In vitro analysis of thermal transport in coronary sinus thermodilution catheters.

The continuous thermodilution technique for measuring blood flow in the range 50-300 ml/min was evaluated in vitro. Experiments indicated that thermotransport within the catheter from the indicator line to the mixing thermistor exists. The resulting error in calculated thermodilution flow will increase with increasing flow rate. A correction factor for thermal transport, Ft, obtained from a blood circulation model was incorporated in a modified formula for calculation of thermodilution flow. Flows derived with the standard Ganz formula were significantly lower than timed volumetric flows, whereas flows obtained with the modified formula agreed with volumetric flow. The coefficient of variation for four consecutive measurements was 3.4%.