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PubMed1998

Gas exchange at rest during simulated altitude in patients with chronic lung disease.

BACKGROUND: To characterize the gasometric and oximetric response to simulated altitudes of 3,100 m and sea level of patients with Chronic Obstructive Pulmonary Disease (COPD) and Interstitial Lung Disease (ILD) studied at 2,240 m above sea level. METHODS: Consecutive stable patients with COPD and ILD were studied at the National Institute of Respiratory Diseases, a referral center for pulmonary diseases in Mexico City, and a healthy control group. The patients breathed room air (FIO2 = 0.21), for at least 15 min, then, a hypoxic mixture (FIO2 = 0.18, simulating 3,100 m), and finally, a hyperoxic mixture (FIO2 = 0.28, simulating sea level). Arterial blood gases and oxygen saturation were measured by a pulse oximeter at the end of each stage. RESULTS: Twelve patients with COPD, 13 patients with ILD and 11 healthy controls were studied. The PaCO2 and pH were constant in the three study stages in both groups of patients and controls. A slope of PaO2 vs. altitude of 9 Torr per Km was found for each of the study's patients, either by simple linear regression or multiple regression, which is identical to that previously obtained at sea level with COPD patients (Gong et al.). Oxygen desaturation per Km of altitude change was alinear, higher for the hypoxic than for the hyperoxic challenge and more severe for the most hypoxic patients. CONCLUSIONS: Exposure tests to simulated altitudes are safe, and orient the physician concerning the patient's condition at altitudes different from the place where the measurement is done. Alveolar ventilation remains constant despite hypoxia or hyperoxia during the challenges. A computer model of the lung reproduces many of the findings in the challenges of this study.

Adult↗
PubMedDate not supplied

Pollen, mite and mould samplings by a personal collector at high altitude in Nepal.

The new personal portable sampler for detection of environmental biologic particles (Partrap FA52, Coppa, Biella, Italy) was used to evaluate both atmospheric and indoor biologic particles in bedding at high altitudes during two Italian scientific expeditions in Nepal, in 1994 and 1996 respectively. The sampling was performed outdoors and indoors at the following altitudes: Katmandu 1,330 meters (m), LuKla 2,800 m, Namche 3,500 m, Pericle 4,200 m and Piramide 5,050 m. In both expeditions each sample of outdoor and indoor air was obtained by sucking air into the sampler either against the wind during a 6-h period, from 9 am to 3 pm, or from bedding of inhabitants resident at the different altitudes for 5 min. The number of pollens, moulds and mites trapped in each sample were assessed. The statistical analysis of the results by Spearman correlation test revealed a significant inverse correlation (p < 0.02) between altitude and the number of the considered biologic particles for sampling carried out during both the 1994 and 1996 expeditions. Moreover, Wilcoxon paired test showed no significant difference between the biologic sampling obtained in the two expeditions. These results confirm the decrease of the environmental biologic charge in relation to the increase of altitude and prove the efficacy of Partrap FA52 in obtaining reproducible quantitative data.

Air Pollution↗
PubMed1998

Paternal directional mating in two Amerindian subpopulations located at different altitudes in northwestern Argentina.

