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Müller J, Appenzeller P, Lichtblau M, Saxer S, Berlier C, Schneider SR, Furian M, Schwarz EI, Swenson ER, Bloch KE, Ulrich S. Effects of 5-Week Oral Acetazolamide on Incremental Cycling Exercise in Pulmonary Arterial and Chronic Thromboembolic Pulmonary Hypertension: A Randomized Placebo-Controlled, Double-Blinded, Crossover Trial. Respiration 2024; 103:124-133. [PMID: 38382479 DOI: 10.1159/000536399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Accepted: 01/18/2024] [Indexed: 02/23/2024] Open
Abstract
INTRODUCTION Acetazolamide (AZA) improves nocturnal and daytime blood oxygenation in patients with pulmonary vascular disease (PVD), defined as pulmonary arterial and distal chronic thromboembolic pulmonary hypertension (CTEPH), and may improve exercise performance. METHODS We investigated the effect of 5 weeks of AZA (250 mg bid) versus placebo on maximal load during incremental cycling ramp exercise in patients with PVD studied in a randomized controlled, double-blind, crossover design, separated by > 2 weeks of washout. RESULTS Twenty-five patients (12 pulmonary arterial hypertension, 13 CTEPH, 40% women, age 62 ± 15 years) completed the trial according to the protocol. Maximum load was similar after 5 weeks of AZA versus placebo (113 ± 9 vs. 117 ± 9 watts [W]), mean difference -4 W (95% CI: -9 to 1, p = 0.138). With AZA, maximum (max)-exercise partial pressure of O2 (PaO2) was significantly higher by 1.1 kPa (95% CI: 0.5-1.8, p = 0.003), while arterial pH and partial pressure of CO2 were significantly lower. Gas exchange threshold was reached at a higher load with AZA (108 ± 8 W vs. 97 ± 8 W) and was therefore delayed by 11 W (95% CI: 3-19, p = 0.013), while the ventilatory equivalent for O2 and CO2 were significantly higher at both the max-exercise and gas exchange threshold with AZA versus placebo. CONCLUSION AZA for 5 weeks did not significantly change maximum exercise capacity in patients with PVD despite a significant increase in PaO2. The beneficial effects of increased blood oxygenation may have been diminished by increased ventilation due to AZA-induced metabolic acidosis and increased dyspnea.
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Affiliation(s)
- Julian Müller
- Clinic of Pulmonology, University Hospital Zurich, Zurich, Switzerland,
- Faculty of Medicine, University of Zurich, Zurich, Switzerland,
| | - Paula Appenzeller
- Clinic of Pulmonology, University Hospital Zurich, Zurich, Switzerland
- Faculty of Medicine, University of Zurich, Zurich, Switzerland
| | - Mona Lichtblau
- Clinic of Pulmonology, University Hospital Zurich, Zurich, Switzerland
- Faculty of Medicine, University of Zurich, Zurich, Switzerland
| | - Stéphanie Saxer
- Clinic of Pulmonology, University Hospital Zurich, Zurich, Switzerland
- Faculty of Medicine, University of Zurich, Zurich, Switzerland
| | - Charlotte Berlier
- Clinic of Pulmonology, University Hospital Zurich, Zurich, Switzerland
- Faculty of Medicine, University of Zurich, Zurich, Switzerland
| | - Simon R Schneider
- Clinic of Pulmonology, University Hospital Zurich, Zurich, Switzerland
- Faculty of Medicine, University of Zurich, Zurich, Switzerland
| | - Michael Furian
- Clinic of Pulmonology, University Hospital Zurich, Zurich, Switzerland
- Faculty of Medicine, University of Zurich, Zurich, Switzerland
| | - Esther I Schwarz
- Clinic of Pulmonology, University Hospital Zurich, Zurich, Switzerland
- Faculty of Medicine, University of Zurich, Zurich, Switzerland
| | - Erik R Swenson
- Division of Pulmonary, Critical Care and Sleep Medicine, University of Washington, Seattle, Washington, USA
| | - Konrad E Bloch
- Clinic of Pulmonology, University Hospital Zurich, Zurich, Switzerland
- Faculty of Medicine, University of Zurich, Zurich, Switzerland
| | - Silvia Ulrich
- Clinic of Pulmonology, University Hospital Zurich, Zurich, Switzerland
- Faculty of Medicine, University of Zurich, Zurich, Switzerland
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Pei C, Jia N, Wang Y, Zhao S, Shen Z, Shi S, Huang D, Wu Y, Wang X, Li S, He Y, Wang Z. Notoginsenoside R1 protects against hypobaric hypoxia-induced high-altitude pulmonary edema by inhibiting apoptosis via ERK1/2-P90rsk-BAD ignaling pathway. Eur J Pharmacol 2023; 959:176065. [PMID: 37775017 DOI: 10.1016/j.ejphar.2023.176065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 09/03/2023] [Accepted: 09/19/2023] [Indexed: 10/01/2023]
Abstract
High-altitude pulmonary edema (HAPE) is a potentially fatal disease. Notoginsenoside R1 is a novel phytoestrogen with anti-inflammatory, antioxidant and anti-apoptosis properties. However, its effects and underlying mechanisms in the protection of hypobaric hypoxia-induced HAPE rats remains unclear. This study aimed to explore the protective effects and underlying mechanisms of Notoginsenoside R1 in hypobaric hypoxia-induced HAPE. We found that Notoginsenoside R1 alleviated the lung tissue injury, decreased lung wet/dry ratio, and reduced inflammation and oxidative stress. Additionally, Notoginsenoside R1 ameliorated the changes in arterial blood gas, decreased the total protein concentration in bronchoalveolar lavage fluid, and inhibited the occurrence of apoptosis caused by HAPE. In the process of further exploration of the mechanism, it was found that Notoginsenoside R1 could promote the activation of ERK1/2-P90rsk-BAD signaling pathway, and the effect of Notoginsenoside R1 was attenuated after the use of ERK1/2 inhibitor U0126. Our study indicated that the protective effects of Notoginsenoside R1 against HAPE were mainly related to the inhibition of inflammation, oxidative stress, and apoptosis. Notoginsenoside R1 may be a potential candidate for preventing HAPE.
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Affiliation(s)
- Caixia Pei
- Hospital of Chengdu University of Traditional Chinese Medicine, No.39 Shi-er-qiao Road, Chengdu, Sichuan 610075, China
| | - Nan Jia
- Hospital of Chengdu University of Traditional Chinese Medicine, No.39 Shi-er-qiao Road, Chengdu, Sichuan 610075, China
| | - Yilan Wang
- Hospital of Chengdu University of Traditional Chinese Medicine, No.39 Shi-er-qiao Road, Chengdu, Sichuan 610075, China
| | - Sijing Zhao
- Hospital of Chengdu University of Traditional Chinese Medicine, No.39 Shi-er-qiao Road, Chengdu, Sichuan 610075, China
| | - Zherui Shen
- Hospital of Chengdu University of Traditional Chinese Medicine, No.39 Shi-er-qiao Road, Chengdu, Sichuan 610075, China
| | - Shihua Shi
- Hospital of Chengdu University of Traditional Chinese Medicine, No.39 Shi-er-qiao Road, Chengdu, Sichuan 610075, China
| | - Demei Huang
- Hospital of Chengdu University of Traditional Chinese Medicine, No.39 Shi-er-qiao Road, Chengdu, Sichuan 610075, China
| | - Yongcan Wu
- Chongqing Key Laboratory of Traditional Chinese Medicine for Prevention and Cure of Metabolic Diseases, Chongqing 400016, China; College of Traditional Chinese Medicine, Chongqing Medical University, Chongqing 400016, China
| | - Xiaomin Wang
- Hospital of Chengdu University of Traditional Chinese Medicine, No.39 Shi-er-qiao Road, Chengdu, Sichuan 610075, China
| | - Shuiqin Li
- Hospital of Chengdu University of Traditional Chinese Medicine, No.39 Shi-er-qiao Road, Chengdu, Sichuan 610075, China
| | - Yacong He
- School of Pharmacy, Chengdu University of Traditional Chinese Medicine, No.1166 Liutai Avenue, Chengdu, Sichuan 611137, China.
| | - Zhenxing Wang
- Hospital of Chengdu University of Traditional Chinese Medicine, No.39 Shi-er-qiao Road, Chengdu, Sichuan 610075, China.
