Respiratory-induced changes in arterial blood pressure predict fluid responsiveness. However, the accuracy of these variables is affected by the preset tidal volume and by the early inspiratory increase in arterial blood pressure. We have therefore calculated the slope produced by the minimal systolic blood pressures (plotted against the respective airway pressures) during a ventilatory maneuver consisting of four incremental, successive, pressure-controlled breaths, termed the Respiratory Systolic Variation Test (RSVT). In 14 ventilated patients, after major vascular surgery, the slope of the RSVT decreased significantly after intravascular fluid administration and correlated with the end-diastolic area and with changes in cardiac output better than filling pressures. This preliminary study suggests that a standardized ventilatory maneuver may be useful in guiding fluid therapy in ventilated patients.