Catheter Shield and Test Structure

This invention relates to catheters such as intravascular catheters and more particularly to equipment for maintaining the sterility of such catheters by physically isolating all portions of a catheter intended for insertion into a patient's blood vessel or other body cavity from the time the seal or the container in which the catheter is stored is broken, during testing and insertion and during subsequent use.

The development of apparatus and techniques for maintaining the sterility of catheters, such as thermodilution flow-directed balloon catheters used for measuring cardiac output and for obtaining other diagnostic data, has received critical attention as the use of such products has expanded. The packaging of the catheter in gas-sterilizable containers and in single-use kits having all of the items needed for insertion of the catheter and for use in carrying out the required procedure and by rigorously following sterile procedures have all contributed to a substantially reduced risk of contamination and infection. However, even when following the most rigorous procedures contamination may occur, particularly when the patient is being treated under emergency conditions. At best, a potentially contaminated catheter may have to be discarded prior to use when sterile procedures have not been followed.

A form of sterility sleeve used to maintain a portion of an indwelling catheter free from contamination for later use when it becomes necessary to re-position the catheter is disclosed in U.S. Pat. No. 4,327,723 to Paul L. Frankhouser. This sleeve is extended over a length of catheter immediately adjacent to the portion inserted into the vascular system of the patient, thereby physically isolating a reserve section of catheter from the atmosphere for use should it later become necessary to reposition the catheter.

U.S. Pat. No. 4,568,334 to Lawrence Lynn discloses a means for more comprehensive treatment of the contamination problem. In the Lynn patent, a combined storage, dispensing and preparation container is provided for an intravascular balloon catheter. The container includes a plurality of interconnected compartments in which different parts of the catheter are housed. Lynn's compartments include a test chamber for testing the integrity of the catheter balloon, an adjacent section in which a pleated sleeve is housed in what is termed a "trough compartment," a main compartment in which a substantial section of catheter may be stored and a connector compartment in which the proximal end of the catheter is located. The distal tip of the catheter is withdrawn from the test chamber once balloon integrity is tested, until the tip is located within the pleated sleeve by a pumping action of the sleeve. The pleated sleeve is then attached to a catheter introducer in place within the patient's blood vessel and the catheter is then advanced into the vessel by a reverse pumping action of the sleeve.

U.S. Pat. No. 4,622,033 to Taniguchi discloses a packaging construction for a urinary catheter comprising a lubricant reservoir and a tubular envelope or shield. A balloon-tipped urinary catheter is advanced into the lubricant reservoir prior to use. The lubricant reservoir has a frangible seal so that the reservoir can be removed once the catheter has been lubricated.

U.S. Pat. No. 4,637,404 to Gessman discloses a dispensing container for a cardiac pacing electrode in which a flexible sheath or sleeve comprising an accordion section 32 and another gathered or accordion section 34 is provided for advancing the electrode by grasping the wire through the sleeve.

The primary object of the present invention is the protection of a vascular catheter from contamination during testing and insertion of the catheter in a manner which maintains a substantial portion of the catheter not indwelling in the patient in physical isolation from the atmosphere for subsequent use as may be later required. A related object is the provision of a simple and effective means for testing, insertion and re-positioning of a vascular catheter in a way which always isolates the catheter from the hands of attending personnel as well as from airborne contaminants.

A still further object of the invention is the provision of simple and relatively inexpensive components for accomplishing the objectives just above mentioned.

A still further object of the invention is the provision of equipment for straightforward and trouble-free testing and insertion of a balloon-tipped vascular catheter which lends itself to unassisted use by a single attendant.

A still further object of the invention is the reduction in the number of catheters which must be discarded due to accidental contamination during testing and insertion of a vascular catheter.

Other objects and advantages of the invention will become apparent upon reference to the following detailed description of a preferred embodiment of the invention.

In the drawings,

FIG. 1 is a view showing a catheter equipped with protective envelopes according to the invention, as the catheter is removed from its container and in condition ready for testing and subsequent use;

FIG. 2 is a fragmentary view showing, in perspective, portions of the structure of FIG. 1;

FIG. 3 is a sectional view of the portion of the structure illustrated in FIG. 2; and

FIG. 4 is a view partly in section showing the catheter as the distal tip has just entered a blood vessel, such as the internal jugular vein;

FIG. 5 is a sectional view through line 5--5 of FIG. 4; and

FIG. 6 is a view similar to FIG. 4, showing the catheter and the sleeve as the catheter is advanced further along into the blood vessel.

