.55 to 0.86 (P = 0.031). In highlanders, chronic hypoxia had attenuated effects on RVSP and no effects on smooth muscle thickness, right ventricle mass, or V-Q matching. Therefore, evolved changes in lung function help attenuate maladaptive plasticity and contribute to hypoxia tolerance in high-altitude deer mice.
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Affiliation(s)
- Claire M West
- Department of Biology, McMaster University, Hamilton, Ontario, Canada
| | - Oliver H Wearing
- Department of Biology, McMaster University, Hamilton, Ontario, Canada
| | - Rod G Rhem
- Division of Respirology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Graham R Scott
- Department of Biology, McMaster University, Hamilton, Ontario, Canada
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15
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Patrician A, Spajić B, Gasho C, Caldwell HG, Dawkins T, Stembridge M, Lovering AT, Coombs GB, Howe CA, Barak O, Drviš I, Dujić Ž, Ainslie PN. Temporal changes in pulmonary gas exchange efficiency when breath-hold diving below residual volume. Exp Physiol 2021; 106:1120-1133. [PMID: 33559974 DOI: 10.1113/ep089176] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 02/04/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? How does deep breath-hold diving impact cardiopulmonary function, both acutely and over the subsequent 2.5 hours post-dive? What is the main finding and its importance? Breath-hold diving, to depths below residual volume, is associated with acute impairments in pulmonary gas exchange, which typically resolve within 2.5 hours. These data provide new insight into the behaviour of the lungs and pulmonary vasculature following deep diving. ABSTRACT Breath-hold diving involves highly integrative and extreme physiological responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure. Over two diving training camps (Study 1 and 2), 25 breath-hold divers (recreational to world-champion) performed 66 dives to 57 ± 20 m (range: 18-117 m). Using the deepest dive from each diver, temporal changes in cardiopulmonary function were assessed using non-invasive pulmonary gas exchange (indexed via the O2 deficit), ultrasound B-line scores, lung compliance and pulmonary haemodynamics at baseline and following the dive. Hydrostatically induced lung compression was quantified in Study 2, using spirometry and lung volume measurement, enabling each dive to be categorized by its residual volume (RV)-equivalent depth. From both studies, pulmonary gas exchange inefficiency - defined as an increase in O2 deficit - was related to the depth of the dive (r2 = 0.345; P < 0.001), with dives associated with lung squeeze symptoms exhibiting the greatest deficits. In Study 1, although B-lines doubled from baseline (P = 0.027), cardiac output and pulmonary artery systolic pressure were unchanged post-dive. In Study 2, dives with lung compression to ≤RV had higher O2 deficits at 9 min, compared to dives that did not exceed RV (24 ± 25 vs. 5 ± 8 mmHg; P = 0.021). The physiological significance of a small increase in estimated lung compliance post-dive (via decreased and increased/unaltered airway resistance and reactance, respectively) remains equivocal. Following deep dives, the current study highlights an integrated link between hydrostatically induced lung compression and transient impairments in pulmonary gas exchange efficiency.
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Affiliation(s)
- Alexander Patrician
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Boris Spajić
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Christopher Gasho
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Hannah G Caldwell
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Tony Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Michael Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, OR, USA
| | - Geoff B Coombs
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Connor A Howe
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Otto Barak
- Faculty of Medicine, University of Novi Sad, Novi Sad, Serbia
| | - Ivan Drviš
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Željko Dujić
- University of Split School of Medicine, Split, Croatia
| | - Philip N Ainslie
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
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16
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Pulmonary Hypertension in Acute and Chronic High Altitude Maladaptation Disorders. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph18041692. [PMID: 33578749 PMCID: PMC7916528 DOI: 10.3390/ijerph18041692] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 02/05/2021] [Accepted: 02/07/2021] [Indexed: 12/13/2022]
Abstract
Alveolar hypoxia is the most prominent feature of high altitude environment with well-known consequences for the cardio-pulmonary system, including development of pulmonary hypertension. Pulmonary hypertension due to an exaggerated hypoxic pulmonary vasoconstriction contributes to high altitude pulmonary edema (HAPE), a life-threatening disorder, occurring at high altitudes in non-acclimatized healthy individuals. Despite a strong physiologic rationale for using vasodilators for prevention and treatment of HAPE, no systematic studies of their efficacy have been conducted to date. Calcium-channel blockers are currently recommended for drug prophylaxis in high-risk individuals with a clear history of recurrent HAPE based on the extensive clinical experience with nifedipine in HAPE prevention in susceptible individuals. Chronic exposure to hypoxia induces pulmonary vascular remodeling and development of pulmonary hypertension, which places an increased pressure load on the right ventricle leading to right heart failure. Further, pulmonary hypertension along with excessive erythrocytosis may complicate chronic mountain sickness, another high altitude maladaptation disorder. Importantly, other causes than hypoxia may potentially underlie and/or contribute to pulmonary hypertension at high altitude, such as chronic heart and lung diseases, thrombotic or embolic diseases. Extensive clinical experience with drugs in patients with pulmonary arterial hypertension suggests their potential for treatment of high altitude pulmonary hypertension. Small studies have demonstrated their efficacy in reducing pulmonary artery pressure in high altitude residents. However, no drugs have been approved to date for the therapy of chronic high altitude pulmonary hypertension. This work provides a literature review on the role of pulmonary hypertension in the pathogenesis of acute and chronic high altitude maladaptation disorders and summarizes current knowledge regarding potential treatment options.
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Solaimanzadeh I. Heterogeneous Perfusion in COVID-19 and High Altitude Pulmonary Edema: A Review of Two Cases Followed by Implications for Hypoxic Pulmonary Vasoconstriction, Thrombosis Development, Ventilation Perfusion Mismatch and Emergence of Treatment Approaches. Cureus 2020; 12:e10230. [PMID: 32913696 PMCID: PMC7474561 DOI: 10.7759/cureus.10230] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Coronavirus disease 2019 (COVID-19) has been compared to high altitude pulmonary edema (HAPE). Multiple similarities between the two conditions were drawn in the past. This article seeks to further clarify potential underlying mechanisms related to hypoxia and pulmonary vascular responses. It does so by looking at perfusion imaging of patients with COVID-19 and comparing them with patterns observed in HAPE and hypoxic exposure. Two separate clinical cases are reviewed. The salient aspect of each case that is emphasized is the perfusion scintigraphy results that revealed heterogeneous perfusion patterns in both patients. Heterogeneous or non-homogeneous perfusion is also observed in HAPE. A detailed clinical course of each patient is described. Medications utilized to treat the conditions are outlined as well as laboratory parameters and clinical findings. Interestingly, both of these patients were treated with calcium channel blockers and this class of medications is utilized to prevent HAPE as well. Discussion following the case presentations attempts to contextualize possible implications of this and other studies on the broader pathophysiology of COVID-19 disease. Findings related to pathophysiologic patterns and treatment strategies are also described. Micro-thrombi formation has been reported in both COVID-19 and HAPE as well and may be an accessory complication of perfusion compromise. In a separate study, vasodilatation with calcium channel blocker (CCB) therapy has been associated with improved mortality in COVID-19 and potential pathophysiologic mechanisms were previously presented. This case report provides further clinical findings that support the notion that perfusion deficits are an integral component of hypoxia in COVID-19. It also advances the basis for use of vasodilator therapy as part of treatment regimens in COVID-19. Vasodilators may improve micro-perfusion. In this way, oxygenation may be promoted by decreasing impedance and improving flow via the alveolar-capillary unit.
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18
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COVID-19 Lung Injury and High-Altitude Pulmonary Edema. A False Equation with Dangerous Implications. Ann Am Thorac Soc 2020; 17:918-921. [PMID: 32735170 PMCID: PMC7393782 DOI: 10.1513/annalsats.202004-327cme] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Amid efforts to care for the large number of patients with coronavirus disease (COVID-19), there has been considerable speculation about whether the lung injury seen in these patients is different than acute respiratory distress syndrome from other causes. One idea that has garnered considerable attention, particularly on social media and in free open-access medicine, is the notion that lung injury due to COVID-19 is more similar to high-altitude pulmonary edema (HAPE). Drawing on this concept, it has also been proposed that treatments typically employed in the management of HAPE and other forms of acute altitude illness—pulmonary vasodilators and acetazolamide—should be considered for COVID-19. Despite some similarities in clinical features between the two entities, such as hypoxemia, radiographic opacities, and altered lung compliance, the pathophysiological mechanisms of HAPE and lung injury due to COVID-19 are fundamentally different, and the entities cannot be viewed as equivalent. Although of high utility in the management of HAPE and acute mountain sickness, systemically delivered pulmonary vasodilators and acetazolamide should not be used in the treatment of COVID-19, as they carry the risk of multiple adverse consequences, including worsened ventilation–perfusion matching, impaired carbon dioxide transport, systemic hypotension, and increased work of breathing.
