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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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Ryan BJ, Charkoudian N, Joyner MJ. Human performance augmentation: the importance of integrative physiological quantification. J Physiol 2023; 601:407-416. [PMID: 36518016 DOI: 10.1113/jp283975] [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: 10/13/2022] [Accepted: 12/09/2022] [Indexed: 12/16/2022] Open
Abstract
In recent years, there has been an explosion of new approaches (technological, methodological, pharmacological, etc.) designed to improve physical performance for athletes, the military and in other applications. The goal of the present discussion is to review and quantify several ways in which physiology can provide important insights about which tools may lead to improved performance (and may therefore be worth resource investment) and which tools are less likely to provide meaningful enhancement. To address these objectives, we review examples of technological solutions/approaches in terms of the magnitude of their potential (or actual) influences: transformational, moderate, ineffective or undetermined. As one example, if there were a technology which significantly increased arterial oxygen partial pressure by 10%, this would be relatively meaningless in healthy people resting at sea level, where it would have a minimal effect on arterial oxygen content. However, there might be specific situations where such an effect would be very helpful, including at high altitude or in some patient populations. We discuss the importance of quantitative evaluation of putative approaches to performance enhancement and highlight the important role of integrative physiologists in the development and critical appraisal of these approaches.
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Affiliation(s)
- Benjamin J Ryan
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA
| | - Nisha Charkoudian
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA
| | - Michael J Joyner
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, USA
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Hannemann J, Böger R. Dysregulation of the Nitric Oxide/Dimethylarginine Pathway in Hypoxic Pulmonary Vasoconstriction—Molecular Mechanisms and Clinical Significance. Front Med (Lausanne) 2022; 9:835481. [PMID: 35252268 PMCID: PMC8891573 DOI: 10.3389/fmed.2022.835481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 01/27/2022] [Indexed: 12/21/2022] Open
Abstract
The pulmonary circulation responds to hypoxia with vasoconstriction, a mechanism that helps to adapt to short-lived hypoxic episodes. When sustained, hypoxic pulmonary vasoconstriction (HPV) may become deleterious, causing right ventricular hypertrophy and failure, and contributing to morbidity and mortality in the late stages of several chronic pulmonary diseases. Nitric oxide (NO) is an important endothelial vasodilator. Its release is regulated, amongst other mechanisms, by the presence of endogenous inhibitors like asymmetric dimethylarginine (ADMA). Evidence has accumulated in recent years that elevated ADMA may be implicated in the pathogenesis of HPV and in its clinical sequelae, like pulmonary arterial hypertension (PAH). PAH is one phenotypic trait in experimental models with disrupted ADMA metabolism. In high altitude, elevation of ADMA occurs during long-term exposure to chronic or chronic intermittent hypobaric hypoxia; ADMA is significantly associated with high altitude pulmonary hypertension. High ADMA concentration was also reported in patients with chronic obstructive lung disease, obstructive sleep apnoea syndrome, and overlap syndrome, suggesting a pathophysiological role for ADMA-mediated impairment of endothelium-dependent, NO-mediated pulmonary vasodilation in these clinically relevant conditions. Improved understanding of the molecular (dys-)regulation of pathways controlling ADMA concentration may help to dissect the pathophysiology and find novel therapeutic options for these diseases.
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Affiliation(s)
- Juliane Hannemann
- Institute of Clinical Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Institute DECIPHER, German-Chilean Institute for Research on Pulmonary Hypoxia and its Health Sequelae, Hamburg, Germany
| | - Rainer Böger
- Institute of Clinical Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Institute DECIPHER, German-Chilean Institute for Research on Pulmonary Hypoxia and its Health Sequelae, Hamburg, Germany
- *Correspondence: Rainer Böger
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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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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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Sikri G, Kotwal A, Singh SP, Bhattachar S, Bhatia SS, Dutt M, Srinath N. Is it time to revise the acclimatization schedule at high altitude? Evidence from a field trial in Western Himalayas. Med J Armed Forces India 2019; 75:251-258. [PMID: 31388226 DOI: 10.1016/j.mjafi.2018.01.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 01/02/2018] [Indexed: 11/25/2022] Open
Abstract
Background In Western Himalayas, Indian Army soldiers take 11 days (6 days of acclimatization and 5 days of travel) on a sea-level to high altitude road (SH road) to reach a high altitude location (HAL) situated at an altitude of 11,500 feet from sea-level location (SLL) at an altitude of 1150 feet while following acclimatization schedule (AS). AS has an extra safety margin over the conventional 'mountaineering thumb rule' of not exceeding 500 m sleeping altitude above 3000 m altitude. We carried out this randomised field trial to study the feasibility of moving large number of troops rapidly from SLL to HAL on SH road in western Himalayas in 4 days under pharmaco-prophylaxis. Methods Based on the pharmaco-prophylaxis, at SLL 508 healthy lowland soldiers were divided into two groups: 'A' (n = 256) with Acetazolamide + Dexamethasone and 'B' (n = 252) with Acetazolamide + Placebo. They travelled rapidly by road to HAL in 4 days and prevalence of acute mountain sickness (AMS), high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE) during the ascent was measured. Results Prevalence of AMS was found to be 1.56% and 1.59% in group 'A' and group 'B' respectively during the ascent with no cases of HAPE and HACE. Conclusion At least on SH road, troops can be inducted rapidly to HAL from SLL in 4 days under pharmaco-prophylaxis with Acetazolamide with minimal occurrence of acute high altitude illnesses.
