Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Altitude”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55Linked to original sources
PubMed1979

Effect of furosemide on altitude tolerance in experimental animals.

Furosemide which is claimed to prevent acute mountain sickness and pulmonary oedema of high altitude was tried in experimental animals to evaluate its usefulness or otherwise as a measure of prophylaxis. 90 mice, 128 rats and 44 guinea pigs--all males--were used for the studies. Half the number in each species were kept as controls. The remaining half were further divided into two batches. The first batch was given furosemide 10 mg/kg body weight. Two h later they were exposed to simulated altitude of 30,000 ft for 6 h. The second batch was given two injections of furosemide at intervals of 24 h before exposure to simulated altitude. The controls were given distilled water. Our results show that the death rate was more in the furosemide-treated groups, both under mild as well as severe dehydration in all species. The present study does not substantiate the claim than the drug can be used as prophylactic against acute mountain sickness and pulmonary oedema of high altitude.

Acclimatization↗
PubMed2006

Role of endothelin-1 in exposure to high altitude: Acute Mountain Sickness and Endothelin-1 (ACME-1) study.

BACKGROUND: The degree of pulmonary hypertension in healthy subjects exposed to acute hypobaric hypoxia at high altitude was found to be related to increased plasma endothelin (ET)-1. The aim of the present study was to investigate the effects of ET-1 antagonism on pulmonary hypertension, renal water, and sodium balance under acute and prolonged exposure to high-altitude-associated hypoxia. METHODS AND RESULTS: In a double-blind fashion, healthy volunteers were randomly assigned to receive bosentan (62.5 mg for 1 day and 125 mg for the following 2 days; n=10) or placebo (n=10) at sea level and after rapid ascent to high altitude (4559 m). At sea level, bosentan did not induce any significant changes in hemodynamic or renal parameters. At altitude, bosentan induced a significant reduction of systolic pulmonary artery pressure (21+/-7 versus 31+/-7 mm Hg, P<0.03) and a mild increase in arterial oxygen saturation versus placebo after just 1 day of treatment. However, both urinary volume and free water clearance (H2OCl/glomerular filtration rate) were significantly reduced versus placebo after 2 days of ET-1 antagonism (1100+/-200 versus 1610+/-590 mL; -6.7+/-3.5 versus -1.8+/-4.8 mL/min, P<0.05 versus placebo for both). Sodium clearance and segmental tubular function were not significantly affected by bosentan administration. CONCLUSIONS: The present results indicate that the early beneficial effect of ET-1 antagonism on pulmonary blood pressure is followed by an impairment in volume adaptation. These findings must be considered for the prevention and treatment of acute mountain sickness.

Acute Disease↗
PubMedDate not supplied

Higher venous bicarbonate concentration associated with hypoxemia, not acute mountain sickness, after ascent to moderate altitude.

BACKGROUND: The pathophysiology underlying acute mountain sickness (AMS) and excessive hypoxemia at high altitudes is not fully understood. Previous work by our group has demonstrated a significant association between urinary measures of dehydration and bicarbonate retention in subjects developing excessive hypoxemia and AMS at high altitudes. To further characterize these findings, we returned to our original testing site to examine the hypothesis that subjects with lower levels of oxygen saturation and/or AMS would possess higher levels of venous bicarbonate. METHODS: Medical history inquiry, clinical examination, Lake Louise scoring, and the collection of venous levels of bicarbonate concentration and base excess were performed on 52 lowland-dwelling persons after they completed a religious pilgrimage in the Nepal Himalayas to approximately 4,250 m. RESULTS: Oxygen saturation levels were strongly and inversely correlated with serum levels of venous bicarbonate and base excess, whereas AMS and Lake Louise scores were not associated with these measures of alkalosis. CONCLUSIONS: Our data suggest an association between measures of serum bicarbonate anion retention and decreasing oxygen saturation. Our data do not demonstrate an association between AMS or Lake Louise scores and measures of serum bicarbonate level. We propose that excessive hypoxemia at high altitudes may be associated with a compromised ability of the kidney to metabolically compensate for an altitude-induced hypocapnic alkalosis.

Adult↗
PubMed2002

High-altitude pulmonary edema: potential protection by red wine.

