Obesity seems to be associated with the development of AMS, which may be partly related to greater nocturnal desaturation with altitude exposure.

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 Ppafrom 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-β 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.

Yoshimura. Exercise performance of Tibetan and Han adolescents at altitudes of 3,417 and 4,300 m. J. Appl. Physiol. 83(2): 661-667, 1997.-The difference was studied between O 2 transport in lifelong Tibetan adolescents and in newcomer Han adolescents acclimatized to high altitude. We measured minute ventilation, maximal O 2 uptake, maximal cardiac output, and arterial O 2 saturation during maximal exercise, using the incremental exercise technique, at altitudes of 3,417 and 4,300 m. The groups were well matched for age, height, and nutritional status. The Tibetans had been living at the altitudes for a longer period than the Hans (14.5 6 0.2 vs. 7.8 6 0.8 yr at 3,417 m, P , 0.01; and 14.7 6 0.3 vs. 5.3 6 0.7 yr at 4,300 m, P , 0.01, respectively). At rest, Tibetans had significantly greater vital capacity and maximal voluntary ventilation than the Hans at both altitudes. At maximal exercise, Tibetans compared with Hans had higher maximal O 2 uptake (42.2 6 1.7 vs. 36.7 6 1.2 ml · min 21 ·kg 21 at 3,417 m, P , 0.01; and 36.8 6 1.9 vs. 30.0 6 1.4 ml · min 21 ·kg 21 at 4,300 m, P , 0.01, respectively) and greater maximal cardiac output (12.8 6 0.3 vs. 11.4 6 0.2 l/min at 3,417 m, P , 0.01; 11.5 6 0.5 vs. 10.0 6 0.5 l/min at 4,300 m, P , 0.05, respectively). Although the differences in arterial O 2 saturation between Tibetans and Hans were not significant at rest and during mild exercise, the differences became greater with increases in exercise workload at both altitudes. We concluded that exposure to high altitude from birth to adolescence resulted in an efficient O 2 transport and a greater aerobic exercise performance that may reflect a successful adaptation to life at high altitude. cardiac output; maximal oxygen consumption; ventilation; developmental adaptation; genetic adaptation MAXIMAL O 2 UPTAKE (V O 2 max ), an integrated index of the overall functional capacity of the O 2 transport system, invariably decreases with altitude during both acute and chronic exposure to high altitude in lowland adults (31,34). This is due to the reduction of ambient O 2 pressure at high altitude. Although comparative studies of V O 2 max between high altitude natives and lowland residents at high-altitude have been done, the conclusions are controversial (10-13, 30). High-altitude adult natives in either Andean or Himalayan populations have higher exercise performance and maintain better arterial O 2 saturation (Sa O 2 ) during exercise compared with newcomers (17,20,30,38). These characteristics, which are associated with more efficient pulmonary gas exchange (38) and better adaptation to high-altitude stress, are acquired through many generations of lifelong high-altitude exposure. The Tibetans are believed to have lived at high altitude longer than other highaltitude residents. The effects of high-altitude hypoxia on the physiological responses of Tibetan and Han adolescents to exercise have never been reported. Whether the pulmonary adaptations in humans are determined purely by environment or relate to genetic character...

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Since first cloned and reported by Zhang et al in 1994 (Nature 372:425)

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High-altitude heart disease, a form of chronic mountain sickness, has been well established in both Tibet and Qinghai provinces of China, although little is known regarding this syndrome in other countries, particularly in the West. This review presents a general overview of high-altitude heart disease in China and briefly summarizes the existing data with regard to the prevalence, clinical features, and pathophysiology of the illness. The definition of high-altitude heart disease is right ventricular enlargement that develops primarily (by high-altitude exposure) to pulmonary hypertension without excessive polycythemia. The prevalence is higher in children than adults and in men than women, but is lower in both sexes of Tibetan high-altitude residents compared with acclimatized newcomers, such as Han Chinese. Clinical symptoms consist of headache, dyspnea, cough, irritability, and sleeplessness. Physical findings include a marked cyanosis, rapid heart and respiratory rates, edema of the face, liver enlargement, and rales. Most patients have complete recovery on descent to a lower altitude, but symptoms recur with a return to high altitude. Right ventricular enlargement, pulmonary hypertension, and remodeling of pulmonary arterioles are hallmarks of high-altitude heart disease. It is hoped that this information will assist in understanding this type of chronic mountain sickness, facilitate international exchange of data, and stimulate further research into this poorly understood condition.

Heatmap of species composition in different yogurt samples (At genus level).