Flattened collapsible vascular catheter

An apparatus and method for establishing a collapsible infusion conduit in a blood vessel includes a catheter formed as a normally-flattened tube of flexible, collapsible plastic. When placed in a blood vessel, the catheter collapses to a flattened configuration for lying along the wall of the blood vessel to avoid obstruction to blood flow. During infusion, infusion fluid expands the catheter to a generally oval flow path. The catheter may be initially placed in the blood vessel by pre-loading the catheter over a guide wire and inserting the catheter and guide wire through an introducer sheath into the blood vessel. Infusion fluid is thereafter applied to the trailing end of the catheter to expand the catheter to facilitate withdrawal of the guide wire. Alternatively, the leading end of the catheter may initially be sealed, and placement into the blood vessel is achieved through an introducer sheath by inflating the catheter with pressurized fluid to temporarily render the catheter rigid and generally oval. The seal at the leading end of the catheter is thereafter opened, either by inserting a guide wire into the catheter to pierce the sealed end, or by increasing the inflation pressure to burst a weakened break line formed at the leading end of the catheter.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to catheters inserted into the 
vascular system for extended periods of time, and more particularly, to a 
collapsible catheter for insertion into a blood vessel, and methods for 
placing such collapsible catheter into the blood vessel. 
2. Description of the Related Art 
Insertion of catheters into the vascular system of humans and animals is a 
commonly performed procedure. These catheters function as a conduit for 
infusion of fluids or drugs. When a catheter needs to be in place for 
greater than three or four days, it is common to place a so-called central 
line catheter, and to locate the leading tip of the catheter in one of the 
major veins at the top of the chest leading to the heart, such as the 
subclavian vein or the major veins of the mediastinum. In some instances, 
but less commonly, catheters are passed from the lower half of the body 
into the inferior vena cava. Central catheters are usually passed into the 
subclavian vein, jugular vein, or into an antecubital vein at the elbow. 
Such central catheters may have single or multiple lumens, and are 
typically made from a relatively rigid plastic material with a standard, 
round cross-section, both to facilitate placement of the catheter into the 
vein and to prevent the catheter lumens from collapsing within the vein. 
Generally speaking these catheters are constructed in such a way that the 
lumen or lumens extending therethrough retain their cross-sectional 
configuration unless an external mechanical force compresses the catheter. 
A complication of placing a central line catheter is the formation of clots 
on the wall of the catheter located in the vascular system. Blood clots 
form for several reasons. The presence of any object occupying space 
within a blood vessel causes turbulence and slowing of the blood flow 
through the vessel, and these factors induce the formation of clots. 
Generally, the greater the cross-sectional area of the catheter relative 
to the blood vessel, the greater the induced turbulence and slowing of the 
blood. In addition, the catheter is a foreign body, and the surface of the 
catheter in contact with blood acts as a nidus for clot formation. Once 
again, the greater the amount of surface area of the catheter or other 
foreign body in contact with the blood, the more likely that clots will 
form. 
Such clots can break away and flow in the blood stream to the heart and 
lungs, causing severe complications. Furthermore, the formation of clots 
can often cause such veins to become irreversibly damaged and thrombose, 
preventing further blood flow through such veins. This may ultimately 
cause debilitating swelling of the limb being drained by these veins. 
Apart from the risks of forming clots within the blood vessel, present 
central line catheters also suffer from susceptibility to clotting within 
the catheter itself. In this regard, blood enters the lumen of the 
catheter and forms a clot within the lumen, obstructing the passage of 
fluids through the catheter into the vein, and thereby rendering it 
unusable. While such clots may not be life threatening to the patient, 
blockage of the catheter can require removal and replacement of the 
catheter, a procedure which poses an inconvenience to both the patient and 
the attending physician, and adds to the cost of maintaining venous 
access. 
U.S. Pat. No. 5,176,659 issued to Mancini discloses an expandable 
intravenous catheter which has a lesser diameter during insertion into a 
vein, and which is thereafter expanded following placement to a larger 
diameter. While such device simplifies insertion of the catheter, it still 
maintains a sizable obstruction within the vein with a significant exposed 
surface area, and it still permits blood to enter the lumen of the 
catheter in the absence of fluid flow. 