Although the catheter illustrated in FIGS. 1-6 is a conventional four-lumen thermodilution catheter, other types of catheter may be advantageously provided with the sheath and test chamber construction of the present invention. Briefly stated, and by way of background, the catheter illustrated comprises an elongated flexible tubular body member 10 which typically has four passageways or lumens extending lengthwise therein. Body member 10 preferably has a pre-curved region adjacent the tip which is provided as an assistance to proper catheter placement as will be understood by those skilled in the art. Separately formed tubes or lumens 11-14 are respectively joined to the lumens of the catheter body member at the proximal end thereof within a molded fitting 15. Typically the tubes 11-14 are independently heat fused or adhesively joined to the lumens integrally formed within the body member so that four independent, non-communicating passages are formed. The proximal ends of the tubes 11, 12 and 14 are provided with Luer adapters or fittings 16-18 for connection to fluid devices. Fitting 18 is provided with a shut-off valve 19 for purposes to be explained hereinafter. The lumens joined to tubes 11 and 12 extend respectively to a port 20 at the catheter's distal tip and to a port 21 which is spaced approximately 30 centimeters from the distal tip. These lumens provide unimpeded flow passages for injecting fluids into the blood stream or for taking pressure measurements in a manner known in the art. The lumen joined to tube 13 houses leads for a thermistor 22 disposed within a port located within the pre-curved region on the inner side of the radius about 4 centimeters from the catheter's distal tip. The thermistor measures a change in temperature of a fluid ejected into the bloodstream through port 21 to provide a measurement of cardiac output as is well understood by those skilled in the art. For temperature measurement, the proximal end of tube 13 is equipped with an adapter 23 which houses an electrical connector for connecting the thermistor to suitable temperature-monitoring equipment. Finally, the lumen joined to tube 14 leads to the inflatable balloon 25 located just adjacent to the distal tip of the catheter. This lumen provides an uninterrupted flow passage for injecting an inflation media applied through adapter fitting 18 for inflation of the balloon 25. Valve 19 provides a means for closing this lumen once the balloon is properly inflated and allows for its deflation, as required. The catheter is also provided with suitable markings 26 at 10-centimeter intervals which give an indication to the user of the length of the catheter which has been inserted into the patient's blood vessel.

In carrying out the invention, there are two interconnected tubular envelopes provided for physically isolating all portions of the catheter that are liable to be inserted into the vascular system of the patient. The catheter is physically isolated from the atmosphere during testing of the balloon and flushing of fluid through the lumens by both envelopes. After testing, the distal end of the catheter is physically retracted into one of the envelopes and the other is discarded. During insertion, all portions not within the vascular system are protected by the remaining envelope. Still further, a substantial length of catheter is isolated for use during the time the catheter remains within the patient's vascular system. This reserve section is thus available in physical isolation within one of the envelopes without risk of contamination by the patient or attendants so that it may be used when repositioning the catheter as may be required. In its preferred form, the first envelope comprises an elongated flexible transparent tubular sheath 30 formed of a sheet-like impervious material which readily yields to finger pressure. The sheath surrounds the catheter and extends from a point adjacent the proximal end where it is secured to the catheter preferably via coupling means 31 comprising a hub 32 having a bore through which the catheter is passed. The hub is secured to the catheter by adhesive or other suitable means in a manner providing a substantially impervious seal. Hub 32 tightly interfits with a cylindrical coupling element 33. The parts are preferably locked in place by means of a slot 33a which receives a locking pin 32a projecting from hub 32. The proximal end of sleeve 30 fits over and is tightly secured to coupling element 33 by any suitable means such as elastic "O" ring 34 or by shrink fitting the sleeve directly onto the coupling element.

The distal end of sleeve 30 is secured to a second coupling means comprising coupling element 35 which has a throughbore 36 as shown in FIG. 3 which is sized to allow free passage for the catheter 10. Sealing means such as used in holding the proximal end of the sleeve on coupling element 33 affixed to the distal end of the sleeve to coupling 35. FIGS. 1-4 and 6 show an elastic "O" ring 37 for this purpose.

