Device for regulating the flow of cerebrospinal fluid in a drain

Details Device for regulating the flow of cerebrospinal fluid in a drain Device for regulating the flow of cerebrospinal fluid in a drain

1995-05-17

1997-07-01

Weiss, John G.

Surgery

Devices transferring fluids from within one area of body to...

With flow control means

604247, A61M 500

Patent

active

056431953

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a device for regulating the flow of an organic liquid in an artificial drainage circuit extending between a production site and a resorption site in a patient. One of the main applications of the invention relates to draining cerebrospinal fluid in the event of hydrocephalus, for example, regardless of whether it is in the cranium or in the lumbar region.
Hydrocephalus is a disease that is caused, in particular, by the natural drainage paths for cerebrospinal fluid being blocked. This disease is treated by installing a bypass for passing the liquid either from the ventricles in the cranium or from the base of the spinal column to a resorption site, and in particular the peritoneum.
This bypass includes a pipe with a flow-regulating valve, and the entire assembly is placed beneath the skin of the patient.
Several types of valve are presently available on the market for performing this function. The simplest include valves of the non-return type. Such valves are constituted by a slitted tube whose slits widen when the pressure inside the tube overcomes the elastic force of the tube which tends to close the slits (to which must be added or subtracted the pressure that obtains in the portion of the pipe situated downstream from said valve). It may likewise have a valve member pressed against a seat by a calibrated spring defining a pressure threshold at which the valve opens.
One of the major drawbacks of such valves lies in their lack of adjustment means. Unfortunately, the characteristics of the valve need to be adapted to each patient as a function of the natural characteristics of the patient's organism, and for any given patient, the characteristics of the valve need to be modified over time as a function of the way the disease evolves. Replacing one valve with another having different characteristics, whether for the purposes of initial adjustment or during evolution of the disease, requires a surgical operation to be performed since the valve is implanted beneath the skin of the patient.
Adjustable valves have therefore been developed. These comprise a spring urging a valve member (a bead) against its seat and organized so that the rated value of the spring can be adjusted from the outside without performing surgery. A control member is coupled to the spring and is capable of rotating inside the housing of the valve. That member is responsive to a magnetic field and it can be magnetically coupled through the skin with a driving member for the purpose of changing its position. Such valves are generally complex, and thus of considerable size and volume, they are of debatable reliability, and they are liable to become wrongly adjusted on receiving a shock. In addition, they include metal elements that interfere with certain acts such as taking X-rays.
In general, given the small driving forces that can be implemented in valves of that type, they are very difficult to build. In addition, regularity of operation is very chancy, since equilibrium of the valve member once a flow is established through the valve is highly sensitive to variations in the pressure and in the viscosity of the liquid. In addition, the high degree of miniaturization of that type of valve gives rise to devices that are fragile and liable to be destroyed.
Furthermore, known valves operate in a manner that is subject to parameters that vary very considerably, particularly as a function of the position of the patient. Thus, in the standing position, the pressure difference between the production site and the resorption site may be as much as 400 mm of water column, whereas in the prone position, the pressure difference may be zero. Furthermore, the absolute pressure in particular in the ventricular cavities, varies depending on whether the patient is standing or prone (it increases in the prone position). In other words, seen from the valve, it appears that one of the sites is subject to large variations in pressure while the other site is subject to variations in pressure that are smaller but not negligi

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