RU2337721C1 - Shunt for hydrocephaly treatment - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: shunt contains silastic pomp mounted between two back valves and membrane. Valves are in the form of linear bushings with radial aperture d tighten inside due to tape bend. Ratio of valve capacity to pressure fall is proportional to value

where δ is tape thickness, mm; d is valve aperture diameter, mm; b is tape width, mm; N is liquor rate (valve capacity), mm³/min; R is internal radius of bushing, mm; ΔP is pressure fall, mm WC. Linear bushings are simultaneously executed on flat foundation. The second bushing is segmental to the first one. There is a partition amounted from above between bushings. Bushings are end blocked from above by dome-shaped membrane of variable radius and variable thickness in dome point δp and along edges δe by relation δe/δp=1.3±0.1.

EFFECT: workable design with controlled parameters and minimised dimensions.

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Description

The invention relates to medical devices used in neurosurgery for craniocerebral implantation, which are designed to provide unidirectional controlled outflow of cerebrospinal fluid from the brain to the right atrium (into the abdominal cavity).

Known Schulte shunt valve systems US No. 3.759.982, class A61M 27/00, 604/10, 1973; US No. 4.364.395, cl. A61M 27/00, 604/10, 1982; USA No. 4.741.730 cl. A61M 27/00, 604 / 8.9, 1988; USA No. 5.176.627, cl. A61M 5/00, 604/8, 1993, which are difficult to manufacture, contain metal parts, many glued elements manually, require a very high production culture and therefore do not guarantee stable performance.

For the prototype, the shunt according to US patent No. 5,304.114, class. A61M 5/00, 604 / 8.9, 1994, which, like analogs, has sufficiently large dimensions, which is a significant drawback for a shunt implanted under the scalp.

The task is to make the valve design simple, technologically advanced, adjustable, which minimizes the overall dimensions of the shunt and ensures reliable operation without replacement until the patient's life.

This problem is solved by the design of the valve in the form of a cylindrical sleeve with a radial hole d, pressed from the inside due to the bending of the tape, while the ratio of the valve performance to the pressure drop across it is proportional to

,

,

where δ is the thickness of the tape, mm;

d is the diameter of the valve hole, mm;

b is the width of the tape, mm;

N - cerebrospinal fluid consumption (valve capacity), mm ³ / min;

R is the inner radius of the sleeve, mm;

ΔР - pressure drop, mm of water. Art.

For craniocerebral implantation, the cylindrical bushings are made at the same time on a flat base, the second of which is located segmental to the first, a partition is located on top of them, both are overlapped on the ends by a membrane made in the form of a dome with a variable radius and a variable thickness at the top of the dome δв and along the edges δc by the ratio δc / δc = 1.3 ± 0.1.

The very design of the valve with a tape allows you to minimize the dimensions of the shunt due to the layout of the second sleeve in the form of a segment of the first and even further minimize due to the first sleeve in the form of a segment, but this is already impractical, because reducing the volume of the pump leads to the inconvenience of using it.

The following drawings are shown, which show:

Figure 1 - General view of the shunt for implantation.

Figure 2 - section aa in plan.

Figure 3 is a cross section BB on the fitting for the exit of cerebrospinal fluid.

Figure 4 is a graph of the dependence of valve performance on the differential pressure at different radii of the shunt.

Figure 1 shows a General view of the shunt for cranial implantation with the following notation:

δв - membrane thickness at the top of the dome, mm;

δк - membrane thickness at the edges of the dome, mm;

The pump 1 is formed between the membrane 2 and the cylindrical bushings 3 and 4 on a flat base 5, the second sleeve 4 is made in the form of a segment of the first, the base of which is the outer side of the sleeve 3 instead of the chord. Both are separated from the pump 1 by a partition 6, forming a chamber 7 in front of the fitting 8 to exit the cerebrospinal fluid. Both bushings 3 and 4 at the ends are covered by a membrane 2, made in the form of a dome with a variable radius in the longitudinal - Rpr and Rpop - transverse direction. The height of the shunt at the top of the dome is equal to the width of the shunt, and the height of the dome is one third of the height of the shunt. The membrane thickness is variable from the top of the dome δв to the edge δк in the ratio δк / δв = 1.3 ± 0.1, which gives it an increase in stiffness when the dome is pressed during forced pumping of the liquor by pump 1 and ensures elastic restoration of shape after unloading.

