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Journal of Applied Physiology... Feb 2022High-altitude exposure results in a hyperventilatory-induced respiratory alkalosis followed by renal compensation (bicarbonaturia) to return arterial blood pH (pHa)...
High-altitude exposure results in a hyperventilatory-induced respiratory alkalosis followed by renal compensation (bicarbonaturia) to return arterial blood pH (pHa) toward sea-level values. However, acid-base balance has not been comprehensively examined in both lowlanders and indigenous populations-where the latter are thought to be fully adapted to high altitude. The purpose of this investigation was to compare acid-base balance between acclimatizing lowlanders and Andean and Sherpa highlanders at various altitudes (∼3,800, ∼4,300, and ∼5,000 m). We compiled data collected across five independent high-altitude expeditions and report the following novel findings: ) at 3,800 m, Andeans ( = 7) had elevated pHa compared with Sherpas ( = 12; < 0.01), but not to lowlanders ( = 16; 9 days acclimatized; = 0.09); 2) at 4,300 m, lowlanders ( = 16; 21 days acclimatized) had elevated pHa compared with Andeans ( = 32) and Sherpas ( = 11; both < 0.01), and Andeans had elevated pHa compared with Sherpas ( = 0.01); and ) at 5,000 m, lowlanders ( = 16; 14 days acclimatized) had higher pHa compared with both Andeans ( = 66) and Sherpas ( = 18; < 0.01, and = 0.03, respectively), and Andean and Sherpa highlanders had similar blood pHa ( = 0.65). These novel data characterize acid-base balance acclimatization and adaptation to various altitudes in lowlanders and indigenous highlanders. Lowlander, Andean, and Sherpa arterial blood data were combined across five independent high-altitude expeditions in the United States, Nepal, and Peru to assess acid-base status at ∼3,800, ∼4,300, and ∼5,000 m. The main finding was that Andean and Sherpa highlander populations have more acidic arterial blood, due to elevated arterial carbon dioxide and similar arterial bicarbonate compared with acclimatizing lowlanders at altitudes ≥4,300 m.
Topics: Acclimatization; Acid-Base Equilibrium; Altitude; Altitude Sickness; Expeditions; Humans
PubMed: 35023761
DOI: 10.1152/japplphysiol.00757.2021 -
Reviews in Cardiovascular Medicine 2016Altitude plays an important role in cardiovascular performance and training for athletes. Whether it is mountaineers, skiers, or sea-level athletes trying to gain an... (Review)
Review
Altitude plays an important role in cardiovascular performance and training for athletes. Whether it is mountaineers, skiers, or sea-level athletes trying to gain an edge by training or living at increased altitude, there are many potential benefits and harms of such endeavors. Echocardiographic studies done on athletes at increased altitude have shown evidence for right ventricular dysfunction and pulmonary hypertension, but no change in left ventricular ejection fraction. In addition, 10% of athletes are susceptible to pulmonary hypertension and high-altitude pulmonary edema. Some studies suggest that echocardiography may be able to identify athletes susceptible to high-altitude pulmonary edema prior to competing or training at increased altitudes. Further research is needed on the long-term effects of altitude training, as repeated, transient episodes of pulmonary hypertension and right ventricular dysfunction may have long-term implications. Current literature suggests that performance athletes are not at higher risk for ventricular arrhythmias when training or competing at increased altitudes. For sea-level athletes, the optimal strategy for attaining the benefits while minimizing the harms of altitude training still needs to be clarified, although-for now-the "live high, train low" approach appears to have the most rationale.
Topics: Acclimatization; Altitude; Athletic Performance; Cardiovascular Diseases; Echocardiography; Electrocardiography; Humans; Physical Conditioning, Human
PubMed: 27667380
DOI: 10.3909/ricm0810 -
Advances in Marine Biology 2016To persist in an ocean changing in temperature, pH and other stressors related to climate change, many marine species will likely need to acclimatize or adapt to avoid... (Review)
Review
To persist in an ocean changing in temperature, pH and other stressors related to climate change, many marine species will likely need to acclimatize or adapt to avoid extinction. If marine populations possess adequate genetic variation in tolerance to climate change stressors, species might be able to adapt to environmental change. Marine climate change research is moving away from single life stage studies where individuals are directly placed into projected scenarios ('future shock' approach), to focus on the adaptive potential of populations in an ocean that will gradually change over coming decades. This review summarizes studies that consider the adaptive potential of marine invertebrates to climate change stressors and the methods that have been applied to this research, including quantitative genetics, laboratory selection studies and trans- and multigenerational experiments. Phenotypic plasticity is likely to contribute to population persistence providing time for genetic adaptation to occur. Transgenerational and epigenetic effects indicate that the environmental and physiological history of the parents can affect offspring performance. There is a need for long-term, multigenerational experiments to determine the influence of phenotypic plasticity, genetic variation and transgenerational effects on species' capacity to persist in a changing ocean. However, multigenerational studies are only practicable for short generation species. Consideration of multiple morphological and physiological traits, including changes in molecular processes (eg, DNA methylation) and long-term studies that facilitate acclimatization will be essential in making informed predictions of how the seascape and marine communities will be altered by climate change.
