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Luks AM, Beidleman BA, Freer L, Grissom CK, Keyes LE, McIntosh SE, Rodway GW, Schoene RB, Zafren K, Hackett PH. Wilderness Medical Society Clinical Practice Guidelines for the Prevention, Diagnosis, and Treatment of Acute Altitude Illness: 2024 Update. Wilderness Environ Med 2024; 35:2S-19S. [PMID: 37833187 DOI: 10.1016/j.wem.2023.05.013] [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: 12/27/2022] [Revised: 04/14/2023] [Accepted: 05/17/2023] [Indexed: 10/15/2023]
Abstract
To provide guidance to clinicians about best practices, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for prevention, diagnosis, and treatment of acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. Recommendations are graded based on the quality of supporting evidence and the balance between the benefits and risks/burdens according to criteria put forth by the American College of Chest Physicians. The guidelines also provide suggested approaches for managing each form of acute altitude illness that incorporate these recommendations as well as recommendations on how to approach high altitude travel following COVID-19 infection. This is an updated version of the original WMS Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness published in Wilderness & Environmental Medicine in 2010 and the subsequently updated WMS Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness published in 2014 and 2019.
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Affiliation(s)
- Andrew M Luks
- Division of Pulmonary, Critical Care and Sleep Medicine, University of Washington, Seattle, WA
| | - Beth A Beidleman
- Military Performance Division, US Army Research Institute of Environmental Medicine, Natick, MA
| | - Luanne Freer
- Everest ER, Himalayan Rescue Association, Kathmandu, Nepal
| | - Colin K Grissom
- Pulmonary and Critical Care Medicine, Intermountain Healthcare and the University of Utah, Salt Lake City, UT
| | - Linda E Keyes
- Department of Emergency Medicine, Section of Wilderness Medicine, University of Colorado, Anschutz Medical Campus, Aurora, CO
| | - Scott E McIntosh
- Department of Emergency Medicine, University of Utah Health, Salt Lake City, UT
| | - George W Rodway
- Department of Family Medicine-Sports Medicine, University of Nevada, Reno School of Medicine, Reno, NV
| | - Robert B Schoene
- Division of Pulmonary and Critical Care Medicine, Sound Physicians, St. Mary's Medical Center and Division of Pulmonary and Critical Care Medicine, University of California, San Francisco, San Francisco, CA
| | - Ken Zafren
- Department of Emergency Medicine, Stanford University School of Medicine, Stanford, CA
- Himalayan Rescue Association, Kathmandu, Nepal
| | - Peter H Hackett
- Altitude Research Center, Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO
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Zelmanovich R, Pierre K, Felisma P, Cole D, Goldman M, Lucke-Wold B. High Altitude Cerebral Edema: Improving Treatment Options. BIOLOGICS (BASEL, SWITZERLAND) 2022; 2:81-91. [PMID: 35425940 PMCID: PMC9006955 DOI: 10.3390/biologics2010007] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
High altitude illness in its most severe form can lead to high altitude cerebral edema (HACE). Current strategies have focused on prevention with graduated ascents, pharmacologic prophylaxis, and descent at first signs of symptoms. Little is understood regarding treatment with steroids and oxygenation being commonly utilized. Pre-clinical studies with turmeric derivatives have offered promise due to its anti-inflammatory and antioxidant properties, but they warrant validation clinically. Ongoing work is focused on better understanding the disease pathophysiology with an emphasis on the glymphatic system and venous outflow obstruction. This review highlights what is known regarding diagnosis, treatment, and prevention, while also introducing novel pathophysiology mechanisms warranting further investigation.
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Affiliation(s)
| | - Kevin Pierre
- Department of Neurosurgery, University of Florida, Gainesville, FL 32611, USA
| | - Patrick Felisma
- Department of Neurosurgery, University of Florida, Gainesville, FL 32611, USA
| | - Dwayne Cole
- Department of Neurosurgery, University of Florida, Gainesville, FL 32611, USA
| | - Matthew Goldman
- Department of Neurosurgery, University of Florida, Gainesville, FL 32611, USA
| | - Brandon Lucke-Wold
- Department of Neurosurgery, University of Florida, Gainesville, FL 32611, USA
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3
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Affiliation(s)
- Andrew M Luks
- From the Division of Pulmonary, Critical Care, and Sleep Medicine, University of Washington, Seattle (A.M.L.); and the Altitude Research Center, Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora (P.H.H.)
| | - Peter H Hackett
- From the Division of Pulmonary, Critical Care, and Sleep Medicine, University of Washington, Seattle (A.M.L.); and the Altitude Research Center, Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora (P.H.H.)
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Doutreleau S. [Physiological and pathological responses to altitude]. Rev Mal Respir 2021; 38:1013-1024. [PMID: 34782179 DOI: 10.1016/j.rmr.2020.12.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 12/28/2020] [Indexed: 11/27/2022]
Abstract
Hypobaric hypoxia, the hallmark of a high altitude environment, has important physiological effects on both the cardiovascular and respiratory systems in order to maintain a balance between oxygen demand and supply. This dynamic of acclimatization is influenced both by the level of altitude and the speed of progression, but is also very individual with a wide spectrum of responses and sensitivities. This wide range of responses is associated with nonspecific symptoms characterising acute mountain sickness and high-altitude cerebral or pulmonary oedema. This article reviews the current knowledge about both the acclimatization processes and specific diseases of high-altitude.
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Affiliation(s)
- S Doutreleau
- Inserm, UM sports et pathologies, laboratoire HP2, CHU Grenoble-Alpes, université Grenoble Alpes, EXALT - centre d'expertise sur l'altitude, 38000 Grenoble, France.
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Staab JE, Muza SR, Fulco CS, Andrew SP, Beidleman BA. Impact of 2 days of staging at 2500-4300 m on sleep quality and quantity following subsequent exposure to 4300 m. Physiol Rep 2021; 9:e15063. [PMID: 34713967 PMCID: PMC8554773 DOI: 10.14814/phy2.15063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 09/10/2021] [Accepted: 09/12/2021] [Indexed: 12/21/2022] Open
Abstract
The impact of 2 days of staging at 2500-4300 m on sleep quality and quantity following subsequent exposure to 4300 m was determined. Forty-eight unacclimatized men and women were randomly assigned to stage for 2 days at one of four altitudes (2500, 3000, 3500, or 4300 m) prior to assessment on the summit of Pikes Peak (4300 m) for 2 days. Volunteers slept for one night at sea level (SL), two nights at respective staging altitudes, and two nights at Pikes Peak. Each wore a pulse oximeter to measure sleep arterial oxygen saturation (sSpO2 , %) and number of desaturations (DeSHr, events/hr) and a wrist motion detector to estimate sleep awakenings (Awak, awakes/hr) and sleep efficiency (Eff, %). Acute mountain sickness (AMS) was assessed using the Environmental Symptoms Questionnaire and daytime SpO2 was assessed after AMS measurements. The mean of all variables for both staging days (STG) and Pikes Peak days (PP) was calculated. The sSpO2 and daytime SpO2 decreased (p < 0.05) from SL during STG in all groups in a dose-dependent manner. During STG, DeSHr were higher (p < 0.05), Eff was lower (p < 0.05), and AMS symptoms were higher (p < 0.05) in the 3500 and 4300 m groups compared to the 2500 and 3000 m groups while Awak did not differ (p > 0.05) between groups. At PP, the sSpO2 , DeSHr, Awak, and Eff were similar among all groups but the 2500 m group had greater AMS symptoms (p < 0.05) than the other groups. Two days of staging at 2500-4300 m induced a similar degree of sleep acclimatization during subsequent ascent to 4300 m but the 2500 m group was not protected against AMS at 4300 m.
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Affiliation(s)
- Janet E. Staab
- Military Performance DivisionU.S. Army Research Institute of Environmental MedicineNatickMassachusettsUSA
| | - Stephen R. Muza
- Strategic Scientific Management OfficeU.S. Army Research Institute of Environmental MedicineNatickMassachusettsUSA
| | - Charles S. Fulco
- Thermal and Mountain Medicine DivisionU.S. Army Research Institute of Environmental MedicineNatickMassachusettsUSA
| | - Sean P. Andrew
- Thermal and Mountain Medicine DivisionU.S. Army Research Institute of Environmental MedicineNatickMassachusettsUSA
| | - Beth A. Beidleman
- Biophysics and Biomedical Modeling DivisionU.S. Army Research Institute of Environmental MedicineNatickMassachusettsUSA
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Gao D, Wang Y, Zhang R, Zhang Y. Efficacy of acetazolamide for the prophylaxis of acute mountain sickness: A systematic review, meta-analysis, and trial sequential analysis of randomized clinical trials. Ann Thorac Med 2021; 16:337-346. [PMID: 34820021 PMCID: PMC8588948 DOI: 10.4103/atm.atm_651_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 04/08/2021] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Acute mountain sickness (AMS) is a benign and self-limiting syndrome, but can progress to life-threatening conditions if leave untreated. This study aimed to assess the efficacy of acetazolamide for the prophylaxis of AMS, and disclose factors that affect the treatment effect of acetazolamide. METHODS Randomized controlled trials comparing the use of acetazolamide versus placebo for the prevention of AMS were included. The incidence of AMS was our primary endpoint. Meta-regression analysis was conducted to explore factors that associated with acetazolamide efficacy. Trial sequential analyses were conducted to estimate the statistical power of the available data. RESULTS A total of 22 trials were included. Acetazolamide at 125, 250, and 375 mg/bid significantly reduced incidence of AMS compared to placebo. TAS indicated that the current evidence was adequate confirming the efficacy of acetazolamide at 125, 250, and 375 mg/bid in lowering incidence of AMS. There was no evidence of an association between efficacy and dose of acetazolamide, timing at start of acetazolamide treatment, mode of ascent, AMS assessment score, timing of AMS assessment, baseline altitude, and endpoint altitude. CONCLUSION Acetazolamide is effective prophylaxis for the prevention of AMS at 125, 250, and 375 mg/bid. Future investigation should focus on personal characteristics, disclosing the correlation between acetazolamide efficacy and body mass, height, degree of prior acclimatization, individual inborn susceptibility, and history of AMS.