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Pathophysiology and Therapy of High-Altitude Sickness: Practical Approach in Emergency and Critical Care. J Clin Med 2022; 11:jcm11143937. [PMID: 35887706 PMCID: PMC9325098 DOI: 10.3390/jcm11143937] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 06/21/2022] [Accepted: 06/24/2022] [Indexed: 12/26/2022] Open
Abstract
High altitude can be a hostile environment and a paradigm of how environmental factors can determine illness when human biological adaptability is exceeded. This paper aims to provide a comprehensive review of high-altitude sickness, including its epidemiology, pathophysiology, and treatments. The first section of our work defines high altitude and considers the mechanisms of adaptation to it and the associated risk factors for low adaptability. The second section discusses the main high-altitude diseases, highlighting how environmental factors can lead to the loss of homeostasis, compromising important vital functions. Early recognition of clinical symptoms is important for the establishment of the correct therapy. The third section focuses on high-altitude pulmonary edema, which is one of the main high-altitude diseases. With a deeper understanding of the pathogenesis of high-altitude diseases, as well as a reasoned approach to environmental or physical factors, we examine the main high-altitude diseases. Such an approach is critical for the effective treatment of patients in a hostile environment, or treatment in the emergency room after exposure to extreme physical or environmental factors.
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Elucidating the combined effect of intermittent hypoxia training and acetazolamide on hypoxia induced hematological and physiological changes. Curr Res Physiol 2022; 5:327-337. [PMID: 35880035 PMCID: PMC9307424 DOI: 10.1016/j.crphys.2022.07.004] [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: 04/04/2022] [Revised: 07/05/2022] [Accepted: 07/11/2022] [Indexed: 11/25/2022] Open
Abstract
As the number of people travelling to altitude increases, the risk of life threatening medical emergencies also increases. It is important that we have effective strategies to minimize the risk of altitude illness. In this study, an attempt was made to investigate the combined effect of non-pharmacological (Intermittent hypoxia training; IHT) and pharmacological (acetazolamide; ACZ) intervention as a prophylactic strategy in order to minimize the risk of high altitude hypoxic related problems using rats as an animal model. Male Sprague Dawley rats were subjected to IHT for 4 h consecutively for 5 days at 12% FiO2 under normobaric conditions with and without oral ACZ administration at 25 mg/kg body weight. Validation of the intervention was performed by exposing the rats to extreme hypoxia (EH) at 8% FiO2 to further assess the effect of IHT and ACZ on hypoxic acclimatization. The principal findings of this study is that the combined effect of IHT and ACZ improves the arterial oxygenation by alterations in hemodynamics and in blood gasometry, thereby resulting into an increase in the oxygen carrying capacity of the blood with increase in SpO2 (peripheral oxygen saturation). The present study showed that the combined effect of IHT with ACZ could be refined as a prophylactic measure for better outcomes during altitude ascent and rapid altitude acclimatization rather than IHT or ACZ alone. Combination of IHT with ACZ attenuates the inhibitory effect of respiratory alkalosis. It also minimizes pathological changes in hematology and blood gas. The strategy improved the oxygen carrying capacity of the blood by increasing SpO2. Thus, it leads to ventilatory Acclimatization. The combined treatment could be refined as a prophylactic measure for altitude maladies.
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Bhattacharya S, Shrimali NM, Mohammad G, Koul PA, Prchal JT, Guchhait P. Gain-of-function Tibetan PHD2 D4E;C127S variant suppresses monocyte function: A lesson in inflammatory response to inspired hypoxia. EBioMedicine 2021; 68:103418. [PMID: 34102396 PMCID: PMC8190441 DOI: 10.1016/j.ebiom.2021.103418] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 04/01/2021] [Accepted: 05/14/2021] [Indexed: 12/30/2022] Open
Abstract
Background We have previously described an evolutionarily selected Tibetan prolyl hydroxylase-2 (PHD2D4E;C127S) variant that degrades the hypoxia-inducible factor (HIFα) more efficiently and protects these highlanders from hypoxia-triggered elevation in haemoglobin concentration. High altitude is known to cause acute mountain sickness (AMS) and high-altitude pulmonary edema (HAPE) in a section of rapidly ascending non-acclimatised lowlanders. These morbidities are often accompanied by inflammatory response and exposure to hypobaric hypoxia is presumed to be the principal causative agent. We have investigated whether PHD2D4E;C127S variant is associated with prevention of hypoxia-mediated inflammatory milieu in Tibetan highlanders and therefore identify a potential target to regulate inflammation. Methods We genotyped the Tibetans using DNA isolated from whole blood. Thereafter immunophenotying was performed on PBMCs from homozygous PHD2D4E;C127S and PHD2WT individuals using flow cytometry. RNA isolated from these individuals was used to evaluate the peripheral level of important transcripts associated with immune as well as hypoxia response employing the nCounter technology. The ex-vivo findings were validated by generating monocytic cell lines (U937 cell line) expressing PHD2D4E;C127S and PHD2WT variants post depletion of endogenous PHD2. We had also collected whole blood samples from healthy travellers and travellers afflicted with AMS and HAPE to evaluate the significance of our ex-vivo and in vitro findings. Hereafter, we also attempted to resolve hypoxia-triggered inflammation in vitro as well as in vivo by augmenting the function of PHD2 using alpha-ketoglutarate (αKG), a co-factor of PHD2. Findings We report that homozygous PHD2D4E;C127S highlanders harbour less inflammatory and patrolling monocytes in circulation as compared to Tibetan PHD2WT highlanders. In response to in vitro hypoxia, secretion of IL6 and IL1β from PHD2D4E;C127S monocytes, and their chemotactic response compared to the PHD2WT are compromised, corresponding to the down-modulated expression of related signalling molecules RELA, JUN, STAT1, ATF2 and CXCR4. We verified these functional outcomes in monocytic U937 cell line engineered to express PHD2D4E;C127S and confirmed the down-modulation of the signalling molecules at protein level under hypoxia. In contrast, non-Tibetan sojourners with AMS and HAPE at high altitude (3,600 m above sea level) displayed significant increase in these inflammatory parameters. Our data henceforth underline the role of gain-of-function of PHD2 as the rate limiting factor to harness hyper-activation of monocytes in hypoxic environment. Therefore upon pre-treatment with αKG, we observed diminished inflammatory response of monocytes in vitro and reduction in leukocyte infiltration to the lungs in mice exposed to normobaric hypoxia. Interpretation Our report suggests that gain-of-function PHD2 D4E;C127S variant can therefore protect against inflammation elicited by hypobaric hypoxia. Augmentation of PHD2 activity therefore may be an important method to alleviate inflammatory response to inspired hypoxia. Funding This study is supported by the Department of Biotechnology, Government of India.
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Affiliation(s)
- Sulagna Bhattacharya
- Regional Centre for Biotechnology, National Capital Region Biotech Science Cluster, Faridabad, India; School of Biotechnology, Kalinga Institute of Industrial Technology, Orissa, India
| | - Nishith M Shrimali
- Regional Centre for Biotechnology, National Capital Region Biotech Science Cluster, Faridabad, India
| | | | - Parvaiz A Koul
- Department of Internal and Pulmonary Medicine, Sher-i-Kashmir Institute of Medical Sciences, Srinagar, India
| | - Josef T Prchal
- Department of Medicine, University of Utah School of Medicine & Huntsman Cancer Center and George E. Wahlin Veteran's Administration Medical Center, Salt Lake City, UT, USA
| | - Prasenjit Guchhait
- Regional Centre for Biotechnology, National Capital Region Biotech Science Cluster, Faridabad, India.
