U.S. patent application number 14/610387 was filed with the patent office on 2015-05-21 for inflatable elastomeric pump for an infusion assembly.
The applicant listed for this patent is Avent, Inc.. Invention is credited to Deepak Gandhi, Kokeb Tefera, Quang Ngoc Vu.
Application Number | 20150141922 14/610387 |
Document ID | / |
Family ID | 48946214 |
Filed Date | 2015-05-21 |
United States Patent
Application |
20150141922 |
Kind Code |
A1 |
Tefera; Kokeb ; et
al. |
May 21, 2015 |
Inflatable Elastomeric Pump for an Infusion Assembly
Abstract
An improved elastomeric pump for an infusion assembly. The pump
includes a generally cylindrical mandrel body with first end, an
opposed second end, a length, an outer diameter corresponding to a
first radius (R.sub.mandrel), a central bore extending through the
length, a first port extending from the outer diameter to the bore
to provide a fluid passageway, a fill port and an exit port in
fluid communication with the bore. The pump includes an inflatable
elastomeric tube disposed concentrically about the mandrel, the
tube being sealingly secured on the mandrel near the respective
ends of the tube and having an original inner diameter that
corresponds to a second radius (r) so that it approximately matches
the outer diameter of the mandrel (R.sub.mandrel), a length (L)
less than the length of the mandrel, a wall thickness (t) such
that: (0.4225.times.r)<t.ltoreq.(0.660.times.r).
Inventors: |
Tefera; Kokeb; (Lake Forest,
CA) ; Vu; Quang Ngoc; (Aliso Viejo, CA) ;
Gandhi; Deepak; (Irvine, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Avent, Inc. |
Alpharetta |
GA |
US |
|
|
Family ID: |
48946214 |
Appl. No.: |
14/610387 |
Filed: |
January 30, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13755037 |
Jan 31, 2013 |
8968242 |
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14610387 |
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61637963 |
Apr 25, 2012 |
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61616589 |
Mar 28, 2012 |
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61597502 |
Feb 10, 2012 |
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Current U.S.
Class: |
604/153 |
Current CPC
Class: |
A61M 5/152 20130101;
A61M 5/145 20130101; A61M 2205/0216 20130101 |
Class at
Publication: |
604/153 |
International
Class: |
A61M 5/152 20060101
A61M005/152; A61M 5/145 20060101 A61M005/145 |
Claims
1. An elastomeric pump for an infusion assembly, the pump
comprising: a mandrel comprising a body having a first end and an
opposed second end, a length, a central bore extending through the
length, a first port positioned between the first end and second
end and in fluid communication with the bore to provide a fluid
passageway, a fill port in fluid communication with the bore, and
an exit port in fluid communication with the bore; and an
inflatable elastomeric tube disposed concentrically about the
mandrel, the tube positioned between the first end and second end
of the mandrel and covering the first port, the tube being
sealingly secured on the mandrel near the respective ends of the
tube and having an original inner diameter that corresponds to a
radius (r), a length (L) less than the length of the mandrel, and a
wall thickness (t) such that:
(0.4225.times.r)<t.ltoreq.(0.660.times.r).
2. The pump of claim 1, wherein the mandrel comprises a radius
(R.sub.mandrel) and a generally uniform outer diameter that matches
the original inner diameter of the inflatable tube.
3. The pump of claim 1, wherein the inflatable tube further
comprises a volume (v.sub.tube) of an elastomeric material:
v.sub.tube=.pi.L(2rt+t.sup.2).
4. The pump of claim 1, wherein the introduction of a volume of
liquid (v.sub.liquid) determined according to the following
equation:
(12.50.times.v.sub.tube).ltoreq.v.sub.liquid.ltoreq.(22.16.times.v.sub.tu-
be) through the fill port at a fill pressure of greater than 0 and
less than 35 psig expands the inflatable elastomeric tube between
the mandrel and the elastomeric tube such that the pump
subsequently dispenses the volume of liquid through the first port
upon contraction of the tube to its original inner diameter.
5. The pump of claim 1, wherein the elastomeric material is an
elastomeric silicone.
6. The pump of claim 5, wherein the elastomeric silicone has a
Shore Hardness of from 25 A to 40 A.
7. The pump of claim 1, wherein the inflatable tube is made from an
elastomeric silicone such that the inflatable tube has a Shore
Hardness of 37 A.
8. An elastomeric pump for an infusion assembly, the pump
comprising: a mandrel comprising a body having a first end and an
opposed second end, a length, a central bore extending through the
length, a first port positioned between the first end and second
end and in fluid communication with the bore to provide a fluid
passageway, a fill port in fluid communication with the bore, and
an exit port in fluid communication with the bore; and an
inflatable elastomeric tube disposed concentrically about the
mandrel, the tube positioned between the first end and second end
of the mandrel and covering the first port, the tube being
sealingly secured on the mandrel near the respective ends of the
tube and having an original inner diameter that corresponds to a
radius (r), a length (L) less than the length of the mandrel, and a
wall thickness (t) such that:
(0.4225.times.r)<t.ltoreq.(0.660.times.r) the inflatable tube
further comprising a volume (v.sub.tube) of an elastomeric
material: v.sub.tube=.pi.L(2rt+t.sup.2) such that introduction of a
volume of liquid (v.sub.liquid) determined according to the
following equation:
(12.50.times.v.sub.tube).ltoreq.v.sub.liquid.ltoreq.(22.16.times.v.sub.tu-
be) through the fill port at a fill pressure of greater than 0 and
less than 35 psig expands the inflatable elastomeric tube between
the mandrel and the elastomeric tube such that the pump
subsequently dispenses the volume of liquid through the first port
upon contraction of the tube to its original inner diameter.
9. The pump of claim 8, wherein the mandrel comprises a radius
(R.sub.mandrel) and a generally uniform outer diameter that matches
the original inner diameter of the inflatable tube.
10. An elastomeric pump for an infusion assembly, the pump
comprising: a mandrel comprising a body having a first end and an
opposed second end, a length, a central bore extending through the
length, a first port positioned between the first end and second
end and in fluid communication with the bore to provide a fluid
passageway, a fill port in fluid communication with the bore, and
an exit port in fluid communication with the bore; and an
inflatable elastomeric tube disposed concentrically about the
mandrel, the tube positioned between the first end and second end
of the mandrel and covering the first port, the tube being
sealingly secured on the mandrel near the respective ends of the
tube and having an original inner diameter that corresponds to a
radius (r), a length (L) less than the length of the mandrel, and a
wall thickness (t) such that:
(0.4225.times.r)<t.ltoreq.(0.660.times.r) and wherein the pump,
upon inflation with a predetermined volume of liquid and during
delivery of that liquid, exhibits a linear pressure versus volume
curve from a deflation yield point that is above a predetermined
operating pressure to a volume the corresponds with the dispensing
of the volume of liquid through the first port upon contraction of
the tube to its original inner diameter.
11. The pump of claim 10, wherein the inflatable tube further
comprises a volume (v.sub.tube) of an elastomeric material:
v.sub.tube=.pi.L(2rt+t.sup.2).
