A model for the regulation of cerebral oxygen delivery

• Published in: Journal of applied physiology (1985) 1998-08, Vol.85 (2), p.554-564
• Main Authors: Hyder, Fahmeed, Shulman, Robert G, Rothman, Douglas L
• Format: Article
• Language: English
• Subjects: Algorithms; Anatomy & physiology; Anesthesia; Animals; Biological and medical sciences; Blood Volume - physiology; Brain; Brain Chemistry - physiology; Capillary Permeability - physiology; Cerebral circulation. Blood-brain barrier. Choroid plexus. Cerebrospinal fluid. Circumventricular organ. Meninges; Cerebrovascular Circulation - physiology; Circulatory system; Fundamental and applied biological sciences. Psychology; Hemoglobins - metabolism; Humans; Magnetic Resonance Imaging; Models, Biological; Oxygen; Oxygen - blood; Oxygen Consumption - physiology; Rats; Regression Analysis; Vertebrates: nervous system and sense organs
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.1998.85.2.554

Departments of 1  Molecular Biophysics and Biochemistry and 2  Diagnostic Radiology, Yale University, New Haven, Connecticut 06510 On the basis of the assumption that oxygen delivery across the endothelium is proportional to capillary plasma P O 2 , a model is presented that links cerebral metabolic rate of oxygen utilization (CMR O 2 ) to cerebral blood flow (CBF) through an effective diffusivity for oxygen (D) of the capillary bed. On the basis of in vivo evidence that the oxygen diffusivity properties of the capillary bed may be altered by changes in capillary P O 2 , hematocrit, and/or blood volume, the model allows changes in D with changes in CBF. Choice in the model of the appropriate ratio of    ( D/D)/( CBF/CBF) determines the dependence of tissue oxygen delivery on perfusion. Buxton and Frank ( J. Cereb. Blood Flow. Metab. 17: 64-72, 1997) recently presented a limiting case of the present model in which  = 0. In contrast to the trends predicted by the model of Buxton and Frank, in the current model when > 0, the proportionality between changes in CBF and CMR O 2 becomes more linear, and similar degrees of proportionality can exist at different basal values of oxygen extraction fraction. The model is able to fit the observed proportionalities between CBF and CMR O 2 for a large range of physiological data. Although the model does not validate any particular observed proportionality between CBF and CMR O 2 , generally values of ( CMR O 2 /CMR O 2 )/( CBF/CBF) close to unity have been observed across ranges of graded anesthesia in rats and humans and for particular functional activations in humans. The model's capacity to fit the wide range of data indicates that the oxygen diffusivity properties of the capillary bed, which can be modified in relation to perfusion, play an important role in regulating cerebral oxygen delivery in vivo. brain mapping; positron emission tomography; blood oxygenation level dependent; functional magnetic resonance imaging; blood; glucose; lactate; metabolism; perfusion; permeability; diffusivity; conductivity