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19
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Swenson KE, Berger MM, Sareban M, Macholz F, Schmidt P, Schiefer LM, Mairbäurl H, Swenson ER. Rapid Ascent to 4559 m Is Associated with Increased Plasma Components of the Vascular Endothelial Glycocalyx and May Be Associated with Acute Mountain Sickness. High Alt Med Biol 2020; 21:176-183. [DOI: 10.1089/ham.2019.0081] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Affiliation(s)
- Kai Erik Swenson
- Division of Pulmonary and Critical Care Medicine, Stanford University, Palo Alto, California, USA
| | - Marc Moritz Berger
- Department of Anesthesiology, Perioperative and General Critical Care Medicine, University Hospital Salzburg, Paracelsus Medical University, Salzburg, Austria
- Department of Anesthesiology and Intensive Care Medicine, University Hospital Essen, Essen, Germany
| | - Mahdi Sareban
- University Institute of Sports Medicine, Prevention and Rehabilitation, Paracelsus Medical University, Salzburg, Austria
- Research Institute of Molecular Sports Medicine and Rehabilitation, Paracelsus Medical University, Salzburg, Austria
| | - Franziska Macholz
- Department of Anesthesiology, Perioperative and General Critical Care Medicine, University Hospital Salzburg, Paracelsus Medical University, Salzburg, Austria
| | - Peter Schmidt
- Department of Anesthesiology, Perioperative and General Critical Care Medicine, University Hospital Salzburg, Paracelsus Medical University, Salzburg, Austria
| | - Lisa Maria Schiefer
- Department of Anesthesiology, Perioperative and General Critical Care Medicine, University Hospital Salzburg, Paracelsus Medical University, Salzburg, Austria
| | - Heimo Mairbäurl
- Division of Sports Medicine, Department of Internal Medicine VII, University Hospital Heidelberg, Heidelberg, Germany
- Translational Lung Research Center, German Center for Lung Research, Heidelberg, Germany
| | - Erik Richard Swenson
- Pulmonary, Critical Care and Sleep Medicine, VA Puget Sound Health Care System, University of Washington, Seattle, Washington, USA
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20
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Swenson ER. Early hours in the development of high-altitude pulmonary edema: time course and mechanisms. J Appl Physiol (1985) 2020; 128:1539-1546. [PMID: 32213112 DOI: 10.1152/japplphysiol.00824.2019] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Clinically evident high-altitude pulmonary edema (HAPE) is characterized by severe cyanosis, dyspnea, cough, and difficulty with physical exertion. This usually occurs within 1-2 days of ascent often with the additional stresses of any exercise and hypoventilation of sleep. The earliest events in evolving HAPE progress through clinically silent and then minimally recognized problems. The most important of these events involves an exaggerated elevation of pulmonary artery (PA) pressure in response to the ambient hypoxia. Hypoxic pulmonary vasoconstriction (HPV) is a rapid response with several phases. The first phase in both resistance arterioles and venules occurs within 5-10 min. This is followed by a second phase that further raises PA pressure by another 100% over the next 2-8 h. Combined with vasoconstriction and likely an unevenness in the regional strength of HPV, pressures in some microvascular regions with lesser arterial constriction rise to a level that initiates greater filtration of fluid into the interstitium. As pressures continue to rise local lymphatic clearance rates are exceeded and interstitial fluid begins to accumulate. Beyond elevation of transmural pressure gradients there is a dynamic noninjurious relaxation of microvascular and epithelial cell-cell contacts and an increase in transcellular vesicular transport which accelerate leakage. At some point with further pressure elevation, damage occurs with breaks of the barrier and bleeding into the alveolar space, a late-stage situation termed capillary stress failure. Earlier before there is fluid accumulation, alveolar hypoxia and hyperventilation-induced hypocapnia reduce the capacity of the alveolar epithelium to reabsorb sodium and water back into the interstitial space. More modest ascent which slows the rate of rise in PA pressure and allows for adaptive remodeling of the microvasculature, drugs which lower PA pressure, and those that can enhance fluid reabsorption will all forestall the deleterious early rise of microvascular pressures and diminished active alveolar fluid reabsorption that precede and underlie the development of HAPE.
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Affiliation(s)
- Erik R Swenson
- Pulmonary, Critical Care and Sleep Medicine, University of Washington, Veterans Affairs Puget Sound Health Care System, Seattle, Washington
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21
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Mulchrone A, Moulton H, Eldridge MW, Chesler NC. Susceptibility to high-altitude pulmonary edema is associated with increased pulmonary arterial stiffness during exercise. J Appl Physiol (1985) 2020; 128:514-522. [PMID: 31854245 DOI: 10.1152/japplphysiol.00153.2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
High-altitude pulmonary edema (HAPE), a reversible form of capillary leak, is a common consequence of rapid ascension to high altitude and a major cause of death related to high-altitude exposure. Individuals with a prior history of HAPE are more susceptible to future episodes, but the underlying risk factors remain uncertain. Previous studies have shown that HAPE-susceptible subjects have an exaggerated pulmonary vasoreactivity to acute hypoxia, but incomplete data are available regarding their vascular response to exercise. To examine this, seven HAPE-susceptible subjects and nine control subjects (HAPE-resistant) were studied at rest and during incremental exercise at sea level and at 3,810 m altitude. Studies were conducted in both normoxic (inspired Po2 = 148 Torr) and hypoxic (inspired Po2 = 91 Torr) conditions at each location. Here, we report an expanded analysis of previously published data, including a distensible vessel model that showed that HAPE-susceptible subjects had significantly reduced small distal artery distensibility at sea level compared with HAPE-resistant control subjects [0.011 ± 0.001 vs. 0.021 ± 0.002 mmHg-1; P < 0.001). Moreover, HAPE-susceptible subjects demonstrated constant distensibility over all conditions, suggesting that distal arteries are maximally distended at rest. Consistent with having increased distal artery stiffness, HAPE-susceptible subjects had greater increases in pulmonary artery pulse pressure with exercise, which suggests increased proximal artery stiffness. In summary, HAPE-susceptible subjects have exercise-induced increases in proximal artery stiffness and baseline increases in distal artery stiffness, suggesting increased pulsatile load on the right ventricle.NEW & NOTEWORTHY In comparison to subjects who appear resistant to high-altitude pulmonary edema, those previously symptomatic show greater increases in large and small artery stiffness in response to exercise. These differences in arterial stiffness may be a risk factor for the development of high-altitude pulmonary edema or evidence that consequences of high-altitude pulmonary edema are long-lasting after return to sea level.
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Affiliation(s)
- A Mulchrone
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin
| | - H Moulton
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin
| | - M W Eldridge
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin.,Department of Pediatrics, University of Wisconsin-Madison, Madison, Wisconsin
| | - N C Chesler
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin.,Department of Pediatrics, University of Wisconsin-Madison, Madison, Wisconsin.,Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin
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22
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The Hen or the Egg: Impaired Alveolar Oxygen Diffusion and Acute High-altitude Illness? Int J Mol Sci 2019; 20:ijms20174105. [PMID: 31443549 PMCID: PMC6747186 DOI: 10.3390/ijms20174105] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 08/18/2019] [Accepted: 08/20/2019] [Indexed: 01/11/2023] Open
Abstract
Individuals ascending rapidly to altitudes >2500 m may develop symptoms of acute mountain sickness (AMS) within a few hours of arrival and/or high-altitude pulmonary edema (HAPE), which occurs typically during the first three days after reaching altitudes above 3000-3500 m. Both diseases have distinct pathologies, but both present with a pronounced decrease in oxygen saturation of hemoglobin in arterial blood (SO2). This raises the question of mechanisms impairing the diffusion of oxygen (O2) across the alveolar wall and whether the higher degree of hypoxemia is in causal relationship with developing the respective symptoms. In an attempt to answer these questions this article will review factors affecting alveolar gas diffusion, such as alveolar ventilation, the alveolar-to-arterial O2-gradient, and balance between filtration of fluid into the alveolar space and its clearance, and relate them to the respective disease. The resultant analysis reveals that in both AMS and HAPE the main pathophysiologic mechanisms are activated before aggravated decrease in SO2 occurs, indicating that impaired alveolar epithelial function and the resultant diffusion limitation for oxygen may rather be a consequence, not the primary cause, of these altitude-related illnesses.
