Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to an improved construction of
the site on a tube external of the patient to enable leak-free
~ithdrawal of fluid samples from, or the injec~ion of medicants
into, a fluid flowing in the tube. The invention is parti-
cularly useful in blood tube sets used for the passage of blood
between the patient and an artificial kidney or a blood oxy-
genator.
Commercial blood-passage tubing sets have typically
provided one or more injection sites at which blood samples
may be taken from, or chemicals injected into, the blood by
hypodermic needle piercing the tube wall. Smooth, nontoxic
tubing must be used for the blood passage for patient safety;
such tubing has relatively thin walls, little elasticity and
is typically non-sealing after being pierced. In order to
prevent leakage into or from blood tubing pierced with a hypo-
dermic needle, eIastomeric materials having some ability to
self-seal have been used in the past. The elastomeric material
is so arranged with the blood tube that the needle puncture
is made through the self-sealing elastomeric material before
piercing the tube. However, the self-sealing characteristics
of the best commercially available material, natural rubber
latex, are insufficient at times to prevent leakage into the
blood tube under some of the conditions of use which are
periodically encountered. For example, the difficulty of
self-sealing increases as the needle size increases, as the
time of needle penetration increases, and as the number of
repeat injections is made at a particular injection site.
Moreover, the best self-sealer, natural rubber latex, is
known to have toxicity and blood clotting characteristics
3a that are less desirable than other elastomeric materials such
as silicone rubber, polyurethane elastomers, etc.
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To overcome the leaka~e problem while concurrently
avoiding toxicity or blood clot formation many injection site
constructions have heretofore been proposed. Commercial tube
sets have used a latex sleeve surrounding a section of the
blood tubing and such site constructions rely on the inherent
self-sealin~ of the latex sleeve to prevent leakage. To
furthex insure against leakage, a similar construction sur-
rounds the latex sleeve with a second thin, latex sleeve
stretched over the first sleeve and extending beyond the ends
1~ of the first sleeve to also seal against the blood tube. This
latter construction is shown in U. S. Patent 3,81~,137. While
this construction has experienced some commercial acceptance,
it is nevertheless subject to leakage under severe use con-
ditions. It is further objectionable because of the hazard
of piercing the holding hand of the person as the elastomeric
sleeves and the tube are pierced.
A blood access site construction which purports to
eliminate hazard to the needle administrator and leakage is
shown in U. S. Patent 3,898,988. This construction employs
2Q a plastic tube section which is placed in the blood flow
conduît. This plastic tube is a T-shaped hard plastic body
having a bore extending for the length of the vertically dis-
posed body portion and a diameter sufficient to receive the
ends of blood tubes which are adhesively secured in the bore.
In the longitudînal central area of the tube the bore diameter
equals the inner diameter of the blood tubes and the blood
flows through the bore in the hard plastic tube in this area.
Injection is made through a cylindrical opening in the top
surface of the T-shaped tube, which opening extends down into
the bore in the tube body through which the blood is flowing;
the opening is filled with a cylindrical insert of a non-
thrombogenic elastomer ~uch as a polyurethane or silicone
rubber which is compressed into place in the opening. This
construction has the serious defects that the lower end of
the elastomer is in contact with the blood flowing through the
tube and the entire cylindrical elastomer insert is subject
to dislodgement as the hypodermic needle is withdrawn; dis-
lodgement of the entire elastomeric inser-~ creates a channel
for leakage having the same diameter as the blood tube dia-
meter which is obviously unacceptable.
1~ The above discussed constructions represent the closest
prior art known to applicant which also includes the references
cited during their prosecution which include U.S. Patents
2,129,983; 2,498,831; 2,832,338; 3,030,955; 3,112,748;
3,447,570; 3,463,691; 3,853,127; 2,053,112; 2,907,351; and
3,566,868. None of the constructions known to applicant
completely solve the problems of leakage into, or from, a ~
non-thrombogenic blood tu~e while simultaneously eliminating ~ -
the hazard of accidental piercing of the hand of the needle
administrator. `
The present invention solves both of these problems.
