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PubMed1998

Increase in serum vascular endothelial growth factor levels during altitude training.

The present study was performed to evaluate the effects of physical exercise at altitudes on serum vascular endothelial growth factor (VEGF) levels. Eight subjects underwent intensive swimming training for 21 days at 1886 m. After altitude training commenced, red blood cell (RBC) counts and erythropoietin levels increased, but both haemoglobin and haematocrit levels did not change significantly. The serum level of VEGF, measured by means of a highly sensitive chemiluminescence (ELISA), showed a transient decrease 10 days after start of the altitude training, thereafter increasing significantly to reach a peak level 19 days later, rising from 23.0 +/- 5.3 to 46.0 +/- 14.6 pg mL-1 (P < 0.05 vs. before). On return to low altitude in Japan, the level of VEGF decreased, and 1 month later had returned to initial levels. Endurance training at altitudes increases serum VEGF levels; this could be an adaptive reaction to hypoxic conditions. This result suggests that VEGF may provide a new physiological parameter for hypoxic stress imposed by high altitude training.

Adult↗
PubMed2002

Hyperuricemia, hypertension, and proteinuria associated with high-altitude polycythemia.

Chronic exposure to high altitude is associated with the development of erythrocytosis, proteinuria, and, in some cases, hyperuricemia. We examined the relationship between high-altitude polycythemia and proteinuria and hyperuricemia in Cerro de Pasco, Peru (altitude, 4,300 m). We studied 25 adult men with hematocrits less than 65% and 27 subjects with excessive erythrocytosis (EE; hematocrit > 65%) living in Cerro de Pasco, Peru and compared them with 28 control subjects living in Lima, Peru (at sea level) and after 48 hours of exposure to high altitude. Serum urate levels were significantly elevated in patients with EE at altitude, and gout occurred in 4 of 27 of these subjects. Urate level strongly correlated with hematocrit (r = 0.71; P < 0.0001). Urate production (24-hour urine urate excretion and urine urate-creatinine ratio) was increased in this group compared with those at sea level. Fractional urate excretion was not increased, and fractional lithium excretion was reduced, in keeping with increased proximal reabsorption of filtrate. Significantly higher blood pressures and decreased renin levels in the EE group were in keeping with increased proximal sodium reabsorption. Serum urate levels correlated with mean blood pressure (r = 0.50; P < 0.0001). Significant proteinuria was more prevalent in the EE group despite normal renal function. Hyperuricemia is common in subjects living at high altitude and associated with EE, hypertension, and proteinuria. The increase in uric acid levels appears to be caused by increased urate generation secondary to systemic hypoxia, although a relative impairment in renal excretion also may contribute.

Adult↗
PubMedDate not supplied

Changes in fetal capillaries during preplacental hypoxia: growth, shape remodelling and villous capillarization in placentae from high-altitude pregnancies.

Patterns of fetoplacental angiogenesis and villous growth vary in pregnancies complicated by different forms of fetal hypoxia. This study uses stereological estimators to examine absolute and relative dimensions of villi and fetal capillaries in cases of preplacental hypoxia due to pregnancy at high altitude. Placental samples were drawn from well-defined subjects in different ethnic groups born, raised and completing term pregnancies at low (500 m) and high altitude (3600 m above sea level). Volumes, surfaces and lengths were used to monitor the nett growth of villi and capillaries. Indices of villous capillarization comprised volume, surface and length densities and capillary:villus surface and length ratios. Villus/capillary 'calibre' and shape were quantified using cross-sectional areas, perimeters and shape coefficients (perimeter(2)/area). Group comparisons were drawn by two-way analyses of variance with altitude and ethnicity as the main factors. Volumes, surfaces and lengths of villi, and volumes of capillaries, were reduced at high altitude. Capillary volume declined primarily by formation of narrower microvessels which were more irregular in outline. There were no differences in capillary surface area or length. Cross-sectional sizes and shapes of villi were unaltered. Differences in villous capillarization were confined to higher surface and length densities. Ethnic differences in villous length, capillary length and cross-sectional area tended to favour native groups who are pre-adapted to life at high altitude. Results show that high-altitude pregnancy is not accompanied by increased angiogenesis but may involve enhanced villous capillarization and vascular shape remodelling. Comparisons are drawn with changes seen in maternal anaemia. It is concluded that absolute and relative measures of villous and capillary growth are required lest misinterpretations are introduced by equating hypercapillarization with enhanced angiogenesis or the pattern of capillary branching. The importance of controlling for various potential confounders is also emphasized.

