Monitoring of right ventricular function using a conventional slow response thermistor catheter

Objective: To investigate whether determination of right ventricular end-diastolic volume (RVEDV) and right ventricular ejection fraction (RVEF) can be performed with reasonable accuracy and reproducibility using a conventional slow response thermistor pulmonary artery catheter (CPAC) applying an adaptive algorithm. Design: To study RVEDV and RVEF simultaneously with pulmonary artery catheters equipped with slow and fast response thermistors (FRPAC) under a broad range of cardiac output. Setting: Laboratory of Institute of Experimental Surgery, Technical University. Animals: 11 anaesthetised piglets. Interventions: Hypovolemia (V-) was induced by withdrawal of blood up to 50 ml/kg, hypervolemia (V+) was produced by retransfusing blood and adding up to 30 ml/kg hydroxyethyl starch. In 5 animals in phases V-and V+ beta-adrenergic stimulation was achieved with dobutamine. Finally pulmonary artery hypertension was induced by infusion of small air bubbles. Measurements and results: Cardiac output (CO), RVEDV and RVEF were determined simultaneously with FRPAC and CPAC placed in the same pulmonary artery branch. Measurements were repeated 8 times sequentially in steady state normovolemia. A total of 130 measurements could be analysed. The coefficient of variation was 6.7±4.2 for CO_(FRPAC) and 4.6±1.7% for CO_(CPAC); for RVEF it was 9.7±6.2% (FRPAC) and 9.9±3.9% (CPAC); for RVEDV it was 11.6±4.8% (FRPAC) and 8.54±3.2 (CPAC). Mean difference (bias) was 0.06±0.39 l/min for CO measured with both methods, 19±35 ml for RVEDV and -3.3±6.5% for RVEF. CO_(CPAC) displayed a strong correlation to CO_(FRPAC) (R=0.97, p=0.001) as well as RVEF (R for RVEF_(CPAC) versus RVEF_(FRPAC)=0.90, p=0.001). R for RVEDV_(CPAC) versus RVEDV_(FRPAC) was 0.67, p=0.001. We conclude that this animal study demonstrates good agreement between RVEF and RVEDV obtained with catheters equipped with a fast response thermistor or with a conventional slow response thermistor allowing accurate monitoring of right ventricular function with a conventional pulmonary artery catheter.