12. The pump of claim 10, wherein the introduction of a volume of
liquid (v.sub.liquid) determined according to the following
equation:
(12.50.times.v.sub.tube).ltoreq.v.sub.liquid.ltoreq.(22.16.times.v.sub.tu-
be) through the fill port at a fill pressure of greater than 0 and
less than 35 psig expands the inflatable elastomeric tube between
the mandrel and the elastomeric tube.
13. The pump of claim 10, wherein the elastomeric material is an
elastomeric silicone.
14. The pump of claim 13, wherein the elastomeric silicone has a
Shore Hardness of from 25 A to 40 A.
15. The pump of claim 14, wherein the elastomeric silicone has a
Shore Hardness of from 35 A to 40 A.
16. The pump of claim 15, wherein the inflatable tube is made from
an elastomeric silicone such that the inflatable tube has a Shore
Hardness of 37 A.
17. An elastomeric pump for an infusion assembly, the pump
comprising: a mandrel comprising a body having a first end and an
opposed second end, a length, a central bore extending through the
length, a first port positioned between the first end and second
end and in fluid communication with the bore to provide a fluid
passageway, a fill port in fluid communication with the bore, an
exit port in fluid communication with the bore; an inflatable
elastomeric tube disposed concentrically about the mandrel, the
tube positioned between the first end and second end of the mandrel
and covering the first port, the tube being sealingly secured on
the mandrel near the respective ends of the tube and having an
original inner diameter with a radius (r), a length (L) less than
the length of the mandrel, a wall thickness (t) such that:
(0.4225.times.r)<t.ltoreq.(0.660.times.r) and; wherein the
elastomeric material is an elastomeric silicone with a Shore
Hardness of from 25 A to 40 A.
18. The pump of claim 17, wherein the inflatable tube further
comprises a volume (v.sub.tube) of an elastomeric material:
v.sub.tube=.pi.L(2rt+t.sup.2).
19. The pump of claim 17, wherein the introduction of a volume of
liquid (v.sub.liquid) is determined according to the following
equation:
(12.50.times.v.sub.tube).ltoreq.v.sub.liquid.ltoreq.(22.16.times.v.sub.tu-
be) through the fill port at a fill pressure of greater than 0 and
less than 35 psig expands the inflatable elastomeric tube between
the mandrel and the elastomeric tube such that the pump
subsequently dispenses the volume of liquid through the first port
upon contraction of the tube to its original inner diameter.
20. The pump of claim 17, wherein the elastomeric silicone such has
a Shore Hardness of 37 A.
21. The pump of claim 17, wherein the inflatable tube further
comprises a volume (v.sub.tube) of the elastomeric material:
v.sub.tube=.pi.L(2rt+t.sup.2) such that introduction of a volume of
liquid (v.sub.liquid) determined according to the following
equation:
(12.50.times.v.sub.tube).ltoreq.v.sub.liquid.ltoreq.(22.16.times.v.sub.tu-
be) through the fill port at a fill pressure of greater than 0 and
less than 35 psig expands the inflatable elastomeric tube between
the mandrel and the elastomeric tube such that the pump
subsequently dispenses the volume of liquid through the first port
upon contraction of the tube to its original inner diameter.
22. The pump of claim 17, wherein upon inflation with a
predetermined volume of liquid and during delivery of that liquid,
the pump exhibits a linear pressure versus volume curve from a
deflation yield point that is above a predetermined operating
pressure to a volume the corresponds with the dispensing of all the
volume of liquid through the first port upon contraction of the
tube to its original inner diameter.
23. The pump of claim 22, wherein the inflatable tube further
comprises a volume (v.sub.tube) of an elastomeric material:
v.sub.tube=.pi.L(2rt+t.sup.2) and wherein the introduction of the
volume of liquid (v.sub.liquid) determined according to the
following equation:
(12.50.times.v.sub.tube).ltoreq.v.sub.liquid.ltoreq.(22.16.times.v.sub.tu-
be) through the fill port at a fill pressure of greater than 0 and
less than 35 psig expands the inflatable elastomeric tube between
the mandrel and the elastomeric.
24. The pump of claim 17, wherein the mandrel comprises a radius
(R.sub.mandrel) and a generally uniform outer diameter that matches
the original inner diameter of the inflatable tube.
Description
[0001] The present application is a Continuation application of
U.S. patent application Ser. No. 13/755,037, filed Jan. 31, 2013,
which claims the benefit of priority from U.S. Provisional
Applications No. 61/637,963 filed on Apr. 25, 2012 and from No.
61/616,589 filed on Mar. 28, 2012 and from No. 61/597,502 filed
Feb. 10, 2012.
FIELD OF THE INVENTION
[0002] The present invention relates to liquid dispensing apparatus
and pertains particularly to an improved infusion apparatus or
assembly for delivering intravenous drugs at a controlled rate to a
patient.
BACKGROUND OF THE INVENTION
[0003] It is often necessary to intravenously supply patients with
pharmaceutically active liquids at a controlled rate over a long
period of time. It is desirable that this be accomplished while the
patient is in an ambulatory state. A few devices have been
developed in the past for accomplishing this purpose.
[0004] The prior art devices typically include an inflatable
elastomeric bladder forming a liquid container and have a flow
control valve or device and tubing for supply of the liquid to the
patient. The walls of the bladder are forced to expand when filled
with the liquid, and provide the pressure for expelling the liquid.
These prior art devices are typically filled by hand by means of a
syringe which often require an inordinate amount of force.
[0005] Another drawback to the prior art devices is that the
conventional inflatable elastomeric bladder provides pressures and
flow rates that can vary widely with the volume of liquid therein.
Therefore, they do not have a reasonably stable pressure and flow
rate over the infusion period. In addition, such conventional
bladders frequently have difficulty dispensing substantially all of
the liquid by the end of the infusion period. It is undesirable to
have liquid remaining in the bladder.
[0006] Various materials are used for constructing conventional
inflatable elastomeric bladders. For example, natural rubber is
frequently used. Some construction requires several layers of
material. The use of silicone in tube form to function as a
pressurized liquid reservoir for infusion purposes is described in,
for example, U.S. Pat. No. 4,909,790 which discloses an infusion
device that uses tubular bladders mounted on mandrel supports with
downstream restrictors to deliver uniform flow rates. Another
example may be found in U.S. Pat. No. 7,704,230 which describes a
pressurized fluid reservoir made from a silicone tube for an
infusion system. Such references point to numerous possible
combinations of silicones, structural dimensions, filling
pressures, operating pressures, and fill volumes. However, the
performance provided by the silicone tube disclosed in U.S. Pat.
No. 7,704,230 has been found to be unacceptable for use at least
because of the variability in flow rate and the pressure during the
infusion period and the difficulty dispensing substantially all of
the liquid by the end of the infusion period.