Adaptation, Physiological↗
PubMed2000

Maternal serum alpha-fetoprotein and altitude.

Maternal serum alpha-fetoprotein (MS-alphaFP) testing is widely used to screen for fetal defects. MS-alphaFP concentrations are affected by a number of variables such as gestational age, maternal weight, number of fetuses, race, and insulin-dependent diabetes. Undefined geographic factors may also influence MS-alphaFP. We have examined the effect of altitude in a sample of 1063 MS-alphaFP results selected to span a range of altitudes. The study sample was subjected to linear regression with and without a term for altitude, and multiple-of-the-median (MoM) values were calculated before and after adjusting for altitude. The median MS-alphaFP was found to decrease an average of 1 ng/mL for every 1100 ft increase in altitude, a change approximately equivalent to that seen with an increase in maternal weight of 6 lb. Adjusting for altitude resulted in the reclassification of 36 of 1063 patient results (3.4%), although the clinical utility of this adjustment remains unexamined.

Altitude↗
PubMed1991

Thyroid function in sojourners and acclimatised low landers at high altitude in man.

The circulatory levels of T4, T3, rT3, TSH as well as TSH response to TRH, thyroid hormone binding proteins and T3 concentration of erythrocytes were studied in (i) healthy euthyroid sea level residents (SLR) at sea level, (ii) during three weeks of stay of SLR at an altitude of 3500 m (sojourners, SJ), (iii) SLR staying at high altitude (HA) for 3 months to 10 years (acclimatised low landers. ALL), (iv) high altitude natives (HAN) and (v) euthyroid men during intermittent exposure to simulated altitude of 3500 m in a hypobaric chamber maintained at an ambient temperature of 22 degrees C to 24 degrees C. Hypoxic stress either simulated or natural, produced marked elevation in plasma T4 and T3 within 4 h and the increased levels were maintained during the entire period of exposure. The circulatory levels of T4 and T3 were higher in HAN and ALL compared to SLR values. The T3 concentration of erythrocytes was decreased (P less than 0.01) at HA, whereas plasma rT3, TBG and T4 binding capacities of TBG and TBPA did not show any appreciable change. Plasma TSH at high altitude in SJ, ALL and HAN was not significantly different from the SLR values. Furthermore, when L-eltroxine treated (L-T4, 0.5 mg/d for 11 days) euthyroid men were subjected to simulated altitude, there was an elevation in both T4 and T3 suggesting that the rise in hormone levels was independent of pituitary secretion of thyrotropin. Both T4 and T3 returned to SLR values when SJ and HAN were brought down to SL.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1988

Psychopathology in mountaineering--mental disturbances under high-altitude stress.

In the years 1960-1985 psychiatric and psychological research was conducted among a group of 80 Polish alpinists. Experimental research was conducted during the expeditions to the Hindu Kush mountains and to the Andes (1971, 1973-74, 1979, 1985). The aim of the research was to describe the personality of the alpinists, their motivation, as well as mental disturbances caused by staying at high altitudes. On the basis of an interview and the Cattell personality questionnaire, two types of personality were distinguished: the schizoid-psychasthenic type (53 persons, i.e. 66%) and the asthenic-neurotic type (23 persons, i.e. 30%). As regards the motivation for mountain climbing, situational and personality factors were described, among them, the need to experience "powerful situations" and compensating for an inferiority complex. A so called integrational fear which mobilizes the psychophysical capabilities to overcome the hardships of the climb, was described as characteristic of the alpinists. Depending on the altitude and the duration of one's stay at it, the mental disturbances, in most cases took on the form of the neurasthenic syndrome (asthenic or sthenic) at low altitudes (3000-4000 m), the cyclothymic syndrome at medium altitudes (4000-5000 m), and the acute organic brain syndrome at high altitudes (above 7000 m). In 24 (35%) cases, there occurred psychotic disturbances with profound disturbances of consciousness and orientation. These states were accompanied by symptoms of high-altitude deterioration with a break-down in the physical condition, disturbances in the hydro-electrolyte equilibrium, and a considerable loss of bodily weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1998

Cough induced stress fracture and arthropathy of the ribs at extreme altitude.