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Affiliation(s)
- Daiquan Gao
- Department of Neurology, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Yuan Wang
- Department of Neurology, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Rujiang Zhang
- Department of Neurology, The People's Hospital of RuiLi, Yunnan, China
| | - Yunzhou Zhang
- Department of Neurology, Xuanwu Hospital, Capital Medical University, Beijing, China
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Hypoxic Exercise Exacerbates Hypoxemia and Acute Mountain Sickness in Obesity: A Case Analysis. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph18179078. [PMID: 34501667 PMCID: PMC8430682 DOI: 10.3390/ijerph18179078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2021] [Revised: 08/14/2021] [Accepted: 08/23/2021] [Indexed: 12/21/2022]
Abstract
Acute mountain sickness (AMS) is a common syndrome characterized by headache, dizziness, loss of appetite, weakness, and nausea. As a major public health issue, obesity has increased in high altitude urban residents and intermittent commuters to high altitudes. The present study investigated acute hypoxic exposure and hypoxic exercise on hypoxemia severity and AMS symptoms in a physically active obese man. In this case analysis, peripheral oxygen saturation (SpO2) was used to evaluate hypoxemia, heart rate (HR) and blood pressure (BP) were used to reflect the function of autonomic nervous system (ANS), and Lake Louise scoring (LLS) was used to assess AMS. The results showed that acute hypoxic exposure led to severe hypoxemia (SpO2 = 72%) and tachycardia (HRrest = 97 bpm), and acute hypoxic exercise exacerbated severe hypoxemia (SpO2 = 59%) and ANS dysfunction (HRpeak = 167 bpm, SBP/DBP = 210/97 mmHg). At the end of the 6-h acute hypoxic exposure, the case developed severe AMS (LLS = 10) symptoms of headache, gastrointestinal distress, cyanosis, vomiting, poor appetite, and fatigue. The findings of the case study suggest that high physical activity level appears did not show a reliable protective effect against severe hypoxemia, ANS dysfunction, and severe AMS symptoms in acute hypoxia exposure and hypoxia exercise.
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Urdampilleta A, León-Guereño P, Calleja-González J, Roche E, Mielgo-Ayuso J. Inclusion of resistance routines in a hypoxia training program does not interfere with prevention of acute mountain sickness. PHYSICIAN SPORTSMED 2021; 49:151-157. [PMID: 32578478 DOI: 10.1080/00913847.2020.1786344] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
OBJECTIVES Acclimatization strategies have been shown to be the best solutions to avoid acute mountain sickness. In this context, we have designed a protocol performed in hypoxia that includes resistance routines in combination with classical endurance training exercises with mountain trekking at mid altitude. METHODS Thirty-two volunteers preparing different mountain expeditions participated in the study distributed into two groups. One group trained at 2000 m, while another group trained at 4500-5800 m of simulated altitude in a hypoxic chamber. Acute mountain sickness was monitored by answering the Lake Louise Scale questionnaire during 2 sleeping sessions at 4800 m of simulated altitude at the beginning and at the end of the study. At the same time, oxygen saturation was determined in both groups to monitor physiologic adaptation. Data were also collected from the base camps in each expedition before ascension. RESULTS Acute mountain sickness incidence in the hypoxic group decreased from 100% at the beginning to 12% of individuals at the end of the training period, and it was 25% at the base camps of expeditions. On the other hand, the control group passed from 100% to 88% of individuals at the end of the intervention and 70% at the base camps. At the same time, acute mountain sickness severity was mild in the experimental group compared to moderate-severe in the control group. These data were supported by the oxygen saturation values, indicating adequate adaptation changes for altitude in the hypoxic group. CONCLUSION The inclusion of resistance workouts in combination with endurance exercises, all performed in hypoxic conditions, does not interfere with an optimal adaptation to altitude and to prevent acute mountain sickness.
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Affiliation(s)
| | | | - Julio Calleja-González
- Department of Physical Education and Sports, University of Basque Country (UPV-EHU), Vitoria, Spain
| | - Enrique Roche
- Department of Applied Biology-Nutrition, Institute of Bioengineering, University Miguel Hernandez (Elche). Alicante Institute for Health and Biomedical Research (ISABIAL), Alicante, Spain.,CIBERobn (Fisiopatología De La Obesidad Y La Nutrición CB12/03/30038) Instituto De Salud Carlos III, Spain
| | - Juan Mielgo-Ayuso
- Department of Biochemistry, Molecular Biology and Physiology, Faculty of Physical Therapy, University of Valladolid, Soria, Spain
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High-altitude illnesses: Old stories and new insights into the pathophysiology, treatment and prevention. SPORTS MEDICINE AND HEALTH SCIENCE 2021; 3:59-69. [PMID: 35782163 PMCID: PMC9219347 DOI: 10.1016/j.smhs.2021.04.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 04/11/2021] [Accepted: 04/11/2021] [Indexed: 01/19/2023] Open
Abstract
Areas at high-altitude, annually attract millions of tourists, skiers, trekkers, and climbers. If not adequately prepared and not considering certain ascent rules, a considerable proportion of those people will suffer from acute mountain sickness (AMS) or even from life-threatening high-altitude cerebral (HACE) or/and pulmonary edema (HAPE). Reduced inspired oxygen partial pressure with gain in altitude and consequently reduced oxygen availability is primarily responsible for getting sick in this setting. Appropriate acclimatization by slowly raising the hypoxic stimulus (e.g., slow ascent to high altitude) and/or repeated exposures to altitude or artificial, normobaric hypoxia will largely prevent those illnesses. Understanding physiological mechanisms of acclimatization and pathophysiological mechanisms of high-altitude diseases, knowledge of symptoms and signs, treatment and prevention strategies will largely contribute to the risk reduction and increased safety, success and enjoyment at high altitude. Thus, this review is intended to provide a sound basis for both physicians counseling high-altitude visitors and high-altitude visitors themselves.
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Gao D, Wang Y, Zhang R, Zhang Y. Efficacy of Acetazolamide for the Prophylaxis of Acute Mountain Sickness: A Systematic Review, Meta-Analysis and Trial Sequential Analysis of Randomized Clinical Trials. Am J Med Sci 2021; 361:635-645. [PMID: 33587912 DOI: 10.1016/j.amjms.2020.12.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 11/24/2020] [Accepted: 12/10/2020] [Indexed: 10/22/2022]
Abstract
BACKGROUND Acute mountain sickness (AMS) is a benign and self-limiting syndrome but can progress to life-threatening conditions if leave untreated. This study aimed to assess the efficacy of acetazolamide for the prophylaxis of AMS and disclose potential factors that affect the treatment effect of acetazolamide. MATERIALS AND METHODS Randomized controlled trials comparing the use of acetazolamide versus placebo for the prevention of AMS were included. The incidence of AMS was the primary endpoint. Meta-regression analysis was conducted to explore potential factors associated with acetazolamide efficacy. Trial sequential analysis (TSA) was conducted to estimate the statistical power of the available data. RESULTS A total of 22 trials were included. Acetazolamide at 125, 250, and 375 mg/ twice daily (bid) significantly reduced incidence of AMS compared to placebo. TAS indicated that the current evidence was adequate confirming the efficacy of acetazolamide at 125, 250, and 375 mg/bid in lowering incidence of AMS. There was no evidence of an association between efficacy and dose of acetazolamide, timing at start of acetazolamide treatment, mode of ascent, AMS assessment score, timing of AMS assessment, baseline altitude, and endpoint altitude. CONCLUSION Acetazolamide is effective prophylaxis for the prevention of AMS in doses of 125, 250, and 375 mg/bid. Future investigations should focus on personal characteristics, disclosing the correlation between acetazolamide efficacy and body mass, height, degree of prior acclimatization, individual inborn susceptibility, and history of AMS.
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Affiliation(s)
- Daiquan Gao
- Department of Neurology, Xuanwu Hospital, Capital Medical University, Xicheng District, Beijing, China
| | - Yuan Wang
- Department of Neurology, Xuanwu Hospital, Capital Medical University, Xicheng District, Beijing, China
| | - Rujiang Zhang
- Department of Neurology, The People's Hospital of RuiLi, Yunnan, China
| | - Yunzhou Zhang
- Department of Neurology, Xuanwu Hospital, Capital Medical University, Xicheng District, Beijing, China.
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Dünnwald T, Kienast R, Niederseer D, Burtscher M. The Use of Pulse Oximetry in the Assessment of Acclimatization to High Altitude. SENSORS 2021; 21:s21041263. [PMID: 33578839 PMCID: PMC7916608 DOI: 10.3390/s21041263] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 01/22/2021] [Accepted: 02/03/2021] [Indexed: 02/07/2023]
Abstract
Background: Finger pulse oximeters are widely used to monitor physiological responses to high-altitude exposure, the progress of acclimatization, and/or the potential development of high-altitude related diseases. Although there is increasing evidence for its invaluable support at high altitude, some controversy remains, largely due to differences in individual preconditions, evaluation purposes, measurement methods, the use of different devices, and the lacking ability to interpret data correctly. Therefore, this review is aimed at providing information on the functioning of pulse oximeters, appropriate measurement methods and published time courses of pulse oximetry data (peripheral oxygen saturation, (SpO2) and heart rate (HR), recorded at rest and submaximal exercise during exposure to various altitudes. Results: The presented findings from the literature review confirm rather large variations of pulse oximetry measures (SpO2 and HR) during acute exposure and acclimatization to high altitude, related to the varying conditions between studies mentioned above. It turned out that particularly SpO2 levels decrease with acute altitude/hypoxia exposure and partly recover during acclimatization, with an opposite trend of HR. Moreover, the development of acute mountain sickness (AMS) was consistently associated with lower SpO2 values compared to individuals free from AMS. Conclusions: The use of finger pulse oximetry at high altitude is considered as a valuable tool in the evaluation of individual acclimatization to high altitude but also to monitor AMS progression and treatment efficacy.
