In vitro performance of six combinations of adjustable differential pressure valves and fixed anti-siphon devices with and without vertical motion

• Published in: Acta neurochirurgica 2020-10, Vol.162 (10), p.2421-2430
• Main Authors: Fiss, I., Röhrig, P., Hore, N., von der Brelie, C., Bettag, C., Freimann, F. B., Thomale, U.-W., Rohde, V., Brandner, S.
• Format: Article
• Language: English
• Subjects: Cerebrospinal fluid; CSF Circulation; Gravitation; Humans; Hydrocephalus - surgery; Interventional Radiology; Medicine; Medicine & Public Health; Minimally Invasive Surgery; Motion; Neurology; Neuroradiology; Neurosurgery; Original Article - CSF Circulation; Pressure; Prostheses and Implants - adverse effects; Prostheses and Implants - standards; Surgical Orthopedics; Valves; Ventriculoperitoneal shunt; Ventriculoperitoneal Shunt - instrumentation
• ISSN: 0001-6268; 0942-0940
• DOI: 10.1007/s00701-020-04519-y

Objective Adjustable differential pressure (DP) valves in combination with fixed anti-siphon devices are currently a popular combination in counteracting the effects of cerebrospinal fluid overdrainage following implantation of a ventriculoperitoneal shunt system. The study examined the flow performance of three DP valves in successive combination with an anti-siphon device in an in vitro shunt laboratory with and without vertical motion. Methods We analyzed three DP valves (Codman Hakim Medos programmable valve [HM], Codman CertasPlus [CP], and Miethke proGAV [PG], in combination with either Codman SiphonGuard [SG] or Miethke ShuntAssistant [SA]), resulting in the evaluation of six different valve combinations. Defined DP conditions between 4 and 40 cm H 2 O within a simulated shunt system were generated and the specific flow characteristics were measured. In addition, combinations with SA, which is a gravity-dependent valve, were measured in defined spatial positions (90°, 60°). All device combinations were tested during vertical motion with movement frequencies of 2, 3, and 4 Hz. Results All valve combinations effectively counteracted the siphon effect in relation to the chosen DP. Angulation-related flow changes were similar in the three combinations of DP valve and SA in the 60° and 90° position. In CP-SA and PG-SA, repeated vertical movement at 2, 3, and 4 Hz led to significant increase in flow, whereas in HM-SA, constant increase was seen at 4 Hz only (flow change at 4Hz, DP 40 cm H 2 O: PG (opening pressure 4 cm H 2 O) 90°: 0.95 ml/min, 60°: 0.71 ml/min; HM (opening pressure 4 cm H 2 O) 90°: 0.66 ml/min, 60°: 0.41 ml/min; CP (PL 2) 90°: 0.94 ml/min, 60°: 0.79 ml/min; p < 0.01); however, HM-SA showed relevant motion-induced flow already at low DPs (0.85 ml/min, DP 4 cm H 2 O). In combinations of DP valve with SG, increase of flow was far less pronounced and even led to significant reduction of flow in certain constellations. Maximum overall flow increase was 0.46 ± 0.04 ml/min with a HM (opening pressure 12 cm H 2 O) at 2 Hz and a DP of 10 cm H 2 O, whereas maximum flow decrease was 1.12 ± 0.08 with a PG (opening pressure 4 cm H 2 O) at 3 Hz and a DP of 10 cmH 2 O. Conclusion In an experimental setup, all valve combinations effectively counteracted the siphon effect in the vertical position according to their added resistance. Motion-induced increased flow was consistently demonstrated in combinations of DP valve and SA. The combination of HM and SA