Cardiac output measurement by pulse dye densitometry using three wavelengths

OBJECTIVES Pulse dye densitometry (PDD), based on the principles of pulse oximetry and dye-dilution technique, is a less invasive method of measuring cardiac output (CO). We have developed prototype equipment to measure CO in pediatric patients using this technique. The purpose of our study was to evaluate the accuracy of this new PDD system using three wavelengths for pediatric application by comparing measurement with an ultrasound flowmeter. DESIGN Laboratory investigation. SETTING Hospital physiology research laboratory. SUBJECTS A total of 15 young piglets weighing approximately 10 kg each. INTERVENTIONS Measurement of CO by PDD was performed using general anesthesia. Indocyanine green, 0.2 mg/kg, was administered intravenously, and CO was calculated from the dye dilution curve obtained by the PDD system. The ultrasound flowmeter probe was placed on the ascending aorta in the animal, and CO was simultaneously calculated. MEASUREMENTS AND MAIN RESULTS The two CO values, simultaneously obtained by the ultrasound flowmeter and PDD, were compared during various hemodynamic states. The bias between the CO measured by the ultrasound flowmeter and the CO measured by the PDD system using the reflection-type probe at the central site was 33.8 mL/min and the precision was 293.4 mL/min, indicating that CO measured by PDD had a good correlation with measurements obtained with the ultrasonic method. CONCLUSION We measured CO in young piglets at an acceptable level of bias and precision using a prototype PDD device. CO measurement by this new PDD system using three wavelengths can be useful and beneficial for critically ill infants and children. It is simple to perform, requiring an injection of dye into a peripheral intravenous catheter, and it will provide a less invasive bedside measurement of CO.