The lung at high altitude

Men and mammals (excluding the indigenous mountain species) who are born at high altitude, or who ascend to live there for a long period, have to undergo acclimatization which affects virtually every system in the body. Since chronic hypoxia is the most important adverse factor in the mountain environment, the lung plays a major part in the process and shows many alterations in structure and function. However, we remain ignorant about many aspects of acclimatization of the lung to hypoxia especially at the ultrastructural level with respect to those cells whose normal function is not yet established. An account of what is known is given in this paper.     

The athlete at high altitude

Track times at moderate altitudes (7000 to 8000 feet) are modified by decreased wind resistance and by systemic disturbances such as mountain sickness, disruption of training, and a decrease of maximum oxygen intake. The optimum period of acclimatization is probably two to three days. This permits adjustment of cerebrospinal fluid acid-base balance, but minimizes disturbances of plasma volume and stroke volume. Further study is needed to establish whether altitude training can improve performance in sea-level competitions.     

The effect of altitude and cold on body temperature during acclimatization of man at 3,300 m

The oral temperature of 20 healthy subjects of 22–28 years of age at sea level (Delhi) was recorded between 08:00–09:00 hr daily for a period of one week. Then they were flown to an altitude of 3,300 m where they were divided into two equal groups. One group was exposed to hypoxia and cold (6° to 11°C) simultaneously, while the other group to only hypoxia (25° to 28°C). At the end of three weeks, the groups were interchanged and studied for a further period of three weeks, after which they were flown back and re-tested at sea level for another week. The chronic hypoxia existing at this altitude produced a significant fall in body temperature irrespective of imposition or withdrawal of cold stress.

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Zusammenfassung Die Mundtemperatur von 20 gesunden Personen (22–28 Jahre alt) wurde auf Seehöhe (Delhi) täglich zwischen 08:00–09:00 hr morgens während einer Woche gemessen. Danach wurden die 20 Personen auf 3.300 m Höhe geflogen und davon 10 Personen 3 Wochen bei 25° bis 28°C und 10 bei 6° bis 11°C exponiert. Nach 3 Wochen wurden die Gruppen aus der Wärme in die Kälte und umgekehrt ausgetauscht. Nach 6 Wochen wurden alle Personen ins Tiefland zurückgeflogen und eine weitere Woche lang beobachtet. Die chronische Hypoxie in dieser Höhe führte mit und ohne Kältebelastung zu einer signifikanten Senkung der Körpertemperatur.

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Resume Pendant une semaine, on a mesuré tous les jours entre 8 et 9 heures du matin la température bucale de 20 personnes en bonne santé âgées de 22 à 29 ans. Ceci a eu lieu à Dehli, c'est-à-dire au niveau de la mer. Ces 20 individus ont été ensuite transportés par avion à 3.300 m d'altitude. 10 d'entre eux furent alors soumis à des températures de 25° à 28°C, les 10 autres à des températures de 6° à 11°C. Après 3 semaines de ce régime, on a interverti les 2 groupes. Après 3 nouvelles semaines de séjour en altitude, ces 20 personnes furent ramenées en plaine — également par avion — et soumises durant une semaine à de nouveaux examens. L'hypoxie chronique due à l'altitude a eu pour conséquence un abaissement de la température du corps, que celui-ci ait été soumis à une contrainte de froid ou non.

     

Hepatic amoebiasis at high altitude

Latent amoebiasis is aggravated at high altitude. Protean manifestations are common. Fever is usually absent. Liver tenderness is not a feature and may have to be specially elicited. Leucocytosis is rare. Bowel symptoms inspite of presence of intestinal ulcerations are usually absent. Response to treatment with emetine or chloroquin is unsatisfactory and relapse rate is high. These points may interest mountaineers and other sojourners to high altitude.     

The effect of high altitude on saliva aldosterone and glucocorticoid concentrations

Saliva was collected from six healthy young men at hourly intervals at sea level and after 1-2, 8-9 and 15-16 days at 4450 m on Mount Kenya for measurement of aldosterone (SA) and glucocorticoid (SGC, cortisol + cortisone) concentrations. Blood samples were collected simultaneously with some of the saliva samples and analysis of these showed that plasma and saliva concentrations of aldosterone and glucocorticoids were highly correlated (r = 0.91 and 0.75 respectively; p less than 0.01 for both hormones). Mean SA for the group was reduced to approximately 50% of the sea-level value (p less than 0.05) by the time the first saliva samples were collected at altitude, and remained at this depressed level throughout the 2-week period on Mount Kenya, although there was considerable inter-subject variation. SGC concentration also tended to be lower on Mount Kenya than at sea level. Though SA was lower throughout the day at altitude compared to sea level, the principal difference in the temporal pattern of SA was the reduction or complete absence of the marked rise in SA that normally occurs in the first few hours after rising. SA and SGC responses to exercise, which consisted of stepping on and off and 0.4-m high stool 60 times/min for 25 min, were assessed at sea level and after various periods at 4450 m.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of high altitude on age at menarche and menopause