BRIEF SUMMARY OF THE INVENTION
[0007] The problems described above are addressed by the present
invention which encompasses an improved elastomeric pump for an
infusion assembly. The pump includes:
[0008] (a) a mandrel having a generally cylindrical body having a
first end and an opposed second end, a length, a generally uniform
outer diameter that corresponds to a first radius (R.sub.mandrel),
a central bore extending through the length, a first port
positioned between the first end and second end and extending from
the outer diameter to the bore to provide a fluid passageway, a
fill port at about the first end in fluid communication with the
bore, and exit port at about the second end in fluid communication
with the bore; and
[0009] (b) an inflatable tube disposed concentrically about the
mandrel, the tube positioned between the first end and second end
of the mandrel and covering the first port, the tube being
sealingly secured on the mandrel near the respective ends of the
tube and having an original inner diameter that corresponds to a
second radius (r) so that it approximately matches the outer
diameter of the mandrel (R.sub.mandrel), a length (L) less than the
length of the mandrel, a wall thickness (t) such that:
(0.4225.times.r)<t.ltoreq.(0.660.times.r).
[0010] According to an aspect of the invention, the the inflatable
tube further includes a volume (vtube) of an elastomeric
material:
v.sub.tube=.pi.L(2rt+t.sup.2).
[0011] The elastomeric material is desirably an elastomeric
silicone. The elastomeric silicone desirably has a Shore Hardness
(durometer hardness) of about 25 A to about 35 A (as initially
reported by the manufacturer) and has a Shore Hardness (durometer
hardness) after processing into an inflatable tube of between about
30 A and about 40 A. More desirably, the elastomeric silicone has a
Shore Hardness (durometer hardness) after processing into an
inflatable tube of about 35 A to about 40 A. According to the
present invention, the introduction of a volume of liquid
(v.sub.liquid) between the mandrel and the inflatable tube expands
and pressurizes the tube such that the pump subsequently dispenses
substantially all the volume of liquid through the first port upon
contraction of the tube to substantially its original inner
diameter. The volume of liquid (v.sub.liquid) is determined
according to the following equation:
(12.50.times.v.sub.tube).ltoreq.v.sub.liquid.ltoreq.(22.16.times.v.sub.t-
ube)
and it is introduced through the fill port at a fill pressure of
greater than 0 and less than 35 psig.
[0012] The present invention also encompasses an elastomeric pump
for an infusion assembly as generally described above wherein the
pump dispenses substantially all the volume of liquid through the
first port.
[0013] Generally speaking, the present invention relates to the
discovery of certain relative ratios of tube wall thickness and
liquid fill volumes that result in specific pressure ranges for the
purpose of infusing 50-600 ml of liquid at relatively uniform flow
rates until almost all the liquid is expelled. According to an
aspect of the invention, the expansion of the tube to contain a
given fill volume (e.g., 50-600 milliliters) may be readily
accomplished by manual injection from a syringe device (filling
pressure upstream of the tube is less than 35 psig). In another
aspect of the invention, there is minimal residual volume of liquid
in the tube after expelling substantially all of the liquid (i.e.
less than 4 milliliters of liquid remaining in the inflatable
tube). In another aspect of the invention, delivery of at least 60%
of the fill volume of liquid is at a substantially uniform flow
rate at pressures of 6.0-14.0 psig (as measured downstream of the
expanded inflatable tube). In yet another aspect of the invention,
the inflatable tube is a single monolithic or homogeneous tubular
material. That is, the inflatable tube desirably lacks discrete
layers and is a single extruded piece of tube. Desirably the
inflatable tube is a single monolithic or homogenous silicone
tube.
[0014] Other objects, advantages and applications of the present
disclosure will be made clear by the following detailed description
of a preferred embodiment of the disclosure and the accompanying
drawings wherein reference numerals refer to like or equivalent
structures.
DESCRIPTION OF THE DRAWINGS
[0015] FIGS. 1A and 1B are illustrations of a graph of data and
information from Crack Pressure and Fill Pressure testing of
comparative examples of inflatable tubes.
[0016] FIG. 2 is an illustration of a graph showing the minimum and
maximum Fill Pressures that are used to calculate a single Average
Fill Pressure for an exemplary improved inflatable elastomeric
pump.
[0017] FIG. 3 is an illustration of a graph showing an exemplary
depressurization curve (profile) for averaged operating pressures
on the y-axis at averaged volumes on the x-axis for exemplary
elastomeric pumps of the invention.
[0018] FIG. 4 is an illustration of a graph showing averaged
Operating Pressure profiles for exemplary expanded tubes of
exemplary elastomeric pumps that track their depressurization from
their Fill Volumes with respect to time (Infusion Time).
[0019] FIG. 5 is an illustration of a graph showing Operating
Pressure versus infusion time as measured downstream from the
inflatable tube and mandrel for four different sample sets of
silicone tubes.
[0020] FIG. 6 is an illustration of a graph showing the pressure on
the y-axis and the volume on the x-axis for respective
pressurization and depressurization cycles for exemplary improved
inflatable elastomeric pumps.
[0021] FIG. 7 is an illustration of the graph of FIG. 6 but also
including additional information from Table 6 for Examples A-C as
well as Example 4.
[0022] FIG. 8 is an illustration of a graph showing a pressure
curve resulting from the Fill values of FIG. 7 with respect to
their corresponding wall thickness.
DETAILED DESCRIPTION
[0023] Reference will now be made in detail to one or more
embodiments, examples of which are illustrated in the drawings. It
should be understood that features illustrated or described as part
of one embodiment may be used with another embodiment to yield
still a further embodiment.
[0024] The improved inflatable elastomeric pump for an infusion
assembly may have the general configuration as described in U.S.
Pat. No. 5,284,481 for "Collapsible Compact Infusion Apparatus"
issued Feb. 8, 1994 to Soika et al., the entire contents of which
are incorporated herein by reference. Deficiencies of the
elastomeric pump portion of infusion pumps discussed at column 1 of
that reference are addressed by the improved inflatable elastomeric
pump as described herein.
[0025] Pressure conditions measured "upstream" or "downstream" of
the invention will proportionally reflect conditions within the
invention and specifically will reflect expansion and contraction
states of the silicone tube. Upstream pressures characterize those
pressures that act on the liquid as it is injected into the tube to
expand the tube from an initial unexpanded state to the maximum
expanded state. The maximum expanded state accommodates a Fill
Volume. Because the liquid is injected from a syringe-type device
through a one-way valve connector before it enters the tube, the
pressure upstream of the one-way valve is dynamically measured
while injection is occurring; hence these upstream pressures are
greater than the pressures within the tube. (The syringe device and
especially the valve connector can act as upstream flow restrictors
and there typically is no allowance for equilibration of pressure
conditions before and after the valve connector.) These upstream
pressures move the liquid through the valve connector, then through
one end of the mandrel and out the first port, and then against the
inside surface of tube.
[0026] The measured upstream pressures ahead of the valve connector
are termed Crack Pressures and Fill Pressures. The Crack Pressures
indicate the forces that must be transmitted by the liquid to
overcome the initial resistance to expansion of the inflatable
tube. Fill Pressures indicate gradual expansion of the tube between
the fixed ends attached to the mandrel; the expansion is in a
general radial direction with respect to the center axis of the
tube. The Fill Pressures initially decrease from the maximum Crack
Pressure and then increase to a maximum when the Fill Volume is
achieved. Typical measured upstream pressure data is shown in FIGS.