According to the present invention the improved infusion tube
access site comprises an infusion tube, an elongated elasto- ~;
meric sleeve surrounding a portion of said infusion tube,
and a needle-impenetrable C-shaped member surrounding said
sleeve and extending substantially the full length and par-
tially around the periphery thereof to thereby expose a
portion of said sleeve between the inner extremities of the
arms of said C-shaped member, said C-shaped member having an
inner diameter smaller than the outer diameter of said sleeve
and compressing said sleeve around said tube along the length
thereof, the arm portions of said C-shaped member exerting a
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combination of radial and transversely directed forces within
the portion of said eIastomeric sleeve not covered by said
C-shaped member sufficient to prevent leaks into said tube
during the time a needle pierces said sleeve and said tube,
and after ~rithdrawal of said needle therefrom.
This invention prov i;desan inexpensive infusion tube
access site comprising a smooth nontoxic tube having an
elongated elastomeric sleeve surrounding a section of the tube
that is improved and distinguishes from prior constructions
by a C-shaped needle-impenetrable member substantially co-
extensive in length with the sleeve and enveloping more
than one-half of the periphery of the elastomeric sleeve,
which C-shaped member exerts a squeezé force on the sleeve
which acts through the elastomeric properties of the sleeve
to effectively seal against air leakage into, or blood leak-
age from, the blood tube during needle insertion or after the
needle is ~ithdrawn. The site construction of this invention
protects against inadvertent injury to the hand holding the
needle-impenetrable C-shaped member during needle insertion,
and provides a large access area for making plural insertions
while facilitating every angle of needle placement for in-
jecting medications and collecting blood samples. The site
construction of this invention also provides improved resist-
ance to leaks under much more severe conditions of use than
those normally encountered in the ordinary use of blood sets
for blood passing between a patient and an artificial kidney
or a blood oxygenator; it is also useful in transfusing blood
or other fluids, such as saline solutions, etc.
Fig. 1 is a top view of a preferred embodiment of the
invention~
Fig. 2 is a view taken on the line 2-2 of Fig. 1.
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Fig. 3 is a view taken on the line 3-3 of Fig. 2.
Fig. 4 is a perspective view, partly broken away,
showing the preferred embodiment during needle insertion.
Fig. 5 is a vie~ of the embodiment of Fig. 4, in
section, showing one needle piercing the elastomeric sleeve
and blood tube wall and two additional piercing locations of
a needle in dotted lines.
Fig. 6 is a view illustrating a site of this invention
~hich shows t~o ~it~drawn needle locations and a third needle
partially withdrawn.
Fig. 7 is an enlarged end view of the embodiment of
Fig. 1.
Fig. 8 is an enlargement of the needle penetrating por-
tion of Fig. 7 showing the force distribution within the elas-
tomeric sleeve as a needle is withdrawn.
Fig. 9 is an enlargement of the portion of Fig. 6
surrounded by the line 9-9 showing the force distribution
within the elastomeric sleeYe on a needle inserted at an
angle less than 90 to the axis of the blood tube.
Referring to the drawings, the improved access site
construction of this invention is shown in Fig. 1 and ~en-
- erally designated 10. Site 10 consists of blood or infusion
tube 12 which in normal use is a part of the blood tubing in
a tube set which connects patient's artery or vein to an
artificial kidney or blood oxygenator, or an organ per-
fusion device. Tube 12 may be made of any of a number of
commercially available nontoxic plastics, for example, poly-
vinyl plastisols, polyurethane or silicone rubber and pref-
erably is made of plasticized pol~vinyl chlorlde. -
An elastomeric sleeve 14 surrounds a section of tube
12 at one or more locations along its length, for example,
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in sections abQut 1 to 2 1/2 inches long. The elastomeric
properties of sleeve 14 are important to the accomplishment
of the objective of elimination of leaks of the types above
mentioned. The elastomer should be relatively soft and yet
have sufficient elasticity and internal strength to permit
needle insertion without shredding or disintegrating as the
needle is înserted or withdrawn; it should exhibit maximized
memory or ability to resume its original position after being
stretched or deformed and maximum resistance to fatigue or
lQ change of resilience with reuse or passage of time. Import-
antly, the elastomer should be capable of transmitting forces,
particularly compxessive forces, from the point of application
to adjacent areas within the body of the elastomer. These
general considerations can be employed in selecting the best
elastomer for particular use conditions which may vary sub-
stantially as to pressure of fluid flowing in tube 12, or the
diameter of the needle used, or the time of retention of the
needle during the blood sampling or during the addition of
medicants to the blood tube from those conditions which are
normally encountered in the use of access sites on blood sets
employed in dialyzing a patient with an artificial kidney.