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Affiliation(s)
- Tobias Dünnwald
- Institute for Sports Medicine, Alpine Medicine and Health Tourism (ISAG), UMIT—Private University for Health Sciences, Medical Informatics and Technology, 6060 Hall in Tirol, Austria;
| | - Roland Kienast
- Department of Biomedical and Health Technology, Federal Higher Technical Institute for Education and Experimentation—HTL Anichstraße, 6020 Innsbruck, Austria;
| | - David Niederseer
- Department of Cardiology, University Hospital Zurich, University Heart Center Zurich, University of Zurich, 8091 Zurich, Switzerland;
| | - Martin Burtscher
- Department of Sport Science, University of Innsbruck, 6020 Innsbruck, Austria
- Correspondence:
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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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Beidleman BA, Fulco CS, Cymerman A, Staab JE, Buller MJ, Muza SR. New metric of hypoxic dose predicts altitude acclimatization status following various ascent profiles. Physiol Rep 2019; 7:e14263. [PMID: 31660703 PMCID: PMC6817994 DOI: 10.14814/phy2.14263] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 07/14/2019] [Indexed: 11/24/2022] Open
Abstract
Medical personnel need practical guidelines on how to construct high altitude ascents to induce altitude acclimatization and avoid acute mountain sickness (AMS) following the first night of sleep at high altitude. Using multiple logistic regression and a comprehensive database, we developed a quantitative prediction model using ascent profile as the independent variable and altitude acclimatization status as the dependent variable from 188 volunteers (147 men, 41 women) who underwent various ascent profiles to 4 km. The accumulated altitude exposure (AAE), a new metric of hypoxic dose, was defined as the ascent profile and was calculated by multiplying the altitude elevation (km) by the number of days (d) at that altitude prior to ascent to 4 km. Altitude acclimatization status was defined as the likely presence or absence of AMS after ~24 h of exposure at 4 km. AMS was assessed using the Cerebral Factor Score (AMS-C) from the Environmental Symptoms Questionnaire and deemed present if AMS-C was ≥0.7. Other predictor variables included in the model were age and body mass index (BMI). Sex, race, and smoking status were considered in model development but eliminated due to inadequate numbers in each of the ascent profiles. The AAE (km·d) significantly (P < 0.0001) predicted AMS in the model. For every 1 km·d increase in AAE, the odds of getting sick decreased by 41.3%. Equivalently, for every 1 km·d decrease in AAE, the odds of getting sick increased by 70.4%. Age and BMI were not significant predictors. The model demonstrated excellent discrimination (AUC = 0.83 (95% CI = 0.79-0.91) and calibration (Hosmer-Lemeshow = 0.11). The model provides a priori estimates of altitude acclimatization status resulting from the use of various rapid, staged, and graded ascent profiles.
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Affiliation(s)
- Beth A. Beidleman
- U.S. Army Research Institute of Environmental MedicineNatickMassachusetts
| | - Charles S. Fulco
- U.S. Army Research Institute of Environmental MedicineNatickMassachusetts
| | - Allen Cymerman
- U.S. Army Research Institute of Environmental MedicineNatickMassachusetts
| | - Janet E. Staab
- U.S. Army Research Institute of Environmental MedicineNatickMassachusetts
| | - Mark J. Buller
- U.S. Army Research Institute of Environmental MedicineNatickMassachusetts
| | - Stephen R. Muza
- U.S. Army Research Institute of Environmental MedicineNatickMassachusetts
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14
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Aksel G, Çorbacıoğlu ŞK, Özen C. High-altitude illness: Management approach. Turk J Emerg Med 2019; 19:121-126. [PMID: 31687609 PMCID: PMC6819752 DOI: 10.1016/j.tjem.2019.09.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2019] [Revised: 09/15/2019] [Accepted: 09/15/2019] [Indexed: 11/30/2022] Open
Abstract
In high altitudes, usually above 2500 m, travelers are faced with decreased partial pressure of oxygen along with decreased barometric pressure. High-altitude illness, a syndrome of acute mountain sickness, high-altitude cerebral edema and high-altitude pulmonary edema, occurs due to the hypobaric hypoxia when there is inadequate acclimatization. This review provides detailed information about pathophysiology, clinical features, prevention and treatment strategies for high-altitude illness according to the current literature.
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Affiliation(s)
- Gökhan Aksel
- University of Health Sciences, Ümraniye Training and Research Hospital, Emergency Medicine Clinic, İstanbul, Turkey
| | - Şeref Kerem Çorbacıoğlu
- University of Health Sciences, Keçiören Training and Research Hospital, Emergency Medicine Clinic, Ankara, Turkey
| | - Can Özen
- Emergency Department, King's College Hospital, London, UK
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15
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Lipman GS, Jurkiewicz C, Winstead-Derlega C, Navlyt A, Burns P, Walker A, Phillips C, Reilly A, Burnier A, Romero J, Warner K, Hackett P. Day of Ascent Dosing of Acetazolamide for Prevention of Acute Mountain Sickness. High Alt Med Biol 2019; 20:271-278. [DOI: 10.1089/ham.2019.0007] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Affiliation(s)
- Grant S. Lipman
- Department of Emergency Medicine, Stanford University School of Medicine, Stanford, California
| | - Carrie Jurkiewicz
- Department of Emergency Medicine, Stanford University School of Medicine, Stanford, California
| | | | - Andrew Navlyt
- Stanford University Emergency Medicine Residency, Stanford University School of Medicine, Stanford, California
| | - Patrick Burns
- Department of Emergency Medicine, Stanford University School of Medicine, Stanford, California
| | - Anne Walker
- Department of Emergency Medicine, Stanford University School of Medicine, Stanford, California
| | - Caleb Phillips
- Department of Computational Science, University of Colorado, Boulder, Boulder, Colorado
| | - Aaron Reilly
- Department of Emergency Medicine, University of New Mexico School of Medicine, Albuquerque, New Mexico
| | - Andre Burnier
- Stanford University Emergency Medicine Residency, Stanford University School of Medicine, Stanford, California
| | - Joseph Romero
- Stanford University Emergency Medicine Residency, Stanford University School of Medicine, Stanford, California
| | - Keiran Warner
- Stanford University Emergency Medicine Residency, Stanford University School of Medicine, Stanford, California
| | - Peter Hackett
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado
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Luks AM, Auerbach PS, Freer L, Grissom CK, Keyes LE, McIntosh SE, Rodway GW, Schoene RB, Zafren K, Hackett PH. Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness: 2019 Update. Wilderness Environ Med 2019; 30:S3-S18. [PMID: 31248818 DOI: 10.1016/j.wem.2019.04.006] [Citation(s) in RCA: 99] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2018] [Revised: 04/12/2019] [Accepted: 04/19/2019] [Indexed: 12/16/2022]
Abstract
To provide guidance to clinicians about best preventive and therapeutic practices, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for prevention and treatment of acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. Recommendations are graded based on the quality of supporting evidence and the balance between the benefits and risks/burdens according to criteria put forth by the American College of Chest Physicians. The guidelines also provide suggested approaches to prevention and management of each form of acute altitude illness that incorporate these recommendations. This is an updated version of the original WMS Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness published in 2010 and subsequently updated as the WMS Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness in 2014.
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Affiliation(s)
- Andrew M Luks
- Division of Pulmonary, Critical Care and Sleep Medicine, University of Washington, Seattle, WA.
| | - Paul S Auerbach
- Department of Emergency Medicine, Stanford University School of Medicine, Stanford, CA
| | - Luanne Freer
- Yellowstone National Park, WY; Midway Atoll National Wildlife Refuge, Honolulu, HI; Everest ER, Himalayan Rescue Association, Kathmandu, Nepal
| | - Colin K Grissom
- Division of Pulmonary and Critical Care Medicine, Intermountain Medical Center, Salt Lake City, UT; Division of Pulmonary and Critical Care Medicine, University of Utah, Salt Lake City, UT
| | - Linda E Keyes
- Department of Emergency Medicine, University of Colorado, Denver, CO; Boulder Community Health, Boulder, CO
| | - Scott E McIntosh
- Division of Emergency Medicine, University of Utah, Salt Lake City, UT
| | - George W Rodway
- University of California, Davis School of Nursing, Sacramento, CA
| | - Robert B Schoene
- Division of Pulmonary and Critical Care Medicine, Sound Physicians, St. Mary's Medical Center, San Francisco, CA
| | - Ken Zafren
- Department of Emergency Medicine, Stanford University School of Medicine, Stanford, CA; Himalayan Rescue Association, Kathmandu, Nepal
| | - Peter H Hackett
- Altitude Research Center, Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO
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Beidleman BA, Fulco CS, Glickman EL, Cymerman A, Kenefick RW, Cadarette BS, Andrew SP, Staab JE, Sils IV, Muza SR. Acute Mountain Sickness is Reduced Following 2 Days of Staging During Subsequent Ascent to 4300 m. High Alt Med Biol 2018; 19:329-338. [PMID: 30517038 DOI: 10.1089/ham.2018.0048] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVE To determine whether 2 days of staging at 2500-3500 m, combined with either high or low physical activity, reduces acute mountain sickness (AMS) during subsequent ascent to 4300 m. METHODS Three independent groups of unacclimatized men and women were staged for 2 days at either 2500 m (n = 18), 3000 m (n = 16), or 3500 m (n = 15) before ascending and living for 2 days at 4300 m and compared with a control group that directly ascended to 4300 m (n = 12). All individuals departed to the staging altitudes or 4300 m after spending one night at 2000 m during which they breathed supplemental oxygen to simulate sea level conditions. Half in each group participated in ∼3 hours of daily physical activity while half were sedentary. Women accounted for ∼25% of each group. AMS incidence was assessed using the Environmental Symptoms Questionnaire. AMS was classified as mild (≥0.7 and <1.5), moderate (≥1.5 and <2.6), and severe (≥2.6). RESULTS While staging, the incidence of AMS was lower (p < 0.001) in the 2500 m (0%), 3000 m (13%), and 3500 m (40%) staged groups than the direct ascent control group (83%). After ascent to 4300 m, the incidence of AMS was lower in the 3000 m (43%) and 3500 m (40%) groups than the 2500 m group (67%) and direct ascent control (83%). Neither activity level nor sex influenced the incidence of AMS during further ascent to 4300 m. CONCLUSIONS Two days of staging at either 3000 or 3500 m, with or without physical activity, reduced AMS during subsequent ascent to 4300 m but staging at 3000 m may be recommended because of less incidence of AMS.
