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MRI of cerebral blood flow under hyperbaric conditions in rats
Author(s) -
Cardenas Damon P.,
Muir Eric R.,
Duong Timothy Q.
Publication year - 2016
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3555
Subject(s) - cerebral blood flow , hypercapnia , oxygen , blood flow , anesthesia , blood oxygen level dependent , chemistry , vasoconstriction , respiration , medicine , magnetic resonance imaging , acidosis , anatomy , organic chemistry , radiology
Hyperbaric oxygen (HBO) therapy has a number of clinical applications. However, the effects of acute HBO on basal cerebral blood flow (CBF) and neurovascular coupling are not well understood. This study explored the use of arterial spin labeling MRI to evaluate changes in baseline and forepaw stimulus‐evoked CBF responses in rats ( n = 8) during normobaric air (NB), normobaric oxygen (NBO) (100% O 2 ), 3 atm absolute (ATA) hyperbaric air (HB) and 3 ATA HBO conditions. T 1 was also measured, and the effects of changes in T 1 caused by increasing oxygen on the CBF calculation were investigated. The major findings were as follows: (i) increased inhaled oxygen concentrations led to a reduced respiration rate; (ii) increased dissolved paramagnetic oxygen had significant effects on blood and tissue T 1 , which affected the CBF calculation using the arterial spin labeling method; (iii) the differences in blood T 1 had a larger effect than the differences in tissue T 1 on CBF calculation; (iv) if oxygen‐induced changes in blood and tissue T 1 were not taken into account, CBF was underestimated by 33% at 3 ATA HBO, 10% at NBO and <5% at HB; (v) with correction, CBF values under HBO, HB and NBO were similar ( p > 0.05) and all were higher than CBF under NB by ~40% ( p < 0.05), indicating that hypercapnia from the reduced respiration rate masks oxygen‐induced vasoconstriction, although blood gas was not measured; and (vi) substantial stimulus‐evoked CBF increases were detected under HBO, similar to NB, supporting the notion that activation‐induced CBF regulation in the brain does not operate through an oxygen‐sensing mechanism. CBF MRI provides valuable insights into the effects of oxygen on basal CBF and neurovascular coupling under hyperbaric conditions. Copyright © 2016 John Wiley & Sons, Ltd.