High Altitude Physiology Research Articles

Mountains of research: Where and whom high-altitude physiology has overlooked.

High altitude is a natural setting in which to study human acclimatization and adaptation. Here, I identify where and in whom high-altitude physiology research has occurred. There has been a mismatch between countries with large high-altitude populations vs. where high-altitude research has been conducted. From 1970 to 2020, 83% of high-altitude physiology research took place in just seven countries: Nepal, China, USA, Peru, India, Bolivia and Italy. Collectively, these countries account for only 35% of the global population living above 2500m. Furthermore, high-altitude physiology research has predominantly studied low-altitude residents visiting high altitude and female participants are under-represented. Accordingly, the included populations are not necessarily a proportional representation of high-altitude residents. Here, I discuss how this influences our understanding of high-altitude adaptation. Finally, I highlight past initiatives to increase diversity in high-altitude research. By identifying the broad gaps in high-altitude physiology research, I propose exciting, inclusive opportunities to study human high-altitude physiology.

Pathophysiological markers of reduced resistance of healthy people to moderate hypoxic hypoxia

BACKGROUND: Despite the abundance of research in the field of high-altitude physiology and medicine, the problem of resistance to moderate hypoxia has not been practically studied. This is partly due to methodological difficulties: the studies were conducted on healthy people and climbers who tolerated the effects of moderate hypoxia well. Such studies have become necessary in connection with the development of hypoxic therapy.
 AIM: To search for indicators of the functional state of a person that are highly sensitive to the effects of moderate hypobaric hypoxia.
 MATERIAL AND METHODS: The examined group consisted of 65 practically healthy men aged 1925 years who were selected for work in high mountains. The main indicators characterizing the state of the central nervous system, cardiovascular and respiratory systems were studied in a state of relative rest and when performing a dosed two-stage bicycle ergometric test, in normoxia conditions (altitude 0) and during a pressure chamber rise in the TABAY climate complex (Japan) to altitudes of 3500 and 4500 m Statistically analyzed were the characteristics of the dynamics of indicators during the transition from normoxia to states of moderate hypoxia, correlations between indicators, their sensitivity to hypoxic effects, the significance of reactivity to hypoxic effects and mobilization of the bodys functional reserves in resistance to hypoxia.
 RESULTS: It has been shown that the key pathophysiological markers of reduced body resistance to moderate hypoxic exposure are a rapid decrease in the level of peripheral blood saturation, high reactivity of the cardiovascular and respiratory systems to hypoxic exposure, as well as excessive mobilization of the bodys functional reserves in response to additional physical activity.
 CONCLUSION: The presented materials confirm that the functional state of a healthy person under conditions of moderate hypoxia at rest is determined by the level of saturation of his peripheral blood. Maintaining saturation at a higher level ensures the maintenance of an optimal level of functional state, physical and operator performance, a lower degree of stress on the respiratory and cardiovascular systems.

Pneumolysis in COVID-19: A Novel Concept Derived from High Altitude Physiology

The COVID-19 pandemic surprised everyone with a severe lung compromise giving rise to gasping and death from respiratory insufficiency. The understanding of lung compromise is essential to advances in the field of pneumology. It is well known that the SARS-CoV-2 adheres through its spikes to the ACE-2 receptors of type II pneumocytes and introduces its RNAm material in search of its reproduction. Pneumolysis, defined as “lung destruction”, is the mechanism whereby the virus utilizes the alveolar cells to reproduce itself and destroys them in the process. The viral “attack” leads to dysfunction of the alveolar type II cells that work in conjunction with the type I alveolar cells, and a specialized thin oxygen and carbon dioxide permeable membrane. Once the virus is inside the cell, the organism’s immune system attempts to attack the virus, causing significant inflammatory reactions with remarkable ineffectiveness. The following destruction of the alveoli gives rise to a shunt, uneven ventilation-perfusion, and alteration of diffusion, generating a rapidly progressive hypoxemia that is often lethal.