We used mitochondrial DNA (mtDNA) and Y-chromosome DNA polymorphisms to analyze the ethnic origin of maternal and paternal lineages in two Amerindian subpopulations from northwestern Argentina. One of the subpopulations was from San Salvador de Jujuy, located 1200 m above sea level. The second subpopulation inhabits the Quebrada de Humahuaca area at altitudes ranging from 2500 to 3500 m. Both subpopulations have the same ethnic background. All mtDNA haplotypes were identified as Amerindian with a frequency of 64.6% of the B form (9-bp deletion in mtDNA region V). Because all Central Andean Amerindian populations studied so far exhibit high frequencies of the B haplotype, we propose that they probably are derived from a common ancestral population that inhabited the Central Andes 6000-8000 years B.P. The presence of paternal directional mating (asymmetric contribution of one parental lineage to interethnic gene mixtures) was demonstrated by the finding of an average introgression of 40.5% Spanish Y chromosomes into our Amerindian sample. This introgression was more evident at low altitude than at high altitude, with frequencies of 64.3% in San Salvador de Jujuy (low altitude) and 27.6% in Quebrada de Humahuaca (high altitude) (p < 0.05). The San Salvador de Jujuy subpopulation also showed a significantly higher Y-chromosome gene variability than the Quebrada de Humahuaca subpopulation. These findings are in good agreement with historical reports indicating that the colonization of South America was undertaken by men who usually practiced polygamous unions with Amerindian women and that San Salvador de Jujuy was the main northwestern Argentinian region of European to Amerindian gene admixture. We found 16.7% of cases with Spanish Y chromosomes and Amerindian family names, and the same percentage with Amerindian Y chromosomes and Hispanic names. The former group probably is the result of unions between Hispanic men, who transmitted the Y chromosome, and Amerindian women, who transmitted the family name to the progeny. The latter group likely illustrates the practice of changing names from Amerindian to Hispanic during the baptism of native Americans in colonial times.

Adult↗
PubMed1999

Exercise-induced altitude decompression sickness.

BACKGROUND: It has been known since World War II that exercise at altitude increases incidence of decompression sickness (DCS). However, data on the effects of specific exercise types at altitude are lacking. This research focused on the relative hazards of exercise without motion (isometric, straining) vs. dynamic exercise involving motion. The study also compared arm vs. leg exercise. METHODS: There were 32 healthy male subjects exposed, while resting, to 29,500 ft (8992 m) for 4 h or until DCS occurred, at which time they were brought to ground level. If the subject developed DCS on this exposure, he was exposed in successive months to lower altitudes, using the same procedure, until the subject was free of symptoms for the 4-h exposure. At this symptom-free altitude, as low as 20,000 ft (6096 m), the subject performed isometric arm, isometric leg, dynamic arm and dynamic leg exercises at less than 10% of maximal oxygen consumption, each during separate exposure months. Precordial venous gas emboli (VGE) were monitored every 20 min during each exposure with a Hewlett-Packard SONOS 1000 Echo Imaging System. RESULTS: Dynamic arm, dynamic leg, isometric arm, and isometric leg exercise induced DCS in 50%, 38%, 41% and 31% of the subjects, respectively. VGE incidence varied from 47-66%. No significant differences in DCS or VGE were found. CONCLUSIONS: Under our test conditions, there was no difference between dynamic and isometric exercise in eliciting DCS. Exercise during exposure to the symptom-free altitude for 4 h produced a 40% incidence DCS.

Adult↗
PubMed2004

Prevention and Treatment of High-altitude Illness in Travelers.

High-altitude illness is the collective term for acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE). These syndromes can affect unacclimatized travelers shortly after ascent to high altitude (especially higher than 2500 m). AMS is relatively common and usually is mild and self-limiting; HACE and HAPE are uncommon but life-threatening. Gradual ascent is the best strategy for preventing or minimizing high-altitude illness, although chemoprophylaxis may be useful in some situations. Acetazolamide remains the chemoprophylactic agent of choice, although other drugs, such as gingko biloba, are being investigated. Immediate descent remains the cornerstone of treatment for HACE and HAPE, although pharmacologic and hyperbaric therapies may facilitate this process.

Journal Article↗
PubMed1977

Reduction of pore area of the avian eggshell as an adaptation to altitude.

Standard measurements of water vapor conductance in units of mg of H(2)O . day(-1) . torr(-1) (SI equivalent is mg of H(2)O . day(-1) . pascal(-1)) of fresh eggs of the red-winged blackbird (Agelaius phoeniceus) and the native chicken of India (Gallus gallus) collected at altitude are significantly less than those of eggs of the same species collected near sea level. This decrease is caused by a reduction of the total effective pore area of the eggshell at altitude. It appears to be proportional to the reduction in barometric pressure and the simultaneous increase in the diffusion coefficient of water vapor. Thus, reduction in pore area offsets increased diffusivity at altitude, and water vapor loss through the eggshell at any altitude remains the same as at sea level. The data suggest a structural adaptation of the shell to altered diffusivity of gases at altitude in order to prevent excessive water loss of eggs during natural incubation.

