Continuous Cardiac Output Monitoring with a Central Venous Catheter Ultrasound Sensor

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PROJECT SUMMARY The goal of this research is to develop an innovative device to improve patient treatment in intensive care: a central venous catheter (CVC) that will provide continuous measurement of cardiac output (CO) using a unique Doppler ultrasound technology. Continuous measurements of CO in critically ill patients will transform modern intensive care, by allowing clinicians to direct clinical care moment-to-moment in each patient based on their individual pathophysiology. The proposed transformational technology adds no added risk and little incremental cost, while having the potential to become the standard of care for many of the seven million central lines placed annually in the USA alone. Cardiac output is a highly desired measurement, yet there are no continuous cardiac output measurement systems that have become accepted standards of care in intensive care units. This is due to safety risks from invasive methods such as the Swan-Ganz catheter or the inaccuracy of non-invasive or indirect methods. The system we propose will directly measure cardiac output in the ascending aorta using a novel, double-beam, side- looking diffraction-grating Doppler ultrasound transducer coated on the external surface of a central venous catheter. As noted earlier, this system will add no additional risk for patients in the ICU who already have a CVC inserted and positioned within the superior vena cava (SVC). Innovative aspects of this research include 1) Measuring arterial flow using a Doppler transducer in an adjacent vein (in this case, flow in the ascending aorta from a position within the SVC where the two are in apposition -- but potentially useful wherever artery-vein pairs occur); 2) Applying unique flexible piezopolymer thin-film ultrasound Doppler diffraction-grating transducers onto a central venous catheter; 3) Using two such Doppler transducers to cancel the effect of catheter angle in Doppler flow measurements (i.e., catheter motion within the superior vena cava caused by pulsatile blood flow, patient motion, etc.). The Doppler signals will be used to indicate and establish the correct position of the catheter within the SVC. The Specific Aims of the proposed research are: Aim 1: Design and fabricate double-beam thin-film Doppler transducer arrays designed to be able to measure blood flow in the aorta while swinging freely in the SVC, a blood vessel-to-blood vessel measurement configuration that is unprecedented. Existing Doppler electronics will be modified for the new catheters. Aim 2: Validate that the system resulting from Aim I is at least as accurate as Pulmonary Artery Catheters (Swan- Ganz catheters) when tested in flow phantoms that mimic the anatomy where central lines are placed. Aim 3: Demonstrate in living porcine models that a hybrid central line/cardiac output device is easily positioned, safe, and at least as accurate and precise as a simultaneously used PAC, in-line transit-time flowmeter and transesophageal monitors.