High Altitude Pulmonary Edema, High Altitude Cerebral Edema, and Acute Mountain Sickness: an enhanced opinion from the High Andes- La Paz, Bolivia 3,500m.

Traveling to high altitudes for entertainment or work is sometimes associated with acute high altitude pathologies. In the past, scientific literature from the lowlander point of view was primarily based on mountain climbing. Sea level scientists developed all guidelines, but they need modifications for medical care in high altitude cities. Acute Mountain Sickness, High Altitude Pulmonary Edema, and High Altitude Cerebral Edema are medical conditions that some travelers can face. We present how to diagnose and treat acute high altitude pathologies, based on 51 years of high altitude physiology research and medical practice in hypobaric hypoxic diseases in La Paz, Bolivia (3,600m; 11,811ft), at the High Altitude Pulmonary and Pathology Institute (HAPPI- IPPA). These can occasionally present after flights to high altitude cities, both in lowlanders or high-altitude residents during re-entry. Acute high altitude ascent diseases can be adequately diagnosed and treated in high altitude cities following the presented guidelines. Treating these high-altitude illnesses, we had no loss of life. Traveling toa high altitude with sound medical advice should not be feared as it has many benefits. Nowadays, altitude descent and evacuation are not mandatory in populated highland cities, with adequate medical resources.

Ward, Milledge & West’s High Altitude Medicine and Physiology, Sixth Edition

Ward, Milledge & West’s High Altitude Medicine and Physiology, sixth edition, is the latest edition of this venerable, but hardly stodgy, book. As with the second through the fifth editions, it continues to improve. The book has come of age with the addition to the title of Michael Ward, James Milledge, and John West, authors of the first 3 editions. Milledge and West continued to the fifth edition and have now passed the baton to new, younger authors. Andrew Luks, the lead author of the sixth edition, joined as an author in the fifth edition. The other authors are all new to the book. Like Dr Luks, all of them are well-respected experts in the subject. The style is less sparse than in previous editions, but still clear and consistent. The authors have rewritten most of the material, rather than just revising the chapters, and have added a wealth of new material. New material includes updates throughout the book, based on new studies published since the fifth edition in 2013, and expansion of many areas, such as genetics and geography. The number of pages and the type size are about the same as in the fifth edition. The format of the sixth edition is larger to accommodate the additional material. The book is now divided into 3 sections: The Environment and Its People, Physiologic Responses to Hypoxia, and Clinical High Altitude Medicine. The chapters have been reorganized and rearranged. The 27 chapters, decreased from 29 in the fifth edition, are divided into many more subsections, making it easier to find information on specific topics. Another welcome change is that the references are now at the end of each chapter rather than at the back of the book. Every chapter is thoroughly referenced. Although any new textbook is already out of date by the time it is printed, this edition is as up to date as possible, with references as recent as 2020. The authors have once again anticipated future trends, pointing the way forward to help readers remain current between editions. Examples include genomic studies of high altitude adaptation and susceptibility to altitude illness, which continue to proliferate, and altitude preacclimatization. New studies of preacclimatization are likely after recently reported ascents of Mount Everest with climbers flying directly to base camp after arriving in Nepal. The authors mention that future editions are likely to include significant new information in these areas as well as others. My worst, but still minor, disappointment is that the iconic frontispiece photo of the original authors on skis during the 1960 Silver Hut expedition that graced the first 3 editions is still missing from the sixth edition. Ward, Milledge & West’s High Altitude Medicine and Physiology continues to be the foremost reference work on its subjects. It was a great pleasure to review the latest edition. I congratulate the authors on freshening and expanding the text. I recommend it to both experts and neophytes with clinical or research interests in high altitude. Before you put it on your bookshelf, preferably in easy reach so that you can refer to it often, you will probably want to read some, or even all, of the chapters.

Book Review of Ward, Milledge & West's High Altitude Medicine and Physiology, 6th Edition by Andrew Luks, Philip Ainslie, Justin Lawley, Robert Roach, and Tatum Simonson.