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Affiliation(s)
- Beth A Beidleman
- 1 Biophysics and Biomedical Modeling Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Charles S Fulco
- 2 Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | | | - Allen Cymerman
- 2 Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Robert W Kenefick
- 2 Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Bruce S Cadarette
- 2 Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Sean P Andrew
- 2 Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Janet E Staab
- 3 Military Performance Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Ingrid V Sils
- 2 Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Stephen R Muza
- 4 Strategic Scientific Management Office, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
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Kenefick RW, Beidleman BA, Andrew SP, Cadarette BS, Muza SR, Fulco CS. Two-Day Residence at 2500 m to 4300 m Does Not Affect Subsequent Exercise Performance at 4300 m. Med Sci Sports Exerc 2018; 51:744-750. [PMID: 30439786 DOI: 10.1249/mss.0000000000001843] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE To determine the efficacy residing for 2 d at various altitudes while sedentary (S) or active (A; ~90 min hiking 2 d) on exercise performance at 4300 m. METHODS Sea-level (SL) resident men (n = 45) and women (n = 21) (mean ± SD; 23 ± 5 yr; 173 ± 9 cm; 73 ± 12 kg; V˙O2peak = 49 ± 7 mL·kg·min) were randomly assigned to a residence group and, S or A within each group: 2500 m (n = 11S, 8A), 3000 m (n = 6S, 12A), 3500 m (n = 6S, 8A), or 4300 m (n = 7S, 8A). Exercise assessments occurred at SL and 4300 m after 2-d residence and consisted of 20 min of steady-state (SS) treadmill walking (45% ± 3% SL V˙O2peak) and a 5-mile, self-paced running time trial (TT). Arterial oxygen saturation (SpO2) and HR were recorded throughout exercise. Resting SpO2 was recorded at SL, at 4 and 46 h of residence, and at 4300 m before exercise assessment. To determine if 2-d altitude residence improved 4300 m TT performance, results were compared with estimated performances using a validated prediction model. RESULTS For all groups, resting SpO2 was reduced (P < 0.01) after 4 h of residence relative to SL inversely to the elevation and did not improve after 46 h. Resting SpO2 (~83%) did not differ among groups at 4300 m. Although SL and 4300 m SS exercise SpO2 (97% ± 2% to 74% ± 4%), HR (123 ± 10 bpm to 140 ± 12 bpm) and TT duration (51 ± 9 to 73 ± 16 min) were different (P < 0.01), responses at 4300 m were similar among all groups, as was actual and predicted 4300 m TT performances (74 ± 12 min). CONCLUSIONS Residing for 2 d at 2500 to 4300 m, with or without daily activity, did not improve resting SpO2, SS exercise responses, or TT performance at 4300 m.
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Affiliation(s)
- Robert W Kenefick
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA
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Sheth C, Ombach H, Olson P, Renshaw PF, Kanekar S. Increased Anxiety and Anhedonia in Female Rats Following Exposure to Altitude. High Alt Med Biol 2018; 19:81-90. [PMID: 29431475 DOI: 10.1089/ham.2017.0125] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Sheth, Chandni, Hendrik Ombach, Paul Olson, Perry F. Renshaw, and Shami Kanekar. Increased anxiety and anhedonia in female rats following exposure to altitude. High Alt Med Biol. 19:81-90, 2018.-Anxiety disorders are chronic, highly prevalent conditions, often comorbid with depression. Both anxiety and depression form major risk factors for suicide. Living at altitude is associated with higher rates of depression and suicide, leading us to address whether anxiety disorders may also be amplified at altitude. Using a novel translational animal model, we previously showed that depression-like behavior increases with altitude of housing in female, but not male rats. We now use this model to examine the effects of altitude on both anxiety-like behavior and anhedonia, a core symptom of depression. After housing for a week at sea level, 4500 or 10,000 ft, rats were evaluated for anxiety in the open-field test or the elevated plus maze, and anhedonia in the sucrose preference test. Another group was tested at baseline. Anxiety-like behavior increased in females housed at altitude. In females, lower sucrose preference was seen in those housed at 10,000 ft versus those at sea level. Males showed no change in anxiety or anhedonia across groups. These data suggest that living at moderate-high altitude may pose a risk factor for those vulnerable to anxiety disorders, with the potential to be particularly detrimental to females at altitude.
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Affiliation(s)
- Chandni Sheth
- 1 Diagnostic Neuroimaging, Department of Psychiatry, University of Utah School of Medicine , Salt Lake City, Utah
| | - Hendrik Ombach
- 1 Diagnostic Neuroimaging, Department of Psychiatry, University of Utah School of Medicine , Salt Lake City, Utah
| | - Paul Olson
- 1 Diagnostic Neuroimaging, Department of Psychiatry, University of Utah School of Medicine , Salt Lake City, Utah
| | - Perry F Renshaw
- 1 Diagnostic Neuroimaging, Department of Psychiatry, University of Utah School of Medicine , Salt Lake City, Utah.,2 VISN 19 Mental Illness Research, Education and Clinical Center (MIRREC) , Salt Lake City Veterans Health Administration, Salt Lake City, Utah
| | - Shami Kanekar
- 1 Diagnostic Neuroimaging, Department of Psychiatry, University of Utah School of Medicine , Salt Lake City, Utah.,2 VISN 19 Mental Illness Research, Education and Clinical Center (MIRREC) , Salt Lake City Veterans Health Administration, Salt Lake City, Utah
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Lipman GS, Pomeranz D, Burns P, Phillips C, Cheffers M, Evans K, Jurkiewicz C, Juul N, Hackett P. Budesonide Versus Acetazolamide for Prevention of Acute Mountain Sickness. Am J Med 2018; 131:200.e9-200.e16. [PMID: 28668540 DOI: 10.1016/j.amjmed.2017.05.034] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Revised: 05/25/2017] [Accepted: 05/26/2017] [Indexed: 11/25/2022]
Abstract
BACKGROUND Inhaled budesonide has been suggested as a novel prevention for acute mountain sickness. However, efficacy has not been compared with the standard acute mountain sickness prevention medication acetazolamide. METHODS This double-blind, randomized, placebo-controlled trial compared inhaled budesonide versus oral acetazolamide versus placebo, starting the morning of ascent from 1240 m (4100 ft) to 3810 m (12,570 ft) over 4 hours. The primary outcome was acute mountain sickness incidence (headache and Lake Louise Questionnaire ≥3 and another symptom). RESULTS A total of 103 participants were enrolled and completed the study; 33 (32%) received budesonide, 35 (34%) acetazolamide, and 35 (34%) placebo. Demographics were not different between the groups (P > .09). Acute mountain sickness prevalence was 73%, with severe acute mountain sickness of 47%. Fewer participants in the acetazolamide group (n = 15, 43%) developed acute mountain sickness compared with both budesonide (n = 24, 73%) (odds ratio [OR] 3.5, 95% confidence interval [CI] 1.3-10.1) and placebo (n = 22, 63%) (OR 0.5, 95% CI 0.2-1.2). Severe acute mountain sickness was reduced with acetazolamide (n = 11, 31%) compared with both budesonide (n = 18, 55%) (OR 2.6, 95% CI 1-7.2) and placebo (n = 19, 54%) (OR 0.4, 95% CI 0.1-1), with a number needed to treat of 4. CONCLUSION Budesonide was ineffective for the prevention of acute mountain sickness, and acetazolamide was preventive of severe acute mountain sickness taken just before rapid ascent.
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Affiliation(s)
- Grant S Lipman
- Department of Emergency Medicine, Stanford University School of Medicine, Palo Alto, Calif.
| | - David Pomeranz
- Department of Emergency Medicine, Stanford University School of Medicine, Palo Alto, Calif
| | - Patrick Burns
- Department of Emergency Medicine, Stanford University School of Medicine, Palo Alto, Calif
| | - Caleb Phillips
- Department of Computational Science, University of Colorado, Boulder
| | - Mary Cheffers
- Emergency Medicine Residency L.A. County, University of Southern California, Los Angeles
| | - Kristina Evans
- Stanford-Kaiser Emergency Medicine Residency, Palo Alto, Calif
| | - Carrie Jurkiewicz
- Emeregency Medicine Residency, University of Chicago School of Medicine, Ill
| | - Nick Juul
- Division of Pulmonary & Critical Care Medicine, Stanford University School of Medicine, Palo Alto, Calif
| | - Peter Hackett
- Department of Emergency Medicine, Institute for Altitude Medicine, University of Colorado, Boulder
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21
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Impact of a Newly Constructed Motor Vehicle Road on Altitude Illness in the Nepal Himalayas. Wilderness Environ Med 2017; 28:332-338. [DOI: 10.1016/j.wem.2017.06.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2017] [Revised: 06/01/2017] [Accepted: 06/09/2017] [Indexed: 11/22/2022]
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22
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Bernardi E, Pomidori L, Cavallari D, Mandolesi G, Cogo A. Residence at Moderate Versus Low Altitude Is Effective at Maintaining Higher Oxygen Saturation During Exercise and Reducing Acute Mountain Sickness Following Fast Ascent to 4559 m. Wilderness Environ Med 2017; 28:122-126. [DOI: 10.1016/j.wem.2017.02.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 02/16/2017] [Accepted: 02/22/2017] [Indexed: 10/19/2022]
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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: 224] [Impact Index Per Article: 32.0] [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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Gong W, Xu P, Guo S, Li X, Jin Z, Zhao Y, Fan M, Xue M. Effect of hypoxia on the pharmacokinetics and metabolism of zaleplon as a probe of CYP3A1/2 activity. RSC Adv 2017. [DOI: 10.1039/c7ra03025h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The objective of this study was to compare the pharmacokinetics and metabolism of zaleplon (ZAL) in rats under hypoxic and normoxic condition and the effect of hypoxia on the protein expression and activities of the main metabolic enzyme CYP3A1/2.
