Implantable devices and methods for controlling the flow of fluids within the body
Implantable fluid shunting apparatus and related procedures for controlling the pressure of fluids within anatomical cavities or areas of the human body. The apparatus generally comprises a tube using a diffusion barrier (e.g., diffusion chamber) shaped on a proximal end thereof. Fluid which flows through the tube will collect within the diffusion chamber and will liquefy outwardly therethrough. However, the existence of the diffusion chamber will prevent microbes, cells or other matter from interfering or backflowing through the tube. Moreover, the tube might be provided with a pressure-openable aperture through which fluid from the tube can flow in the diffusion chamber. Such pressure-openable aperture will remain closed, until the pressure of fluid inside the tube exceeds a predetermined maximum pressure P.sub.MAX. This way, the pressure-openable aperture will limit the quantity of fluid drained from the anatomical area or section of the body, thereby avoiding hypotony within such anatomical area or cavity.
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A number of diseases and disorders in humans and other mammals are characterized with the build-up of excessive fluid pressure within one or more human body cavities. In many cases, implantable devices or surgical procedures may be employed to shuntexcessive fluid from the body wherein the excess pressure build up is present, to one or more other websites within the entire body, as a method of getting the undesirable pressure buildup, and thus deterring the growth of undesirable sequelaewhich may result from these pressure build-up.
Glaucoma is a disorder of the eye which is characterized by high blood pressure pressure, also is one of the leading causes of blindness in the world. Generally, glaucoma results from a defect in the drainage drainage system, whereas naturallyoccurring endogenous fluid (e.g., aqueous humor) is emptied by the interior of the eye. The consequence of the decreased functional drainage of the eye is three-fold: a) increased intraocular pressure, b) degeneration of the optic nerve and supportingtissue in the optic nerve head (disc ), and c) progressive loss of the visual area.
Individual cases of glaucoma are usually categorized, on the basis of etiology, into two categories. These two important are”closed angle glaucoma” and”open angle glaucoma”.
In closed angle glaucoma (syn. “angle-closure glaucoma”,”narrow-angle glaucoma”,”pupillary block glaucoma”) excess fluid accumulates within the anterior chamber of the eye due to the gradual closure of an anterior angle formed by thejunction of the iris and the inner surface of the trabecular mesh work through which the aqueous humor is normally reabsorbed. Closure of the anatomical angle prevents normal drainage of aqueous humor from the anterior chamber of the eye.
In open angle glaucoma (syn. “chronic simple glaucoma””simple glaucoma”,”wide-angle glaucoma) the angle of the anterior chamber remains ordinary, but the drainage of aqueous humor from the anterior chamber is impeded or obstructed by other ways,such as edema or swelling of the trabecular spaces, abnormal pigment dispersion, or non-perforating harm to the eye leading to vascular congestion.
Various pharmacologic manners of therapy have been used to lessen the intraocular fluid pressure in glaucoma sufferers. Drugs which have been administered to treat glaucoma have contained parasympathomimetic agents of the choline ester type (e.g.,bethanechol, carbachol and methacholine), carbonic anhydrase inhibitors (e.g., acetazolamide), anticholinesterase agents (e.g., physostigmine, pilocarpine, demecarium, echothiophate and isoflurophate), sympathomimetic agents (e.g, epinephrine,phenylephrine) and .beta. -adrenergic blocking agents (e.g., tymolol). But, these a variety of drug therapies for glaucoma are occasionally related to significant untoward effects, including headache, blurred vision, allergic reactions, retinaldetachment, phacodinesis, histological changes inside the eye and possible interactions with other medications.
As opposed to pharmacologic styles of therapy, at least a few glaucoma patients may be treated surgically by producing surgical openings into the anterior chamber of the eye, to alleviate drainage of excessive aqueous humor from the anteriorchamber. Many of these surgical methods involve the formation of an opening or gap into the anterior chamber, under the conjunctiva and/or scleral flap like fluid will be emptied by filtration from the anterior chamber of the eye, into thetissues located inside the lateral wall of the eye. The significant problems associated with these surgical filtration processes stem from the magnitude of this opening or hole made into the anterior chamber. These problems include hypotony, synechiae,inflammation, cataract, corneal decompensation (edema), vitritis, choroidal separation (detachment), macular edema, and infections which may cause endophthalmitis. Additionally, such glaucoma filtration surgery is often ineffective because of the formation ofdense fibrovascular connective tissue (e.g., scar tissue) around the surgical opening formed into the anterior chamber. Such proliferation of connective tissue will close off the surgically-formed opening into the anterior chamber, thereby deterringor preventing the desirable filtration of aqueous humor into the subconjunctival space.