Topics: Acclimatization; Adaptation, Biological; Animals; Biological Evolution; Climate Change; Epigenomics; Gene-Environment Interaction; Genetic Variation; Invertebrates; Oceans and Seas; Stress, Physiological
PubMed: 27573050
DOI: 10.1016/bs.amb.2016.06.001 -
Journal of Thermal Biology Apr 2023Due to a long period of low humidity, exposure to the dry environment of the Tibetan Plateau can cause skin and respiratory diseases and threaten human health. To...
Due to a long period of low humidity, exposure to the dry environment of the Tibetan Plateau can cause skin and respiratory diseases and threaten human health. To examine the characteristics of acclimatization response to humidity comfort in visitors to the Tibetan Plateau based on an examination of the targeted effect and mechanism of the dry environment. A scale corresponding to local dryness symptoms was proposed. Eight participants were selected to conduct a two-week plateau experiment and a one-week plain experiment under six humidity ratios, respectively, to explore the characteristics of dry response and acclimatization of people entering the plateau. The results indicate that duration has a significant effect on human dry response. On the sixth day after entering Tibet, the degree of dryness reached the maximum, and acclimatization to the plateau environment began on the 12th day. The sensitivity of different body parts to the change in a dry environment was different. When the indoor humidity ratio increased from 9.04 g/kg to 21.77 g/kg, the symptoms of dry skin were most significantly relieved by 0.5 units of scale. After de-acclimatization, the degree of dryness in the eyes was most significantly alleviated, reducing by nearly one scale. The analysis of human symptom indicators in a dry environment shows that subjective and physiological indices are influential and essential in measuring human comfort in a dry environment. This study extends our understanding of dry environment responses and cognition of human comfort and lays a solid foundation for humid built environments in the plateau.
Topics: Humans; Acclimatization; Eye; Skin; Tibet; Respiratory Tract Diseases
PubMed: 37055112
DOI: 10.1016/j.jtherbio.2023.103493 -
The Journal of Physiology Feb 2023In recent years, there has been an explosion of new approaches (technological, methodological, pharmacological, etc.) designed to improve physical performance for... (Review)
Review
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.
Topics: Humans; Altitude; Hypoxia; Acclimatization; Oxygen Consumption; Oxygen; Physical Endurance
PubMed: 36518016
DOI: 10.1113/JP283975 -
Paediatric Anaesthesia Feb 2022Over 150 million people, including many children, live at high altitude (>2500 m) with the majority residing in Asia and South America. With increases in elevation,... (Review)
Review
Over 150 million people, including many children, live at high altitude (>2500 m) with the majority residing in Asia and South America. With increases in elevation, the partial pressure of oxygen (pO2) is reduced, resulting in a hypobaric hypoxic environment. Fortunately, humans have evolved adaptive processes which serve to acclimate the body to such conditions. These mechanisms, occurring along a specific time course, result in tachypnea, tachycardia, diuresis, and hematopoiesis, and a shift in the oxygen dissociation curve favoring an increased affinity for oxygen. These, along with other physiological effects, including increased pulmonary vascular resistance, alterations in cerebral blood flow, and changes in sensitivity to opioids, must be considered when administering anesthesia at high altitudes. Susceptible individuals or those who ascend too quickly may outpace the body's ability to acclimate resulting in one or more forms of high-altitude sickness ranging from the milder acute mountain sickness to the more serious conditions of high-altitude pulmonary edema and cerebral edema, either of which can be life-threatening if not promptly recognized and treated. Since the adaptive mechanisms for acclimatization greatly affect the cardiopulmonary systems, patients with underlying health issues such as sleep apnea, congenital heart disease, and asthma may have susceptibilities and warrant special consideration. Clinicians should have an understanding of the physiologic adaptations, anesthetic considerations, and special concerns in these populations in order to offer the best care possible.
Topics: Acclimatization; Altitude; Altitude Sickness; Child; Humans; Hypoxia; Respiratory Physiological Phenomena
PubMed: 34919777
DOI: 10.1111/pan.14380 -
International Journal of Environmental... Feb 2023This report aims to summarise the scientific knowledge around hydration, nutrition, and metabolism at high altitudes and to transfer it into the practical context of... (Review)
Review
This report aims to summarise the scientific knowledge around hydration, nutrition, and metabolism at high altitudes and to transfer it into the practical context of extreme altitude alpinism, which, as far as we know, has never been considered before in the literature. Maintaining energy balance during alpine expeditions is difficult for several reasons and requires a deep understanding of human physiology and the biological basis for altitude acclimation. However, in these harsh conditions it is difficult to reconcile our current scientific knowledge in sports nutrition or even for mountaineering to high-altitude alpinism: extreme hypoxia, cold, and the logistical difficulties intrinsic to these kinds of expeditions are not considered in the current literature. Requirements for the different stages of an expedition vary dramatically with increasing altitude, so recommendations must differentiate whether the alpinist is at base camp, at high-altitude camps, or attempting the summit. This paper highlights nutritional recommendations regarding prioritising carbohydrates as a source of energy and trying to maintain a protein balance with a practical contextualisation in the extreme altitude environment in the different stages of an alpine expedition. More research is needed regarding specific macro and micronutrient requirements as well as the adequacy of nutritional supplementations at high altitudes.
