Validation of real-time continuous perfusion measurement

Perfusion, the rate at which blood in tissue is replenished at the capillar y level, is a primary factor in the transport of heat, drugs, oxygen and nu trients. While there have been many measurement techniques proposed, most d o not lend themselves to routine, continuous and real-time use. A minimally invasive probe, called the thermal diffusion probe (TDP), which uses a sel f-heated thermistor to measure absolute perfusion continuously and in real time, was validated at low flows with the microsphere technique. In 27 rabb its, simultaneous TDP measurements were made in liver from 0 to 60 ml min(- 1) 100 g(-1). The TDP perfusion correlated well with the microspheres (R-2 = 0.898) and the agreement between techniques is very good with a slope clo se to unity (0.921) and an intercept close to zero (0.566 ml min(-1) 100 g( -1)). Variability between the two techniques was primarily due to the sampl ing error from the microsphere 'snap shot' of periodic blood flow when comp ared with the continuous TDP perfusion measurement. The ability to quantify local perfusion continuously and in real time may have a profound impact o n patient management in a number of clinical areas such as organ transplant ation, neurosurgery, oncology and others, in which quantitative knowledge o f perfusion is of value.