Journal Article↗
PubMed1999

Environmental stress and 3-day eventing: effects of altitude.

Three-day event horses are subject to various external environmental stresses including changes in ambient temperature, humidity, altitude, and test severity. Considerable research on the adverse effects of increased heat and humidity preceded the 1996 Olympic Summer Games in Atlanta, Georgia USA, but no research has been done previously on the effects of altitude on 3-day eventing. Physical and venous blood gas data were collected on horses (n = 24) competing in the High Prairie Preliminary (CCN*) and Intermediate (CCN**) 3-day events and Preliminary Horse Trials in Parker, Colorado (1900 m above sea level). Despite the increased altitude, only post exercise rectal temperature and pH were higher (P < 0.05) whereas heart rate (HR), [K+], and ionized calcium (ICa++) were lower (P < 0.05) in 3-day event horses compared to horse trial horses. All other variables (respiratory rate [RR], PCV, [Hb], PCO2, [tCO2], [HCO3-], BE, and [Na+]) were not different between groups (P > 0.05). When these preliminary horse trial horses in Colorado were compared to those previously studied at preliminary horse trials at sea level in Arizona, post exercise HR and RR were higher (P < 0.05) and pH, PCO2, [tCO2], [HCO3-], BE and [iCa++] were lower (P < 0.05) at altitude. These data show that increased altitude (1900 m above sea level) was more stressful for 3-day event horses, but did not result in the severe physiological changes and inability to complete prescribed exercise tests seen in previous studies with increased heat and humidity. It is clear from these and previous data that increased heat and humidity are the more important environmental stressors in 3-day eventing.

Animals↗
PubMed1998

Blunted hypoxic pulmonary vasoconstrictive response in the rodent Ochotona curzoniae (pika) at high altitude.

To investigate the possible mechanisms of adaptation to chronic hypoxia in the pulmonary circulation, we made direct measurements of pulmonary arterial pressure (Ppa) in 10 awake pika rodents that were transported to Xining, People's Republic of China (altitude 2,260 m) after being captured at 4,300 m and in 10 Wistar rats in a decompression chamber (simulated altitudes of 4,300 and 5,000 m) in Xining. Ppa was obtained at 1 h of exposure to each simulated altitude. The histology and immunohistochemistry of the lung tissues were also studied. Ppa in the pikas after the 4,300- and 5,000-m altitude exposures did not significantly increase, whereas in the rats Ppa rose significantly. Mean changes in Ppa from 2,260 to 4,300 and 5,000 m were 1.48 +/- 0.49 and 4.80 +/- 0.67 mmHg in the pikas and 10.38 +/- 3.36 and 19.10 +/- 2.28 mmHg in the rats. The ratio of right ventricular to left ventricular plus septal weight in the pikas and rats was 0.22 and 0.45, respectively. The pikas maintained levels of Hb, hematocrit, and 2,3-diphosphoglycerate lower than those of the rats. The percent wall thickness of the small pulmonary arteries in the pikas and rats was 9.22 and 27.21%, respectively, and it was well correlated with the degree of Ppa in both groups. Mast cells were observed in the lungs of the rats (7.1 +/- 0.33 cells/mm2) but not in the pikas. There was highly positive staining for mast cell tryptase and transforming growth factor-beta around pulmonary vessels in the rats, whereas no demonstrable reaction was observed in the pikas. We conclude that the pika has adapted to high altitude by losing hypoxic pulmonary vasoconstriction and thin-walled pulmonary arterioles.

Animals↗
PubMed1975

Inherited susceptibility of cattle to high-altitude pulmonary hypertension.

