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At least 415 records · Page 23Linked to original sources
PubMed2000

Intraocular pressure and acclimatization to 4300 M altitude.

BACKGROUND: Studies were conducted to determine the effect of altitude exposure on intraocular pressure (IOP) and any relationship with the severity of acute mountain sickness (AMS). HYPOTHESES: a) IOP is decreased during exposure to 4300 m altitude; b) there is a positive correlation between IOP and AMS; and c) there is a correlation between changes in urinary catecholamines and IOP. METHODS: IOP (noncontact tonometry) was measured in 11 resting males during acute simulated altitude (446 mmHg, < 2 h, hypobaric chamber), during altitude acclimatization (15 d at 4300 m), and in 6 of the 11 volunteers during re-exposure in the chamber after 8 d at sea level (Study A). In a second study (Study B) of 12 females, IOP (contact tonometry) and 24-h urinary catecholamines were measured during a 50-h chamber exposure (446 mmHg). AMS severity was assessed using the Environmental Symptoms Questionnaire (ESQ-C). RESULTS: IOP decreased 25% after 2 d at altitude and returned toward sea level values by 15 d (Study A). IOP was reduced 13% after 5 h of exposure followed by return toward sea level values (Study B). Significant correlation was found between the sea level IOP and ESQ-C (Study A); significant correlation was found between the reduction in IOP and the ESQ-C and urinary epinephrine concentrations (Study B). CONCLUSIONS: Altitude exposure resulted in a reduction in IOP that occurred within hours and recovered during acclimatization. This reduction may be related to increases in epinephrine concentration. Measurement of IOP before and during altitude exposure may provide an objective method of assessing an individual's response to hypoxic stress.

Acclimatization↗
PubMed2002

Reduced tolerance of simulated altitude (4200 m) in young men with borderline hypertension.

BACKGROUND: Primary hypertensives who are acutely exposed to hypoxic hypoxia show an enhanced reactivity of arterial chemoreceptors as well as an exaggerated response of the sympathetic nervous system. Since these phenomena could influence their ability to tolerate sustained hypoxic hypoxia, this study was performed to determine whether persons predisposed to hypertension have a normal tolerance of simulated high altitude. METHODS: Subjects were 18 young men with a family history of hypertension (sons of hypertensives, SOHT) whose BP values were in the upper normal or borderline hypertensive range. Controls were 15 young men without parental hypertension (sons of normotensives, SONT) who had normal BP values. Each subject underwent both a control and an altitude experiment. The latter consisted of an 8-h exposure to hypobaric hypoxia (equivalent to 4200 m) while resting supine in an altitude chamber. Fluids were administered by mouth and by intravenous line to produce sustained diuresis. Variables measured included heart rate, BP, respiratory rate, O2 saturation, urine flow rate, and sodium excretion. RESULTS: All subjects tolerated the control experiment and all SONT also completed altitude exposure. However, 8 of 18 SOHT developed antidiuresis and had to leave the chamber early due to symptoms of mild acute mountain sickness. Compared with SONT, SOHT exhibited more stable cardiorespiratory parameters at altitude. CONCLUSIONS: The data support the hypothesis that borderline hypertensives have stronger cardiorespiratory responses to altitude than controls, a response that is compatible with higher excitability of their arterial chemoreceptors. However, their altitude tolerance is reduced even at rest, probably because of the renal effects of an exaggerated response in the sympathetic nervous system.

Adaptation, Physiological↗
PubMed2004

[Visiting high altitudes--healthy persons and patients with risk diseases].

At altitudes higher than the threshold altitude of 2,500 m, high-altitude diseases may occur, usually after a delay of 6 to 12 hours. Apart from the headache associated with acute mountain sickness, life-threatening cerebral edema may develop. High-altitude pulmonary edema is a non-cardiac edema that often precedes acute mountain sickness. The most important preventive measure is a slow ascent. In the case of mountain sickness a prophylactic effect can be achieved with acetazolamide or dexamethasone possible, while for high-altitude pulmonary edema, nifedipine is the first-choice drug. Immediate descent and the administration of oxygen are always indicated. Patients with a high-altitude risk are those with cardiac or pulmonary disease. Nevertheless, it is still possible for patients with coronary heart disease, hypertension or bronchial asthma to attain to high altitudes. In contrast, patients with COPD, interstitial pulmonary disease or pulmonary hypertension are at appreciably greater risk.

Acclimatization↗
PubMed2005

Altitude, exercise and immune function.

