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PubMed1993

Body composition and maximum alactic anaerobic performance during a one month stay at high altitude.

Prolonged altitude exposure usually leads to considerable weight loss of which a large part is from muscle tissue. This loss reduces maximum alactic anaerobic muscle power. It was hypothesized that most of the weight loss may simply be the result of malnutrition due to lack of palatable food in an uncomfortable environment. To test this hypothesis eight healthy male subjects (age 33.7 +/- 4.6 S.C. yr), well acclimatized to prevent symptoms of acute mountain sickness, were exposed for 4 weeks to an altitude of 5050 m with access to a large choice of palatable food in comfortable conditions. Body weight (with a scale), body composition (from skinfolds), arm muscle plus bone cross-sectional area (Am + b) and muscle plus bone leg volume (Vm+b) (from skinfolds and circumferences), maximum voluntary contraction force of the elbow flexors (MVC, with a load cell) and maximum jumping height (Hmax, on a platform) were measured before departure (SL) and in the first (ALT1), second (ALT2) and fourth week (ALT4) of their altitude sojourn. Three-day dietary records were obtained at SL and at ALT4. Body mass had decreased significantly at ALT2 (-3.8%) and at ALT4 (-4.6%) likely reflecting changes in body water homeostasis. No changes were found in %fat, Am+b, Vm+b, MVC or Hmax. Average dietary intake at SL was 8.96 +/- 1.45 MJ and had increased to 13.59 +/- 3.07 MJ at ALT4. In conclusion, up to an altitude of 5050 m loss of body mass from fat and muscle tissue, and hence impairment of maximum anaerobic muscle power (alactic) appears to be avoidable by food intake matched to energy expenditure. The latter may be achieved simply by proper acclimatization, sufficient comfort and availability of palatable food.

Adipose Tissue↗
PubMed1992

Salt and water control at altitude.

The physiological effect of altitude hypoxia, in the absence of exercise, is a sodium and water diuresis with decrease in plasma and extra-cellular volumes. Plasma aldosterone concentrations (PAC) are reduced but plasma atrial natriuretic peptide (ANP) levels are modestly increased. Day-long exercise at low altitude has almost opposite effects on fluid balance. There is an anti-diuresis, sodium retention, expansion of the plasma and extra-cellular compartments, elevation of PAC and ANP. Subjects who develop acute mountain sickness (AMS) show a pathological response to hypoxia even before the development of symptoms. There is an anti-diuresis, sodium retention, increased plasma and extra-cellular volumes and increased PAC compared with subjects resistant to AMS. Plasma ANP tends to be elevated compared with sea level values but the relation of ANP levels to AMS is variable. In general therefore, the pathological response to altitude hypoxia parallels that of exercise at low altitude and is opposite to the physiological response. Both exercise and the pathological response predispose the subject to edema and are probably important in the genesis of AMS.

Acute Disease↗
PubMed1992

Treatment of high altitude diseases without drugs.

Treatments other than descent and supplemental oxygen are discussed in this short review. Exercise gives rise to physiologic responses which may enhance acute mountain sickness (AMS), high altitude cerebral edema (HACE) and high altitude pulmonary edema (HAPE). Therefore, physical rest can be considered the principle treatment for moderate AMS and it should always accompany any treatment of severe high altitude illnesses as long as descent is not possible. Therapy with a portable fabric hyperbaric chamber has a beneficial short-term effect in subjects with AMS, HACE and HAPE. However, treatment modalities using this device which result in long-term beneficial effects need yet to be established. New technical solutions practicable under field conditions at extreme altitude are required for the removal of CO2 from the bag. Expiratory positive airway pressure (EPAP) improves arterial oxygen saturation by 10-20% in subjects with HAPE in trials of 10 min duration. Clinical studies examining longterm effects are necessary, before EPAP can be recommended as initial emergency treatment of HAPE.

Acute Disease↗
PubMed1992

Anaerobic performance at altitude.

Anaerobic metabolism is usually evaluated by the determination of the anaerobic capacity and the maximal anaerobic mechanical external power (Wmax). Conflicting results are reported on anaerobic capacity evaluated by maximal oxygen deficit and debt, and maximal blood lactate concentration during acute or chronic hypoxia (acclimatized subjects). Data on muscle biopsies (lactate concentration, changes in ATP, phosphocreatine and glycogen stores, glycolytic enzyme activities) and the few studies on lactate flux give in most cases evidence of a non-alteration of the anaerobic capacity for altitudes up to 5,500 m. No differences are observed in Wmax measured at high altitudes up to 5,200 m during intense short-term exercises: (1) jumps on a force platform which is a good indicator of alactic Wmax, and (2) 7-10 s sprints (i.e. force-velocity test) which solicit alactic metabolism but also lactic pathway. For exercises of duration equal or more than 30 s (i.e. Wingate test), there are conflicting results because a lower participation of aerobic metabolism during this test at high altitude can interfere with anaerobic performance. In conclusion, we can admit that anaerobic performances are not altered by high altitudes up to 5,200 m if the length of exposure does not exceed 5 weeks. After this period, muscle mass begins to decrease.