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Affiliation(s)
- Wenwen Gong
- Department of Pharmacology
- Beijing Laboratory for Biomedical Detection Technology and Instrument
- School of Basic Medical Sciences
- Capital Medical University
- Beijing 100069
| | - Pingxiang Xu
- Department of Pharmacology
- Beijing Laboratory for Biomedical Detection Technology and Instrument
- School of Basic Medical Sciences
- Capital Medical University
- Beijing 100069
| | - Shanshan Guo
- Department of Pharmacology
- Beijing Laboratory for Biomedical Detection Technology and Instrument
- School of Basic Medical Sciences
- Capital Medical University
- Beijing 100069
| | - Xiaorong Li
- Department of Pharmacology
- Beijing Laboratory for Biomedical Detection Technology and Instrument
- School of Basic Medical Sciences
- Capital Medical University
- Beijing 100069
| | - Zengliang Jin
- Department of Pharmacology
- Beijing Laboratory for Biomedical Detection Technology and Instrument
- School of Basic Medical Sciences
- Capital Medical University
- Beijing 100069
| | - Yuming Zhao
- Department of Pharmacology
- Beijing Laboratory for Biomedical Detection Technology and Instrument
- School of Basic Medical Sciences
- Capital Medical University
- Beijing 100069
| | - Ming Fan
- Department of Nerobiology
- School of Basic Medical Sciences
- Capital Medical University
- Beijing
- China
| | - Ming Xue
- Department of Pharmacology
- Beijing Laboratory for Biomedical Detection Technology and Instrument
- School of Basic Medical Sciences
- Capital Medical University
- Beijing 100069
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Chapman RF, Karlsen T, Ge RL, Stray-Gundersen J, Levine BD. Living altitude influences endurance exercise performance change over time at altitude. J Appl Physiol (1985) 2016; 120:1151-8. [DOI: 10.1152/japplphysiol.00909.2015] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 03/04/2016] [Indexed: 11/22/2022] Open
Abstract
For sea level based endurance athletes who compete at low and moderate altitudes, adequate time for acclimatization to altitude can mitigate performance declines. We asked whether it is better for the acclimatizing athlete to live at the specific altitude of competition or at a higher altitude, perhaps for an increased rate of physiological adaptation. After 4 wk of supervised sea level training and testing, 48 collegiate distance runners (32 men, 16 women) were randomly assigned to one of four living altitudes (1,780, 2,085, 2,454, or 2,800 m) where they resided for 4 wk. Daily training for all subjects was completed at a common altitude from 1,250 to 3,000 m. Subjects completed 3,000-m performance trials on the track at sea level, 28 and 6 days before departure, and at 1,780 m on days 5, 12, 19, and 26 of the altitude camp. Groups living at 2,454 and 2,800 m had a significantly larger slowing of performance vs. the 1,780-m group on day 5 at altitude. The 1,780-m group showed no significant change in performance across the 26 days at altitude, while the groups living at 2,085, 2,454, and 2,800 m showed improvements in performance from day 5 to day 19 at altitude but no further improvement at day 26. The data suggest that an endurance athlete competing acutely at 1,780 m should live at the altitude of the competition and not higher. Living ∼300-1,000 m higher than the competition altitude, acute altitude performance may be significantly worse and may require up to 19 days of acclimatization to minimize performance decrements.
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Affiliation(s)
| | - Trine Karlsen
- K. G. Jebsen Center of Exercise in Medicine, Department of Circulation and Medical Imaging, Norweigan University of Science and Technology, Trondheim, Norway
| | - R.-L. Ge
- Research Center for High Altitude Medicine, Qinghai University, Qinghai, China
| | | | - Benjamin D. Levine
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, The University of Texas Southwestern Medical Center, Dallas, Texas
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Kanekar S, Bogdanova OV, Olson PR, Sung YH, D'Anci KE, Renshaw PF. Hypobaric hypoxia induces depression-like behavior in female Sprague-Dawley rats, but not in males. High Alt Med Biol 2016; 16:52-60. [PMID: 25803141 DOI: 10.1089/ham.2014.1070] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Rates of depression and suicide are higher in people living at altitude, and in those with chronic hypoxic disorders like asthma, chronic obstructive pulmonary disorder (COPD), and smoking. Living at altitude exposes people to hypobaric hypoxia, which can lower rat brain serotonin levels, and impair brain bioenergetics in both humans and rats. We therefore examined the effect of hypobaric hypoxia on depression-like behavior in rats. After a week of housing at simulated altitudes of 20,000 ft, 10,000 ft, or sea level, or at local conditions of 4500 ft (Salt Lake City, UT), Sprague Dawley rats were tested for depression-like behavior in the forced swim test (FST). Time spent swimming, climbing, or immobile, and latency to immobility were measured. Female rats housed at altitude display more depression-like behavior in the FST, with significantly more immobility, less swimming, and lower latency to immobility than those at sea level. In contrast, males in all four altitude groups were similar in their FST behavior. Locomotor behavior in the open field test did not change with altitude, thus validating immobility in the FST as depression-like behavior. Hypobaric hypoxia exposure therefore induces depression-like behavior in female rats, but not in males.
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Affiliation(s)
- Shami Kanekar
- 1 The Brain Institute, University of Utah , Salt Lake City, Utah
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27
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He L, Jiang Y, Su H, Li J, Cheng X. Vascular Endothelial Function Assessed by Postischemic Diastolic Blood Pressure Is Associated with Acclimatization and Acute Mountain Sickness. High Alt Med Biol 2016; 17:11-5. [PMID: 26977539 DOI: 10.1089/ham.2015.0070] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND This study assessed whether the brachial diastolic blood pressure (DBP) decline induced by 5-minute arm ischemia is associated with acclimatization and acute mountain sickness (AMS). METHODS Forty-two age- and body mass index-matched young male residents at sea level (<400 m) or moderate altitude (1000-2000 m above sea level) were enrolled. All subjects had never been to 3200 m before. Brachial BP was measured at a station at 1380 m altitude before and 1, 5, and 10 minutes after right arm ischemia. AMS score was evaluated after 3-day training at a high altitude of 3200 m. RESULTS In moderate altitude versus sea-level residents: (1) systolic BP curves for both arms overlapped well; (2) mean right arm DBP decline post right arm ischemia was larger, while left arm, which was not subjected to ischemia, did not show DBP decline in either group; and (3) AMS scores were significantly lower (3.19 ± 2.16 vs. 5.52 ± 4.58, p = 0.043) in those residing at moderate altitude compared to those from low altitude. There was a low negative correlation between AMS score and right arm area between curves-DBP (r = -0.320, p = 0.039). CONCLUSION Moderate altitude relative to sea-level residents had a larger mean postischemic DBP decline in weak but significant association with lower mean AMS score at 3200 m. These data suggest that differences in vascular endothelial function related to altitude of residence persist during travel to high altitude and might contribute to AMS risk.
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Affiliation(s)
- Lipeng He
- Department of Cardiology, The Second Affiliated Hospital of Nanchang University , Nanchang, Jiangxi, China
| | - Yu Jiang
- Department of Cardiology, The Second Affiliated Hospital of Nanchang University , Nanchang, Jiangxi, China
| | - Hai Su
- Department of Cardiology, The Second Affiliated Hospital of Nanchang University , Nanchang, Jiangxi, China
| | - Juxiang Li
- Department of Cardiology, The Second Affiliated Hospital of Nanchang University , Nanchang, Jiangxi, China
| | - Xiaoshu Cheng
- Department of Cardiology, The Second Affiliated Hospital of Nanchang University , Nanchang, Jiangxi, China
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28
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Kanaan NC, Lipman GS, Constance BB, Holck PS, Preuss JF, Williams SR. Reply. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 2016; 35:456-457. [PMID: 26795047 DOI: 10.7863/ultra.15.10050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Affiliation(s)
- Nicholas C Kanaan
- University of Utah, Salt Lake City, Utah USA (N.C.K.)Stanford University School of Medicine, Palo Alto, California USA (G.S.L., S.R.W.)Tacoma General Hospital, Tacoma, Washington USA (B.B.C.)University of Hawaii, Honolulu, Hawaii USA (P.S.H.)Royal Perth Hospital, Perth, Western Australia, Australia (J.F.P.)
| | - Grant S Lipman
- University of Utah, Salt Lake City, Utah USA (N.C.K.)Stanford University School of Medicine, Palo Alto, California USA (G.S.L., S.R.W.)Tacoma General Hospital, Tacoma, Washington USA (B.B.C.)University of Hawaii, Honolulu, Hawaii USA (P.S.H.)Royal Perth Hospital, Perth, Western Australia, Australia (J.F.P.)
| | - Benjamin B Constance
- University of Utah, Salt Lake City, Utah USA (N.C.K.)Stanford University School of Medicine, Palo Alto, California USA (G.S.L., S.R.W.)Tacoma General Hospital, Tacoma, Washington USA (B.B.C.)University of Hawaii, Honolulu, Hawaii USA (P.S.H.)Royal Perth Hospital, Perth, Western Australia, Australia (J.F.P.)
| | - Peter S Holck
- University of Utah, Salt Lake City, Utah USA (N.C.K.)Stanford University School of Medicine, Palo Alto, California USA (G.S.L., S.R.W.)Tacoma General Hospital, Tacoma, Washington USA (B.B.C.)University of Hawaii, Honolulu, Hawaii USA (P.S.H.)Royal Perth Hospital, Perth, Western Australia, Australia (J.F.P.)
| | - James F Preuss
- University of Utah, Salt Lake City, Utah USA (N.C.K.)Stanford University School of Medicine, Palo Alto, California USA (G.S.L., S.R.W.)Tacoma General Hospital, Tacoma, Washington USA (B.B.C.)University of Hawaii, Honolulu, Hawaii USA (P.S.H.)Royal Perth Hospital, Perth, Western Australia, Australia (J.F.P.)
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Abstract
BACKGROUND AND AIMS Altitude-related medical literature provides very few simple clinical studies relating to those on 'adventure holidays'. Systemic blood pressure has seldom been studied closely in relation to altitude. This study aimed to address both these issues and to assist GPs approached by patients for pre-trek advice. METHODS AND RESULTS A total of 17 hillwalkers, evenly distributed for gender and age, trekked gradually from moderate to extreme altitude on Mera Peak in the Himalaya, noting any altitude sickness symptoms. Heart rate, blood pressure, oxygen saturation, peak expiratory flow and core temperature were measured daily. Altitude was double-checked hourly and synchronised with each set of measurements. On each day, two individuals wore 24-h ambulatory blood pressure monitors for assessment of altitude effects. Two principal findings emerged. Firstly, none of our 17 developed altitude-related symptoms below 4000 m, consistent with the recognised protective effect of slow rate of ascent; at 3500-4000 m all showed a sharp fall on O2sat and above 4500 m symptoms arose unpredictably. Secondly, hourly blood pressure monitoring showed no altitude effect below 3500 m, but above 5000 m a marked yet asymptomatic rise with delayed and prolonged peak. CONCLUSION There may be a critical altitude above which extra vigilance is required; blood pressure here needs further research.
