Method of Providing a Long-Lived Window Through the Skin to Subcutaneous Tissue

This invention relates to a transcutaneous access device. It relates more particularly to a device of this type to facilitate access to the body through the skin by catheters and similar percutaneous devices.

There has of late been increasing use of catheters to provide prolonged or repeated access to the internal organs of chronically ill patients. For example, catheters are used to access a patient's venous system for the administration of intravenous (IV) fluids, antibiotics, and chemotherapy. Catheters are also implanted in patients who require repeated access to the peritoneum for peritoneal dialysis.

Other than occlusion, the most common complications arising with long-standing implants are exit-site infection, tunnel infection, local abscesses and even sepsis. Many of these complications arise because the skin adjacent to the catheter does not heal to form a tight barrier to infection. Rather, epidermal cells tend to invaginate or migrate inward along the catheter and never form a tight biological seal around the catheter. Also, tunnels are created through which body fluids may exude thereby creating a site for infection.

In an attempt to overcome these problems, a catheter has been devised which includes a button-like skirt with a raised neck and a central hole for accommodating a tube. The tube has a corrugated segment extending above the button neck which allows the external portion of the tube to be flexed so as to absorb shocks. The skirt, including a portion of the neck thereof, is covered with a porous material, such as polyester velour, to allow for cell infiltration. When that device is implanted, the epidermal cells tend to migrate or invaginate downward along the neck to the skirt where they form a biological seal with the collagen and subcutaneous tissue growth on the porous covering of the button; see U.S. Pat. No. 4,886,502.

While that concept was relatively successful in animals, it has had limited success in human trials because normal body motions caused stretching of the tissue adjacent to the catheter and exerted torsion on the catheter. Such movements of the tissue relative to the button, which is held stationary by the external segment of the catheter tube, results in disruption of the biological seal between the catheter and the adjacent tissue. Such disruption may also occur when the external segment of the catheter tube is moved accidentally or intentionally when connecting and disconnecting the catheter tube to the infusate source.

Accordingly, the present invention aims to provide a transcutaneous access device for a catheter which should circumvent most of the problems caused by relative movement of the catheter and the tissue surrounding the catheter.

Another object of the invention is to provide a transcutaneous access device which, when implanted, provides a tight biological seal between the device and adjacent tissue.

A further object of the invention is to provide a device of this type which reduces the risk of infection;

Yet another object of the invention is to provide a transcutaneous access device which is relatively easy to manufacture in quantity.

Other objects will, in part, be obvious and will, in part, appear hereinafter. The invention accordingly comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the following detailed description, and the scope of the invention will be indicated in the claims.

The transcutaneous access device of this invention comprises a flat button with an opening therethrough and an integral upstanding tubular neck in registration with that opening. Formed as an integral extension of that neck is a flexible, extensible sleeve or tube whose free end is terminated by a collar which is arranged to connect mechanically to a conventional access catheter that extends all the way through the lumen formed by the sleeve or tube, neck and button of the access device.

In accordance with the invention, the lumen of the present device is large enough to provide appreciable clearance between the walls of the lumen and the access catheter so as to minimize contact between the access device and the access catheter.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is an isometric view with parts broken away of a transcutaneous access device incorporating the invention;

FIG. 2 is a sectional view with parts in elevation showing the FIG. 1 access device implanted in the body and ready for use, and

FIG. 3 is a view similar to FIG. 1 of another embodiment of the access device.

Referring to FIGS. 1 and 2 of the drawing, one embodiment of my access device comprises a flat, button-like main body or skirt 10 having a central opening 12 and an array of three to six through-holes 14 distributed around opening 12. Extending out from one side of skirt 10 in registration with opening 12 is an integral, tubular neck 16 whose lumen is in registration with opening 12. Skirt 10 and neck 16 should be stiff enough to maintain their shapes but be somewhat flexible and compliant so that when implanted they flex and "give" with the patient's dermis. In the illustrated device, the neck 16 extends out from skirt 10 at an angle; however, the neck could just as well be perpendicular to the skirt 10.