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Young JM, Williams DR, Thompson AAR. Thin Air, Thick Vessels: Historical and Current Perspectives on Hypoxic Pulmonary Hypertension. Front Med (Lausanne) 2019; 6:93. [PMID: 31119132 PMCID: PMC6504829 DOI: 10.3389/fmed.2019.00093] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 04/16/2019] [Indexed: 12/21/2022] Open
Abstract
The association between pulmonary hypertension (PH) and hypoxia is well-established, with two key mechanistic processes, hypoxic pulmonary vasoconstriction and hypoxia-induced vascular remodeling, driving changes in pulmonary arterial pressure. In contrast to other forms of pulmonary hypertension, the vascular changes induced by hypoxia are reversible, both in humans returning to sea-level from high altitude and in animal models. This raises the intriguing possibility that the molecular drivers of these hypoxic processes could be targeted to modify pulmonary vascular remodeling in other contexts. In this review, we outline the history of research into PH and hypoxia, before discussing recent advances in our understanding of this relationship at the molecular level, focussing on the role of the oxygen-sensing transcription factors, hypoxia inducible factors (HIFs). Emerging links between HIF and vascular remodeling highlight the potential utility in inhibiting this pathway in pulmonary hypertension and raise possible risks of activating this pathway using HIF-stabilizing medications.
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Affiliation(s)
- Jason M. Young
- Edinburgh Medical School, University of Edinburgh, Edinburgh, United Kingdom
- Apex (Altitude Physiology Expeditions), Edinburgh, United Kingdom
| | | | - A. A. Roger Thompson
- Apex (Altitude Physiology Expeditions), Edinburgh, United Kingdom
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
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24
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Lim R, Ma IWY, Brutsaert TD, Nysten HE, Nysten CN, Sherpa MT, Day TA. Transthoracic sonographic assessment of B-line scores during ascent to altitude among healthy trekkers. Respir Physiol Neurobiol 2019; 263:14-19. [PMID: 30794965 DOI: 10.1016/j.resp.2019.02.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 02/07/2019] [Accepted: 02/19/2019] [Indexed: 10/27/2022]
Abstract
Sonographic B-lines can indicate pulmonary interstitial edema. We sought to determine the incidence of subclinical pulmonary edema measured by sonographic B-lines among lowland trekkers ascending to high altitude in the Nepal Himalaya. Twenty healthy trekkers underwent portable sonographic examinations and arterial blood draws during ascent to 5160 m over ten days. B-lines were identified in twelve participants and more frequent at 4240 m and 5160 m compared to lower altitudes (P < 0.03). There was a strong negative correlation between arterial oxygen saturation and the number of B-lines at 5160 m (ρ = -0.75, P = 0.008). Our study contributes to the growing body of literature demonstrating the development of asymptomatic pulmonary edema during ascent to high altitude. Portable lung sonography may have utility in fieldwork contexts such as trekking at altitude, but further research is needed in order to clarify its potential clinical applicability.
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Affiliation(s)
- Rachel Lim
- Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
| | - Irene W Y Ma
- Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Tom D Brutsaert
- Department of Exercise Science and Anthropology, Syracuse University, New York, USA
| | | | - Cassandra N Nysten
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | | | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
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25
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Pratali L. Right Heart-Pulmonary Circulation at High Altitude and the Development of Subclinical Pulmonary Interstitial Edema. Heart Fail Clin 2018; 14:333-337. [PMID: 29966631 DOI: 10.1016/j.hfc.2018.02.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Most healthy subjects can develop a subclinical interstitial pulmonary edema that is a complex and multifactor phenomenon, still with unanswered questions, and might be one line of defense against the development of severe symptomatic lung edema. Whether the acute, reversible increase in lung fluid content is really an innocent and benign part of the adaptation to extreme physiologic condition or rather the clinically relevant marker of an individual vulnerability to life-threatening high altitude pulmonary edema remains to be established in future studies. Thus the question if encouraging more conservative habits to climb is right or not remains open.
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Affiliation(s)
- Lorenza Pratali
- Department of Institute of Clinical Physiology, National research Council, Via Moruzzi 1, Pisa 56214, Italy.
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Boulet LM, Teppema LJ, Hackett HK, Dominelli PB, Cheyne WS, Dominelli GS, Irwin DC, Buehler PW, Baek JH, Swenson ER, Foster GE. Attenuation of human hypoxic pulmonary vasoconstriction by acetazolamide and methazolamide. J Appl Physiol (1985) 2018; 125:1795-1803. [PMID: 30236048 DOI: 10.1152/japplphysiol.00509.2018] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
RATIONALE Acetazolamide, a carbonic anhydrase inhibitor used for preventing altitude illness attenuates hypoxic pulmonary vasoconstriction (HPV) while improving oxygenation. Methazolamide, an analog of acetazolamide, is more lipophilic, has a longer half-life, and activates a major antioxidant transcription factor. However, its influence on the hypoxic pulmonary response in humans is unknown. OBJECTIVE To determine if a clinically relevant dosing of methazolamide improves oxygenation, attenuates HPV and augments plasma antioxidant capacity in men exposed to hypoxia when compared to an established dosing of acetazolamide known to suppress HPV. METHODS In this double-blind, placebo-controlled, cross-over trial, eleven participants were randomized to treatments with methazolamide (100mg b.i.d.) and acetazolamide (250mg t.i.d.) for two days prior to 60 minutes of hypoxia (FIO2≈0.12). MEASUREMENTS Pulmonary artery systolic pressure (PASP), alveolar ventilation (V̇A), blood gases and markers of redox status were measured. Pulmonary vascular sensitivity to hypoxia was determined by indexing PASP to alveolar PO2. RESULTS Acetazolamide caused greater metabolic acidosis compared with methazolamide, but the augmented V̇A and improved oxygenation with hypoxia were similar. The rise in PASP with hypoxia was lower with methazolamide (9.0 ± 0.9 mmHg) and acetazolamide (8.0 ± 0.7 mmHg) compared with placebo (14.1 ± 1.3 mmHg; P < 0.05). The pulmonary vascular sensitivity to hypoxia (ΔPASP/ΔPAO2) was reduced equally by both drugs. Only acetazolamide improved the non-enzymatic plasma antioxidant capacity. CONCLUSIONS Although acetazolamide only had plasma antioxidant properties, methazolamide led to similar improvements in oxygenation and reduction in HPV at a dose causing less metabolic acidosis than acetazolamide in humans.
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Affiliation(s)
| | - Luc J Teppema
- Anesthesiology, Leiden University Medical Center, Netherlands
| | - Heather K Hackett
- School of Health and Exercise Sciences, University of British Columbia
| | | | | | | | - David C Irwin
- Division of Cardiovascular Pulmonary Research, University of Colorado Denver Health Sciences Center, United States
| | | | | | | | - Glen Edward Foster
- School of Health and Exercise Science, University of British Columbia, Canada
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Singh M, Yadav S, Kumar M, Saxena S, Saraswat D, Bansal A, Singh SB. The MAPK-activator protein-1 signaling regulates changes in lung tissue of rat exposed to hypobaric hypoxia. J Cell Physiol 2018; 233:6851-6865. [PMID: 29665093 DOI: 10.1002/jcp.26556] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 02/20/2018] [Indexed: 01/06/2023]
Abstract
This study reports the role of MAPKs (JNK, ERK, and p38), and activator protein-1 (AP-1) transcription factor in the hypobaric hypoxia induced change in lung tissue. Healthy male Sprague-Dawley rats were exposed to hypobaric hypoxia for 6, 12, 24, 48, 72, and 120 hr. Hypoxia resulted in significant increase in reactive oxygen species (ROS), vascular endothelial growth factor (VEGF) and decreased nitric oxide (NO), these act as signaling molecules for activation of MAPK and also contribute in development of vascular leakage (an indicator of pulmonary edema) as confirmed by histological studies. Our results confirmed JNK activation as an immediate early response (peaked at 6-48 hr), activation of ERKs (peaked at 24-72 hr) and p38 (peaked at 72-120 hr) as a secondary response to hypoxia. The MAPK pathway up regulated its downstream targets phospho c-Jun (peaked at 6-120 hr), JunB (peaked at 24-120 hr) however, decreased c-Fos, and JunD levels. DNA binding activity also confirmed activation of AP-1 transcription factor in lung tissue under hypobaric hypoxia. Further, we analyzed the proliferative and inflammatory genes regulated by different subunits of AP-1 to explore its role in vascular leakage. Increased expression of cyclin D1 (peaked at 12-72 hr) and p16 level (peaked at 48-120 hr) were correlated to the activation of c-jun, c-Fos and JunB. Administration of NFκB inhibitor caffeic acid phenethyl ester (CAPE) and SP600125 (JNK inhibitor) had no effect on increased levels of Interferon-γ (IFN-γ), Interleukin-1 (IL-1), and Tumor Necrosis Factor-α (TNF-α) thereby confirming the involvement of AP-1 as well as NFκB in inflammation. Expression of c-jun, c-Fos were correlated with activation of proliferative genes and JunB, Fra-1 with pro-inflammatory cytokines. In conclusion immediate response to hypobaric hypoxia induced c-Jun:c-Fos subunits of AP-1; responsible for proliferation that might cause inhomogeneous vasoconstriction leading to vascular leakage and inflammation at increased duration of hypobaric hypoxia exposure.