As can be seen in the drawings, particularly FIGS. 1, 4 and 6, the sleeve 30 is of large enough diameter relative to the catheter and is readily collapsible so that a substantial amount of relative axial movement can be achieved easily with the excess sleeve material being gathered or bunched up upon the catheter upon movement of the sleeve ends towards one another and being readily ungathered as the sleeve ends are separated. In overall length, the sleeve is capable of extension from a fixed point at 31 to the distal tip of the catheter.

Preferably a section of relatively flexible, somewhat resilient, plastic tubing 39 formed of polyurethane or the like extends rearwardly from the fitting 35 within sleeve 30. The tubing 39 is formed co-axially of the throughbore 36 and is dimensioned so that the catheter passes freely. The tubing 39 should have sufficient flexibility and resilience so that the application of a moderate amount of finger pressure exerted through sleeve 30 onto the outside walls of the tubing will compress the walls against the catheter, holding it in position against relative movement for reasons which will appear hereinafter.

The second envelope comprises a test chamber within which the distal portion of the catheter is to be positioned so that certain required tests, such as balloon inflation testing and catheter lumen patency, can be carried out and viewed in physical isolation from the environment immediately prior to use of the catheter. With reference to FIG. 1 which illustrates the position in which the catheter appears when the lid stock of the package in which it is stored in sterile condition is removed, the test chamber of the preferred embodiment of the invention comprises an elongated tube 40, preferably formed of transparent material so that the distal end of the catheter is exposed to view. When used with a catheter having a balloon at its distal tip, tube 40 has an enlarged end which may take the form of a separate cup or receptacle section 41 joined thereto, which is also preferably formed with a transparent wall section as shown in FIG. 1, which illustrates the position in which the catheter is ready to be tested. In this condition it is noted that the distal catheter tip with balloon 25 in the uninflated condition is preferably already within the cup 41 and the ejectate lumen 21 is within the tube 40. As is shown in FIGS. 2 and 3, the interior of the cup section 41 is large enough to provide ample clearance when the balloon is fully inflated. A vent is conveniently located in lid 42 as seen at 42a in FIG. 2, although a vent opening may be provided in other locations and in some instances may be unnecessary. Tube 40 may be a rigid tube with a pre-formed bend to accommodate the pre-formed bend common to pulmonary artery catheters, in its preferred form a flexible transparent tubing formed of polyurethane or the like is utilized. The flexible tubing is packaged with its end curved to the curvature of the distal end of the catheter having the pre-formed bend and it has been found that such tubing will take a nice set when sterilized after being positioned in the package with the required curvature. In FIG. 3, the curvature is not to scale and is somewhat exaggerated, it being shown for illustrative purposes only.

In order to releasibly interconnect the two envelopes, the proximal end of tube 40 carries a coupling hub member 43 which is of cylindrical shape so as to tightly fit into the cylindrical cavity 44 of coupling member 35 as may be best seen in FIGS. 2 and 3. Preferably a resilient sealing ring 45 fits within a recess 46 in the outer cylindrical wall of coupling member 43. Sealing ring 45 presses against the inner wall surface of the cylindrical cavity 44, providing a substantially air-impervious seal. The members are preferably locked together by releasible locking means which preferably comprises an L-shaped bayonet slot 47 on one member which receives pin 48.

As can best be seen in FIG. 1, the combined length of the envelope comprised of tube 40 and cup 41 is sufficient to extend proximally of catheter ejectate port 21 when the catheter is positioned with its distal tip within cup 41. As seen in FIGS. 2 and 3, tube 40 has a large enough internal diameter relative to catheter 10 to allow for free flow of liquid downwardly into cup 41 when the cup is held below the level of the ejectate port.

