Using Heart-Lung Interactions for Functional Hemodynamic Monitoring: Important Factors beyond Preload

Abstract

The basic mechanism underlying functional preload indices, such as stroke volume variation (SVV), pulse pressure variation (PPV), or systolic pressure variation (SPV), is that mechanical ventilation induces cyclic alterations in ventricular filling and, in consequence, in stroke volume and cardiac output. This phenomenon is most easily recognized in clinical practice as periodical variations in the arterial pressure signal. Based on the understanding of the Frank-Starling-relationship, i.e., the relation of cardiac preload and stroke volume, the ventilation-synchronous variations of cardiac output, or the indices named above, which serve as surrogates, allow assessment of left ventricular (LV) filling, and, more importantly the evaluation of the steepness of the patient-individual LV function curve [1]. The usefulness of these functional preload indices in assessing cardiac preload and in predicting whether a patient will respond to fluid administration with an increase in cardiac output (fluid responsiveness) has been demonstrated in many studies.