U.S. Pat. No. 5,106,368 to Uldall et al. discloses a dual lumen catheter 
for vascular access. The distal portion of the catheter includes two 
tubular members attached to each other, only one of which is collapsible 
The catheter is inserted into a blood vessel through a peel-away sheath, 
and over both a stiffening cannula and a guide wire. The collapsible lumen 
returns to its original circular shape once placed in the blood vessel. 
Thus, no reduction of the cross-sectional area, or surface area, of the 
catheter is achieved after the catheter is placed. In addition, blood can 
still enter both lumens of the catheter in the absence of fluid flow. 
U.S. Pat. No. 4,406,656 issued to Hattler et al. discloses a multi-lumen 
catheter adapted to be inserted through the center of an insertion needle 
into the vein of a patient. The catheter disclosed by Hattler et al. 
includes two or more collapsible lumens formed around a flexible, but 
non-collapsible, central lumen. The collapsible lumens expand outwardly 
under the pressure of fluid flow and collapse to a smaller cross-sectional 
area in the absence of fluid flow. However, the central lumen of the 
Hattler et al. device is formed of materials which retain the shape of the 
central passageway whether or not fluids flow therethrough. Thus, even 
when the collapsible lumens are collapsed, the device disclosed by Hattler 
et al. still approximates the cross-sectional area of a conventional 
single lumen catheter. Indeed, Hattler et al. state that the central lumen 
of the disclosed multi-lumen catheter requires a certain degree of 
stiffness or rigidity to provide sufficient structural support so that the 
catheter can be handled as are conventional catheters. While the device 
disclosed by Hattler et al. somewhat reduces the cross-sectional area of a 
multi-lumen catheter, it does not reduce the cross-sectional area or 
surface area of the catheter below that of a conventional single lumen 
catheter, nor does it prevent blood from entering the central, 
non-collapsible lumen in the absence of fluid flow. 
Accordingly, it is an object of the present invention to provide a central 
line catheter which reduces the likelihood of the formation of clots 
within the blood vessel into which the catheter is placed. 
It is another object of the present invention to provide such a catheter 
which presents a minimal cross-section obstruction to the normal flow of 
blood within the blood vessel when the catheter is not being used for 
infusion, while providing a satisfactory flow path to infused fluids 
during infusion procedures. 
It is still another object of the present invention to provide such a 
catheter which minimizes the surface area of the catheter exposed to the 
blood when infusion procedures are not being performed. 
It is a further object of the present invention to provide such a catheter 
which minimizes the likelihood of blood entering the lumen of the catheter 
and forming a blockage therein. 
A still further object of the present invention is to provide a method for 
conveniently placing such a catheter within the desired blood vessel using 
commonly available vascular apparatus. 
These and other objects of the present invention will become more apparent 
to those skilled in the art as the description of the present invention 
proceeds. 
SUMMARY OF THE INVENTION 
Briefly described, and in accordance with the preferred embodiments 
thereof, the present invention is a collapsible vascular infusion catheter 
apparatus for providing an infusion passage into a blood vessel while 
occupying minimal space, and presenting minimal surface area within the 
blood vessel, when infusion is not being conducted. The catheter of the 
present invention includes at least first and second elongated, generally 
flattened strips of flexible material; suitable flexible material include 
without limitation plastic sheets formed of polyethylene, polyethylene 
teraphthalate, and polyvinyl chloride. The respective sides of the first 
and second strips are joined with each other to form an elongated, 
normally-flattened tube having an inner lumen and having first and second 
opposing ends. The first, or trailing, end of the tube is adapted to 
receive fluid to be infused into a blood vessel of a patient, and the 
second, or leading, end of the tube provides an exit port through which 
fluid received at the first end of the tube can be introduced into a blood 
vessel of a patient. 
