title: Cerebral pressure-flow relationship in lowlanders and natives at high altitude.
abstract: We investigated if dynamic cerebral pressure-flow relationships in lowlanders are altered at high altitude (HA), differ in HA natives and after return to sea level (SL). Lowlanders were tested at SL (n=16), arrival to 5,050 m, after 2-week acclimatization (with and without end-tidal PO2 normalization), and upon SL return. High-altitude natives (n=16) were tested at 5,050 m. Testing sessions involved resting spontaneous and driven (squat-stand maneuvers at very low (VLF, 0.05 Hz) and low (LF, 0.10 Hz) frequencies) measures to maximize blood pressure (BP) variability and improve assessment of the pressure-flow relationship using transfer function analysis (TFA). Blood flow velocity was assessed in the middle (MCAv) and posterior (PCAv) cerebral arteries. Spontaneous VLF and LF phases were reduced and coherence was elevated with acclimatization to HA (P<0.05), indicating impaired pressure-flow coupling. However, when BP was driven, both the frequency- and time-domain metrics were unaltered and comparable with HA natives. Acute mountain sickness was unrelated to TFA metrics. In conclusion, the driven cerebral pressure-flow relationship (in both frequency and time domains) is unaltered at 5,050 m in lowlanders and HA natives. Our findings indicate that spontaneous changes in TFA metrics do not necessarily reflect physiologically important alterations in the capacity of the brain to regulate BP.
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Smirl
authors.affiliation: 1] Department of Physiology, University of Otago, Dunedin, New Zealand [2] School of Physical Education, University of Otago, Dunedin, New Zealand [3] School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, UK.
authors.forename: Samuel J E
authors.initials: SJ
authors.lastname: Lucas
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.
authors.forename: Nia C S
authors.initials: NC
authors.lastname: Lewis
authors.forename: Gregory R
authors.initials: GR
authors.lastname: duManoir
authors.affiliation: Department of Human Kinetics, Okanagan College, Penticton, British Columbia, Canada.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Dumanior
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.
authors.forename: Kurt J
authors.initials: KJ
authors.lastname: Smith
authors.affiliation: University of Twente, Enschede, The Netherlands.
authors.forename: Akke
authors.initials: A
authors.lastname: Bakker
authors.affiliation: Good Samaritan Hospital, Phoenix, Arizona, USA.
authors.forename: Aperna S
authors.initials: AS
authors.lastname: Basnyat
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.
authors.forename: Philip N
authors.initials: PN
authors.lastname: Ainslie
mesh_terms: D000064:Acclimatization; D000208:Acute Disease; D000328:Adult; D000532:Altitude Sickness / Q000503:physiopathology*; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged