Surgery – Devices transferring fluids from within one area of body to... – With flow control means
Reexamination Certificate
1998-03-16
2001-02-27
Dawson, Glenn K. (Department: 3763)
Surgery
Devices transferring fluids from within one area of body to...
With flow control means
C604S008000, C604S198000, C604S246000
Reexamination Certificate
active
06193682
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to medical devices which are implanted in the human body, and particularly, to a medical device used to treat hydrocephalus.
2. Background Discussion
“Hydrocephalus” is the diagnostic term meaning excess water in the brain or cranial vault due to the cerebral spinal fluid flow being blocked. When this occurs, the increased intracranial pressure causes the brain to flatten into a thin shell against the skull. In newborn babies this fluid pressure increase also causes the head to swell which, if left untreated, usually results in death. Hydrocephalus is discussed in greater depth in the “Encyclopedia of Neuroscience” Volume 1, Edited by George Adelman and published by Birkhauser. Medical valve type devices, sometimes referred to as shunts, are used to treat hydrocephalus. In an article entitled “Shunt Obstruction: A preventable Complication?” published in Pediatric Neurosurgery (1993, Volume 19, pages 156-164, C. Sainte-Rose discusses mechanical shunt complications.
As disclosed in U.S. Pat. No. 5,411,473, one type of valve (herein the Glaucoma Valve) has been used to treat glaucoma by allowing aqueous humor to flow from the intraocular chamber of the eye to relieve excess pressure. The Glaucoma Valve uses a membrane under tension to form its own fluid retention chamber. A slit-like opening is along adjoining, overlapping edges of portions of the membrane. The membrane responds to slight changes in fluid pressure and expands or contracts to open or close the opening. When opened, it provides a wide open mouth with parted lips that allows for free flow of fluid through it without any substantial resistance to fluid flow. This feature also substantially reduces the likelihood that the opening will be clogged by particulate matter. In a copending application of the inventor, U.S. Ser. No. 08/592,016, now U.S. Pat. No. 5,728,061, there is disclosed a device for treating individuals with hydrocephalus that uses the Glaucoma Valve. Although this device has several advantages over the prior art, it was not specifically designed for treating infants. The invention disclosed herein is an improvement over this device which is especially designed to be implanted in infants (children typically from about the age of 1 month to 4 years).
SUMMARY OF THE INVENTION
In accordance with this invention, the Glaucoma Valve has been enclosed within a uniquely shaped and sized flexible shell to provide a medical device that may be used to treat hydrocephalus in infants. This valve is especially suited for this application because its slit-like opening is not easily obstructed by particulates and it is self regulating, opening and closing in response to slight changes in pressure.
There are several features of this invention, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this invention as expressed by the claims, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section of the application entitled “DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT,” one will understand how the features of this invention provide its benefits, which include ease of implantation into a patient, especially small children, ease of manufacture, and reliability in draining fluid from a patient's body.
The first feature of the medical device of this invention is that it includes a shell having an aerofoil-like shape, and preferably having a maximum volume of about 0.275 cubic inch. The shell is made of a flexible, resilient material, preferably siliconized rubber, which is self sealing to allow the shell to be pierced with a needle that upon withdrawal leaves a puncture which is sealed due the resiliency of the material. Consequently, it is adapted to expand or contract in response to pressure. Preferably, the shell has a maximum height which is about 0.35 inch, a maximum width which is about 0.65 inch, and a maximum length which is about 1.2 inch. Typically, the height ranges between about 0.20 and about 0.35 inch, the width ranges between about 0.55 and about 0.85 inch, and the length ranges between about 0.8 and about 1.2 inch.
The second feature is that the shell includes an anterior cavity and a posterior cavity separated by a partition wall. The anterior cavity has a maximum volumetric capacity of about 0.030 cubic inch and the posterior cavity has a maximum volumetric capacity of about 0.110 cubic inch. Typically, the anterior cavity has a volumetric capacity ranging between about 0.018 and about 0.030 cubic inch and the posterior cavity has a volumetric capacity ranging between about 0.100 and about 0.150 cubic inch. The ratio of the volume of the anterior cavity to the volume of the posterior cavity ranges between about 1:4 to about 1:6.
The third feature is that the shell has opposed ends, one of which is tapered so that this tapered end is adapted for insertion into a patient's body. Preferably, both ends are tapered. There are a pair of tubes, one tube is an inlet tube in communication with one end and the other tube is an outlet tube in communication with the other end. The inlet tube has a first end in communication with the fluid in the patient's body (typically the cranium) to be drained and a second end in communication with the anterior cavity. The outlet tube has a first end in communicationt the posterior cavity and a second end from which the fluid is drained from the shell into the patient's stomach or heart.
The fourth feature is a one-way directional flow valve housed within the posterior cavity and connected to the partition wall. The one-way directional flow valve, preferably the Glaucoma Valve, has an inlet end which is in communication with the anterior cavity and an outlet end in communication with the posterior cavity. At a predetermined pressure, the valve allows fluid to flow through the inlet tube through the one-way directional flow valve and exiting the shell through the outlet tube. The one-way directional flow valve has a height ranging between about 0.100 and about 0.175 inch, a width ranging between about 0.60 and about 0.80 inch, and a length ranging between about 0.35 and about 0.65 inch. Preferably, the one-way directional flow valve has a pair of overlying membranes in tension which provide a chamber with a slit-like opening through which fluid exits the one-way directional flow valve into the posterior cavity. The chamber has a trapezoidal configuration with a minimum volumetric capacity of about 0.03 cubic inch to a maximum volumetric capacity of about 0.05 cubic inch. The overlying membranes are formed from a single sheet of siliconized rubber material having a thickness of at least about 0.0075 inch which is folded to form the slit-like opening, and a pair of plates maintain the membrane in tension. The folded sheet siliconized rubber material and the pair of plates have a substantially rectangular configuration.
The fifth feature is that the device is manufactured by insert molding where the inlet tube, the outlet tube, and the one-way directional flow valve are placed with a mold which is then filled with material to form the shell.
This invention also includes a method for treating hydrocephalus by draining the fluid from the cranial vault of a patient. The method includes
(a) providing a medical device, including
a shell including a pair of cavities, said shell having an aerofoil-like shape and a maximum height which is about 0.35 inch, a maximum width which is about 0.65 inch, and a maximum length which is about 1.2 inch,
a pair of tubes, each tube having free ends and one tube in communication with one cavity and the other tube in communication with the other cavity, and
a one-way directional flow valve housed within the one cavity that at a predetermined pressure allows fluid to flow through one tube into one cavity and then through the one-way directional flow valve into the other cavity and finally exiting the device through the other tube,
Connors John J.
Connors & Associates
Dawson Glenn K.
Maynard Jennifer
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