Little is known with regard to how acute and chronic high altitude exposure effects immune function. Hypoxia is an environmental stressor that is known to elicit alterations in both the autonomic nervous system and endocrine function. Alterations in these systems can have an immediate as well as a longer lasting impact on immune function. Studies from the summit of Pikes Peak (4300 m) have indicated a strong alpha- & beta-adrenergic component in the regulation of immune function at altitude that can persist weeks after initial exposure. Specifically, interleukin (IL)-6 is elevated with acute altitude exposure primarily mediated via beta-adrenergic stimulation and remains elevated for several weeks as a result of alpha-adrenergic activation. When the added stress of physical exercise is combined with that of hypoxia, a more pronounced impact on immune function is observed compared to that of either exercise or hypoxia alone. A popular training paradigm currently employed by endurance athletes to enhance performance involves living at high altitude while training at low altitude. The concept entails incorporating the physiologic and metabolic adaptations associated with chronic high altitude exposure (increase in RBC, mitochondrial oxidative capacity, capillary density, etc) while training at a lower altitude allowing for the maintenance of a high absolute training intensity. Others have demonstrated that a short-term application (18 days) of the live high-train low paradigm results in suppression of the mucosal immune system as indicated by a cumulative decline in salivary IgA levels. Taken together, the majority of evidence suggests a potential additive effect of combined hypoxia and exercise in transiently suppressing immune function, at least in the short-term. Implications for the athletes and training are addressed.

Acclimatization↗
PubMed1983

Maximal exercise during hypobaric hypoxia (447 Torr) in moderate-altitude natives.

Six low-altitude natives (LAN) (373 m or less, aged 19-25 yr) and eight moderate-altitude natives (MAN) (1830-2200 m, aged 19-23 yr) were studied at both their residence (home) altitude (740 Torr and 587 Torr, respectively) and in a hypobaric chamber at a simulated altitude of 4270 m (447 Torr). Following a 2-d adaptation period, subjects performed an incremented test on the cycle ergometer until voluntary exhaustion. Significantly (P less than 0.05) greater differences in percent change of maximum exercise variables (total exercise time, exercise intensity, VO2, VCO2, VE/VO2 and HR) were noted in the LAN group than in the MAN group, going from their residence altitude to 447 Torr. The decrement in VO2max was 15% in the MAN group compared to 34% in the LAN group. The anaerobic threshold (% VO2max), estimated from VE BTPS measurements, was similar in both groups at residence altitude and at 447 Torr. In the morning prior to exercise testing at 447 Torr, LAN subjects reported greater (P less than 0.001) symptoms of acute mountain sickness (AMS) than MAN subjects. Our results indicate that, with respect to maximum exercise performance, moderate-altitude natives are at an advantage during early adaptation to hypobaric hypoxia.

Adult↗
PubMed1995

Physical adaptation of children to life at high altitude.

Children permanently exposed to hypoxia at altitudes of > 3000 m above sea level show a phenotypical form of adaptation. Under these environmental conditions, oxygen uptake in the lungs is enhanced by increases in ventilation, lung compliance, and pulmonary diffusion. Lung and thorax volumes in children growing up at high altitude are increased. The haemoglobin concentration in highlanders is elevated. With respect to the decreased arterial oxygen tension at high altitude, this seems a useful adaptation. Blood viscosity also increases as a result of the increase in red blood cell concentrations however, and this has potentially negative effects on the microcirculation in the tissues. The decreased partial pressure of oxygen in the lungs of highland children is associated with a higher pulmonary artery pressure. Pulmonary hypertension, high altitude pulmonary oedema, and chronic mountain sickness form part of the pathophysiology afflicting highland dwellers. Birth weight at high altitude is decreased. Decreased postnatal growth has been widely reported in populations at high altitude, particularly in early studies from the Andes. Recent studies taking into account the effects of socio-economic deprivation, suggest that long-term exposure to altitudes of 2500-3900 m is associated with a moderate reduction in linear growth in children.

2,3-Diphosphoglycerate↗
PubMed1997

Ventilation and hypoxic ventilatory response of Tibetan and Aymara high altitude natives.

