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Published in: World Journal of Urology 5/2016

01-05-2016 | Original Article

The hydrodynamic basis of the vacuum cleaner effect in continuous-flow PCNL instruments: an empiric approach and mathematical model

Authors: R. Mager, C. Balzereit, K. Gust, T. Hüsch, T. Herrmann, U. Nagele, A. Haferkamp, D. Schilling

Published in: World Journal of Urology | Issue 5/2016

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Abstract

Purpose

Passive removal of stone fragments in the irrigation stream is one of the characteristics in continuous-flow PCNL instruments. So far the physical principle of this so-called vacuum cleaner effect has not been fully understood yet. The aim of the study was to empirically prove the existence of the vacuum cleaner effect and to develop a physical hypothesis and generate a mathematical model for this phenomenon.

Methods

In an empiric approach, common low-pressure PCNL instruments and conventional PCNL sheaths were tested using an in vitro model. Flow characteristics were visualized by coloring of irrigation fluid. Influence of irrigation pressure, sheath diameter, sheath design, nephroscope design and position of the nephroscope was assessed. Experiments were digitally recorded for further slow-motion analysis to deduce a physical model.

Results

In each tested nephroscope design, we could observe the vacuum cleaner effect. Increase in irrigation pressure and reduction in cross section of sheath sustained the effect. Slow-motion analysis of colored flow revealed a synergism of two effects causing suction and transportation of the stone. For the first time, our model showed a flow reversal in the sheath as an integral part of the origin of the stone transportation during vacuum cleaner effect. The application of Bernoulli’s equation provided the explanation of these effects and confirmed our experimental results.

Conclusions

We widen the understanding of PCNL with a conclusive physical model, which explains fluid mechanics of the vacuum cleaner effect.
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Metadata
Title
The hydrodynamic basis of the vacuum cleaner effect in continuous-flow PCNL instruments: an empiric approach and mathematical model
Authors
R. Mager
C. Balzereit
K. Gust
T. Hüsch
T. Herrmann
U. Nagele
A. Haferkamp
D. Schilling
Publication date
01-05-2016
Publisher
Springer Berlin Heidelberg
Published in
World Journal of Urology / Issue 5/2016
Print ISSN: 0724-4983
Electronic ISSN: 1433-8726
DOI
https://doi.org/10.1007/s00345-015-1682-5

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