• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.1061-1071
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• 2001

The present study investigated design parameters of shunt valves and anti-siphon device used to treat patients with hydrocephalus. The shunt valve controls drainage of cerebrospinal fluid (CSF) through passive deflection of a thin and small diaphragm. The anti-siphon device(ASD) is optionally connected to the valve to prevent overdrainage when the patients are in the standing position. The major design parameters influencing pressure-flow characteristics of the shunt valve were analyzed using ANSYS structural program. Experiments were performed on the commercially available valves and showed good agreements with the computer simulation. The results of the study indicated that predeflection of the shunt valve diaphragm is an important design parameter to determine the opening pressure of the valve. The predeflection was found to depend on the diaphragm tip height and could be adjusted by the diaphragm thickness and its elastic modulus. The major design parameters of the ASD were found to be the clearance (gap height) between the thin diaphragm and the flow orifice. Besides the gap height, the opening pressure of the ASD could be adjusted by the diaphragm thickness, its elastic modulus, area ratio of the diaphragm to the flow orifice. Based on the numerical simulation which considered the increased subcutaneous pressure introduced by the tissue capsule pressure on the implanted shunt valve system, optimum design parameters were proposed for the ASD.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.699-702
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• 2002

Shunt valves implanted in the subcutaneous tissue of brain to treat patient with hydrocephalus were numerically simulated to investigate influence of pressure pulsation on their flow control characteristics. Shunt valves are subjected to pressure variation since ventricles enclosing the brain are under pressure pulsation rather than uniform pressure due to blood pressure variation. We modeled flow orifice through shunt valve and imposed pulsating pressure and valve diaphragm movement to compute flow through the valve. The results of our study indicated that flow rate increased by $40{\%}$ by introducing pressure pulsation and diaphragm movement on the shunt valve. Our results demonstrate the pressure-flow control characteristics of shunt valves unplanted above human brain may be quite different from the characteristics obtained by syringe pump test with uniform pressure and no diaphragm movement.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.1
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• pp.31-34
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• 2004

This paper presents the fabrication and testing of a two-way pressure regulation micro shunt valve with an anti-siphon effect that can be implanted in hydrocephalus patients. This micro shunt valve consists of a silicone rubber membrane and a valve seat for the opening pressure control as well as the anti-siphon behavior. The two-way pressure regulation and the anti-siphon effect of the micro shunt valve are verified experimentally for various sizes of membranes and valve seats.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.1051-1054
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• 2000

We developed the micro CSF (celebrospinal fluid) shunt valve with surface and bulk micromachining technology in polymer MEMS. This micro CSF shunt valve was formed with four micro check valves to have a membrane connected to the anchor with the four bridges. The up-down movement of the membrane made the CSF on & off and the valve characteristic such as open pressure was controlled by the thickness and shape of the bridge and the membrane. The membrane, anchor and bridge layer were made of the $O_2$ RIE (reactive ion etching) patterned Parylene thin film to be about 5~10 microns in thickness on the silicon wafer. The dimension of the rectangular nozzle is 0.2＊0.2 $\textrm{mm}^2$ and the membrane 0.45 mm in diameter. The bridge width is designed variously from 0.04 mm to 0.12 mm to control the valve characteristics. To protect the membrane and bridge in the CSF flow, we developed the packaging system for the CSF micro shunt valve with the deep RIE of the silicon wafer. Using this package, we can control the gap size between the membrane and the nozzle, and protect the bridge not to be broken in the flow. The total dimension of the assembled system is 2.5＊2.5 $\textrm{mm}^2$ in square, 0.8 mm in height. We could precisely control the burst pressure and low rate of the valve varing the design parameters, and develop the whole CSF shunt system using this polymer MEMS fabricated CSF shunt valve.

• Journal of Biomedical Engineering Research
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• v.23 no.5
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• pp.391-395
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• 2002

Shunt valves used to treat patient with hydrocephalus were numerically simulated to investigate influence of pressure pulsation on their flow control characteristics. We modeled flow orifice through the shunt valve and imposed pulsating pressure and valve diaphragm movement to compute flow through the valve. The results of our study indicated that flow rates increased more than 40% by introducing pressure pulsation and diaphragm movement on the shunt valve. Our results demonstrate the pressure-flow control characteristics of shunt valves implanted above human brain may be quite different from those obtained by syringe pump test just after manufacture that induces uniform pressure.