UNLABELLED: High-altitude pulmonary edema (HAPE) is the predominant cause of death due to high-altitude illness. At first sight, the observation that mountaineers regularly consume red wine in order to "feel better" seems to be paradoxical because, especially at higher altitudes, alcohol consumption could be detrimental. In this article, we review the potential mechanisms by which the components of red wine may beneficially affect the development of HAPE. DATA SYNTHESIS: The underlying cause of HAPE is the altitude-related reduction in barometric pressure, which leads to a decrease in partial pressure of oxygen in the alveolae and subsequently in the pulmonary capillaries and arterial system. Two cellular mechanisms have been described, both of which increase pulmonary vascular tone: enhanced endothelin 1 production and the increased generation of reactive oxygen species. Recent evidence has indicated that some of the compounds of red wine suppress endothelin 1 gene expression, and the anti-oxidative properties of red wine have been previously reported. CONCLUSION: This article briefly summarises the pathophysiological cellular events leading to HAPE and describes the potential mechanisms by which the ingredients of red wine may have a beneficial effect.

Altitude↗
PubMedDate not supplied

Is the incidence of acute mountain sickness (AMS) at medium altitude in the Austrian Alps influenced by the height of home residence of the alpinist?

UNLABELLED: In previous studies the incidence of acute mountain sickness (AMS) at medium altitude was examined in the Austrian Alps, where many tourists come from low parts of Europe. This study assesses the influence of the height of home residence on the incidence of AMS at medium altitude. The severity of high-altitude adaptation disorder was quantified by using a scoring system after an interview and a clinical examination in 84 lowlanders, mainly those from Hungary. Forty-two alpinists with a home residence of 800 to 1000 m served as control. The incidence of AMS was 1.4% at 2000 m and 7.4% in 3000 m. The most frequent symptoms were slight headache and peripheral or periorbital oedema. The AMS-score of the Hungarian alpinists did not differ significantly from that of the alpinists with a home residence of height 800 to 1000 m. CONCLUSION: in contrast to the situation at high altitude, at medium height tourists from lowlands are not at higher risk of AMS than other alpinists.

Acclimatization↗
PubMed2004

[Preconditions for a stay in high altitude areas in the case of existing health problems].

Various symptoms can arise during a stay in high altitude areas (above 2500 m), such as tissue hypoxia and in particular pulmonary and brain oedema. Patients with existing health problems can expect to develop more complaints or more severe complaints at an earlier stage. For a number of these patients a stay in high altitude areas should be advised against or should only take place if certain measures are taken. The advising physician should have knowledge about the reactions of the human body on hypoxy, and about (derailments of) the acclimatisation proces in high altitude areas. Every patient with a disease that can interfere with hypoxia should be assessed on an individual basis. The most important absolute and relative contraindications are cardiac and pulmonary conditions, haemoglobin abnormalities, diabetes mellitus, hypertension, epilepsy, severe obesity, kidney diseases and pregnancy. In the case of an existing health problem, a stay in high altitude should only be considered if medical care can be quickly and adequately provided on the spot.

Acclimatization↗
PubMed1983

Ocular functions and incidence of acute mountain sickness in women at altitude.

The effects of altitude on a series of ocular functions were studied on seven expedition members, all women aged 23-53 years, during the first ascent of the 6798-m peak Brigupanth in the Indian Himalayas. The only consistent change was a decrease in convergence amplitude. The amplitude of accommodation remained stable among the younger climbers, but decreased markedly among the older ones as higher altitudes were reached. There also appeared to be a lessened vascular reactivity to the hypoxia of altitude in the older members. Stereoscopic vision was unimpaired at all altitudes tested and extra-ocular muscle balance remained unaffected in all but two members who had an increase in their baseline phorias. Two of the summit climbers developed retinal hemorrhages. There was an average weight loss of 5.4 kg during the climb, but general health was good. Symptoms of acute mountain sickness were noted infrequently, and there were only moderate changes in the menstrual cycle.

Adult↗
PubMed1983

Neuropsychological functioning after prolonged high altitude exposure in mountaineering.

This prospective study examined the possibility of long lasting CNS sequelae of high altitude exposure in mountaineering. An extensive battery of neuropsychological and personality tests was given to 22 subjects before and after Himalayan climbs above 5334 m (17,500 ft). All subjects were at altitude for long periods without supplemental oxygen, but did not suffer other physical insults such as serious injury or food or water deprivation. Although several climbers experienced acute effects of mountain sickness while at altitude, their post-climb evaluations revealed no evidence of lasting cerebral dysfunction or psychological deficit. A few climbers' subjective ratings of mental functioning were worse after their expeditions, but these self-assessments were unsupported by their performances on the objective testing. It was concluded that in healthy people who do not suffer other physical insults as well, acute CNS effects of low oxygen tensions during high altitude climbs are reversible.

