Cerebral Blood Flow Determined by Saturation and Desaturation with Krypton-85: an Evaluation of the Validity of the Inert Gas; Method of Kety and Schmidt.

• In the original inert gas method of Kety and Schmidt the saturation of the brain with the inert gas, N,,O, is followed for 10 minutes. In a group of subjects we have studied both the saturation and the desaturation of the brain with krypton as the inert gas. The results give an experimental demonstration of a relatively small systematic error inherent in the method apparently due to differences of the uptake rate of inert gas in the various cerebral tissues. The error is discussed with particular emphasis on the use of extrapolation to infinity for the purpose of counteracting it.