Simulated altitude
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This review deals with the capability of the heart to adapt to chronic hypoxia in animals exposed to either natural or simulated high altitude. From the broad spectrum of related issues, we focused on the development and reversibility of both beneficial and adverse adaptive myocardial changes. Particular attention was paid to cardioprotective effects of adaptation to chronic high-altitude hypoxia and their molecular mechanisms. Moreover, interspecies and age differences in the cardiac sensitivity to hypoxia-induced effects in various experimental models were emphasized.
- MeSH
- aklimatizace fyziologie MeSH
- atmosférický tlak MeSH
- chronická nemoc MeSH
- financování organizované MeSH
- hypoxie komplikace metabolismus MeSH
- ischemie etiologie metabolismus MeSH
- kyslík krev MeSH
- myokard metabolismus MeSH
- nadmořská výška MeSH
- reperfuzní poškození myokardu etiologie metabolismus MeSH
- věkové faktory MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- přehledy MeSH
Background: Coronary artery disease remains the leading cause of morbidity and mortality in developed countries. Despite advances in treatment and standard rehabilitation, conventional programs may be monotonous and insufficiently engaging. Normobaric hypoxia, simulating high-altitude conditions, has emerged as a potential method to enhance cardiovascular adaptations in post-myocardial infarction (MI) patients. Objective: This study aimed to compare the efficacy and safety of exercise-based cardiac rehabilitation performed under normobaric hypoxia corresponding to altitudes of 2000 m and 3000 m above sea level in patients after MI treated with percutaneous coronary intervention (PCI). Methods: A total of 61 male post-MI patients (mean age 60.4 ± 8.9 years) were randomized into two groups: training under simulated altitudes of 2000 m (n = 35) or 3000 m (n = 26). The 22-day program consisted of interval ergometer sessions. Pre- and post-intervention assessments included cardiopulmonary exercise testing (CPET), echocardiography, and tissue Doppler imaging (TDI). Results: Both groups demonstrated significant improvements in exercise tolerance. Training at 2000 m significantly increased test duration (r = 0.735) and peak heart rate (r = 0.467). At 3000 m, additional benefits were observed, including improvements in metabolic equivalent (r = 0.861), peak oxygen consumption (d = 0.81), and reduction in respiratory exchange ratio (r = 0.682). Intergroup analysis revealed moderate differences favoring the 3000 m group in MET, breathing frequency, and RER. Echocardiography showed beneficial remodeling in both groups, with improvements in LV dimensions, ejection fraction, and MAPSE. Notably, training at 2000 m resulted in more consistent echocardiographic benefits compared to 3000 m. Conclusions: Cardiac rehabilitation under normobaric hypoxia is effective and safe in stable post-MI patients. Training at 3000 m provides greater improvements in exercise tolerance, while 2000 m confers more favorable effects on cardiac structure and function. These findings suggest that moderate hypoxic exposure (2000 m) may represent an optimal balance between efficacy and safety in post-MI rehabilitation.
- Publikační typ
- časopisecké články MeSH
This study focuses on the determination of the vagal threshold (Tva) during exercise with increasing intensity in normoxia and normobaric hypoxia. The experimental protocol was performed by 28 healthy men aged 20 to 30 years. It included three stages of exercise on a bicycle ergometer with a fraction of inspired oxygen (FiO2) 20.9% (normoxia), 17.3% (simulated altitude ~1500 m), and 15.3% (~2500 m) at intensity associated with 20% to 70% of the maximal heart rate reserve (MHRR) set in normoxia. Tva level in normoxia was determined at exercise intensity corresponding with (M ± SD) 45.0 ± 5.6% of MHRR. Power output at Tva (POth), representing threshold exercise intensity, decreased with increasing degree of hypoxia (normoxia: 114 ± 29 W; FiO2 = 17.3%: 110 ± 27 W; FiO2 = 15.3%: 96 ± 32 W). Significant changes in POth were observed with FiO2 = 15.3% compared to normoxia (p = 0.007) and FiO2 = 17.3% (p = 0.001). Consequentially, normoxic %MHRR adjusted for hypoxia with FiO2 = 15.3% was reduced to 39.9 ± 5.5%. Considering the convenient altitude for exercise in hypoxia, POth did not differ excessively between normoxic conditions and the simulated altitude of ~1500 m, while more substantial decline of POth occurred at the simulated altitude of ~2500 m compared to the other two conditions.