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Affiliation(s)
- Gaurav Sikri
- Professor and Head, Department of Physiology, Armed Forces Medical College, Pune, 411040, India
| | - Atul Kotwal
- Dy DGAFMS (Pensions), O/o DGAFMS, Ministry of Defence, 'M' Block, New Delhi, 110001, India
| | - S P Singh
- Professor, Department of Physiology, Armed Forces Medical College, Pune, 411040, India
| | - Srinivasa Bhattachar
- Assistant Professor, Department of Physiology, Armed Forces Medical College, Pune, 411040, India
| | - S S Bhatia
- Commandant, Military Hospital Mhow, C/o 56 APO, India
| | - Manohar Dutt
- Commanding Officer, 4002 Field Hospital, C/o 56 APO, India
| | - N Srinath
- Consultant (Surgery), O/o DGAFMS, Ministry of Defence, 'M' Block, New Delhi, 110001, India
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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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Boulet LM, Teppema LJ, Hackett HK, Dominelli PB, Cheyne WS, Dominelli GS, Irwin DC, Buehler PW, Baek JH, Swenson ER, Foster GE. Attenuation of human hypoxic pulmonary vasoconstriction by acetazolamide and methazolamide. J Appl Physiol (1985) 2018; 125:1795-1803. [PMID: 30236048 DOI: 10.1152/japplphysiol.00509.2018] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
RATIONALE Acetazolamide, a carbonic anhydrase inhibitor used for preventing altitude illness attenuates hypoxic pulmonary vasoconstriction (HPV) while improving oxygenation. Methazolamide, an analog of acetazolamide, is more lipophilic, has a longer half-life, and activates a major antioxidant transcription factor. However, its influence on the hypoxic pulmonary response in humans is unknown. OBJECTIVE To determine if a clinically relevant dosing of methazolamide improves oxygenation, attenuates HPV and augments plasma antioxidant capacity in men exposed to hypoxia when compared to an established dosing of acetazolamide known to suppress HPV. METHODS In this double-blind, placebo-controlled, cross-over trial, eleven participants were randomized to treatments with methazolamide (100mg b.i.d.) and acetazolamide (250mg t.i.d.) for two days prior to 60 minutes of hypoxia (FIO2≈0.12). MEASUREMENTS Pulmonary artery systolic pressure (PASP), alveolar ventilation (V̇A), blood gases and markers of redox status were measured. Pulmonary vascular sensitivity to hypoxia was determined by indexing PASP to alveolar PO2. RESULTS Acetazolamide caused greater metabolic acidosis compared with methazolamide, but the augmented V̇A and improved oxygenation with hypoxia were similar. The rise in PASP with hypoxia was lower with methazolamide (9.0 ± 0.9 mmHg) and acetazolamide (8.0 ± 0.7 mmHg) compared with placebo (14.1 ± 1.3 mmHg; P < 0.05). The pulmonary vascular sensitivity to hypoxia (ΔPASP/ΔPAO2) was reduced equally by both drugs. Only acetazolamide improved the non-enzymatic plasma antioxidant capacity. CONCLUSIONS Although acetazolamide only had plasma antioxidant properties, methazolamide led to similar improvements in oxygenation and reduction in HPV at a dose causing less metabolic acidosis than acetazolamide in humans.
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Affiliation(s)
| | - Luc J Teppema
- Anesthesiology, Leiden University Medical Center, Netherlands
| | - Heather K Hackett
- School of Health and Exercise Sciences, University of British Columbia
| | | | | | | | - David C Irwin
- Division of Cardiovascular Pulmonary Research, University of Colorado Denver Health Sciences Center, United States
| | | | | | | | - Glen Edward Foster
- School of Health and Exercise Science, University of British Columbia, Canada
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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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10
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Bradwell AR, Ashdown K, Rue C, Delamere J, Thomas OD, Lucas SJE, Wright AD, Harris SJ, Myers SD. Acetazolamide reduces exercise capacity following a 5-day ascent to 4559 m in a randomised study. BMJ Open Sport Exerc Med 2018; 4:e000302. [PMID: 29387446 PMCID: PMC5783038 DOI: 10.1136/bmjsem-2017-000302] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/14/2017] [Indexed: 11/08/2022] Open
Abstract
Objective To assess whether acetazolamide (Az), used prophylactically for acute mountain sickness (AMS), alters exercise capacity at high altitude. Methods Az (500 mg daily) or placebo was administered to 20 healthy adults (aged 36±20 years, range 21–77), who were paired for age, sex, AMS susceptibility and weight, in a double-blind, randomised manner. Participants ascended over 5 days to 4559 m, then exercised to exhaustion on a bicycle ergometer, while recording breath-by-breath gas measurements. Comparisons between groups and matched pairs were done via Mann-Whitney U and Pearson’s χ2 tests, respectively. Results Comparing paired individuals at altitude, those on Az had greater reductions in maximum power output (Pmax) as a percentage of sea-level values (65±14.1 vs 76.6±7.4 (placebo); P=0.007), lower VO2max (20.7±5.2 vs 24.6±5.1 mL/kg/min; P<0.01), smaller changes from rest to Pmax for VO2 (9.8±6.2 vs 13.8±4.9 mL/kg/min; P=0.04) and lower heart rate at Pmax (154±25 vs 167±16, P<0.01) compared with their placebo-treated partners. Correlational analysis (Pearson’s) indicated that with increasing age Pmax (r=−0.83: P<0.005) and heart rate at Pmax (r=−0.71, P=0.01) reduced more in those taking Az. Conclusion Maximum exercise performance at altitude was reduced more in subjects taking Az compared with placebo, particularly in older individuals. The age-related effect may reflect higher tissue concentrations of Az due to reduced renal excretion. Future studies should explore the effectiveness of smaller Az doses (eg, 250 mg daily or less) in older individuals to optimise the altitude–Az–exercise relationships.