The device also includes a highly flexible, extensible tubular sleeve 22 extending from the free end of neck 16. In the FIGS. 1 and 2 device, sleeve 22 is a pleated accordion-like tube which forms a bellows and which is terminated at its free end by a cylindrical collar 24. Thus, the sleeve 22 allows the collar 24 to be moved toward and away from neck 16 in the order of 2-5 cm, as well as in all directions about the longitudinal axis of neck 16. The skirt 10, neck 16, sleeve 22 and collar 24 define a continuous, uniformly sized lumen 25 which extends through the entire device.

As best seen in FIG. 2, the collar 24 is formed with an internal lip 24a to provide a mechanical connection to an associated access catheter as will be described later.

The access device, including the skirt 10, neck 16, sleeve 22 and collar 24 are preferably formed of a flexible, thermally stable, biocompatible material such as flexible, medical grade polyurethane. The accordion-like sleeve 22 may be configured by placing a tubular extension of the neck 16 in a heated female mold and applying gas pressure inside the tube to force the tube walls to conform to the mold. The neck may then be secured to the button-like skirt 10 by welding. Alternatively, the device may be molded as a unitary part.

Preferably, the entire surface of the body or skirt 10 is covered by a porous covering or bed 26 of a material such as medical grade polyester (Dacron) velour. Such a covered skirt 10 is available as Part No. 600K61121, from the U.S. Catheter and Instrument Company of Glenfalls, N.Y. The covering encourages cell infiltration and the formation of subcutaneous tissue and collagen and thus obtains a better bond than the PTFE material used in the above patent.

Typically, when the access device is used for peritoneal dialysis, the skirt 10 is in the order of 2.5 cm in diameter, the neck 16 is about 0.5 cm long, the sleeve 22 is about 2 to 24 cm long and the diameter of the device's lumen 25 is in the order of 0.4 to 0.8 cm. On the other hand, when the device is used for vascular access, skirt 10 may be smaller, e.g., 1 cm in diameter, with the lengths of the neck and sleeve being 0.5 cm and 4 cm, respectively. In that event, the lumen 25 diameter may be in the order of 0.3 to 0.5 cm.

Referring to FIG. 2, the access device is implanted so that the skirt 10 is anchored in the subcutaneous tissue 32 and the covered neck 16 extends out through the dermal layer 34 and epidermal layer 36 of the skin S through an opening O. In time, tissue growth penetrates the through-holes 14 to help anchor the access device. Those same holes also allow for fluid drainage and for sutures to anchor the device to tissue 32. As noted previously, the covering 26 provides a porous bed to encourage the growth of tissue and collagen around the body 10 to provide a biological seal with the epidermal cells which migrate or invaginate down around neck 16 until they reach the covering 26.

The access device is designed to be used in conjunction with an access catheter or catheter tube such as the one shown generally at 42 in FIG. 2. The illustrated catheter is a vascular access catheter. However, the catheter could just as well be a peritoneal access catheter. Suffice it to say that the catheter 42 includes a tube 44 which has an internal segment 44a which extends from the skin line along neck 16 and through body 10 to a selected infusion site such as the subclavian vein. The catheter tube also includes an external segment 44b which extends from the skin line through sleeve 22 and collar 24 to a Y-fitting 46 to which is connected a pair of fluid inlet tubes 48a and 48b so as to allow fluid from two different sources to be flowed to the catheter tube 44.

