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Tissue viability represents the balance between O2 supply and demand. In our previous paper (Mayevsky et al;
Proc.SPIE 6083 : z1-z10, 2006) the HbO2 was added to the multiparametric tissue spectroscope (Mayevsky et al
J.Biomedical Optics 9:1028-1045,2004). This parameter provides relative values of microcirculatory blood oxygenation
(MC-HbO2) evaluated by the 2 wavelength reflectometry principle. The advantage of this approach as compared to pulse
oximetry is that the measurement is not dependent of the existence of the pulse of the heart. Also in the MC-HbO2 the
information is collected from small vessels providing O2 to the mitochondria as compared to the pulse oximeter
indicating blood oxygenation by the respiratory and cardiovascular systems.
In the present study we compared the level of blood oxygenation measured by the pulse oximeter to that measured by the
CritiView in the brain exposed to various systemic and localized perturbations of O2 supply or demand. We exposed
gerbils to anoxia, hypoxia, ischemia and terminal anoxia. In addition we measured mitochondrial NADH (surface
fluorometry), tissue reflectance, tissue blood flow (laser Doppler flowmetry) from the same site of MC-HbO2
measurement.
A clear connection was found between the two blood oxygenation parameters only when systemic perturbations were
used (anoxia, hypoxia and terminal anoxia). Under local events (ischemia) the MC-HbO2 was responsive while the
systemic oxygenation was unchanged. We concluded that MC-HbO2 has a significant value in interpretation of tissue
energy metabolism under pathophysiological conditions.
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