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Pham K, Parikh K, Heinrich EC. Hypoxia and Inflammation: Insights From High-Altitude Physiology. Front Physiol 2021; 12:676782. [PMID: 34122145 PMCID: PMC8188852 DOI: 10.3389/fphys.2021.676782] [Citation(s) in RCA: 77] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Accepted: 04/26/2021] [Indexed: 12/19/2022] Open
Abstract
The key regulators of the transcriptional response to hypoxia and inflammation (hypoxia inducible factor, HIF, and nuclear factor-kappa B, NF-κB, respectively) are evolutionarily conserved and share significant crosstalk. Tissues often experience hypoxia and inflammation concurrently at the site of infection or injury due to fluid retention and immune cell recruitment that ultimately reduces the rate of oxygen delivery to tissues. Inflammation can induce activity of HIF-pathway genes, and hypoxia may modulate inflammatory signaling. While it is clear that these molecular pathways function in concert, the physiological consequences of hypoxia-induced inflammation and how hypoxia modulates inflammatory signaling and immune function are not well established. In this review, we summarize known mechanisms of HIF and NF-κB crosstalk and highlight the physiological consequences that can arise from maladaptive hypoxia-induced inflammation. Finally, we discuss what can be learned about adaptive regulation of inflammation under chronic hypoxia by examining adaptive and maladaptive inflammatory phenotypes observed in human populations at high altitude. We aim to provide insight into the time domains of hypoxia-induced inflammation and highlight the importance of hypoxia-induced inflammatory sensitization in immune function, pathologies, and environmental adaptation.
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Affiliation(s)
| | | | - Erica C. Heinrich
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
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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: 34] [Impact Index Per Article: 11.3] [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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Swenson ER, Bärtsch P. The search for a model of high-altitude pulmonary oedema must continue. Acta Physiol (Oxf) 2021; 231:e13485. [PMID: 32344466 DOI: 10.1111/apha.13485] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 04/21/2020] [Accepted: 04/23/2020] [Indexed: 10/24/2022]
Affiliation(s)
- Erik R. Swenson
- Department of Medicine, Pulmonary and Critical Care Medicine VA Puget Sound Health Care System University of Washington Seattle WA USA
| | - Peter Bärtsch
- Sports Medicine University of Heidelberg Heidelberg Germany
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Berger MM, Hackett PH, Bärtsch P. No Relevant Analogy Between COVID-19 and Acute Mountain Sickness. High Alt Med Biol 2020; 21:315-318. [PMID: 32970479 DOI: 10.1089/ham.2020.0147] [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: 12/16/2022] Open
Abstract
Berger, Marc Moritz, Peter H. Hackett, and Peter Bärtsch. No relevant analogy between COVID-19 and acute mountain sickness. High Alt Med Biol. 21:315-318, 2020.-Clinicians and scientists have suggested therapies for coronavirus disease-19 (COVID-19) that are known to be effective for other medical conditions. A recent publication suggests that pathophysiological mechanisms underlying acute mountain sickness (a syndrome of nonspecific neurological symptoms typically experienced by nonacclimatized individuals at altitudes >2500 m) may overlap with the mechanisms causing COVID-19. In this short review, we briefly evaluate this mistaken analogy and demonstrate that this concept is not supported by scientific evidence.
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Affiliation(s)
- Marc Moritz Berger
- Department of Anesthesiology and Intensive Care Medicine, University Hospital Essen, Essen, Germany
| | - Peter H Hackett
- Altitude Research Center, Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Peter Bärtsch
- Department of Internal Medicine, University of Heidelberg, Heidelberg, Germany
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10
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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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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: 10] [Impact Index Per Article: 2.5] [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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12
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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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13
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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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14
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Swallow-breathing coordination during incremental ascent to altitude. Respir Physiol Neurobiol 2018; 265:121-126. [PMID: 29920337 DOI: 10.1016/j.resp.2018.06.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Revised: 06/11/2018] [Accepted: 06/12/2018] [Indexed: 12/26/2022]
Abstract
Swallow and breathing are highly coordinated behaviors reliant on shared anatomical space and neural pathways. Incremental ascent to high altitudes results in hypoxia/hypocapnic conditions altering respiratory drive, however it is not known whether these changes also alter swallow. We examined the effect of incremental ascent (1045 m, 3440 m and 4371 m) on swallow motor pattern and swallow-breathing coordination in seven healthy adults. Submental surface electromyograms (sEMG) and spirometry were used to evaluate swallow triggered by saliva and water infusion. Swallow-breathing phase preference was different between swallows initiated by saliva versus water. With ascent, saliva swallows changed to a dominate pattern of occurrence during the transition from inspiration to expiration. Additionally, water swallows demonstrated a significant decrease in submental sEMG duration and a shift in submental activity to earlier in the apnea period, especially at 4371 m. Our results suggest that there are changes in swallow-breathing coordination and swallow production that likely increase airway protection with incremental ascent to high altitude. The adaptive changes in swallow were likely due to the exposure to hypoxia and hypocapnia, along with airway irritation.
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15
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Abstract
Crosstalk signaling between the closely juxtaposed epithelial and endothelial membranes of pulmonary alveoli establishes the lung's immune defense against inhaled and blood-borne pathogens. The crosstalk can occur in a forward direction, as from alveolus to capillary, or in a reverse direction, as from capillary to alveolus. The crosstalk direction likely depends on the site at which pathogens first initiate signaling. Thus, forward crosstalk may occur when inhaled pathogens encounter the alveolar epithelium, while reverse crosstalk may result from interactions of blood-borne pathogens with the endothelium. Here, we review the factors that regulate these two directions of signaling.
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Affiliation(s)
- Rebecca F Hough
- 1 Lung Biology Lab, Columbia University College of Physicians & Surgeons, New York, NY, USA.,2 Department of Pediatrics, Columbia University College of Physicians & Surgeons, New York, NY, USA
| | - Sunita Bhattacharya
- 1 Lung Biology Lab, Columbia University College of Physicians & Surgeons, New York, NY, USA.,2 Department of Pediatrics, Columbia University College of Physicians & Surgeons, New York, NY, USA
| | - Jahar Bhattacharya
- 1 Lung Biology Lab, Columbia University College of Physicians & Surgeons, New York, NY, USA.,3 Department of Medicine, Columbia University College of Physicians & Surgeons, New York, NY, USA
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16
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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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17
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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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18
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Droma Y, Kato A, Ichiyama T, Kobayashi N, Honda T, Uehara T, Hanaoka M. Electron Microscopy Observation of Human Pulmonary Ultrastructure in Two Patients with High-Altitude Pulmonary Edema. High Alt Med Biol 2017; 18:288-291. [PMID: 28876136 DOI: 10.1089/ham.2016.0163] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We examined the pulmonary ultrastructure in tissue from two patients with high-altitude pulmonary edema (HAPE) by electron microscopy. In one case, we found that neutrophils were trapped in pulmonary capillary lumen of alveolar-capillary wall and part of the cytoplasm of a neutrophil protruded and adhered to the capillary endothelium. There were several degranulated vacuoles in the cytoplasm of the neutrophil. The pulmonary capillary wall was deformed, thickened, and swollen and there was evidence of degeneration. In another case, infiltration of neutrophils and macrophages, proliferation of type II pneumocytes, and numerous red blood cells were also observed in alveolar air space. These electron microscopic ultrastructural observations illustrate for the first time damage to the pulmonary alveolar-capillary barrier in lung tissue of humans with advanced HAPE.