This study examines the hypothesis that susceptibility of cattle to high-altitude pulmonary hypertension and heart failure (high mountain disease) is genetically transmitted. Eight offspring of cattle recovered from high mountain disease were considered "susceptible." Eleven offspring of healthy cattle residing at high altitude were considered "resistant." At the resident altitude of 1,524 m, 10-day-old susceptible calves had higher pulmonary arterial pressures than did resistant calves (34 vs.21 mmHg), but at 90 days of age the pressures for the two groups were similar (26 vs. 24 mmHg). After 64 days of exposure to an altitude of 3,048 m, the susceptible calves (87 +/- 7 (SE) vs. 40 +/- 3 mmHg). By 124 days at 3,048 m, all susceptible but none of the resistant calves had developed heart failure. The results indicated that susceptibility to pulmonary hypertension at high altitude was inherited. Susceptible cattle may provide a useful model of human hypoxic pulmonary hypertension.

Age Factors↗
PubMed2004

Food for high-altitude expeditions: Pugh got it right in 1954--a commentary on the report by L.G.C.E. Pugh: "Himalayan rations with special reference to the 1953 expedition to Mount Everest".

An examination of the nutritional recommendations at altitude by L.G.C.E. Pugh made in the early 1950s reveals that his approaches to feeding and hydration at altitude are still ascribed to today, 50 years later. We can forgive his one perhaps overstatement concerning the "craving" for carbohydrates at altitude if we simply acknowledge that he was generally correct about the benefits of carbohydrates for work at altitude. Pugh's emphasis on adequate energy intake and fluid intake at altitude is as sound today as it was in 1954.

Acclimatization↗
PubMed2005

Tibetans at extreme altitude.

Between 1960 and 2003, 13 Chinese expeditions successfully reached the summit of Chomolungma (Mt Everest or Sagarmatha). Forty-five of the 80 summiteers were Tibetan highlanders. During these and other high-altitude expeditions in Tibet, a series of medical and physiological investigations were carried out on the Tibetan mountaineers. The results suggest that these individuals are better adapted to high altitude and that, at altitude, they have a greater physical capacity than Han (ethnic Chinese) lowland newcomers. They have higher maximal oxygen uptake, greater ventilation, more brisk hypoxic ventilatory responses, larger lung volumes, greater diffusing capacities, and a better quality of sleep. Tibetans also have a lower incidence of acute mountain sickness and less body weight loss. These differences appear to represent genetic adaptations and are obviously significant for humans at extreme altitude. This paper reviews what is known about the physiologic responses of Tibetans at extreme altitudes.

Acclimatization↗
PubMed2002

Pathogenesis of high-altitude pulmonary edema: inflammation is not an etiologic factor.

CONTEXT: The pathogenesis of high-altitude pulmonary edema (HAPE) is considered an altered permeability of the alveolar-capillary barrier secondary to intense pulmonary vasoconstriction and high capillary pressure, but previous bronchoalveolar lavage (BAL) findings in well-established HAPE are also consistent with inflammatory etiologic characteristics. OBJECTIVES: To determine whether inflammation is a primary event in HAPE and to define the temporal sequence of events in HAPE. DESIGN, SETTING, AND PARTICIPANTS: Case study from July through August 1999 of 10 subjects with susceptibility to HAPE and 6 subjects resistant to HAPE, all of whom are nonprofessional alpinists with previous mountaineering experience above 3000 m. MAIN OUTCOME MEASURES: Pulmonary artery pressure measurements and BAL findings at low altitude (490 m) and shortly before or at the onset of HAPE at an altitude of 4559 m. RESULTS: Subjects who were HAPE susceptible had higher mean (SD) pulmonary artery systolic blood pressures at 4559 m compared with HAPE-resistant subjects (66 vs 37 mm Hg; P =.004). Despite development of HAPE in the majority of HAPE-susceptible subjects, there were no differences in BAL fluid total leukocyte counts between resistant and susceptible subjects or between counts taken at low and high altitudes. Subjects who developed HAPE had BAL fluid with high concentrations of plasma-derived proteins and erythrocytes, but there was no increase in plasma concentrations of surfactant protein A and Clara cell protein. The chest radiograph score was 12.7 for the 3 HAPE-susceptible subjects who developed HAPE before BAL was performed; they were lavaged within 3 to 5 hours. The remainder of the HAPE-susceptible group was lavaged before edema was apparent on radiographs. However, 6 subjects from the HAPE-susceptible group who developed HAPE on the following day had a score on bronchoscopy of 1.5, which increased to 4.6, reflective of mild pulmonary edema. In HAPE cases, there were no elevations in a number of proinflammatory cytokines and eicosanoid and nitric oxide metabolites. CONCLUSIONS: Early HAPE is characterized by high pulmonary artery pressures that lead to a protein-rich and mildly hemorrhagic edema, with normal levels of leukocytes, cytokines, and eicosanoids. HAPE is a form of hydrostatic pulmonary edema with altered alveolar-capillary permeability.