The age at menarche and menopause of three groups of Bhotia females living at high altitude, Himalayan region — Uttar Pradesh, North India, were studied. The Johari Bhotia women had earliest menarche (¯X=15.1±1.1 years) as compared to Rang Bhotias, settled (¯X=15.6±0.9 years) and Rang Bhotias, migratory (¯X=16.0±1.0 years). The differences between all these three groups for age at menarche were significant. A trend towards increase in age at menarche with an increase in altitude has been observed, but the total fertility period in the three groups remained similar as early menarche has been found to be associated with early onset of menopause and late menarche with late menopause.     

液态氧在高原地区供氧效果的评价

目的:探讨高原单兵及车载液态氧供氧效果.方法:观察高原单兵速跑和乘车中液氧罐的供氧时间及血氧饱和度(SaO2)和脉搏(P)的变化.结果:1.5 L单兵罐可供1名士兵持续吸氧(2 L·min-1)8～10 h;15 L车载罐可供4人同时吸氧(2 L·min-1)25～27 h.海拔3 700 m和5 380 m携罐吸氧速跑后较常氧速跑后SaO2显著增加(P<0.01),海拔3 700～5 380 m吸氧乘车平均SaO2较常氧乘车显著增高(P<0.01).结论:液态氧在高原有较好的应用价值,速跑或乘车时吸氧可使SaO2增加.     

Cell mediated immunity at high altitude

Cell mediated immunity (CMI) was assessed by determining total and differential leucocyte and absolute lymphocyte counts, T and B-rosettes, PHA-blast transformation of lymphocytes, lymphocyte migration index (LMI), and DNCB response in 66 sea-level residents, 45 temporary residents, and 24 natives at high altitude (3,692 m). An accentuated CMI, indicated by increase in PHA-blasts, increased lymphocyte migration index, and intense DNCB response, was present, despite a mild decrease in total leucocytes in temporary residents and in lymphocytes in natives at high altitude. While T-rosettes did not show any change in numbers, B-rosettes were increased in temporary residents, and natives at high altitude. A qualitative change had, therefore, occurred in lymphocytes at high altitude. CMI is equally augmented in temporary residents and natives at high altitude and prevails at a higher plane than at sea-level. Augmentation of CMI at high altitude, therefore, could be used as a therapeutic measure.     

The physiology and biomechanics of avian flight at high altitude

Many birds fly at high altitude, either during long-distanceflights or by virtue of residence in high-elevation habitats.Among the many environmental features that vary systematicallywith altitude, five have significant consequences for avianflight performance: ambient wind speeds, air temperature, humidity,oxygen availability, and air density. During migratory flights,birds select flight altitudes that minimize energy expenditurevia selection of advantageous tail- and cross-winds. Oxygenpartial pressure decreases substantially to as little as 26%of sea-level values for the highest altitudes at which birdsmigrate, whereas many taxa reside above 3000 meters in hypoxicair. Birds exhibit numerous adaptations in pulmonary, cardiovascular,and muscular systems to alleviate such hypoxia. The systematicdecrease in air density with altitude can lead to a benefitfor forward flight through reduced drag but imposes an increasedaerodynamic demand for hovering by degrading lift productionand simultaneously elevating the induced power requirementsof flight. This effect has been well-studied in the hoveringflight of hummingbirds, which occur throughout high-elevationhabitats in the western hemisphere. Phylogenetically controlledstudies have shown that hummingbirds compensate morphologicallyfor such hypodense air through relative increases in wing size,and kinematically via increased stroke amplitude during thewingbeat. Such compensatory mechanisms result in fairly constantpower requirements for hovering at different elevations, butdecrease the margin of excess power available for other flightbehaviors.     

The pulmonary circulation of some domestic animals at high altitude

Pulmonary haemodynamics and the histology of the pulmonary vasculature have been studied at high altitude in the yak, in interbreeds between yaks and cattle, and in domestic goats and sheep indigenous to high altitudes together with crosses between them and low-altitude strains. Cattle at high altitude had a higher pulmonary arterial pressure than cattle at low altitude. The yak and two interbreeds with cattle (dzos and stols) had a low pulmonary arterial pressure compared with cattle, while the medial thickness of the small pulmonary arteries was less than would be expected in cattle, suggesting that the yak has a low capacity for hypoxic pulmonary vasoconstriction and that this characteristic is transmitted genetically. Goats and sheep showed haemodynamic evidence of a limited response of the pulmonary circulation to high altitude, but no evidence that the high altitude breeds had lost this response. There were no measurable differences in the thickness of the media of the small pulmonary arteries between high- and low-altitude breeds of goats and sheep. All these species showed prominent intimal protrusions of muscle into the pulmonary veins but no specific effect of high altitude in this respect.