Fiberoptic Catheter

Abstract

A catheter of the fiberoptic type is disclosed for insertion into the cardiovascular system. The catheter comprises a flexible element with light-conducting fibers therein extending from one end of the element to the other. A recess is provided adjacent one end of the catheter to prevent the optical fibers from contacting a vessel wall when the catheter is inserted therein.

Description

The invention described herein was made in the course of work under a grant or award from the Department of Health, Education and Welfare.

BACKGROUND OF THE INVENTION

This invention relates, as indicated, to a fiberoptic catheter for insertion into the cardiovascular system to permit in vivo examination of intravascular and intracardiac environments which avoids the effects of wall artifact.

In recent years, developments in the field of fiberoptics have enabled immediate determinations to be made of intravascular and intracardiac blood oxygen saturation by catheterization. To make such determinations, a catheter containing a multiplicity of light-conducting fibers, which have their ends exposed adjacent the lead end of the catheter, is inserted into an artery or vein to position the ends of the fibers at a position where the determinations are required. Rapidly alternating pulses of light are supplied to a number of the fibers which emit light into the blood with the light reflected from the blood carried back through other fibers for photoelectric analysis from which determinations of the blood's oxygen saturation are made.

It has also been proposed previously to utilize a fiberoptic catheter which includes a lumen extending through the catheter to permit measurements of blood pressure. Typically, such catheters comprise a central lumen with the light-conducting fibers spaced concentrically about the lumen in the wall of the catheter.

One of the principal disadvantages in the use of such previously known fiberoptic catheters is the artifact which is created by blood flow fluctuatons and blood vessel wall reflectance. To overcome such problems, it has been proposed to utilize a metal basket in conjunction with the catheter to protect the area around the distal tip of the catheter where the reflectance signals emanate. The use of such a metal basket, which may be in the form of a wire cage, however, promotes clotting which is not only dangerous and interferes with the normal functioning of the cardiovascular system, but also interferes with the operation of the fiberoptic catheter. It is highly desirable, therefore, to provide a catheter which may be used in the determination of blood pressure and oxygen saturation and which is capable of preventing artifact at the distal tip and also prevents a non-injurious surface to the blood vessel wall which minimizes the chances of producing clotting.

SUMMARY OF THE INVENTION

The present invention is thus directed to a fiberoptic catheter which may be inserted into the cardiovascular system without incurring the effects of wall artifact. The catheter comprises a flexible element which has a multiplicity of light-conducting fibers extending therethrough and a recess at one end, whereby the tips of the light-conducting fibers are prevented from contacting a vessel wall during or after insertion therein.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the annexed drawings:

FIG. 1 is a perspective view showing the catheter of the present invention in conjunction with an optical connector;

FIG. 2 is a fragmentary cross-section view of the tip portion of the catheter taken on line 2--2 of FIG. 1;

FIGS. 3 and 4 are a fragmentary section view and a section view on line 4--4 of FIG 3, respectively, illustrating a further form of tip construction;

FIGS. 5 and 6 are a fragmentary section view and a section view on line 6--6 of FIG. 5 respectively showing yet another form of tip construction;

FIGS. 7, 8, and 9 are fragmentary section views showing further modifications of the catheter; and

FIGS. 10 and 11 are fragmentary section views illustrating the catheter with flow direction inserts positioned therein.

Referring now more particularly to FIG. 1, a catheter, indicated generally by the numeral 1, is shown which comprises an elongated flexible element 2 connected at one end to an optical connector 3 through a protective sheath 4. The optical connector is a standard item, adapted to be slidably inserted into an oximeter, and includes a plurality of openings (not shown) in side 5 through which infra-red and red light can be introduced into the catheter and emitted therefrom for determinations of oxygen saturation in the blood, as will be explained hereinafter. The connector also includes coupling element 6 for connection to a pressure transducer to measure pressure, there being an opening in connector 3 communicating with element 6 and the pressure lumen of the catheter. The element 6 may also be connected to a syringe to take a blood sample or to a saline solution to flush the catheter.

In FIG. 2, one form of tip construction of the catheter is illustrated. The catheter includes a catheter wall 10 which contains a multiplicity of light-conducting fibers 11 extending therethrough from one end of the catheter to the other. The catheter also includes a substantially central lumen 12 which likewise extends throughout the length of the catheter for pressure measurements and other uses to be explained. The catheter also includes at the forward tip a recess denoted generally by 13. In this embodiment, the recess is of a generally conical configuration and is formed by the outer surface 14 of wall 10 extending beyond the end of the light-conducting fibers and central lumen.