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Shah NM, Hussain S, Cooke M, O’Hara JP, Mellor A. Wilderness medicine at high altitude: recent developments in the field. Open Access J Sports Med 2015; 6:319-28. [PMID: 26445563 PMCID: PMC4590685 DOI: 10.2147/oajsm.s89856] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Travel to high altitude is increasingly popular. With this comes an increased incidence of high-altitude illness and therefore an increased need to improve our strategies to prevent and accurately diagnose these. In this review, we provide a summary of recent advances of relevance to practitioners who may be advising travelers to altitude. Although the Lake Louise Score is now widely used as a diagnostic tool for acute mountain sickness (AMS), increasing evidence questions the validity of doing so, and of considering AMS as a single condition. Biomarkers, such as brain natriuretic peptide, are likely correlating with pulmonary artery systolic pressure, thus potential markers of the development of altitude illness. Established drug treatments include acetazolamide, nifedipine, and dexamethasone. Drugs with a potential to reduce the risk of developing AMS include nitrate supplements, propagators of nitric oxide, and supplemental iron. The role of exercise in the development of altitude illness remains hotly debated, and it appears that the intensity of exercise is more important than the exercise itself. Finally, despite copious studies demonstrating the value of preacclimatization in reducing the risk of altitude illness and improving performance, an optimal protocol to preacclimatize an individual remains elusive.
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Affiliation(s)
- Neeraj M Shah
- Division of Asthma, Allergy and Lung Biology, King’s College London, UK
| | - Sidra Hussain
- School of Medicine, University College London, London, UK
| | - Mark Cooke
- Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, UK
| | - John P O’Hara
- Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, UK
| | - Adrian Mellor
- Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, UK
- Academic Department of Military Anaesthesia and Critical Care, Royal Centre for Defence Medicine, Birmingham, UK
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Impact of Study Design on Reported Incidences of Acute Mountain Sickness: A Systematic Review. High Alt Med Biol 2015; 16:204-15. [DOI: 10.1089/ham.2015.0022] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
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Luks AM, McIntosh SE, Grissom CK, Auerbach PS, Rodway GW, Schoene RB, Zafren K, Hackett PH. Wilderness Medical Society practice guidelines for the prevention and treatment of acute altitude illness: 2014 update. Wilderness Environ Med 2015; 25:S4-14. [PMID: 25498261 DOI: 10.1016/j.wem.2014.06.017] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 06/16/2014] [Indexed: 10/24/2022]
Abstract
To provide guidance to clinicians about best practices, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for prevention and treatment of acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. These guidelines present the main prophylactic and therapeutic modalities for each disorder and provide recommendations about their role in disease management. Recommendations are graded based on the quality of supporting evidence and balance between the benefits and risks/burdens according to criteria put forth by the American College of Chest Physicians. The guidelines also provide suggested approaches to prevention and management of each disorder that incorporate these recommendations. This is an updated version of the original WMS Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness published in Wilderness & Environmental Medicine 2010;21(2):146-155.
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Affiliation(s)
- Andrew M Luks
- Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, WA (Drs Luks and Schoene).
| | | | - Colin K Grissom
- Pulmonary and Critical Care Division, Intermountain Medical Center and the University of Utah, Salt Lake City, UT (Dr Grissom)
| | - Paul S Auerbach
- Department of Surgery, Division of Emergency Medicine, Stanford University School of Medicine, Stanford, CA (Drs Auerbach and Zafren)
| | - George W Rodway
- Division of Health Sciences, University of Nevada, Reno, NV (Dr Rodway)
| | - Robert B Schoene
- Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, WA (Drs Luks and Schoene); East Bay Regional Pulmonary and Critical Care Medicine Associates, Berkeley, CA (Dr Schoene)
| | - Ken Zafren
- Department of Surgery, Division of Emergency Medicine, Stanford University School of Medicine, Stanford, CA (Drs Auerbach and Zafren); Himalayan Rescue Association, Kathmandu, Nepal (Dr Zafren)
| | - Peter H Hackett
- Division of Emergency Medicine, Altitude Research Center, University of Colorado School of Medicine, Aurora and the Institute for Altitude Medicine, Telluride, CO (Dr Hackett)
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Gong W, Liu S, Xu P, Fan M, Xue M. Simultaneous Quantification of Diazepam and Dexamethasone in Plasma by High-Performance Liquid Chromatography with Tandem Mass Spectrometry and Its Application to a Pharmacokinetic Comparison between Normoxic and Hypoxic Rats. Molecules 2015; 20:6901-12. [PMID: 25913929 PMCID: PMC6272486 DOI: 10.3390/molecules20046901] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 04/07/2015] [Accepted: 04/13/2015] [Indexed: 11/16/2022] Open
Abstract
In order to investigate the pharmacokinetics of a combination of diazepam and dexamethasone under hypoxic conditions, a novel, sensitive and specific liquid chromatography with tandem mass spectrometry (LC-MS/MS) method for the simultaneous determination of diazepam and dexamethasone in rat plasma was developed and validated. The chromatographic separation of analytes was successfully achieved on an XTerra® MS C18 column using a gradient elution of methanol and water containing 0.1% formic acid at a flow rate of 0.5 mL/min. This method demonstrated good linearity and no endogenous material interferences. The linear ranges were 1.0-100 ng/mL for diazepam and 2.0-200 ng/mL for dexamethasone. The intra- and inter-day precision for the two compounds in plasma were lower than 10.0%, and the accuracy was between -7.9% and 11.5%. Our method was then successfully applied in a pharmacokinetic comparison between normoxic and hypoxic rats. The results indicated that there were significant differences in the main pharmacokinetics parameters of diazepam and dexamethasone between normoxic and hypoxic rats. The results provide the important and valuable information for discovering and developing novel anti-hypoxia drug combinations, as well as a better understanding of the safety and efficacy of these drugs.
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Affiliation(s)
- Wenwen Gong
- Department of Neurobiology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China.
- Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China.
| | - Shuhong Liu
- Department of Cognitive Sciences, Beijing Institute of Basic Medical Sciences, Beijing 100850, China.
| | - Pingxiang Xu
- Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China.
- Beijing Laboratory for Biomedical Detection Technology and Instrument, Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China.
| | - Ming Fan
- Department of Neurobiology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China.
- Department of Cognitive Sciences, Beijing Institute of Basic Medical Sciences, Beijing 100850, China.
| | - Ming Xue
- Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China.
- Beijing Laboratory for Biomedical Detection Technology and Instrument, Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China.
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Croughs M, Van Gompel A, Rameckers S, Van den Ende J. Serious altitude illness in travelers who visited a pre-travel clinic. J Travel Med 2014; 21:403-9. [PMID: 25238200 DOI: 10.1111/jtm.12160] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 06/29/2014] [Accepted: 07/15/2014] [Indexed: 02/06/2023]
Abstract
BACKGROUND Few data are available on the incidence and predictors of serious altitude illness in travelers who visit pre-travel clinics. Travel health consultants advise on measures to be taken in case of serious altitude illness but it is not clear if travelers adhere to these recommendations. METHODS Visitors to six travel clinics who planned to travel to an altitude of ≥3,000 m were asked to complete a diary from the first day at 2,000 m until 3 days after reaching the maximum sleeping altitude. Serious altitude illness was defined as having symptoms of serious acute mountain sickness (AMS score ≥ 6) and/or cerebral edema and/or pulmonary edema. RESULTS The incidence of serious altitude illness in the 401 included participants of whom 90% reached ≥4,000 m, was 35%; 23% had symptoms of serious AMS, 25% symptoms of cerebral edema, and 13% symptoms of pulmonary edema. Independent predictors were young age, the occurrence of dark urine, travel in South America or Africa, and lack of acclimatization between 1,000 and 2,500 m. Acetazolamide was brought along by 77% of the responders of whom 41% took at least one dose. Of those with serious altitude illness, 57% had taken at least one dose of acetazolamide, 20% descended below 2,500 m on the same day or the next, and 11% consulted a physician. CONCLUSIONS Serious altitude illness was a very frequent problem in travelers who visited pre-travel clinics. Young age, dark urine, travel in South America or Africa, and lack of acclimatization nights at moderate altitude were independent predictors. Furthermore, we found that seriously ill travelers seldom followed the advice to descend and to visit a physician.
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Affiliation(s)
- Mieke Croughs
- Department of Environment, GGD Hart voor Brabant, 's-Hertogenbosch, The Netherlands; Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
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Chapman RF, Laymon AS, Levine BD. Timing of arrival and pre-acclimatization strategies for the endurance athlete competing at moderate to high altitudes. High Alt Med Biol 2014; 14:319-24. [PMID: 24377334 DOI: 10.1089/ham.2013.1022] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
With the wide array of endurance sport competition offerings at moderate and high altitudes, clinicians are frequently asked about best practice recommendations regarding arrival times prior to the event and acclimatization guidelines. This brief review will offer data and current advice on when to arrive at altitude and various potential sea level-based pre-acclimatization strategies in an effort to maximize performance and minimize the risk of altitude sickness.