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Affiliation(s)
- Yunden Droma
- 1 First Department of Medicine, Shinshu University School of Medicine , Matsumoto, Japan
| | - Akane Kato
- 1 First Department of Medicine, Shinshu University School of Medicine , Matsumoto, Japan
| | - Takashi Ichiyama
- 1 First Department of Medicine, Shinshu University School of Medicine , Matsumoto, Japan
| | - Nobumitsu Kobayashi
- 1 First Department of Medicine, Shinshu University School of Medicine , Matsumoto, Japan
| | - Takayuki Honda
- 2 Department of Laboratory Medicine, Shinshu University School of Medicine , Matsumoto, Japan
| | - Takeshi Uehara
- 2 Department of Laboratory Medicine, Shinshu University School of Medicine , Matsumoto, Japan
| | - Masayuki Hanaoka
- 1 First Department of Medicine, Shinshu University School of Medicine , Matsumoto, Japan
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19
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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: 230] [Impact Index Per Article: 32.9] [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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20
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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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21
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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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22
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Swenson ER. Pharmacology of acute mountain sickness: old drugs and newer thinking. J Appl Physiol (1985) 2015; 120:204-15. [PMID: 26294748 DOI: 10.1152/japplphysiol.00443.2015] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 08/12/2015] [Indexed: 01/09/2023] Open
Abstract
Pharmacotherapy in acute mountain sickness (AMS) for the past half century has largely rested on the use of carbonic anhydrase (CA) inhibitors, such as acetazolamide, and corticosteroids, such as dexamethasone. The benefits of CA inhibitors are thought to arise from their known ventilatory stimulation and resultant greater arterial oxygenation from inhibition of renal CA and generation of a mild metabolic acidosis. The benefits of corticosteroids include their broad-based anti-inflammatory and anti-edemagenic effects. What has emerged from more recent work is the strong likelihood that drugs in both classes act on other pathways and signaling beyond their classical actions to prevent and treat AMS. For the CA inhibitors, these include reduction in aquaporin-mediated transmembrane water transport, anti-oxidant actions, vasodilation, and anti-inflammatory effects. In the case of corticosteroids, these include protection against increases in vascular endothelial and blood-brain barrier permeability, suppression of inflammatory cytokines and reactive oxygen species production, and sympatholysis. The loci of action of both classes of drug include the brain, but may also involve the lung as revealed by benefits that arise with selective administration to the lungs by inhalation. Greater understanding of their pluripotent actions and sites of action in AMS may help guide development of better drugs with more selective action and fewer side effects.
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Affiliation(s)
- Erik R Swenson
- Veterans Affairs Puget Sound Health Care System, Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Washington, Seattle
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23
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Mishra A, Mohammad G, Norboo T, Newman JH, Pasha MAQ. Lungs at high-altitude: genomic insights into hypoxic responses. J Appl Physiol (1985) 2015; 119:1-15. [DOI: 10.1152/japplphysiol.00513.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 04/20/2015] [Indexed: 11/22/2022] Open
Abstract
Hypobaric hypoxia at high altitude (HA) results in reduced blood arterial oxygen saturation, perfusion of organs with hypoxemic blood, and direct hypoxia of lung tissues. The pulmonary complications in the cells of the pulmonary arterioles due to hypobaric hypoxia are the basis of the pathophysiological mechanisms of high-altitude pulmonary edema (HAPE). Some populations that have dwelled at HA for thousands of years have evolutionarily adapted to this environmental stress; unadapted populations may react with excessive physiological responses that impair health. Individual variations in response to hypoxia and the mechanisms of HA adaptation provide insight into physiological responses. Adaptive and maladaptive responses include alterations in pathways such as oxygen sensing, hypoxia signaling, K+- and Ca2+-gated channels, redox balance, and the renin-angiotensin-aldosterone system. Physiological imbalances are linked with genetic susceptibilities, and nonhomeostatic responses in gene regulation that occur by small RNAs, histone modification, and DNA methylation predispose susceptible humans to these HA illnesses. Elucidation of the interaction of these factors will lead to a more comprehensive understanding of HA adaptations and maladaptations and will lead to new therapeutics for HA disorders related to hypoxic lungs.
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Affiliation(s)
- Aastha Mishra
- Department of Genomics and Molecular Medicine, Genomics and Molecular Medicine, CSIR-Institute of Genomics and Integrative Biology, Delhi, India
- Department of Biotechnology, University of Pune, Pune, India
| | - Ghulam Mohammad
- Department of Medicine, SNM Hospital, Leh, Ladakh, J&K, India
| | - Tsering Norboo
- Ladakh Institute of Prevention, Leh, Ladakh, J&K, India; and
| | - John H. Newman
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - M. A. Qadar Pasha
- Department of Genomics and Molecular Medicine, Genomics and Molecular Medicine, CSIR-Institute of Genomics and Integrative Biology, Delhi, India
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24
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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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25
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Zheng CR, Chen GZ, Yu J, Qin J, Song P, Bian SZ, Xu BD, Tang XG, Huang YT, Liang X, Yang J, Huang L. Inhaled budesonide and oral dexamethasone prevent acute mountain sickness. Am J Med 2014; 127:1001-1009.e2. [PMID: 24784698 DOI: 10.1016/j.amjmed.2014.04.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 04/07/2014] [Accepted: 04/11/2014] [Indexed: 02/05/2023]
Abstract
BACKGROUND This double-blind, randomized controlled trial aimed to investigate inhaled budesonide and oral dexamethasone compared with placebo for their prophylactic efficacy against acute mountain sickness after acute high-altitude exposure. METHODS There were 138 healthy young male lowland residents recruited and randomly assigned to receive inhaled budesonide (200 μg, twice a day [bid]), oral dexamethasone (4 mg, bid), or placebo (46 in each group). They traveled to 3900 m altitude from 400 m by car. Medication started 1 day before high-altitude exposure and continued until the third day of exposure. Primary outcome measure was the incidence of acute mountain sickness after exposure. RESULTS One hundred twenty-four subjects completed the study (42, 39, and 43 in the budesonide, dexamethasone, and placebo groups, respectively). Demographic characteristics were comparable among the 3 groups. After high-altitude exposure, significantly fewer participants in the budesonide (23.81%) and dexamethasone (30.77%) groups developed acute mountain sickness compared with participants receiving placebo (60.46%) (P = .0006 and P = .0071, respectively). Both the budesonide and dexamethasone groups had lower heart rate and higher pulse oxygen saturation (SpO2) than the placebo group at altitude. Only the budesonide group demonstrated less deterioration in forced vital capacity and sleep quality than the placebo group. Four subjects in the dexamethasone group reported adverse reactions. CONCLUSIONS Both inhaled budesonide (200 μg, bid) and oral dexamethasone (4 mg, bid) were effective for the prevention of acute mountain sickness, especially its severe form, compared with placebo. Budesonide caused fewer adverse reactions than dexamethasone.
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Affiliation(s)
- Cheng-Rong Zheng
- Institute of Cardiovascular Science, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Guo-Zhu Chen
- Institute of Cardiovascular Science, Xinqiao Hospital, Third Military Medical University, Chongqing, China; PLA Institute of Cardiovascular Disease, Chongqing, China
| | - Jie Yu
- Institute of Cardiovascular Science, Xinqiao Hospital, Third Military Medical University, Chongqing, China; PLA Institute of Cardiovascular Disease, Chongqing, China
| | - Jun Qin
- Institute of Cardiovascular Science, Xinqiao Hospital, Third Military Medical University, Chongqing, China; PLA Institute of Cardiovascular Disease, Chongqing, China
| | - Pan Song
- Institute of Cardiovascular Science, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Shi-Zhu Bian
- Institute of Cardiovascular Science, Xinqiao Hospital, Third Military Medical University, Chongqing, China; PLA Institute of Cardiovascular Disease, Chongqing, China
| | - Bai-Da Xu
- Institute of Cardiovascular Science, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Xu-Gang Tang
- Institute of Cardiovascular Science, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Yong-Tao Huang
- Institute of Cardiovascular Science, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Xiao Liang
- Institute of Cardiovascular Science, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Jie Yang
- Institute of Cardiovascular Science, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Lan Huang
- Institute of Cardiovascular Science, Xinqiao Hospital, Third Military Medical University, Chongqing, China; PLA Institute of Cardiovascular Disease, Chongqing, China.