There are a number of types of elastomeric materials which
are available from which sleeve 14 may be fabricated that will
possess the appropriate degree of resiliency for a specific
set of use conditions, for example, polyurethane elastomers,
silicone elastomers, synthetic latex and natural rubber latex.
For use in dialysis of humans employing an artificial kidney,
particularly the type of artificial kidney containing hollow
fibers as the dialyzing element such as the C-DAK artificial
3~ kidney available from Cordis Dow Corp., the preferred elastomer
is natural rubber latex.
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The third, and key, element in the preferred access
site construction of this invention is a C-shaped needle-
;mpenetrable element 16, which surrounds a portion of the
periphery of sleeve 14, greater than one-half of that periph-
ery, and preferably about 65~ to about 90% of it. Element 16
has as its first function the prevention of inadvertent pene-
tration by needle 18 completely through sleeve 14 and tube 12
and piercing the hand holding the access site as best illus-
trated in phantom in FIg. 4. The second and more important
function of C-shaped member 16 is to apply an amount of com-
pressive force to the portion of sleeve 14 which it surrounds
sufficient to enhance the inherent resiliency characteristics
of that sleeve in the portion thereof which is not coverea
by member 16 to cause sleeve 14 to prevent air leaks into
the tube 12 during the time that needle 18 is in penetrated
position extending through the upper wall portions of sleeve
14 and tube 12 as may be seen in Fig. 5. Another somewhat
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less important function of member 16 is to continuously apply
such an amount of force to and through the body of member 16
2Q to cause substantially immediate blockage of fluid leaks out-
ward through the opening in tube 12 as needle 18 is drawn
through the interface between the outer surface of the wall of
tube 12 and the inner surface of sleeve 14, as is illustrated
in Fig. 6. Momentarily later, as needle 18 is withdrawn
through the body, or upper wall, portion of sleeve 14, the
force applied to sleeve 14 by member 16 functions to cause
leak-tight closure of the opening earlier generated by the
penetration of needle 18, as shown by lines 20, 22 in Fig. 6.
This latter force is applied majorly by the portions 16A,
3Q 16B of member 16, that is, the upper arm extremities which
lie above a horizontal plane tangent to the upper surface
of the tu~e 12 as shown by dotted line 17 in Fig. 7.
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The ~orce applied hy member 16 to sleeve 14 results
from the strength of the material comprising member 16 to
resist deformation from an original circular cross-section
to the C-shaped cross-section it possesses when positioned
around the portion of the periphery of sleeve 14 which it
covers as sho~n in Figs. 3 and 7. Fig. 7 is an expanded end
view of the preferred access site 10 which is drawn to scale
and shows the degree to which member 16 is distorted from its
original circular cross-section when the material of tube 12
la is plasticized polyvinyl chloride, elastomeric sleeve 14 is
natural rub~er latex and member 16 is polypropylene. Before
assembly, tube 12 had an outside diameter of 0.253" + 0.003";
latex sleeve 14 had an inner diameter of 0.219" + 0.016", a
wall thickness of 0.125" + 0.010l' and a nominal outside
diameter of Q.469". Sleeve 14 is mounted over tube 12 and
its inner diameter is slightly stretched as it moves into
position over the section of tube 12 preselected as the
location for access site 10 and sleeve 14 concurrently applles
a smaLl compressive force on the outer diameter of tube 12.
