1. Field of the Invention
The present invention relates generally to the design and use of medical devices, and more particularly to the design and use of an implantable port having a simplified design that establishes temporary access to a body lumen in the patient.
Access to a patient's vascular system can be established by a variety of temporary and permanently implanted devices. Most simply, temporary access can be provided by the direct percutaneous introduction of a needle through the patient's skin and into a blood vessel. While such a direct approach is relatively simple and suitable for some applications, they are not suitable for hemodialysis, peritoneal dialysis, and hemofiltration. Such a direct approach is also inconvenient for other procedures, such as insulin or drug delivery procedures, which are repeated frequently over the lifetime of the patient.
A variety of implantable ports have been proposed over the years to provide long-term vascular access for hemodialysis, hemofiltration, and other medical treatments. Typically, the port includes a chamber having an access region, such as a septum, where the chamber is attached to an implanted cannula which in turn is secured to a blood vessel. In the case of veins, the cannula is typically indwelling, and in the case of arteries, the cannula may be attached by conventional surgical technique. Percutaneous access to a port through a septum is generally limited to small diameter, non-coring needles. Large diameter needles will core the septum, i.e. form permanent channels therethrough, which will destroy the septum after repeated uses. Unfortunately, even the use of small diameter, non-coring needles will eventually cause a septum to fail due to repeated septum penetrations.
Implantable ports having an access aperture and internal valve mechanism for isolating the implanted cannula have also been proposed. One type of implantable valved port is described in a series of issued of U.S. patents which name William Ensminger as inventor. The Ensminger access ports have internal lumens for receiving a percutaneously introduced needle and an internal valve structure for isolating the port from an associated implanted cannula. Generally, the Ensminger ports have a needle-receiving aperture which is oriented at an inclined angle relative to the patient's skin. The Ensminger ports employ relatively entry ports having large funnel-like tapers and troughs so that needles can be introduced through many different sites in accordance with conventional procedures. The Ensminger patents do not describe port access using large diameter, coring needles, such as fistula needles. Moreover, as many of the specific Ensminger designs employ elastomeric valve elements, it is likely that the valve mechanisms would be damaged if the ports were accessed by a fistula needle or other large bore coring needle. Representative Ensminger patents are listed in the Description of the Background Art below.
Although promising, these known valve-type implantable ports are not without limitations. For one thing, these known ports are expensive and that limits their applicability to a broader range of medical treatments. Such implantable ports typically have an interior structure having many moving parts and elements as evidenced by the devices of the Ensminger patents. The complicated interior of these known ports increases the cost per part of each implantable port. Although not true in all circumstances, the additional parts may also increase the probability that one of these parts may fail. The plurality of parts also increases the level of skill required to assemble each implantable port. Additionally, some of these known implantable ports still have valves which contact the needle and will wear out due to needle damage incurred during repeated use. Furthermore, to the extent that implantable ports have been used, it has generally been recommended that the access site be moved relative to the port in order to change the location of the tissue tract between successive access procedures.
For these reasons, it would be desirable to provide improved methods and apparatus for percutaneously accessing a patient's vasculature. The improved methods and apparatus should reduce patient trauma, reduce cost, simplify apparatus design, provide for reliable access to the vasculature, minimize the risk of infection to the patient, and preferably require only minor modifications to present procedures. At least some of these objectives will be met by the invention described hereinafter.
2. Description of the Background Art
U.S. Pat. No. 5,562,617 and WO 95/19200, assigned to the assignee of the present application, describe implantable vascular access systems comprising an access port having an internal slit or duck bill valve for preventing back flow into the port. Vascular access ports having various articulating valves for isolating the port from the vascular system in the absence of external percutaneous connection to the port are described in the following U.S. patents which name William Ensminger as an inventor: U.S. Pat. Nos. 5,527,278; 5,527,277; 5,520,643; 5,503,630; 5,476,451; 5,417,656; 5,350,360; 5,281,199; 5,263,930; 5,226,879; 5,180,365; 5,057,084; and 5,053,013. Other patents and published applications which show implantable ports having valve structures opened by insertion of a needle include U.S. Pat. Nos. 5,741,228; 5,702,363; 4,569,675; 4,534,759; 4,181,132; WO 97/47338; and WO 96/31246. Devices for hemodialysis or devices having one piece valves are described in U.S. Pat. Nos. 4,892,518; 5,098,405; and 5,125,897. Implantable ports and subcutaneous catheters for connecting the ports for hemodialysis, peritoneal dialysis, and other procedures which may be useful in the present invention are described in co-pending application Ser. Nos. 08/539,105; 08/724,948; 09/009,758; 08/942,990; 08/857,386; 08/896,791; 08/856,641; and 09/003,772, the full disclosures of which are incorporated herein by reference.