In opinion of post-surgical complications linked to the maturation of fibrovascular connective tissue (e.g., scar tissue) around the surgical site, a number of implantable drainage apparatus are utilized to ensure the desirable filtrationand outflow of aqueous humor through the surgically-formed opening will persist, regardless of the configurations of, scar tissue throughout the post operative period. Examples of implantable shunts or other implantable devices which have been implantedinto the eye for drainage of aqueous humor from the anterior chamber of the eye include those described in U.S. Pat. Nos. 4,750,901 (Molteno), 5,041,081 (Odrich), 5,476,445 (Baerveldt), 4,886,488 (White), 5,454,796 (Krupin), 5,397,300 (Baerveldt),5,372,577 (Ungerleider), 5,338,291 (Speckman, et al.), 5,300,020 (L’Esperance), 5,178,604 (Baerveldt, et al.), 5,171,213 (Price), 5,092,837 (Klein et al.), 4,968,296 (Klein et al.), 4,946,436 (Smith), 4,936,825 (Ungerleider), 4,886,488 (White), 4,806,382(Burns et al.), 4,554,918 (White), 4,521,210 (Wong), 4,428,746 (Mendez), 4,184,491 (McGannon), 4,157,718 (Baehr), 4,030,480 (Meyer), 5,433,701 (Rubinstein), 5,346,464 (Camras), 5,073,163 (Lippman), 4,604,087 (Joseph), 5,180,362 (Worst), 5,520,631 (Li etal.) .
The major drawback associated with the use of implantable shunts for therapy of cataract is the fact the fact that, in the immediate post operative period, the shunt may facilitate excessive fluid drainage which leads to hypotony inside the anteriorchamber, flattening of the anterior chamber and possible choroidal detachment and/or phthisis bulbi. Such excessive post-operative fluid outflow can also bring about expansion of the fibrous capsule found under the rectus muscles of the eye. Suchexpansion of the fibrous capsule may elongate and tighten the rectus muscles, thereby inducing heterotropia and impairing the motility of the eye at the quadrant whereas the implant is located. Furthermore, due to the size of some of these shuntdevices, the bulky presence of the apparatus itself inside the subconjunctival space could lead to scleral erosion, changes in the natural curvature of the eye, or damage to adjoining vasculature and tissue. Other problems associated with the usage of implantableshunt devices for treating glaucoma involve friction and use imparted by the implanted shunt apparatus, irritation of the iris endothelium brought on by insertion of the shunt apparatus to the anterior chamber, along with intrusion of cells, microbes, proteinsor other matter through the lumen of the shunt apparatus and into the anterior chamber of the eye.
Another disorder where the accumulation of abnormal fluid pressure is a hallmark is hydrocephalus. In hydrocephalus, excessive amounts of cerebrospinal fluids accumulate within skull, normally leading to elevated intracranial pressure. Thechronic elevation in intracranial pressure brought on by such excess cerebrospinal fluid inside the skull typically results in enlargement of the mind, prominence of the forehead, brain atrophy, mental deterioration, and convulsions. Hydrocephalus ismaybe of congenital source or may be an acquired illness. In certain patients, hydrocephalus is of abrupt onset while in others it’s slowly progressive.
In addition to different pharmacologic therapies, the surgical approach to treatment of hydrocephalus frequently includes the implantation of a shunt which facilitates drainage of excessive cerebrospinal fluid in the intracranial area, to other regions ofthe body whereas it may be tolerated–most commonly into the lymph nodes.
In addition to glaucoma and hydrocephalus, numerous other ailments and ailments involve the buildup of excessive fluid within one or more bodily spaces (i.e., cavities) of their entire body, and may be effectively treated by shunting of their excessivefluid from the affected body space (i.e., body cavity) to other region(s) of your entire body. Nonetheless, in many cases, it is desirable an effluent shunt device be utilized, which such shunt device be valved or even pressure-regulated such that just excessivefluid is going to be removed in the affected body cavity, while allowing the normal amount of such fluid to stay within the affected body cavity, as long as the pressure within the cavity is in the normal selection. Thus, it is required for the implantedshunt device to include a pressure-sensitive opening or alternative pressure-actuated valving device which will allow fluid to flow from their affected body cavity just when the fluid in the body cavity has exceeded a predetermined maximum pressure.
One complication related to the use of implantable shunt apparatus to drain fluid from body cavities is that proteins, cellular thing, or other debris can block the lumen of the shunt tube thereby interfering with the drainage of fluidthrough the tube. Additionally, proliferation of tissue or blebs may compress, collapse, or block the shunt tube. Additionally, pathogenic microorganism or irritating proteins or other thing may migrate through the lumen of the shunt tube into the influenced bodycavity in a way that may result in iatrogenic disease, inflammation or irritation of the affected body cavity.
Given the above-summarized constraints and drawbacks connected to the implantable fluid-shunting devices of the prior art, it is evident that no single fluid-shunting apparatus has proven to be optimal for all applications. Thus, thereexists a need in the art for its evolution of new implantable fluid-shunting devices which comprise: a) means for valving or pressure-regulation of the fluid outflow and b) means of preventing germs, cells, proteins or other thing from cloggingthe shunt or glancing through the shunt to the affected body cavity.
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