Validation of the inferior vena cava collapsibility as a predictive marker of fluid responsiveness in spontaneously breathing patients

In a previous derivation cohort, we found that inferior vena cava collapsibility (cIVC) thresholds of ≥ 33% during non-standardised breathing (cIVC-ns) and ≥ 44% during a standardised breathing manoeuvre (cIVC-st) identified fluid responsiveness (FR). The aim of this study was to validate these findings through a secondary analysis of a prospective validation cohort. We measured cIVC-ns and cIVC-st in spontaneously breathing adult patients in a sub-xiphoid, long-axis view, using the two-dimensional mode, at 4 cm from the cavo-atrial junction. An increase in the subaortic time-velocity integral during a passive leg raising test (∆VTI) ≥ 10% was used to define FR. Among 61 intensive care unit (ICU) patients included, a cIVC-ns ≥ 33% predicted FR with a sensitivity and a specificity of 84% and 83%, respectively. A cIVC-st ≥ 44% predicted FR with a sensitivity and a specificity of 94% and 87%, respectively. A cIVC-ns ≥ 33% and a cIVC-st ≥ 44% misclassified 16.4% and 8.2% of the patients respectively (p = 0.06). Measuring cIVC is a reliable, non-invasive tool to predict FR in pontaneously breathing patients admitted to ICU. However, the clinical added value of a standardised breathing manoeuvre to improve its diagnostic accuracy warrants further investigation in dedicated studies.Trial registration: Name of the registry: Diagnostic Accuracy of the Central Venous Pressure (CVP) Variation to Predict Fluid Responsiveness in Spontaneously Breathing Patients (VPVC). Trial registration number: NCT03780660.