The normally-flattened tube expands toward a generally oval shape, 
depending upon the rate of infusion, when fluid is infused into a blood 
vessel of a patient, thereby providing an open path for the infusion 
fluid. When the infusion procedure is terminated, the tube collapses back 
to a generally flattened configuration for lying adjacent a wall of the 
blood vessel. In this manner, the tube presents minimal cross-sectional 
obstruction to the flow of blood within the blood vessel, and also 
presents minimal surface area exposed to the blood flowing in the blood 
vessel. In addition, the tube acts like a valve by sealing the tip of the 
tube when the tube collapses to prevent blood from entering the lumen of 
the catheter. 
The preferred embodiment of the above-described catheter includes a 
radiopaque marker to allow the catheter to be viewed by X-ray or 
fluoroscope to ensure that the catheter has been positioned within the 
selected blood vessel as desired. This radiopaque marker may take the form 
of a radiopaque stripe applied to one face of the tube, a radiopaque 
marker located at the leading end of the tube, or a radiopaque wire 
extending along one seam of the catheter. 
Alternate embodiments of the present invention include similarly 
collapsible catheters having two or more lumens formed therein. For 
example, a second lumen may be provided by including a third elongated, 
generally flattened strip of the same flexible material extending 
generally along at least one of the first and second strips, and joining 
the respective sides of third strip with those of the first and/or second 
strips to form a second elongated, normally-flattened tube having a second 
lumen in parallel with the first lumen. 
In order to facilitate handling of the first, or trailing, end of the 
catheter after placement, and to prevent unintended damage to the tube at 
the skin entry point, the first end of the tube may include a more rigid 
skin entry portion extending from the hub of the catheter to the entry 
point of the blood vessel. 
Another aspect of the invention relates to the apparatus and method for 
placing the catheter within the patient's blood vessel. One such procedure 
uses a cylindrical guide wire initially extending through the lumen of the 
normally-flattened tube to rigidify the tube and to shape the tube into a 
generally oval shape for insertion into a blood vessel of the patient. The 
catheter is pre-loaded over the guide wire prior to insertion, with the 
tip portion of the guide wire extending through and beyond the exit port 
of the tube. An entry path is established through the patient's skin into 
a blood vessel, as by placing an introducer sheath using standard 
angiographic techniques. The guide wire and the leading end of the tube 
are inserted as a unit through the entry path and into the blood vessel. 
The catheter and guide wire are advanced together through the blood vessel 
to a desired location using fluoroscopic, ultrasonic, or X-ray guidance. 
Following insertion in the manner described above, the introducer sheath is 
removed (assuming that one was used), while temporarily leaving both the 
guide wire and catheter in place. The guide wire is then removed from the 
tube while leaving the second, or leading, end of the tube within the 
blood vessel at the desired location and allowing the inserted portion of 
the tube to collapse against the wall of the blood vessel. To facilitate 
the release of the guide wire from the lumen of the tube, the present 
invention may include a mechanism for temporarily infusing fluid into the 
first, or trailing, end of the tube while the guide wire is present within 
the catheter for expanding the tube. The infused fluid expands the tube, 
freeing the tube from the guide wire, thereby allowing the guide wire to 
be more easily withdrawn by pulling the same from the first end of the 
tube. 
An alternate procedure for placing the collapsible catheter of the present 
invention in a selected blood vessel involves the initial formation of a 
seal at the second, or leading, end of the tube for allowing the tube to 
be inflated by fluid under pressure. The seal initially formed at the 
second end of the tube is adapted to be broken for providing the exit 
port. After establishing an entry path through the patient's skin into the 
blood vessel, an introducer sheath is inserted through the entry path and 
into the blood vessel. The introducer sheath provides an entry passageway 
into a blood vessel into which the tube is to be placed. Next, a device 
for applying a fluid under pressure, such as a syringe, is releasably 
coupled to the first end of the normally-flattened tube to rigidify the 
tube and to temporarily form the tube into a more oval shape to facilitate 
passage of the tube through the introducer sheath for placement within the 
blood vessel. The leading end of the tube is then inserted into the 
introducer sheath and into the blood vessel while maintaining the fluid 
within the tube under pressure. Once the catheter has been advanced to the 
desired location using fluoroscopic, ultrasonic, or X-ray guidance, the 
introducer sheath is removed from the entry path while leaving the tube 
within the blood vessel. 
