Journal
JOURNAL OF APPLIED PHYSIOLOGY
Volume 116, Issue 7, Pages 724-729Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/japplphysiol.00880.2013
Keywords
transcranial Doppler; cerebral blood flow; cerebral oxygenation; transfer function analysis; hypoxia
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Funding
- U.S. Department of Defense [W81XWH-11-2-0040, W81XWH-10-2-0114]
- Cardiopulmonary & Respiratory Physiology Laboratory, University of Oregon
- Altitude Research Center
- Department of Emergency Medicine, School of Medicine, University of Colorado Denver
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Cerebral autoregulation (CA) acts to maintain brain blood flow despite fluctuations in perfusion pressure. Acute hypoxia is thought to impair CA, but it is unclear if CA is affected by acclimatization or related to the development of acute mountain sickness (AMS). We assessed changes in CA using transfer function analysis of spontaneous fluctuations in radial artery blood pressure (indwelling catheter) and resulting changes in middle cerebral artery blood flow velocity (transcranial Doppler) in 21 active individuals at sea level upon arrival at 5,260 m (ALT1), after 16 days of acclimatization (ALT16), and upon re-exposure to 5,260 m after 7 days at 1,525 m (POST7). The Lake Louise Questionnaire was used to evaluate AMS symptom severity. CA was impaired upon arrival at ALT1 (P < 0.001) and did not change with acclimatization at ALT16 or upon re-exposure at POST7. CA was not associated with AMS symptoms (all R < 0.50, P > 0.05). These findings suggest that alterations in CA are an intrinsic consequence of hypoxia and are not directly related to the occurrence or severity of AMS.
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