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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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Doherty CJ, Chang JC, Thompson BP, Swenson ER, Foster GE, Dominelli PB. The Impact of Acetazolamide and Methazolamide on Exercise Performance in Normoxia and Hypoxia. High Alt Med Biol 2023; 24:7-18. [PMID: 36802203 DOI: 10.1089/ham.2022.0134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023] Open
Abstract
Doherty, Connor J., Jou-Chung Chang, Benjamin P. Thompson, Erik R. Swenson, Glen E. Foster, and Paolo B. Dominelli. The impact of acetazolamide and methazolamide on exercise performance in normoxia and hypoxia. High Alt Med Biol. 24:7-18, 2023.-Carbonic anhydrase (CA) inhibitors are commonly prescribed for acute mountain sickness (AMS). In this review, we sought to examine how two CA inhibitors, acetazolamide (AZ) and methazolamide (MZ), affect exercise performance in normoxia and hypoxia. First, we briefly describe the role of CA inhibition in facilitating the increase in ventilation and arterial oxygenation in preventing and treating AMS. Next, we detail how AZ affects exercise performance in normoxia and hypoxia and this is followed by a discussion on MZ. We emphasize that the overarching focus of the review is how the two drugs potentially affect exercise performance, rather than their ability to prevent/treat AMS per se, their interrelationship will be discussed. Overall, we suggest that AZ hinders exercise performance in normoxia, but may be beneficial in hypoxia. Based upon head-to-head studies of AZ and MZ in humans on diaphragmatic and locomotor strength in normoxia, MZ may be a better CA inhibitor when exercise performance is crucial at high altitude.
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Affiliation(s)
- Connor J Doherty
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada
| | - Jou-Chung Chang
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada
| | - Benjamin P Thompson
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada
| | - Erik R Swenson
- Division of Pulmonary, Critical Care and Sleep Medicine, University of Washington, Washington, USA
- Medical Service, VA Puget Sound Health Care System, Seattle, Washington, USA
| | - Glen E Foster
- School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Paolo B Dominelli
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada
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Schmickl CN, Owens RL, Orr JE, Edwards BA, Malhotra A. Side effects of acetazolamide: a systematic review and meta-analysis assessing overall risk and dose dependence. BMJ Open Respir Res 2021; 7:7/1/e000557. [PMID: 32332024 PMCID: PMC7204833 DOI: 10.1136/bmjresp-2020-000557] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2020] [Revised: 02/22/2020] [Accepted: 02/29/2020] [Indexed: 02/04/2023] Open
Abstract
Introduction Acetazolamide (AZM) is used for various conditions (eg, altitude sickness, sleep apnoea, glaucoma), but therapy is often limited by its side effect profile. Our objective was to estimate the risk of commonly reported side effects based on meta-analyses. We hypothesised that these risks are dose-dependent. Methods We queried MEDLINE/EMBASE (Medical Literature Analysis and Retrieval System Online/Excerpta Medica dataBASE) up until 04/10/2019, including any randomised placebo-controlled trial in which adults received oral AZM versus placebo reporting side effects. Eligibility assessment was performed by two independent reviewers. Data were abstracted by one reviewer who verified key entries at a second time point. For side effects reported by >3 studies a pooled effect estimate was calculated, and heterogeneity assessed via I2; for outcomes reported by >5 studies effect modification by total daily dose (EMbyTDD; <400 mg/d, 400–600 mg/d, >600 mg/d) was assessed via meta-regression. For pre-specified, primary outcomes (paraesthesias, taste disturbances, polyuria and fatigue) additional subgroup analyses were performed using demographics, intervention details, laboratory changes and risk of bias. Results We included 42 studies in the meta-analyses (Nsubjects=1274/1211 in AZM/placebo groups). AZM increased the risk of all primary outcomes (p<0.01, I2 ≤16% and low-to-moderate quality of evidence for all)—the numbers needed to harm (95% CI; nStudies) for each were: paraesthesias 2.3 (95% CI 2 to 2.7; n=39), dysgeusia 18 (95% CI 10 to 38, n=22), polyuria 17 (95% CI 9 to 49; n=22), fatigue 11 (95% CI 6 to 24; n=14). The risk for paraesthesias (beta=1.8 (95% CI 1.1 to 2.9); PEMbyTDD=0.01) and dysgeusia (beta=3.1 (95% CI 1.2 to 8.2); PEMbyTDD=0.02) increased with higher AZM doses; the risk of fatigue also increased with higher dose but non-significantly (beta=2.6 (95% CI 0.7 to 9.4); PEMbyTDD=0.14). Discussion This comprehensive meta-analysis of low-to-moderate quality evidence defines risk of common AZM side effects and corroborates dose dependence of some side effects. These results may inform clinical decision making and support efforts to establish the lowest effective dose of AZM for various conditions.