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Affiliation(s)
- Mrinalini Singh
- Defence Institute of Physiology and Allied Sciences, Timarpur, Delhi
| | - Seema Yadav
- Defence Institute of Physiology and Allied Sciences, Timarpur, Delhi
| | - Meetul Kumar
- Defence Institute of Physiology and Allied Sciences, Timarpur, Delhi
| | - Shweta Saxena
- Defence Institute of Physiology and Allied Sciences, Timarpur, Delhi
| | - Deepika Saraswat
- Defence Institute of Physiology and Allied Sciences, Timarpur, Delhi
| | - Anju Bansal
- Defence Institute of Physiology and Allied Sciences, Timarpur, Delhi
| | - Shashi B Singh
- Defence Institute of Physiology and Allied Sciences, Timarpur, Delhi
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Huertas A, Guignabert C, Barberà JA, Bärtsch P, Bhattacharya J, Bhattacharya S, Bonsignore MR, Dewachter L, Dinh-Xuan AT, Dorfmüller P, Gladwin MT, Humbert M, Kotsimbos T, Vassilakopoulos T, Sanchez O, Savale L, Testa U, Wilkins MR. Pulmonary vascular endothelium: the orchestra conductor in respiratory diseases. Eur Respir J 2018; 51:13993003.00745-2017. [DOI: 10.1183/13993003.00745-2017] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 02/03/2018] [Indexed: 12/15/2022]
Abstract
The European Respiratory Society (ERS) Research Seminar entitled “Pulmonary vascular endothelium: orchestra conductor in respiratory diseases - highlights from basic research to therapy” brought together international experts in dysfunctional pulmonary endothelium, from basic science to translational medicine, to discuss several important aspects in acute and chronic lung diseases. This review will briefly sum up the different topics of discussion from this meeting which was held in Paris, France on October 27–28, 2016. It is important to consider that this paper does not address all aspects of endothelial dysfunction but focuses on specific themes such as: 1) the complex role of the pulmonary endothelium in orchestrating the host response in both health and disease (acute lung injury, chronic obstructive pulmonary disease, high-altitude pulmonary oedema and pulmonary hypertension); and 2) the potential value of dysfunctional pulmonary endothelium as a target for innovative therapies.
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Pulmonary Vascular Dysfunction and Cor Pulmonale During Acute Respiratory Distress Syndrome in Sicklers. Shock 2018; 46:358-64. [PMID: 27206275 DOI: 10.1097/shk.0000000000000640] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Acute chest syndrome (ACS) is the most common cause of death among sickle cell disease (SCD) adult patients. Pulmonary vascular dysfunction (PVD) and acute cor pulmonale (ACP) are common during acute respiratory distress syndrome (ARDS) and their prevalence may be even more important during ARDS related to ACS (ACS-ARDS). The objective of this study was to evaluate the prevalence and prognosis of PVD and ACP during ACS-ARDS. PATIENTS AND METHODS This was a retrospective analysis over a 10-year period of patients with moderate-to-severe ARDS. PVD and ACP were assessed by echocardiography. ARDS episodes were assigned to ACS-ARDS or nonACS-ARDS group according to whether the clinical insult was ACS or not, respectively. To evaluate independent factors associated with ACP, significant univariable risk factors were examined using logistic regression and propensity score analyses. RESULTS A total of 362 patients were analyzed, including 24 ACS-ARDS. PVD and ACP were identified, respectively, in 24 (100%) and 20 (83%) ACS-ARDS patients, as compared with 204 (60%) and 68 (20%) nonACS-ARDS patients (P < 0.0001). The mortality did not differ between ACS-ARDS and nonACS-ARDS patients. Both the crude (odds ratio [OR], 19.9; 95% confidence interval [CI], 6.6-60; P < 0.0001), multivariable adjustment (OR, 27.4; 95% CI, 8.2-91.5; P < 0.001), and propensity-matched (OR, 11.7; 95% CI, 1.2-110.8; P = 0.03) analyses found a significant association between ACS-ARDS and ACP. CONCLUSIONS All SCD patients presenting with moderate-to-severe ARDS as a consequence of ACS experienced PVD and more than 80% of them exhibited ACP. These results suggest a predominant role for PVD in the pathogenesis of severe forms of ACS.
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Rong H, He X, Zhu L, Zhu X, Kang L, Wang L, He Y, Yuan D, Jin T. Association between regulator of telomere elongation helicase1 (RTEL1) gene and HAPE risk: A case-control study. Medicine (Baltimore) 2017; 96:e8222. [PMID: 28953687 PMCID: PMC5626330 DOI: 10.1097/md.0000000000008222] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
High altitude pulmonary edema (HAPE) is a paradigm of pulmonary edema. Mutations in regulator of telomere elongation helicase1 (RTEL1) represent an important contributor to risk for pulmonary fibrosis. However, little information is found about the association between RTEL1 and HAPE risk. The present study was undertaken to tentatively explore the potential relation between single-nucleotide polymorphisms (SNPs) in RTEL1 and HAPE risk in Chinese Han population. A total of 265 HAPE patients and 303 healthy controls were included in our case-control study. Four SNPs in RTEL1 were selected and genotyped using the Sequenom MassARRAY method. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated by unconditional logistic regression with adjustment for gender and age. All P values were Bonferroni corrected, and statistical significance was set at P < .0025 (.05/20). In allelic model analysis, we found that the allele "G" of rs6089953 and rs6010621 and the allele "A" of rs2297441 were associated with decreased risk of HAPE. In the genetic model analysis, we found that rs6010621, rs6089953, and rs2297441 were relevant to decreased HAPE risk under dominant model (rs6010621: OR = 0.55; 95% CI = 0.39-0.78; P = .001; rs6089953: OR = 0.68; 95% CI = 0.48-0.96; P = .027; rs2297441: OR = 0.63; 95% CI = 0.45-0.89; P = .008, respectively) and additive model (rs6010621: OR = 0.51; 95% CI = 0.46-0.81; P < .001; rs6089953: OR = 0.72; 95% CI = 0.55-0.95; P = .022; rs2297441: OR = 0.73; 95% CI = 0.57-0.95; P = .019, respectively). SNPs rs6010621 remained significant after Bonferroni correction (P < .0025). In addition, haplotype "GG, GT, AT" of rs6089953-rs6010621 were detected significantly associated with HAPE risk (P < .05), haplotype "GG" remained significant after Bonferroni correction (P < .0025). Our findings provide new evidence for the association between SNPs in RTEL1 and a decreased risk HAPE in the Chinese population. The results need further confirmation.