Acclimatization↗
PubMed1992

Physical fitness of children resident at high altitude in Bolivia.

In 7-15-yr-old children living in La Paz (Bolivia, altitude 3,700 m) (HA): 1) Maximal oxygen consumption (VO2max) varies from 35 to 45 ml.min-1.kg-1 and maximal heart rate from 188 to 194 beats.min-1. These values are lower than those of their counterparts at low altitude (LA) by 10-20% and 10-15 b.min-1, respectively. 2) The anaerobic metabolism is not affected by chronic hypoxia if the nutritional conditions and pubertal development of HA and LA boys are the same. When related to percent of VO2max, submaximal O2 debts are similar at HA and LA. After supramaximal exercise, maximal O2 debts (45.7 +/- 2.7 vs 45.9 +/- 3.8 ml.kg-1) and blood lactate concentrations (7.6 +/- 0.6 vs 6.5 +/- 0.6 mmol.l-1) are also the same at HA and LA. No differences are observed between the 2 altitudes in ventilatory (60 vs 56% VO2max) and lactate (60 vs 65% VO2max) thresholds. The altitude of La Paz does not alter the anaerobic performance of a force-velocity test (from 6 to 10 W.kg-1) between the ages of 7 to 15 years but reduces by 14-17% the mean anaerobic power developed during a 30-s Wingate test. This decrease could be linked to a lower participation of glycolysis and aerobic metabolism at HA during this test. 3) Poor socio-economic and nutritional conditions do not modify the aerobic performance of boys living in La Paz but lead to lower maximal anaerobic power (from -17% to -25%) when compared with HA boys from a high socio-economic background.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Hypoxic ventilatory response of rats born at simulated altitude.

Steady-state ventilatory response to isocapnic hypoxia was measured in awake rats: a) resident at sea level (Control); b) born at sea level and acclimatized to a simulated altitude of 3500 m (Newcomers); c) born and raised for two generations at a simulated altitude of 3500 m (HA-II Generation). Arterial PO2, PCO2, and pH were measured at the same time as ventilation. Resting ventilation (mean +/- SE) on room air in Control, Newcomers, and HA-II Generation was 707 +/- 25, 811 +/- 28 and 878 +/- 21 ml.min-1.kg-1, respectively. The ratios of ventilations measured at PaO2 55 and 100 Torr were 1.61 for Control, 1.52 for Newcomers, and 1.60 for HA-II Generation and were not significantly different from one another. The ventilatory response to 5% CO2 in air was also similar in all three groups. After four days at sea level, ventilatory responses of HA-II Generation to normoxia or isocapnic hypoxia were the same as those of sea level control. We conclude that the HA-II Generation groups had ventilatory responses to hypoxia that did not differ from those of Newcomers acclimatized to the same altitude. Unlike man, rats that were born and raised at altitude for two generations did not show any "blunting" of the ventilatory response to hypoxia.

Altitude↗
PubMed1997

[High altitude retinopathy after Himalayan ascent].

BACKGROUND: Visual disturbances after high altitude exposure were first reported in 1969. Later, the term "High Altitude Retinal Hemorrhage-HARH" has been used for the ensuing retinal hemorrhages and vascular engorgement. CASE REPORT: A 31-year-old Caucasian male presented to our outpatient department 1 week after climbing Mt. Gosainthan in the Himalayas. He had spent 25 days without oxygen supply above 5000 meters, with a maximum of 8046 meters. He now complained of glare and decreased vision in twilight. Visual acuity was 20/25 OD and 20/20 OS. Ophthalmoscopy revealed intraretinal hemorrhages and tortuosity of dilated arterioles and venoles. After 6 weeks of gradual improvement, visual acuity was 20/20 OD and 20/16 OS with normal visual fields. DISCUSSION: The hypoxia at high altitude causes increased retinal blood flow and blood volume possibly via autoregulatory mechanisms. Furthermore, retinal venous pressure can be increased by extreme physical exertion and Valsalva maneuvers during mountain climbing. A hypoxic retinal capillary bed exposed to increased retinal venous pressure predisposes to intraretinal hemorrhage. Retinal changes include marked increase of retinal vessel diameter with tortuosity of arterioles and venoles and hyperemia or edema of the optic disc. The intra- or preretinal hemorrhages often spare the macular area. These patients do not experience debilitating symptoms unless vitreous hemorrhage occurs. This may be potentially hazardous when the patient is still in the high mountains. Clinically, all these retinal changes are reversible within weeks. To prevent high altitude retinopathy, ascending slowly and use of supplemental oxygen is recommended.