1A and 1B for multiple injection cycles into silicone tubes (one
injection of 100 milliliters Fill Volume per tube). That is, FIGS.
1A and 1B are graphs of the measure pressure of liquid in the
inflatable tube versus (y-axis) for an individual injection cycle
in 5 individual tubes (x-axis) (each cycle, .about.15 second in
duration).
[0027] The tubes of FIGS. 1A & B all have 0.355'' ID and 3.05''
length but have different wall thickness and/or durometer hardness
on mandrels of the same dimensions. As indicated on FIG. 1A: Groups
A-C represent the injection of 100 milliliters (mis or ml) into 5
individual tubes made from an elastomeric silicone material having
a measured durometer hardness of 25 A before processing into the
tubes (i.e., a 25 A durometer hardness material) and with 0.055,
0.065, and 0.075 inch wall thickness respectively and Group D
represents similar individual injections into tubes made from an
elastomeric silicone material having a measured durometer hardness
of 30 A before processing into the tubes (i.e., a 30 A durometer
hardness material) with wall thickness of 0.045 inches. As
indicated in FIG. 1B: Group 1 represents the injection of 100 ml
into 5 individual tubes with 0.065 wall thickness and a 30 A
durometer hardness material; Groups 2, 3, and 4 represent similar
individual injections into tubes of 35 A durometer hardness
material and respective wall thickness of 0.045, 0.055 and 0.065
inches. For each individual injection (cycle, .about.15 second in
duration) a maximum Crack Pressure is the left-most peak and a
maximum Fill Pressure is the right-most peak.
[0028] The Groups of FIG. 1A and FIG. 1B illustrate the variations
observed for Crack and Fill Pressures for silicone tubes in general
(of the invention and not of the invention). Groups A-C (FIG. 1A)
and Group 1 (FIG. 1B) exhibit maximum Crack Pressures that are less
than the maximum Fill Pressures; Group 4 (FIG. 1B) exhibits the
reverse; Groups D (FIG. 1A), Groups 2 and 3 (FIG. 1B) exhibit
instances for such maximum pressures being greater than, less than,
or equal to one another. The information depicted in FIGS. 1A and
1B suggests that for tubes of the same inner diameter (ID): [0029]
Silicone tubes of 30 A and less durometer hardness material exhibit
maximum Crack Pressures that are less than the maximum Fill
Pressures [0030] For silicone tubes of a given durometer hardness,
the thicker the wall the greater the maximum Crack Pressure with
respect to the maximum Fill Pressure
[0031] More conclusive for tubes of a given ID are the following
relationships among Fill Pressures, wall thickness, and durometer
hardness: [0032] At a given wall thickness, the greater the
durometer hardness the greater the Fill Pressures [0033] At a given
durometer hardness, the thicker the walls the greater the Fill
Pressures
[0034] Thus there are numerous combinations for durometer hardness
and wall thickness that one can choose to achieve a specific
maximum Fill Pressure.
[0035] One method for recording Fill Pressures is to average the
minimum and maximum Fill Pressures into a single Average Fill
Pressure value for a given fill cycle. FIG. 2 illustrates such
minimum and maximum data points for calculating an Average Fill
Pressure (Ave Fill Pressure) for a mandrel supported silicone tube
of the invention with the tube having a 0.10'' wall thickness, an
ID of 0.355 inches, and a length of 3.05 inches. In FIG. 2, the
y-axis represents the pressure of liquid in the inflatable tube and
the x-axis is time in seconds. The cycle is approximately 15
seconds in duration, starting at about 35 seconds and ending at
about 50 seconds. Table 1 gives such average values for the data
represented in FIG. 1 and for additional groups T and E (, not
shown in the FIG. 1 but with 5 individual fill cycles each) as;
these Average Fill Pressure values correspond to the "Unsterilized
As-Made" sample type values in Table 1. Also presented in Table 1
is data for other samples that are the same as the Unsterilized
As-Made but after exposure to one of two types of sterilization:
"Post-Gamma" values are for samples after their sterilization by
exposure to gamma radiation; "Post-EtO" values are for samples
after their sterilization by exposure to ethylene oxide. As the
values of Table 1 indicate, ethyene oxide sterilization has
negliglbe effect while gamma radiation increases the Crack and Fill
Pressures by .about.6 to .about.16%. Such impact due to
sterilization conditions is also observed for other silicone tubes
of 30 A durometer hardness material with walls up to 0.180 inch
thickness, and presumedly greater.
TABLE-US-00001 TABLE 1 Average Fill Pressure (PSIG) Group T A B C D
E 1 2 3 4 Durometer - Wall thickness 25A- 25A- 25A- 25A- 30A- 30A-
30A- 35A- 35A- 35A- .045 .055 .065 .075 .045 .055 .065 .045 .055
.065 Sample Type: Unsterilized As-Made 15 17 17.5 19 19 21 23 25 27
30 Post-Gamma 16 16 20 22 21 24 25 28 30 34 Post-EtO 15 17 17 20 20
21 24 25 28 31
[0036] FIG. 2 shows that both the maximum Crack and Fill Pressures
are less than 35 psig; this criteria, regardless of time duration
for the fill cycle, is a desirbable characteristic of the
invention.
[0037] While Crack and Fill Pressures reflect the pressure
conditions that act on the silicone tubes, Operating Pressures
directly provide information about the actual pressure conditions
on the tubes. The Operating Pressures are measured downstream of
the mandrel and silicone tube invention and have no intervening
blockage in the liquid flow path from the silicone tube to the
pressure sensor. Thus the pressure acting on the silicone tube is
transmitted hydrostatically and continuously downstream of the
invention. Because the downstream conduits are generally designed
to delivery approximate flow rates of 1-4 ml/hour, pressure
conditions against the silicone tube equilibrate relatively quickly
with pressure conditions downstream of the mandrel and silicone
tube assembly. When the pressure sensor is inserted into direct
communication with the liquid in the conduit (e.g. tubing) within 2
feet of the first port the measured pressures via the sensor are
essentially those acting on the silicone tube; thus such Operating
Pressures are portrayals of the actual pressures on the silicone
tube.
[0038] Silicone tubes of interest for the invention share a common
characteristic "depressurization" profile as liquid, initially at a
Fill Volume, is squeezed out of the silicone tube and delivered
downstream over time. FIG. 3 provides an illustrative example of
the characteristic depressurization curve; the example is
representative of the dimensions of Tube 1 per Table 2 and of a
silicone with a durometer hardness of 30 A. In FIG. 3, the y-axis
is average operating pressure of liquid in the inflatable tube and
the x-axis is volume of liquid in the tube.
[0039] Additional exemplary dimensions for silicone tubes of the
invention are given in Table 2. Each of the tubes have mandrels
that support the tube in the absence of contained liquid; the
respective mandrel (for Tubes 1, 2, 3, 4) has an OD sized to match
the ID of the tube and a length greater than the tube.