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Affiliation(s)
- Hao Rong
- Key Laboratory of Molecular Mechanism and Intervention Research for Plateau Diseases of Tibet Autonomous Region
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region
- Key Laboratory for Basic Life Science Research of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi
| | - Xue He
- Key Laboratory of Molecular Mechanism and Intervention Research for Plateau Diseases of Tibet Autonomous Region
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region
- Key Laboratory for Basic Life Science Research of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi
| | - Linhao Zhu
- Key Laboratory of Molecular Mechanism and Intervention Research for Plateau Diseases of Tibet Autonomous Region
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region
- Key Laboratory for Basic Life Science Research of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi
| | - Xikai Zhu
- Key Laboratory of Molecular Mechanism and Intervention Research for Plateau Diseases of Tibet Autonomous Region
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region
- Key Laboratory for Basic Life Science Research of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi
| | - Longli Kang
- Key Laboratory of Molecular Mechanism and Intervention Research for Plateau Diseases of Tibet Autonomous Region
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region
- Key Laboratory for Basic Life Science Research of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi
| | - Li Wang
- Key Laboratory of Molecular Mechanism and Intervention Research for Plateau Diseases of Tibet Autonomous Region
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region
- Key Laboratory for Basic Life Science Research of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi
| | - Yongjun He
- Key Laboratory of Molecular Mechanism and Intervention Research for Plateau Diseases of Tibet Autonomous Region
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region
- Key Laboratory for Basic Life Science Research of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi
| | - Dongya Yuan
- Key Laboratory of Molecular Mechanism and Intervention Research for Plateau Diseases of Tibet Autonomous Region
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region
- Key Laboratory for Basic Life Science Research of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi
| | - Tianbo Jin
- Key Laboratory of Molecular Mechanism and Intervention Research for Plateau Diseases of Tibet Autonomous Region
- Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region
- Key Laboratory for Basic Life Science Research of Tibet Autonomous Region, School of Medicine, Xizang Minzu University, Xianyang, Shaanxi
- School of Life Science, Northwest University, Xi’an, China
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Thin Air Resulting in High Pressure: Mountain Sickness and Hypoxia-Induced Pulmonary Hypertension. Can Respir J 2017; 2017:8381653. [PMID: 28522921 PMCID: PMC5385916 DOI: 10.1155/2017/8381653] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 02/15/2017] [Accepted: 02/28/2017] [Indexed: 12/31/2022] Open
Abstract
With rising altitude the partial pressure of oxygen falls. This phenomenon leads to hypobaric hypoxia at high altitude. Since more than 140 million people permanently live at heights above 2500 m and more than 35 million travel to these heights each year, understanding the mechanisms resulting in acute or chronic maladaptation of the human body to these circumstances is crucial. This review summarizes current knowledge of the body's acute response to these circumstances, possible complications and their treatment, and health care issues resulting from long-term exposure to high altitude. It furthermore describes the characteristic mechanisms of adaptation to life in hypobaric hypoxia expressed by the three major ethnic groups permanently dwelling at high altitude. We additionally summarize current knowledge regarding possible treatment options for hypoxia-induced pulmonary hypertension by reviewing in vitro, rodent, and human studies in this area of research.
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Abstract
In recent years, there has been a substantial increase in opioid use and abuse, and in opioid-related fatal overdoses. The increase in opioid use has resulted at least in part from individuals transitioning from prescribed opioids to heroin and fentanyl, which can cause significant respiratory depression that can progress to apnea and death. Heroin and fentanyl may be used individually, together, or in combination with other substances such as ethanol, benzodiazepines, or other drugs that can have additional deleterious effects on respiration. Suspicion that a death is drug-related begins with the decedent's medical and social history, and scene investigation, where drugs and drug paraphernalia may be encountered, and examination of the decedent, which may reveal needle punctures and needle track marks. At autopsy, the most significant internal finding that is reflective of opioid toxicity is pulmonary edema and congestion, and frothy watery fluid is often present in the airways. Various medical ailments such as heart and lung disease and obesity may limit an individual's physiologic reserve, rendering them more susceptible to the toxic effects of opioids and other drugs. Although many opioids will be detected on routine toxicology testing, more specialized testing may be warranted for opioid analogs, or other uncommon, synthetic, or semisynthetic drugs.
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Fain SB, Eldridge MW. Exploring new heights with pulmonary functional imaging: insights into high-altitude pulmonary edema. J Appl Physiol (1985) 2017; 122:853-854. [PMID: 28235856 DOI: 10.1152/japplphysiol.00168.2017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 02/21/2017] [Indexed: 11/22/2022] Open
Affiliation(s)
- Sean B Fain
- University of Wisconsin-Madison Medical School, Wisconsin; and
| | - Marlowe W Eldridge
- Pediatric Critical Care Medicine Departments of Pediatrics, Kinesiology and Biomedical Engineering, University of Wisconsin-Madison, Wisconsin
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Luks AM, Swenson ER, Bärtsch P. Acute high-altitude sickness. Eur Respir Rev 2017; 26:26/143/160096. [PMID: 28143879 PMCID: PMC9488514 DOI: 10.1183/16000617.0096-2016] [Citation(s) in RCA: 242] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 10/23/2016] [Indexed: 12/28/2022] Open
Abstract
At any point 1–5 days following ascent to altitudes ≥2500 m, individuals are at risk of developing one of three forms of acute altitude illness: acute mountain sickness, a syndrome of nonspecific symptoms including headache, lassitude, dizziness and nausea; high-altitude cerebral oedema, a potentially fatal illness characterised by ataxia, decreased consciousness and characteristic changes on magnetic resonance imaging; and high-altitude pulmonary oedema, a noncardiogenic form of pulmonary oedema resulting from excessive hypoxic pulmonary vasoconstriction which can be fatal if not recognised and treated promptly. This review provides detailed information about each of these important clinical entities. After reviewing the clinical features, epidemiology and current understanding of the pathophysiology of each disorder, we describe the current pharmacological and nonpharmacological approaches to the prevention and treatment of these diseases. Lack of acclimatisation is the main risk factor for acute altitude illness; descent is the optimal treatmenthttp://ow.ly/45d2305JyZ0
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Affiliation(s)
- Andrew M Luks
- Dept of Medicine, Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, WA, USA
| | - Erik R Swenson
- Dept of Medicine, Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, WA, USA.,Medical Service, Veterans Affairs Puget Sound Health Care System, Seattle, WA, USA
| | - Peter Bärtsch
- Dept of Internal Medicine, University Clinic Heidelberg, Heidelberg, Germany
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Patz MD, Sá RC, Darquenne C, Elliott AR, Asadi AK, Theilmann RJ, Dubowitz DJ, Swenson ER, Prisk GK, Hopkins SR. Susceptibility to high-altitude pulmonary edema is associated with a more uniform distribution of regional specific ventilation. J Appl Physiol (1985) 2017; 122:844-852. [PMID: 28057815 DOI: 10.1152/japplphysiol.00494.2016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 12/29/2016] [Accepted: 01/03/2017] [Indexed: 01/09/2023] Open
Abstract
High-altitude pulmonary edema (HAPE) is a potentially fatal condition affecting high-altitude sojourners. The biggest predictor of HAPE development is a history of prior HAPE. Magnetic resonance imaging (MRI) shows that HAPE-susceptible (with a history of HAPE), but not HAPE-resistant (with a history of repeated ascents without illness) individuals develop greater heterogeneity of regional pulmonary perfusion breathing hypoxic gas (O2 = 12.5%), consistent with uneven hypoxic pulmonary vasoconstriction (HPV). Why HPV is uneven in HAPE-susceptible individuals is unknown but may arise from regionally heterogeneous ventilation resulting in an uneven stimulus to HPV. We tested the hypothesis that ventilation is more heterogeneous in HAPE-susceptible subjects (n = 6) compared with HAPE-resistant controls (n = 7). MRI specific ventilation imaging (SVI) was used to measure regional specific ventilation and the relative dispersion (SD/mean) of SVI used to quantify baseline heterogeneity. Ventilation heterogeneity from conductive and respiratory airways was measured in normoxia and hypoxia (O2 = 12.5%) using multiple-breath washout and heterogeneity quantified from the indexes Scond and Sacin, respectively. Contrary to our hypothesis, HAPE-susceptible subjects had significantly lower relative dispersion of specific ventilation than the HAPE-resistant controls [susceptible = 1.33 ± 0.67 (SD), resistant = 2.36 ± 0.98, P = 0.05], and Sacin tended to be more uniform (susceptible = 0.085 ± 0.009, resistant = 0.113 ± 0.030, P = 0.07). Scond was not significantly different between groups (susceptible = 0.019 ± 0.007, resistant = 0.020 ± 0.004, P = 0.67). Sacin and Scond did not change significantly in hypoxia (P = 0.56 and 0.19, respectively). In conclusion, ventilation heterogeneity does not change with short-term hypoxia irrespective of HAPE susceptibility, and lesser rather than greater ventilation heterogeneity is observed in HAPE-susceptible subjects. This suggests that the basis for uneven HPV in HAPE involves vascular phenomena.NEW & NOTEWORTHY Uneven hypoxic pulmonary vasoconstriction (HPV) is thought to incite high-altitude pulmonary edema (HAPE). We evaluated whether greater heterogeneity of ventilation is also a feature of HAPE-susceptible subjects compared with HAPE-resistant subjects. Contrary to our hypothesis, ventilation heterogeneity was less in HAPE-susceptible subjects and unaffected by hypoxia, suggesting a vascular basis for uneven HPV.