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Affiliation(s)
- Christopher N Schmickl
- Department of Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of California San Diego, La Jolla, California, USA
| | - Robert L Owens
- Department of Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of California San Diego, La Jolla, California, USA
| | - Jeremy E Orr
- Department of Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of California San Diego, La Jolla, California, USA
| | - Bradley A Edwards
- Sleep and Circadian Medicine Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia.,School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Monash University, Clayton, Victoria, Australia
| | - Atul Malhotra
- Department of Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of California San Diego, La Jolla, California, USA
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Methazolamide in high-altitude illnesses. Eur J Pharm Sci 2020; 148:105326. [PMID: 32251722 DOI: 10.1016/j.ejps.2020.105326] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 03/26/2020] [Accepted: 03/26/2020] [Indexed: 11/24/2022]
Abstract
As a carbonic anhydrase inhibitor and a methylated lipophilic analogue of acetazolamide, Methazolamide has higher lipid solubility, less plasma protein binding and renal excretion, and fewer side effects, compared to acetazolamide. Methazolamide can increase systemic metabolic acidosis and sequentially improve ventilation and oxygenation level. The increased oxygenation level leads to reduced reactive oxygen species (ROS) production, relived cerebral edema, mitigated hypoxic pulmonary vasoconstriction, abrogated hypoxic fatigue, and decreased excessive erythrocytosis. In addition to the effect as a carbonic anhydrase inhibitor, methazolamide directly activates the transcription factor anti-oxidative nuclear factor-related factor 2 (Nrf2) and inhibits interleukin-1β (IL-1β) release. These pharmacological functions of methazolamide are beneficial for the prevention and treatment of high-altitude illnesses. Besides, methazolamide causes less fatigue side effects than acetazolamide does. It is also worth noting that several studies suggested that a lower dose of methazolamide has similar prophylaxis and treatment efficacy in acute mountain sickness (AMS) to a higher dose of acetazolamide. Given methazolamide's advantages over acetazolamide, methazolamide may thus represent an alternative for acetazolamide when taken for high-altitude illnesses prophylaxis and treatment. However, more in-depth clinical trials are needed to fully evaluate this efficacy of methazolamide.
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Subudhi AW, Evero O, Reitinger J, Davis C, Gronewold J, Nichols AJ, Van‐Houten SJ, Roach RC. Combined methazolamide and theophylline improves oxygen saturation but not exercise performance or altitude illness in acute hypobaric hypoxia. Exp Physiol 2020; 106:117-125. [DOI: 10.1113/ep088461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 04/29/2020] [Indexed: 01/04/2023]
Affiliation(s)
- Andrew W. Subudhi
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
- Department of Human Physiology and Nutrition University of Colorado Colorado Springs Colorado Springs CO USA
| | - Oghenero Evero
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
| | - Jeremy Reitinger
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
| | - Christopher Davis
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
| | - Jeffrey Gronewold
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
| | - Andrew J. Nichols
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
| | | | - Robert C. Roach
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
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Bradbury KE, Yurkevicius BR, Mitchell KM, Coffman KE, Salgado RM, Fulco CS, Kenefick RW, Charkoudian N. Acetazolamide does not alter endurance exercise performance at 3,500-m altitude. J Appl Physiol (1985) 2020; 128:390-396. [PMID: 31804890 DOI: 10.1152/japplphysiol.00655.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Acetazolamide (AZ) is a medication commonly used to prevent acute mountain sickness (AMS) during rapid ascent to high altitude. However, it is unclear whether AZ use impairs exercise performance; previous literature regarding this topic is equivocal. The purpose of this study was to evaluate the impact of AZ on time-trial (TT) performance during a 30-h exposure to hypobaric hypoxia equivalent to 3,500-m altitude. Ten men [sea-level peak oxygen consumption (VO2peak): 50.8 ± 6.5 mL·kg-1·min-1; body fat %: 20.6 ± 5.2%] completed 2 30-h exposures at 3,500 m. In a crossover study design, subjects were given 500 mg/day of either AZ or a placebo. Exercise testing was completed 2 h and 24 h after ascent and consisted of 15-min steady-state treadmill walking at 40%-45% sea-level VO2peak, followed by a 2-mile self-paced treadmill TT. AMS was assessed after ~12 h and 22 h at 3,500 m. The incidence of AMS decreased from 40% with placebo to 0% with AZ. Oxygen saturation was higher (P < 0.05) in AZ versus placebo trials at the end of the TT after 2 h (85 ± 3% vs. 79 ± 3%) and 24 h (86 ± 3% vs. 81 ± 4%). There was no difference in time to complete 2 miles between AZ and PL after 2 h (20.7 ± 3.2 vs. 22.7 ± 5.0 min, P > 0.05) or 24 h (21.5 ± 3.4 vs. 21.1 ± 2.9 min, P > 0.05) of exposure to altitude. Our results suggest that AZ (500 mg/day) does not negatively impact endurance exercise performance at 3,500 m.NEW & NOTEWORTHY To our knowledge, this is the first study to examine the impact of acetazolamide (500 mg/day) versus placebo on self-paced, peak-effort exercise performance using a short-duration exercise test in a hypobaric hypoxic environment with a repeated-measures design. In the present study, acetazolamide did not impact exercise performance after 2-h or 24-h exposure to 3,500-m simulated altitude.