Before the catheter placed in the above-described manner can be used, the 
seal initially formed at the second end of the tube must first be broken 
for allowing fluid within the tube to exit into the blood vessel. In one 
embodiment of the present invention, a seal-breaking apparatus is inserted 
into the tube after the syringe or other pressure application mechanism is 
removed. The seal-breaking apparatus is extended along the length of the 
tube to a point proximate the second end of the tube for opening the seal 
at the second end of the tube. Such a seal-breaking apparatus may include 
a simple guide wire which is inserted into the tube along the length of 
the tube to a point proximate the second end of the tube for piercing the 
second end of the tube. 
In another embodiment of the present invention, the seal formed at the 
second end of the tube is broken remotely by further increasing the 
inflation pressure applied to the tube. In this embodiment, the seal 
initially formed at the second end of the tube includes a weakened break 
line that ruptures when fluid pressure within the tube exceeds a 
predetermined value. During placement of the catheter into the blood 
vessel through the introducer sheath, the fluid pressure is maintained 
below this predetermined value to avoid premature rupture of the seal. 
Once the catheter is properly placed, the fluid pressure is increased up 
to the predetermined burst value to rupture the seal along the weakened 
break line for providing the exit port.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates a first embodiment of a fully-collapsible venous 
infusion catheter apparatus for providing an infusion passage into a vein 
in accordance with the teachings of the present invention. While the 
preferred embodiment of the present invention described herein is placed 
in a vein, the present invention is not intended to be limited to use with 
veins, but should be understood to extend to any blood vessel. The 
collapsible catheter is designated generally by reference numeral 20 
within FIG. 1, and includes a leading open end 22 and an opposing trailing 
end 24. Leading end 22 provides an exit port through which fluid received 
at trailing end 24 can be introduced into a vein of a patient. Trailing 
end 24 terminates in a conventional rigid plastic body 26 having a knurled 
collar or hub 28 to facilitate handling. A conventional luer lock 
connector fitting 30 is provided at the end of body 26 for connection to 
syringes, infusion lines and the like for receiving fluid to be passed 
through catheter 20 to exit port 22. 
Referring to FIG. 3A and 3B, the collapsible portion of catheter 20 
includes a first elongated, generally flattened strip 32 of flexible 
material having first and second opposing sides 34 and 36. First strip 32 
extends the length of catheter 20 from trailing end 24 to leading end 22. 
The collapsible portion of catheter 20 also includes a second elongated, 
generally flattened strip 38 of flexible material having first and second 
opposing sides 40 and 42, and like first strip 32, extends the length of 
catheter 20 from trailing end 24 to leading end 22. First side 40 of 
second strip 38 is joined with the first side 34 of first strip 32; 
likewise, second side 42 of second strip 38 is joined with the second side 
36 of first strip 32 to form an elongated, normally-flattened, collapsible 
tube 44 having opposing ends 22 and 24. 
Tube 44 is shown in its collapsed configuration in FIG. 3A prior to 
placement in a vein. Within FIG. 3D, tube 44 is shown collapsed against 
the inner wall of vein 46 following placement in the vein, and in the 
absence of fluid flow therethrough. This is the configuration which the 
inventor anticipates tube 44 will assume in the vein in the absence of the 
flow of infusion fluid therethrough. In this collapsed configuration, tube 
44 occupies minimal space within the vein when infusion is not being 
conducted, and therefore causes minimal turbulence and slowing of blood 
flow within vein 46. In addition, because almost one-half of the surface 
of tube 44 lies adjacent the wall of vein 46 when in the collapsed 
condition shown in FIG. 3D, the amount of surface area of tube 44 exposed 
to blood flow within vein 46 is minimized. All of these features lessen 
the likelihood of blood clot formation within vein 46. In addition, since 
exit port 22 of tube 44 also assumes the collapsed configuration shown in 
FIG. 3D in the absence of fluid flow, blood is prevented from entering the 
lumen of tube 44 between infusion procedures, thereby lessening the 
possibility for clots to form within the lumen, and the resulting blockage 
of infusion fluid. Thus, the collapsible leading end of tube 44 functions 
like a one-way flap valve to permit infusion fluid to escape therefrom and 
to prevent blood from entering therein. 