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Affiliation(s)
- Michael D Patz
- Department of Anesthesiology, University of Washington, Seattle, Washington
| | - Rui C Sá
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - Chantal Darquenne
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - Ann R Elliott
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - Amran K Asadi
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - Rebecca J Theilmann
- Department of Radiology, University of California, San Diego, La Jolla, California; and
| | - David J Dubowitz
- Department of Radiology, University of California, San Diego, La Jolla, California; and
| | - Erik R Swenson
- Medical Service, Veterans Affairs Puget Sound Health Care System, University of Washington, Seattle, Washington
| | - G Kim Prisk
- Department of Medicine, University of California, San Diego, La Jolla, California.,Department of Radiology, University of California, San Diego, La Jolla, California; and
| | - Susan R Hopkins
- Department of Medicine, University of California, San Diego, La Jolla, California; .,Department of Radiology, University of California, San Diego, La Jolla, California; and
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Abstract
More than 140 million people permanently reside in high-altitude regions of Asia, South America, North America, and Africa. Another 40 million people travel to these places annually for occupational and recreational reasons, and are thus exposed to the low ambient partial pressure of oxygen. This review will focus on the pulmonary circulatory responses to acute and chronic high-altitude hypoxia, and the various expressions of maladaptation and disease arising from acute pulmonary vasoconstriction and subsequent remodeling of the vasculature when the hypoxic exposure continues. These unique conditions include high-altitude pulmonary edema, high-altitude pulmonary hypertension, subacute mountain sickness, and chronic mountain sickness.
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Affiliation(s)
- Maniraj Neupane
- Mountain Medicine Society of Nepal, Maharajgunj, Kathmandu, Nepal
| | - Erik R. Swenson
- Department of Medicine, Section of Pulmonary and Critical Care Medicine, VA Puget Sound Health Care System, University of Washington, Seattle, WA
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Dehnert C, Mereles D, Greiner S, Albers D, Scheurlen F, Zügel S, Böhm T, Vock P, Maggiorini M, Grünig E, Bärtsch P. Exaggerated hypoxic pulmonary vasoconstriction without susceptibility to high altitude pulmonary edema. High Alt Med Biol 2016; 16:11-7. [PMID: 25803140 DOI: 10.1089/ham.2014.1117] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Abnormally high pulmonary artery pressure (PAP) in hypoxia due to exaggerated hypoxic pulmonary vasoconstriction (HPV) is a key factor for development of high-altitude pulmonary edema (HAPE). It was shown that about 10% of a healthy Caucasian population has an exaggerated HPV that is comparable to the response measured in HAPE-susceptible individuals. Therefore, we hypothesized that those with exaggerated HPV are HAPE-susceptible. METHODS AND RESULTS We screened 421 healthy Caucasians naïve to high altitude for HPV using Doppler echocardiography for assessment of systolic PAP in normobaric hypoxia (PASPHx; Po2 corresponding to 4500 m). Subjects with exaggerated HPV and matched controls were exposed to 4559 m with an identical protocol that causes HAPE in 62% of HAPE-S. Screening revealed 39 subjects with exaggerated HPV, of whom 33 (PASPHx 51±6 mmHg) ascended within 24 hours to 4559 m. Four (13%) of them developed HAPE during the 48 h-stay. This incidence is significantly lower than the recurrence rate of 62% previously observed in HAPE-S in the same setting. None of the control subjects (PASPHx 33±5 mmHg) developed HAPE. CONCLUSION An exaggerated HPV cannot be considered a surrogate maker for HAPE-susceptibility although excessively elevated PAP is a hallmark in HAPE, while a normal HPV appears to protect from HAPE in this study.
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Affiliation(s)
- Christoph Dehnert
- 1 Internal Medicine VII, Sports Medicine, University Hospital Heidelberg , Germany
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Integrative Conductance of Oxygen During Exercise at Altitude. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 903:395-408. [PMID: 27343110 DOI: 10.1007/978-1-4899-7678-9_26] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In the oxygen (O2) cascade downstream steps can never achieve higher flows of O2 than the preceding ones. At the lung the transfer of O2 is determined by the O2 gradient between the alveolar space and the lung capillaries and the O2 diffusing capacity (DLO2). While DLO2 may be increased several times during exercise by recruiting more lung capillaries and by increasing the oxygen carrying capacity of blood due to higher peripheral extraction of O2, the capacity to enhance the alveolocapillary PO2 gradient is more limited. The transfer of oxygen from the alveolar space to the hemoglobin (Hb) must overcome first the resistance offered by the alveolocapillary membrane (1/DM) and the capillary blood (1/θVc). The fractional contribution of each of these two components to DLO2 remains unknown. During exercise these resistances are reduced by the recruitment of lung capillaries. The factors that reduce the slope of the oxygen dissociation curve of the Hb (ODC) (i.e., lactic acidosis and hyperthermia) increase 1/θVc contributing to limit DLO2. These effects are accentuated in hypoxia. Reducing the size of the active muscle mass improves pulmonary gas exchange during exercise and reduces the rightward shift of the ODC. The flow of oxygen from the muscle capillaries to the mitochondria is pressumably limited by muscle O2 conductance (DmcO2) (an estimation of muscle oxygen diffusing capacity). However, during maximal whole body exercise in normoxia, a higher flow of O2 is achieved at the same pressure gradients after increasing blood [Hb], implying that in healthy humans exercising in normoxia there is a functional reserve in DmcO2. This conclusion is supported by the fact that during small muscle exercise in chronic hypoxia, peak exercise DmcO2 is similar to that observed during exercise in normoxia despite a markedly lower O2 pressure gradient driving diffusion.
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Abstract
Hypoxic pulmonary vasoconstriction (HPV) represents a fundamental difference between the pulmonary and systemic circulations. HPV is active in utero, reducing pulmonary blood flow, and in adults helps to match regional ventilation and perfusion although it has little effect in healthy lungs. Many factors affect HPV including pH or PCO2, cardiac output, and several drugs, including antihypertensives. In patients with lung pathology and any patient having one-lung ventilation, HPV contributes to maintaining oxygenation, so anesthesiologists should be aware of the effects of anesthesia on this protective reflex. Intravenous anesthetic drugs have little effect on HPV, but it is attenuated by inhaled anesthetics, although less so with newer agents. The reflex is biphasic, and once the second phase becomes active after about an hour of hypoxia, this pulmonary vasoconstriction takes hours to reverse when normoxia returns. This has significant clinical implications for repeated periods of one-lung ventilation.
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Berger MM, Macholz F, Mairbäurl H, Bärtsch P. Remote ischemic preconditioning for prevention of high-altitude diseases: fact or fiction? J Appl Physiol (1985) 2015; 119:1143-51. [PMID: 26089545 DOI: 10.1152/japplphysiol.00156.2015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 06/17/2015] [Indexed: 01/14/2023] Open
Abstract
Preconditioning refers to exposure to brief episodes of potentially adverse stimuli and protects against injury during subsequent exposures. This was first described in the heart, where episodes of ischemia/reperfusion render the myocardium resistant to subsequent ischemic injury, which is likely caused by reactive oxygen species (ROS) and proinflammatory processes. Protection of the heart was also found when preconditioning was performed in an organ different from the target, which is called remote ischemic preconditioning (RIPC). The mechanisms causing protection seem to include stimulation of nitric oxide (NO) synthase, increase in antioxidant enzymes, and downregulation of proinflammatory cytokines. These pathways are also thought to play a role in high-altitude diseases: high-altitude pulmonary edema (HAPE) is associated with decreased bioavailability of NO and increased generation of ROS, whereas mechanisms causing acute mountain sickness (AMS) and high-altitude cerebral edema (HACE) seem to involve cytotoxic effects by ROS and inflammation. Based on these apparent similarities between ischemic damage and AMS, HACE, and HAPE, it is reasonable to assume that RIPC might be protective and improve altitude tolerance. In studies addressing high-altitude/hypoxia tolerance, RIPC has been shown to decrease pulmonary arterial systolic pressure in normobaric hypoxia (13% O2) and at high altitude (4,342 m). Our own results indicate that RIPC transiently decreases the severity of AMS at 12% O2. Thus preliminary studies show some benefit, but clearly, further experiments to establish the efficacy and potential mechanism of RIPC are needed.
