Principal investigator Nikolai M. Krivitski, Ph.D., D.Sc., led the Transonic Systems team in developing a novel ultrasound method of comparing blood flow in dialysis tubing with the machine' s pump flow setting. A discrepancy between actual blood flow and the setting indicates an obstruction somewhere in the circuit, a problem that can lead to hemolysis and inadequate dialysis. The system uses ultrasound sensors that clip onto the tubes carrying blood to and from the dialysis machine. The system also introduces saline into the tube that carries blood back to the patient. The saline dilutes the blood and reduces the velocity of ultrasound waves.
Sensors can then detect diluted blood that recirculates from the patient back into the tubing.
The system calculates access flow by reversing the normal direction of blood flow and then using the arterial sensor to measure reverse recirculation. The system can also measure cardiac output with blood flowing in the normal direction through the tubing. In 1998, FDA approved the system for measuring cardiac output. The system can help dialysis clinic staff detect problems with access patency, dialysis adequacy, and cardiac output. The ultrasound dilution methodology has been cited numerous times in the literature on vascular access problems in hemodialysis and is mentioned in the Dialysis Outcomes Quality Initiative vascular access guidelines.