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Affiliation(s)
- Arthur R Bradwell
- Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Kimberley Ashdown
- Department of Sport and Exercise Sciences, University of Chichester, Chichester, UK
| | - Carla Rue
- Department of Sport and Exercise Sciences, University of Chichester, Chichester, UK
| | - John Delamere
- Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Owen D Thomas
- Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Samuel J E Lucas
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - Alex D Wright
- Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | | | - Stephen D Myers
- Department of Sport and Exercise Sciences, University of Chichester, Chichester, UK
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Role of acetazolamide and telmisartan/nifedipine-GITS combination in antagonizing the blood pressure rise induced by high altitude exposure. Int J Cardiol 2016; 225:324-326. [DOI: 10.1016/j.ijcard.2016.09.094] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 09/24/2016] [Indexed: 11/23/2022]
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12
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Luks AM, Grissom C, Freer L, Hackett P. Medication Use Among Mount Everest Climbers: Practice and Attitudes. High Alt Med Biol 2016; 17:315-322. [PMID: 27763796 DOI: 10.1089/ham.2016.0077] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Luks, Andrew M., Colin Grissom, Luanne Freer, and Peter Hackett. Medication use among mount Everest climbers: practice and attitudes. High Alt Med Biol. 17:315-322, 2016.-The lay public, media, and medical experts have expressed concern about the ethics of climbers using medications to improve performance and increase the odds of summit success while climbing at high altitude, but the true incidence of this practice remains unclear. We conducted an anonymous survey of climbers who have attempted to climb Mt. Everest to gather information about medication use and attitudes toward medication and supplemental oxygen use while climbing the mountain. One hundred eighty-seven individuals completed the survey, providing information about medication and oxygen use for 262 expeditions to Mt. Everest between 1963 and 2015, the majority of which occurred after the year 2000. The majority of respondents were male (82%) and from English-speaking countries (75%). Medications were used on 43% of climbs, with acetazolamide being the most commonly used medication. Reported use of dexamethasone, nifedipine, sildenafil, or tadalafil was uncommon as was use of multiple medications at the same time. The majority of respondents indicated that it was acceptable for climbers to use medications and supplemental oxygen to prevent altitude illness while climbing Mt. Everest. Opinions were more mixed regarding whether summiting without the use of medications or oxygen carried the same value as reaching the summit using those interventions. Our data suggest that less than one-half of Mt. Everest climbers use medications during their expedition, with the primary medication used being acetazolamide, for prevention of altitude illness. Given the limitations of the study design and preliminary nature of these data, further research is warranted to further clarify these issues.
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Affiliation(s)
- Andrew M Luks
- 1 Division of Pulmonary and Critical Care Medicine, University of Washington , Seattle, Washington
| | - Colin Grissom
- 2 Division of Pulmonary and Critical Care Medicine, Intermountain Medical Center and the University of Utah , Salt Lake City, Utah
| | - Luanne Freer
- 3 Yellowstone National Park , Bozeman, Montana.,4 Himalayan Rescue Association Everest Base Camp Medical Clinic , Nepal
| | - Peter Hackett
- 5 Department of Emergency Medicine, University of Colorado , Denver, Colorado.,6 Institute for Altitude Medicine , Telluride, Colorado
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Harrison MF, Anderson PJ, Johnson JB, Richert M, Miller AD, Johnson BD. Acute Mountain Sickness Symptom Severity at the South Pole: The Influence of Self-Selected Prophylaxis with Acetazolamide. PLoS One 2016; 11:e0148206. [PMID: 26848757 PMCID: PMC4744068 DOI: 10.1371/journal.pone.0148206] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 01/14/2016] [Indexed: 01/23/2023] Open
Abstract
INTRODUCTION Acetazolamide, a carbonic anhydrase inhibitor, remains the only FDA approved pharmaceutical prophylaxis for acute mountain sickness (AMS) though its effectiveness after rapid transport in real world conditions is less clear. METHODS Over 2 years, 248 healthy adults traveled by airplane from sea level (SL) to the South Pole (ALT, ~3200m) and 226 participants provided Lake Louise Symptom Scores (LLSS) on a daily basis for 1 week; vital signs, blood samples, and urine samples were collected at SL and at ALT. Acetazolamide was available to any participant desiring prophylaxis. Comparisons were made between the acetazolamide with AMS (ACZ/AMS) (n = 42), acetazolamide without AMS (ACZ/No AMS)(n = 49), no acetazolamide with AMS (No ACZ/AMS) (n = 56), and the no acetazolamide without AMS (No ACZ/No AMS) (n = 79) groups. Statistical analysis included Chi-squared and one-way ANOVA with Bonferroni post-hoc tests. Significance was p≤0.05. RESULTS No significant differences were found for between-group characteristics or incidence of AMS between ACZ and No ACZ groups. ACZ/AMS reported greater LLSS, BMI, and red cell distribution width. ACZ/No AMS had the highest oxygen saturation (O2Sat) at ALT. No significant differences were found in serum electrolyte concentrations or PFT results. DISCUSSION Acetazolamide during rapid ascent provided no apparent protection from AMS based on LLSS. However, it is unclear if this lack of effect was directly associated with the drug or if perhaps there was some selection bias with individuals taking ACZ more likely to have symptoms or if there may have been more of perceptual phenomenon related to a constellation of side effects.
