Article
In vitro performance of six different combinations of adjustable differential pressure valves and fixed anti siphon devices with and without vertical motion
In-vitro-Flusseigenschaften von sechs verschiedenen Kombinationen verstellbarer Differenzdruckventile mit fixen Anti-Siphon-Ventilen mit und ohne vertikale Bewegung
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Authors
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Ingo Fiss
- Universitätsmedizin Göttingen, Neurochirurgie, Göttingen, Deutschland
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Pauline Röhrig
- Universitätsmedizin Göttingen, Neurochirurgie, Göttingen, Deutschland
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Florian Freimann
- Universitätsmedizin Göttingen, Neurochirurgie, Göttingen, Deutschland
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Ulrich-Wilhelm Thomale
- Charité – Universitätsmedizin Berlin, Klinik für Neurochirurgie, Berlin, Deutschland
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Michael Buchfelder
- Universitätsklinikum Erlangen, Neurochirurgie, Erlangen, Deutschland
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Veit Rohde
- Universitätsmedizin Göttingen, Neurochirurgie, Göttingen, Deutschland
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Sebastian Brandner
- Universitätsklinikum Erlangen, Neurochirurgie, Erlangen, Deutschland
| Published: | May 8, 2019 |
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Outline
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Objective: Adjustable differential pressure valves in combination with fixed anti siphon devices are currently the most popular combination to counteract the effects of cerebrospinal fluid overdrainage after implantation of a shunt system. The study examined the flow performance of three different different pressure valves (Codman Hakim programmable valve, Codman CertasPlus and Miethke proGAV) in successive combination with a hydrostatic valve (either Codman SiphonGuard [SG] or Miethke Shuntassistant [SA]) in an in vitro shunt laboratory with and without vertical motion.
Methods: We analyzed three differential pressure valves in combination with either a gravitational unit (SA) or a siphon regulatory device (SG), thus six different valve combinations were evaluated. Defined pressure conditions within a simulated shunt system were generated (differential pressure 4–40 cmH2O) and the specific flow characteristics were measured. In addition, combinations with gravity-dependent SA were measured in defined spatial positions (90°, 60°). All device combinations were tested under vertical motion with movement frequencies of 2, 3, and 4 Hz. Statistical analysis was performed using one-way ANOVA, followed by Tukey’s multiple comparison test.
Results: All valve combinations effectively counteracted the hydrostatic effect in relation to the chosen differential pressure. Angulation-related flow changes were similar in the three SA-device combinations in the 60° and 90° device position. Repeated vertical movement at a differential pressure of 40 cm H2O significantly increased flow through all device combination with an SA (difference in flow: proGAV 90°: 0.94±0.31, 60°: 0.71±0.27; Hakim 90°: 0.66±0.38, 60°: 0.41±0.24; CertasPlus 90°: 0.94±0.21, 60°: 0.79±0.16 ml/min; p<0.01); in combination with an SG, only CertasPlus and Hakim (0.17±0.04 and 0.17±0.02 ml/min; p<0.01), but not proGAV (0,11±0.05 ml/min, p=0,48) showed increased flow.
Conclusion: In a static setup, all valve combinations effectively counteracted the hydrostatic effect according to their added resistance in vertical position. Motion-induced increased flow was demonstrated in device combination with an SA. In combinations with an SG, the induced flow was much more depending on the applied differential pressure and setting of the respective valve. The measured changed flow rates should be taken into account when selecting appropriate valves and settings in active shunt patients.