Due to the recess, when the catheter is inserted into a vessel wall, the light-conducting fibers will not contact the vessel wall. As explained previously, the usefulness of catheters of prior constructions is severely limited due to artifacts created at the distal tip of the catheter. The recess, however, holds the light-conducting fibers away from the vessel wall and thus reduces blood flow velocity at the tip of the fibers and minimizes velocity artifact.

The depth of the recess has been found to be quite important. In general, the recess, that is, the distance between the edge 14 of the catheter wall and the forward edge of the fiberoptics, should be from about 0.2 to about 1.5 millimeters, with the exact depth being somewhat variable depending upon the exact tip construction used and the diameter and configuration of the optical fibers which are used. A depth of about 0.5 to 1.0 millimeters has been found to be very satisfactory. The foregoing dimensions of the recess have been derived experimentally utilizing catheters of different tip constructions. In determining oxygen saturation, infra-red to red light reflected by the blood and returned through the optical fibers to the oximeter is obtained, the ratio being proportional to the oxygen saturation in the blood. Ideally, if the catheter is capable of accurate measurement, the ratio should remain substantially constant in a localized area regardless of the closeness of the catheter tip to a vessel wall, that is, the effect of blood artifact should be eliminated. It has been found that this is achieved with the recessed catheter of the present invention.

Referring now to FIGS. 3 through 6, further forms of catheter tip construction ar shown. In FIGS. 3 and 4, the catheter includes wall 20 which has a ring of light-conducting fibers 21 contained therein. A central lumen 22 is also provided, the fibers being disposed concentrically about the central lumen. The recess 23 is essentially rectangular in configuration, formed by the wall of the catheter extending beyond the end of the light-conducting fibers. In FIGS. 5 and 6, catheter 25 includes a pressure lumen 26 which is positioned in one segment of the catheter, while the light-conducting fibers 27 and positioned in a second segment opposite pressure lumen 26. A partitioning web 28 extends throughout the length of the catheter and interconnects the two segments. The recess 29, as illustrated, again is essentially of rectangular configuration, although it is to be understood that the recess may be of other shapes including a conical configuration as illustrated in FIG. 2.

FIGS. 7, 8 and 9 illustrate further modifications of the catheter of the present invention. In FIG. 7, the catheter 30 is particularly suitable for use in conjunction with a needle which would be inserted in the central pressure lumen 31 for puncturing an artery or vein to enable the catheter to be inserted therein. The catheter includes a tapered outer surface 32 as well as the light-conducting fibers 33 which are tapered at the forward end 34. The recess 35, formed between the end 36 of the catheter and end 34 of the fibers is cylindrical.

In FIG. 8, the catheter 40 includes tubular element 41 which has a pressure lumen 42 and light-conducting fibers 43 therein, connected by partitioning web 44 similar to the catheter illustrated in FIGS. 5 and 6. In FIG. 8, however, the catheter includes an opening or vent 45 in the outer surface of the tube and has an expandable sleeve 46 of neoprene rubber or other suitable thin expandable material attached thereto by clamping rings 47 and 48, which are positioned about the exterior of the catheter. It is to be understood, of course, that other means can be used to attach the expandable sleeve to the catheter including, for example, suitable bio-compatible adhesives. In this embodiment, the ends of the light-conducting fibers are sealed, as for example, with a plastic or epoxy resin, since the pressure for inflation of the expandable sleeve is introduced through such lumen and opening 45. As shown in FIG. 8, the expandable sleeve, after inflation, resembles a balloon and extends circumferentially about the catheter beyond the forward tip of the same to provide recess 49. To assist in providing a stable recess configuration and to ensure that the inflated balloon assumes the proper position, which does not change due to blood flow and wall forces exerted at the catheter tip, ring 48 extends beyond the tip 50 of the catheter to serve as a stiffener for the balloon, which extends beyond the forward edge of the catheter, when expanded, as shown at 51 to provide a recess of the previously indicated depth of about 0.2 to 1.5 millimeters.