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Affiliation(s)
- Marc Moritz Berger
- Department of Anesthesiology, Perioperative and General Critical Care Medicine, Salzburg General Hospital, Paracelsus Medical University, Salzburg, Austria; Department of Anesthesiology, University of Heidelberg, Heidelberg, Germany;
| | - Franziska Macholz
- Department of Anesthesiology, Perioperative and General Critical Care Medicine, Salzburg General Hospital, Paracelsus Medical University, Salzburg, Austria
| | - Heimo Mairbäurl
- Department of Internal Medicine VII, Division of Sports Medicine, University of Heidelberg, Heidelberg, Germany; and Translational Lung Research Center Heidelberg, German Center for Lung Research, Heidelberg, Germany
| | - Peter Bärtsch
- Department of Internal Medicine VII, Division of Sports Medicine, University of Heidelberg, Heidelberg, Germany; and
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Wilkins MR, Ghofrani HA, Weissmann N, Aldashev A, Zhao L. Pathophysiology and Treatment of High-Altitude Pulmonary Vascular Disease. Circulation 2015; 131:582-90. [DOI: 10.1161/circulationaha.114.006977] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Martin R. Wilkins
- From Experimental Medicine, Imperial College London, Hammersmith Hospital, United Kingdom (M.R.W., H.-A.G., L.Z.); Excellence Cluster Cardio-Pulmonary System, Universities of Giessen, Germany (M.R.W., H.-A.G., N.W., L.Z.); University of Giessen Marburg Lung Center, Justus-Liebig-University, Germany (M.R.W., H.-A.G., N.W., L.Z.); Kerckhoff Clinic, Bad Nauheim, Germany (H.-A.G.); Institute of Molecular Biology and Medicine, Bishkek, Kyrgyzstan (A.A.)
| | - Hossein-Ardeschir Ghofrani
- From Experimental Medicine, Imperial College London, Hammersmith Hospital, United Kingdom (M.R.W., H.-A.G., L.Z.); Excellence Cluster Cardio-Pulmonary System, Universities of Giessen, Germany (M.R.W., H.-A.G., N.W., L.Z.); University of Giessen Marburg Lung Center, Justus-Liebig-University, Germany (M.R.W., H.-A.G., N.W., L.Z.); Kerckhoff Clinic, Bad Nauheim, Germany (H.-A.G.); Institute of Molecular Biology and Medicine, Bishkek, Kyrgyzstan (A.A.)
| | - Norbert Weissmann
- From Experimental Medicine, Imperial College London, Hammersmith Hospital, United Kingdom (M.R.W., H.-A.G., L.Z.); Excellence Cluster Cardio-Pulmonary System, Universities of Giessen, Germany (M.R.W., H.-A.G., N.W., L.Z.); University of Giessen Marburg Lung Center, Justus-Liebig-University, Germany (M.R.W., H.-A.G., N.W., L.Z.); Kerckhoff Clinic, Bad Nauheim, Germany (H.-A.G.); Institute of Molecular Biology and Medicine, Bishkek, Kyrgyzstan (A.A.)
| | - Almaz Aldashev
- From Experimental Medicine, Imperial College London, Hammersmith Hospital, United Kingdom (M.R.W., H.-A.G., L.Z.); Excellence Cluster Cardio-Pulmonary System, Universities of Giessen, Germany (M.R.W., H.-A.G., N.W., L.Z.); University of Giessen Marburg Lung Center, Justus-Liebig-University, Germany (M.R.W., H.-A.G., N.W., L.Z.); Kerckhoff Clinic, Bad Nauheim, Germany (H.-A.G.); Institute of Molecular Biology and Medicine, Bishkek, Kyrgyzstan (A.A.)
| | - Lan Zhao
- From Experimental Medicine, Imperial College London, Hammersmith Hospital, United Kingdom (M.R.W., H.-A.G., L.Z.); Excellence Cluster Cardio-Pulmonary System, Universities of Giessen, Germany (M.R.W., H.-A.G., N.W., L.Z.); University of Giessen Marburg Lung Center, Justus-Liebig-University, Germany (M.R.W., H.-A.G., N.W., L.Z.); Kerckhoff Clinic, Bad Nauheim, Germany (H.-A.G.); Institute of Molecular Biology and Medicine, Bishkek, Kyrgyzstan (A.A.)
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42
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Luks AM. Physiology in Medicine: A physiologic approach to prevention and treatment of acute high-altitude illnesses. J Appl Physiol (1985) 2014; 118:509-19. [PMID: 25539941 DOI: 10.1152/japplphysiol.00955.2014] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
With the growing interest in adventure travel and the increasing ease and affordability of air, rail, and road-based transportation, increasing numbers of individuals are traveling to high altitude. The decline in barometric pressure and ambient oxygen tensions in this environment trigger a series of physiologic responses across organ systems and over a varying time frame that help the individual acclimatize to the low oxygen conditions but occasionally lead to maladaptive responses and one or several forms of acute altitude illness. The goal of this Physiology in Medicine article is to provide information that providers can use when counseling patients who present to primary care or travel medicine clinics seeking advice about how to prevent these problems. After discussing the primary physiologic responses to acute hypoxia from the organ to the molecular level in normal individuals, the review describes the main forms of acute altitude illness--acute mountain sickness, high-altitude cerebral edema, and high-altitude pulmonary edema--and the basic approaches to their prevention and treatment of these problems, with an emphasis throughout on the physiologic basis for the development of these illnesses and their management.
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Affiliation(s)
- Andrew M Luks
- Division of Pulmonary and Critical Care Medicine, University of Washington Seattle, Washington
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43
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Assessment of Pulmonary Perfusion With Breath-Hold and Free-Breathing Dynamic Contrast-Enhanced Magnetic Resonance Imaging. Invest Radiol 2014; 49:382-9. [DOI: 10.1097/rli.0000000000000020] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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44
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Burrowes KS, Clark AR, Wilsher ML, Milne DG, Tawhai MH. Hypoxic pulmonary vasoconstriction as a contributor to response in acute pulmonary embolism. Ann Biomed Eng 2014; 42:1631-43. [PMID: 24770844 DOI: 10.1007/s10439-014-1011-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 04/11/2014] [Indexed: 01/12/2023]
Abstract
Hypoxic pulmonary vasoconstriction (HPV) is an adaptive response unique to the lung whereby blood flow is diverted away from areas of low alveolar oxygen to improve ventilation-perfusion matching and resultant gas exchange. Some previous experimental studies have suggested that the HPV response to hypoxia is blunted in acute pulmonary embolism (APE), while others have concluded that HPV contributes to elevated pulmonary blood pressures in APE. To understand these contradictory observations, we have used a structure-based computational model of integrated lung function in 10 subjects to study the impact of HPV on pulmonary hemodynamics and gas exchange in the presence of regional arterial occlusion. The integrated model includes an experimentally-derived model for HPV. Its function is validated against measurements of pulmonary vascular resistance in normal subjects at four levels of inspired oxygen. Our results show that the apparently disparate observations of previous studies can be explained within a single model: the model predicts that HPV increases mean pulmonary artery pressure in APE (by 8.2 ± 7.0% in these subjects), and concurrently shows a reduction in response to hypoxia in the subjects who have high levels of occlusion and therefore maximal HPV in normoxia.
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Affiliation(s)
- K S Burrowes
- Department of Computer Science, University of Oxford, Wolfson Building, Parks Road, Oxford, OX1 3QD, UK,
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45
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Abstract
Hypoxic pulmonary vasoconstriction (HPV) continues to fascinate cardiopulmonary physiologists and clinicians since its definitive description in 1946. Hypoxic vasoconstriction exists in all vertebrate gas exchanging organs. This fundamental response of the pulmonary vasculature in air breathing animals has relevance to successful fetal transition to air breathing at birth and as a mechanism of ventilation-perfusion matching in health and disease. It is a complex process intrinsic to the vascular smooth muscle, but with in vivo modulation by a host of factors including the vascular endothelium, erythrocytes, pulmonary innervation, circulating hormones and acid-base status to name only a few. This review will provide a broad overview of HPV and its mechansms and discuss the advantages and disadvantages of HPV in normal physiology, disease and high altitude.
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Affiliation(s)
- Erik R Swenson
- Department of Medicine, University of Washington, VA Puget Sound Health Care System, Seattle, WA 98108, USA.