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26
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The lungs in acute mountain sickness: victim, perpetrator, or both? Am J Med 2014; 127:899-900. [PMID: 24950487 DOI: 10.1016/j.amjmed.2014.06.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 06/11/2014] [Accepted: 06/11/2014] [Indexed: 11/23/2022]
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27
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Yang Y, Ma L, Guan W, Wang Y, DU Y, Ga Q, Ge RL. Differential plasma proteome analysis in patients with high-altitude pulmonary edema at the acute and recovery phases. Exp Ther Med 2014; 7:1160-1166. [PMID: 24940404 PMCID: PMC3991535 DOI: 10.3892/etm.2014.1548] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 01/17/2014] [Indexed: 11/22/2022] Open
Abstract
This study aimed to investigate the differential expression of plasma proteins in patients suffering from high-altitude pulmonary edema (HAPE) at different phases. A complete proteomic analysis was performed using two-dimensional gel electrophoresis followed by mass spectrometry in three patients with HAPE at the acute stage and recovery phase. Comparisons between the expression patterns of the patients with HAPE at the two different phases led to the identification of eight protein spots with a >1.5-fold difference in expression between the acute and recovery phases. These differentially expressed proteins were apolipoproteins, serum amyloid P component, complement components and others. Apolipoprotein A-I (Apo A-I), serum amyloid P component and fibrinogen were overexpressed in the patients with HAPE in the acute stage compared with their expression levels in the recovery phase. However, Apo A-IV and antithrombin-III were overexpressed in the patients with HAPE in the recovery phase compared with their expression levels in the acute stage. The results indicate that the differential plasma proteome in patients with HAPE may be associated with the occurrence of HAPE, and the expression changes of Apo A-I and A-IV may offer further understanding of HAPE to aid its prognosis, diagnosis and treatment.
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Affiliation(s)
- Yingzhong Yang
- Research Center for High Altitude Medical Sciences, Qinghai University School of Medicine, Xining, Qinghai 810001, P.R. China
| | - Lan Ma
- Research Center for High Altitude Medical Sciences, Qinghai University School of Medicine, Xining, Qinghai 810001, P.R. China
| | - Wei Guan
- Research Center for High Altitude Medical Sciences, Qinghai University School of Medicine, Xining, Qinghai 810001, P.R. China ; Department of Respiratory Medicine, Qinghai University Affiliated Hospital, Xining, Qinghai 810001, P.R. China
| | - Yaping Wang
- Research Center for High Altitude Medical Sciences, Qinghai University School of Medicine, Xining, Qinghai 810001, P.R. China
| | - Yang DU
- Research Center for High Altitude Medical Sciences, Qinghai University School of Medicine, Xining, Qinghai 810001, P.R. China
| | - Qin Ga
- Research Center for High Altitude Medical Sciences, Qinghai University School of Medicine, Xining, Qinghai 810001, P.R. China
| | - Ri-Li Ge
- Research Center for High Altitude Medical Sciences, Qinghai University School of Medicine, Xining, Qinghai 810001, P.R. China
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28
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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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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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Lattuada M, Bergquist M, Maripuu E, Hedenstierna G. Mechanical ventilation worsens abdominal edema and inflammation in porcine endotoxemia. Crit Care 2013; 17:R126. [PMID: 23799965 PMCID: PMC4056092 DOI: 10.1186/cc12801] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 06/24/2013] [Indexed: 11/10/2022] Open
Abstract
INTRODUCTION We hypothesized that mechanical ventilation per se increases abdominal edema and inflammation in sepsis and tested this in experimental endotoxemia. METHODS Thirty anesthetized piglets were allocated to one of five groups: healthy control pigs breathing spontaneously with continuous positive pressure of 5 cm H2O or mechanically ventilated with positive end-expiratory pressure of 5 cm H2O, and endotoxemic piglets during mechanical ventilation for 2.5 hours and then continued on mechanical ventilation with positive end-expiratory pressure of either 5 or 15 cm H2O or switched to spontaneous breathing with continuous positive pressure of 5 cm H2O for another 2.5 hours. Abdominal edema formation was estimated by isotope technique, and inflammatory markers were measured in liver, intestine, lung, and plasma. RESULTS Healthy controls: 5 hours of spontaneous breathing did not increase abdominal fluid, whereas mechanical ventilation did (Normalized Index increased from 1.0 to 1.6; 1 to 3.3 (median and range, P<0.05)). Endotoxemic animals: Normalized Index increased almost sixfold after 5 hours of mechanical ventilation (5.9; 4.9 to 6.9; P<0.05) with twofold increase from 2.5 to 5 hours whether positive end-expiratory pressure was 5 or 15, but only by 40% with spontaneous breathing (P<0.05 versus positive end-expiratory pressure of 5 or 15 cm H2O). Tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 in intestine and liver were 2 to 3 times higher with mechanical ventilation than during spontaneous breathing (P<0.05) but similar in plasma and lung. Abdominal edema formation and TNF-α in intestine correlated inversely with abdominal perfusion pressure. CONCLUSIONS Mechanical ventilation with positive end-expiratory pressure increases abdominal edema and inflammation in intestine and liver in experimental endotoxemia by increasing systemic capillary leakage and impeding abdominal lymph drainage.
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Burki NK, Tetenta SU. Inflammatory response to acute hypoxia in humans. Pulm Pharmacol Ther 2013; 27:208-11. [PMID: 23727146 DOI: 10.1016/j.pupt.2013.05.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 05/01/2013] [Accepted: 05/21/2013] [Indexed: 11/29/2022]
Abstract
BACKGROUND In animal studies hypoxia is known to cause an inflammatory response, inducing multiple transcription factors and activating molecular processes at the cellular level. However, it is not known whether acute hypoxia causes similar inflammatory effects in humans, although such an assumption is commonly made. METHODS The effects of acute hypoxic exposure were studied in 12 healthy adults: Each subject was studied on 2 different days. Group 1 (mean age 33 ± 5.5 years; 2 females, 4 males) was exposed either to a hypoxic gas mixture or room air for 30 min and Group 2 (mean age 26.5 ± 7.5 years; 3 females, 3 males) for 60 min. Measurements of circulating adhesion molecules (AMs), Clara cell secretory protein (CC16), hypoxia inducible factor 1α (HIF-1α), vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), tumor necrosis factor (TNF-α), and C reactive protein (hsCRP) were made at baseline and at intervals following exposure for 240 min. RESULTS No significant changes were seen in circulating AMs, CC16, TNF-α, IL-6 or hsCRP, although both HIF-1α and VEGF levels increased significantly (p < 0.05) after hypoxic exposure. CONCLUSIONS Acute hypoxic exposure in normal man does not induce a measurable change in inflammatory or epithelial biomarkers, in contrast to studies at the cellular level in animals. However, acute hypoxic exposure does induce the expression of HIF-1α and VEGF. These results indicate that in humans acute hypoxic exposure for up to 60 min does not induce a generalized inflammatory response, indicating that the human response to hypoxia is more complex than inferred from animal/cellular studies.
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Affiliation(s)
- Nausherwan K Burki
- Division of Pulmonary & Critical Care Medicine, University of Connecticut Health Center, Farmington, CT 06030-1321, USA.
| | - Sodienye U Tetenta
- Division of Pulmonary & Critical Care Medicine, University of Connecticut Health Center, Farmington, CT 06030-1321, USA.
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Bouzat P, Walther G, Rupp T, Doucende G, Payen JF, Levy P, Verges S. Time course of asymptomatic interstitial pulmonary oedema at high altitude. Respir Physiol Neurobiol 2013; 186:16-21. [DOI: 10.1016/j.resp.2012.12.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 11/20/2012] [Accepted: 12/11/2012] [Indexed: 12/21/2022]
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Wang CT, Lin HJ, Cheng BC, Lin MT, Chang CP. Attenuating systemic inflammatory markers in simulated high-altitude exposure by heat shock protein 70-mediated hypobaric hypoxia preconditioning in rats. J Formos Med Assoc 2013; 114:328-38. [PMID: 25839766 DOI: 10.1016/j.jfma.2012.11.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 10/22/2012] [Accepted: 11/23/2012] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND/PURPOSE The primary goal of this study was to test whether high-altitude exposure (HAE: 0.9% O(2) at 0.47 ATA for 24 hours) was capable of increasing the systemic inflammatory markers as well as the toxic organ injury indicators in rats, with a secondary goal to test whether preinduction of heat shock protein (HSP) 70 by hypobaric hypoxia preconditioning (HHP: 18.3% O(2) at 0.66 ATA for 5 h/day on 5 days consecutively for 2 weeks) attenuated the proposed increased serum levels of both the systemic inflammatory markers and the toxic organ injury indicators. METHODS Rats were assigned to: (1) non-HHP (21% O(2) at 1.0 ATA)+non-HAE (21% O(2) at 1.0 ATA) group; (2) non-HHP+HAE group; (3) HHP+non-HAE group; (4) HHP+HAE group; and (5) HHP+HSP70 antibodies (Ab)+HAE group. For the HSP70Ab group, a neutralizing HSP70Ab was injected intravenously at 24 hours prior to HAE. All the physiological and biochemical parameters were obtained at the end of HAE or the equivalent time period of non-HAE. Blood samples were obtained for determination of both the systemic inflammatory markers (e.g., serum tumor necrosis factor-α, interleukin-1β, E-selectin, intercellular adhesion molecule-1, and liver myeloperoxidase activity) and the toxic organ injury indicators (e.g., nitric oxide metabolites, 2,3-dihydroxybenzoic acid, and lactate dehydrogenase). RESULTS HHP, in addition to inducing overexpression of tissue HSP70, significantly attenuated the HAE-induced hypotension, bradycardia, hypoxia, acidosis, and increased tissue levels of both the systemic inflammatory markers and the toxic organ injury indicators. The beneficial effects of HHP in inducing tissue overexpression of HSP70 as well as in preventing the HAE-induced increased levels of the systemic inflammatory markers and the toxic organ injury indicators could be significantly reduced by HSP70Ab preconditioning. CONCLUSION These results suggest that HHP may downgrade both the systemic inflammatory markers and the toxic organ injury indicators in HAE by upregulating tissue HSP70.