Adult↗
PubMed1980

Observation on the reactions of the albino rat in simulated altitude.

Albino rats of the Wistar family were reared from the time of birth in a simulated altitude of about 6000 meters (barometric pressure 370 mm Hg) for a period of about 50 days. A number of these were killed after losing consciousness upon exposure to acute hypoxia. The others were killed without being first subjected to the acute hypoxia. Control groups of the same stock were reared for a corresponding period of time in a normal atmosphere at sea level and killed like the previous group. The animals reared in a simulated altitude displayed an increase in the 2,3-DPG content in the red blood cells, Hb concentration and the number of erythrocytes for one ml of blood. They are to be considered phenomena of adaptation, only slightly influenced by the acute hypoxia. The animals reared in a simulated altitude also displayed a displacement of the acid-base balance of the blood towards the acid side. This was even more accentuated in the group subjected to the acute hypoxia. It was observed, via the weight curve, that the animals reared in a simulated altitude presented a slower body growth in comparison to the control group. We were not able to demonstrate significant variations in the tolerance to acute hypoxia in the various groups studied.

Acid-Base Imbalance↗
PubMed1981

Beneficial effect of rightward hemoglobin-oxygen dissociation curve shift for short-term high-altitude adaptation.

To determine whether a rightward shift of the ODC was beneficial for short-term high-altitude adaptation, 10 drug-treated subjects were compared in a double-blind manner to 10 placebo-treated subjects after ascent from Ann Arbor, Mich. (240 m) to the top of Pike's Peak, Colo. (4300 m). Subjects were normal, male residents at 240 m in good health. Phosphate (30 mmol, t.i.d.), vitamin C (500 mg, q.i.d.), and sodium bicarbonate (1.25 mEq/kg body weight) were administered in order to elevate 2,3-DPG levels and shift ODCs to the right before the ascent so that subjects with right-shifted ODCs could be contrasted with subjects whose ODCs were not right-shifted during the first 1 to 2 days at 4300 m. After 24 hr at 4300 m, 2,3-DPG levels were higher in drug-treated than in placebo-treated subjects (19.7 +/- 0.6 mmol/gm of hemoglobin vs. 18.5 +/- 0.4; p less than 0.05 by one-tailed test), and ODC positions were different after 6 hr at high altitude (one-tailed p less than 0.01). Drug-treated subjects felt better as measured by a symptomatology questionnaire and had better central nervous system function as measured by a darkness-adaptation visual task. Performance in the two groups of subjects was the same on other visual and cognitive psychometric tests. Cardiopulmonary responses to high altitude were comparable in the two groups. The small, though significant improvement in dark adaptation and symptoms in drug-treated subjects suggests that oxygenation of the brain may have benefited from the small-shift in ODC observed. Agents with greater effect on 2,3-DPG levels are deserving of trial to determine whether they have more substantial effects on short-term responses to high altitude.

Adaptation, Physiological↗
PubMed1995

The effect of altitude pre-acclimatization on acute mountain sickness during reexposure.

BACKGROUND: Acclimatization to high altitude appears to prevent acute mountain sickness (AMS), as evidenced by a decline in AMS symptoms as acclimatization progresses. HYPOTHESIS: We hypothesized that partial retention of acclimatization would attenuate the incidence and/or severity of AMS upon reinduction to altitude. METHODS: To test this hypothesis 6 male lowlanders returned to sea level after the acclimatizing of the 16 d at 4300 m (HA). After 8 d at sea level (PA), they were reexposed to 4300 m in a hypobaric chamber for 30 h (RA). AMS symptom severity was determined by the AMS-cerebral (AMS-C) scores calculated from the daily administration of the Environmental Symptoms Questionnaire during HA and RA. RESULTS: The mean AMS-C scores were reduced from 0.6 on HA day 1 (HA1) to 0.1 during RA (p < 0.05). Four subjects were "sick" (AMS-C > 0.7) during HA1, while only one was "sick" during RA. The % oxyhemoglobin, hemoglobin concentration and hematocrit were higher during RA compared to HA1. CONCLUSIONS: These results suggest that the retention of acclimatization after 8 d at low altitude is sufficient to attenuate AMS upon reinduction to high altitude.

