A dynamic view of dynamic indices.

Dynamic indices (based on cardiopulmonary interactions in mechanically ventilated patients in sinus rhythm) have been developed as simple tools for predicting fluid responsiveness in the absence of cardiac output monitoring. Although the earliest dynamic indices relied on the invasive measurement of pulse pressure variations or stroke volume variations, the most recently developed indices are based on non-invasive photoplethysmography. However, a number of confounding factors have been found which decrease the clinical value of these indices. The present experts' opinion explains why changes in dynamic indices during hemodynamic maneuvers might be an interesting alternative to using them accurately at bedside.