In:
Journal of Applied Physiology, American Physiological Society, Vol. 95, No. 6 ( 2003-12), p. 2453-2461
Abstract:
Breathing 100% O 2 at 1 atmosphere absolute (ATA) is known to be associated with a decrease in cerebral blood flow (CBF). It is also accompanied by a fall in arterial Pco 2 leading to uncertainty as to whether the cerebral vasoconstriction is totally or only in part caused by arterial hypocapnia. We tested the hypothesis that the increase in arterial Po 2 while O 2 was breathed at 1.0 ATA decreases CBF independently of a concurrent fall in arterial Pco 2 . CBF was measured in seven healthy men aged 21–62 yr by using noninvasive continuous arterial spin-labeled-perfusion MRI. The tracer in this technique, magnetically labeled protons in blood, has a half-life of seconds, allowing repetitive measurements over short time frames without contamination. CBF and arterial blood gases were measured while breathing air, 100% O 2 , and 4 and 6% CO 2 in air and O 2 backgrounds. Arterial Po 2 increased from 91.7 ± 6.8 Torr in air to 576.7 ± 18.9 Torr in O 2 . Arterial Pco 2 fell from 43.3 ± 1.8 Torr in air to 40.2 ± 3.3 Torr in O 2 . CBF-arterial Pco 2 response curves for the air and hyperoxic runs were nearly parallel and separated by a distance representing a 28.7–32.6% decrement in CBF. Regression analysis confirmed the independent cerebral vasoconstrictive effect of increased arterial Po 2 . The present results also demonstrate that the magnitude of this effect at 1.0 ATA is greater than previously measured.
Type of Medium:
Online Resource
ISSN:
8750-7587
,
1522-1601
DOI:
10.1152/japplphysiol.00303.2003
Language:
English
Publisher:
American Physiological Society
Publication Date:
2003
detail.hit.zdb_id:
1404365-8
SSG:
12
SSG:
31
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