The effect of basal vasodilation on hypercapnic and hypocapnic reactivity measured using magnetic resonance imaging

Molly G. Bright, Manus J. Donahue, Jeff H. Duyn, Peter Jezzard, Daniel P. Bulte

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Cerebrovascular reactivity to vasodilatory hypercapnic and vasoconstrictive hypocapnic challenges is known to be altered in several hemodynamic disorders, which is often attributable to changes in smooth muscle-mediated vascular compliance. Recently, attenuated reactivity to hypercapnia but enhanced reactivity to hypocapnia was observed in patients with chronic stroke. We hypothesize that the latter observation could be explained by a change in the basal vascular tone. In particular, reduced cerebral perfusion pressure, as is prevalent in these patients, may cause vasodilation through autoregulatory mechanisms, and this compensatory baseline condition may alter reactivity to vasoconstrictive hypocapnic challenges. To test this hypothesis, a predilated vascular condition was created in young, healthy subjects (n11; age23 to 36 years) using inhalation of 4% CO2. Using blood oxygenation level-dependent functional magnetic resonance imaging at 3 T, breath holding and cued deep breathing respiratory challenges were administered to assess hypercapnia and hypocapnia reactivity, respectively. During the predilated condition, vasoconstrictive reactivity to hypocapnia was significantly (21.1%, P0.016) enhanced throughout the gray matter, whereas there was no significant change (6.4%, P0.459) in hypercapnic vasodilatory reactivity. This suggests that baseline vasodilation may explain the enhanced hypocapnia reactivity observed in some stroke patients, and that hypocapnia challenges may help identify the level of vascular compliance in patients with reduced cerebral perfusion pressure.

Original languageEnglish (US)
Pages (from-to)426-438
Number of pages13
JournalJournal of Cerebral Blood Flow and Metabolism
Issue number2
StatePublished - Feb 2011


  • BOLD
  • CO2
  • cerebrovascular reactivity
  • hypercapnia
  • hypocapnia
  • respiration

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology
  • Cardiology and Cardiovascular Medicine

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