Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1998-01-12
2001-04-10
Weiss, John G. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S175000, C604S905000, C604S890100
Reexamination Certificate
active
06213973
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to vascular access systems and, more specifically, to implantable vascular access ports for use in such systems.
2. Background Art
Implantable vascular access systems are used extensively in the medical field to facilitate the performance of recurrent therapeutic tasks inside the body of a patient.
Such a vascular access system generally includes an implantable vascular access port attached to the proximal end of a vascular catheter. A typical vascular access port has a needle-impenetrable housing that encloses a fluid reservoir that is accessible from the exterior of the access port through a needle-penetrable elastomeric septum. The vascular access port also includes an outlet stem, which projects from the housing and encloses a fluid passageway that communicates with the fluid reservoir. The distal end of the catheter is mechanically coupled to the vascular access port in fluid-tight communication with the fluid reservoir using the outlet stem.
The entirety of the system, both the vascular access port and the catheter attached thereto, is implanted in the body of a patient. The distal tip of the catheter is disposed at a predetermined location where therapeutic activity is to be effected. The distal tip of the catheter is either open-ended or is provided with pressure-sensitive valving that affords for one-way or two-way fluid flow therethrough during use of the system by medical personnel. Once the vascular access system is implanted, the tip of a hypodermic needle can then be employed selectively and repeatedly to access the fluid reservoir of the access port by penetrating the skin at the implantation site for the access port and then by being advanced through the septum of the access port itself.
The syringe associated with the hypodermic needle then is able to deliver medication or other fluids into the fluid reservoir. These flow through the outlet stem of the vascular access port and through the catheter attached thereto, thereby to become infused into the body of the patient at the distal tip of the catheter. Alternatively, the syringe is able to aspirate bodily fluids from the vicinity of the distal tip of the catheter by withdrawing such fluids along the catheter, through the outlet stem and the fluid reservoir of the vascular access port, and lastly up the hypodermic needle into the syringe.
For the repeated selective use of an implanted vascular access port to be successful in the long term, the septum of that vascular access port be possessed of specific properties.
For example, when the tip of a hypodermic needle penetrates the septum, the material of the septum about the shaft of the hypodermic needle must form an effective seal about the exterior of that needle. Otherwise, fluid will escape from the fluid reservoir to the exterior of the vascular access port along the exterior of the shaft of the hypodermic needle. This needle sealing characteristic of the septum of a vascular access port is influenced by several factors, a few of which will be explored subsequently.
The septum should also impose a predetermined amount of needle retention force on the shaft of any hypodermic needle that has penetrated therethrough. Needle retention force refers to the tendency of a septum to resist the removal therefrom of the shaft of any such hypodermic needle. Inadequate needle retention force can allow the tip of the shaft of a hypodermic needle to become withdrawn inadvertently from a septum, even after the tip of the shaft of the hypodermic needle has penetrated the septum to the fluid reservoir in the vascular access port. This is quite painful to the patient and disruptive of the therapeutic process.
If the withdrawal of the hypodermic needle is detected, the attention of medical personnel will, at the very least, need to be redirected to the penetration of the tip of the hypodermic needle through the septum of the vascular access port. If the inadvertent withdrawal of the tip of the shaft of the hypodermic needle from the septum is not detected, however, fluids in the syringe associated with the hypodermic needle will not even enter the fluid reservoir of the vascular access port when infusion of those fluids is undertaken. Instead, the fluids will be injected subcutaneously into the pocket in which the vascular access port is implanted. Necrosis of the tissue surrounding the implantation pocket will occur as a result, complicating therapeutic activities and frequently requiring the removal and reimplantation at another site of the entire vascular access system.
A corollary aspect of the needle retention force imposed on the shaft of a hypodermic needle by any given septum is the degree of force required to cause the tip of that hypodermic needle to advance through the septum from the exterior surface to the interior surface thereof.
This is referred to as the needle penetration force. The needle retention force and the needle penetration force for a given septum are generally identical, but oppositely directed.
It is desirable that the amount of the needle penetration force.be within a range that facilitates the labors of medical personnel. First, the needle penetration force for a given septum cannot be substantial, or the process of accessing the fluid reservoir of the associated vascular access port with the tip of the shaft of a hypodermic needle will be difficult for medical personnel and dangerous to the patient.
On the other hand, the needle penetration force for a given septum should be distinctly different and usually greater than the force required to advance the tip of the shaft of a hypodermic needle through the tissue of the patient at the implantation site for the vascular access port. If such is the case, medical personnel utilizing a hypodermic needle to access the fluid reservoir in a vascular access port will be informed by feel when the tip of the hypodermic needle has actually encountered and is being advanced through that septum. Such tactile feedback has been reported to be particularly useful.
The sealing effectiveness, the needle retention force, and the needle penetration force for a given septum are each in part related to the amount and types of forces applied to the septum by the housing of the vascular access port in which the septum is installed. While torsional forces and tensions are on occasion applied to a septum by the housing of the vascular access port in which the septum is installed, it is more common that the forces applied thereto by a housing are directed inwardly toward the body of the septum. In general, the greater the inwardly directed forces that are applied to a septum, the greater will be the sealing effectiveness of the septum about the shaft of a hypodermic needle. Also, the larger will be the needle retention force and the needle penetration force that are imposed on the shaft of that hypodermic needle by that septum.
The inwardly directed forces imposed on an installed septum by the housing of a vascular access port must, however, not be so great that penetrating the septum with the tip of a hypodermic needle results in coring of the septum. When the tip of a hypodermic needle advances through the septum, coring occurs if any portion of the septum material is forced inside the shaft of the hypodermic needle through the opening in the tip thereof That portion of the septum material forced inside a hypodermic needle in this process is in effect severed from the rest of the body of the septum material.
S Septum coring produces small, detached particles of the septum that are likely to enter the fluid that is infused by the implanted vascular access system into the vascular system of the patient. These particles can obstruct fluid flow through the outlet stem of the vascular access port, or if escaping through the outlet stem of the vascular access port, can become trapped in the cardiovascular system of the patient.
In addition, septum coring produces small passageways through the body of a septum. On occasion these passageways
Christian Kelly J.
Eliasen Kenneth A.
Powers Kelly B.
C. R. Bard Inc.
Thanh Loan H.
Trask & Britt
Weiss John G.
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