As shown in FIGS. 3B and 9B, tube 44 can be expanded by infusing fluid 
through tube 44. The normally-flattened tube 44 expands to a generally 
oval shape when fluid is infused into a vein of a patient, thereby 
providing a sizable cross-sectional path for fluid to be passed into the 
vein. When infusion is terminated, tube 44 collapses back to the generally 
flattened configuration shown in FIG. 3D for lying adjacent the wall of 
the vein. 
While strips 32 and 38 have been described as discrete strips joined along 
their respective sides, it should be understood that strips 32 and 38 may 
be integrally formed with each other, and that the described joinder of 
the side edges of such strips may, in fact, constitute the formation of 
pleats or folds in what is otherwise a single, smooth continuous surface. 
Suitable materials for forming strips 32 and 38 include strong but 
flexible plastic films, including those made of polyethylene, polyethylene 
teraphthalate, and polyvinyl chloride. In the preferred embodiment of the 
present invention, these plastic films are inelastic, although plastic 
films which exhibit elasticity might also be used. 
Referring back to FIG. 1 tube 44 includes a skin entry portion 48 extending 
adjacent trailing end 24 of tube 44, and adjacent hub 28; this skin entry 
portion ultimately extends through the skin of the patient at the point of 
entry following placement of the catheter. If desired, this skin entry 
portion 48 of tube 44 may be made relatively rigid for a length of 
approximately eight to ten centimeters, as measured from hub 28, to 
facilitate handling of the catheter by medical personnel following 
placement, and to prevent damage to catheter 20 from long term 
manipulation. 
As noted above, it is desired to make the majority of tube 44 that lies 
within the vein fully collapsible. However, a catheter that has no 
rigidity is almost impossible to insert into a vein as compared with a 
catheter which has rigidity. Accordingly, another aspect of the present 
invention relates to the apparatus and method used to place such a fully 
collapsible catheter within a vein. One such apparatus and method is shown 
in FIGS. 1 and 3C, wherein catheter 20 is pre-loaded onto a cylindrical 
guide wire 50 that initially extends through normally-flattened tube 44 to 
rigidify tube 44 and to temporarily shape it into a generally oval shape 
for insertion into the vein of a patient. As used in this specification 
and within the claims which follow, the term generally-oval should be 
understood to include cylindrical shapes. FIGS. 3C, 9A, and 9B illustrate 
the space within tube 44 surrounding guide wire 50 as being relatively 
large for clarity and to simplify the drawings. In practice, the inventor 
anticipates that guide wire 50 would closely approximate the internal 
"diameter" of tube 44, thereby providing a relatively close fit between 
tube 44 and guide wire 50 to avoid bunching of tube 44 along guide wire 50 
during insertion. Guide wire 50 has a tip portion 52 which extends through 
and beyond exit port 22 of tube 44 during insertion. 
Prior to insertion of catheter 20 and guide wire 50 into the vein of the 
patient, a guide wire diaphragm/side infusion port device 54 is slid over 
the trailing end of guide wire 50, as shown in FIG. 1. As shown best in 
FIGS. 4 and 5, device 54 includes a split seal diaphragm 56 secured 
thereto by a threaded cap 58 having a central bore 60 formed therein. 
Guide wire 50 extends through bore 60 and is wipingly engaged by split 
seal diaphragm 56 to prevent the loss of blood or infused fluid around 
guide wire 50. Device 54 also includes a side port 62 which is preferably 
provided with a luer lock connector fitting 64 for receiving a syringe or 
other source of infusion fluid. As shown in FIGS. 2 and 4 device 54 also 
includes a luer lock fitting 65 which is engaged with mating luer lock 
fitting 30 of catheter 20 to form a fluid tight seal therebetween. 