Cough and chest wall pain at high altitude have only received passing mention in the medical literature. Increased minute ventilation of cold dry air at very high altitude is likely to cause airway irritation. This in turn may result in airway drying, mucus production, postnasal drip from vasomotor rhinitis, and bronchospasm acting individually or in combination to stimulate the vagal cough reflex. The cough is exacerbated further at extreme altitudes above 5500 m, and may result in intercostal muscle strain and single or multiple rib fractures. We present a case of multiple cough induced stress fractures and arthropathy documented by technetium-99 bone scan in a high altitude climber and suggest the addition of the term High Altitude Cough Syndrome (HACS) to the medical syntax to identify this discrete medical problem of exposure to very high altitude.

Adult↗
PubMed1997

After-effects of a high altitude expedition on blood.

The aim of the study was to investigate blood alterations caused by altitude acclimatization which last more than few days after return and might play a role for exercise performance at sea level. Measurements were performed in 12 mountaineers before, during and either 7/8 or 11/12 days after a Himalaya expedition (26-29 days at 4900 to 7600 m altitude). [Erythropoietin] rose only temporarily at altitude (max. +11 +/- 1 [SE] mu/ml serum). After return hemoglobin mass (initially 881 +/- 44 g, CO-Hb method) was increased by 14% (p < 0.01); aspartate aminotransferase activity in erythrocytes (initially 682 +/- 25 U/l) was augmented (day 7: +964 +/- 152 U/l, day 11: +533 +/- 107 U/l) indicating reduced mean cell age. Calculated blood volume (+14%) was influenced by red cell formation at altitude but also by plasma expansion at sea level. The half saturation pressure for Hb-O2 (pH 7.4, 37 degrees C) as well as the 2.3-diphosphoglycerate concentration were already initially high (32.1 +/- 0.5 mmHg, 20.5 +/- 0.7 mumol/g Hb) and showed only a nonsignificant tendency to increase after return. Also Hill's n was consistently high in the mountaineers, whereas the Bohr coefficients were slightly increased only after descent. Probably the preparatory physical training, partly in the Alps, and the stay in the Himalaya influenced O2-affinity for a prolonged time. The adaptations might reduce the loss of physical performance capacity at altitude and be part of altitude training effects.

Acid-Base Equilibrium↗
PubMed1977

Reduction in mortality from coronary heart disease in men residing at high altitude.

In New Mexico, where inhabited areas vary from 914 to over 2135 m above sea level, we compared age-adjusted mortality rates for arteriosclerotic heart disease for white men and women for the years 1957-1970 in five sets of counties, grouped by altitude in 305-m (1000-foot) increments. The results show a serial decline in mortality from the lowest to the highest altitude for males but not for females. Mortality rates for males residing in the county groups higher than 1220 m in order of ascending altitude were 98, 90, 86 and 72 per cent of that for the county group below 1220-m altitude (P less than 0.0001). The results do not appear to be explained by artifacts in ascertainment, variations in ethnicity or urbanization. A possible explanation of the trend is that adjustment to residence at high altitude is incomplete and daily activities therefore represent greater exercise than when undertaken at lower altitudes.

Acclimatization↗
PubMed1975

High altitude stress and retinal hemorrhage: relation to vascular headache mechanisms.

Retinal hemorrhage occurred in 36% of 39 subjects exposed to altitudes at or above 14,200 feet. In subjects with a history of vascular headaches at sea level, there was a higher incidence of and more severe altitude headache, as well as a higher incidence of retinal hemorrhage than among those previously headache-free. In subjects without altitude headache, none had retinal hemorrhage. In subjects with altitude headache, 42% had retinal hemorrhage. A progressive rise in the incidence of retinal hemorrhage was correlated with progressively greater intensity of altitude headache. Factors that intensified the rate or degree of exposure, including rapid ascent and strenuous exertion, appeared to increase the likelihood of hemorrhage. An optimal balance between acclimatization and subsequent altitude stress appeared to prevent retinal hemorrhage. Increased retinal blood flow, retinal vessel engorgement, increased retinal vein and prevenous capillary pressure, and possibly decreased intraocular pressure may contribute to the pathogenesis of retinal hemorrhage.