• 한국전산유체공학회:학술대회논문집
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• 2000.05a
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• pp.21-26
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• 2000

Pressure-flow control characteristics of a commercially available cerebrospinal flow(CSF) control shunt valve was tested using fluid-solid interaction analysis. Pre-stress of the valve diaphragm(membrane) was computed for proper valve opening. The results were ir good agreements with the valve specification listed in the commercially available CSF control valve. The results of the study can be effectively used to design variety of CSF control shunt valves.

• Journal of Chest Surgery
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• v.33 no.6
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• pp.476-486
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• 2000

Background: Pulmonary atresia with intact ventricular septum(PA/IVS) is an anatomically heterogenous anomaly with a variety of surgical strategies possible. The purpose of the study is to evaluate the influence of right ventricular size on the early and midterm results of surgical repair of PA/IVS. Material and method: Medical records of 20 consecutive patients with PA/IVS operated on between January 1993 and August 1999 were retrospectively reviewed. There were 12 boys and 8 girls whose ages ranged from 2 days to 14.5 months (median 6 days). Their body weight ranged from 2.52kg to 9.35 kg(median 3.18kg). The preoperative Z-value of the diameter of the tricuspid valve(T-valve) was less than or -4 in 5 patients, between -4 and -2 in 1, between -2 and 0 in 7, between 0 and 2 in 6, and greater than or 2 in 1. All patients who had z-value of tricuspid valve greater than -2.05 were attempted biventricular repair(n=15) and all patients who had it smaller than -4.4 underwent systemic-pulmonary shunt operation only(n=3) or bidirectinal cavopulmonary shunt with right ventricular reconstruction(n=2). Result: Two early deaths(2/20, 10%) occurred. Both were infants who underwent transannular patch with shunt. One of these two had huge right ventricle(Z-value of tricuspid valve = 5). There were 2 late non-cardiac deaths 3 and 7 months after operations respectively. Follow-up was completed in all children at a mean of 35.3 months(range, 5 to 54 months). 10 of 11 survivors who underwent transannular patch or valvotomy with or without shunt procedure were in NYHA functional class I even though some of them had small interatrial communication or patent shunt. All three patients who had shunt procedure only at initial palliation completed Fontan procedures with no death. Two patients who underwent right ventricular outflow reconstruction with bidirectional cavopulmonary shunt were also in good condition. Conclusion: The transanular RVOT patch or valvotomy with or without systemic-pumonary shunt as an initial palliative procedure to achieve biventricular repair for the patients who had neither too small nor too large right ventricle(-2.05$\leq$Z-value of T-value of T-valve$\leq$2) could be performed at low operative risk(1/14 7.1%). Systemic-pulmonary shunt procedure and bidirectional cavopulmonary shunt procedure for the patients who had small right ventricle(Z-value of T-valve$\leq$4.4) could be also performed with low risk. But a patient with huge right atrium and ventricle(Z-value of t-valve=5) had poor operative result.

• Journal of Korean Neurosurgical Society
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• v.48 no.3
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• pp.251-258
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• 2010

Objective : Despite rapid evolution of shunt devices, the complication rates remain high. The most common causes are turning from obstruction, infection, and overdrainage into mainly underdrainage. We investigated the incidence of complications in a consecutive series of hydrocephalic patients. Methods : From January 2002 to December 2009, 111 patients underwent ventriculoperitoneal (VP) shunting at our hospital. We documented shunt failures and complications according to valve type, primary disease, and number of revisions. Results : Overall shunt survival time was 268 weeks. Mean survival time of gravity-assisted valve (GAV) was 222 weeks versus 286 weeks for other shunts. Survival time of programmable valves (264 weeks) was longer than that of pressure-controlled valves (186 weeks). The most common cause for shunt revision was underdrainage (13 valves). The revision rate due to underdrainage in patients with GAV (7 of 10 patients) was higher than that for other valve types. Of 7 patients requiring revision for GAV underdrainage, 6 patients were bedridden. The overall infection rate was 3.6%, which was lower than reported series. Seven patients demonstrating overdrainage had cranial defects when operations were performed (41%), and overdrainage was improved in 5 patients after cranioplasty. Conclusion : Although none of the differences was statistically significant, some of the observations were especially notable. If a candidate for VP shunting is bedridden, GAV may not be indicated because it could lead to underdrainage. Careful procedure and perioperative management can reduce infection rate. Cranioplasty performed prior to VP shunting may be beneficial.