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Affiliation(s)
- Chia-Ti Wang
- Department of Emergency Medicine, Chi Mei Medical Center, Tainan, Taiwan
| | - Hung-Jung Lin
- Department of Emergency Medicine, Chi Mei Medical Center, Tainan, Taiwan; Department of Biotechnology, Southern Taiwan University of Science and Technology, Tainan, Taiwan
| | - Bor-Chih Cheng
- Department of Biotechnology, Southern Taiwan University of Science and Technology, Tainan, Taiwan; Department of Surgery, Chi Mei Medical Center, Tainan, Taiwan
| | - Mao-Tsun Lin
- Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan
| | - Ching-Ping Chang
- Department of Biotechnology, Southern Taiwan University of Science and Technology, Tainan, Taiwan.
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Huertas A, Das SR, Emin M, Sun L, Rifkind JM, Bhattacharya J, Bhattacharya S. Erythrocytes induce proinflammatory endothelial activation in hypoxia. Am J Respir Cell Mol Biol 2012; 48:78-86. [PMID: 23043086 DOI: 10.1165/rcmb.2011-0402oc] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Although exposure to ambient hypoxia is known to cause proinflammatory vascular responses, the mechanisms initiating these responses are not understood. We tested the hypothesis that in systemic hypoxia, erythrocyte-derived H(2)O(2) induces proinflammatory gene transcription in vascular endothelium. We exposed mice or isolated, perfused murine lungs to 4 hours of hypoxia (8% O(2)). Leukocyte counts increased in the bronchoalveolar lavage. The expression of leukocyte adhesion receptors, reactive oxygen species, and protein tyrosine phosphorylation increased in freshly recovered lung endothelial cells (FLECs). These effects were inhibited by extracellular catalase and by the removal of erythrocytes, indicating that the responses were attributable to erythrocyte-derived H(2)O(2). Concomitant nuclear translocation of the p65 subunit of NF-κB and hypoxia-inducible factor-1α stabilization in FLECs occurred only in the presence of erythrocytes. Hemoglobin binding to the erythrocyte membrane protein, band 3, induced the release of H(2)O(2) from erythrocytes and the p65 translocation in FLECs. These data indicate for the first time, to our knowledge, that erythrocytes are responsible for endothelial transcriptional responses in hypoxia.
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Affiliation(s)
- Alice Huertas
- Lung Biology Laboratory, Pulmonary Division, Department of Medicine, Columbia University Medical Center, New York, NY 10032, USA
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Kylhammar D, Rådegran G. Cyclooxygenase-2 inhibition and thromboxane A(2) receptor antagonism attenuate hypoxic pulmonary vasoconstriction in a porcine model. Acta Physiol (Oxf) 2012; 205:507-19. [PMID: 22554045 DOI: 10.1111/j.1748-1716.2012.02437.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Revised: 12/12/2011] [Accepted: 03/17/2012] [Indexed: 11/30/2022]
Abstract
AIM Hypoxic pulmonary vasoconstriction (HPV) causes pulmonary hypertension that may lead to right heart failure. We hypothesized that the COX-2 inhibitor nimesulide and the thromboxane A(2) receptor antagonist daltroban would attenuate HPV. METHODS Haemodynamic measurements and blood sampling were performed in 18 anaesthetized, mechanically ventilated pigs, with mean ± SEM weights of 31.3 ± 0.6 kg, in normoxia (F(i)O(2)~0.21) and hypoxia (F(i)O(2)~0.10), before and 5, 15 and 45 min after initiation of right atrial infusion of nimesulide (n = 6) or daltroban (n = 6), respectively, and in six control pigs. RESULTS Compared with normoxia, hypoxia (n = 18) increased mean pulmonary artery pressure by 15.8 ± 0.8 mmHg (P < 0.001), pulmonary vascular resistance (PVR) by 2.7 ± 0.3 WU (P < 0.05) and mean right atrial pressure by 2.3 ± 0.3 mmHg (P < 0.001). In the control pigs, mean pulmonary artery pressure, PVR and mean right atrial pressure remained stable (P = ns) throughout 45 min hypoxia, compared with hypoxia baseline. Nimesulide decreased mean pulmonary artery pressure by 3.7 ± 1.3 mmHg after 45 min (P < 0.013), as well as PVR by 0.8 ± 0.2 WU (P < 0.05), levelling off after 15 min. Daltroban transiently increased (P < 0.001) mean pulmonary artery pressure and mean right atrial pressure by 7.2 ± 1.2 and 2.7 ± 0.4 mmHg, respectively, but they returned to hypoxia baseline (P = ns) within 5 min. Daltroban then decreased mean pulmonary artery pressure to after 45 min be 4.2 ± 1.6 mmHg lower (P < 0.005) than at hypoxia baseline. CONCLUSION COX-2 inhibition and thromboxane A(2) receptor antagonism attenuate HPV by decreasing mean pulmonary artery pressure by approximately 10-11%, as measured 45 min after initiation of nimesulide or daltroban infusion respectively.
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Affiliation(s)
- D Kylhammar
- The Öresund Cardiovascular Research Collaboration, The Clinic for Heart Failure and Valvular Disease, Skåne University Hospital, Lund, Sweden.
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S K S S, Veeramohan, P H, Mathew T, S S, M C. Nifedipine inhibits hypoxia induced transvascular leakage through down regulation of NFkB. Respir Physiol Neurobiol 2012; 183:26-34. [PMID: 22627105 DOI: 10.1016/j.resp.2012.05.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2011] [Revised: 05/15/2012] [Accepted: 05/15/2012] [Indexed: 10/28/2022]
Abstract
We have studied the prophylactic administration of nifedipine and its molecular mechanism involved in reducing the transvascular leakage and inflammation in rats under hypoxia. Rats exposed to an altitude of 7620m for 6h resulted into significant increase in transvascular leakage, oxidative stress with increased NFkB expression in lungs followed by significant increase in pro inflammatory cytokines (IL-1, TNF-α) with up regulation of cell adhesion molecules (ICAM-I, VCAM-I, E-selectin, and P-selectin) in the lungs over control. Prophylactic administration of nifedipine significantly reduced the transvascular leakage, oxidative stress, inhibited the up regulation of NFkB in lungs of rats compared to control. In addition, nifedipine significantly suppressed the levels of proinflammatory cytokines and cell adhesion molecules and stabilized the HIF1-α accumulation in the lungs of rats compared to control. These results indicate that, nifedipine has an inhibitory effect on initial leaking and showed reduction in progression of inflammation through down regulation of NFkB activity in lungs of rats under hypoxia.
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Affiliation(s)
- Sarada S K S
- Department of Experimental Biology, Defence Institute of Physiology and Allied Sciences, Lucknow Road, Timarpur, Delhi 54, India.