High Altitude Medicine & BiologyVol. 22, No. 2 Book ReviewsFree AccessBook Review of Ward, Milledge & West's High Altitude Medicine and Physiology, 6th Edition by Andrew Luks, Philip Ainslie, Justin Lawley, Robert Roach, and Tatum SimonsonPeter H. HackettPeter H. Hackett—Reviewed by: Peter H. Hackett, MD, Ridgway, Colorado, USA Search for more papers by this authorPublished Online:23 Jun 2021https://doi.org/10.1089/ham.2021.29022.hacAboutSectionsPDF/EPUB ToolsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail Ward, Milledge and West's High Altitude Medicine and Physiology, 6th edition, by Andrew Luks, Philip Ainsile, Justin Lawley, Robert Roach, and Tatum Simonson, Taylor and Francis Publishing, CRC Press, Boca Rotan, 2021, 554 pp., ISBN: 9780429444333.Sitting in a yak herder's stone hut at 4,243 m in Nepal in 1975, I was operating the Himalayan Rescue Association Pheriche Aid Post. By candlelight I was reading Michael Ward's just-published book Mountain Medicine. I could not put it down, devoured every chapter. I was an initiate in mountain medicine with minimal experience, and it was both exciting and somewhat reassuring to read a clear and comprehensive state-of-the-art book regarding all things related to mountain medicine, from the physiology of acclimatization to clinical altitude illness to cold injuries. There is no doubt that Mountain Medicine helped propel me into a lifelong career as a mountain medicine doctor. Fourteen years later, Professor Ward teamed up with his companions from the famous 1960–61 Silver Hut research expedition, JB West and JS Milledge, to produce the first edition of High Altitude Medicine and Physiology. We now are treated to the sixth edition of this landmark text, and I can imagine young physicians, physiologists, and scientists being as captivated with this new book as I was with Mountain Medicine 45 years ago.Of course, much has changed over the decades. Over 80 million humans now live at >2,500 m, and many more millions travel to high altitude for tourism, recreation, work, or other purposes. Altitude-related medical problems have correspondingly increased, as has research into both clinical and basic science aspects. Since the first edition was published in 1989, there have been ∼16,000 entries in PubMed on high-altitude medicine and physiology, and 9,000 just since the previous edition in 2013. The authors of this new edition have done a marvelous job of parsing the extensive literature to produce a volume pertinent to the practicing physician, clinical scientists, and physiologists. Andy Luks puts together a splendid team of coauthors in Drs. Ainslie, Lawley, Roach, and Simonson to do a much-needed thorough revision of the previous edition.The 6th edition for the first time includes 49 figures with color, a very attractive enhancement. The 194 black-and-white figures are 40 more than the previous edition. The book is a bit physically larger (8 × 11.5 in) than the previous, with nicely done font and formatting that makes it easier reading. The spectacular cover photo of Ama Dablam was taken from above Pheriche by Dr. Luks when he was working at the clinic years ago. I like that they put the references at the end of each chapter instead of all together at the end of the book. More importantly, the authors have rigorously edited and updated the references, providing an excellent resource for readers.Although the chapters are titled nearly the same as the 5th edition, the authors have meticulously revised the material. A section on genomics is new. Special populations and patients with pre-existing medical problems receive more attention. I was disappointed that the chapter on athletes and altitude was removed from the previous edition, but much of the content was incorporated into the exercise chapter. Chapter 1 on the history of high-altitude medicine and physiology now encompasses research projects up to the last few years, a major upgrade from the previous edition.Overall, Dr. Luks and his crew took on a major revision of this textbook, did an outstanding job, and delivered a must-have addition to our home and institutional libraries. For physicians and scientists interested in high-altitude medicine and physiology, upgrading to this new edition is more than worthwhile.FiguresReferencesRelatedDetails Volume 22Issue 2Jun 2021 InformationCopyright 2021, Mary Ann Liebert, Inc., publishersTo cite this article:Peter H. Hackett.Book Review of Ward, Milledge & West's High Altitude Medicine and Physiology, 6th Edition by Andrew Luks, Philip Ainslie, Justin Lawley, Robert Roach, and Tatum Simonson.High Altitude Medicine & Biology.Jun 2021.242-242.http://doi.org/10.1089/ham.2021.29022.hacPublished in Volume: 22 Issue 2: June 23, 2021PDF download

Hypoxia and Inflammation: Insights From High-Altitude Physiology.