When the catheter tip of FIG. 8 is used, the catheter is inserted into the blood vessel with the expandable sleeve in the deflated position shown in broken line. After insertion, air pressure is admitted to the catheter through lumen 42 and air vent 45 to expand the sleeve to the position shown in full line. As thus illustrated, the expanded sleeve or balloon acts as an obstruction to blood flow and generates a force on the tip of the catheter which pulls the catheter in the direction of flow, thereby flow directing the catheter tip along the path of flow through the heart chambers into the pulmonary artery. This form of the catheter is highly desirable, as acess to the pulmonary artery in many cases is a clinical necessity. Also, since the recess is formed by the inflated balloon, as described, a smooth non-injurious surface is presented to the blood vessel wall.

Although a Swan-Ganz flow directed catheter, such as that available from Edwards Laboratories Inc., has been used before, it is not a fiberoptic catheter. Moreover, in a fiberoptic catheter, care must be taken to avoid "balloon artifact," that is, having the balloon, when expanded, extend too far into the volume of blood illuminated by the fiberoptics and moving in response to flow or wall forces, thereby introducing artifact into the reflected light measurement. As indicated previously, ring 48 positioned as illustrated and the shape and stiffness of the balloon 46, assist in avoiding such problem.

In FIG 9, another form of catheter tip is shown with the catheter 55 including a plurality of flexible fingers 56 of rubber or a suitable plastic positioned at the lead end thereof. The catheter also includes a central lumen 57 and light-conducting fibers 58 as in the embodiments previously discussed. The flexible fingers are designed such that, when the catheter is inserted into the blood vessel through a sheath or needle, the fingers assume the position shown in broken line. After insertion into the blood vessel, however, the fingers are unrestrained and open out into the position shown in full line and thus provide the necessary recessed tip configuration for artifact-free performance, the recess being formed between the tip of fingers 56 and the forward edge of catheter 55. Additionally, when in the unrestrained position, the flexible fingers obstruct the blood flow and provide for flow direction of the catheter in the manner described above with respect to FIG. 8.

In FIGS. 10 and 11, further modifications of the catheter are shown, where a catheter, such as that shown in FIGS. 1 through 7, includes a flow direction insert positioned within the pressure lumen. In FIG. 10, the catheter, denoted generally by numeral 59, includes optical fibers 60 and a flow direction insert 61 extending through the pressure lumen 62. The insert comprises a wire 63 and means 64, such as resilient rubber wings, cup or bulb, on the forward end which extend radially from the wire to provide a flared obstruction for flow direction in the manner described above. In FIG. 11, the flow direction insert is a balloon 65 connected to a tubular element 66. The balloon is, of course, inflatable by application of air pressure through the tubular element. When the balloon is inserted within the catheter, it is partially inflated as shown by the broken line 67, and after insertion beyond the tip of the catheter to the desired flow direction position, the balloon is further inflated as shown at 68 to provide the obstruction to flow and flow direction previously discussed.

The flow direction inserts shown in both FIGS. 10 and 11 in the operative position have the flow direction means extending beyond the forward tip of the catheter. The advantages of the catheters of FIGS. 10 and 11 are that flow direction of the catheter in a venous system can be achieved by the inserts, and, when the catheter is in the desired position within the vein, the insert can be removed. In the FIG. 10 form, the insert would be removed simply by withdrawing the same by pulling on wire 63. In FIG 11, the insert would be removed by deflating the balloon 65 to the position shown in broken line at 69 and then withdrawing the same. After the catheter has thus been removed, the lumen is free for pressure monitoring and sampling. The provision of the flow direction inserts thus provides greater versatility for the catheters, since the insert would be used only when flow direction is desired clinically and the need for a balloon to be permanently located at the catheter tip would thus be eliminated.

The materials of which the catheters are constructed are any of those commonly used, including flexible plastics such as nylon, Teflon, vinyls such as polyvinyl chloride, polyurethane and polyethylene, or various rubber compounds. Typically, the catheter will be 5 to 40 inches long and have an outer diameter of about 1 to 2 millimeters. The pressure lumen can vary in diameter, but typically will be about one half to 1 millimeter in diameter.

Claims

1. A catheter for insertion into the cardiovascular system comprising an elongated flexible element having a multiplicity of light-conducting fibers extending therethrough, a recess formed in the distal end of the element, the recess cutting across said fibers at an angle to the longitudinal axis of the fibers, the distal end of the catheter preventing the light conducting fibers from contacting said vessel wall, and an expandable sleeve located near the distal end and on the exterior of said catheter whereby upon expansion of the sleeve, it extends beyond said element to further maintain a space between the distal end of the fibers and the end of the sleeve.