Next, an entry path is established through the skin. Such an entry path may 
be established, by way of example, using the Seldinger technique or 
modified Seldinger technique, both of which are well known to those 
skilled in the art. For example, using the modified Seldinger technique an 
introducer sheath is inserted through the skin into the vein, providing a 
convenient passage for inserting the guide wire 50 and catheter 20, as a 
unit, into the vein. Proper placement of the leading end 22 of the 
catheter can be confirmed using X-rays, fluoroscopy, or ultrasound 
provided that a radiopaque marker stripe 66, like that shown in FIGS. 6 
and 7, is formed upon and along one of flattened strips 32 or 38 of tube 
44. Alternatively, a radiopaque wire 68 can be incorporated within a seam 
or pleat of tube 44 for extending along the tube, as shown in FIG. 11. 
Once proper placement of the catheter tip is confirmed, guide wire 50 is 
removed. However, as shown in FIGS. 3C and 9A, guide wire 50 closely 
approximates the internal diameter of tube 44, and excessive friction 
between guide wire 50 and tube 44 could dislodge tube 44 from its desired 
position within the vein and/or cause kinks in catheter 20. Accordingly, 
prior to removal of guide wire 50, a syringe 70 or other mechanism for 
injecting a fluid is coupled to side port 62 of diaphragm device 54, as 
shown in FIG. 10, for injecting fluid into the lumen of tube 44. As 
indicated in FIG. 9B, the injected fluid 72 further expands tube 44 and 
moves the internal walls thereof away from guide wire 50 while 
additionally lubricating guide wire 50, thus allowing guide wire 50 to be 
withdrawn from catheter 20 without dislodging catheter 20 within the vein 
or creating kinks therein. Upon removal of guide wire 50, device 54 is 
removed from luer lock connector fitting 30 of catheter 20. Tube 44 then 
collapses against the wall of the vein, as shown in FIG. 3D, until an 
infusion procedure is initiated. 
A second method of rigidifying the catheter for insertion avoids the need 
for a guide wire and instead uses a pressurized fluid to inflate tube 44 
for purposes of insertion. This second method requires that the leading 
end 22 of catheter 20 is initially sealed, as shown in FIGS. 6 and 7, 
rather than being open as described with respect to FIG. 1. As shown in 
FIGS. 6 and 7, leading end 22 of tube 44 is initially sealed, but the seal 
formed at the second end of tube 44 preferably includes a weakened break 
line 74 which is adapted to be broken for providing an exit port. As 
described in greater detail below, this seal is later broken either 
locally or remotely after the catheter is properly placed. 
Prior to placement of catheter 20 using the pressurized fluid method, an 
introducer sheath is inserted into the vein, in the manner shown in FIG. 
8A. The introducer sheath includes a stiffening dilator 76 and a 
pull-apart sheath 78. The introducer sheath assembly is itself guided into 
vein 46 over a guide wire (not shown). As indicated in FIG. 8B, the rigid 
dilator 76 is then removed, leaving the pull-apart sheath extending 
through the skin 47 and into vein 46, thereby providing an entry 
passageway into a vein into which tube 44 is to be placed. 
The next step is to pressurize tube 44 with fluid to rigidify tube 44 and 
make it more oval. As indicated in FIG. 8C, an angiographic syringe 80 
filled with contrast dye is releasably secured to luer lock fitting 30 of 
catheter 20, and the plunger of syringe 80 is depressed sufficiently to 
inflate tube 44 with contrast dye fluid. The materials suggested above for 
use in forming tube 44 are easily capable of withstanding a pressure of 5 
Atmospheres without bursting, and such pressure is adequate to temporarily 
rigidify tube 44 for placement within the vein. While not illustrated, 
syringes which include pressure gauges are available and well known to 
those physicians practicing in the art. As indicated in FIGS. 8E and 8F, 
tube 44 of catheter 20 is then inserted into sheath 78 and advanced 
therethrough into vein 46 until sealed end 22 is positioned at a desired 
location within the vein, while maintaining pressure on the fluid within 
the tube. The presence of the contrast dye within tube 44, and the 
radiopaque markings on the tube, allows the catheter to be visible in 
X-rays or on a fluoroscope. 