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Affiliation(s)
- Karleigh E Bradbury
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Beau R Yurkevicius
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts.,Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee
| | - Katherine M Mitchell
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Kirsten E Coffman
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts.,Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee
| | - Roy M Salgado
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Charles S Fulco
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts.,Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee
| | - Robert W Kenefick
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Nisha Charkoudian
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
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Heuberger JAAC, Cohen AF. Review of WADA Prohibited Substances: Limited Evidence for Performance-Enhancing Effects. Sports Med 2019; 49:525-539. [PMID: 30411235 PMCID: PMC6422964 DOI: 10.1007/s40279-018-1014-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The World Anti-Doping Agency is responsible for maintaining a Prohibited List that describes the use of substances and methods that are prohibited for athletes. The list currently contains 23 substance classes, and an important reason for the existence of this list is to prevent unfair competition due to pharmacologically enhanced performance. The aim of this review was to give an overview of the available evidence for performance enhancement of these substance classes. We searched the scientific literature through PubMed for studies and reviews evaluating the effects of substance classes on performance. Findings from double-blind, randomized controlled trials were considered as evidence for (the absence of) effects if they were performed in trained subjects measuring relevant performance outcomes. Only 5 of 23 substance classes show evidence of having the ability to enhance actual sports performance, i.e. anabolic agents, β2-agonists, stimulants, glucocorticoids and β-blockers. One additional class, growth hormone, has similar evidence but only in untrained subjects. The observed effects all relate to strength or sprint performance (and accuracy for β-blockers); there are no studies showing positive effects on reliable markers of endurance performance. For 11 classes, no well-designed studies are available, and, for the remaining six classes, there is evidence of an absence of a positive effect. In conclusion, for the majority of substance classes, no convincing evidence for performance enhancement is available, while, for the remaining classes, the evidence is based on a total of only 266 subjects from 11 studies.
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Affiliation(s)
| | - Adam F Cohen
- Centre for Human Drug Research, Zernikedreef 8, 2333 CL, Leiden, The Netherlands
- Department of Internal Medicine, Leiden University Medical Centre, Leiden, The Netherlands
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Posch AM, Dandorf S, Hile DC. The Effects of Acetazolamide on Exercise Performance at Sea Level and in Hypoxic Environments: A Review. Wilderness Environ Med 2018; 29:541-545. [PMID: 30314664 DOI: 10.1016/j.wem.2018.06.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 06/26/2018] [Indexed: 11/17/2022]
Abstract
Lowlanders rapidly ascending to high altitude (>2500 m) often develop acute mountain sickness (AMS). While acclimatization is the most effective method of reducing symptoms of AMS (ie, headache, fatigue, nausea, gastrointestinal distress, etc.), it may take several days to become fully acclimated. Prophylactic use of acetazolamide (AZ), a carbonic anhydrase inhibitor, has become a popular alternative to staged acclimatization because it can be a less time-consuming method of reducing symptoms of AMS. While numerous studies have shown the effectiveness of AZ in mitigating the symptoms of AMS, a review of the existing literature regarding the effects of AZ on submaximal and maximal exercise performance at sea level and at altitude has not been performed. Literature search identified 17 peer reviewed articles examining the effects of AZ on exercise performance both at sea level and at altitude, as well as the associated side effects of prophylactic AZ use for the attenuation of AMS. This review finds that AZ treated cohorts experience a reduction in time to exhaustion during both submaximal and maximal exercise performance at sea level. At altitude, AZ treated cohorts' recorded widely variable submaximal and maximal exercise performance. At sea level, AZ impairs submaximal and maximal exercise performance. Due to the wide variation of findings of previously published studies, the effects of AZ on submaximal and maximal exercise performance at altitude remain unknown.
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Affiliation(s)
- Alexander M Posch
- Nova Southeastern University College of Osteopathic Medicine, Davie, FL (Mr Posch) and the Department of Emergency Medicine, Johns Hopkins University, Baltimore, MD (Drs Dandorf and Hile).