Adult↗
PubMed1984

Hemoglobin levels in a Himalayan high altitude population.

This report presents data on hemoglobin concentrations in a sample of Himalayan high altitude natives measured at their habitual altitude of residence. In this sample of 270 healthy Tibetan adults resident at 3250-3560 m in Upper Chumik , Nepal, the mean hemoglobin concentration is 16.1 +/- 1.2 gm/dl among adult males, 14.4 +/- 1.4 gm/dl among premenopausal and 15.0 +/- 1.1 gm/dl among postmenopausal adult females. 123 of 126 (98%) males, 96 of 100 (96%) premenopausal and 36 of 44 (82%) postmenopausal females have hemoglobin concentrations within two standard deviations of the sea level mean. These data demonstrate that a healthy population may reside at high altitude without the degree of elevation in hemoglobin widely known and cited for Andean highlanders. Comparing published data on mean hemoglobin concentrations of adult Himalayan and Andean samples residing between 3200 m and 4100 m reveals that Himalayan means are systematically lower. This in turn may account for the reported population differences in the prevalence of chronic mountain sickness ( Monge 's disease). It is hypothesized that Himalayan and Andean highlanders represent alternative patterns of high altitude hematological adaptation.

Adaptation, Physiological↗
PubMed2006

Pulmonary hypertension in high-altitude dwellers: novel mechanisms, unsuspected predisposing factors.

Studies of high-altitude populations, and in particular of maladapted subgroups, may provide important insight into underlying mechanisms involved in the pathogenesis of hypoxemia-related disease states in general. Over the past decade, studies involving short-term hypoxic exposure have greatly advanced our knowledge regarding underlying mechanisms and predisposing events of hypoxic pulmonary hypertension. Studies in high altitude pulmonary edema (HAPE)-prone subjects, a condition characterized by exaggerated hypoxic pulmonary hypertension, have provided evidence for the central role of pulmonary vascular endothelial and respiratory epithelial nitric oxide (NO) for pulmonary artery pressure homeostasis. More recently, it has been shown that pathological events during the perinatal period (possibly by impairing pulmonary NO synthesis), predispose to exaggerated hypoxic pulmonary hypertension later in life. In an attempt to translate some of this new knowledge to the understanding of underlying mechanisms and predisposing events of chronic hypoxic pulmonary hypertension, we have recently initiated a series of studies among high-risk subpopulations (experiments of nature) of high-altitude dwellers. These studies have allowed to identify novel risk factors and underlying mechanisms that may predispose to sustained hypoxic pulmonary hypertension. The aim of this article is to briefly review this new data, and demonstrate that insufficient NO synthesis/bioavailability, possibly related in part to augmented oxidative stress, may represent an important underlying mechanism predisposing to pulmonary hypertension in high-altitude dwellers.

Altitude↗
PubMed2000

Effect of high altitude on sensitivity to the taste of phenylthiocarbamide.