Acclimatization↗
PubMedDate not supplied

Altitude and mortality from chronic obstructive lung disease in New Mexico.

This study tested the hypothesis that altitude increases mortality from chronic obstructive lung disease (COLD) in New Mexico. A death was attributed to COLD if it resulted from chronic bronchitis, emphysema, or chronic obstructive lung disease, according to the Eighth Revision International Classification of Diseases, Adapted for Use in the United States. New Mexico's average annual ethnic and sex-specific mortality rates from COLD were calculated using death certificate data for the period 1969 to 1977. Deaths were assigned to altitude groups according to the county of residence at the time of death. Mortality rates for whites exceeded nationwide rates at all altitudes. However, mortality rates showed no increase with altitude. In fact, mortality from COLD decreased significantly with altitude for non-Hispanic white (Anglo) males (P less than .02). Immigration of Anglos to the lower altitudes of New Mexico probably explains these results.

Altitude↗
PubMedDate not supplied

Acute mountain sickness and physiological stress during intermittent exposure to high altitude.

The effect of intermittent exposure to high altitude (4200 m) hypoxia on symptomatology of acute mountain sickness (AMS) was observed, and the relationship between AMS and stress hormone excretion was examined among shift workers at the United Kingdom Infrared Telescope (UKIRT) facility and a control group of sea level residents. Some of the shift workers experienced AMS during their first day at altitude, but had recovered after 5 days residence at altitude. Upon acute exposure to altitude, none of the shift workers reported severe cases of AMS after 5 days residence at sea level, but some reported severe cases after 45 residence at sea level, thus providing some evidence for a 'carry over' of acclimatization for a 5 day period. Reported symptomatology at sea level was predictive of 24 h. excretion rates of adrenaline and 17-hydroxycorticosteroids at high altitude. No good predictors of symptomatology of AMS at high altitude were found using sea level measures alone.

17-Hydroxycorticosteroids↗
PubMedDate not supplied

Respiratory adaptation to high altitude in adolescent Bod girls of the Western Himalayas.

The impact of high-altitude environment was studied on respiratory functions and body measurements in adolescent Bod girls of Ladakh, Jammu and Kashmir, India. Data were collected on 133 high-altitude and 141 low-altitude Bod girls in the age range 12-18 years. Lung functions were, age to age, higher in high-altitude girls than their coeval lowlanders. This has been explained as an adaptation to the stress of low atmospheric pressure at high altitude. This response is similar to the one observed in growing Bod boys living in the same area (Malik and Singh 1979, 1984). High-altitude girls were shorter and lighter, the difference was more pronounced in weight and especially after 14 years of age.

Adaptation, Physiological↗
PubMed1982

Ethanol and hypobarometric simulated high altitude: a gonadal-hepatic toxicity study in the male rat.

Male rats were maintained on water or on 10% ethanol drinking fluid. They were pairfed for 30 d prior to exposure to simulated high altitude (approximately 6000 m) and for 78 d, during which they were exposed to simulated high altitude on alternate days. Corresponding controls were maintained at ambient pressure. The high-altitude animals showed loss in liver and epididymis weights compared to respective water controls as contrasted with increased spleen weight in ethanol-drinking rats exposed to high altitude. Hepatic mitochondrial aldehyde dehydrogenase (ALDH) was decreased, compared to controls, by hypobarometric pressure in water-drinking animals. Ethanol intake negated this effect. The kinetics of this inhibition show changes in Vmax without concomitant changes in the apparent Km. Hepatic alcohol dehydrogenase did not change by either treatment. Testicular and epididymal ALDH showed, statistically, no significant changes in specific activity as a function of exposure to high altitude. However, combined ethanol drinking and altitude exposure increased epididymal ALDH compared to water-drinking rats subjected to the same experimental conditions. The changes in liver and testicular weight and in the enzyme involved in the biotransformation of ethanol-derived acetaldehyde suggest the contribution of endocrinological and biochemical factors to hypoxia and to ethanol-evoked adverse responses studied.