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Affiliation(s)
- Michael F. Harrison
- Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, United States of America
- Department of Emergency Medicine, Henry Ford Hospital, Detroit, Michigan, United States of America
| | - Paul J. Anderson
- Division of Preventive, Occupational, and Aerospace Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Jacob B. Johnson
- Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Maile Richert
- Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Andrew D. Miller
- Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Bruce D. Johnson
- Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, United States of America
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Wauters A, Vicenzi M, De Becker B, Riga JP, Esmaeilzadeh F, Faoro V, Vachiéry JL, van de Borne P, Argacha JF. At high cardiac output, diesel exhaust exposure increases pulmonary vascular resistance and decreases distensibility of pulmonary resistive vessels. Am J Physiol Heart Circ Physiol 2015; 309:H2137-44. [PMID: 26497960 DOI: 10.1152/ajpheart.00149.2015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 10/19/2015] [Indexed: 12/19/2022]
Abstract
Air pollution has recently been associated with the development of acute decompensated heart failure, but the underlying biological mechanisms remain unclear. A pulmonary vasoconstrictor effect of air pollution, combined with its systemic effects, may precipitate decompensated heart failure. The aim of the present study was to investigate the effects of acute exposure to diesel exhaust (DE) on pulmonary vascular resistance (PVR) under resting and stress conditions but also to determine whether air pollution may potentiate acquired pulmonary hypertension. Eighteen healthy male volunteers were exposed to ambient air (AA) or dilute DE with a particulate matter of <2.5 μm concentration of 300 μg/m(3) for 2 h in a randomized, crossover study design. The effects of DE on PVR, on the coefficient of distensibilty of pulmonary vessels (α), and on right and left ventricular function were evaluated at rest (n = 18), during dobutamine stress echocardiography (n = 10), and during exercise stress echocardiography performed in hypoxia (n = 8). Serum endothelin-1 and fractional exhaled nitric oxide were also measured. At rest, exposure to DE did not affect PVR. During dobutamine stress, the slope of the mean pulmonary artery pressure-cardiac output relationship increased from 2.8 ± 0.5 mmHg · min · l (-1) in AA to 3.9 ± 0.5 mmHg · min · l (-1) in DE (P < 0.05) and the α coefficient decreased from 0.96 ± 0.15 to 0.64 ± 0.12%/mmHg (P < 0.01). DE did not further enhance the hypoxia-related upper shift of the mean pulmonary artery pressure-cardiac output relationship. Exposure to DE did not affect serum endothelin-1 concentration or fractional exhaled nitric oxide. In conclusion, acute exposure to DE increased pulmonary vasomotor tone by decreasing the distensibility of pulmonary resistive vessels at high cardiac output.
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Affiliation(s)
- Aurélien Wauters
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium;
| | - Marco Vicenzi
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium; Laboratory of Physiology and Physiopathology, Université Libre de Bruxellesm, Brussels, Belgium; and
| | - Benjamin De Becker
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Jean-Philippe Riga
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Fatemeh Esmaeilzadeh
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Vitalie Faoro
- Laboratory of Physiology and Physiopathology, Université Libre de Bruxellesm, Brussels, Belgium; and
| | - Jean-Luc Vachiéry
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Philippe van de Borne
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Jean-François Argacha
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium; Department of Cardiology, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel, Brussels, Belgium
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Cerebral volumetric changes induced by prolonged hypoxic exposure and whole-body exercise. J Cereb Blood Flow Metab 2014; 34:1802-9. [PMID: 25160673 PMCID: PMC4269757 DOI: 10.1038/jcbfm.2014.148] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 07/17/2014] [Accepted: 07/28/2014] [Indexed: 11/08/2022]
Abstract
The present study assessed the isolated and synergetic effects of hypoxic exposure and prolonged exercise on cerebral volume and subedema and symptoms of acute mountain sickness (AMS). Twelve healthy males performed three semirandomized blinded 11-hour sessions with (1) an inspiratory oxygen fraction (FiO2) of 12% and 4-hour cycling, (2) FiO2=21% and 4-hour cycling, and (3) FiO2=8.5% to 12% at rest (matching arterial oxygen saturation measured during the first hypoxic session). Volumetric, apparent diffusion coefficient (ADC), and arterial spin labelling 3T magnetic resonance imaging sequences were performed after 30 minutes and 10 hours in each session. Thirty minutes of hypoxia at rest induced a significant increase in white-matter volume (+0.8±1.0% compared with normoxia) that was exacerbated after 10 hours of hypoxia at rest (+1.5±1.1%) or with cycling (+1.6±1.1%). Total brain parenchyma volume increased significantly after 10 hours of hypoxia with cycling only (+1.3±1.1%). Apparent diffusion coefficient was significantly reduced after 10 hours of hypoxia at rest or with cycling. No significant change in cerebral blood flow was observed. These results demonstrate changes in white-matter volume as early as after 30 minutes of hypoxia that worsen after 10 hours, probably due to cytotoxic edema. Exercise accentuates the effect of hypoxia by increasing total brain volume. These changes do not however correlate with AMS symptoms.