TABLE-US-00002 TABLE 2 Tube Silicone Tube Dimensions, inches 1 2 3
4 ID, inch 0.355 0.6 0.6 0.6 OD, inch 0.555 0.88 0.88 0.96 Wall,
inch 0.1 0.14 0.14 0.18 Length, inch 3.05 3.75 4.75 4.75 Tube
Volume, in.sup.3 0.43597 1.22051 1.54598 1.65405 Fill Volume, ml
(in.sup.3) 100 (6.1024) 250 (15.256) 400 (24.409) 600 (36.6140)
[0040] Silicones with a durometer hardness (Shore hardness) of 35 A
or less are suitable for forming the tube. Such silicones in the
dimensions represented by Tubes 1-4 allow for allow expansion of
the tube to contain liquids up to the indicated Fill Volumes.
Appropriate selection of silicones are ones that: form inflatable
tubes; result in any maximum pressures that are greater than 12
psig but less than 35 psig when inflated with a predetermined Fill
Volume of liquid as measured a short distance downtream of the
first port; and provide sufficent constricting forces to expell
almost all the Fill Volume liquid. Exemplary silicones are: NUSIL
4020 (also called MED-4020) with a Shore hardness of 25 A (as
reported by the manufacturer); NUSIL 4025 (also called MED-4025)
with a Shore hardness of 30 A (as reported by the manufacturer);
NUSIL 4030 (also called MED-4035) with a Shore hardness of 35 A (as
reported by the manufacturer). NUSIL 4025 is a preferred silicone.
The durometer hardness of the silicone that is used to make the
tubes is a material parameter of the invention. Values for the
durometer hardness are measured and given per the Shore A scale.
The exemplary silicone polymers sold under the designation NUSIL
MED-4020, MED-4025 and MED-4035, as well as other polymers (e.g.,
MED-4050, MED-4065) are available from NuSil Technology, LLC of
Carpinteria, Calif., USA.
[0041] The Shore Hardness testing of plastics is most commonly
measured by the Shore (Durometer) test using either the Shore A or
Shore D scale. The Shore A scale is used for "softer" rubbers while
the Shore D scale is used for "harder" ones. The Shore A Hardness
is the relative hardness of materials such as rubber or soft
plastics and can be determined with an apparatus known as a
Durometer and is sometimes also referred to as Durometer Hardness
(or durometer hardness).
[0042] The hardness value is determined by the penetration of the
Durometer indenter foot into the sample. If the indenter completely
penetrates the sample, a reading of 0 is obtained, and if no
penetration occurs, a reading of 100 results. The reading is
dimensionless. Because of the resilience of rubbers and plastics,
the hardness reading may change over time so the indentation time
is sometimes reported along with the hardness number. The durometer
hardeness values measured for the tubes presented in connection
with this invention are determined per ASTM D2240 procedures and
use a time interval of approximately 1 second between initial
indentor travel cessation and the recording of the indicated
reading (as considered standard). The analogous ISO test method to
this ASTM test number is ISO 868. The given values for the material
durometer hardness values are vendor provided.
[0043] It is noted that processing of the silicone into an
inflatable tube and curing the tube may have an impact on the Shore
Hardness. Sterilization of the tube and inflation/deflation or
mechanical working of the material for at least one cycle may also
have an impact on the Shore Hardness. Table 3 reports the Shore A
Hardness measured for a series of inflatable tubes corresponding to
Inflatable Tube #3 from Table 2 (Inside Diameter=0.6 inch, Outside
Diameter 0.88 inch, Wall Thickness 0.14 inch, design volume 400
milliliters). These tubes were made by extruding NUSIL 4025 (Shore
ardness of 30 A as reported by the manufacturer--also referred to
as Shore A hardness of 30). Three (3) separate tubes were tested.
The average results and corresponding standard deviations in Table
3 are for the extruded & cured tube; tube sterilized utilizing
a conventional Ethylene Oxide (EO) sterilization cycle; and
sterilized tube loaded with sterile water and allowed to deflate
over a period of approximately 279 hours (i.e., cycled). The
results are based on six (6) measurements per tube.
TABLE-US-00003 TABLE 3 SHORE A HARDNESS Standard SAMPLE Average: n
= 6 Deviation Extruded & Cured 37.00 1.14 EO Sterilized 36.83
2.70 EO Sterilized & Cycled 36.75 1.37
[0044] As can be seen from Table 3, extruding the Nusil 4025 into
inflatable tubes and curing the tubes with heat increases the Shore
A hardess from a nominal value of 30 (as reported by the
manufacturer) for the unprocessed material to a value of about 37
for the tube. Sterilization with ethylene oxide and recoverable
stretching do not appear to produce a meaningful change to the
Shore A hardness.
[0045] A structural parameter of the invention is the wall
thickness, t, of the inflatable tube. An exemplary range of wall
thicknesses for silicone tubes made from NUSIL 4025 are greater
than 0.075 inches up to 0.180 inches. Another structural parameter
is the inner diameter, ID, of the tube and exemplary ranges are
0.355 inches to 0.600 inches. Another parameter is the length, L,
of the tube. The Tube Volume (equivalently Tube Vol and vtube) is
derived from these parameters according to conventionally accepted
mathematical relationships. Also from the t, ID, L, and Tube Vol
values are certain ratios that can characterize the invention.
[0046] Appropriate combinations of the structural and material
parameters yield tubes of the invention that accommodate Fill
Volumes from 50-600 ml of liquid.
[0047] FIG. 4 shows averaged Operating Pressure profiles for
expanded tubes that track their depressurization of liquid expelled
from the expanded tube beginning from their Fill Volumes with
respect to time (Infusion Time) reported in hours. The tubes used
in making FIG. 4 are examples of the invention, have the structural
parameters of Table 2, and are made from NUSIL 4025 silicone which
has a material parameter of 30 A durometer hardness. Table 4
identifies these examples as Examples 1-4 and their respective
connection to Table 2. Table 4 also specifies the Operating
Pressure at .about.0 Infusion Time, which is essentially the
equilibrated pressure that acts against the tube wall while
containing all the Fill Volume. Additional information in Table 4
provides the Design Flow rates that indicate the degree of
downstream restrictions that are intentionally made to modulate the
flow rate and specifies the number of individual samples for the
examples that were used to obtain the averaged Operating Pressure
profiles.
[0048] Each profile of FIG. 4 displays the depressurization
charactertistics of FIG. 3: a maximum Operating Pressure at 0
Infusion time, a second peak towards the completion of
depressurization, and a generalized plateau between the maximum
Operating and second peak pressures. The pressure values for Ex. 1
are similar to those for the tube of FIG. 3 (Tube 1) as expected
since they have structural and material parameters in common. FIG.
4 shows pressures with respect to time while FIG. 3 shows them with
respect to expelled volume (volume in the tube and infusion time
are interrelated). It is noteworthy that the second peaks and
plateaus of each profile have similar pressure values. As shown
subsequently, the differences in the maximum Operating Pressures
can be explained via ratios that are based on certain structural
parameters.