| | - Stewart Dandorf
- Nova Southeastern University College of Osteopathic Medicine, Davie, FL (Mr Posch) and the Department of Emergency Medicine, Johns Hopkins University, Baltimore, MD (Drs Dandorf and Hile)
| | - David C Hile
- Nova Southeastern University College of Osteopathic Medicine, Davie, FL (Mr Posch) and the Department of Emergency Medicine, Johns Hopkins University, Baltimore, MD (Drs Dandorf and Hile)
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Dominelli PB, McNeil CJ, Vermeulen TD, Stuckless TJR, Brown CV, Dominelli GS, Swenson ER, Teppema LJ, Foster GE. Effect of acetazolamide and methazolamide on diaphragm and dorsiflexor fatigue: a randomized controlled trial. J Appl Physiol (1985) 2018; 125:770-779. [PMID: 29792554 DOI: 10.1152/japplphysiol.00256.2018] [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: 02/08/2023] Open
Abstract
Acetazolamide, a carbonic anhydrase (CA) inhibitor used clinically and to prevent acute mountain sickness, worsens skeletal muscle fatigue in animals and humans. In animals, methazolamide, a methylated analog of acetazolamide and an equally potent CA inhibitor, reportedly exacerbates fatigue less than acetazolamide. Accordingly, we sought to determine, in humans, if methazolamide would attenuate diaphragm and dorsiflexor fatigue compared with acetazolamide. Healthy men (dorsiflexor: n = 12; diaphragm: n = 7) performed fatiguing exercise on three occasions, after ingesting acetazolamide (250 mg three times a day) and then in random order, methazolamide (100 mg twice a day) or placebo for 48 h. For both muscles, subjects exercised at a fixed intensity until exhaustion on acetazolamide, with subsequent iso-time and -workload trials. Diaphragm exercise was performed using a threshold-loading device, while dorsiflexor exercise was isometric. Neuromuscular function was determined pre- and postexercise by potentiated transdiaphragmatic twitch pressure and dorsiflexor torque in response to stimulation of the phrenic and fibular nerve, respectively. Diaphragm contractility 3-10 min postexercise was impaired more for acetazolamide than methazolamide or placebo (82 ± 10, 87 ± 9, and 91 ± 8% of pre-exercise value; P < 0.05). Similarly, dorsiflexor fatigue was greater for acetazolamide than methazolamide (mean twitch torque of 61 ± 11 vs. 57 ± 13% of baseline, P < 0.05). In normoxia, methazolamide leads to less neuromuscular fatigue than acetazolamide, indicating a possible benefit for clinical use or in the prophylaxis of acute mountain sickness. NEW & NOTEWORTHY Acetazolamide, a carbonic anhydrase inhibitor, may worsen diaphragm and locomotor muscle fatigue after exercise; whereas, in animals, methazolamide does not impair diaphragm function. Compared with both methazolamide and the placebo, acetazolamide significantly compromised dorsiflexor function at rest and after exhaustive exercise. Similarly, diaphragm function was most compromised on acetazolamide followed by methazolamide and placebo. Methazolamide may be preferable over acetazolamide for clinical use and altitude illness prophylaxis to avoid skeletal muscle dysfunction.
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Affiliation(s)
- Paolo B Dominelli
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
| | - Chris J McNeil
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
| | - Tyler D Vermeulen
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
| | - Troy J R Stuckless
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
| | - Courtney V Brown
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
| | - Giulio S Dominelli
- Southern Medical Program, University of British Columbia, Kelowna, Canada
| | - Erik R Swenson
- Division of Pulmonary & Critical Care Medicine, VA Puget Sound Health Care System, University of Washington , Seattle, Washington
| | - Lucas J Teppema
- Department of Anesthesiology, Leiden University Medical Center , Leiden , The Netherlands
| | - Glen E Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
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Lizamore CA, Hamlin MJ. The Use of Simulated Altitude Techniques for Beneficial Cardiovascular Health Outcomes in Nonathletic, Sedentary, and Clinical Populations: A Literature Review. High Alt Med Biol 2017; 18:305-321. [PMID: 28846046 DOI: 10.1089/ham.2017.0050] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Lizamore, Catherine A., and Michael J. Hamlin. The use of simulated altitude techniques for beneficial cardiovascular health outcomes in nonathletic, sedentary, and clinical populations: A literature review. High Alt Med Biol 18:305-321, 2017. BACKGROUND The reportedly beneficial improvements in an athlete's physical performance following altitude training may have merit for individuals struggling to meet physical activity guidelines. AIM To review the effectiveness of simulated altitude training methodologies at improving cardiovascular health in sedentary and clinical cohorts. METHODS Articles were selected from Science Direct, PubMed, and Google Scholar databases using a combination of the following search terms anywhere in the article: "intermittent hypoxia," "intermittent hypoxic," "normobaric hypoxia," or "altitude," and a participant descriptor including the following: "sedentary," "untrained," or "inactive." RESULTS 1015 articles were returned, of which 26 studies were accepted (4 clinical cohorts, 22 studies used sedentary participants). Simulated altitude methodologies included prolonged hypoxic exposure (PHE: continuous hypoxic interval), intermittent hypoxic exposure (IHE: 5-10 minutes hypoxic:normoxic intervals), and intermittent hypoxic training (IHT: exercising in hypoxia). CONCLUSIONS In a clinical cohort, PHE for 3-4 hours at 2700-4200 m for 2-3 weeks may improve blood lipid profile, myocardial perfusion, and exercise capacity, while 3 weeks of IHE treatment may improve baroreflex sensitivity and heart rate variability. In the sedentary population, IHE was most likely to improve submaximal exercise tolerance, time to exhaustion, and heart rate variability. Hematological adaptations were unclear. Typically, a 4-week intervention of 1-hour-long PHE intervals 5 days a week, at a fraction of inspired oxygen (FIO2) of 0.15, was beneficial for pulmonary ventilation, submaximal exercise, and maximum oxygen consumption ([Formula: see text]O2max), but an FIO2 of 0.12 reduced hyperemic response and antioxidative capacity. While IHT may be beneficial for increased lipid metabolism in the short term, it is unlikely to confer any additional advantage over normoxic exercise over the long term. IHT may improve vascular health and autonomic balance.