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Bradwell AR, Myers SD, Beazley M, Ashdown K, Harris NG, Bradwell SB, Goodhart J, Imray CH, Wimalasena Y, Edsell ME, Pattinson KT, Wright AD, Harris SJ. Exercise Limitation of Acetazolamide at Altitude (3459 m). Wilderness Environ Med 2014; 25:272-7. [DOI: 10.1016/j.wem.2014.04.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 03/26/2014] [Accepted: 04/04/2014] [Indexed: 10/25/2022]
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Ke T, Wang J, Swenson ER, Zhang X, Hu Y, Chen Y, Liu M, Zhang W, Zhao F, Shen X, Yang Q, Chen J, Luo W. Effect of acetazolamide and gingko biloba on the human pulmonary vascular response to an acute altitude ascent. High Alt Med Biol 2014; 14:162-7. [PMID: 23795737 DOI: 10.1089/ham.2012.1099] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Acetazolamide and gingko biloba are the two most investigated drugs for the prevention of acute mountain sickness (AMS). Evidence suggests that they may also reduce pulmonary artery systolic pressure (PASP). To investigate whether these two drugs for AMS prevention also reduce PASP with rapid airlift ascent to high altitude, a randomized controlled trial was conducted on 28 healthy young men with acetazolamide (125 mg bid), gingko biloba (120 mg bid), or placebo for 3 days prior to airlift ascent (397 m) and for the first 3 days at high altitude (3658 m). PASP, AMS, arterial oxygen saturation (Sao2), mean arterial pressure (MAP), heart rate (HR), forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and peak expiratory flow (PEF) were assessed both at 397 m and 3658 m. HR, PEF, and PASP increased with altitude exposure (p<0.05), and SaO2 decreased (p<0.05). PASP with acetazolamide (mean at 3658 m, 26.2 mm Hg; incremental change, 4.7 mm Hg, 95% CI., 2.6-6.9 mm Hg) was lower than that with ginkgo biloba (mean at 3658 m, 33.7 mm Hg, p=0.001; incremental change, 13.1 mm Hg, 95%CI., 9.6-16.5 mm Hg, p=0.002), and with placebo (mean at 3658 m, 34.7 mm Hg, p<0.001; 14.4 mm Hg, 95% CI., 8.8-20.0 mm Hg, p=0.001). The data show that a low prophylactic dosage of acetazolamide, but not gingko biloba, mitigates the early increase of PASP in a quick ascent profile.
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Affiliation(s)
- Tao Ke
- Department of Occupational and Environmental Health, the Ministry of Education Key Lab of Hazard Assessment and Control in Special Operational Environment, School of Public Health, Fourth Military Medical University, Xi'an, China
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Abstract
Carbonic anhydrase (CA) inhibitors, particularly acetazolamide, have been used at high altitude for decades to prevent or reduce acute mountain sickness (AMS), a syndrome of symptomatic intolerance to altitude characterized by headache, nausea, fatigue, anorexia and poor sleep. Principally CA inhibitors act to further augment ventilation over and above that stimulated by the hypoxia of high altitude by virtue of renal and endothelial cell CA inhibition which oppose the hypocapnic alkalosis resulting from the hypoxic ventilatory response (HVR), which acts to limit the full expression of the HVR. The result is even greater arterial oxygenation than that driven by hypoxia alone and greater altitude tolerance. The severity of several additional diseases of high attitude may also be reduced by acetazolamide, including high altitude cerebral edema (HACE), high altitude pulmonary edema (HAPE) and chronic mountain sickness (CMS), both by its CA-inhibiting action as described above, but also by more recently discovered non-CA inhibiting actions, that seem almost unique to this prototypical CA inhibitor and are of most relevance to HAPE. This chapter will relate the history of CA inhibitor use at high altitude, discuss what tissues and organs containing carbonic anhydrase play a role in adaptation and maladaptation to high altitude, explore the role of the enzyme and its inhibition at those sites for the prevention and/or treatment of the four major forms of illness at high altitude.