Adult↗
PubMedDate not supplied

Relationships between blood pressure, anthropometric characteristics and blood lipids in high- and low-altitude populations from Central Asia.

We studied the relationships between blood pressure, anthropometric characteristics and blood lipids in 72 low altitude (LA) Uighurs (600 m), 91 LA-Kirghizs (900 m), 117 medium altitude (MA) Kazakhs (2100 m) and 94 high altitude (HA) Kirghizs (3200 m). All subjects were male and had a similar age (p = ns, ANOVA; range for all 374 subjects: 18-66 yr). Body weight (Wt), body mass index (BM1) and the sum of four skinfolds (4SF) were significantly lower in HA-Kirghizs than the remaining groups (p < 0.0005, p < 0.0005 and p < 0.05 respectively, ANOVA). However, no difference was found in body fat distribution as detected by waist:hip circumference (WHR) and triceps:subscapular skinfold ratios (TSR; p = ns, ANOVA). Stage 1 hypertension was detected in 18% of LA-Uighurs, 2% of LA-Kirghizs, 4% of MA-Kazakhs and 1% of HA-Kirghizs; stage 2 hypertension was detected in 2% of LA-Uighurs and none of the remaining groups; no subject had stage 3 hypertension (The Joint National Committee on Prevention. Detection, Evaluation and Treatment of High Blood Pressure 1997). Blood cholesterol (CH) and triglycerides (TG) did not differ between groups (p = ns, ANOVA). The relationships between systolic (SBP) or diastolic (DBP) blood pressure and age, Wt, BMI, 4SF, WHR, TSR, CH and TG were independent from altitude (p = ns, ANCOVA). In the pooled sample (n = 374), age explained 1 and 3% of SBP (p < 0.05) and DBP (p < 0.005) variance respectively, Wt was the best predictor of SBP and DBP explaining 11 and 10% of their variance respectively (p < 0.0001) and CH explained 5% of DBP variance (p < 0.0001). In conclusion, hypertension is more frequent in LA- than MA- and HA-subjects from Central Asia. However, anthropometric characteristics and blood lipids do similarly contribute to explain blood pressure in these subjects.

Adolescent↗
PubMedDate not supplied

Growth in a population of Tibetan origin at high altitude.

The report describes height, weight and triceps skinfold measurement for 239 individuals from 5 to 22 and 30 to 39 years of age living in the rural Tibetan village of Mugu, Nepal (altitude 3800m). It compares this population with a high-altitude Andean Quechua population and another high-altitude Tibetan population. A delay in height and weight is manifested by the Mugu population. Mugu children are shorter and lighter than the high-altitude Quechua sample during childhood and the early teens, yet they eventually achieve similar adult heights and weights. Mugu males are shorter and lighter than another Tibetan male sample. The reasons for the contrasting growth patterns are not known precisely due to present lack of thorough nutritional, epidemiological and genetical studies from Mugu.

Adolescent↗
PubMedDate not supplied

Variations in body dimensions in relation to altitude among the Sherpas of the eastern Himalayas.

A biomedical study was undertaken on the Sherpas of Upper Khumbu (3500-4500m), Nepal, and their migrant counterparts in the lower altitudes (1000-1500m) of Kalimpong subdivision, Darjeeling district, West Bengal, to study the impact of altitude on human biological characteristics in this Himalayan population, following the basic design of the IBP/Human Adaptability Panel. The results of the anthropometric survey of the adults (234 males and 169 females) are presented here. The high-altitude Sherpas of both sexes have significantly higher values than their low-altitude counterparts for most of the length, breadth and girth measurements, weight, cormic index, weight/stature ratio, weight/(stature)2 ratio, chest/stature ratio, surface area and body fat.

Adipose Tissue↗
PubMedDate not supplied

Technical note: reference values of haematocrit in young people and relationship with altitude.

