Development and application of a logistic-based systolic model for hemodynamic measurements using the esophageal Doppler monitor.

The esophageal Doppler monitor (EDM) is a clinically useful device for minimally invasive assessment of cardiac output, preload, afterload, and contractility. An empirical model, based upon the logistic function, has been developed. Use of this model illustrates how the EDM could estimate the net effect of aortic and non-aortic contributions to inertia, resistance, and elastance within real time. This is based on an assumed mechanical impedance conceptually resembling that of a series arrangement of a spring, mass, and dashpot. In addition, when used with an invasive radial arterial catheter, the EDM may also estimate aortic pulse wave velocity, as well as aortic characteristic impedance, and characteristic volume. Approximations of left ventricular stroke work and stroke power can also be made. Furthermore, the effects of inertia, resistance, and elastance, on mean blood pressure during systole, can be quantified. These additional parameters could offer insight for clinicians, as well as researchers, and may be beneficial in further examining and utilizing clinical hemodynamics with the EDM. These additional measurements also underscore the need to integrate the EDM with existing and future monitoring equipment.