The key regulators of the transcriptional response to hypoxia and inflammation (hypoxia inducible factor, HIF, and nuclear factor-kappa B, NF-κB, respectively) are evolutionarily conserved and share significant crosstalk. Tissues often experience hypoxia and inflammation concurrently at the site of infection or injury due to fluid retention and immune cell recruitment that ultimately reduces the rate of oxygen delivery to tissues. Inflammation can induce activity of HIF-pathway genes, and hypoxia may modulate inflammatory signaling. While it is clear that these molecular pathways function in concert, the physiological consequences of hypoxia-induced inflammation and how hypoxia modulates inflammatory signaling and immune function are not well established. In this review, we summarize known mechanisms of HIF and NF-κB crosstalk and highlight the physiological consequences that can arise from maladaptive hypoxia-induced inflammation. Finally, we discuss what can be learned about adaptive regulation of inflammation under chronic hypoxia by examining adaptive and maladaptive inflammatory phenotypes observed in human populations at high altitude. We aim to provide insight into the time domains of hypoxia-induced inflammation and highlight the importance of hypoxia-induced inflammatory sensitization in immune function, pathologies, and environmental adaptation.

Effects of High Altitude on Sleep and Respiratory System

The purpose of this review is to discuss the pathogenesis, clinical manifestations, and diagnosis treatment of sleep apnea at high altitude as well and acute altitude illnesses. Differences in adaptive responses of different native highlander populations are leading to interesting new insights into high-altitude physiology. Periodic breathing at altitude is a physiologic response to hypobaric oxygen and patients with obstructive sleep apnea have transition of respiratory events from obstructive to central at altitude. Acetazolamide is first-line therapy for periodic breathing at altitude. Other acute altitude illnesses are best treated with descent to a lower altitude.

RETRACTED: Acute Mountain Sickness, High Altitude Pulmonary Edema, and High Altitude Cerebral Edema: A view from the High Andes

Travelling to high altitude for entertainment or work is sometimes associated with acute high altitude pathologies. In the past, scientific literature from the lowlanders' point of view was mostly based on mountain climbing. Nowadays, descent is not mandatory in populated highland cities. We present how to diagnose and treat acute high altitude pathologies (hypobaric hypoxic diseases) based on 50 years of experience in both: high altitude physiology research and medical practice as clinicians, in La Paz, Bolivia (3,600 m; 11,811 ft), at the High Altitude Pulmonary and Pathology Institute (HAPPI - IPPA). Acute Mountain Sickness, High Altitude Pulmonary Edema, and High Altitude Cerebral Edema are medical conditions faced by some travelers. These can occasionally present after flights to high altitude cities, both in lowlanders or in high altitude residents during re-entry, having spent more than 20 days at sea level. Traveling to high altitude should not be feared as it has many benefits; Acute high altitude ascent diseases can be adequately diagnosed and treated without descent.

A tribute to some of the doctors who died from COVID-19

A tribute to some of the doctors who died from COVID-19

Geographic components of SARS-CoV-2 expansion: a hypothesis.

The emergence of COVID-19 infection (caused by the SARS-CoV-2 virus) in Wuhan, China in the latter part of 2019 has, within a relatively short time, led to a global pandemic. Amidst the initial spread of SARS-CoV-2 across Asia, an epidemiologic trend emerged in relation to high altitude (HA) populations. Compared with the rest of Asia, SARS-CoV-2 exhibited attenuated rates of expansion with limited COVID-19 infection severity along the Tibetan plateau. These characteristics were soon evident in additional HA regions across Bolivia, central Ecuador, Nepal, Bhutan, and the Sichuan province of mainland China. This mini-review presents a discussion surrounding attributes of the HA environment, aspects of HA physiology, as well as, genetic variations among HA populations which may provide clues for this pattern of SARS-CoV-2 expansion and COVID-19 infection severity. Explanations are provided in the hypothetical, albeit relevant historical evidence is provided to create a foundation for future research.