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van Patot MCT, Gassmann M. Hypoxia: adapting to high altitude by mutating EPAS-1, the gene encoding HIF-2α. High Alt Med Biol 2012; 12:157-67. [PMID: 21718164 DOI: 10.1089/ham.2010.1099] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Living at high altitude is demanding and thus drives adaptational mechanisms. The Tibetan population has had a longer evolutionary period to adapt to high altitude than other mountain populations such as Andeans. As a result, some Tibetans living at high altitudes do not show markedly elevated red blood cell production as compared to South American high altitude natives such as Quechuas or Aymaras, thereby avoiding high blood viscosity creating cardiovascular risk. Unexpectedly, the responsible mutation(s) reducing red blood cell production do not involve either the gene encoding the blood hormone erythropoietin (Epo), or the corresponding regulatory sequences flanking the Epo gene. Similarly, functional mutations in the hypoxia-inducible transcription factor 1α (HIF-1α) gene that represents the oxygen-dependent subunit of the HIF-1 heterodimer, the latter being the main regulator of over 100 hypoxia-inducible genes, have not been described so far. It was not until very recently that three independent groups showed that the gene encoding HIF-2α, EPAS-1 (Wenger et al. 1997), represents a key gene mutated in Tibetan populations adapted to living at high altitudes (Beall et al. 2010 , Yi et al. 2010 , Simonson et al. 2010). Hypoxia-inducible transcription factors were first identified by the description of HIF-1 (Semenza et al. 1991 , 1992), which was subsequently found to enhance transcription of multiple genes that encode proteins necessary for rescuing from hypoxic exposure, including erythropoietic, angiogenic and glycolytic proteins. Then HIF-2 was identified (Ema et al. 1997 ; Flamme et al. 1997 ; Hogenesch et al. 1997 ; and Tian et al. 1997) and although it is highly similar to HIF-1 and has the potential to bind (Camenisch et al. 2001) and mediate (Mole et al. 2009) many of the same genes as HIF-1, its biological actions in response to hypoxia are distinct from those of HIF-1 (reviewed by Loboda et al. 2010). By now, several of these HIF-2 mediated processes have been implicated in the human response to high altitude exposure including erythropoiesis (Kapitsinou et al. 2010), iron homeostasis (Peyssonnaux et al. 2008), metabolism (Shohet et al. 2007; Tormos et al. 2010; Biswas et al. 2010 ; Rankin et al. 2009) and vascular permeability (Chen et al. 2009; Tanaka et al. 2005), among others. Clearly, mutation of EPAS-1 has the potential to bring far more advantage when adapting to high altitude than solely mutating the Epo gene.
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Affiliation(s)
- Martha C Tissot van Patot
- Institute of Veterinary Physiology, Vetsuisse Faculty and Zurich Center for Integrative Human Physiology (ZIHP), University of Zürich, Zürich, Switzerland
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Abstract
It has been known for more than 60 years, and suspected for over 100, that alveolar hypoxia causes pulmonary vasoconstriction by means of mechanisms local to the lung. For the last 20 years, it has been clear that the essential sensor, transduction, and effector mechanisms responsible for hypoxic pulmonary vasoconstriction (HPV) reside in the pulmonary arterial smooth muscle cell. The main focus of this review is the cellular and molecular work performed to clarify these intrinsic mechanisms and to determine how they are facilitated and inhibited by the extrinsic influences of other cells. Because the interaction of intrinsic and extrinsic mechanisms is likely to shape expression of HPV in vivo, we relate results obtained in cells to HPV in more intact preparations, such as intact and isolated lungs and isolated pulmonary vessels. Finally, we evaluate evidence regarding the contribution of HPV to the physiological and pathophysiological processes involved in the transition from fetal to neonatal life, pulmonary gas exchange, high-altitude pulmonary edema, and pulmonary hypertension. Although understanding of HPV has advanced significantly, major areas of ignorance and uncertainty await resolution.
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Affiliation(s)
- J. T. Sylvester
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
| | - Larissa A. Shimoda
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
| | - Philip I. Aaronson
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
| | - Jeremy P. T. Ward
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
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Tourigny PD, Hall C. Diagnosis and management of environmental thoracic emergencies. Emerg Med Clin North Am 2011; 30:501-28, x. [PMID: 22487116 DOI: 10.1016/j.emc.2011.10.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
Physiologic sequelae from increasing ambient pressure in underwater activities, decreasing ambient pressure while at altitude, or the consequences of drowning present a unique set of challenges to emergency physicians. In addition, several environmental toxins cause significant respiratory morbidity, whether they be pulmonary irritants, simple asphyxiants, or systemic toxins. It is important for emergency physicians to understand the pathophysiology of these illnesses as well as to apply this knowledge to the clinical arena either in the prehospital setting or in the emergency department. Current treatment paradigms and controversies within these regimens are discussed.
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Affiliation(s)
- Paul D Tourigny
- Division of Emergency Medicine, Foothills Medical Centre, University of Calgary, 1403-29 Street Northwest, Calgary, Alberta, Canada.
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Rodway GW, McIntosh SE, Dow J. Mountain Research and Rescue on Denali: A Short History from the 1980s to the Present. High Alt Med Biol 2011; 12:277-83. [DOI: 10.1089/ham.2010.1063] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- George W. Rodway
- University of Utah College of Nursing and School of Medicine, Salt Lake City, Utah, USA
| | - Scott E. McIntosh
- University of Utah Division of Emergency Medicine and School of Medicine, Salt Lake City, Utah, USA
| | - Jennifer Dow
- Denali National Park and Preserve, Alaska Regional Hospital, Anchorage, Alaska, USA
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Identification of haptoglobin and apolipoprotein A-I as biomarkers for high altitude pulmonary edema. Funct Integr Genomics 2011; 11:407-17. [DOI: 10.1007/s10142-011-0234-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 06/15/2011] [Accepted: 06/26/2011] [Indexed: 11/25/2022]
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Yuan JXJ, Garcia JG, West JB, Hales CA, Rich S, Archer SL. High-Altitude Pulmonary Edema. TEXTBOOK OF PULMONARY VASCULAR DISEASE 2011. [PMCID: PMC7122766 DOI: 10.1007/978-0-387-87429-6_61] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
High-altitude pulmonary edema (HAPE) is an uncommon form of pulmonary edema that occurs in healthy individuals within a few days of arrival at altitudes above 2,500–3,000 m. The crucial pathophysiology is an excessive hypoxia-mediated rise in pulmonary vascular resistance (PVR) or hypoxic pulmonary vasoconstriction (HPV) leading to increased microvascular hydrostatic pressures despite normal left atrial pressure. The resultant hydrostatic stress can cause both dynamic changes in the permeability of the alveolar capillary barrier and mechanical damage leading to leakage of large proteins and erythrocytes into the alveolar space in the absence of inflammation. Bronchoalveolar lavage (BAL) and pulmonary artery (PA) and microvascular pressure measurements in humans confirm that high capillary pressure induces a high-permeability non-inflammatory-type lung edema; a concept termed “capillary stress failure.” Measurements of endothelin and nitric oxide (NO) in exhaled air, NO metabolites in BAL fluid, and NO-dependent endothelial function in the systemic circulation all point to reduced NO availability and increased endothelin in hypoxia as a major cause of the excessive hypoxic PA pressure rise in HAPE-susceptible individuals. Other hypoxia-dependent differences in ventilatory control, sympathetic nervous system activation, endothelial function, and alveolar epithelial sodium and water reabsorption likely contribute additionally to the phenotype of HAPE susceptibility. Recent studies using magnetic resonance imaging in humans strongly suggest nonuniform regional hypoxic arteriolar vasoconstriction as an explanation for how HPV occurring predominantly at the arteriolar level can cause leakage. This compelling but not yet fully proven mechanism predicts that in areas of high blood flow due to lesser vasoconstriction edema will develop owing to pressures that exceed the structural and dynamic capacity of the alveolar capillary barrier to maintain normal alveolar fluid balance. Numerous strategies aimed at lowering HPV and possibly enhancing active alveolar fluid reabsorption are effective in preventing and treating HAPE. Much has been learned about HAPE in the past four decades such that what was once a mysterious alpine malady is now a well-characterized and preventable lung disease. This chapter will relate the history, pathophysiology, and treatment of HAPE, using it not only to illuminate the condition, but also for the broader lessons it offers in understanding pulmonary vascular regulation and lung fluid balance.