Newcomers acclimatizing to high altitude and adult male Tibetan high altitude natives have increased ventilation relative to sea level natives at sea level. However, Andean and Rocky Mountain high altitude natives have an intermediate level of ventilation lower than that of newcomers and Tibetan high altitude natives although generally higher than that of sea level natives at sea level. Because the reason for the relative hypoventilation of some high altitude native populations was unknown, a study was designed to describe ventilation from adolescence through old age in samples of Tibetan and Andean high altitude natives and to estimate the relative genetic and environmental influences. This paper compares resting ventilation and hypoxic ventilatory response (HVR) of 320 Tibetans 9-82 years of age and 542 Bolivian Aymara 13-94 years of age, native residents at 3,800-4,065 m. Tibetan resting ventilation was roughly 1.5 times higher and Tibetan HVR was roughly double that of Aymara. Greater duration of hypoxia (older age) was not an important source of variation in resting ventilation or HVR in either sample. That is, contrary to previous studies, neither sample acquired hypoventilation in the age ranges under study. Within populations, greater severity of hypoxia (lower percent of oxygen saturation of arterial hemoglobin) was associated with slightly higher resting ventilation among Tibetans and lower resting ventilation and HVR among Aymara women, although the associations accounted for just 2-7% of the variation. Between populations, the Tibetan sample was more hypoxic and had higher resting ventilation and HVR. Other systematic environmental contrasts did not appear to elevate Tibetan or depress Aymara ventilation. There was more intrapopulation genetic variation in these traits in the Tibetan than the Aymara sample. Thirty-five percent of the Tibetan, but none of the Aymara, resting ventilation variance was due to genetic differences among individuals. Thirty-one percent of the Tibetan HVR, but just 21% of the Aymara, HVR variance was due to genetic differences among individuals. Thus there is greater potential for evolutionary change in these traits in the Tibetans. Presently, there are two different ventilation phenotypes among high altitude natives as compared with sea level populations at sea level: lifelong sustained high resting ventilation and a moderate HVR among Tibetans in contrast with a slightly elevated resting ventilation and a low HVR among Aymara.

Acclimatization↗
PubMed1999

Effect of developmental and ancestral high-altitude exposure on VO(2)peak of Andean and European/North American natives.

Peak oxygen consumption (VO(2)peak) was measured in 150 adult males (18-35 years old) in Bolivia, using a complete migrant study design to partition developmental from ancestral (genetic) effects of high-altitude (HA) exposure. High-altitude natives (HANs, Aymara/Quechua ancestry, n = 75) and low-altitude natives (LANs, European/North American ancestry, n = 75) were studied at high altitude (3,600-3,850 m) and near sea level (420 m). HAN and LAN migrant groups to a nonnative environment were classified as: multigeneration migrants, born and raised in a nonnative environment; child migrants who migrated to the nonnative environment during the period of growth and development (0-18 years old); and adult migrants who migrated after 18 years of age. Variability in VO(2)peak due to high-altitude adaptation was modeled by covariance analysis, adjusting for fat-free mass and physical activity (training) differences between groups. A trend for increased VO(2)peak with increasing developmental high-altitude exposure in migrant groups did not reach statistical significance, but low statistical power may have limited the ability to detect this effect. HANs and LANs born, raised, and tested at high altitude had similar VO(2)peak values, indicating no genetic effect, or an effect much smaller than that reported previously in the literature. There was no functional correlation between forced vital capacity and VO(2)peak, within or across groups. These results do not support the hypothesis that Andean HANs have been selected to express a greater physical work capacity in hypoxia.

Adaptation, Physiological↗
PubMed1979

A multinational Andean genetic and health program. VIII. Lung function changes with migration between altitudes.

Studies of lung function in high altitude populations have suggested the influence of hypoxic environment on the development of this characteristic independent of confounding variables such as ethnicity and habitual exercise. However, often the effect of altitude on vital capacity is greater in children than adults, suggesting that more than developmental adaptation is operative. Also selective migration could account for the similarity of migrants and permanent residents at a destination altitude. To explore these problems we studied the lung function (FVC, FEV1, PFR) of 377 individuals who had migrated between altitudes in northern Chile. Migrant measurements were adjusted to those of permanent residents of appropriate age, sex and height at the altitudes of origin and destination. The measurements were then related to ethnicity (Spanish-Aymara ancestry), occupation and permanence, the latter combining information on both age at migration to and length of stay at a destination altitude. Upward migration was associated with increased chest depth, FVC and FEV1, but not height or other chest measurements. Downward migration had no significant effect. The flow-dependent test PFR was so sensitive to observer variability and occupation that it was difficult to establish its relationship to permanence. Unlike the body measurements, lung function measurements (especially PFR) tended to deviate from permanent controls at the origin altitude in a direction suggestive of selective migration, nor was permanence itself independent of ethnicity and occupation. Because of these difficulties the question of developmental adaptation in lung function may not be answerable in cross-sectional studies like the present and previous efforts, but rather in longitudinal investigations in which the control is the individual him/herself.