Similarly, prior to assembly, member 16 was an injection
molded polypropylene member, circular in cross-section,
having an inner diameter of 0.400" and a wall thickness of
0.0;52"-0.060" and an opening between the upper wall portions
16A and 16B of 0.125" as shown in Figs. 3 and 7. Member 16
is mounted on sleeve 14 by forcing the portions 16A and 16B
apart sufficiently to enable encirclement of the outside
diameter of sleeve 14; the resistance of the polypropylene
material to the spreading deformation sufficient to tightly
overlie the illustrated portion of the periphery of sleeve
3a 14 results in a bulging of the portion indicated by arrow
23 of sleeve 14 which lies between the inner surfaces 24A
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and 24B. Due to the final position spreading of arm portions
16A and 16B during assembly the portion indicated by arrow
25 of the wall of member 16 is slightly flattened from its
circular cross-section producing a slightly elongated C-section
which may be seen by rotating Fig. 7 until portion 16B is at
the top of the figure.
As a result of the distortion of member 16 from its
initial circular cross-section a combination of multi-direc-
tional forces are constantly applied to sleeve 1~ by member
16. These forces are illustrated by the arrows 26 in Fig. 8
and are related to a needle 18 which is piercing sleeve 14
perpendicularly to the longitudinal axis of tube 12. It may
be seen that the forces applied, primarily by the upper wall
portions 16A and 16B, comprise forces consistin~ of components
directed radially inwardly toward sleeve 12 and other forces
which result from the squeezing pressure of surfaces 24A, and
24B on the outer surface of sleeve 14 to cause the bulging at
23 which ha~e components which vary from the radial direction
gradually upwardly to the horizontal and beyond toward the
2a axially central area of the bulge 23.
Fig. 9 specifically illustrates the distribution of
forces which are additionally available to cause closure, and
leak-tight sealing, of a needle inserted through sleeve 14 at ~ ,
an angle less than 90, and about 40 as shown, from a hori-
zontal plane passing through the axis of tube 12, as indicated
at 28, Fig. 6. Arrows 30 show the vertically oriented forces
which bear on the upper and lower surface portions of the
opening cause by needle 18 due to the angular insertion of
the needle. The best sealing results are obtained with the
access site construction of this invention when the needle
penetration is made at an angle of approximately 45 + 10
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from a horizontal plane passing through the axis of tube 12.
The access site shown in Fig. 7 and constructed from -the
materials above identified represents the best form of the
invention that is currently known. It is satisfactory, how-
ever, to fabricate member 16 from materials other than poly-
propylene. The important requirement which must be satisfied
is that the substitute material possessa relatively high rigid-
ity and resistance to deformation from an initial circular
cross-section to a C-shaped cross-section similar to that
above described for polypropylene member 16. It is desirable
to select a substitute having sufficient resistance to deform-
ation in a relatively thin wall section, for example, less
than 0.100", to exert sufficient force to insuxe against
leaks under severe use conditions. Satisfactory substitutes
for polypropylene include other plastics such as synthetic
polyamides available under the designation "Nylon", acetal
resins available under the designation "Delrin", and ABS
resins available from many suppliers; metals such as steel,
stainless steel, aluminum and magnesium may be used and are
recommended for use under the most severe of use conditions.
Metal offers the advantage of ease of fabrication into
initial cross-sectional forms other than circular to enable
increased pressure from the upper wall portions corresponding
to 16A and 16B. For example, portions 16A and 16B may be
initially bent inwardly from the circular so as to exert
additional downward forces to those illustrated as arrows
26 in Fig. 8.
The improvement in preventing air leaks using the
preferred embodiment of this invention which has been speci-
fically described above as to materials, initial and
assem~led sizes in the description of Fig. 7 is illustrated
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by the comparative test data se~ forth below. The preferred
access site of this invention was tested in comparison with
the access site construction of U.S. patent 3,814,137 which
is commercially available from Travenol Laboratories, Inc.
under the designation Travenol Dialysis slood Set. Each of
these constructions is especially sultable for use in blood
sets employed in artificial kidney dialysis, and thus the
test conditions selected for the comparison are conditions
which are much more severe than the conditions encountered --
in normal clinical use on actual dialysis patients. The
test conditions used are shown in Table I to provide a
comparison with normal conditions encountered in clinical
usage during dialysis employing a hollow fiber C-DAK artifi-
cial kîdney.