[0049] FIG. 4 also indicates that almost all of the Fill Volume
liquid is expelled at the completion of depressurization. This is
an important feature of the invention. Desirably, none of the tubes
of the invention retain more than just a few millileters of liquid
upon complete depressurization. For example, the tubes of the
present invention retain less than about 10 mls of liquid upon
complete depressurization. As another example, the tubes of the
present invention retain less than about 5 mls of liquid upon
complete depressurization. As yet another example, the tubes of the
present invention retain less than about 4 mls of liquid upon
complete depressurization. As still another example, the tubes of
the present invention retain less than about 2.5 mls of liquid upon
complete depressurization.
TABLE-US-00004 TABLE 4 Structural Parameters that correspond Design
Fill Operating ~0 Calculated to Table 2 Flow rate, Volume,
Pressure, Infusion Expel Ex. Silicone Tube Description per FIG. 4
ml/hr ml psig time, hrs Time, hr 1 1 0.100'' (100 mlx2, n =
19).sup. 2 100 13.14 0 50 2 2 140'' (270 mlx1, n = 20) 1 270 12.58
0.5 270 3 3 140'' (400 mlx4, n = 20) 4 400 11.24 0.083 100 4 4
180'' (600 mlx2, n = 3) 2 600 13.09 0 300
[0050] For purposes of characterizing tubes that are not
representative of the invention, it has been found that tubes made
from NUSIL 4025 (material durometer hardness=30 A) with wall
thickness of 0.075 or less lack sufficent constrictng forces in the
expanded tube to expel almost all of the Fill Volume at the desired
Operating Pressures. The importance of having sufficent
constricting force to expel the Fill Volume liquid is shown in FIG.
5. More particularly, FIG. 5 is a graph of Operating Pressure of
liquid expelled from the tube (that is measured downstream from the
silicone tube and support mandrel and before flow restrictors) for
four different sample sets of silicone tubes versus infusion time
(reported in hours). All the tubes were made from NUSIL 4025 (Shore
hardness 30 A) with a length of 3.05 inches and an ID of 0.355
inches and were filled with a Fill Volume liquid of 100 ml.
[0051] The top curve of FIG. 5 represents Ex. 1, a tube with
0.100'' thick wall and indicates acceptable pressure behavior with
respect to the invention; the next highest curve represents Ex. C,
a tube with 0.075'' thick wall; the following curve represents Ex.
B, a tube with 0.065'' thick wall; and the lowest curve represents
Ex. A, a tube with 0.055'' thick wall. After 50 hours, only the
tube with 0.100'' thick wall expelled all of the Fill Volume
liquid; the other tubes had insufficent constricting forces to
overcome the downstream restrictions that dramatically slowed
expulsion of the 100 ml Fill Volume from those tubes. FIG. 5 also
provides a comparison of the maximum Operating Pressures that
expand the tube walls away from the mandrel when the tubes contain
all 100 ml of the Fill Volume liquid; these pressures are the "Y"
intercepts of the curves at 0 Infusion time. (At 0 Infusion time,
when none of the Fill Volume has been expelled, the Operating
Pressure essentially equals the expanding pressure that provides
the force to counter the constricting forces that are inherent in
the tube.) These expanding pressures for 100 ml Fill Volume liquid
are given in Table 5.
TABLE-US-00005 TABLE 5 0.355'' ID .times. 3.05'' length tubes from
NUSIL 4025 silicone (Shore hardness of 30A - as reported by
manufacturer) supported on matching mandrels Example Ex. A Ex. B
Ex. C Ex. 1 Tube Wall, inch 0.055 0.065 0.075 0.100 Expanding
pressure, psig 4.434 5.0875 5.874 13.138 (at 0 Infusion time)
[0052] To further establish the direct connection between Operating
Pressures and pressures acting against the tubes the following
`static` experiment was conducted. The pressures at a very short
distance downstream of the first port were recorded as selected
mandrel-supported silicone tubes, suitable for the invention, were
inflated to and deflated from Fill Volumes in 25 ml increments. The
selected tubes are identified as Ex. 11, 21, 31, and 41 and are
described with respect to structural parameters in Table 6. These
tubes were made from NUSIL 4025, thus their material parameter was
a durometer hardness of 30 A. That is, the tubes were made from a
material having a durometer hardness of 30 A prior to processing
into the tubes. Table 6 also reproduces the recorded pressures
(pressure data points) for each Ex. 11, 21, 31, and 41 with
respective Fill Volumes of 100, 250, 400, and 600 milliliters as
obtained via the following `Inflation/Deflation Curves` Procedure.
These pressures were graphed in FIG. 6 with respect to volume to
give an inflation curve towards each respective Fill Volume and a
deflation curve away from the Fill Volume. (The pressure data
points for injecting are shown as solid markers; those of
dispensing are unfilled markers.)
Inflation/Deflation Curves Procedure for Ex. 11, 21, 31, and 41
(the Static Experiment):
[0053] 1. Obtain a new mandrel and silicone tube assembly with
attached downstream conduit
[0054] 2. Cut the downstream conduit approximately 5'' from its
connection end to the mandrel and attach male Luer with two
connection ports, one with a valve mechanism that is closed.
[0055] 3. Connect the pressure transducer to the connection port
without the valve mechanism and prime the line with saline before
connection.
[0056] 4. Using a syringe, inject 25 ml of saline for each pressure
data point through the valve mechanism when opened.
[0057] 5. Measure pressure one minute after each injection.
[0058] 6. Repeat until Fill Volume is obtained.
[0059] 7. Measure pressure as the silicone tube is depressurized
(emptied) dispense 25 ml at a time by opening the valve mechanism.
Measure pressure one minute after 25 ml is dispensed until all of
the Fill Volume is removed.
TABLE-US-00006 TABLE 6 Pressure, PSI for: Reservoir Tube Ex. 11 Ex.
21 Ex. 31 Ex. 41 Tube Exterior 0.555'' OD .times. 0.880'' OD
.times. 0.880'' OD .times. 0.960'' OD .times. Dimensions 3.05'' L
3.75'' L 4.25'' L 4.25'' L Wall thickness 0.10'' 0.14'' 0.14''
0.18'' to Fill from Fill to Fill from Fill to Fill from Fill to
Fill from Fill Vol, ml Vol Vol Vol Vol Vol Vol Vol Vol 0 0 0 0 0 0
0 0 0 25 13.39 7.99 14.71 8.29 14.43 7.36 18.53 7.78 50 14.46 8.21
14.5 7.93 14.41 7.5 18.83 8.65 75 16.31 10.17 14.09 7.81 13.32 7.07
17.74 8.37 100 18.11 18.11 14.1 7.73 13 6.95 16.95 7.92 125 14.23
7.98 12.91 6.95 16.58 7.68 150 14.49 8.37 12.86 6.9 16.4 7.49 175
14.81 8.75 12.36 6.96 16.28 7.6 200 15.12 9.72 12.67 7.01 16.25
7.61 225 15.35 11.1 12.87 7.31 16.31 7.69 250 15.59 15.59 13.1 7.73
16.41 7.61 275 13.32 8.08 16.5 7.79 300 13.53 8.64 16.53 8 325
13.77 9.33 16.42 8.18 350 14.01 9.98 16.39 8.1 375 14.27 11.16
16.43 8.42 400 14.54 14.54 16.54 8.69 425 16.66 9.15 450 16.81 9.43
475 17.01 10.28 500 17.24 10.84 525 17.5 11.81 550 17.75 12.65 575
18.01 13.97 600 18.3 18.3
[0060] The inflation curves of FIG. 6 share characteristics of the
Crack and Fill Pressures previously described and the deflation
curves closely mirror the Operating Pressures for tubes of similar
structural and material parameters and relatively similar Fill
Volumes. Table 7 compares maximum, second peak and general plateau
pressures as shown in FIG. 6 per Table 6 with maximum, second peak,
and general plateau Operating Pressures as given in previous Tables
and Figures.