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Affiliation(s)
- Erik R Swenson
- VA Puget Sound Health Care System and Department of Medicine, University of Washington, Seattle, WA, USA,
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Abstract
High-altitude pulmonary edema (HAPE), a not uncommon form of acute altitude illness, can occur within days of ascent above 2500 to 3000 m. Although life-threatening, it is avoidable by slow ascent to permit acclimatization or with drug prophylaxis. The critical pathophysiology is an excessive rise in pulmonary vascular resistance or hypoxic pulmonary vasoconstriction (HPV) leading to increased microvascular pressures. The resultant hydrostatic stress causes dynamic changes in the permeability of the alveolar capillary barrier and mechanical injurious damage leading to leakage of large proteins and erythrocytes into the alveolar space in the absence of inflammation. Bronchoalveolar lavage and hemodynamic pressure measurements in humans confirm that elevated capillary pressure induces a high-permeability noninflammatory lung edema. Reduced nitric oxide availability and increased endothelin in hypoxia are the major determinants of excessive HPV in HAPE-susceptible individuals. Other hypoxia-dependent differences in ventilatory control, sympathetic nervous system activation, endothelial function, and alveolar epithelial active fluid reabsorption likely contribute additionally to HAPE susceptibility. Recent studies strongly suggest nonuniform regional hypoxic arteriolar vasoconstriction as an explanation for how HPV occurring predominantly at the arteriolar level causes leakage. In areas of high blood flow due to lesser HPV, edema develops due to pressures that exceed the dynamic and structural capacity of the alveolar capillary barrier to maintain normal fluid balance. This article will review the pathophysiology of the vasculature, alveolar epithelium, innervation, immune response, and genetics of the lung at high altitude, as well as therapeutic and prophylactic strategies to reduce the morbidity and mortality of HAPE.
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Affiliation(s)
- Erik R Swenson
- VA Puget Sound Health Care System, Department of Medicine, University of Washington, Seattle, Washington, USA.
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Naeije R, Vanderpool R. Pulmonary Hypertension and Chronic Mountain Sickness. High Alt Med Biol 2013; 14:117-25. [DOI: 10.1089/ham.2012.1124] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Affiliation(s)
- Robert Naeije
- Department of Pathophysiology, Faculty of Medicine, Free University of Brussels, Brussels, Belgium
| | - Rebecca Vanderpool
- Department of Pathophysiology, Faculty of Medicine, Free University of Brussels, Brussels, Belgium
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MacCormick IJC, Somner J, Morris DS, MacGillivray TJ, Bourne RRA, Huang SS, MacCormick A, Aspinall PA, Baillie JK, Thompson AAR, Dhillon B. Retinal vessel tortuosity in response to hypobaric hypoxia. High Alt Med Biol 2013; 13:263-8. [PMID: 23270443 DOI: 10.1089/ham.2011.1097] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
PURPOSE Retinal vascular tortuosity is associated with retinopathy of differing etiologies, including hypertension, diabetes, and hypoxia. However, detailed understanding of the underlying pathophysiology is lacking. The aim of this study was to map changes in tortuosity associated with hypoxia at high altitude, and to determine the influence of sildenafil and an antioxidant preparation on altitude-induced tortuosity. METHODS We measured the tortuosity of retinal vessels using a semi-automated method in 35 young, healthy subjects exposed to hypobaric hypoxia for 7 days at 5200 m, and compared the measurements to those from the same vessels at sea level. These subjects simultaneously took part in a randomized double-blind placebo-controlled trial of sildenafil and antioxidant. Comparison of tortuosity between these subgroups was performed. RESULTS High altitude was associated with the development of retinal tortuosity in individual vessels. A nonsignificant trend suggests this is limited by prophylaxis with sildenafil or antioxidant. CONCLUSIONS Retinal vessel tortuosity increases rapidly at high altitude. We suggest that retinal vessel tortuosity at altitude may result from increased sheer stress causing elongation of vessel segments and that this might be limited by agents that act to preserve nitric oxide dependent vasodilation. TRIAL REGISTRATION NUMBERS NCT00664001, NCT00627965.
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Affiliation(s)
- Ian J C MacCormick
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi.
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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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Performance-Enhancing Drugs—Commentaries. Wilderness Environ Med 2012; 23:207-11. [DOI: 10.1016/j.wem.2012.07.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 07/05/2012] [Indexed: 11/22/2022]
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Bates MGD, Thompson AAR, Baillie JK, Sutherland AI, Irving JB, Hirani N, Webb DJ. Sildenafil citrate for the prevention of high altitude hypoxic pulmonary hypertension: double blind, randomized, placebo-controlled trial. High Alt Med Biol 2012; 12:207-14. [PMID: 21962063 DOI: 10.1089/ham.2011.0007] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Exaggerated hypoxic pulmonary vasoconstriction is a key factor in the development of high altitude pulmonary edema (HAPE). Due to its effectiveness as a pulmonary vasodilator, sildenafil has been proposed as a prophylactic agent against HAPE. By conducting a parallel-group double blind, randomized, placebo-controlled trial, we investigated the effect of chronic sildenafil administration on pulmonary artery systolic pressure (PASP) and symptoms of acute mountain sickness (AMS) during acclimatization to high altitude. Sixty-two healthy lowland volunteers (36 male; median age 21 years, range 18 to 31) on the Apex 2 research expedition were flown to La Paz, Bolivia (3650 m), and after 4-5 days acclimatization ascended over 90 min to 5200 m. The treatment group (n=20) received 50 mg sildenafil citrate three times daily. PASP was recorded by echocardiography at sea level and within 6 h, 3 days, and 1 week at 5200 m. AMS was assessed daily using the Lake Louise Consensus symptom score. On intention-to-treat analysis, there was no significant difference in PASP at 5200 m between sildenafil and placebo groups. Median AMS score on Day 2 at 5200 m was significantly higher in the sildenafil group (placebo 4.0, sildenafil 6.5; p=0.004) but there was no difference in prevalence of AMS between groups. Sildenafil administration did not affect PASP in healthy lowland subjects at 5200 m but AMS was significantly more severe on Day 2 at 5200 m with sildenafil. Our data do not support routine prophylactic use of sildenafil to reduce PASP at high altitude in healthy subjects with no history of HAPE. TRIALS REGISTRATION NUMBER: NCT00627965.