Table I
Selected Test Clinical Dialysis-
Condition Normal Range
Needle 18 gauge (0.05" diameter) 20-27 gauge (0.036-
0.016" diameter)
Angle of piercing 90 45
Pressure, sub-
atmospheric -150 to -400 mm Hg 0 to -80 mm Hg
Pressure, positive 5, lO, 15 psig 0.4 - 3.0 psig
Fluid Flow Rate 200 ml/minute 100 - 300 ml/minute
Temperature 37C + 1C 35 - 39 C -
Fluid Water Blood ~
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It will be apparent that the conditions of larger
needle size, angle of piercing, pressures both negative and
positive and the use of ~ater rather than blood are each sub-
stantially more severe than use conditions normally encoun-
tered.
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The test procedure used was as follows:
l. Connect blood lines to negative pressure system and warm
to body temperature, 37C.
2. At water flow rate of 20Q ml/min. set pressure to -150 mm
Hg, which is approximately twice the maximum negative
pressure usually encountered in dialysis.
3. Using 18 gauge, Q.Q50" diameter, needle pierce through
the latex sleeve and the tube at a 90 angle to a hori-
zontal plane passing through the axis of the blood tubes
la and hold in place for l minute, withdraw and inspect for
leaks under bright light. If no leak, after 1 minute,
then repeat and reinspect.
4. If no leak is visible after second inspection, raise sub-
atmospheric pressure on water to -400 mm Hg. Repeat Step
3 for 2 piercings with l minute held before inspection.
5. If no leak after the four piercings of Steps 3 and 4,
set pressure on water to positive 5 psig and repeat Step
3.
6. If no leak after the sixth piercing in Step 5, change
pressure to positive lO psig and repeat Step 3.
7. If no leak after the eighth piercing of Step 6, change
pressure to positive 15 psig and repeat Step 3. At any
time a leak appeared in the form of a visible bubble or
bubbles in the water in the Steps 3 or 4 or a leak around
the needle or at the needle opening after withdrawal and
after 1 minute of inspection time, the test was stopped
and the number of piercings made before the leak occurred
was recorded and the test discontinued.
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Twenty access site constructions of the type shown in
Fig. 2 of U.5. Patent 3,814,137, available in the United States
under the designation Travenol Dialysis Blood Set were ob-
tained and tested under the selected test conditions by using
the above stated test procedure in comparison to the preferred
access site constructions of this invention~ specifically
shown in Fig. 7 and described above as to dimensions. The
results are reported as the average number of needle punctures
before a leak occurred, follo~ing for each access site the
la sequence of puncturing under the increasingly severe test
conditions until failure occurred. The average number of
punctures before a leak occurred for the access site con-
structions of U.S. Patent 3,814,137 for the 20 sites tested
was 5.25. The average number of punctures before a leak
occurred for the preferred access site constructions of this
invention for the 72 sites tested was 7.66.
To illustrate the necessity for sufficient forces to
be generated by the needle-impenetrable sleeve within the
body of the latex sleeve to prevent leaks, and for contrast
w-ith the results obtained from the use of the preferred ;
embodiment of this invention as above shown, a further series
of tests was conducted. In this series, each of the tube,
the latex sleeve and the needle-impenetrable member was made
of the same material as was used in the test of the preferred
embodiment. The only change was the size of the latex sleeve,
and it was decreased to an outside diameter of 0.438" and its
inner diameter was 0.187". This change decreased the
difference in diameter between the latex sleeve outside dia-
meter and the impenetrable member inside diameter and con-
3Q currently increased the difference in outside diameter of the
tube and the inside diameter of the latex sleeve. Seventy-
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two access sites of this construction, tested under identical
conditions and by the same procedure resulted in an average
number of punctures to leak of 2.53.
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