The purpose of this paper is to provide scientific basis for a unified standard reference value of haematocrit in young people in China. The reference values of haematocrit levels in healthy young people have been collected according to the Wintrobe methods; the relationship between the reference values of haematocrit in young people and altitude has been tested in this paper. It has been found that the reference value of haematocrit in young people increases when the altitude gradually increases, and such relationship is quite significant, The method of mathematical univariate regression analysis is used to deduce two regression equations: Y1 = 44.3 + 0.00357X +/- 3.7, and Y2 = 39.7+0.00318X +/- 2.6. If the altitude value of a s known, the particular area of China is known, the reference value of haematocrit in young people there can be calculated by means of the regression equations. Furhermore depending on the altitude, China can be divided into three districts: Qingzang District, Central District and Eastern District.

Adolescent↗
PubMedDate not supplied

Reference value of young people's erythrocyte sedimentation rate and altitude.

The purpose of this paper is to provide a scientific basis for a unified standard of the reference value of young people's erythrocyte sedimentation rate (ESR) in China. The reference values of healthy young people's ESR were collected according to the Wintrobe method, and the relationship between the reference value of young people's ESR and altitude was tested in this paper. It was found that the reference value of young people's ESR decreases when the altitude gradually increases, and the relationship is significant. The method of mathematical univariate regression analysis was used to deduce two regression equations: Y(1) = 10.92-0.00183X +/-2.59 and Y(2) = 18.58-0.00319X +/-4.37. If the altitude value of a particular area of China is known, the reference value of young people's ESR can be calculated by means of the regression equations. Furthermore, depending on the altitude, China can be divided into three districts: Qingzang, Central and Eastern districts.

Adolescent↗
PubMed2005

Ghrelin and leptin levels of sojourners and acclimatized lowlanders at high altitude.

The circulatory levels of two appetite regulatory hormones i.e. leptin and ghrelin were estimated in sojourners and acclimatized subjects to investigate their possible role in high altitude (HA) induced anorexia. A group of 30 lowlanders who had never visited HA were inducted to a height of 3600 m by air and after 48 h they were further taken to an altitude of 4300 m by road. Blood samples were collected after 48 h stay at 3600 m and again after 48 h and 7 days of stay at 4300 m during 0700-0730 h. There was a decrease in energy intake (850 kcal/day) of sojourners, which resulted in loss of body weight by 2.12 kg at HA. At an altitude of 4300 m there was a significant increase in leptin over basal levels (54.9%, p < 0.001) at 48 h that persisted even after 7 days of stay at this altitude. Ghrelin levels of sojourners decreased by more than 30% in comparison to basal values at 48 h of ascent to HA. Leptin levels of acclimatized lowlanders were also higher in comparison with control group (acclimatized group 7.6 + 0.6 ng/ml vs. control 5.6 + 0.5 ng/ml, p < 0.01, n = 50).

Acclimatization↗
PubMed2004

Effects of temperature, photoperiod, and light intensity on the eclosion rhythm of the high-altitude Himalayan strain of Drosophila ananassae.

Eclosion rhythm of the high-altitude Himalayan strain of Drosophila ananassae from Badrinath (altitude 5123 m) was temperature-dependent and at 21 degrees C, it was entrained by cycles of 12h light: 12h darkness (LD 12:12) and free-ran in constant darkness, however, it was arrhythmic at 13 degrees C or 17 degrees C under identical experimental conditions (Khare, P. V., Barnabas, R. J., Kanojiya, M., Kulkarni, A. D., Joshi, D. S. (2002). Temperature dependent eclosion rhythmicity in the high altitude Himalayan strains of Drosophila ananassae. Chronobiol. Int. 19:1041-1052). The present studies were designed to see whether or not these strains could be entrained at 13 degrees C, 17 degrees C, and 21 degrees C by two types of LD cycles in which the photoperiod at 100 lux intensity varied from 6h to 18h, and the light intensity of LD 14:10 cycles varied from 0.001 lux to 1000 lux. All LD cycles entrained this strain at 21 degrees C but not at 13 degrees C or 17 degrees C. These results demonstrate that the entrainment of eclosion rhythm depends on the ambient temperature and not on the photoperiod or light intensity of LD cycles. Thus the temperature has taken precedence over the light in the entrainment process of eclosion rhythm of the high altitude Himalayan strain of D. ananassae. This may be the result of natural selection in response to the environmental temperature at Badrinath that resembles that of the sub-Arctic region but the photoperiod or light intensity are of the subtropical region.

Altitude↗
PubMed2001

Postural instability and acute mountain sickness during exposure to 24 hours of simulated altitude (4300 m).