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Affiliation(s)
- Robert F Chapman
- 1 Human Performance Laboratory, Department of Kinesiology, Indiana University , Bloomington, Indiana
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Dehnert C, Böhm A, Grigoriev I, Menold E, Bärtsch P. Sleeping in moderate hypoxia at home for prevention of acute mountain sickness (AMS): a placebo-controlled, randomized double-blind study. Wilderness Environ Med 2014; 25:263-71. [PMID: 24931591 DOI: 10.1016/j.wem.2014.04.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2013] [Revised: 04/03/2014] [Accepted: 04/04/2014] [Indexed: 11/19/2022]
Abstract
OBJECTIVE Acclimatization at natural altitude effectively prevents acute mountain sickness (AMS). It is, however, unknown whether prevention of AMS is also possible by only sleeping in normobaric hypoxia. METHODS In a placebo-controlled, double-blind study 76 healthy unacclimatized male subjects, aged 18 to 50 years, slept for 14 consecutive nights at either a fractional inspired oxygen (Fio2) of 0.14 to 0.15 (average target altitude 3043 m; treatment group) or 0.209 (control group). Four days later, AMS scores and incidence of AMS were assessed during a 20-hour exposure in normobaric hypoxia at Fio2 = 0.12 (equivalent to 4500 m). RESULTS Because of technical problems with the nitrogen generators, target altitude was not achieved in the tents and only 21 of 37 subjects slept at an average altitude considered sufficient for acclimatization (>2200 m; average, 2600 m). Therefore, in a subgroup analysis these subjects were compared with the 21 subjects of the control group with the lowest sleeping altitude. This analysis showed a significantly lower AMS-C score (0.38; 95% CI, 0.21 to 0.54) vs 1.10; 95% CI, 0.57 to 1.62; P = .04) and lower Lake Louise Score (3.1; 95% CI, 2.2 to 4.1 vs 5.1; 95% CI, 3.6 to 6.6; P = .07) for the treatment subgroup. The incidence of AMS defined as an AMS-C score greater than 0.70 was also significantly lower (14% vs 52%; P < .01). CONCLUSIONS Sleeping 14 consecutive nights in normobaric hypoxia (equivalent to 2600 m) reduced symptoms and incidence of AMS 4 days later on exposure to 4500 m.
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Affiliation(s)
- Christoph Dehnert
- University Hospital, Medical Clinic, Internal Medicine VII, Sports Medicine, Heidelberg, Germany.
| | - Astrid Böhm
- University Hospital, Medical Clinic, Internal Medicine VII, Sports Medicine, Heidelberg, Germany
| | - Igor Grigoriev
- University Hospital, Medical Clinic, Internal Medicine VII, Sports Medicine, Heidelberg, Germany
| | - Elmar Menold
- University Hospital, Medical Clinic, Internal Medicine VII, Sports Medicine, Heidelberg, Germany
| | - Peter Bärtsch
- University Hospital, Medical Clinic, Internal Medicine VII, Sports Medicine, Heidelberg, Germany
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Medical Services at Ultra-Endurance Foot Races in Remote Environments: Medical Issues and Consensus Guidelines. Sports Med 2014; 44:1055-69. [DOI: 10.1007/s40279-014-0189-3] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Correlation between blood pressure changes and AMS, sleeping quality and exercise upon high-altitude exposure in young Chinese men. Mil Med Res 2014; 1:19. [PMID: 25722875 PMCID: PMC4340834 DOI: 10.1186/2054-9369-1-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 07/17/2014] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Excessive elevation of arterial blood pressure (BP) at high altitude can be detrimental to our health due to acute mountain sickness (AMS) or some AMS symptoms. This prospective and observational study aimed to elucidate blood pressure changes induced by exposure to high-altitude hypoxia and the relationships of these changes with AMS prevalence, AMS severity, sleep quality and exercise condition in healthy young men. METHODS A prospective observational study was performed in 931 male young adults exposed to high altitude at 3,700 m (Lhasa) from low altitude (LA, 500 m). Blood pressure measurement and AMS symptom questionnaires were performed at LA and on day 1, 3, 5, and 7 of exposure to high altitude. Lake Louise criteria were used to diagnose AMS. Likewise, the Athens Insomnia Scale (AIS) and the Epworth Sleepiness Scale (ESS) were filled out at LA and on day 1, 3, and 7 of exposure to high altitude. RESULTS After acute exposure to 3,700 m, diastolic blood pressure (DBP) and mean arterial blood pressure (MABP) rose gradually and continually (P < 0.05). Analysis showed a relationship with AMS for only MABP (P < 0.05) but not for SBP and DBP (P > 0.05). Poor sleeping quality was generally associated with higher SBP or DBP at high altitude, although inconsistent results were obtained at different time (P < 0.05). SBP and Pulse BP increased noticeably after high-altitude exercise (P < 0.05). CONCLUSIONS Our data demonstrate notable blood pressure changes under exposure to different high-altitude conditions: 1) BP increased over time. 2) Higher BP generally accompanied poor sleeping quality and higher incidence of AMS. 3) SBP and Pulse BP were higher after high-altitude exercise. Therefore, we should put more effort into monitoring BP after exposure to high altitude in order to guard against excessive increases in BP.
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Zafren K. Prevention of high altitude illness. Travel Med Infect Dis 2014; 12:29-39. [DOI: 10.1016/j.tmaid.2013.12.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 12/05/2013] [Accepted: 12/10/2013] [Indexed: 11/28/2022]
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Staab JE, Beidleman BA, Muza SR, Fulco CS, Rock PB, Cymerman A. Efficacy of residence at moderate versus low altitude on reducing acute mountain sickness in men following rapid ascent to 4300 m. High Alt Med Biol 2013; 14:13-8. [PMID: 23537255 DOI: 10.1089/ham.2012.1065] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
To determine if residence at moderate (~2000 m) compared to low (<50 m) altitude reduces acute mountain sickness (AMS) in men during subsequent rapid ascent to a higher altitude. Nine moderate-altitude residents (MAR) and 18 sea-level residents (SLR) completed the Environmental Symptoms Questionnaire (ESQ) at their respective baseline residence and again at 12, 24, 48, and 72 h at 4300 m to assess the severity and prevalence of AMS. AMS cerebral factor score (AMS-C) was calculated from the ESQ at each time point. AMS was judged to be present if AMS-C was ≥0.7. Resting end-tidal CO2 (PETco2) and arterial oxygen saturation (Sao2) were assessed prior to and at 24, 48, and 72 h at 4300 m. Resting venous blood samples were collected prior to and at 72 h at 4300 m to estimate plasma volume (PV) changes. MAR compared to SLR: 1) AMS severity at 4300 was lower (p<0.05) at 12 h (0.50±0.69 vs. 1.48±1.28), 24 h (0.15±0.19 vs. 1.39±1.19), 48 h (0.10±0.18 vs. 1.37±1.49) and 72 h (0.08±0.12 vs. 0.69±0.70); 2) AMS prevalence at 4300 was lower (p<0.05) at 12 h (22% vs. 72%), 24 h (0% vs. 56%), 48 h (0% vs. 56%), and 72 h (0% vs. 45%); 3) resting Sao2 (%) was lower (p<0.05) at baseline (95±1 vs. 99±1) but higher (p<0.05) at 4300 at 24 h (86±2 vs. 81±5), 48 h (88±3 vs. 83±6), and 72 h (88±2 vs. 83±5); and 4) PV (%) did not differ at 72 h at 4300 m in the MAR (4.5±6.7) but was reduced for the SLR (-8.1±10.4). These results suggest that ventilatory and hematological acclimatization acquired while living at moderate altitude, as indicated by a higher resting Sao2 and no reduction in PV during exposure to a higher altitude, is associated with greatly reduced AMS after rapid ascent to high altitude.
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Affiliation(s)
- Janet E Staab
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760, USA.
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Sun NL, Wang LY, Xi Y, Hu QZ. Effect of renin–angiotensin system on arterial function in persons with acute mountain sickness. Int J Cardiol 2013. [DOI: 10.1016/j.ijcard.2012.11.029] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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Abstract
A 45-year-old healthy man wishes to climb Mount Kilimanjaro (5895 m) in a 5-day period, starting at 1800 m. The results of a recent exercise stress test were normal; he runs 10 km 4 or 5 times per week and finished a marathon in less than 4 hours last year. He wants to know how he can prevent becoming ill at high altitude and whether training or sleeping under normobaric hypoxic conditions in the weeks before the ascent would be helpful. What would you advise?
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Affiliation(s)
- Peter Bärtsch
- University Clinic, Department of Internal Medicine, Division VII Sports Medicine, Heidelberg, Germany.
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Abstract
Acute mountain sickness (AMS) and large decrements in endurance exercise performance occur when unacclimatized individuals rapidly ascend to high altitudes. Six altitude and hypoxia preacclimatization strategies were evaluated to determine their effectiveness for minimizing AMS and improving performance during altitude exposures. Strategies using hypobaric chambers or true altitude were much more effective overall than those using normobaric hypoxia (breathing, <20.9% oxygen).
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Weng YM, Chiu YH, Lynn JJ, Li WC, Wang SH, Kao WF, Hsu TY, Chiu TF, Lin YJ, Chan CW. Different duration of high-altitude pre-exposure associated with the incidence of acute mountain sickness on Jade Mountain. Am J Emerg Med 2013; 31:1113-7. [PMID: 23688567 DOI: 10.1016/j.ajem.2013.03.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 03/15/2013] [Accepted: 03/16/2013] [Indexed: 11/17/2022] Open
Abstract
OBJECTIVE The objective of this study is to determine the association between the duration of high-altitude (>3000 m) pre-exposure and acute mountain sickness (AMS) incidence. METHODS A prospective observational study was conducted on 2 random days each month from April 2007 to March 2008 at Paiyun Lodge (3402 m), Jade Mountain, Taiwan. Demographic data, prior AMS history, symptoms, and scores and the days and times of high-altitude pre-exposure within the preceding 2 months were obtained from lowland (<1500 m) trekkers. RESULTS Totally, 1010 questionnaires were analyzed; 106, 76, and 828 trekkers had pre-exposure lasting at least 3 days (group 1), less than 3 days (group 2), and 0 days (group 3), respectively. Acute mountain sickness incidence was significantly higher in groups 2 and 3 than in group 1 (21.70%, 35.53%, 37.08%, respectively; P = .008). Logistic regression analysis indicated a significantly lower AMS risk in group 1 (group 1, P = .004; odds ratio [OR], 0.479; 95% confidence interval [CI], 0.290-0.791; group 2, P = .226; OR, 0.725; 95% CI, 0.430-1.221). In group 1, 28 and 78 trekkers had single and intermittent multiple pre-exposure, respectively. There was no difference in the incidence or severity of AMS symptoms between single and intermittent multiple pre-exposure (AMS, P = .838; headache, P = .891; dizziness or lightheadedness, P = .414; fatigue and/or weakness, P = .957; gastrointestinal symptoms, P = .257; difficulty sleeping, P = .804; AMS score, P = .796). CONCLUSIONS High-altitude pre-exposure lasting at least 3 days within the preceding 2 months was associated with a significant lower AMS incidence during a subsequent ascent among Jade Mountain trekkers.