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46
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Genome wide expression analysis suggests perturbation of vascular homeostasis during high altitude pulmonary edema. PLoS One 2014; 9:e85902. [PMID: 24465776 PMCID: PMC3899118 DOI: 10.1371/journal.pone.0085902] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2013] [Accepted: 12/06/2013] [Indexed: 01/08/2023] Open
Abstract
Background High altitude pulmonary edema (HAPE) is a life-threatening form of non-cardiogenic edema which occurs in unacclimatized but otherwise normal individuals within two to four days after rapid ascent to altitude beyond 3000 m. The precise pathoetiology and inciting mechanisms regulating HAPE remain unclear. Methodology/Principle findings We performed global gene expression profiling in individuals with established HAPE compared to acclimatized individuals. Our data suggests concurrent modulation of multiple pathways which regulate vascular homeostasis and consequently lung fluid dynamics. These pathways included those which regulate vasoconstriction through smooth muscle contraction, cellular actin cytoskeleton rearrangements and endothelial permeability/dysfunction. Some notable genes within these pathways included MYLK; rho family members ARGEF11, ARHGAP24; cell adhesion molecules such as CLDN6, CLDN23, PXN and VCAM1 besides other signaling intermediates. Further, several important regulators of systemic/pulmonary hypertension including ADRA1D, ECE1, and EDNRA were upregulated in HAPE. We also observed significant upregulation of genes involved in paracrine signaling through chemokines and lymphocyte activation pathways during HAPE represented by transcripts of TNF, JAK2, MAP2K2, MAP2K7, MAPK10, PLCB1, ARAF, SOS1, PAK3 and RELA amongst others. Perturbation of such pathways can potentially skew vascular homeostatic equilibrium towards altered vascular permeability. Additionally, differential regulation of hypoxia-sensing, hypoxia-response and OXPHOS pathway genes in individuals with HAPE were also observed. Conclusions/Significance Our data reveals specific components of the complex molecular circuitry underlying HAPE. We show concurrent perturbation of multiple pathways regulating vascular homeostasis and suggest multi-genic nature of regulation of HAPE.
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47
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Abstract
High-altitude pulmonary edema (HAPE), a not uncommon form of acute altitude illness, can occur within days of ascent above 2500 to 3000 m. Although life-threatening, it is avoidable by slow ascent to permit acclimatization or with drug prophylaxis. The critical pathophysiology is an excessive rise in pulmonary vascular resistance or hypoxic pulmonary vasoconstriction (HPV) leading to increased microvascular pressures. The resultant hydrostatic stress causes dynamic changes in the permeability of the alveolar capillary barrier and mechanical injurious damage leading to leakage of large proteins and erythrocytes into the alveolar space in the absence of inflammation. Bronchoalveolar lavage and hemodynamic pressure measurements in humans confirm that elevated capillary pressure induces a high-permeability noninflammatory lung edema. Reduced nitric oxide availability and increased endothelin in hypoxia are the major determinants of excessive HPV in HAPE-susceptible individuals. Other hypoxia-dependent differences in ventilatory control, sympathetic nervous system activation, endothelial function, and alveolar epithelial active fluid reabsorption likely contribute additionally to HAPE susceptibility. Recent studies strongly suggest nonuniform regional hypoxic arteriolar vasoconstriction as an explanation for how HPV occurring predominantly at the arteriolar level causes leakage. In areas of high blood flow due to lesser HPV, edema develops due to pressures that exceed the dynamic and structural capacity of the alveolar capillary barrier to maintain normal fluid balance. This article will review the pathophysiology of the vasculature, alveolar epithelium, innervation, immune response, and genetics of the lung at high altitude, as well as therapeutic and prophylactic strategies to reduce the morbidity and mortality of HAPE.
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Affiliation(s)
- Erik R Swenson
- VA Puget Sound Health Care System, Department of Medicine, University of Washington, Seattle, Washington, USA.
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48
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Heinonen I, Savolainen AM, Han C, Kemppainen J, Oikonen V, Luotolahti M, Duncker DJ, Merkus D, Knuuti J, Kalliokoski KK. Pulmonary blood flow and its distribution in highly trained endurance athletes and healthy control subjects. J Appl Physiol (1985) 2013; 114:329-34. [DOI: 10.1152/japplphysiol.00710.2012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pulmonary blood flow (PBF) is an important determinant of endurance sports performance, yet studies investigating adaptations of the pulmonary circulation in athletes are scarce. In the present study, we investigated PBF, its distribution, and heterogeneity at baseline and during intravenous systemic adenosine infusion in 10 highly trained male endurance athletes and 10 untrained but fit healthy controls, using positron emission tomography and [15O]water at rest and during adenosine infusion at supine body posture. Our results indicate that PBF at rest and during adenosine stimulation was similar in both groups (213 ± 55 and 563 ± 138 ml·100 ml−1·min−1 in athletes and 206 ± 83 and 473 ± 212 ml·100 ml−1·min−1 in controls, respectively). Although the PBF response to adenosine was thus unchanged in athletes, overall PBF heterogeneity was reduced from rest to adenosine infusion (from 84 ± 18 to 70 ± 19%, P < 0.05), while remaining unchanged in healthy controls (77 ± 16 to 85 ± 33%, P = 0.4). Additionally, there was a marked gravitational influence on general PBF distribution so that clear dorsal dominance was observed both at rest and during adenosine infusion, but training status did not have an effect on this distribution. Regional blood flow heterogeneity was markedly lower in the high-perfusion dorsal areas, both at rest and during adenosine, in all subjects, but flow heterogeneity in dorsal area tended to further decrease in response to adenosine in athletes. In conclusion, reduced blood flow heterogeneity in response to adenosine in endurance athletes may be a reflection of capillary reserve, which is more extensively recruitable in athletes than in matched healthy control subjects.
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Affiliation(s)
- Ilkka Heinonen
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
- Research Center of Applied and Preventive Cardiovascular Medicine, University of Turku and Turku University Hospital, Turku, Finland
- Division of Experimental Cardiology, Thoraxcenter, Erasmus MC, University Medical Center Rotterdam, Rotterdam, the Netherlands
| | - Anna M. Savolainen
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - Chunlei Han
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - Jukka Kemppainen
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
- Department of Clinical Physiology and Nuclear Medicine, University of Turku and Turku University Hospital, Turku, Finland
| | - Vesa Oikonen
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - Matti Luotolahti
- Department of Clinical Physiology and Nuclear Medicine, University of Turku and Turku University Hospital, Turku, Finland
| | - Dirk J. Duncker
- Division of Experimental Cardiology, Thoraxcenter, Erasmus MC, University Medical Center Rotterdam, Rotterdam, the Netherlands
| | - Daphne Merkus
- Division of Experimental Cardiology, Thoraxcenter, Erasmus MC, University Medical Center Rotterdam, Rotterdam, the Netherlands
| | - Juhani Knuuti
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - Kari K. Kalliokoski
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
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49
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Abstract
This article challenges the use of hyperoxia in the perioperative period. It describes the biochemical and physiologic basis for both the direct and indirect adverse effects of oxygen. The reasons for using hyperoxia in the perioperative period are critically evaluated, and the evidence and guidelines for oxygen use in common acute medical conditions are reviewed.
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Affiliation(s)
- Andrew B Lumb
- Department of Anaesthesia, St James's University Hospital, Leeds, United Kingdom.
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50
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Risse F, Pesic J, Young S, Olsson LE. A texture analysis approach to quantify ventilation changes in hyperpolarised ³He MRI of the rat lung in an asthma model. NMR IN BIOMEDICINE 2012; 25:131-141. [PMID: 21739495 DOI: 10.1002/nbm.1725] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 03/17/2011] [Accepted: 03/17/2011] [Indexed: 05/31/2023]
Abstract
In preclinical research, allergic asthma is investigated in rats sensitised with the antigen ovalbumin (OVA), followed by a challenge with aerosolised OVA to induce an inflammatory reaction of the lower airways. This causes diffuse, nonfocal ventilation defects that lead to heterogeneously distributed signal intensities in hyperpolarised (HP) (3)He MR images, which are difficult to assess directly by diagnostic grading or volumetry. Texture analysis can characterise these changes and does not require segmentation of the lung structures prior to the analysis. The aim of this work was to evaluate a texture analysis approach to quantify changes in lung ventilation in HP (3)He MRI of OVA-challenged rats. OVA-challenged animals were treated with two different compound doses to evaluate the sensitivity of the texture analysis. Four groups were investigated using HP (3)He MRI at 4.7 T: controls, vehicle-treated, and low- and high-dose budesonide-treated rats. In addition, broncho-alveolar lavage was performed and the eosinophil cell count was used as a biological reference marker. First-order texture, geometrical features and features based on second-order statistics using run-length and grey-level co-occurrence matrices were calculated. In addition, wavelet transforms were applied to compute first-order statistics on multiple scales. The texture analysis was able to show significant differences between the control and untreated vehicle groups as well as between the vehicle and treatment groups. This is in agreement with the findings of the eosinophil cell counts, which were used as a marker for the severity of inflammation. However, not all features used in the different texture analysis methods could differentiate between the treatment groups. In conclusion, texture analysis can be used to quantify changes in lung ventilation as measured with HP (3)He MRI after therapeutic intervention with budesonide.
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Affiliation(s)
- Frank Risse
- DECS Imaging&Antibodies, AstraZeneca R&D, Mölndal, Sweden.
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