Such a severable sheath finds particular application when it is desired to insert a medical instrument which is not removed through the introducer. After the medical instrument is inserted into the patient, the introducer and the severable sheath are removed from around the medical instrument.

Background of the Invention It is known to utilize severable sheaths in introducers when certain medical instruments are to be inserted into a patient. An introducer with a severable sheath may commonly be used when, as one example, pacemaker electrodes are to be inserted into a patient and remain in the patient. Under these circumstances, an introducer is used to insert the pacemaker wires into the patient, and then the introducer and sheath must be removed from around the pacemaker wires.

One example of such an introducer is disclosed in U. S. Patent 4,345,606 to Littleford.

Littleford discloses that a severable sheath element can be ripped in two after a medical instrument is inserted through the introducer and sheath into a patient.

Littleford discloses the specifics of utilizing an introducer with such a sheath, and also discusses similar background sheath introducer systems. Littleford specifically discloses a sheath which is severable by including perforations, holes, through cuts, a reduced wall thickness, and integral cutting agents such as strings and the like. Littleford further discloses a specific example of utilizing an introducer with such a severable sheath in the insertion of pacemaker wires into a patient.

However, the system of Littleford suffers from a significant drawback in that each of the disclosed methods of forming the severable structure in the sheath involves a mechanical scoring operation, or mechanical variations in the manufacturing process. Such mechanical manipulations of the sheath in Littleford result in imprecise severing of the sheath. Further, such mechanical manipulations in Littleford result in significant additional manufacturing processes to the sheaths and limits in the form of the severing.

Cook Incorporated also discloses a severable sheath system in which a severable sheath can be incorporated into an introducer. Such a severable sheath system by Cook Incorporated controls a process of forming a sheath out of PTFE (Teflon) so that there is an alignment of molecules in the PTFE. As a result, the PTFE sheath disclosed by Cook Incorporated can be easily severed by merely ripping the sheath apart because of the alignment of the PTFE molecules resulting from the particular process of forming the PTFE severable sheath. This system disclosed by Cook Incorporated, however, suffers from drawbacks in that the process to form the PTFE sheath to be severable increases costs of the sheath, and further the sheath material is limited to PTFE.

OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to provide a novel severable sheath, and an introducer utilizing such a novel severable sheath, which can be formed of a wide range of materials, and which includes an easy to form perforation which allows for a smooth ripping of the severable sheath.

SUMMARY OF THE INVENTION In order to achieve the above and other objects, the present invention is a novel severable sheath which has a severable portion formed by a laser operation. The laser operation can be applied to a wide range of materials, including polyurethane, a nylon, and fluoropolymers such as PTFE, etc. Further, the laser operation can produce a precise severable portion in the sheath. The severable portion can take, as examples, the form of a score line in the sheath or holes in the sheath.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of the present invention, and many of the attendant advantages thereof, will be readily obtained as the same becomes better understood by the following detailed description when considered in conjunction with the accompanying drawings, wherein: Figure 1 shows an overall introducer utilizing a severable sheath of the present invention; Figure 2 shows the severable sheath of the present invention in isolation in an operation of splitting ; Figure 3 shows a process of forming the severable sheath of the present invention; Figures 4A-4C show different structures of a severable portion in the severable sheath of the present invention; and Figures 5A-5C show different cross-sections of a severable portion in the severable sheath of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 shows an introducer of the present invention which finds particular application in inserting medical implements into a patient which are not to be removed through the introducer. For example, pacemaker leads may have to be inserted into a patient and remain there for some time. Thus, pacemaker leads are inserted through the introducer, but then the introducer has to be removed from around the pacemaker leads.

To achieve such an operation, the introducer 1 as shown in Figure 1 includes a main hub 10 including a cap portion 12, a distal end 22, and a far distal end 28. The cap portion 12 includes a hole 13 through which a medical implement 52 is inserted. As noted above, a typical use of such an introducer of the present invention is to insert a pair of pacemaker leads as medical implement 52 into a patient. The introducer 1 further includes a sheath 5 with a severable portion 15. Further, the main hub 10 of the introducer 1 includes a partition section 20 along which the main hub 10 can break into two separate parts. Different severable hub designs are also clearly applicable to being used in an introducer with the sheath 5.