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Affiliation(s)
- Catherine A Lizamore
- Department of Tourism, Sport and Society, Lincoln University , Lincoln, New Zealand
| | - Michael J Hamlin
- Department of Tourism, Sport and Society, Lincoln University , Lincoln, New Zealand
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Nieto Estrada VH, Molano Franco D, Medina RD, Gonzalez Garay AG, Martí‐Carvajal AJ, Arevalo‐Rodriguez I. Interventions for preventing high altitude illness: Part 1. Commonly-used classes of drugs. Cochrane Database Syst Rev 2017; 6:CD009761. [PMID: 28653390 PMCID: PMC6481751 DOI: 10.1002/14651858.cd009761.pub2] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND High altitude illness (HAI) is a term used to describe a group of cerebral and pulmonary syndromes that can occur during travel to elevations above 2500 metres (8202 feet). Acute hypoxia, acute mountain sickness (AMS), high altitude cerebral oedema (HACE) and high altitude pulmonary oedema (HAPE) are reported as potential medical problems associated with high altitude. In this review, the first in a series of three about preventive strategies for HAI, we assess the effectiveness of six of the most recommended classes of pharmacological interventions. OBJECTIVES To assess the clinical effectiveness and adverse events of commonly-used pharmacological interventions for preventing acute HAI. SEARCH METHODS We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OVID), Embase (OVID), LILACS and trial registries in January 2017. We adapted the MEDLINE strategy for searching the other databases. We used a combination of thesaurus-based and free-text terms to search. SELECTION CRITERIA We included randomized-controlled and cross-over trials conducted in any setting where commonly-used classes of drugs were used to prevent acute HAI. DATA COLLECTION AND ANALYSIS We used standard methodological procedures as expected by Cochrane. MAIN RESULTS We included 64 studies (78 references) and 4547 participants in this review, and classified 12 additional studies as ongoing. A further 12 studies await classification, as we were unable to obtain the full texts. Most of the studies were conducted in high altitude mountain areas, while the rest used low pressure (hypobaric) chambers to simulate altitude exposure. Twenty-four trials provided the intervention between three and five days prior to the ascent, and 23 trials, between one and two days beforehand. Most of the included studies reached a final altitude of between 4001 and 5000 metres above sea level. Risks of bias were unclear for several domains, and a considerable number of studies did not report adverse events of the evaluated interventions. We found 26 comparisons, 15 of them comparing commonly-used drugs versus placebo. We report results for the three most important comparisons: Acetazolamide versus placebo (28 parallel studies; 2345 participants)The risk of AMS was reduced with acetazolamide (risk ratio (RR) 0.47, 95% confidence interval (CI) 0.39 to 0.56; I2 = 0%; 16 studies; 2301 participants; moderate quality of evidence). No events of HAPE were reported and only one event of HACE (RR 0.32, 95% CI 0.01 to 7.48; 6 parallel studies; 1126 participants; moderate quality of evidence). Few studies reported side effects for this comparison, and they showed an increase in the risk of paraesthesia with the intake of acetazolamide (RR 5.53, 95% CI 2.81 to 10.88, I2 = 60%; 5 studies, 789 participants; low quality of evidence). Budenoside versus placebo (2 parallel studies; 132 participants)Data on budenoside showed a reduction in the incidence of AMS compared with placebo (RR 0.37, 95% CI 0.23 to 0.61; I2 = 0%; 2 studies, 132 participants; low quality of evidence). Studies included did not report events of HAPE or HACE, and they did not find side effects (low quality of evidence). Dexamethasone versus placebo (7 parallel studies; 205 participants)For dexamethasone, the data did not show benefits at any dosage (RR 0.60, 95% CI 0.36 to 1.00; I2 = 39%; 4 trials, 176 participants; low quality of evidence). Included studies did not report events of HAPE or HACE, and we rated the evidence about adverse events as of very low quality. AUTHORS' CONCLUSIONS Our assessment of the most commonly-used pharmacological interventions suggests that acetazolamide is an effective pharmacological agent to prevent acute HAI in dosages of 250 to 750 mg/day. This information is based on evidence of moderate quality. Acetazolamide is associated with an increased risk of paraesthesia, although there are few reports about other adverse events from the available evidence. The clinical benefits and harms of other pharmacological interventions such as ibuprofen, budenoside and dexamethasone are unclear. Large multicentre studies are needed for most of the pharmacological agents evaluated in this review, to evaluate their effectiveness and safety.
