Brain tissue oxygen concentration measurements.
Brain function depends exquisitely on oxygen for energy metabolism. Measurements of brain tissue oxygen tension, by a variety of quantitative and qualitative techniques, going back for >50 years, have led to a number of significant conclusions. These conclusions have important consequences for understanding brain physiology as it is now being explored by techniques such as blood-oxygen-level-dependent functional magnetic resonance imaging (BOLD fMRI) and near-infrared spectroscopy (NIRS). It has been known for some time that most of the measured oxygen tensions are less than venous pO2 and are distributed in a spatially and temporally heterogeneous manner on a microregional scale. Although certain large-scale methods can provide reproducible average brain pO2 measurements, no useful concept of a characteristic oxygen tension or meaningful average value for brain tissue oxygen can be known on a microregional level. Only an oxygen field exists with large local gradients due to local tissue respiration, and the most useful way to express this is with a pO2 distribution curve or histogram. The neurons of the brain cortex normally exist in a low-oxygen environment and on activation are oxygenated by increases in local capillary blood flow that lead to increases in hemoglobin saturation and tissue oxygen.
Ndubuizu
Obinna
O
Department of Physiology and Anatomy, Case Western Reserve University, Cleveland, Ohio 44106-4930, USA.
LaManna
Joseph C
JC
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002196:Capillaries / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D049449:Luminescence; D008279:Magnetic Resonance Imaging / Q000379:methods*; D013058:Mass Spectrometry; D008954:Models, Biological; D010092:Oximetry / Q000295:instrumentation / Q000379:methods*; D010100:Oxygen / Q000097:blood / Q000378:metabolism*; D011048:Polarography / Q000379:methods; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013997:Time Factors
D006454:Hemoglobins; D010100:Oxygen