Topics: Humans; Altitude; Mountaineering; Hypoxia; Altitude Sickness; Acclimatization
PubMed: 36833880
DOI: 10.3390/ijerph20043186 -
The Journal of Physiological Sciences :... Oct 2023Heat acclimation/acclimatisation (HA) mitigates heat-related decrements in physical capacity and heat-illness risk and is a widely advocated countermeasure for... (Review)
Review
Heat acclimation/acclimatisation (HA) mitigates heat-related decrements in physical capacity and heat-illness risk and is a widely advocated countermeasure for individuals operating in hot environments. The efficacy of HA is typically quantified by assessing the thermo-physiological responses to a standard heat acclimation state test (i.e. physiological biomarkers), but this can be logistically challenging, time consuming, and expensive. A valid molecular biomarker of HA would enable evaluation of the heat-adapted state through the sampling and assessment of a biological medium. This narrative review examines candidate molecular biomarkers of HA, highlighting the poor sensitivity and specificity of these candidates and identifying the current lack of a single 'standout' biomarker. It concludes by considering the potential of multivariable approaches that provide information about a range of physiological systems, identifying a number of challenges that must be overcome to develop a valid molecular biomarker of the heat-adapted state, and highlighting future research opportunities.
Topics: Humans; Hot Temperature; Acclimatization; Biomarkers; Phenotype; Heart Rate
PubMed: 37848829
DOI: 10.1186/s12576-023-00882-4 -
Aerospace Medicine and Human Performance Aug 2015The effect of hypoxia on the exhaled nitric oxide (NO) of humans is unresolved. Many studies have measured the fraction of exhaled NO (FENO) or the partial pressure of... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
The effect of hypoxia on the exhaled nitric oxide (NO) of humans is unresolved. Many studies have measured the fraction of exhaled NO (FENO) or the partial pressure of exhaled NO (PENO) in normobaric and hypobaric hypoxia, with differing results.
METHODS
To better understand NO physiology and altitude acclimatization, we employed a random effects meta-analysis to determine the effect of acute normobaric hypoxia on the PENO of humans. A total of 93 subjects from 7 published studies (with 9 groups) were included. The median duration of exposure was 30 min and the mean hypoxic PIo2 was 95 (SD=10) mmHg.
RESULTS
The weighted standardized mean difference (SMD) in PENO measured at baseline and during an acute exposure to normobaric hypoxia was not significantly different from zero (SMD=0.09; 95% CI=-0.17, 0.34; z=0.65).
CONCLUSION
Based on this meta-analysis, acute normobaric hypoxia does not affect the PENO measured from the mouths of humans. This result should be considered for interpretations of high-altitude (and hypobaric) measurements of exhaled NO. As the PENO is a potential biomarker for altitude-illness susceptibility, recognizing that normobaric hypoxia does not affect the PENO will be important for understanding previous associations between low exhaled NO and poor acclimatization to hypoxia.
Topics: Acclimatization; Altitude; Breath Tests; Exhalation; Humans; Hypoxia; Nitric Oxide; Partial Pressure
PubMed: 26387892
DOI: 10.3357/AMHP.4172.2015 -
The New Phytologist Mar 2023The physiological challenges posed by climate change for seasonal, perennial plants include increased risk of heat waves, postbudbreak freezing ('false springs'), and... (Review)
Review
The physiological challenges posed by climate change for seasonal, perennial plants include increased risk of heat waves, postbudbreak freezing ('false springs'), and droughts. Although considerable physiological work has shown that the traits conferring tolerance to these stressors - thermotolerance, cold hardiness, and water deficit stress, respectively - are not static in time, they are frequently treated as such. In this review, I synthesize the recent literature on predictable seasonal - and therefore, phenological - patterns of acclimation and deacclimation to heat, cold, and water-deficit stress in perennials, focusing on woody plants native to temperate climates. I highlight promising, high-throughput techniques for quantifying thermotolerance, cold hardiness, and drought tolerance. For each of these forms of stress tolerance, I summarize the current balance of evidence regarding temporal patterns over the course of a year and suggest a characteristic temporal scale in these responses to environmental stress. In doing so, I offer a synthetic framework of 'phenological physiology', in which understanding and leveraging seasonally recurring (phenological) patterns of physiological stress acclimation can facilitate climate change adaptation and mitigation.
Topics: Seasons; Plants; Acclimatization; Water; Climate Change; Cold Temperature
PubMed: 36372992
DOI: 10.1111/nph.18617