[0061] The magnitudes of the pressures at the Fill Volumes of FIG.
6 also indicate a relationship between pressure and actual wall
thickness. Ex. 11 with the thinnest initial wall and shortest for
length, thus it has the smallest Tube Volume (per Table 8,
equivalent to dimensions of Tube 1 per Table 2), has a pressure at
its Fill Volume (100 ml) that is comparable to that for Ex. 41 (at
600 ml Fill Volume), which has the thickest initial wall and
longest length, hence the greatest Tube Volume (per Table 8,
equivalent to dimensions of Tube 4 per Table 2). Ex. 21 and Ex. 31
have lower pressures at their Fill Volumes.
[0062] One explanation for the magnitude differences in pressures
at respective Fill Volumes is that: Ex. 11 and Ex. 41 should have
comparably thinner actual walls at their Fill Volumes compared to
Ex. 21 and Ex. 31 and therefore exert the greater constricting
forces per unit surface area at these Fill Volume; Ex. 21 should
have the next thinner actual wall at its Fill Volume and thus the
next greater constricting force per unit area; Ex. 31 should have
an actual wall thickness at its Fill Volume that is greater than
that of Ex. 21 and therefore has less constricting force per unit
surface area. In other words Ex. 11 and Ex. 41 are expanded
(stretched) more towards their limit of plastic deformation (yield
point, past which the tube will not quickly return to its original
dimensions before filling). Ex. 21 and 31 should be respectively
thicker and thus should allow for more expansion before reaching
the actual thinness of Ex. 11 at its Fill Volume. The Operating
Pressures of Ex. 1-4 per Table 7 show similar magnitude differences
that are consistent with the offered explanation: the maximum
pressure of Ex. 1 (like Ex. 11) is comparable to Ex. 4 (like Ex.
41) while the maximum pressures for Ex. 2 (like Ex. 21) and Ex. 3
(like Ex. 31) are less.
[0063] The offered explanation is further supported when the shape
of each tube at its Fill Volume is assumed to be a sphere and tube
is assumed to form a shell around the sphere. Given the accepted
volume-to-radius relationship for a sphere, the above assumptions,
and the appropriate values of Table 8, the shell thicknesses at
each Fill Volume calculate as: 0.0264'' for Ex. 11, 0.0306'' for
Ex. 41; 0.0399'' for Ex. 21; 0.0372'' for Ex. 31.
[0064] Table 7 also gives maximum pressure values (all Operating
Pressures) for examples Ex. A, B, and C, which are lower than Ex.
1, and thus in contradiction to the preceding explanation. This
contradiction can be explained if the initial Crack and Fill
Pressures for Ex. A, B, and C tubes produced stretching forces that
closely approached or exceeded the limit of plastic deformation so
that these tubes will not recover their initial dimensions. The
lack of respective second peaks in pressure per FIG. 5 indicates
this is the case.
[0065] Table 7 allows comparisons of the maximum pressures at Fill
Volumes (Fill) for tubes that are essentially the same: values for
Ex. 11 to those of Ex. 1; those of Ex. 21 to those of Ex. 2; etc.
The difference in the maximum pressures at Fill can be explained as
stress relaxation phenomena common to elastomeric materials. The
measured pressures at Fill for Ex. 11-Ex. 41 were all made 1 minute
after the Fill volume was attained. The maximum pressures for Ex.
1-4 are the Operating Pressures at 0 infusion time, which implies
these examples have been containing the same respective Fill
Volumes as for Ex. 11-Ex. 41 for sufficiently long enough periods
of time to allow some of the molecular entanglements that are
initially present when the tubes are inflated to rearrange and
dissipate some of the constricting energy. Indeed, should the
maximum pressure for Ex. 11 have been held for a time longer than
that given per the procedure, it is conceivable that the maximum
pressure value for Ex. 11 will decay to the lower maximum pressure
value for Ex. 1. In other words, the maximum pressures at Fill per
the Inflation/Deflation Curves procedure should decay to the
equilibrium pressures as represented by the Operating pressures at)
infusion time.
TABLE-US-00007 TABLE 7 Pressure values Wall .times. Maximum Second
Tube Source Length, inch at Fill Peak Plateau Ex. 11 Table 6 0.010
.times. 3.05 18.11 7.99 7.99-8.21 Ex. 1 FIG. 4 data; 13.14 7.94
7.94-9.01 FIG. 3 Ex. 21 Table 6 0.140 .times. 3.75 15.59 8.29
8.29-9.72 Ex. 2 FIG. 4 Data 12.56 7.50 7.50-8.35 Ex. 31 Table 6
0.140 .times. 4.75 14.54 7.50 7.50-9.33 Ex. 3 FIG. 4 data 11.24
7.46 7.46-8.50 Ex. 41 Table 6 18.3 8.65 8.65-9.43 Ex. 4 FIG. 4 data
0.180 .times. 4.75 13.09 6.81 6.81-7.02 Ex. A Table 2; 0.055
.times. 3.05 4.43 -- 2.80-3.00 FIG. 5 Ex. B Table 2; 0.065 .times.
3.05 5.09 -- 2.90-3.50 FIG. 5 Ex. C Table 2; 0.075 .times. 3.05
5.87 -- 3.80-4.20 FIG. 5
[0066] When ratios based on structural parameters for the tubes of
Table 6 are compared in light of their pressure values, these
ratios point to ranges that characterize the suitability for use in
the invention. Table 8 lists structural parameters and various
ratios based on them. Of primary relevance for defining dimensions
for tubes that may be suitable candidates for use in the invention
are the ratios of wall thickness t to tube inner radius r or the
outer radius as shown in items j) and k) respectively. Since these
ratios are expressions of the same structural parameters, item j),
the ratio of t to the inner tube radius r, will be used to identify
limitations. Of secondary relevance is the ratio for the Fill
Volume to the Tube Volume, as shown in item I). Given that tubes of
Ex. 1-4 and Ex. 11-41 (all from 30 A durometer hardness material)
exhibit preferred pressure behavior up to their respective Fill
Volumes, their ratio values per item j) and item I) are within the
range of acceptability for the invention. Since Ex. C exhibits
unacceptable pressure behavior at its indicated Fill Volume, the
value of the j) ratio lies outside the lower limit of
acceptability. The value of the item j) ratio for Ex. 4 & Ex.
