Estimating medullary chemoreceptor blood flow from ventilatory-CO2 response transients: theory and data from anesthetized dogs.

We examined the tracer wash-in technique for measuring blood flow for a specific experimental model in which medullary chemoreceptor blood flow is estimated using carbon dioxide as the tracer. Using a mathematical model, we calculated the flow values that would be estimated when blood flow is a function of the tracer concentration, CO2. The estimate was compared with three indices of time-varying blood flow: the steady-state blood flow before and after the step change of CO2 and the time-average blood flow. Estimated blood flow was found to be most closely related to the final value of flow. Perfusion estimates from five pentobarbital anesthetized dogs were 102 ml/100 g/min (S.D. 35) at an average of PaCO2 of 60.7 Torr.