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Sustained vasomotor control of skin microcirculation in Sherpas versus altitude-naive lowlanders: Experimental evidence from Xtreme Everest 2

Sustained vasomotor control of skin microcirculation in Sherpas versus altitude-naive lowlanders: Experimental evidence from Xtreme Everest 2
Sustained vasomotor control of skin microcirculation in Sherpas versus altitude-naive lowlanders: Experimental evidence from Xtreme Everest 2
Enhanced oxygen delivery, consequent to an increased microvascular perfusion, has been postulated to play a key role in the physiological adaptation of Tibetan highlanders to the hypobaric hypoxia encountered at high altitude. We tested the hypothesis that Sherpas, when exposed to graded hypobaric hypoxia, demonstrate enhanced vasomotor and neurovascular control to maintain microcirculatory flux, and thus tissue oxygenation, when compared with altitude‐naive lowlanders. Eighty‐three lowlanders [39 men and 44 women, 38.8 (13.1) years old; mean (SD)] and 61 Sherpas [28 men and 33 women, 27.9 (6.9) years old] were studied on ascent to Everest Base Camp over 11 days. Skin blood flux and tissue oxygen saturation were measured simultaneously using combined laser Doppler fluximetry and white light spectroscopy at baseline, 3500 and 5300 m. In both cohorts, ascent resulted in a decline in the sympathetically mediated microvascular constrictor response (P < 0.001), which was more marked in lowlanders than in Sherpas (P < 0.001). The microvascular dilator response evaluated by postocclusive reactive hyperaemia was significantly greater in Sherpas than in lowlanders at all sites (P < 0.002). Spectral analysis of the blood flux signals revealed enhanced myogenic (vasomotion) activity in Sherpas, which was unaffected by ascent to 5300 m. Although skin tissue oxygenation was lower in Sherpas than in lowlanders, the oxygen unloading rate was faster, and deoxyhaemoglobin levels higher, at all altitudes. Together, these data suggest that Sherpas, when exposed to hypobaric hypoxia, demonstrated superior preservation of peripheral microcirculatory perfusion compared with altitude‐naive lowlanders. The physiological differences in local microvasculature vasomotor and neurovascular control may play a key role in Sherpa adaptation to high‐altitude hypobaric hypoxia by sustaining local perfusion and tissue oxygenation.
0958-0670
Davies, Thomas
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Gilbert-Kawai, Edward
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Wythe, Stephen
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Meale, Paula
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Mythen, Monty
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Levett, Denny
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Mitchell, Kay
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Grocott, Michael P.
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Clough, Geraldine
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Martin, Daniel
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Davies, Thomas
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Gilbert-Kawai, Edward
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Wythe, Stephen
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Meale, Paula
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Mythen, Monty
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Levett, Denny
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Mitchell, Kay
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Grocott, Michael P.
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Clough, Geraldine
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Martin, Daniel
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Davies, Thomas, Gilbert-Kawai, Edward, Wythe, Stephen, Meale, Paula, Mythen, Monty, Levett, Denny, Mitchell, Kay, Grocott, Michael P., Clough, Geraldine and Martin, Daniel (2018) Sustained vasomotor control of skin microcirculation in Sherpas versus altitude-naive lowlanders: Experimental evidence from Xtreme Everest 2. Experimental Physiology. (doi:10.1113/EP087236).

Record type: Article

Abstract

Enhanced oxygen delivery, consequent to an increased microvascular perfusion, has been postulated to play a key role in the physiological adaptation of Tibetan highlanders to the hypobaric hypoxia encountered at high altitude. We tested the hypothesis that Sherpas, when exposed to graded hypobaric hypoxia, demonstrate enhanced vasomotor and neurovascular control to maintain microcirculatory flux, and thus tissue oxygenation, when compared with altitude‐naive lowlanders. Eighty‐three lowlanders [39 men and 44 women, 38.8 (13.1) years old; mean (SD)] and 61 Sherpas [28 men and 33 women, 27.9 (6.9) years old] were studied on ascent to Everest Base Camp over 11 days. Skin blood flux and tissue oxygen saturation were measured simultaneously using combined laser Doppler fluximetry and white light spectroscopy at baseline, 3500 and 5300 m. In both cohorts, ascent resulted in a decline in the sympathetically mediated microvascular constrictor response (P < 0.001), which was more marked in lowlanders than in Sherpas (P < 0.001). The microvascular dilator response evaluated by postocclusive reactive hyperaemia was significantly greater in Sherpas than in lowlanders at all sites (P < 0.002). Spectral analysis of the blood flux signals revealed enhanced myogenic (vasomotion) activity in Sherpas, which was unaffected by ascent to 5300 m. Although skin tissue oxygenation was lower in Sherpas than in lowlanders, the oxygen unloading rate was faster, and deoxyhaemoglobin levels higher, at all altitudes. Together, these data suggest that Sherpas, when exposed to hypobaric hypoxia, demonstrated superior preservation of peripheral microcirculatory perfusion compared with altitude‐naive lowlanders. The physiological differences in local microvasculature vasomotor and neurovascular control may play a key role in Sherpa adaptation to high‐altitude hypobaric hypoxia by sustaining local perfusion and tissue oxygenation.

Text
Davies et al Exp Physiol XE2 final accepted version with revised Figure 1 200818pm - Accepted Manuscript
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More information

Accepted/In Press date: 21 August 2018
e-pub ahead of print date: 4 September 2018

Identifiers

Local EPrints ID: 423280
URI: http://eprints.soton.ac.uk/id/eprint/423280
ISSN: 0958-0670
PURE UUID: bb9529a4-ed51-4825-8eee-3c0568043a91
ORCID for Kay Mitchell: ORCID iD orcid.org/0000-0001-6393-8475
ORCID for Michael P. Grocott: ORCID iD orcid.org/0000-0002-9484-7581
ORCID for Geraldine Clough: ORCID iD orcid.org/0000-0002-6226-8964

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Date deposited: 20 Sep 2018 16:30
Last modified: 22 Nov 2021 06:40

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Contributors

Author: Thomas Davies
Author: Edward Gilbert-Kawai
Author: Stephen Wythe
Author: Paula Meale
Author: Monty Mythen
Author: Denny Levett
Author: Kay Mitchell ORCID iD
Author: Daniel Martin

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