Short exposures to severe or moderate hypoxia can have detrimental effects on postural stability. We hypothesized that continuous 24-h exposure to simulated 4300-m altitude (446 mmHg) would adversely affect postural stability and that this change in postural stability would be related to the severity of acute mountain sickness (AMS). On two different studies with similar experimental designs, postural instability was measured after approximately 3 and approximately 24 h of exposure using a computer-controlled unstable platform system in a total of 19 volunteers on three consecutive, 30-sec tests: eyes open (EO), eyes closed (EC), and a dynamic test involving tracking a circular moving object. Compared to baseline sea-level results, increases in postural instability were obtained with the EO test after 2 to 3 h (30%, p = 0.002) and 23 to 24 h (21%, p = 0.036) of altitude exposure. Similar increases were obtained on the EC test: 2 to 3 h (25%, p < 0.001) and 23 to 24 h (31%, p < 0.001). Although absolute instability values were higher on the EC test, the ratio EC/EO and the relative temporal changes with altitude exposure were similar. There were no significant altitude-stability effects on the target-tracking task. Sixty-three percent of the subjects (12 of 19) exhibited significant AMS (> 0.7 ESQ-C score) at some point during the 24-h exposure. No statistically significant correlations were obtained between the ESQ-C and any of the postural instability tests. These results indicate that postural stability is adversely affected during a 24-h exposure to 4300 m; however, there does not appear to be a correlation with the incidence or severity of AMS.

Adolescent↗
PubMed2002

Transient minor improvement of high altitude headache by sumatriptan.

High-altitude headache often fulfills the criteria of migraine. Therefore, we hypothesized that sumatriptan, a 5-HT1 receptor agonist specifically effective for treatment of migraine, would also alleviate high altitude headache. A randomized, placebo-controlled double-blind trial was performed on 29 mountaineers with at least moderate headache on the day of arrival at 4559 m. Fourteen subjects received 100 mg sumatriptan orally and 15 subjects received placebo. Before treatment there were no significant differences between groups regarding rate of ascent, duration and severity of headache, and acute mountain sickness score. All 6 female subjects were randomly assigned to placebo. Absolute values and the reduction of headache scores 1, 3, and 12 h after the administration of sumatriptan did not differ between treatment groups, but headache scores tended to be lower with sumatriptan after 1 or 3 h when compared with placebo. Considering only male mountaineers, there was a significant decrease of headache scores after 1 and 3 h. Because there was only a minor transient amelioration of high altitude headache with sumatriptan, we conclude that 5-HT1 receptors do not play a major role in the pathophysiology of high altitude headache.

Adult↗
PubMed2003

Beta-blockers may provoke oxygen desaturation during submaximal exercise at moderate altitudes in elderly persons.

Frequency of therapeutic beta-blocker use in elderly mountaineers is unknown. Therefore, the aim of this field study was to measure the regular beta-blocker intake in elderly persons visiting moderate altitudes. In a subset of mountaineers on beta-blockers, exercise response at two different altitude levels was compared to matched controls. The observed frequency of beta-blocked persons among the interviewed elderly mountaineers (age >35) was 7%, mainly (65%) due to hypertension. In subjects taking beta-blockers, arterial oxygen saturation (84 +/- 6% vs. 90 +/- 3%, p < 0.05) was decreased and heart rate (120 +/- 17 bpm vs. 112 +/- 14 bpm, p = 0.01), rate pressure product (22,192 +/- 6459 vs. 17,576 +/- 4010, p < 0.05), and ratings of perceived exertion (14 +/- 3 vs. 12 +/- 3, p < 0.05) were increased during a submaximal step test at 2311 m compared to 1480 m. Mountaineers without beta-blocker intake showed no changes. Although the epidemiological data have to be interpreted with caution because of the small sample size and the limitation to a single geographical site, a large number of beta-blocked persons visiting high altitudes was observed. If confirmed in further studies, the increased heart work and exertion could indicate a reduced exercise tolerance of people taking beta-blockers during acute high altitude exposure.

Adrenergic beta-Antagonists↗
PubMed2004

High altitude cerebral edema.

This review focuses on the epidemiology, clinical description, pathophysiology, treatment, and prevention of high altitude cerebral edema (HACE). HACE is an uncommon and sometimes fatal complication of traveling too high, too fast to high altitudes. HACE is distinguished by disturbances of consciousness that may progress to deep coma, psychiatric changes of varying degree, confusion, and ataxia of gait. It is most often a complication of acute mountain sickness or high altitude pulmonary edema. The current leading theory of its pathophysiology is that HACE is a vasogenic edema; that is, a disruption of the blood-brain barrier, and we review possible mechanisms to explain this. Treatment and prevention of HACE are similar to those for the other altitude illnesses, but with greater emphasis on descent and steroids. We conclude the review with several case histories to illustrate key clinical features of the disorder.

Acetazolamide↗