- MeSH
- cvičení * fyziologie MeSH
- dospělí MeSH
- hypoxie MeSH
- lidé MeSH
- mladý dospělý MeSH
- nadmořská výška MeSH
- spotřeba kyslíku * MeSH
- zátěžový test MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Cílem práce bylo posouzení změn v aktivitě autonomního nervového systému (ANS) v průběhu hodinové expozice normobarické hypoxii simulující nadmořskou výšku 4 800 m a 6 000 m. Testovaný soubor tvořilo 10 mužů ve věku 24,4 ± 1,9 let. Aktivita ANS byla monitorována metodou spektrální analýzy variability srdeční frekvence (SA HRV). Ke kvantifikaci aktivity ANS bylo využito individuálních ukazatelů SA HRV. Při hypoxické simulaci 6 000 m došlo v porovnání s hodnotami těchto parametrů v simulované výšce 4 800 m a KV k signifikantnímu snížení P VLF; P LF ,P HF ,P T a ke zvýšení P VLF /P HF aP LF /P HF . Mezi simulovanou výškou 4800maKV nebyly zjištěny žádné významné rozdíly P VLF . Hodnota P HF byla v simulované výšce 4 800 m signifikantně nižší než při kontrolním vyšetření (KV). Průměrné hodnoty P VLF /P HF aP LF /P HF byly ve výšce 4 800 m signifikantně vyšší než při KV. Při dýchání s maskou byla významně vyšší průměrná hodnota P HF aP T a nižší hodnota P LF /P HF než u dýchání bez masky. Naše pilotní studie ukázala, že hypoxie v simulované výšce 6 000 m významně redukovala aktivitu obou větví ANS a přesun sympatovagové balance na stranu sympatiku byl zapříčiněn kombinací výraznějšího poklesu aktivity vagu než sympatiku. Ve výšce 4 800 m byla výrazně redukována pouze aktivita vagu. Také bylo zjištěno, že aktivita ANS byla díky použití obličejové masky ovlivňována kromě hypoxie i hyperkapnií.
The aim of this study was to assess the changes in autonomic nervous system (ANS) activity during one hour normobaric hypoxic exposure to simulated altitudes of 4800 m and 6000 m. Tested group consisted of 10 men with age 24.4 ± 1.9 year. ANS activity was assessed by using spectral analysis of heart rate variability (SA HRV) method. Individual spectral parameters were applied for quantification of ANS activity. Simulated hypoxie equal to 6000 m induced significant decrease in P VLF; P LF ,P HF ,P T , and increase in P VLF /P HF aP LF /P HF compared to both 4800 m and control measurements (CM). Average values of P VLF /P HF and P LF /P HF were significantly higher at 4800 m than in CM. Average values of P HF and P T were significantly higher during CM with mask compared to CM without mask. Our pilot study revealed that both branches of ANS were significantly blunted by hypoxie at 6000 m simulated altitude, and sympathovagal balance was shifted to relatively sympathetic dominance due to combination of higher reduction of vagal activity than sympathetic activity in this altitude. Only vagal activity was markedly reduced in the simulated altitude of 4800 m. Our study further showed that ANS activity was affected by hypoxia as well as hypercapnia when the face mask was applied.
- Klíčová slova
- variabilita srdeční frekvence, parasympatikus, hypoxická expozice, simulovaná nadmořská výška,
- MeSH
- autonomní nervový systém fyziologie MeSH
- dospělí MeSH
- financování organizované MeSH
- hyperkapnie MeSH
- hypoxie metabolismus MeSH
- lidé MeSH
- nadmořská výška MeSH
- pilotní projekty MeSH
- srdeční frekvence MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mužské pohlaví MeSH
