期刊
EXPERIMENTAL PHYSIOLOGY
卷 103, 期 11, 页码 1494-1504出版社
WILEY
DOI: 10.1113/EP087236
关键词
Flowmotion; hypobaric hypoxia; laser Doppler flowmetry; microcirculation
类别
资金
- Royal Free Hospital NHS Trust Charity
- University College London Hospital NHS Foundation Trust
- Southampton University Hospital Charity
- UCL Institute of Sports Exercise and Health
- London Clinic
- University College London
- University of Southampton
- Duke University Medical School
- United Kingdom Intensive Care Society
- National Institute of Academic Anaesthesia
- Rhinology and Laryngology Research Fund
- Physiological Society
- Smiths Medical
- Deltex Medical
- Atlantic Customer Solutions
- United Kingdom Department of Health's National Institute for Health Research Biomedical Research Centres funding scheme
- United Kingdom Department of Health's National Institute for Health Research Biomedical Research Units funding scheme
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.
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