Adaptation, Physiological↗
PubMed2006

Effect of the interaction between high altitude and socioeconomic factors on birth weight in a large sample from South America.

Several studies of South American populations showed that altitude is associated with low birth weight and intrauterine growth retardation. Although some of them analyzed the altitude-birth weight association, only a few assessed the effect of the interaction between altitude and socioeconomic factors on birth weight. The purpose of this research is to evaluate such effects on birth weight, after adjustment for confounding factors. This observational descriptive study includes a sample of 37,022 live-born infants without congenital anomalies, weighing >or=500 g, from 75 South American maternity hospitals, during 1982-1999. Of the total sample, 1,187 infants were born in two South American cities located at more than 2,000-m altitude: La Paz, Bolivia (N = 974 at 3,600 m) and Bogota, Colombia (N = 274 at 2,600 m). Among the seven risk factors analyzed, altitude was the main predictor of birth weight (except for gestational age). After adjustment for the other risk factors, birth weight at cities located above 2,000 m showed a decrease of approximately 200 g. When comparing highest and lowest socioeconomic levels, birth weight also showed differences for levels of altitude analyzed (lowland, <2,000 m; middle land, 2,600 m; and highland, 3,600 m). Interaction between both factors showed no effect. High altitude seems to act independent of socioeconomic status in explaining birth weight reduction.

Altitude↗
PubMed1987

Changes of heart rate and QT interval at high altitude in alpinists: analysis by Holter ambulatory electrocardiogram.

The purpose of this study is to record continuously electrocardiograms of alpinists during different activities practiced in mountaineering, compare heart rate and QT interval at high altitude with those at sea level, and compare alpinists with nonalpinists. Analysis was attempted on 14 alpinists (9 male, 5 female, ages 26-45) to determine changes in heart rate and QT interval using continuous ambulatory electrocardiograms recorded at sea level and high altitude. Between 1983 and 1984, 9 of 14 alpinists (6 male, 3 female) were subjected to the study at high altitude, that is, at Mt. Kangchenjunga (Himalaya), Mt. Satopanth (Himalaya), and Mt. Jitudake (Butan), 4400 to 7800 m (mean 5710 m). The following were noted: Heart rate at high altitude was significantly higher both in daytime and nighttime. The circadian rhythm of the heart rate disappeared at extremely high altitude in several alpinists. A high correlation was noted between measured QT interval (QTm) and RR interval (r = 0.81, p = 0.005). Nighttime QTm at high altitude was prolonged in comparison with that of daytime so far as the RR interval remained the same. At high altitude, the nighttime corrected QT interval (QTc) was also significantly prolonged in spite of shortened RR interval. The mechanism of QTc prolongation is not clear. Many factors may impact on the QT interval during mountaineering.

Altitude↗
PubMed1976

A stereological analysis of the ultrastructure of the lungs of wild mice living at low and high altitude.

Stereological analysis of the ultrastructural composition of the pulmonary alveolo-capillary region of mice living at sea level compared with that of the same species (Phyllotis darwini) genetically adapted to life at 4,660 m reveals a trend at high altitude towards a greater volume percentage of tissue components. On a weight-specific basis, non-circulating tissue occupies a significantly greater volume in high-altitude mice, but air space and capillary contents are not correspondingly greater. Since the arithmetic mean thickness of the tissue layers and of the air-blood barrier are the same in the two altitudinal groups, the average alveolus must have a smaller volume in the high-altitude mice. Epithelial, endothelial, and erythrocyte surface areas per gram body weight are significantly greater in the high-altitude mice. Nuclear counts indicate that the larger lungs of mice adapted to high altitude are due to larger Pneumocyte I and II and endothelial cells rather than to an increase in the number of these cells. Hematocrits measured within the pulmonary capillaries in the two altitudinal groups were equal. An heretofore unrecognized feature of possible adaptive value is the surface/volume ratio of erythrocytes, which is similar for erythrocytes in alveolar space of mice at low and high altitudes but within lung capillaries is 14.7% greater at high altitude.

Acclimatization↗
PubMed1993

High altitude tissue adaptation in Andean coots: capillarity, fibre area, fibre type and enzymatic activities of skeletal muscle.