After properly positioning catheter 20, pull-apart sheath 78 is withdrawn 
from the entry path while leaving tube 44 within the vein. FIG. 8F shows 
catheter 20 within vein 46 following removal of sheath 78 but before 
pressure has been released from tube 44. The final step is to break the 
seal at the seal at the leading end 22 of tube 44 for allowing infusion 
fluid within the tube to exit into the vein. Two preferred methods of 
breaking the seal will now be described. 
In the first seal breaking method, syringe 80 is removed from luer lock 
connector 30 of catheter 20, and a seal-breaking apparatus is inserted 
into tube 44 along the length of the tube to a point proximate leading end 
22 of the tube for opening the seal therein. For example, as shown in FIG. 
8D, the so-called seal-breaking apparatus consists of a guide wire 82 
inserted into tube 44 along the length of the tube to a point proximate 
leading end 22; the leading tip portion of guide wire 82 is advanced into 
the sealed end of tube 44 for piercing the sealed end of the tube to 
create the exit port. 
The second method for breaking the seal at the leading end of tube 44, 
after the tube is properly positioned within the vein, involves raising 
the fluid pressure within tube 44 beyond the burst strength of the 
weakened break line at the second end of the tube. As mentioned above, 
syringe 80 (see FIG. 8C) normally applies no more than 5 Atmospheres of 
pressure to the contrast fluid dye in tube 44 during insertion of catheter 
20 to avoid premature rupture of the seal. However syringe 80 is capable 
of applying at least 10 Atmospheres of pressure to the contrast dye fluid 
injected into tube 44. This higher pressure is adequate to rupture the 
seal along the weakened break line 74 at leading end 22 of tube 44 for 
providing the exit port. Confirmation of the successful rupture of the 
seal using this method can be confirmed using a fluoroscope by observing a 
puff of contrast dye emitted from the tip of the catheter. 
While the embodiments of the invention described thus far provide a 
catheter having only a single lumen, a fully collapsible multi-lumen 
catheter may also be constructed in accordance with the teachings of the 
present invention. Referring to FIG. 11, a third elongated, generally 
flattened strip 84 of the same flexible material as strips 32 and 38 can 
be secured along its side edges with the respective side edges of first 
strip 32 to form a second elongated, normally-flattened tube in parallel 
with tube 44; the collapsed lumen of such second tube is designated in 
FIG. 11 by reference numeral 86. The original lumen of the first 
normally-flattened tube is pre-loaded upon guide wire 50, as shown in FIG. 
11, prior to insertion into the vein. The third strip 84 may, if desired, 
be made of the same length as strips 32 and 38 to provide a second lumen 
86 having an exit port at its leading end disposed at approximately the 
same point in the vein as the exit port of the first lumen. Alternatively, 
third strip 84 may be made shorter in length than strips 32 and 38 to 
create a shorter second lumen 86 having an exit port that is 
longitudinally displaced from the exit port of the first lumen. Each of 
the two tubes may be provided with its own catheter hub (not shown) at the 
trailing end of such tubes in order to allow for separate control over the 
fluids infused therethrough. 
Likewise, in FIG. 12, a fourth elongated, generally flattened strip 88 of 
the same flexible material as strips 32, 38, and 84 can be secured along 
its side edges with the respective side edges of second strip 38 to form a 
third elongated, normally-flattened tube in parallel with tube 44; the 
collapsed lumen of such third tube is designated in FIG. 12 by reference 
numeral 90. The above-described insertion methods for catheter 20 apply 
equally well to the double and triple lumen catheters shown in FIGS. 11 
and 12 respectively. 
Those skilled in the art will now appreciate that an improved, fully 
collapsible venous infusion catheter has been described which presents 
minimal obstruction to blood flow within a vein, which presents minimal 
surface area in contact with blood flowing in the vein, and which prevents 
blood from entering the infusion lumen between infusion cycles, yet which 
expands to provide a relatively large infusion path during infusion 
procedures. While the present invention has been described with respect to 
several preferred embodiments thereof, such description is for 
illustrative purposes only, and is not to be construed as limiting the 
scope of the invention. Various modifications and changes may be made to 
the described embodiments by those skilled in the art without departing 
from the true spirit and scope of the invention as defined by the appended 
claims