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Affiliation(s)
- Matthew G D Bates
- Mitochondrial Research Group, Medical School, Institute for Ageing and Health, Newcastle University, Newcastle upon Tyne, United Kingdom.
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Abstract
The pulmonary circulation is a high-flow and low-pressure circuit, with an average resistance of 1 mmHg/min/L in young adults, increasing to 2.5 mmHg/min/L over four to six decades of life. Pulmonary vascular mechanics at exercise are best described by distensible models. Exercise does not appear to affect the time constant of the pulmonary circulation or the longitudinal distribution of resistances. Very high flows are associated with high capillary pressures, up to a 20 to 25 mmHg threshold associated with interstitial lung edema and altered ventilation/perfusion relationships. Pulmonary artery pressures of 40 to 50 mmHg, which can be achieved at maximal exercise, may correspond to the extreme of tolerable right ventricular afterload. Distension of capillaries that decrease resistance may be of adaptative value during exercise, but this is limited by hypoxemia from altered diffusion/perfusion relationships. Exercise in hypoxia is associated with higher pulmonary vascular pressures and lower maximal cardiac output, with increased likelihood of right ventricular function limitation and altered gas exchange by interstitial lung edema. Pharmacological interventions aimed at the reduction of pulmonary vascular tone have little effect on pulmonary vascular pressure-flow relationships in normoxia, but may decrease resistance in hypoxia, unloading the right ventricle and thereby improving exercise capacity. Exercise in patients with pulmonary hypertension is associated with sharp increases in pulmonary artery pressure and a right ventricular limitation of aerobic capacity. Exercise stress testing to determine multipoint pulmonary vascular pressures-flow relationships may uncover early stage pulmonary vascular disease.
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Affiliation(s)
- R NAEIJE
- Department of Physiology, Erasme Campus of the Free University of Brussels, CP 604, 808, Lennik road, B-1070 Brussels, BELGIUM, Tel +32 2 5553322, Fax +32 2 5554124
| | - N CHESLER
- University of Wisconsin at Madison, 2146 Engineering Centers Building, 1550 Engineering drive, Madison, Wisconsin 53706-1609, USA, Tel +1 608 265 8920, Fax +1 608 265 9239
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Latshang TD, Turk AJ, Hess T, Schoch OD, Bosch MM, Barthelmes D, Merz TM, Hefti U, Hefti JP, Maggiorini M, Bloch KE. Acclimatization improves submaximal exercise economy at 5533 m. Scand J Med Sci Sports 2011; 23:458-67. [PMID: 22093058 DOI: 10.1111/j.1600-0838.2011.01403.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/29/2011] [Indexed: 11/28/2022]
Abstract
We tested whether the better subjective exercise tolerance perceived by mountaineers after altitude acclimatization relates to enhanced exercise economy. Thirty-two mountaineers performed progressive bicycle exercise to exhaustion at 490 m and twice at 5533 m (days 6-7 and day 11), respectively, during an expedition to Mt. Muztagh Ata. Maximal work rate (W(max)) decreased from mean ± SD 356 ± 73 watts at 490 m to 191 ± 49 watts and 193 ± 45 watts at 5533 m, days 6-7 and day 11, respectively; corresponding maximal oxygen uptakes (VO2max ) were 50.7 ± 9.5, 26.3 ± 5.6, 24.7 ± 7.0 mL/min/kg (P = 0.0001 5533 m vs 490 m). On days 6-7 (5533 m), VO(2) at 75% W(max) (152 ± 37 watts) was 1.75 ± 0.45 L/min, oxygen saturation 68 ± 8%. On day 11 (5533 m), at the same submaximal work rate, VO(2) was lower (1.61 ± 0.47 L/min, P < 0.027) indicating improved net efficiency; oxygen saturation was higher (74 ± 7%, P < 0.0004) but ratios of VO(2) to work rate increments remained unchanged. On day 11, mountaineers climbed faster from 4497 m to 5533 m than on days 5-6 but perceived less effort (visual analog scale 50 ± 15 vs 57 ± 20, P = 0.006) and reduced symptoms of acute mountain sickness. We conclude that the better performance and subjective exercise tolerance after acclimatization were related to regression of acute mountain sickness and improved submaximal exercise economy because of lower metabolic demands for non-external work-performing functions.
