An In Vitro and In Vivo Study of the Detection and Reversal of Venous Collapse During Extracorporeal Life Support

Abstract

The objective of this study was to investigate venous collapse (VC) related to venous drainage during the use of an extracorporeal life support circuit. A mock circulation was built containing a centrifugal pump and a collapsible vena cava model to simulate VC under controlled conditions. Animal experiments were performed for in vivo verification. Changing pump speed had a different impact on flow during a collapsed and a distended caval vein in both models. Flow measurement in combination with pump speed interventions allows for the detection and quantitative assessment of the degree of VC. Additionally, it was verified that a quick reversal of a VC situation could be achieved by a two-step pump speed intervention, which also proved to be more effective than a straightforward decrease in pump speed.

Dynamic filling index: a novel parameter to monitor circulatory filling during minimized extracorporeal bypass

“…4) was the result of substantial cannula obstruction and/ or caval vein occlusion with extreme luxation. In a previous study, we showed that such a decrease in the DFI is indicative of insufficient volume available for drainage [11]. The present study demonstrates that even small changes in DV can be detected by DFI measurement.…”

“…Although the effect of luxating the heart created reproducible changes in DFI, we did not obtain in our patients alternative evidence for the absolute changes in DV. In previous studies performed under well-controlled conditions we have demonstrated that the DFI responds straightforwardly to caval vein constriction and changes in transmural pressure at the drainage site [11]. The DFI may also be affected by a change in arterial line pressure.…”

“…In previous laboratory studies, we found that the relationship between bypass flow and pump speed in a minimized perfusion setup is modulated by venous return and DV [10,11]. Fig.…”

Reserve-driven flow control for extracorporeal life support: proof of principle

“…The loops illustrate that resolving impaired drainage due to inappropriate pump speed (plateau in the curve) firstly requires a speed reduction, after which an increase of pump speed will restore the balance between venous return and venous drainage. 10 In a recent study, we demonstrated that small changes in DV, as reflected by the slope of the speed-flow curve (Figure 1 right) can be determined by measuring the dynamic filling index (DFI). 12 This index proved more sensitive to changes in DV than direct haemodynamic and pump-related parameters.…”

Quantitative assessment of cardiac load-responsiveness during extracorporeal life support: case and rationale

“…Recently, we developed a technique to quantitatively assess venous volume that can be (potentially) drained by the centrifugal pump-based ELS circuit, and introduced the dynamic filling index (DFI, in ml/rotation) for the purpose of optimizing ELS flow [6-8]. DFI measurement uses periodical, transient reductions (-100 rpm) of pump speed, each lasting approximately 10 seconds, superimposed on the steady state pump speed.…”