Mathematical model of oxygen transport in the cerebral cortex.
To estimate the magnitude of hyperemia necessary to support oxidative metabolism in the cerebral cortex during functional activation, a mathematical model of O2 transport from capillary to tissue was developed. Radial and axial gradients of O2 pressure in tissue surrounding a single capillary were calculated at normal and increased cerebral metabolic rates for O2. Cone-shaped tissue geometry and nonlinear oxyhemoglobin dissociation were assumed. Local O2 consumption was assumed to be supported with local tissue pO2 greater than 1 mmHg. The distribution of tissue pO2 was also calculated during moderate hypoxemia (paO2=42 mmHg), using experimental values of red blood cell velocity measured in individual capillaries of the rat cerebral cortex using intravital video-microscopy. The model predicted that moderate increases (</=50%) in cerebral O2 consumption were supported by proportional increases in capillary blood flow. Large increases in O2 consumption (50-110%) were supported by disproportional increases in flow. During moderate hypoxemia, average tissue pO2 decreased but oxygen utilization was sustained when capillary flow was increased to a level measured in experiments. The results suggest a proportional relationship between cerebrocortical blood flow and oxygen consumption in the normal physiological range of functional activation.
Hudetz
A G
AG
Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.ahudetz@mcw.edu
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002540:Cerebral Cortex / Q000098:blood supply / Q000378:metabolism*; D004058:Diffusion; D008297:Male; D008433:Mathematics; D008833:Microcirculation / Q000502:physiology; D008959:Models, Neurological; D010100:Oxygen / Q000493:pharmacokinetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014741:Video Recording
D010100:Oxygen