Cerebrovascular Responsiveness to Hypercapnia Is Stable over Six Months in Older Adults: e0143059

• Published in: PloS one 2015-11, Vol.10 (11)
• Main Authors: Spencer, Matthew D, Tyndall, Amanda V, Davenport, Margie H, Argourd, Laurie, Anderson, Todd J, Eskes, Gail A, Friedenreich, Christine M, Hogan, David B, Leigh, Richard, Meshi, Bernard
• Format: Article
• Language: English
• ISSN: 1932-6203
• DOI: 10.1371/journal.pone.0143059

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 greater than or equal to 55 yrs (range 55-92 yrs). At baseline and 6 months later 88 women (65 plus or minus 6 yr) and 78 men (67 plus or minus 7 yr) completed a hypercapnic challenge (step changes from resting end-tidal PCO2 ((PETCO2) 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 (p0.05) when MCAv was normalized to PETCO2. During hypercapnia, MCAv tended to be increased at follow-up, but this finding was absent when MCAv/PETCO2 was compared across time. Cerebrovascular reactivity (i.e., [delta]MCAv/[delta]PETCO2) 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 PETCO2, an important finding with implications for future studies considering cerebral blood flow velocity.