Relationship between cardiorespiratory phase coherence during hypoxia and genetic polymorphism in humans.

Key points High altitude‐induced hypoxia in humans evokes a pattern of breathing known as periodic breathing (PB), in which the regular oscillations corresponding to rhythmic expiration and inspiration are modulated by slow periodic oscillations.The phase coherence between instantaneous heart rate and respiration is shown to increase significantly at the frequency of periodic breathing during acute and sustained normobaric and hypobaric hypoxia.It is also shown that polymorphism in specific genes, NOTCH4 and CAT, is significantly correlated with this coherence, and thus with the incidence of PB.Differences in phase shifts between blood flow signals and respiratory and PB oscillations clearly demonstrate contrasting origins of the mechanisms underlying normal respiration and PB.These novel findings provide a better understanding of both the genetic and the physiological mechanisms responsible for respiratory control during hypoxia at altitude, by linking genetic factors with cardiovascular dynamics, as evaluated by phase coherence. Periodic breathing (PB) occurs in most humans at high altitudes and is characterised by low‐frequency periodic alternation between hyperventilation and apnoea. In hypoxia‐induced PB the dynamics and coherence between heart rate and respiration and their relationship to underlying genetic factors is still poorly understood. The aim of this study was to investigate, through novel usage of time–frequency analysis methods, the dynamics of hypoxia‐induced PB in healthy individuals genotyped for a selection of antioxidative and neurodevelopmental genes. Breathing, ECG and microvascular blood flow were simultaneously monitored for 30 min in 22 healthy males. The same measurements were repeated under normoxic and hypoxic (normobaric (NH) and hypobaric (HH)) conditions, at real and simulated altitudes of up to 3800 m. Wavelet phase coherence and phase difference around the frequency of breathing (approximately 0.3 Hz) and around the frequency of PB (approximately 0.06 Hz) were evaluated. Subjects were genotyped for common functional polymorphisms in antioxidative and neurodevelopmental genes. During hypoxia, PB resulted in increased cardiorespiratory coherence at the PB frequency. This coherence was significantly higher in subjects with NOTCH4 polymorphism, and significantly lower in those with CAT polymorphism (HH only). Study of the phase shifts clearly indicates that the physiological mechanism of PB is different from that of the normal respiratory cycle. The results illustrate the power of time‐evolving oscillatory analysis content in obtaining important insight into high altitude physiology. In particular, it provides further evidence for a genetic predisposition to PB and may partly explain the heterogeneity in the hypoxic response.

Population Genomics Analysis Revealed Origin and High-altitude Adaptation of Tibetan Pigs

Tibetan pig is native to the Qinghai-Tibet Plateau and has adapted to the high-altitude environmental condition such as hypoxia. However, its origin and genetic mechanisms underlying high-altitude adaptation still remain controversial and enigmatic. Herein, we analyze 229 genomes of wild and domestic pigs from Eurasia, including 63 Tibetan pigs, and detect 49.6 million high-quality variants. Phylogenomic and structure analyses show that Tibetan pigs have a close relationship with low-land domestic pigs in China, implying a common domestication origin. Positively selected genes in Tibetan pigs involved in high-altitude physiology, such as hypoxia, cardiovascular systems, UV damage, DNA repair. Three of loci with strong signals of selection are associated with EPAS1, CYP4F2, and THSD7A genes, related to hypoxia and circulation. We validated four non-coding mutations nearby EPAS1 and CYP4F2 showing reduced transcriptional activity in Tibetan pigs. A high-frequency missense mutation is found in THSD7A (Lys561Arg) in Tibetan pigs. The selective sweeps in Tibetan pigs was found in association with selection against non-coding variants, indicating an important role of regulatory mutations in Tibetan pig evolution. This study is important in understanding the evolution of Tibetan pigs and advancing our knowledge on animal adaptation to high-altitude environments.