Capillarity, fibre types, fibre area and enzyme activities of different skeletal muscles (pectoralis, extensor digitorum longus), tibialis anterior, plantaris and the myocardium) were compared in Andean coot (Fulica americana peruviana) native to high altitude (Junín, Perú, 4200 m) and the same species nesting at sea level. Numbers of capillaries per square millimeter were higher in all high-altitude muscles when compared with sea-level muscles (P < 0.0001). Moreover, values for capillaries per fibre and capillaries in contact with each fibre were higher in digitorum and tibialis high-altitude muscles. Muscle fibres were classified as Type I, Type IIA or Type IIB on the basis of their myofibrillar ATPase pH lability. Pectoralis muscle of high-altitude and sea-level coots presented only fibres of Type IIA. In contrast, all the leg muscles studied showed a mosaic pattern of the three fibre types. Fibre areas were determined using a Leitz Texture Analysis System. Significant differences in fibre area were observed (P < 0.01) between high-altitude and sea-level muscles. Mean muscle fibre diameters were also lower in the high-altitude group than in the sea-level group. The enzyme activities studied were hexokinase, lactate dehydrogenase, citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase. The oxidative capacity, as reflected by citrate synthetase and hydroxyacyl-CoA-dehydrogenase activities, was greater for myocardial and pectoralis than for leg muscles. However, analysis of maximal enzyme activities showed that there were no significant differences between the glycolytic and oxidative enzyme activities of high-altitude and sea-level coots.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1995

Estimation of the degree of acclimatization to high altitude by a rapid and simple physiological examination.

The recent expansion in the geographical areas open to human activity has made it desirable to have an objective method to evaluate the degree of high-altitude acclimatization. In this study, we measured the arterial oxygen saturation value at rest and just after exercise in healthy high-altitude trekkers using a transportable pulse oximeter. During a 100-day stay at high altitude (around 4000 m), the degree of arterial hemoglobin saturation measured at rest was relatively stable. However, shortly after arrival at high altitude, even light exercise induced an acute reduction in the degree of arterial hemoglobin saturation; this reduction was ameliorated as the trekkers became acclimatized to the high altitude. Preliminary short trekking to high altitudes does not appear sufficient to induce this response. It is suggested that this rapid and simple physiological examination, the measurement of arterial oxygen saturation value after light exercise, could be a convenient means of estimating the level of high-altitude acclimatization among healthy subjects.

Acclimatization↗
PubMed1995

Effects of altitude on top speeds during 1 h unaccompanied cycling.

The present world record for 1 h unaccompanied cycling (55.291 km) was set by T. Rominger in November 1994 at sea level (Bordeaux, France). However, maximal aerobic cycling performances can be expected to increase at altitude because, for a given air temperature, air density decreases more than VO2max. The combined effect of these opposite trends results in an improvement of performances. In this study, based on the aerodynamics of track cycling, and assuming an average decrease of VO2max with altitude as from the literature, we show that the ideal altitude for Rominger is 4000 m where he could cover 60.1 km in 1 h. To our knowledge, only two cyclists attempted at close time intervals to set the 1 h record at sea level and at altitude (Mexico, 2230 m above sea level): F. Moser and J. Longo. Their increase of performance with altitude was only about 50% of that predicted on the basis of similar calculations as performed on Rominger. This suggests that the decrease of VO2max resulting from altitude is greater for athletes than for average trained subjects and/or that the fraction of VO2max that can be maintained throughout 1 h decreases with altitude.

Altitude↗
PubMed1991

Altitude diuresis: endocrine and renal responses to acute hypoxia of acclimatized and non-acclimatized subjects.

As a result of our recently published studies we have thought that altitude diuresis resulting from hypoxic stimulation of the arterial chemoreceptors reduces the cardiac volume overload. To test this hypothesis, cardiovascular, endocrine and renal responses to stepwise acute exposure to simulated altitude (6,000 m) were compared in ten acclimatized recumbent mountaineers a mean of 24 days, SD 11, after descending from Himalayan altitudes of at least 4,000 m, with those found in ten non-acclimatized recumbent volunteers. The results showed that natriuresis and diuresis typified the renal responses to altitude exposure of both the acclimatized as well as non-acclimatized subjects, as long as altitude was well tolerated. It was concluded that the renal effects were mediated by atrial natriuretic peptide release and slight suppression of arginine-vasopressin (AVP) secretion, that the increased urine flow at altitude offset the cardiac (volume) overload resulting from hypoxic stimulation of the arterial chemoreceptors, and that enhanced AVP secretion, as found in the non-acclimatized subjects at and above 4,000 m, coincided with subjective and objective distress, i.e. with inadequate altitude adjustment owing to insufficient chemoreflex effects and central hypoxia.

