Estimating total cerebral blood flow from the initial slope of hydrogen washout curves.

An initial slope index of total cerebral blood flow, measured by the hydrogen clearance technique, shows a high correlation with flows calculated by bicompartmental analysis. In 247 flow measurements done on 41 rhesus monkeys, a linear regression analysis between these two methods of calculating flow shows a correlation coefficient of 0.928 with a standard error about y values of plus or minus 7.63. The initial slope index is not only faster but does not require that a steady state be maintained for ten minutes.