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Affiliation(s)
- T D Latshang
- Pulmonary Division, University Hospital Zurich, Zurich, Switzerland
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Faoro V, Boldingh S, Moreels M, Martinez S, Lamotte M, Unger P, Brimioulle S, Huez S, Naeije R. Bosentan Decreases Pulmonary Vascular Resistance and Improves Exercise Capacity in Acute Hypoxia. Chest 2009; 135:1215-1222. [DOI: 10.1378/chest.08-2222] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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Lalande S, Snyder EM, Olson TP, Hulsebus ML, Orban M, Somers VK, Johnson BD, Frantz RP. The effects of sildenafil and acetazolamide on breathing efficiency and ventilatory control during hypoxic exercise. Eur J Appl Physiol 2009; 106:509-15. [PMID: 19337745 DOI: 10.1007/s00421-009-1042-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/16/2009] [Indexed: 11/30/2022]
Abstract
The reduced arterial oxygen tension at high altitude impairs the ability to work. Acetazolamide improves arterial oxygen saturation (SaO(2)) by increasing ventilation but is associated with an increased work and cost of breathing. Depending on the settings, sildenafil can also increases SaO(2) possibly through a reduction in pulmonary hypertension and interstitial edema, which could improve ventilation-perfusion matching. The objective of this study is to determine the effects of acetazolamide and sildenafil on ventilatory control and breathing efficiency (V(E)/VCO(2)) during submaximal steady-state hypoxic exercise in healthy individuals. Following 18 h of hypoxic exposure in an altitude tent at an oxygen concentration of 12.5% (simulated altitude of 4,300 m), 15 participants performed 10 min of hypoxic exercise on a stationary bicycle at 40% of their sea level peak oxygen uptake (VO(2)) while randomly receiving sildenafil 40 mg (SIL), acetazolamide 125 mg (ACZ) or a placebo (PLA). There was no difference in VO(2) during exercise between conditions while SaO(2) was greater with acetazolamide compared to both placebo and sildenafil. Acetazolamide increased ventilation (PLA 49.0 +/- 3.2, SIL 47.7 +/- 3.1, ACZ 52.1 +/- 3.0 l/min) and reduced end-tidal CO(2) (P(ET)CO(2)) (PLA 32.1 +/- 0.8, SIL 32.8 +/- 0.9, ACZ 29.2 +/- 0.7 mmHg) compared to placebo and sildenafil. Breathing was less efficient with acetazolamide (increased V(E)/VCO(2)) in comparison to placebo and sildenafil (PLA 41.5 +/- 1.0, SIL 40.4 +/- 1.3, ACZ 45.4 +/- 1.0) while sildenafil did not change V(E)/VCO(2) during hypoxic exercise. In conclusion, acetazolamide increased ventilation and reduced breathing efficiency while sildenafil did not affect breathing efficiency despite a trend toward a blunted ventilatory response, possibly due to a reduction in pulmonary hypertension and/or ventilatory drive, during submaximal hypoxic exercise in healthy individuals.
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Affiliation(s)
- Sophie Lalande
- Division of Cardiovascular Diseases, Mayo Clinic, College of Medicine, Rochester, MN 55905, USA.
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Luks AM. Do we have a "best practice" for treating high altitude pulmonary edema? High Alt Med Biol 2008; 9:111-4. [PMID: 18578641 DOI: 10.1089/ham.2008.1017] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
High-altitude pulmonary edema (HAPE) is a rare, but potentially fatal, non-cardiogenic pulmonary edema that affects unacclimatized lowlanders ascending to altitudes above 2500 m. A review of the literature on the disease suggests that a wide range of strategies is employed for treatment purposes. This situation raises questions as to whether a "best practice" exists for treating HAPE and whether clinicians are using greater measures than necessary to ensure good outcomes. This review considers these issues in greater detail, examining the current state of research and clinical practice in HAPE treatment, addressing important questions raised by documented treatment practices, such as the utility of beta agonists, acetazolamide and diuretics and, finally, proposing reasonable, parsimonious treatment approaches that reflect the setting in which the patient is being treated.
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Affiliation(s)
- Andrew M Luks
- Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington 91895-6522, USA.
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Basnyat B, Hargrove J, Holck PS, Srivastav S, Alekh K, Ghimire LV, Pandey K, Griffiths A, Shankar R, Kaul K, Paudyal A, Stasiuk D, Basnyat R, Davis C, Southard A, Robinson C, Shandley T, Johnson DW, Zafren K, Williams S, Weiss EA, Farrar JJ, Swenson ER. Acetazolamide Fails to Decrease Pulmonary Artery Pressure at High Altitude in Partially Acclimatized Humans. High Alt Med Biol 2008; 9:209-16. [DOI: 10.1089/ham.2007.1073] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Buddha Basnyat
- Nepal International Clinic, Kathmandu, Nepal
- Himalayan Rescue Association, Kathmandu, Nepal
| | | | - Peter S. Holck
- University of Hawaii, John A Burns School of Medicine, Honolulu, Hawaii
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- Himalayan Rescue Association, Kathmandu, Nepal
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- Himalayan Rescue Association, Kathmandu, Nepal
- Stanford University Medical Center, Stanford, California
| | - Sarah Williams
- Stanford University Medical Center, Stanford, California
| | - Eric A. Weiss
- Stanford University Medical Center, Stanford, California
| | - Jeremy J. Farrar
- Oxofrd University Clinical Research Unit, The Hospital for Tropical Diseases, Ho Chi Minh City, Viet Nam
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Richalet JP, Rivera-Ch M, Maignan M, Privat C, Pham I, Macarlupu JL, Petitjean O, León-Velarde F. Acetazolamide for Monge's Disease. Am J Respir Crit Care Med 2008; 177:1370-6. [DOI: 10.1164/rccm.200802-196oc] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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32
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Severinghaus JW. Sightings. High Alt Med Biol 2007. [DOI: 10.1089/ham.2007.8403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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