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Affiliation(s)
- Víctor H Nieto Estrada
- Fundacion Universitaria Sanitas, Colombia ClinicDepartment of Critical CareCarrera 19 # 8‐32BogotaBogotaColombia11001
| | - Daniel Molano Franco
- Fundacion Universitaria de Ciencias de la Salud, Hospital de San JoséDepartment of Critical CareCarrera 19 # 8‐32BogotaBogotaColombia11001
| | - Roger David Medina
- Fundación Universitaria de Ciencias de la SaludDivision of ResearchCarrera 19 # 8‐32Bogotá D.C.Colombia
| | - Alejandro G Gonzalez Garay
- National Institute of PediatricsMethodology Research UnitInsurgentes Sur 3700 ‐ CCol. Insurgentes Cuicuilco, CoyoacanMexico CityDistrito FederalMexico04530
| | | | - Ingrid Arevalo‐Rodriguez
- Universidad Tecnológica EquinoccialCochrane Ecuador. Centro de Investigación en Salud Pública y Epidemiología Clínica (CISPEC). Facultad de Ciencias de la Salud Eugenio EspejoAv. Mariscal Sucre s/n y Av. Mariana de JesúsQuitoEcuador
- Hospital Universitario Ramon y Cajal (IRYCIS)Clinical Biostatistics UnitMadridSpain
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Determinants of curvature constant (W') of the power duration relationship under normoxia and hypoxia: the effect of pre-exercise alkalosis. Eur J Appl Physiol 2017; 117:901-912. [PMID: 28280973 PMCID: PMC5388723 DOI: 10.1007/s00421-017-3574-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 02/15/2017] [Indexed: 01/08/2023]
Abstract
Purpose This study investigated the effect of induced alkalosis on the curvature constant (W’) of the power-duration relationship under normoxic and hypoxic conditions. Methods Eleven trained cyclists (mean ± SD) Age: 32 ± 7.2 years; body mass (bm): 77.0 ± 9.2 kg; VO2peak: 59.2 ± 6.8 ml·kg−1·min−1 completed seven laboratory visits which involved the determination of individual time to peak alkalosis following sodium bicarbonate (NaHCO3) ingestion, an environment specific ramp test (e.g. normoxia and hypoxia) and four x 3 min critical power (CP) tests under different experimental conditions. Participants completed four trials: alkalosis normoxia (ALN); placebo normoxia (PLN); alkalosis hypoxia (ALH); and placebo hypoxia (PLH). Pre-exercise administration of 0.3 g.kg−1 BM of NaHCO3 was used to induce alkalosis. Environmental conditions were set at either normobaric hypoxia (FiO2: 14.5%) or normoxia (FiO2: 20.93%). Results An increase in W’ was observed with pre-exercise alkalosis under both normoxic (PLN: 15.1 ± 6.2 kJ vs. ALN: 17.4 ± 5.1 kJ; P = 0.006) and hypoxic conditions (ALN: 15.2 ± 4.9 kJ vs. ALN: 17.9 ± 5.2 kJ; P < 0.001). Pre-exercise alkalosis resulted in a larger reduction in bicarbonate ion (HCO3−) concentrations during exercise in both environmental conditions (p < 0.001) and a greater blood lactate accumulation under hypoxia (P = 0.012). Conclusion Pre-exercise alkalosis substantially increased W’ and, therefore, may determine tolerance to exercise above CP under normoxic and hypoxic conditions. This may be due to NaHCO3 increasing HCO3− buffering capacity to delay exercise-induced acidosis, which may, therefore, enhance anaerobic energy contribution.
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Donegani E, Paal P, Küpper T, Hefti U, Basnyat B, Carceller A, Bouzat P, van der Spek R, Hillebrandt D. Drug Use and Misuse in the Mountains: A UIAA MedCom Consensus Guide for Medical Professionals. High Alt Med Biol 2016; 17:157-184. [PMID: 27583821 DOI: 10.1089/ham.2016.0080] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Donegani, Enrico, Peter Paal, Thomas Küpper, Urs Hefti, Buddha Basnyat, Anna Carceller, Pierre Bouzat, Rianne van der Spek, and David Hillebrandt. Drug use and misuse in the mountains: a UIAA MedCom consensus guide for medical professionals. High Alt Med Biol. 17:157-184, 2016.-Aims: The aim of this review is to inform mountaineers about drugs commonly used in mountains. For many years, drugs have been used to enhance performance in mountaineering. It is the UIAA (International Climbing and Mountaineering Federation-Union International des Associations d'Alpinisme) Medcom's duty to protect mountaineers from possible harm caused by uninformed drug use. The UIAA Medcom assessed relevant articles in scientific literature and peer-reviewed studies, trials, observational studies, and case series to provide information for physicians on drugs commonly used in the mountain environment. Recommendations were graded according to criteria set by the American College of Chest Physicians. RESULTS Prophylactic, therapeutic, and recreational uses of drugs relevant to mountaineering are presented with an assessment of their risks and benefits. CONCLUSIONS If using drugs not regulated by the World Anti-Doping Agency (WADA), individuals have to determine their own personal standards for enjoyment, challenge, acceptable risk, and ethics. No system of drug testing could ever, or should ever, be policed for recreational climbers. Sponsored climbers or those who climb for status need to carefully consider both the medical and ethical implications if using drugs to aid performance. In some countries (e.g., Switzerland and Germany), administrative systems for mountaineering or medication control dictate a specific stance, but for most recreational mountaineers, any rules would be unenforceable and have to be a personal decision, but should take into account the current best evidence for risk, benefit, and sporting ethics.