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Affiliation(s)
- Yi-Ming Weng
- Department of Emergency Medicine, Chang Gung Memorial Hospital at Linkou, Taoyuan, Taiwan
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Luks AM. Clinician's corner: What do we know about safe ascent rates at high altitude? High Alt Med Biol 2013; 13:147-52. [PMID: 22994513 DOI: 10.1089/ham.2012.1055] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Although pharmacologic strategies are available for decreasing the risk of acute altitude illness, the best means of preventing these problems remains undertaking an adequately slow ascent. Guidelines regarding appropriate ascent rates have been published in various forums, and while these guidelines are generally similar to each other in regards to the recommended ascent rates and use of rest days, there is actually little evidence in the literature supporting the particular recommendations. The purpose of this review is to consider these guidelines and the issue of ascent rates in greater detail. Following a discussion of the evidence regarding ascent rates and acclimatization, the review considers several unanswered questions regarding the current guidelines, including the applicability of the guidelines for all altitude travelers, how best to determine the ascent rate, how to implement rest days, and whether pre-acclimatization strategies can be used to facilitate faster than recommended ascents. Given the current state of evidence, there is no reason to alter the current guidelines, as they likely work for the substantial majority of high altitude travelers. It is individuals traveling to high altitude for the first time for whom they remain most important, while those individuals with substantial prior experience at high altitude may opt for faster or slower ascent rates based on their prior experience. Rest days should remain a part of any ascent profile and should be used following any large gains in elevation rather than simply at specified time intervals. Pre-acclimatization strategies may decrease the risk of acute altitude illness but there is insufficient evidence to suggest they can be used to facilitate faster than recommended ascents. Further research may allow changes in practice in the future but for the time being, adherence to the current recommendations is the prudent approach for the majority of high altitude travelers.
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Affiliation(s)
- Andrew M Luks
- Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington 98104, USA.
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Lipman GS, Kanaan NC, Holck PS, Constance BB, Gertsch JH. Ibuprofen prevents altitude illness: a randomized controlled trial for prevention of altitude illness with nonsteroidal anti-inflammatories. Ann Emerg Med 2012; 59:484-90. [PMID: 22440488 DOI: 10.1016/j.annemergmed.2012.01.019] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 01/05/2012] [Accepted: 01/13/2012] [Indexed: 11/26/2022]
Abstract
STUDY OBJECTIVE Acute mountain sickness occurs in more than 25% of the tens of millions of people who travel to high altitude each year. Previous studies on chemoprophylaxis with nonsteroidal anti-inflammatory drugs are limited in their ability to determine efficacy. We compare ibuprofen versus placebo in the prevention of acute mountain sickness incidence and severity on ascent from low to high altitude. METHODS Healthy adult volunteers living at low altitude were randomized to ibuprofen 600 mg or placebo 3 times daily, starting 6 hours before ascent from 1,240 m (4,100 ft) to 3,810 m (12,570 ft) during July and August 2010 in the White Mountains of California. The main outcome measures were acute mountain sickness incidence and severity, measured by the Lake Louise Questionnaire acute mountain sickness score with a diagnosis of ≥ 3 with headache and 1 other symptom. RESULTS Eighty-six participants completed the study; 44 (51%) received ibuprofen and 42 (49%) placebo. There were no differences in demographic characteristics between the 2 groups. Fewer participants in the ibuprofen group (43%) developed acute mountain sickness compared with those receiving placebo (69%) (odds ratio 0.3, 95% confidence interval 0.1 to 0.8; number needed to treat 3.9, 95% confidence interval 2 to 33). The acute mountain sickness severity was higher in the placebo group (4.4 [SD 2.6]) than individuals receiving ibuprofen (3.2 [SD 2.4]) (mean difference 0.9%; 95% confidence interval 0.3% to 3.0%). CONCLUSION Compared with placebo, ibuprofen was effective in reducing the incidence of acute mountain sickness.
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Affiliation(s)
- Grant S Lipman
- Division of Emergency Medicine, Stanford University School of Medicine, Palo Alto, CA, USA. grant
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Rodway GW, Muza SR. Fighting in Thin Air: Operational Wilderness Medicine in High Asia. Wilderness Environ Med 2011; 22:297-303. [DOI: 10.1016/j.wem.2011.08.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Revised: 07/02/2011] [Accepted: 08/25/2011] [Indexed: 10/14/2022]
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Croughs M, Van Gompel A, Van den Ende J. Acute mountain sickness in travelers who consulted a pre-travel clinic. J Travel Med 2011; 18:337-43. [PMID: 21896098 DOI: 10.1111/j.1708-8305.2011.00537.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND The main objective of this study was to investigate the incidence and predictors of acute mountain sickness (AMS) in travelers who consulted a pre-travel clinic and the compliance with advices concerning this condition. METHODS A post-travel questionnaire was sent to clients of five travel clinics who planned to climb above 2,000 m. RESULTS The response was 77% and the data of all 744 respondents who stayed above 2,500 m were used for the analysis. Eighty-seven percent (646) read and understood the written advices on AMS. The incidence of AMS was 25% (184), and the predictors were previous AMS [odds ratio (OR) 2.2], female sex (OR 1.6), age (OR 0.98 per year), maximum sleeping altitude (OR 1.2 per 500 m), and the number of nights between 1,500 and 2,500 m (OR 0.9 per night). Eighty-seven percent of respondents understood the written advices about AMS but 21% did not read or understand the use of acetazolamide. Forty percent spent less than two nights between 1,500 and 2,500 m and 43% climbed more than 500 m/d once above 2,500 m. Acetazolamide was brought along by 541 respondents (72%) and 116 (16%) took it preventively. Of those with AMS 62 (34%) took acetazolamide treatment and 87 (47%) climbed higher despite AMS symptoms. The average preventive dose of acetazolamide was 250 mg/d, while the average curative dose was 375 mg/d. We found no relation between acetazolamide prevention and AMS (p = 0.540). CONCLUSIONS The incidence of AMS in travelers who stayed above 2,500 m was 25%. Predictors were previous AMS, female sex, age, maximum overnight altitude, and the number of nights between 1,500 and 2,500 m. Only half of these travelers followed the preventive and curative advices and 21% did not read or understand the use of acetazolamide. We found no preventive effect of a low dose of acetazolamide in this retrospective observational study.
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Affiliation(s)
- Mieke Croughs
- GGD Hart voor Brabant, Community Health Service,'s-Hertogenbosch, The Netherlands.
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Fulco CS, Muza SR, Beidleman BA, Demes R, Staab JE, Jones JE, Cymerman A. Effect of repeated normobaric hypoxia exposures during sleep on acute mountain sickness, exercise performance, and sleep during exposure to terrestrial altitude. Am J Physiol Regul Integr Comp Physiol 2011; 300:R428-36. [DOI: 10.1152/ajpregu.00633.2010] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There is an expectation that repeated daily exposures to normobaric hypoxia (NH) will induce ventilatory acclimatization and lessen acute mountain sickness (AMS) and the exercise performance decrement during subsequent hypobaric hypoxia (HH) exposure. However, this notion has not been tested objectively. Healthy, unacclimatized sea-level (SL) residents slept for 7.5 h each night for 7 consecutive nights in hypoxia rooms under NH [ n = 14, 24 ± 5 (SD) yr] or “sham” ( n = 9, 25 ± 6 yr) conditions. The ambient percent O2 for the NH group was progressively reduced by 0.3% [150 m equivalent (equiv)] each night from 16.2% (2,200 m equiv) on night 1 to 14.4% (3,100 m equiv) on night 7, while that for the ventilatory- and exercise-matched sham group remained at 20.9%. Beginning at 25 h after sham or NH treatment, all subjects ascended and lived for 5 days at HH (4,300 m). End-tidal Pco2, O2 saturation (SaO2), AMS, and heart rate were measured repeatedly during daytime rest, sleep, or exercise (11.3-km treadmill time trial). From pre- to posttreatment at SL, resting end-tidal Pco2 decreased ( P < 0.01) for the NH (from 39 ± 3 to 35 ± 3 mmHg), but not for the sham (from 39 ± 2 to 38 ± 3 mmHg), group. Throughout HH, only sleep SaO2 was higher (80 ± 1 vs. 76 ± 1%, P < 0.05) and only AMS upon awakening was lower (0.34 ± 0.12 vs. 0.83 ± 0.14, P < 0.02) in the NH than the sham group; no other between-group rest, sleep, or exercise differences were observed at HH. These results indicate that the ventilatory acclimatization induced by NH sleep was primarily expressed during HH sleep. Under HH conditions, the higher sleep SaO2 may have contributed to a lessening of AMS upon awakening but had no impact on AMS or exercise performance for the remainder of each day.
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Affiliation(s)
- Charles S. Fulco
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Stephen R. Muza
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Beth A. Beidleman
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Robby Demes
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Janet E. Staab
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Juli E. Jones
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Allen Cymerman
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
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Abstract
For many low-altitude (<1500 m) residents, their travel itineraries may cause them to ascend rapidly to high (>2400 m) altitudes without having the time to develop an adequate degree of altitude acclimatization. Prior to departing on these trips, low-altitude residents can induce some degree of altitude acclimatization by ascending to moderate (>1500 m) or high altitudes during either continuous or intermittent altitude preexposures. Generally, the degree of altitude acclimatization developed is proportional to the altitude attained and the duration of exposure. The available evidence suggests that continuous residence at 2200 m or higher for 1 to 2 days or daily 1.5- to 4-h exposures to >4000 m induce ventilatory acclimatization. Six days at 2200 m substantially decreases acute mountain sickness (AMS) and improves work performance after rapid ascent to 4300 m. There is evidence that 5 or more days above 3000 m within the last 2 months will significantly decrease AMS during a subsequent rapid ascent to 4500 m. Exercise training during the altitude preexposures may augment improvement in physical performance. The persistence of altitude acclimatization after return to low altitude appears to be proportional to the degree of acclimatization developed. The subsequent ascent to high altitude should be scheduled as soon as possible after the last altitude preexposure.
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