Acclimatization↗
PubMed2002

Changes in performance, maximal oxygen uptake and maximal accumulated oxygen deficit after 5, 10 and 15 days of live high:train low altitude exposure.

Nineteen well-trained cyclists (14 males and 5 females, mean initial .VO(2max) 62.3 ml kg(-1 )min(-1)) completed a multistage cycle ergometer test to determine maximal mean power output in 4 min (MMPO(4min)), maximal oxygen uptake (.VO(2max)) and maximal accumulated oxygen deficit (MAOD). The athletes were divided into three groups, each of which completed 5, 10 or 15 days of both a control condition (C) and live high:train low altitude exposure (LHTL). The C groups lived and trained at the ambient altitude of 610 m. The LHTL groups spent 8-10 h night(-1) in normobaric hypoxia at a simulated altitude of 2,650 m, and trained at the ambient altitude of 610 m. The changes to MMPO(4min), .VO(2max) and MAOD in response to LHTL altitude exposure were not significantly different for the 5-, 10- and 15-day treatment periods. For the pooled data from all three treatment periods, there were significant increases in MMPO(4min) [mean (SD) 5.15 (0.83) W kg(-1) vs 5.34 (0.78) W kg(-1)] and MAOD [50.1 (14.2) ml kg(-1) vs 54.9 (13.1) ml kg(-1)] in the LHTL athletes between pre- and post-altitude exposure. There were no significant changes in MMPO(4min) [5.09 (0.76) W kg(-1) vs 5.16 (0.86) W kg(-1)] or MAOD [50.5 (14.1) ml kg(-1) vs 49.1 (13.0) ml kg(-1)] in the C athletes over the corresponding period. There were significant increases in .VO(2max) in the athletes during both the LHTL [63.2 (9.0) ml kg(-1 )min(-1) vs 64.1 (9.0) ml kg(-1 )min(-1)] and C [62.0 (8.6) ml kg(-1 )min(-1) vs 63.4 (9.2) ml kg(-1 )min(-1)] conditions. In these athletes, there was no difference in the impact of 5, 10 or 15 days of LHTL on the increases observed in MMPO(4min), .VO(2max) or MAOD; and LHTL increased MMPO(4min) and MAOD more than training at low altitude alone.

Adult↗
PubMed2007

Reduced hypoxic ventilatory response with preserved blood oxygenation in yoga trainees and Himalayan Buddhist monks at altitude: evidence of a different adaptive strategy?

Yoga induces long-term changes in respiratory function and control. We tested whether it represents a successful strategy for high-altitude adaptation. We compared ventilatory, cardiovascular and hematological parameters in: 12 Caucasian yoga trainees and 12 control sea-level residents, at baseline and after 2-week exposure to high altitude (Pyramid Laboratory, Nepal, 5,050 m), 38 active lifestyle high-altitude natives (Sherpas) and 13 contemplative lifestyle high-altitude natives with practice of yoga-like respiratory exercises (Buddhist monks) studied at 5,050 m. At baseline, hypoxic ventilatory response (HVR), red blood cell count and hematocrit were lower in Caucasian yoga trainees than in controls. After 14 days at altitude, yoga trainees showed similar oxygen saturation, blood pressure, RR interval compared to controls, but lower HVR (-0.44 +/- 0.08 vs. -0.98 +/- 0.21 l/min/m/%SaO(2), P < 0.05), minute ventilation (8.3 +/- 0.9 vs. 10.8 +/- 1.6 l/min, P < 0.05), breathing rate (indicating higher ventilatory efficiency), and lower red blood cell count, hemoglobin, hematocrit, albumin, erythropoietin and soluble transferrin receptors. Hypoxic ventilatory response in monks was lower than in Sherpas (-0.23 +/- 0.05 vs. -0.63 +/- 0.09 l/min/m/%SaO(2), P < 0.05); values were similar to baseline data of yoga trainees and Caucasian controls, respectively. Red blood cell count and hematocrit were lower in monks as compared to Sherpas. In conclusion, Caucasian subjects practicing yoga maintain a satisfactory oxygen transport at high altitude, with minimal increase in ventilation and with reduced hematological changes, resembling Himalayan natives. Respiratory adaptations induced by the practice of yoga may represent an efficient strategy to cope with altitude-induced hypoxia.

Acclimatization↗