In an operation utilizing the introducer 1, assume that pacemaker leads as medical implement 52 have already been inserted into a patient. A subsequent operation after the medical implement 52 has been inserted into the patient is to remove the introducer 1 from around the medical implement 52. The first step in this operation is to break apart the main hub 10 along the partition section 20. After the main hub 10 is broken into two parts and then removed from around the medical implement 52, the sheath 5 is ripped along the severable portion 15, after which the sheath 5 is removed from around the medical implement 52.

Figure 2 shows an operation of removing the sheath 5 from around the medical implement 52 after the main hub 10 has already been removed from around the medical implement 52. As shown in Figure 2, the sheath 5 is ripped along the severable portion 15 to be removed from around the medical implement 52.

A significant feature in the present invention is how the severable portion 15 is formed in the sheath 5. In the present invention, the severable portion 15 is formed in the sheath 5 by impinging the sheath 5 with a laser beam from a laser, e. g., along a linear path on the surface of the sheath 5. The severable portion 15 is not limited to a linear path in the present invention, and one of the benefits of the present invention is being able to form severable portions of various shapes. By impinging the sheath 5 with a laser beam, a very precise severable portion 15 is formed in the sheath 5. It should also be pointed out that the severable portion 15 is not necessarily formed completely through the wall of the sheath 5, but may only be formed partially through the wall of the sheath 5. That is, the severable portion 15 can take the form of a score line of various shapes which only extends partially through the wall of the sheath 5, or the severable portion 5 can take the form of a line of holes which either only extend partially through the wall of the sheath 5 or which extend entirely through the wall of the sheath 5 to perforate the sheath 5. The formation of the severable portion 15 is discussed in further detail below. Further, by utilizing such a laser forming operation, the severable portion 15 can be formed in the sheath 5 to a size as small as 10, um. Further, forming the severable portion 15 with a laser allows the severable portion 15 to be formed in a wide range of materials for the sheath 5. For example, a severable portion 15 can be properly formed in the sheath 5 by a laser if the sheath 5 is formed of any of polyurethane, a nylon and fluoropolyers such as PTFE, etc. Moreover, by utilizing a laser to form the severable portion 15 in the sheath 5, the severable portion 15 can be formed extremely quickly and efficiently.

Figure 3 shows a process of forming the severable portion 15 in the sheath 5. In Figure 3 a sheath 5 in which a severable portion 15 is to be formed is slid over a metal tube 30. A laser source 31 outputs a laser beam 32 to then impinge on the sheath 5. Either one of the laser source 31 or the sheath 5 placed on the metal tube 30 is then moved to create a relative motion between the laser source 31 and the sheath 5 so that the severable portion 15 can be formed linearly along the sheath 5. In this operation, the laser source 31 outputs the laser beam 32 as a series of pulses which impinge on different areas on the wall of the sheath 5 as one of the laser source 31 or the sheath 5 is moved. With this operation, a severable portion 15 can be formed in the sheath 5.

Further, the distance from the laser source 31 to the sheath 5 is selected such that the focal length of the laser beam 32 output from the laser source 31 is focused at a desired depth on the wall of the sheath 5 for forming the severable portion 15. That is, in the present invention the depth of the severable portion 15 within the sheath 5 can be varied as desired (for example, based on the wall thickness of the sheath 5, the material of the sheath 5, the application of use of the sheath 5 etc.). The severable portion 15 is formed in the sheath 5 with the appropriate desired depth by positioning the laser source 31 a distance away from the sheath 5 so that the focal point of the laser beam 32 output by the laser source 31 is at the desired depth of forming the severable portion 15 in the wall of the sheath 5. The focal point of the laser beam 32 could also be changed by changing optics positioned between the laser source 31 and the sheath 5. In this way, the severable portion 15 can be formed at the desired depth in the sheath 5 by impinging the sheath 5 with the laser beam 32 output from the laser source 31.

As noted above, the severable portion 15 can take different forms in the sheath 5.

Figures 4A-4C show examples of the different forms that the severable portion 15 can take.