Acclimatization↗
PubMedDate not supplied

Oxygen saturation and heart rate in healthy school children and adolescents living at high altitude.

This study was conducted to establish reference values for percent oxygen saturation of hemoglobin (SaO2, %) and heart rate (HR, bpm) in children living at high altitude (4,100 m) and to relate possible differences in the variables with ethnic origin. Healthy children from a mine-located school (Tintaya, n = 417), a nearby school (Marquiri, n = 474), and a rural Andean community (Nuñoa, n = 373) were investigated. The samples included different ethnic combinations, with the Nuñoa children having a predominant Quechua ancestry. Mean SaO2 for all ages was substantially lower in all high altitude children compared to values considered normal for sea level. Among the three samples, SaO2 was higher (91.3 +/- 2.7) and HR was lower (84.8 +/- 13.6) in Nuñoa than in Tintaya (SaO2, 89.8 +/- 2.5; HR, 91.7 +/- 14.9) and Marquiri (SaO2, 89.6 +/- 3.1; HR, 88.5 +/- 12.9) (P < 0.05). There was no sex difference and only a weak age-dependent trend for SaO2. Values considered abnormal at sea level were observed in all healthy high-altitude children. Higher SaO2 and lower HR in Nuñoa children may suggest a better degree of acclimatization to altitude.

Acclimatization↗
PubMed1980

The physical growth of high altitude Bolivian Aymara children.

This study describes the growth characteristics of Aymara children living in Ancoraimes, Bolivia at altitudes between 3800 and 4000 meters. Anthropometric measurements were made on 510 children between the ages of 6.0 and 20.9 years, 360 males and 150 females. The growth pattern of Ancoraimes Aymara children is very similar to that of other high altitude Andean populations. They are greatly delayed in height and weight, exhibit little sexual dimorphism in body size and, relative to stature, have larger chest dimensions than U.S. children. Compared to Quechua children living at higher altitudes in Peru, Ancoraimes children tend to be taller and heavier but have significantly smaller chest dimensions. Although the causes of the size differences between these two groups are not entirely clear, they may be due to the different altitudes at which the groups reside.

Adolescent↗
PubMed2005

Body proportions in ancient Andeans from high and low altitudes.

Living human populations from high altitudes in the Andes exhibit relatively short limbs compared with neighboring groups from lower elevations as adaptations to cold climates characteristic of high-altitude environments. This study compares relative limb lengths and proportions in pre-Contact human skeletons from different altitudes to test whether ecogeographic variation also existed in Andean prehistory. Maximum lengths of the humerus, radius, femur, and tibia, and femoral head breadth are measured in sex-specific groups of adult human skeletons (N = 346) from the central (n = 80) and the south-central (n = 123) Andean coasts, the Atacama Desert at 2,500 m (n = 102), and the southern Peruvian highlands at 2,000-3,800 m (n = 41). To test whether limb lengths vary with altitude, comparisons are made of intralimb proportions, limb lengths against body mass estimates derived from published equations, limb lengths against the geometric mean of all measurements, and principal component analysis. Intralimb proportions do not statistically differ between coastal groups and those from the Atacama Desert, whereas intralimb proportions are significantly shorter in the Peruvian highland sample. Overall body size and limb lengths relative to body size vary along an altitudinal gradient, with larger individuals from coastal environments and smaller individuals with relatively longer limbs for their size from higher elevations. Ecogeographic variation in relation to climate explains the variation in intralimb proportions, and dietary variation may explain the altitudinal cline in body size and limb lengths relative to body size. The potential effects of gene flow on variation in body proportions in Andean prehistory are also explored.

Altitude↗
PubMed2001

Heat and water rate transfer processes in the human respiratory tract at various altitudes.

