Continuous, long term monitoring of IVC size and collapsibility indexes during simulated blood volume challenges

Inferior vena cava (IVC) size and collapsibility indices are frequently examined to provide rapid and non-invasive indications of volemic status, although numerous factors reduce their clinical applicability. This is achieved through single-time assessments, which provide a very poor time resolution. This is insufficient to describe the intrinsic variability of the signals and inadequate to follow both the fast and slow hemodynamic changes associated with specific maneuvers or therapeutic interventions. Recent technological improvements in ultrasound (US) imaging and in image processing speed now allow automatic measurement of vessel size and calculation of real-time indices. With the addition of procedural tricks, like the adoption of dedicated holders for the US probes, long-lasting continuous monitoring of IVC size can be obtained. This allows for improved understanding of hemodynamic transients and the time course of changes in cardiovascular variables in response to physical/pharmacological interventions, with particular reference to blood volume distribution and central venous filling. In the present paper, the methodology is described, a few recordings from ongoing studies are presented as proof of concept, and the implications for cardiovascular research, along with possible clinical applications, are discussed.