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Affiliation(s)
- Enrico Donegani
- 1 Department of Cardiovascular Surgery, Sabah Al-Ahmed Cardiac Center , Al-Amiri Hospital, Kuwait, State of Kuwait
| | - Peter Paal
- 2 Department of Anaesthesiology and Critical Care Medicine, Innsbruck University Hospital , Innsbruck, Austria .,3 Department of Perioperative Medicine, Barts Heart Centre, St. Bartholomew's Hospital, Barts Health NHS Trust, Queen Mary University of London, London, United Kingdom .,4 Perioperative Medicine, St. Bartholomew's Hospital , London, United Kingdom
| | - Thomas Küpper
- 5 Institute of Occupational and Social Medicine, RWTH Aachen University , Aachen, Germany
| | - Urs Hefti
- 6 Department of Orthopedic and Trauma Surgery, Swiss Sportclinic , Bern, Switzerland
| | - Buddha Basnyat
- 7 Oxford University Clinical Research Unit-Nepal , Nepal International Clinic, and Himalayan Rescue, Kathmandu, Nepal
| | - Anna Carceller
- 8 Sports Medicine School, Instituto de Medicina de Montaña y del Deporte (IMMED), Federació d'Entitats Excursionistes (FEEC), University of Barcelona , Barcelona, Spain
| | - Pierre Bouzat
- 9 Department of Anesthesiology and Critical Care, University Hospital, INSERM U1236, Neuroscience Institute, Alps University, Grenoble, France
| | - Rianne van der Spek
- 10 Department of Endocrinology and Metabolism, Academic Medical Center Amsterdam, University of Amsterdam , Amsterdam, The Netherlands
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Abstract
This paper describes the interactions between ventilation and acid-base balance under a variety of conditions including rest, exercise, altitude, pregnancy, and various muscle, respiratory, cardiac, and renal pathologies. We introduce the physicochemical approach to assessing acid-base status and demonstrate how this approach can be used to quantify the origins of acid-base disorders using examples from the literature. The relationships between chemoreceptor and metaboreceptor control of ventilation and acid-base balance summarized here for adults, youth, and in various pathological conditions. There is a dynamic interplay between disturbances in acid-base balance, that is, exercise, that affect ventilation as well as imposed or pathological disturbances of ventilation that affect acid-base balance. Interactions between ventilation and acid-base balance are highlighted for moderate- to high-intensity exercise, altitude, induced acidosis and alkalosis, pregnancy, obesity, and some pathological conditions. In many situations, complete acid-base data are lacking, indicating a need for further research aimed at elucidating mechanistic bases for relationships between alterations in acid-base state and the ventilatory responses.
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Affiliation(s)
- Michael I Lindinger
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada.
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Gonzales JU, Scheuermann BW. Effect of acetazolamide on respiratory muscle fatigue in humans. Respir Physiol Neurobiol 2013; 185:386-92. [DOI: 10.1016/j.resp.2012.08.023] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 08/22/2012] [Accepted: 08/28/2012] [Indexed: 10/27/2022]
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Abstract
Context: Sports and other activities at high altitude are popular, yet they pose the unique risk for high-altitude illness (HAI). Once those who have suffered from a HAI recover, they commonly desire or need to perform the same activity at altitude in the immediate or distant future. Evidence Acquisition: As based on key text references and peer-reviewed journal articles from a Medline search, this article reviews the pathophysiology and general treatment principles of HAI. Results: In addition to the type of HAI experienced and the current level of recovery, factors needing consideration in the return-to-play plan include physical activity requirements, flexibility of the activity schedule, and available medical equipment and facilities. Most important, adherence to prudent acclimatization protocols and gradual ascent recommendations (when above 3000 m, no more than 600-m net elevation gain per day, and 1 rest day every 1 to 2 ascent days) is powerful in its preventive value and thus strongly recommended. When these are not practical, prophylactic medications (acetazolamide, dexamethasone, salmeterol, nifedipine, or phosphodiesterase inhibitors, depending on the type of prior HAI) may be prescribed and can reduce the risk of illness. Athletes with HAI should be counseled that physical and mental performance may be adversely affected if activity at altitude continues before recovery is complete and that there is a risk of progression to a more serious HAI. Conclusion: With a thoughtful plan, most recurrent HAI in athletes can be prevented.
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Affiliation(s)
- Kevin Deweber
- Uniformed Services University of the Health Sciences, Bethesda, Maryland
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Kiwull-Schöne HF, Li Y, Kiwull PJ, Teppema LJ. Methazolamide does not impair respiratory work performance in anesthetized rabbits. Am J Physiol Regul Integr Comp Physiol 2009; 297:R648-54. [DOI: 10.1152/ajpregu.00134.2009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In human medicine, the carbonic anhydrase (CA) inhibitor acetazolamide is used to treat irregular breathing disorders. Previously, we demonstrated in the rabbit that this substance stabilized closed-loop gain properties of the respiratory control system, but concomitantly weakened respiratory muscles. Among others, the highly diffusible CA-inhibitor methazolamide differs from acetazolamide in that it fails to activate Ca2+-dependent potassium channels in skeletal muscles. Therefore, we aimed to find out, whether or not methazolamide may exert attenuating adverse effects on respiratory muscle performance as acetazolamide. In anesthetized spontaneously breathing rabbits ( n = 7), we measured simultaneously the CO2 responses of tidal phrenic nerve activity, tidal transpulmonary pressure changes, and tidal volume before and after intravenous application of methazolamide at two mean (± SE) cumulative doses of 3.5 ± 0.1 and 20.8 ± 0.4 mg/kg. Similar to acetazolamide, low- and high-dose methazolamide enhanced baseline ventilation by 52 ± 10% and 166 ± 30%, respectively ( P < 0.01) and lowered the base excess in a dose-dependent manner by up to 8.3 ± 0.9 mmol/l ( P < 0.001). The transmission of a CO2-induced rise in phrenic nerve activity into volume and/or pressure and, hence, respiratory work performance was 0.27 ± 0.05 ml·kg−1·kPa·unit−1 under control conditions, but remained unchanged upon low- or high-dose methazolamide, at 0.30 ± 0.06 and 0.28 ± 0.07 ml·kg−1·kPa·unit−1, respectively. We conclude that methazolamide does not cause respiratory muscle weakening at elevated levels of ventilatory drive. This substance (so far not used for medication of respiratory diseases) may thus exert stabilizing influences on breathing control without adverse effects on respiratory muscle function.