High adventure shunts old notions of pulmonary vascular control during hypoxic exercise: contrasting views that might just burst your bubble!

High adventure shunts old notions of pulmonary vascular control during hypoxic exercise: contrasting views that might just burst your bubble!

Operation Everest II and the 1978 Habeler/Messner ascent of Everest without bottled O2: what might they have in common?

In 1978, Peter Habeler and Reinhold Messner climbed Everest without supplemental O2. Subsequently, Oelz et al. (Oelz O, Howald H, Di Prampero PE, Hoppeler H, Claassen H, Jenni R, Bühlmann A, Ferretti G, Brückner JC, Veicsteinas A, Gussoni M, Cerretelli P. J Appl Physiol (1985) 60: 1734-1742, 1986) assessed their cardiopulmonary function, finding no advantageous physiological attributes to explain their success, and leading West (West JB. High Life: A History of High-Altitude Physiology and Medicine. New York: Oxford University, 1998) to suggest that grit and determination were more important. In 1985, Charlie Houston, John Sutton, and Al Cymerman hosted a scientific project assessing a simulated ascent of Everest (OE II) at the U.S. Army Research Institute of Environmental Medicine. Included were measurements of O2 transport. In particular, mixed venous Po2 was measured at/near maximal exercise, for calculating pulmonary O2-diffusing capacity. A serendipitous observation was made: while both V̇o2max and mixed venous Po2 fell with altitude (as expected), it was how they fell-in direct proportion-that was remarkable. It later became clear that this reflected diffusion limitation of O2 transport from muscle microvessels to the mitochondria, and that this last step in O2 transport plays a major role in limiting V̇o2max. Thus, how Habeler and Messner made it up Everest without bottled O2 and no special cardiopulmonary attributes might be explained if their muscle O2-diffusing capacity, which depends largely on muscle capillarity, was unusually high. Oelz et al. mention that muscle capillary density was substantially-40%-above normal, but did not suggest that this accounted for the climbers' success. Therefore, high muscle capillarity, enhancing diffusive unloading of O2, may have been a major enabling physiological attribute for Habeler and Messner and that OE II, by chance, played a key role in bringing this to light.

Physiological Changes to the Cardiovascular System at High Altitude and Its Effects on Cardiovascular Disease

Riley, Callum James, and Matthew Gavin. Physiological changes to the cardiovascular system at high altitude and its effects on cardiovascular disease. High Alt Med Biol. 18:102-113, 2017.-The physiological changes to the cardiovascular system in response to the high altitude environment are well understood. More recently, we have begun to understand how these changes may affect and cause detriment to cardiovascular disease. In addition to this, the increasing availability of altitude simulation has dramatically improved our understanding of the physiology of high altitude. This has allowed further study on the effect of altitude in those with cardiovascular disease in a safe and controlled environment as well as in healthy individuals. Using a thorough PubMed search, this review aims to integrate recent advances in cardiovascular physiology at altitude with previous understanding, as well as its potential implications on cardiovascular disease. Altogether, it was found that the changes at altitude to cardiovascular physiology are profound enough to have a noteworthy effect on many forms of cardiovascular disease. While often asymptomatic, there is some risk in high altitude exposure for individuals with certain cardiovascular diseases. Although controlled research in patients with cardiovascular disease was largely lacking, meaning firm conclusions cannot be drawn, these risks should be a consideration to both the individual and their physician.