In one structure as shown in Figure 4A, the severable portion 15 can take the form of a score line formed in the wall of the sheath 5. When forming this score line as shown in Figure 4A as a severable portion 15, the pulse laser beam 32 is impinged on the sheath 5 with very small spacing between the different pulses so that a continuous score line is formed. In this instance, the laser source 31 is a distance from the sheath 5, or optics are provided, such that a focal point of the laser beam is a predetermined depth into the wall of the sheaths, so that the severable portion 15 is formed in the sheath 5 to a desired depth. Such a score line provides a severable portion 15 at which the sheath 5 can tear when needed.

A second structure which the severable portion 15 can take is as a series of holes 40 formed in the wall of the sheath 5, as shown in Figure 4B. In this instance, the size, spacing, and depth of each hole 40 may vary based on the distance from the laser source 31 to the sheath 5, and the selected power, beam width, and other properties of the laser beam 32 impinged onto the sheath 5. In forming the severable portion 15 as a series of holes 40, each hole 40 can be formed from one or more pulses of the laser beam 32 output from the laser source 31. In this structure, the holes 40 may be formed only partially through the wall of the sheath 5 or can be formed completely through the wall of the sheath 5 as a series of perforations. The depth of the holes 40 again can be varied based on the distance from the laser source 31 to the sheath 5 and the focal length of the laser beam 32.

A third structure which the severable portion 15 can take is a series of holes 41 which partially overlap with each other as shown in Figure 4C. In this instance, there is no spacing between adjacent holes 41, and thereby a continuous line is formed. This operation of forming the severable portion 15 as a plurality of overlapping holes 41 is similar to the operation of forming the score line discussed above with respect to Figure 4A, except to form the structure of the severable portion 15 in Figure 4C there is a greater spacing between adjacent pulses of the laser beam 32 output from the laser source 31. Thus, in structure shown in Figure 4C scalloped portions are provided on the severable portion 15 because of the partial overlap of the holes 41 corresponding to laser pulses of the laser beam 32. In this instance, the severable portion 15 is only formed partially through the wall of the sheath 5.

Again, the size, spacing, and depth of the perforation holes 41 as shown in Figure 4C can vary based on the selected positioning and parameters of the laser source 31.

Further, the cross-sectional shape of the severable portion 15 may be varied based on several parameters of the laser beam 32 impinging onto the wall of the sheath 5. For example, optics can be provided between the laser source 31 and the wall of the sheath 5 to change the shape of the laser beam 32 impinging on the wall of the sheath 5. Further, the angle at which the laser beam 32 impinges on the wall of the sheath 5 can be varied, the number of passes of the laser beam 32 onto the wall of the sheath 5 can be varied, etc.

Varying such parameters may change the cross-sectional shape of the severable portion 15 of the sheath 15. The cross-sectional shape of the sheath 5 for any of the severable portions 15 noted above may, as an example, be in a V-grooved shape as shown in Figure 5A, a rounded shape as shown in Figure 5B, or a squared-bottom shape as shown in Figure 5C.

It should also be noted that within one severable portion 15 the depth, cross-section, etc. may be varied at different portions in the same manners as discussed above, if desired.

Different types of lasers are believed to able to be utilized to form the severable portion 15. One suitable laser is a C°2 laser. When utilizing a C°2 laser, the C°2 laser can be operated at 120 watts with a 5% duty cycle and can output pulses of a laser beam with a beam width of 75 llm to form the severable portion 15 in the sheath 5. In this instance, a sheath tubing can be moved past the laser beam at 4 inches per second.

With these conditions, a severable portion 15 can be formed with a plurality of overlapping holes 41 as shown in Figure 4C. If the spacing between the CO2 laser as laser source 31 and the sheath 5 is changed, the depth of the severable portion 15 in the wall of the sheath 5 can be changed. Further, the laser beam 32 width size can also be varied to change the size of the severable portion 15, e. g., to change the width of the score line as shown in Figure 4A and the size of the holes as shown in Figures 4B and 4C.

Moreover, to achieve the different cross-sectional shapes of the severable portion 15 as shown in Figures 5A-5C, optics can be inserted between the laser source 31 and the sheath 5, an angle of the laser beam 32 impinging on the wall of the sheath 5 can be changed, the number of passes of the laser beam 32 on the wall of the sheath 5 can be changed, etc.

Obviously, numerous additional modifications and variations of the present invention are possible in view of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.