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Faoro V, Huez S, Giltaire S, Pavelescu A, van Osta A, Moraine JJ, Guenard H, Martinot JB, Naeije R. Effects of acetazolamide on aerobic exercise capacity and pulmonary hemodynamics at high altitudes. J Appl Physiol (1985) 2007; 103:1161-5. [PMID: 17615281 DOI: 10.1152/japplphysiol.00180.2007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Aerobic exercise capacity is decreased at altitude because of combined decreases in arterial oxygenation and in cardiac output. Hypoxic pulmonary vasoconstriction could limit cardiac output in hypoxia. We tested the hypothesis that acetazolamide could improve exercise capacity at altitude by an increased arterial oxygenation and an inhibition of hypoxic pulmonary vasoconstriction. Resting and exercise pulmonary artery pressure (Ppa) and flow (Q) (Doppler echocardiography) and exercise capacity (cardiopulmonary exercise test) were determined at sea level, 10 days after arrival on the Bolivian altiplano, at Huayna Potosi (4,700 m), and again after the intake of 250 mg acetazolamide vs. a placebo three times a day for 24 h. Acetazolamide and placebo were administered double-blind and in a random sequence. Altitude shifted Ppa/Q plots to higher pressures and decreased maximum O2 consumption (V̇o2max). Acetazolamide had no effect on Ppa/Q plots but increased arterial O2 saturation at rest from 84 ± 5 to 90 ± 3% ( P < 0.05) and at exercise from 79 ± 6 to 83 ± 4% ( P < 0.05), and O2 consumption at the anaerobic threshold (V-slope method) from 21 ± 5 to 25 ± 5 ml·min−1·kg−1 ( P < 0.01). However, acetazolamide did not affect V̇o2max (from 31 ± 6 to 29 ± 7 ml·kg−1·min−1), and the maximum respiratory exchange ratio decreased from 1.2 ± 0.06 to 1.05 ± 0.03 ( P < 0.001). We conclude that acetazolamide does not affect maximum exercise capacity or pulmonary hemodynamics at high altitudes. Associated changes in the respiratory exchange ratio may be due to altered CO2 production kinetics.
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Affiliation(s)
- Vitalie Faoro
- Laboratory of Physiology, Faculty of Medicine, Free University of Brussels, Brussels, Belgium
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Jonk AM, van den Berg IP, Olfert IM, Wray DW, Arai T, Hopkins SR, Wagner PD. Effect of acetazolamide on pulmonary and muscle gas exchange during normoxic and hypoxic exercise. J Physiol 2007; 579:909-21. [PMID: 17218362 PMCID: PMC2151360 DOI: 10.1113/jphysiol.2006.120949] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Acetazolamide (ACZ) is used to prevent acute mountain sickness at altitude. Because it could affect O2 transport in several different and potentially conflicting ways, we examined its effects on pulmonary and muscle gas exchange and acid-base status during cycle exercise at approximately 30, 50 and 90% VO2max in normoxia (F(IO2) = 0.2093) and acute hypoxia (F(IO2) = 0.125). In a double-blind, order-balanced, crossover design, six healthy, trained men (normoxic VO2max= 59 ml kg(-1) min(-1)) exercised at both F(IO2) values after ACZ (3 doses of 250 mg, 8 h apart) and placebo. One week later this protocol was repeated using the other drug (placebo or ACZ). We measured cardiac output (QT), leg blood flow (LBF), and muscle and pulmonary gas exchange, the latter using the multiple inert gas elimination technique. ACZ did not significantly affect VO2, QT, LBF or muscle gas exchange. As expected, ACZ led to lower arterial and venous blood [HCO3-], pH and lactate levels (P < 0.05), and increased ventilation (P < 0.05). In both normoxia and hypoxia, ACZ resulted in higher arterial P(O2) and saturation and a lower alveolar-arterial P(O2) difference (AaD(O2)) due to both less VA/Q mismatch and less diffusion limitation (P < 0.05). In summary, ACZ improved arterial oxygenation during exercise, due to both greater ventilation and more efficient pulmonary gas exchange. However, muscle gas exchange was unaffected.
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Affiliation(s)
- Amy M Jonk
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0623, USA
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