The cylindrical bushings 3 and 4 are made with a radial hole d, pressed from the inside by a tape 9 due to its bending during installation. The length of the tape is 1 + 1 mm less than the inner diameter of the sleeve 3 so that the ends of the tape do not touch each other and the tape does not lose stability. The width of the tape (b = 3d ± 0.3) mm, in order to provide the necessary contact area around the hole d in the vertical direction and thereby the valve tightness at ΔР, is less than that specified for the installed type of shunt: low, medium, high pressure.

The radial hole d in the sleeve 3 passes into the fitting 10 for entry of the cerebrospinal fluid through a ventricular catheter. A radial hole d in the sleeve 4 connects the cavity of the pump 1 to the chamber 7 for the cerebrospinal fluid to exit through the nozzle 8, which is connected through the adapter to a cardiac catheter.

In an implantation operation, the shunt is sutured for the tides 11 (Fig. 2) on a flat base 5. With an increase in intracranial pressure above the shunt established for this patient and, accordingly, the shunt applied is low - N (50 mm water. Art.), Medium - C (100 mm water.) or high - B (150 mm water. Art.) the pressure of the cerebrospinal fluid through a ventricular catheter enters the nozzle 10 and presses on the tape 9, which is squeezed from the hole d of the sleeve 3, the greater the greater the pressure drop (Fig. 4 ) Liquor fills the pump 1 and when the pressure rises above the set value for the outlet valve in the sleeve 4, squeezes the tape 9 and enters the chamber 7, from which through the nozzle 8 and the adapter into the cardiac catheter (Figs. 2, 3).

To stabilize the flow shunt characteristics, the resistance of the outlet valve 4 can easily be set somewhat larger than the input valve due to the greater thickness of the tape and smaller diameter d. With the same technique, it is easy to set the resistance of the inlet valve 3 and thereby the purpose of the shunt - N. S. B - pressure. So the shunt works in automatic mode for a given pressure drop.

For emergency relief of unexpectedly increased cerebrospinal fluid pressure, the doctor or patient presses on membrane 2 and pumps pump 1 cerebrospinal fluid in only one direction, because valves alternately operate either as direct or as reverse. When removing the load on the membrane 2, it due to the variable thickness and accordingly stiffness instantly restores its shape and does not lose stability. The ratio δк / δв = 1.3 ± 0.1 is optimal, because with a ratio less than 1.2, the difference in stiffness is insignificant / 1 / and does not exclude the loss of stability, and with a larger 1.4 the effort / 2 / increases when pumping liquor, which is inconvenient for the doctor.

With a very small tape thickness δ = 0.3 mm, the stiffness of the valve depends little on its curvature (1 / R). Figure 4 shows that when tested on simulators, valves with R = 1.5 and 2 mm are quite pliable and work according to the proposed mechanism for elastic bending of the tape. However, minimizing less than R = 2.5 mm is impractical, because the volume of the pump 1 is small and it is inconvenient to press on the membrane 2. The achieved result (7.1 × 10 × 7 mm) in minimizing the dimensions of the shunt - height, length, width - 2, 3, 4 times less than the existing ones, has no analogues, and this is a decisive indicator for implantation.

At the same time, due to the simplicity of the design of the valve elements: the hole d and the tape 9 cut out from the plate, which is easy to produce of any thickness, the manufacturability and adjustable characteristics of the shunt are ensured.

The valves on the simulators were tested for adhesion and aging of the tape for 11 years using ordinary tap water instead of distilled. Even in such harsh conditions, with an annual demonstration, doctors are shown reliable operation and preservation of the characteristics of the shunt.

Information sources

1. Spindler V.M. et al. // Rubber and rubber. 1990. No4. C 26-28.

2. Spindler V.M., Fedyukin D.L. A.S. USSR No. 945542: MKI F16J 15/00 (BI 1982. No. 27).

Claims (1)

A shunt for the treatment of hydrocephalus during craniocerebral implantation, containing a silicone rubber pump formed between two check valves and a membrane, characterized in that the membrane is made in the form of a dome with a variable radius and a variable thickness at the top of the dome δв and along the edges δк in the ratio δк / δв = 1.3 ± 0.1, two valves made on a flat base in the form of cylindrical bushings are blocked by the membrane from the end, the second of which is located segmental to the first, a partition is located on top of them, and the bushings are made with ialnym hole inside pursed by bending strip, wherein the ratio of performance of the valve to the differential pressure on it proportional

, where δ is the thickness of the tape, mm; d is the diameter of the valve hole, mm; b is the width of the tape, mm; N - cerebrospinal fluid consumption (valve capacity), mm ³ / min; R is the inner radius of the sleeve, mm; ΔР - pressure drop, mm water. Art.

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