In:
Journal of Applied Physiology, American Physiological Society, Vol. 117, No. 10 ( 2014-11-15), p. 1084-1089
Abstract:
In the evaluation of cerebrovascular CO 2 reactivity measurements, it is often assumed that the diameter of the large intracranial arteries insonated by transcranial Doppler remains unaffected by changes in arterial CO 2 partial pressure. However, the strong cerebral vasodilatory capacity of CO 2 challenges this assumption, suggesting that there should be some changes in diameter, even if very small. Data from previous studies on effects of CO 2 on cerebral artery diameter [middle cerebral artery (MCA)] have been inconsistent. In this study, we examined 10 healthy subjects (5 women, 5 men, age 21–30 yr). High-resolution (0.2 mm in-plane) MRI scans at 7 Tesla were used for direct observation of the MCA diameter during hypocapnia, −1 kPa (−7.5 mmHg), normocapnia, 0 kPa (0 mmHg), and two levels of hypercapnia, +1 and +2 kPa (7.5 and 15 mmHg), with respect to baseline. The vessel lumen was manually delineated by two independent observers. The results showed that the MCA diameter increased by 6.8 ± 2.9% in response to 2 kPa end-tidal Pco 2 (Pet CO 2 ) above baseline. However, no significant changes in diameter were observed at the −1 kPa (−1.2 ± 2.4%), and +1 kPa (+1.4 ± 3.2%) levels relative to normocapnia. The nonlinear response of the MCA diameter to CO 2 was fitted as a continuous calibration curve. Cerebral blood flow changes measured by transcranial Doppler could be corrected by this calibration curve using concomitant Pet CO 2 measurements. In conclusion, the MCA diameter remains constant during small deviations of the Pet CO 2 from normocapnia, but increases at higher Pet CO 2 values.
Type of Medium:
Online Resource
ISSN:
8750-7587
,
1522-1601
DOI:
10.1152/japplphysiol.00651.2014
Language:
English
Publisher:
American Physiological Society
Publication Date:
2014
detail.hit.zdb_id:
1404365-8
SSG:
12
SSG:
31
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