Aldehyde Dehydrogenase↗
PubMed2001

Infections at high altitude.

Every year, thousands of outdoor trekkers worldwide visit high-altitude (>2500 m) destinations. Although high-altitude areas per se do not harbor any specific agents, it is important to know the pathogens encountered in the mountains to be better able to help the ill sojourner at high altitude. These are the same pathogens prevalent in the surrounding lowlands, but various factors such as immunomodulation, hypoxia, physiological adaptation, and harsh environmental stressors at high altitude may enhance susceptibility to these pathogens. Against this background, various gastrointestinal, respiratory, dermatological, neurological, and other infections encountered at high altitude are discussed. Because there are few published data on infections at high altitude, this review is largely anecdotal and based on personal experience.

Altitude↗
PubMed2000

Does hypoxia impair ovarian function in Bolivian women indigenous to high altitude?

Fertility appears to be reduced in at least some high altitude populations relative to their counterparts at lower elevations. Inferring from the difficulties with reproduction of newcomers to high altitude and from animal experiments, it has been hypothesized that this apparent reduction is the result of hypoxia acting to reduce fecundity and/or increase fetal loss. In humans, however, several behavioral as well as biological factors may affect fertility levels. These many factors have been organized by demographers into a framework of seven proximate determinants that includes fecundability (the monthly probability of conception) of which successful ovulation is one component. To test whether ovarian function is impaired in women indigenous to high altitude, we measured salivary progesterone (P) in a sample (n = 20) of Quechua women (aged 19-42 years) residing at 3,100 m. It was found that mean luteal P = 179 pmol/L and mean midluteal P = 243 pmol/L, levels that fall about midway in the range of known values for several populations and are higher than some lower altitude populations. These findings suggest that hypoxia does not appear to significantly impair ovarian function in those with lifelong residence at high altitude. There are, however, several factors common to many high altitude populations that may act to reduce fecundability and fertility including intercourse patterns (affected by marriage and migration practices), prolonged lactation, dietary insufficiency, and hard labor.

Adult↗
PubMed2000

Acute medical problems in the Himalayas outside the setting of altitude sickness.

Well-recognized medical threats at high altitude (>2,500 m) include acute mountain sickness (AMS), high altitude pulmonary edema (HAPE), and high altitude cerebral edema (HACE). Thousands of travelers in the Himalayas are exposed annually to these often life-threatening syndromes. Their recognition and treatment has advanced considerably in recent years. In the Himalayas, we frequently see acute medical problems outside the setting of AMS and the two types of altitude edemas. Many of these other conditions are also hypoxia related and sometimes may mimic the classic high altitude illnesses of AMS, HAPE, and HACE. Although the vast majority of these medical problems are neurological, pulmonary and other organ system dysfunction also occur. These "non-high altitude sickness" disease entities in persons who sojourn to remote mountainous environments are reviewed in this paper to enhance their recognition, diagnosis, and treatment.

Acute Disease↗
PubMed2001

Role of vascular smooth muscle in the development of high altitude pulmonary hypertension: an interspecies evaluation.

There is a marked variability in the degree of pulmonary hypertension induced by long-term exposure to altitudes above 3000 m among low altitude species, ranging from hyporesponders (sheep and dogs) to hyper-responders (cattle and pigs). The amount of inherent muscularization of small pulmonary arteries appears to be a determinant of this hypertensive response, as does the presence or absence of collateral ventilation. Hyper-responders also exhibit marked pulmonary vascular hypertrophy when exposed to long-term hypoxia. Humans exhibit similar inter- and intra-population variability. Animal species indigenous to high altitudes exhibit less variable, attenuated pulmonary hypertensive responses with little pulmonary vascular hypertrophy. This attenuated response is also apparent among human high altitude populations, particularly in Andean and Tibetan populations. Thus, successful adaptation to high altitudes is evident in species that do not sustain the acute cardiopulmonary compensations that occur upon initial exposure to high altitude.

Altitude↗