INTRODUCTION: Transthoracic echocardiography (TTE) is a useful tool for minimally invasive hemodynamic monitoring in the ICU. Dynamic indices (such as the inferior vena cava distensibility index (dIVC)) can be used to predict fluid responsiveness in mechanically ventilated patients. Although quantitative use of the dIVC has been validated, the routinely used qualitative (visual) approach had not been assessed prior to the present study. METHODS: Qualitative and quantitative assessments of the dIVC were compared in a prospective, observational study. After operators with differing levels in critical care echocardiography had derived a qualitative dIVC, the last (expert) operator performed a standard, numerical measurement of the dIVC (referred to as the quantitative dIVC). Two groups of patients were separated in two groups: group (dIVC < 18%) and group (dIVC >= 18%). RESULTS: A total of 114 patients were assessed for inclusion and 97 (63 men and 34 women) were included. The mean sensitivity and specificity values for qualitative assessment of the dIVC by an intensivist were 80.7% and 93.7%, respectively. A qualitative evaluation detected all quantitative dIVCs over 40%. Most of the errors concerned quantitative dIVCs of between 15% and 30%. In the dIVC < 18% group, two qualitative evaluation errors were noted for quantitative dIVCs of between 0% and 10%. The average of positive predictive values and negative predictive values for qualitative assessment of the dIVC by residents, intensivists and cardiologists were respectively 83%, 83% and 90%; and 92%, 94% and 90%. Fleiss' kappa for all operators was estimated to be 0.68, corresponding to substantial agreement. CONCLUSION: The qualitative dIVC is a rather easy and reliable assessment for extreme numerical values. It has a gray zone between 15% and 30%. The highest and lowest limitations of the gray area are rather tedious to define.Despite reliability of the qualitative assessment when it comes to extreme to numerical values, the quantitative dIVC measurement must always be done within a hemodynamic assessment for intensive care patients. The qualitative approach can be easily integrated into a fast hemodynamic evaluation using portable ultrasound scanner for out of hospital patients.