When the catheter 42 is properly seated in the access device, the lip 24a of the device's collar 24 is arranged to releasably engage over a radial flange 46a usually. present at the lower end of the catheter fitting 46 to mechanically connect the catheter to the access device at the free end of the device's flexible sleeve 22. However, as noted previously, the device's lumen 25 is sized to minimize contact with the catheter tube 44 and so as not to inhibit motion of the catheter tube. Therefore, any motion of the internal catheter tube segment 44a caused by movements of the patient's body is substantially decoupled from the implanted portions of the access device, i.e., skirt 10 and neck 16. By the same token, if the external segment 44b of the catheter tube 44 should be moved accidentally or intentionally when connecting or disconnecting the catheter, the accordion-like sleeve 22 is able to flex, extend and contract as needed to accommodate such movement so that essentially no motion is coupled to the implanted portions of the access device. Resultantly, a tight biological seal is maintained between the access device and the surrounding tissue.

Indeed, actual experiments with prototype devices have shown that there are no signs of infection at the implantation sites even after the devices have been in place for prolonged periods.

Refer now to FIG. 3 which shows a second embodiment of my transcutaneous access device. It is similar to the FIG. 1 embodiment, except that its button-like skirt 50, tubular neck 52 and extensible sleeve 54 are formed as a unitary part. An annular connector member 56 which may be similar to member 24 is provided at the free end of the sleeve 54. Thus, the device has an axial passage or lumen 58 which extends the entire length of the device. A suitable material for the button-neck-sleeve unit is medical grade polyurethane sold under the designation Tecoflex EG 80A by Thermedics, Inc., Woburn, Mass.

In this case, the extensible sleeve 52 is not accordion-like. Rather, it is a thin-walled (e.g., 0.030 in.), elastic tube which can readily flex and extend lengthwise by the required amount, i.e., a few centimeters.

For most applications, sleeve 52 is more flexible and extensible than skirt 50 and neck 52. To achieve this result, the device is formed so that the skirt and neck have a greater wall thickness than the sleeve.

As in the FIG. 1 device, porous bed material is applied to exterior surfaces of the skirt 50 and neck 52. This material may be the same as or similar to the material used for bed 26 described above. Here, however, the material is applied in two parts. An annular piece 60a of bed material is slid onto the sleeve 54 and neck 52 and folded as shown in FIG. 3 so that it covers the upper surface of the skirt and encircles the neck 52. It may be secured there by any suitable adhesive. To assure placement of the material piece 60a at the correct elevation on the neck 52 indicium 62 may be molded into or inscribed around neck 52.

Another annular piece 60b of bed material is adhered to the undersurface of skirt 50, the opening through piece 60b being substantially the same size as lumen 58.

After being secured to skirt 50, the bed material pieces 60a and 60b may be trimmed so that their outer edges are even with the periphery of skirt 50.

The FIG. 3 embodiment of the device has all of the attributes of the FIG. 1 embodiment and functions in the same way described above in connection with the FIG. 1 embodiment.

As seen from the foregoing, my transcutaneous access device is, for the most part, a molded plastic part which can be made in quantity relatively easily and inexpensively. Therefore, it should find wide application wherever it is necessary to maintain catheters in situ for a long period of time.

In the course of testing my transcutaneous access device on human patients, I observed that when the device is removed after it has fulfilled its function, there remains the small, e.g., 0.4 cm, opening O through the skin formerly occupied by the covered neck 16 (or 52).

Furthermore, the epidermal cells and connective tissue joined to the collagen growth encouraged by the covering 26 form a stable infection-free barrier or wall all around opening O. While that opening may normally be closed by an appropriate skin graft. I have found that when left alone, the opening provides a permanent window through the skin to the subcutaneous tissue. It then occurred to me that this window could be used as a test site for an instrument that tests for diabetes or some other malady.

One instrument that tests for diabetes flashes ultraviolet or near ultraviolet light on the skin and detects the reflected energy. From this, the instrument calculates the patient's blood sugar level. That information is then used to determine the correct insulin dosage for the patient at that time.

The test results from instruments of this type are adversely affected because the epidermis is a very good absorber of UV light. By providing a permanent window through the skin to the subcutaneous tissue, the instrument can now illuminate that tissue directly and thus obtain a more accurate reading of the patient's sugar level.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention described herein.