Catheter introducing device and method of placing catheter

A catheter placement cannula is disclosed having a passageway therethrough to receive a catheter. The cannula is made up of a substantially tubular body portion and a tip portion made of pliable material. The tip portion has a shape retaining memory such that the end of the tip is naturally flattened in shape to provide a seal for preventing the backflow of blood or other fluids when the cannula is in place in a body.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to catheters in general and particularly to 
cannulas for introducing catheters into a body. 
2. Description of the Prior Art 
Catheters have a variety of uses especially in the medical field. The term 
"catheter" is commonly used to identify a tubular instrument that is 
inserted into various body cavities, either naturally or surgically 
opened. They can be used for administering fluids into the body, 
performing blood transfusions, removal of body fluids or components of 
body fluids, blood pressure determinations, etc. 
Conventionally, a catheter is placed into the, body-by any of a number of 
well known methods. The simplest method is to make a surgical incision in 
the body and insert the tip of the catheter directly through the incision 
into the body. Alternatively, a needle is inserted into the body and the 
catheter is passed through the needle and into the body. The needle is 
then usually withdrawn leaving the catheter inserted. These methods 
inevitably involve the loss of blood through the incision. Further, the 
damage to the skin, blood vessel wall and other body parts makes it 
difficult to employ the same area when multiple studies are contemplated. 
Semi-permanent cannulas are also known. The term "cannula", as it is used 
here, means a generally tubular device, through which a catheter is 
placed, which is designed to assist the placement of the catheter in the 
body. For example, U.S. Pat. No. 4,000,739 to Stevens is directed to a 
cannula which is adapted to be left in place in the body whether or not a 
catheter is present. A gasket-like seal having a Y-shaped slit is placed 
in the cannula in order to prevent any backflow of blood when a catheter 
is removed. U.S. Pat. No. 4,239,042 to Asai is directed to a catheter 
placement system which involves a cannula having a body portion and a tip 
portion. The cannula is useful in avoiding thrombogenic irritations and in 
avoiding collapse of the catheter during use. However, these patents 
suffer the disadvantage of being of a relatively large size. Additionally, 
they are quite bulky to use, often requiring more than one pair of hands 
for insertion and use. 
SUMMARY OF THE INVENTION 
It is the purpose of the present invention to provide a catheter placement 
device or cannula which avoids the above-noted problems. The device of the 
present invention is contemplated by a cannula for placing a catheter in a 
body comprising a body portion made of material of sufficient rigidity to 
receive the catheter and a tip portion made of a pliable material of 
sufficient rigidity to also receive the catheter. The tip portion is 
connected to the body portion and has a shape retaining memory such that 
the tip is naturally flattened in a sealed condition when not in use. This 
has the direct advantage of preventing any backflow of blood or other 
fluids from the body when a catheter is removed leaving only the cannula 
in place. Additionally, once the cannula of the present invention is 
inserted into the body, it can remain in the body for multiple uses or 
studies. By this, it is meant that the cannula of the present invention 
may be used for successive catheter insertions. This has the advantage of 
requiring only one puncture into the body for multiple studies. Due to the 
relatively small size of the cannula it may be placed in virtually any 
part of the body. The term "body" as used herein is specifically directed 
to a human body but it is to be understood that 15 the device of the 
present invention is useful in other types of bodies, such as animals 
other than humans. 
Further, the use of the cannula of the present invention aids in avoiding 
the collapse of the catheter during placement and use. 
The cannula of the present invention can advantageously be left in the body 
whether a catheter is or is not present. When the catheter is in place, 
there is no blood loss due to the sealing engagement between the 
interested catheter and the cannula walls. When the catheter is removed, 
the tip of the cannula automatically closes obviating the necessity of 
either removing the cannula or of occluding the cannula.

DETAILED DESCRIPTION OF THE INVENTION 
FIGS. 1 and 2 show the cannula 10 according to the present invention. 
Cannula 10 is made of a material having sufficient rigidity to be inserted 
into a body part such as, for example, a blood vessel, through an opening 
made by a needle tip. Cannula 10 must have enough rigidity to withstand 
the pressure from the patient's skin and the systemic pressure against it 
after the cannula insertion device is withdrawn. All or part of cannula 10 
may be composed of any standard flexible, nontoxic materials, such as for 
example natural rubber or latex, polypropylene, fluororesin, polyethylene, 
polyvinylchloride or silicone. The surface of cannula 10 may also be 
coated with a low-friction material in order to eliminate the tendency to 
grab the skin tissues and to prevent a build up of infection-causing 
organisms. Materials such as Teflon.RTM. and silicone act to create a 
low-friction surface. 