• Journal of Korean Neurosurgical Society
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• v.60 no.1
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• pp.1-7
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• 2017

Objective : The diagnosis of shunt malfunction can be challenging since neuroimaging results are not always correlated with clinical outcomes. The purpose of this study was to evaluate the efficacy of a simple, minimally invasive cerebrospinal fluid (CSF) lumbar tapping test that predicts shunt under-drainage in hydrocephalus patients. Methods : We retrospectively reviewed the clinical and radiological features of 48 patients who underwent routine CSF lumbar tapping after ventriculoperitoneal shunt (VPS) operation using a programmable shunting device. We compared shunt valve opening pressure and CSF lumbar tapping pressure to check under-drainage. Results : The mean pressure difference between valve opening pressure and CSF lumbar tapping pressure of all patients were $2.21{\pm}24.57mmH_2O$. The frequency of CSF lumbar tapping was $2.06{\pm}1.26times$. Eighty five times lumbar tapping of 41 patients showed that their VPS function was normal which was consistent with clinical improvement and decreased ventricle size on computed tomography scan. The mean pressure difference in these patients was $-3.69{\pm}19.20mmH_2O$. The mean frequency of CSF lumbar tapping was $2.07{\pm}1.25times$. Fourteen cases of 10 patients revealed suspected VPS malfunction which were consistent with radiological results and clinical symptoms, defined as changes in ventricle size and no clinical improvement. The mean pressure difference was $38.07{\pm}23.58mmH_2O$. The mean frequency of CSF lumbar tapping was $1.44{\pm}1.01times$. Pressure difference greater than $35mmH_2O$ was shown in 2.35% of the normal VPS function group (2 of 85) whereas it was shown in 64.29% of the suspected VPS malfunction group (9 of 14). The difference was statistically significant (p=0.000001). Among 10 patients with under-drainage, 5 patients underwent shunt revision. The causes of the shunt malfunction included 3 cases of proximal occlusion and 2 cases of distal obstruction and valve malfunction. Conclusion : Under-drainage of CSF should be suspected if CSF lumbar tapping pressure is $35mmH_2O$ higher than the valve opening pressure and shunt malfunction evaluation or adjustment of the valve opening pressure should be made.

• Journal of Biomedical Engineering Research
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• v.22 no.5
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• pp.403-412
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• 2001

The Present study analyzed the pressure-flow characteristics of a Korean shunt valve. Changes in the characteristic currie depending on the design parameters were also investigated. The Korean shunt valve used in the present study was constant pressure type and our analyses were validated through experiments. We applied fluid-structure interaction to solve the flow dynamic Problem because the small diaphragm in the valve was made from flexible silicone elastomers. Considering the material nonlinearity of the hyper-elastic material. the Mooney-Rivlin approximation was employed. The results of the numerical analyses were close to the experimental results The major Pressure drop was observed to happen in the small diaphragm. The slope of the pressure-flow characteristic curve was computed to be 0.37mm$H_2O$.hr/cc, which was similar to the average value of commercial shunt valves. 0.40mm$H_2O$.hr/cc. Therefore. our valves analyzed in the Present study showed a Proper Pressure control characteristics of the constant pressure type shunt valves. The opening pressure could be controlled by adjusting the amount of predeflection of the valve diaphragm. In order to obtain opening pressures of 25mm$H_2O$ and 80mm$H_2O$, respectively, and the required predeflection was found to be 10.2$\mu$m and 35.3$\mu$m. The flow orifice size was found to be within 10$\mu$m during valve operation Therefore, Precision design and manufacturing techniques are necessary for successful operations of the shunt valve. The study indicated the amount of predeflection as well as the magnitude of corner rounding of the diaphragm edge are important design parameters to influence the slope of the pressure-flow characteristic curve.