The process of the respiratory air conditioning as a process of heat and mass exchange at the interface inspired air-airways surface was studied. Using a model of airways (Olson et al., 1970) where the segments of the respiratory tract are like cylinders with a fixed length and diameter, the corresponding heat transfer equations, in the paper are founded basic rate exchange parameters-convective heat transfer coefficient h(c)(W m(-2) degrees C(-1)) and evaporative heat transfer coefficient h(e)(W m(-2)hPa(-1)). The rate transfer parameters assumed as sources with known heat power are connected to airflow rate in different airways segments. Relationships expressing warming rate of inspired air due to convection, warming rate of inspired air due to evaporation, water diffused in the inspired air from the airways wall, i.e. a system of air conditioning parameters, was composed. The altitude dynamics of the relations is studied. Every rate conditioning parameter is an increasing function of altitude. The process of diffusion in the peripheral bronchial generations as a basic transfer process is analysed. The following phenomenon is in effect: the diffusion coefficient increases with altitude and causes a compensation of simultaneous decreasing of O(2)and CO(2)densities in atmospheric air. Due to this compensation, the diffusion in the peripheral generations with altitude is approximately constant. The elements of the human anatomy optimality as well as the established dynamics are discussed and assumed. The square form of the airways after the trachea expressed in terms of transfer supposes (in view of maximum contact surface), that a maximum heat and water exchange is achieved, i.e. high degree of air condition at fixed environmental parameters and respiration regime.

Altitude↗
PubMed1998

Origin of cadmium and lead in clear softwater lakes of high-altitude and high-latitude, and their bioavailability and toxicity to fish.

As a consequence of atmospheric deposition, effects of pollutants such as acidification and metal contamination are evident even in remote aquatic ecosystems of mountain and polar regions. Due to similar environmental characteristics (e.g., oligotrophy, low buffering capacity, long ice-cover, high precipitation rates), clearwater high altitude and high latitude lakes represent very sensitive ecosystems, which are extremely susceptible to even slight changes of the environment. Thus, the environmental relevance of Cd and Pb for both types of lakes is discussed in relation to their extraordinary sensitivity to environmental changes. The impact of Cd and Pb on fish from high altitude and high latitude lakes is reviewed and biotic and abiotic factors controlling bioavailability and toxicity of metals to fish are summarized. Apart from direct toxic effects of low pH, acidification increases the bioavailability of metals for fish. Furthermore, low concentrations of dissolved organic carbon and suspended particles take influence on the uptake and toxicity of metals in fish from clear high altitude and high latitude lakes. Since even very low concentrations of Cd and Pb may result in high metal concentrations in fish, evaluation of critical metal loads for clear high altitude and high latitude lakes is of major importance.

Altitude↗
PubMed1989

[Strategies of adaptation of oxygen transport systems in mammals to life at high altitude].

Like many mammalian species, man responds to exposure to high altitude with an increasing hemoglobin concentration and a decreasing blood O2-affinity. The Lama vicugna of the Andes does not show this kind of adaptation to altitude. Even at high altitude its hematocrit is unusually low and its O2-affinity is the highest known among mammals. Additionally, it is characterized by a high capillary density of the muscles and a large relative heart weight. The consequences of these different strategies of altitude adaptation of the oxygen supply system and the capability for physical performance are discussed.

Adaptation, Physiological↗
PubMed1980

Influence of exposure to moderate altitude on the plasma concentraton of cortisol, aldosterone, renin, testosterone, and gonadotropins.

The influence of 11 days at moderate altitude (2,000 m) combined with exercise on plasma concentration of testosterone, FSH (follicle-stimulating hormone), LH (luteinizing hormone), cortisol, aldosterone, and renin activity was studied in ten healthy subjects. Within 48 h of arrival at moderate altitude a significant increase in testosterone was found whereas FSH had decreased significantly and LH showed a tendency to decrease. Cortisol increased significantly at the beginning and reached a maximum at the end of altitude exposure. The plasma aldosterone level rose continuously and on the last day of altitude was significantly elevated. Plasma renin activity showed a tendency to decrease. On return to low land all measured parameters returned to base line values within 2 days. The findings of increases in plasma levels of aldosterone and testosterone (and serum T3 and T4, as reported by others) are in contrast to the previously found decrease of urinary excretion of all these hormones. This appears to be a distinct dissociation of serum levels of adrenal (and thyroid) hormones from their urinary excretion. The observed increase in plasma aldosterone is probably mediated through ACTH and the rise in plasma potassium, since plasma renin activity showed an opposite trend. The rise in plasma testosterone is probably of adrenal origin since plasma gonadotropins declined simultaneously. The increase of plasma levels of glucocorticoids, mineralocorticoids, and androgens after an ascent from 600 m to 2,000 m above sea level is compatible with an ACTH-mediated stimulation of the entire adrenal cortex and/or a diminished elimination of adrenal steroids: The concomitant fall of FSH, LH, and plasma renin would then be a consequence of a direct negative feedback inhibition of these hormones.

Adaptation, Physiological↗