Travel health - Travel medicine

In the post-World War II period, modern travel medicine was created as an interdisciplinary field not limited to tropical medicine and infectious diseases, but including also dive and high-altitude physiology, geriatrics, public health, etc. The goal is to keep future travellers alive and healthy, and to provide returning travellers with illness or sequelae of accidents the best possible care. With respect to both mortality and morbidity, we now have a broad idea about what is frequent, what in contrast is rare. However, particularly, the World Health Organization requests that more quality data should be generated to assure a safe evidence base for preventive recommendations. The lack of consensus on a global scale is the illustration that even 'experts' so far do not agree on all measures, be they advise immunisation or medication. A further challenge is that we are living in a constantly changing world. Hygienic conditions have improved in some locations, particularly such frequently visited by tourists and businessmen and women; also some infections are being eliminated or reduced by international efforts. On the other hand, new threats are emerging - infectious and other. Thus, in the coming decades, we must create an improved database. We must continue to be vigilant based on coordinated surveillance and we must continue to spread the news to both the travelling public and those health professionals advising them pre-departure, also those in charge of diagnosis and treatment in those returning ill or with injuries.

BEHAVIOR OF HEMOGLOBIN CONCENTRATION, HEMATOCRIT AND OXYGEN SATURATION IN COLOMBIAN UNIVERSITY POPULATION AT DIFFERENT ALTITUDES

the development of this research is base on the growing interest in understanding the adaptations to chronic hipoxia mainly in the range of intermediate altitudes (1 500-3 000 m.s.n.m) and the need to establish parameters of normality in the variables [Hb], Hct and SO2 for diagnostic and characterization of the population purposes. to analyze the behavior of the [Hb], Hct and SaO2 at different intermediate altitudes (970 m.s.n.m, 1 520 m.s.n.m, 1 728 m.s.n.m, 1 923 m.s.n.m, 2 180 m.s.n.m and 2 600 m.s.n.m) in order to contribute to the knowledge of the high altitude physiology and the clinical field to support the diagnosis of anemia. clinically healthy subjects with low levels of physical activity and food consumption report containing iron. Total of 264 participants of both genders between 18 and 30 years. The blood samples were collected from the antecubital vein and the earlobe and analyzed in a radiometer. A non-parametric statistical analysis was performed. with increasing of altitude, [Hb] and Hct values were increased while the SO2 decreased. Men showed higher values than women in [Hb] and Hct, related to lower values of SO2 than women. a threshold variable was not found, perhaps because of the small distance between the altitudes. The values reported were similar but not identical to other studies. This difference could be explained by genetic diversity among populations. this study allows for the first values of characterization of the study population. All altitudes were above the cutoff for the diagnosis of anemia ([Hb] 12 g/dl).

Early history of high-altitude physiology.

High-altitude physiology can be said to have begun in 1644 when Torricelli described the first mercury barometer and wrote the immortal words "We live submerged at the bottom of an ocean of the element air." Interestingly, the notion of atmospheric pressure had eluded his teacher, the great Galileo. Blaise Pascal was responsible for describing the fall in pressure with increasing altitude, and Otto von Guericke gave a dramatic demonstration of the enormous force that could be developed by atmospheric pressure. Robert Boyle learned of Guericke's experiment and, with Robert Hooke, constructed the first air pump that allowed small animals to be exposed to a low pressure. Hooke also constructed a small low-pressure chamber and exposed himself to a simulated altitude of about 2400 meters. With the advent of ballooning, humans were rapidly exposed to very low pressures, sometimes with tragic results. For example, the French balloon, Zénith, rose to over 8000 m, and two of the three aeronauts succumbed to the hypoxia. Paul Bert was the first person to clearly state that the deleterious effects of high altitude were caused by the low partial pressure of oxygen (PO2), and later research was accelerated by high-altitude stations and expeditions to high altitude.

Travelers health: An emerging issue

Abstract Tourism in India is a large industry. International travel and commerce is here to stay and continue their global expansion. With increase in the travel trend, comes various health risks to the travelers. Children, pregnant women, older age group, people with pre-existing diseases, adventurers and sex travelers are particularly vulnerable. This is where travel medicine or emporiatrics come into light. It encompasses a wide variety of disciplines including epidemiology, infectious disease, public health, tropical medicine, high altitude physiology, travel related obstetrics, psychiatry, occupational medicine, military and migration medicine, and environmental health. In this article an attempt has been made to describe the various health risks to the travelers, their occurrence and how they can be prevented.