Open AccessCerebrovascular Responsiveness to Hypercapnia Is Stable over Six Months in Older Adults
Author(s) -
Matthew D. Spencer,
Amanda V. Tyndall,
Margie H. Davenport,
Laurie Argourd,
Todd J. Anderson,
Gail A. Eskes,
Christine M. Friedenreich,
David B. Hogan,
Richard Leigh,
Bernard Meshi,
Eric E. Smith,
Ben Wilson,
Stephen B. Wilton,
Marc J. Poulin
Publication year - 2015
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0143059
Subject(s) - hypercapnia , transcranial doppler , middle cerebral artery , medicine , context (archaeology) , cerebral blood flow , pco2 , blood flow , cardiology , cerebral arteries , anesthesia , ischemia , acidosis , paleontology , biology
The primary purpose of this Brain in Motion (BIM) sub-study was to determine the 6-month stability of resting blood flow velocity and cerebrovascular responsiveness to a euoxic hypercapnic challenge in a group of physically inactive community dwelling men and men aged ≥55 yrs (range 55–92 yrs). At baseline and 6 months later 88 women (65±6 yr) and 78 men (67±7 yr) completed a hypercapnic challenge (step changes from resting end-tidal P CO2 ((PET CO2 ) to +1, +5 and +8 mmHg above rest) while cerebral blood flow velocity was assessed using transcranial Doppler ultrasound. Peak velocity of the middle cerebral artery (MCAv) was increased (p<0.05) at the second visit during rest (51±2 vs. 52±4); however, these differences were abolished (p>0.05) when MCAv was normalized to PET CO2 . During hypercapnia, MCAv tended to be increased at follow-up, but this finding was absent when MCAv/PET CO2 was compared across time. Cerebrovascular reactivity (i.e., ΔMCAv/ΔPET CO2 ) was similar (p>0.05) between testing occasions regardless of the approach taken (i.e., considering only the lower step [from +1 to +5 mmHg]; the upper step [+5 to +8 mmHg]; or the complete test taken together). In conclusion, this study has shown that cerebral blood flow and cerebrovascular responsiveness to acute euoxic hypercapnia are stable in older, healthy adults over a 6-month period. Modest changes in MCAv over time must be viewed in the context of underlying differences in PET CO2 , an important finding with implications for future studies considering cerebral blood flow velocity.