title: AltitudeOmics: cerebral autoregulation during ascent, acclimatization, and re-exposure to high altitude and its relation with acute mountain sickness.
abstract: 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.
authors.affiliation: University of Colorado Altitude Research Center, Department of Emergency Medicine, Anschutz Medical Campus, Aurora, Colorado;
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Subudhi
authors.forename: Jui-Lin
authors.initials: JL
authors.lastname: Fan
authors.forename: Oghenero
authors.initials: O
authors.lastname: Evero
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bourdillon
authors.forename: Bengt
authors.initials: B
authors.lastname: Kayser
authors.forename: Colleen G
authors.initials: CG
authors.lastname: Julian
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Lovering
authors.forename: Ronney B
authors.initials: RB
authors.lastname: Panerai
authors.forename: Robert C
authors.initials: RC
authors.lastname: Roach
mesh_terms: D000064:Acclimatization; D000208:Acute Disease; D000531:Altitude; D000532:Altitude Sickness / Q000175:diagnosis / Q000503:physiopathology*; D062186:Arterial Pressure; D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation; D005260:Female; D006706:Homeostasis; D006801:Humans; D000860:Hypoxia / Q000175:diagnosis / Q000503:physiopathology*; D008297:Male; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017534:Radial Artery / Q000503:physiopathology; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013997:Time Factors; D017585:Ultrasonography, Doppler, Transcranial; D055815:Young Adult
keywords: cerebral blood flow; cerebral oxygenation; hypoxia; transcranial Doppler; transfer function analysis