Sensitivity to the taste of phenylthiocarbamide (PTC) was studied using the Harris-Kalmus method in healthy human volunteers at sea level and then subsequently at an altitude of 3500 m over a period of 3 weeks, after which they were brought back to sea level. Blood sugar, insulin and blood cortisol levels were estimated weekly. The results indicated that, out of 51 subjects studied, 26 (55%) were PTC tasters at sea level. Eight of those unable to taste PTC at sea level tested as tasters at high altitude, and 2 of them reverted to being non-tasters on return to sea level. In the blood, an increase in cortisol and blood insulin levels was seen without any significant change in sugar levels. All the changes recorded at high altitude tended to return to basal values after re-induction to sea level. The study suggests that high-altitude hypoxia in some way, possibly involving changes in hormonal profile among other factors, causes an alteration in sensitivity to the taste of PTC, resulting in some of the individuals shifting to lower PTC sensitivity.

Acclimatization↗
PubMed1995

Topographic EEG changes due to hypobaric hypoxia at simulated high altitude.

Multichannel human EEG signals were studied topographically in subjects exposed to an atmosphere of reduced air pressure in a chamber in which high-altitude conditions were simulated. EEG signals from 16 electrodes placed on the scalp were recorded simultaneously with electrocardiography and vertical eye movement. Baseline records were first obtained at sea level (PRE 0 m), and then at reduced air pressures corresponding to the altitudes of 3000 m, 4000 m, and 6000 m, respectively, and after returning to sea level (POST 0 m). A complete set of EEG records under all 6 conditions was obtained in 5 of the 15 subjects, and under 5 conditions (all except the 6000 m condition) in 3 other subjects. The spectral powers of 1 min epochs of the multichannel EEG signal under each altitude condition were compared to that at PRE 0 m using analysis of variance. Under the 3000 m condition, the spectral power of the 10-11 Hz components was significantly decreased and, with increasing altitude, significant decrease of spectral power was observed in a wider range of the alpha frequency band. Under the 6000 m condition, the decrease of spectral power of the alpha band in the posterior brain areas was -7 dB compared to the baseline. In contrast, the spectral power of the theta frequency band in anterior brain areas increased significantly in the 5000 m and 6000 m conditions. At the POST 0 m condition after return from the 5000 m condition (without exposure to the 6000 m condition), the EEG showed recovery to the level of the baseline PRE 0 m condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Renal carbonic anhydrase inhibition reduces high altitude sleep periodic breathing.

The efficacy of carbonic anhydrase (CA) inhibitors in amelioration of periodic breathing during sleep at high altitude is not fully understood. Although CA is present in a number of tissues, we hypothesized that selective renal CA inhibition without physiologically important inhibition of other tissue CA, may be sufficient alone by its generation of a mild metabolic acidosis to stimulate ventilation and prevent periodic breathing. We studied benzolamide (3 mg/kg), a selective inhibitor of renal CA, in 4 climbers on ventilation and ventilatory responses at sea level and on arterial O2 saturation (SaO2%) and periodic breathing during sleep at altitude. At sea level, ventilation increased and PaO2 rose accompanied by a mild metabolic acidosis. The isocapnic hypoxic ventilatory response was unchanged but the hyperoxic hypercapnic ventilatory response rose 40%. At high altitude (4400 m), daytime SaO2% improved from 81 to 85 and venous plasma HCO3- fell from 18.9 to 14.8 mM. During sleep, mean SaO2% rose from 76 to 80 and periodic breathing decreased 75%. We conclude that metabolic acidosis occurring with all CA inhibitors is one of the major stimulant actions of these drugs on ventilation while awake and during sleep at high altitude.

Acidosis↗
PubMed1982

Platelet count, platelet aggregation and fibrinogen levels following acute induction to high altitude (3200 and 3771 metres).

Two groups of 20 subjects each were separately exposed to altitudes of 3200 m and 3771 m for 10 days by rapid induction requiring 14 and 16 hours respectively to reach high altitude camps. A statistically significant fall in platelet counts was observed from day 2 at 3200 m and day 3 at 3771 m and counts remained decreased. Platelet aggregation was also decreased initially at both altitudes. Blood fibrinogen decreased only on day 2 at 3771 m with a significant increase over control values by day 10 at both altitudes.

Adult↗