The importance of shunt valve position in flow characteristics of the Medtronic PS Medical Delta valve

Abstract

<jats:p>This study was conducted to document the extent to which flow depends on valve position in relation to head-pressure reference.</jats:p> <jats:p>Medtronic PS Medical Delta valves (contour model, performance levels 0.5, 1.0, 1.5, and 2.0) were studied in a bench test designed to evaluate flow rates with respect to valve position in relation to the head-pressure reference postion. The valves were connected to an “infinite” reservoir by the standard inlet catheter. An initial head (proximal) pressure was selected for each valve based on package insert data. The position of the inlet catheter tip was fixed at this starting head pressure, thus making the inlet catheter tip position the reference for relative head pressures on the valve assembly. When the valve body is positioned above this level, the effective head pressure is lowered, and when the valve body is positioned below this level, the effective head pressure is raised. Flow was established with the siphon control portion of the valve body located on the same horizontal level as the inlet catheter tip (the reference head pressure or “0” position). A standard silastic catheter was attached to the outlet of the valve, and its length was fixed at 50 cm for all valves (-50 cm H<jats:sub>2</jats:sub>0). The distal end of the outlet catheter was connected to a fraction collector, and 1-minute samples (five replicates) were collected for gravimetric determination of flow rate. The valve assembly was then moved in 1-cm increments through the range of 4 cm above to 8 cm below the head-pressure reference position. Samples were collected from each position (4 cm to -8 cm) relative to the inlet catheter tip. Flow rate, in milliliters/hour, was plotted against both relative position (4 cm to -8 cm) and absolute head pressure (in centimeters of water).</jats:p> <jats:p>Each of the valves tested was shown to have a linear relationship between flow and position relative to the inlet catheter tip (or absolute head pressure). The average increase in flow per centimeter of displacement of valve from catheter tip was 16.5 ml/hr/cm (range 14.4-17.6 ml/hr/cm). Once the inlet catheter tip is fixed in position, it serves as a pressure reference. Movement of the valve above this level results in a net decrease in effective head pressure, and movement below this position results in a net increase in effective head pressure. Thus, the positioning of shunt valves in locations different from this pressure reference position should be performed only with the knowledge that significant increases in outflow rate may occur when the valve body is positioned lower than the inlet catheter tip. This increase in outflow rate is not the result of siphoning or a defect in the antisiphon device but instead the result of a net increase in effective head pressure.</jats:p>

Ventriculoperitoneal shunt malfunction diagnosis based on substance dilution

“…When normal CSF flows through the reservoir, the high SV concentration in the reservoir is continuously diluted. [9,10] In contrast, when the VP shunt malfunctions, the SV in the reservoir cannot be quickly diluted.…”

Optimization of number and range of shunt valve performance levels in infant hydrocephalus: a machine learning analysis

“…These variables were employed in unsupervised machine learning analysis to optimize the number and range of valve performance levels. It should be noted that shunt valve performance levels were also converted to drainage pressure values according to the respective manufacturer’s catalogs when specific drainage pressures were not recorded in the operative reports ( Francel et al, 1999 ; Chong et al, 2002 ; Lollis et al, 2010 ; Czosnyka et al, 2013 ; Mirone et al, 2019 ; Skalický et al, 2022 ).…”

“…Hence, this study exclusively focused on infant hydrocephalus patients who demonstrated improvement after their first shunt surgery, with no documented shunt failures. This focus was based on our assumption (Francel et al, 1999;Chong et al, 2002;Lollis et al, 2010;Czosnyka et al, 2013;Mirone et al, 2019;Skalický et al, 2022) 5-2.5; 3.5-5.5; 7.0-9.0; 10.5-12.5; 13.5-15.5 1; 2; 2; 2; 2 1.00…”

“…These variables were employed in unsupervised machine learning analysis to optimize the number and range of valve performance levels. It should be noted that shunt valve performance levels were also converted to drainage pressure values according to the respective manufacturer's catalogs when specific drainage pressures were not recorded in the operative reports (Francel TABLE 1 (Continued) Specifications of shunt valve models, manufacturers, types, performance levels, and pressure ranges and errors (Francel et al, 1999;Chong et al, 2002;Lollis et al, 2010;Czosnyka et al, 2013;Mirone et al, 2019;Skalický et al, 2022) , 1999;Chong et al, 2002;Lollis et al, 2010;Czosnyka et al, 2013;Mirone et al, 2019;Skalický et al, 2022).…”

Feasibility of assessing non-invasive intracranial compliance using FSI simulation-based and MR elastography-based brain stiffness

“…As we said, we only recruited patients with improved outcomes and without valve adjustments over 7 months after shunt surgery. Hence, we defined an outlet pressure instead of the shunt, as reported in the Medtronic shunt catalog 40 . After applying the abovementioned processes, we calculated the ICP using FSI simulation for all 14 patients before shunt surgery and 7 stages after shunt surgery (Fig.…”