Barometric pressures at extreme altitudes on Mt. Everest: physiological significance

West, John B.; Lahiri, S.; Maret, K. H.; Peters, Richard M.; Pizzo, C. J.

doi:10.1152/jappl.1983.54.5.1188

Cited by 116 publications

(63 citation statements)

References 5 publications

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“…Secondly, cooler and denser conditions will increase the partial pressure of oxygen following the ideal gas law (for example, at 6,000 m the change in density altitude by 690 m would increase inspired PO 2 from ∼75-81 mm Hg, or 10-10.8 kPa), increasing the diffusion gradient at the alveoli-blood interface and potentially increasing hemoglobin saturation. This increase may be critical in O 2 uptake, as has been shown for mountaineers attempting to reach the summit of Mount Everest (27) without supplementary oxygen. In addition, early flights would avoid the potential heat load of flying at low altitudes in India during the hottest time of the day, whilst cooler nighttime and early morning temperatures could help dissipate metabolically produced heat from the body (maximum daily temperatures in the Khumbu valley were 23.4°C at 2,660 m, 17.2°C at 3,560 m, and −10°C at 5,585 m).…”

Section: Resultsmentioning

confidence: 79%

The trans-Himalayan flights of bar-headed geese ( Anser indicus )

Hawkes

Balachandran

Batbayar

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

145

125

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Birds that fly over mountain barriers must be capable of meeting the increased energetic cost of climbing in low-density air, even though less oxygen may be available to support their metabolism. This challenge is magnified by the reduction in maximum sustained climbing rates in large birds. Bar-headed geese (Anser indicus) make one of the highest and most iconic transmountain migrations in the world. We show that those populations of geese that winter at sea level in India are capable of passing over the Himalayas in 1 d, typically climbing between 4,000 and 6,000 m in 7-8 h. Surprisingly, these birds do not rely on the assistance of upslope tailwinds that usually occur during the day and can support minimum climb rates of 0.8-2.2 km·h −1 , even in the relative stillness of the night. They appear to strategically avoid higher speed winds during the afternoon, thus maximizing safety and control during flight. It would seem, therefore, that bar-headed geese are capable of sustained climbing flight over the passes of the Himalaya under their own aerobic power.exercise physiology | high altitude | satellite tracking | vertebrate migration | climbing flight M ountains and high plateaus present formidable obstacles to the migratory flights of a number of bird species. Large birds, such as cranes and geese, may find such barriers particularly challenging as the sustained climbing rates of birds scale negatively with increasing body mass (1). For example, brent geese (Branta bernicla) are unable to sustain climbing flights over the Greenland icecap (summit elevation 3,207 m, mean elevation >2,000 m) and make regular stops to recover, possibly from partly anaerobic flights (2). Nevertheless, populations of bar-headed geese (Anser indicus) that spend the winter at sea level in India and the summer in central Asia must perform the world's steepest migratory flight north over the highest mountain range on earth, the Himalaya (3). There, most passes are at altitudes greater than 5,000 m, where the air density and partial pressure of oxygen are only about half of those at sea level. As a consequence, the partial pressure of oxygen (PO 2 ) in the arterial blood may begin to limit maximum performance (4, 5), although negative effects on the rate of oxygen diffusion may be partially ameliorated by an increase in the gas diffusion coefficient (6). The thinner air at these higher altitudes will also reduce lift generation during flapping flight for any given air speed, thus increasing the energy costs of flying by around 30% (7,8).However, bar-headed geese have adapted in a variety of ways for living and flying at high altitudes (4, 5). Their skeletal and cardiac muscles are better supplied with oxygen, having greater capillary density, more homogenous capillary spacing, a higher proportion of mitochondria in a subsarcolemmal location, and a greater proportion of oxidative fibers than other waterfowl (9, 10). Bar-headed goose hemoglobin is also highly effective at oxygen loading (11), compared with many other bird species, largel...

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Section: Resultsmentioning

confidence: 79%

The trans-Himalayan flights of bar-headed geese ( Anser indicus )

Hawkes

Balachandran

Batbayar

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

145

125

View full text Add to dashboard Cite

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“…This change is more pronounced at higher latitudes and during the winter [3] and leads to lower inspired oxygen partial pressure, alveolar oxygen partial pressure (PA,O 2 ) and arterial oxygen tension (Pa,O 2 ) values. Air density and ambient temperature also decrease, with the latter falling at a rate of 1uC for every 150-m gain in elevation [4].…”

Section: Environmental Changes At High Altitude That May Affect Pulmomentioning

confidence: 99%

Travel to high altitude with pre-existing lung disease

Luks

Swenson²

2007

Eur Respir J

107

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The pathophysiology of high-altitude illnesses has been well studied in normal individuals, but little is known about the risks of high-altitude travel in patients with pre-existing lung disease. Although it would seem self-evident that any patient with lung disease might not do well at high altitude, the type and severity of disease will determine the likelihood of difficulty in a high-altitude environment. The present review examines whether these individuals are at risk of developing one of the main forms of acute or chronic high-altitude illness and whether the underlying lung disease itself will get worse at high elevations. Several groups of pulmonary disorders are considered, including obstructive, restrictive, vascular, control of ventilation, pleural and neuromuscular diseases. Attempts will be made to classify the risks faced by each of these groups at high altitude and to provide recommendations regarding evaluation prior to high-altitude travel, advice for or against taking such excursions, and effective prophylactic measures.

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“…Given that flight is a particularly costly form of transport, in terms of the rate of oxygen consumption, and that oxygen becomes progressively more rarefied at higher altitudes, powered flight should become progressively more challenging with altitude. For example, at 8000 m, the minimum mechanical power required for flight is 50 per cent greater than that at sea level [34], whereas the partial pressure of oxygen is 40 per cent lower than that at sea level [35]. The postulated high-altitude migration of bar-headed geese is thus a paradox of avian migration ecology and physiology [17].…”

Section: Introductionmentioning

confidence: 99%

The paradox of extreme high-altitude migration in bar-headed geeseAnser indicus

et al. 2013

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Bar-headed geese are renowned for migratory flights at extremely high altitudes over the world's tallest mountains, the Himalayas, where partial pressure of oxygen is dramatically reduced while flight costs, in terms of rate of oxygen consumption, are greatly increased. Such a mismatch is paradoxical, and it is not clear why geese might fly higher than is absolutely necessary. In addition, direct empirical measurements of high-altitude flight are lacking. We test whether migrating bar-headed geese actually minimize flight altitude and make use of favourable winds to reduce flight costs. By tracking 91 geese, we show that these birds typically travel through the valleys of the Himalayas and not over the summits. We report maximum flight altitudes of 7290 m and 6540 m for southbound and northbound geese, respectively, but with 95 per cent of locations received from less than 5489 m. Geese travelled along a route that was 112 km longer than the great circle (shortest distance) route, with transit ground speeds suggesting that they rarely profited from tailwinds. Bar-headed geese from these eastern populations generally travel only as high as the terrain beneath them dictates and rarely in profitable winds. Nevertheless, their migration represents an enormous challenge in conditions where humans and other mammals are only able to operate at levels well below their sea-level maxima.

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Barometric pressures at extreme altitudes on Mt. Everest: physiological significance

Cited by 116 publications

References 5 publications

The trans-Himalayan flights of bar-headed geese ( Anser indicus )

The trans-Himalayan flights of bar-headed geese ( Anser indicus )

Travel to high altitude with pre-existing lung disease

The paradox of extreme high-altitude migration in bar-headed geeseAnser indicus

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