As indicated above, the catheter is packaged with the two envelopes interconnected by the coupling parts 35 and 43 so that a section of catheter (hereinafter sometimes called the "insertion zone"), comprising the entire length of the catheter running from the distal tip that is liable to be inserted into the patient's vascular system, is physically isolated from the ambient. When the lid stock is removed from the container tray (not shown) within which the catheter and other items needed for its use are housed, all portions, except for that portion proximal of the fitting 31, are thus in physical isolation. The user removes the assembly comprising the catheter housed within its protective envelopes from the tray and commences the test procedure, positioning the test chamber envelope below the level of the remainder of the catheter. By injecting saline solution through the fitting 16, one can visually observe the flow of solution which flows down tube 40 from ejectate port 21, thus simultaneously flushing the lumen 11 and verifying that it is unobstructed. During this phase of the test procedure, the tube 10 and the receptacle 41 are allowed to incline downwardly so that saline solution flowing out through port 21 freely flows towards receptacle 41. The user next injects saline solution through Luer fitting 17 and tubular lumen 12 thus flushing this lumen and filling the receptacle with saline solution. The balloon is then inflated by injecting a charge of inflation medium through Luer fitting 18. The balloon can be visually observed through the clear walls of cup 41. Symmetry of the balloon can be seen and leaks detected through the presence of bubbles flowing upwardly through the clear saline solution. If no leaks are detected and the balloon is seen to be appropriately symmetrical, the balloon is thereupon deflated. The distal end of the catheter is now ready to be extracted from the envelope comprising the test chamber.

To retract the catheter from the test chamber comprising tube 40 and cup 41, the front hub 35 is held by one hand and the rear hub by the other and the bunched material of sleeve 30 extended by physically separating the hubs. Since the sheath is as long as the catheter, the distal catheter tip is now within the hub 35. As the catheter is withdrawn from the test chamber, a resilient wiper 44a shown in FIG. 3 squeegees saline solution from the catheter back into the test chamber.

The test chamber is then removed by disconnecting coupling member 43 from coupling member 35 and discarded. The catheter is now ready for insertion into the vascular system of the patient.

Although the catheter may be inserted into a blood vessel by use of other techniques, it is preferably introduced using a standard sheath introducer 50 of known construction (FIGS. 4 and 6). As is known in the art, introducer 50 comprises a hollow valve body 51, and a thin walled sheath 52 which is adapted to be inserted into a blood vessel as schematically shown in FIGS. 4 and 6. The introducer assembly also includes a soft rubber hemostasis valve 53, located within hollow valve body 51 to inhibit back-bleeding. The valve is provided with a narrow slit, not shown, which is biased to close when catheter 10 is not in place and yields to form a seal around the catheter when the latter is introduced. Body 51 is further provided with a side port 54 which communicates with the interior of sheath 52 for fluid replacement and blood sampling if necessary prior to and during placement of the catheter.

The front connector element 35 is sized to interfit with a male connector 55 formed integrally with valve body 51. The connector parts are configured to provide a seal against air or airborne contaminants.

FIG. 4 illustrates the catheter with its distal tip advanced to a point just beyond the distal end of sheath 52. In order to advance the catheter, it is grasped through the sheath between the thumb and forefinger of one hand at a point five to ten centimeters behind hub 35 and gently pushed forwardly so that the distal tip passes through the introducer into the blood vessel. At the end of each forward stroke by the one hand the grip on the catheter is relaxed and the thumb and forefinger of the other hand apply pressure through tube 39 to hold the catheter in place while the gathered material of sheath 30 is moved away from the hub 35 in a reverse stroking motion. A series of forward and reverse strokes, while holding the catheter against movement on each reverse stroke, effect advancement of the catheter to the wedge position. If re-positioning becomes necessary, a reserve section of catheter extended from front hub 35 to rear hub 32 is always maintained in contamination-free condition.

The catheter may be partially withdrawn during re-positioning with the same series of forward and reverse strokes with the exception that the catheter is grasped with the thumb and forefinger of the stroking hand on the reverse stroke and held against movement by pressure exerted through tubing 39 by the thumb and forefinger of the other hand on the forward stroke. To effect complete withdrawal proximal hub 31 may be grasped and gently pulled backwardly until the catheter is fully retracted into sheath 30 or the distal hub 35 may be disconnected from the introducer and the catheter directly grasped and withdrawn.

Through use of the two envelopes, it can be seen that all portions of the catheter which may be introduced into the vascular system can be protected from external contamination from the time of sterilization until the catheter is withdrawn from the patient. During testing the balloon and all fluid flow ports on the body of the catheter are within the envelope comprising the test chamber and can be readily inspected and tested prior to catheter use. Saline solution flushed through ports 20 and 21 is confined to the test chamber. Following testing and immediately prior to use, all portions of the catheter are within the other envelope. In emergency conditions, the catheter can be tested and manipulated even without protective gloves should that be necessary.