IMPROVEMENT OF INDICATOR DILUTION-BASED CAPILLARY FLOW ESTIMATION BY SENSITIVITY ANALYSIS.

The sensitivity of indicator dilution measurement of capillary perfusion rate to errors in the experimental variables was studied. Parameter sensitivity analysis and models based on a diffusion equation with a capillary-level convection term were used. The sensitivity analysis is based on normalized partial derivatives of indicator concentration with respect to experimental variables (time, position, etc. ). Results for washout models commonly employed in flow analysis produced some striking findings. The sensitivity of a perfusion estimate to errors in measured indicator concentration is orders of magnitude higher than it is to other variables in the material balance. The best estimate of perfusion can be shown to occur at predictable times in the washout period. Those variables yielding the highest sensitivity to error in the perfusion estimate can be identified in this manner and the protocol designed accordingly to minimize that error.