The mechanism of cerebral autoregulation is still open to discussion . One important factor involved is described by the myogenic theory. From our recent experimental work dealing with the influence of extracorporeal circulation upon CBF and cerebral metabolism we obtained results which, we think, support the myogenic theory. The term autoregulation in its restricted sense describes the intrinsic ability of cerebral circulation to maintain a constant blood flow at varying perfusion pressures. This fact is usually demonstrated in the familiar pressure-flow diagram, where CBF is plotted against an arbitrary mean pressure. This procedure however neglects the fact that normal blood pressure is pulsatile. If one agrees to the concept of transmural pressure as the important factor in myogenic autoregulation a different response to normal pulsatile and to a constant non-pulsatile perfusion pressure can be expected.
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