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Affiliation(s)
- Jason X. -J. Yuan
- Departments of Medicine, COMRB Rm. 3131 (MC 719), University of Illinois at Chicago, 909 South Wolcott Avenue, Chicago, 60612 Illinois USA
| | - Joe G.N. Garcia
- 310 Admin.Office Building (MC 672), University of Illinois at Chicago, 1737 W. Polk Street, Suite 310, Chicago, 60612 Illinois USA
| | - John B. West
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, 92093-0623 California USA
| | - Charles A. Hales
- Dept. Pulmonary & Critical Care Medicine, Massachusetts General Hospital, 55 Fruit Street, Boston, 02114 Massachusetts USA
| | - Stuart Rich
- Department of Medicine, University of Chicago Medical Center, 5841 S. Maryland Ave., Chicago, 60637 Illinois USA
| | - Stephen L. Archer
- Department of Medicine, University of Chicago School of Medicine, 5841 S. Maryland Ave., Chicago, 60637 Illinois USA
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Role of Oxidative Stress and NFkB in Hypoxia-Induced Pulmonary Edema. Exp Biol Med (Maywood) 2008; 233:1088-98. [DOI: 10.3181/0712-rm-337] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Hypoxia is well known to increase the free radical generation in the body, leading to oxidative stress. In the present study, we have determined whether the increased oxidative stress further upregulates the nuclear transcription factor (NFkB) in the development of pulmonary edema. The rats were exposed to hypobaric hypoxia at 7620 m (280 mm Hg) for different durations, that is, 3 hrs, 6 hrs, 12 hrs, and 24 hrs at 25 ± 1°C. The results revealed that exposure of animals to hypobaric hypoxia led to a significant increase in vascular leakage, with time up to 6 hrs (256.38 ± 61 rfu/g) as compared with control (143.63 ± 60.1 rfu/g). There was a significant increase in reactive oxygen species, lipid peroxidation, and superoxide dismutase levels, with a concurrent decrease in lung glutathione peroxidase activity. There was 13-fold increase in the expression of NFkB level in nuclear fraction of lung homogenates of hypoxic animals over control rats. The DNA binding activity of NFkB was found to be increased significantly ( P < 0.001) in the lungs of rats exposed to hypoxia as compared with control. Further, we observed a significant increase in proinflammatory cytokines such as IL-1, IL-6, and TNF-α with concomitant upregulation of cell adhesion molecules such as ICAM-I, VCAM-I, and P-selectin in the lung of rats exposed to hypoxia as compared with control. Interestingly, pretreatment of animals with curcumin (NFkB blocker) attenuated hypoxia-induced vascular leakage in lungs with concomitant reduction of NFkB levels. The present study therefore reveals the possible involvement of NFkB in the development of pulmonary edema.
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Kaufmann BA, Bernheim AM, Kiencke S, Fischler M, Sklenar J, Mairbäurl H, Maggiorini M, Brunner-La Rocca HP. Evidence supportive of impaired myocardial blood flow reserve at high altitude in subjects developing high-altitude pulmonary edema. Am J Physiol Heart Circ Physiol 2008; 294:H1651-7. [DOI: 10.1152/ajpheart.00760.2007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An exaggerated increase in pulmonary arterial pressure is the hallmark of high-altitude pulmonary edema (HAPE) and is associated with endothelial dysfunction of the pulmonary vasculature. Whether the myocardial circulation is affected as well is not known. The aim of this study was, therefore, to investigate whether myocardial blood flow reserve (MBFr) is altered in mountaineers developing HAPE. Healthy mountaineers taking part in a trial of prophylactic treatment of HAPE were examined at low (490 m) and high altitude (4,559 m). MBFr was derived from low mechanical index contrast echocardiography, performed at rest and during submaximal exercise. Among 24 subjects evaluated for MBFr, 9 were HAPE-susceptible individuals on prophylactic treatment with dexamethasone or tadalafil, 6 were HAPE-susceptible individuals on placebo, and 9 persons without HAPE susceptibility served as controls. At low altitude, MBFr did not differ between groups. At high altitude, MBFr increased significantly in HAPE-susceptible individuals on treatment (from 2.2 ± 0.8 at low to 2.9 ± 1.0 at high altitude, P = 0.04) and in control persons (from 1.9 ± 0.8 to 2.8 ± 1.0, P = 0.02), but not in HAPE-susceptible individuals on placebo (2.5 ± 0.3 and 2.0 ± 1.3 at low and high altitude, respectively, P > 0.1). The response to high altitude was significantly different between the two groups ( P = 0.01). There was a significant inverse relation between the increase in the pressure gradient across the tricuspid valve and the change in myocardial blood flow reserve. HAPE-susceptible individuals not taking prophylactic treatment exhibit a reduced MBFr compared with either treated HAPE-susceptible individuals or healthy controls at high altitude.
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Stream JO, Grissom CK. Update on High-Altitude Pulmonary Edema: Pathogenesis, Prevention, and Treatment. Wilderness Environ Med 2008; 19:293-303. [DOI: 10.1580/07-weme-rev-173.1] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Affiliation(s)
- Peter Bärtsch
- Department of Internal Medicine VII, Division of Sports Medicine, Medical University Clinic, Im Neuenheimer Feld 410, D-69120 Heidelberg, Germany.
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Abstract
Pulmonary hypertension is a condition associated with a variety of pulmonary disorders whose common denominator is alveolar hypoxia. Such disorders include chronic obstructive pulmonary disease, pulmonary fibrosis, sleep-disordered breathing, and exposure to high altitude. Acute hypoxia is characterized by vasoconstriction of small pulmonary arteries, a phenomenon called hypoxic pulmonary vasoconstriction. With prolonged hypoxia, thickening of the smooth vascular layer of the small pulmonary arteries occurs, a phenomenon described as pulmonary vascular remodeling. Although the core mechanisms of both vasoconstriction and remodeling are thought to reside in the smooth muscle cell layer, the endothelium modulates these two processes. The purpose of this review is briefly to (a) discuss the mechanisms of hypoxic pulmonary hypertension as it pertains to certain disease states, and (b) examine the pathways that have potential therapeutic applications for this condition.
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Affiliation(s)
- Ioana R Preston
- Pulmonary, Critical Care and Sleep Division, Tufts-New England Medical Center, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
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Dehnert C, Berger MM, Mairbäurl H, Bärtsch P. High altitude pulmonary edema: a pressure-induced leak. Respir Physiol Neurobiol 2007; 158:266-73. [PMID: 17602898 DOI: 10.1016/j.resp.2007.05.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Revised: 04/30/2007] [Accepted: 05/01/2007] [Indexed: 10/23/2022]
Abstract
High altitude pulmonary edema (HAPE) is a non-cardiogenic pulmonary edema that can occur in healthy individuals who ascend rapidly to altitudes above 3000-4000m. Excessive pulmonary artery pressure (PAP) is crucial for the development of HAPE, since lowering pulmonary artery pressure by nifedipine or tadalafil (phosphodiesterase-5-inhibitor) will in most cases prevent HAPE. Recent studies using microspheres in swine and magnetic resonance imaging in humans strongly support the concept and primacy of nonuniform hypoxic arteriolar vasoconstriction to explain how hypoxic pulmonary vasoconstriction occurring predominantly at the arteriolar level can cause leakage. Evidence is accumulating that the excessive PAP response in HAPE-susceptible individuals is due to a reduced NO bioavailability. HAPE-susceptible individuals show an endothelial dysfunction in the systemic circulation in hypoxia. Lower levels of exhaled NO in hypoxia before and during HAPE suggest that this abnormality also occurs in the lungs and polymorphisms of the eNOS gene are associated with susceptibility to HAPE in the Indian and Japanese population.
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Affiliation(s)
- Christoph Dehnert
- Medical University Clinic, Department of Internal Medicine, Div. of Sports Medicine, Im Neuenheimer Feld 410, D - 69120 Heidelberg, Germany
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