SBIR-STTR Award

The objective of this study is to develop a system for continuously monitoring cardiac output by the use of Doppler ultrasound from the esophagus.The principle of operation is that blood velocity at the measurement site, the transverse aorta, will be proportional to the blood flow. It has already been demonstrated that continuous wave Doppler can accurately assess stroke volume in man. Recent studies by others have shown that flow velocities can be detected by pulsed Doppler sensors from the esophagus. Experiments are planned to quantify the requirements for an esophageal probe design and placement technique so as to be able to continuously monitor such flow.The grantee has several specific objectives: 1) development of a continuous wave esophageal transducer system; 2) testing of this system in animals under conditions similar to clinical situations to verify operation and refinement of placement technique; 3) perform any necessary refinements of the transducer and system; and 4) evaluate the system in 20 human subjects in the intensive care unit and operating room. The objective of the clinical evaluations is to further refine the design of the system, to assess the feasibility of the technique in clinical settings, and to provide the basis for a more extensive evaluation to assess the efficacy of the technique and to develop patient care applications.National Heart, Lung and Blood Institute

The purpose of this research is to optimize a system for continuously monitoring cardiac output and systemic vascular resistance by the use of Doppler ultrasound from the esophagus, to evaluate the accuracy of the technique, and to demonstrate its clinical utility in patient management.This will be accomplished by: (1) quantifying the anatomical relationship between the esophagus and the ultrasonically accessible portions of the ascending and transverse aorta in humans using commercially available pulsed-Doppler ultrasound imaging equipment; (2) developing a measurement system optimized for human anatomy; (3) evaluating the accuracy in humans by comparison with alternative techniques; (4) determining the effect of large variations of afterload, preload, and contractility on the relationship between the esophageal measurement and conventional methods using a dog model; and (5) evaluating the system efficacy in patient management through the development and testing of patient management protocols based on the use of continuous hemodynamic monitoring.This work will provide a substitute for higher risk methods of cardiac diagnosing and will provide the physician a means to continuously monitor hemodynamics while titrating drugs or inducing anesthesia, and will greatly enhance the physician's ability to manage the anesthetized patient.National Heart, Lung, And Blood Institute