If desired, part of cannula 10 may be made of metals such as stainless 
steel as will be described further on in this description. Cannula 10 
comprises a body portion 12 and a tip portion 14. Body portion 12 and tip 
portion 14 are a generally one piece construction of extruded flexible 
material as described above. However, it is contemplated in this invention 
to have separate body portions 12 and tip portions 14. In this manner, 
body portion 12 may be made of a material which is different from tip 
portion 14. For example, body portion 12 may be made of hard plastics or 
metals in a generally tubular fashion. Tip portion 14, on the other hand, 
must be made of a generally pliable material. As illustrated in the 
figures, the proximal portion 18 of the body 12 is flared to accommodate 
the catheter 22. In this manner, a catheter having a diameter only 
slightly smaller than the cannula, as illustrated in FIG. 2, may be easily 
inserted into the cannula. 
Cannula 10 has a passage 16 therethrough adapted to receive a catheter. As 
illustrated in FIG. 3, passage 16 extends from the proximal portion 18 of 
the cannula 10 to the distal end 20 of the tip 14. However, due to the 
memory-activated closure of the tip 14, passage 16 is normally sealed off 
when a catheter 22 or other object is not in place in the cannula 10. 
The tip 14 acts as a backflow prevention valve. Like body portion 12, it 
contains passage 16. However, the tip 14 is provided with a "memory" of a 
naturally closed seal as illustrated in FIGS. 1, 3 and 5. This seal is 
capable of withstanding minimum blood pressure or other fluid pressure 
when a catheter is removed. The normally closed tip is adapted when closed 
to prevent any fluid from flowing through passage 16 of the cannula 10. 
This obviates the necessity of occluding the cannula and also prevents 
significant blood or fluid loss at all times. 
When desired, the valve may be shifted from the normally closed position to 
an open position, as illustrated in FIGS. 2 and 6. The tip is generally 
formed of a cylindrical hollow base portion at 24 with a pair of tapered 
opposing flaps 26 and 28 which are engaged in a sealing relationship at 
the distal end 20 when the tip portion is in a normal relaxed position. 
When a catheter 22 or other object is inserted into the cannula 10, as 
illustrated in FIG. 2, the resilient walls of the tip 14 adjust to allow 
the passage of the catheter 22. The walls of the tip 14 are so provided to 
be in sealing engagement with the catheter 22 in order to prevent any back 
flow of body fluid through the passage 16 when the catheter 22 is in 
place. 
One method of inserting the cannula of the present invention into a body 
will be described below, with specific reference to FIG. 4. FIG. 4 shows a 
cross-sectional view of the skin 30 and a blood vessel 32 of a patient. In 
operation, an incision is made in the patients skin 30 close to the blood 
vessel 32 to be used. Cannula 10, which is fitted with a needle 34 of the 
cannula insertion device 36 is then introduced into the blood vessel 32. 
When the tip 38 of the needle 34 reaches the blood vessel, blood spurts 
through the hollow portion of the needle and appears in the syringe 40, 
which confirms that the cannula and needle have penetrated into the vein. 
The cannula insertion device 36 consisting of the syringe 40 and the 
needle 34 is then withdrawn, leaving the cannula 10 in the body as 
illustrated in FIG. 5. 
It is to be understood that the body portion 12 of the cannula 10 may be of 
any length as desired. Generally, the body portion 12 is affixed to the 
skin surface by any means known to the art, such as an adhesive strip. 
When the cannula is not in use, a plug 42 may be placed on the proximal 
end of the cannula 10 in order to prevent the 15 entrance of any bacteria 
or other infectious organisms into the passageway 16. 
When it is desired to place the catheter 22 through the cannula 10 into the 
blood vessel 32, the plug 42 is simply removed and the catheter 22 is 
passed through the passageway 16 of the cannula 10. The resiliency of the 
tip 14 will immediately cause the tip 14 to adjust to the entrance of the 
catheter 22 allowing its passage therethrough and into the blood vessel 32 
as illustrated in FIG. 6. 
If multiple studies are indicated, it is a simple matter to remove the 
catheter 22 and introduce another. The sealing nature of the naturally 
closing tip 14 will prevent any clotting. However, in order to further 
insure the prevention of clotting, an anticoagulant such as heparin may be 
flushed through the passage 16. 
By the cannula 10 of the present invention, multiple insertions of 
catheters may be made in one incision in the body. This removes the 
necessity of multiple incisions. 
Although the present invention has been described with preferred 
embodiments, it is to be understood that modifications and variations may 
be resorted to, without departing from the spirit and scope of this 
invention, as those skilled in the art will readily understand.