41 is determined to be within the acceptable range per its pressure
behavior up to its Fill Volume and sets an upper limit in light of
the value for the ratio of item I) versus those for Ex. A and Ex.
B, which have unacceptable pressure behaviors for their Fill
Volumes. In other words, acceptable structural parameters for tubes
suitable for the invention are defined by item j) ratios from
greater than 0.42254 to 0.6.
[0067] A graphic depiction of such an acceptable range is
illustrated by FIG. 8 which is derived from Fill values of FIG. 7
that are based on Table 7 data points for maximum at Fill values
that correspond to Operating pressures at 0 infusion time. FIG. 7
shows the same information as FIG. 6 but includes the maximum
pressures per Table 7 for Ex. A-C (unacceptable for the invention)
and Ex. 1-4 (acceptable for the invention). FIG. 8 plots the
maximum pressures per Table 7 for Ex. A-C and Ex. 1-4 with respect
to their corresponding wall thickness; clearly a lower bound of
acceptability for tubes with ID values of 0.355 inches exists for
wall thickness between 0.075 and 0.100 inches and an upper bound
seemingly exists for tubes of ID values of 0.600 inches and a wall
thickness of or near 0.180 inches.
TABLE-US-00008 TABLE 8 Examples Ex. 1 & Ex. 2 & Ex. 3 &
Ex. 4 & item Ex. A Ex. B Ex. C Ex. 11 Ex. 21 Ex. 31 Ex. 41 a)
ID, in 0.355 0.355 0.355 0.355 0.6 0.6 0.6 b) OD, in 0.465 0.485
0.505 0.555 0.88 0.88 0.96 c) t (Wall), in 0.055 0.065 0.075 0.1
0.14 0.14 0.18 d) L (Length), in 3.05 3.05 3.05 3.05 3.75 4.75 4.75
e) Tube Vol, in.sup.3 0.21607 0.26158 0.30901 0.43597 1.22051
1.54598 1.65405 f) Fill Vol, in.sup.3 6.1024 6.1024 6.1024 6.1024
15.256 24.409 36.614 g) Fill Vol, ml 100 100 100 100 250 400 600 h)
r (=ID/2), in 0.1775 0.1775 0.1775 0.1775 0.3 0.3 0.3 i) R (=OD/2),
in 0.2772 0.2772 0.2772 0.2772 0.44 0.44 0.48 j) t/r 0.30986
0.36620 0.42254 0.56338 0.46667 0.46667 0.6 k) t/R 0.23656 0.26804
0.29703 0.36036 0.31818 0.31818 0.375 l) Fill Vol/ 28.2427 23.3290
19.7482 13.9973 12.4997 15.7887 22.1360 Tube Vol
[0068] The relationship of the pressures at the Fill Volumes per
the Inflation/Deflation Curves Procedure to the Operating Pressures
was demonstrated by duplicating the filling part of the Procedure
to the Fill Volume with a new (previously unexpanded) set of Ex.
11, 21, 31, and 41 tubes, which are identified as Ex. 11A, 21A,
31A, and 41A, and then modifying the Procedure to allow 24 hours to
lapse. Once the pressures were recorded approximately 1 minute
after reaching their Fill Volume, the tubes retained these Fill
Volumes for approximately 24 hours, then the pressures at the Fill
Volume were recorded again and the emptying part of the Procedure
was subsequently followed. As the results given in Table 9 show,
all the after 24 hours Fill Volume pressures were lower than the
after 1 minute Fill Volume pressures by 30-34%. Comparing Table 9
to Table 6 values indicates that the 24 hour delay also results in
lower pressures as liquid is removed.
TABLE-US-00009 TABLE 9 Pressure, PSI for: Reservoir Tube Ex. 11A
Ex. 21A Ex. 31A Ex. 41A Tube Exterior 0.555'' OD .times. 0.880'' OD
.times. 0.880'' OD .times. 0.960'' OD .times. Dimensions 3.05'' L
3.75'' L 4.25'' L 4.25'' L Wall thickness 0.10'' 0.14'' 0.14''
0.18'' to Fill After to Fill After to Fill After to Fill After Vol,
ml Vol 24 hrs Vol 24 hrs Vol 24 hrs Vol 24 hrs 0 0 0 0 0 0 0 0 0 25
13.61 7.56 14.60 6.33 15.86 5.06 18.21 6.06 50 13.3 6.98 14.72 6.91
14.76 6.27 18.45 8.14 75 15.28 7.35 14.37 6.50 13.81 6.09 17.34
8.14 100 17.14 12.01 13.83 6.38 13.38 5.94 16.53 7.86 125 13.86
6.66 13.10 5.75 16.06 7.54 150 14.09 6.91 12.86 5.82 15.75 7.20 175
14.54 6.94 12.68 5.99 15.47 7.19 200 14.93 7.37 12.57 5.88 15.41
7.21 225 15.32 8.30 12.62 5.86 15.34 7.18 250 15.84 10.71 12.76
6.02 15.20 7.40 275 12.92 6.27 15.34 7.23 300 13.01 6.48 15.47 7.51
325 13.09 6.71 15.66 7.40 350 13.28 7.34 15.87 7.50 375 13.57 8.51
15.35 7.64 400 13.90 9.36 15.75 7.86 425 16.05 8.10 450 16.32 8.64
475 16.61 8.90 500 16.89 9.57 525 17.14 9.99 550 17.41 10.76 575
17.66 11.81 600 17.90 12.36
[0069] Comparison of the Operating Pressures of Table 4 to the
after 24 hour Fill Volume pressures of Table 9 for tubes of like
structural parameters leads to the conclusion that these pressures
are essentially the same. A factor that may account for the
slightly higher Operating Pressure values of the Examples of Table
4 compared to the after 24 hour Fill Volume pressures of Table 9,
in addition to possible inherent variations of the individual
samples themselves, was the presence of a confining non-stretchable
housing as described in U.S. Pat. No. 5,284,481 around the tubes
for Table 4 examples, while the tubes of Table 9 lacked such a
housing. Such a confining housing was also present for all the
examples and samples used for Table 1, 3, and 5, while the examples
of Table 6, 9, and 10 lacked a confining housing around the
tubes.
[0070] The Inflation/Deflation Curves Procedure was also used to
see if overfilling of the reservoirs would cause insufficient
constricting forces in the expanded tube to expel the final amounts
of liquid. An unexpanded tube Ex. 11B with structural parameters
like those of Ex. 1, 11 and 11 A was filled to a Fill Volume of 200
ml according to the Inflation/Deflation Curves Procedure used to
generate the values of Table 9 (with a 24 hour delay after reaching
the Fill volume). The results are given in Table 10 and show that,
for this tube, the structural parameters are adequate to provide
sufficient constricting forces to expel all the filled liquid.
Comparing the "to Fill Vol" values up to 100 mls for this Ex. 11 B
to those of Ex. 11 A (Table 9) and Ex. 11 (Table 6) shows there is
a range in measured pressures that is most likely due to sample
variability (all these tubes have the same structural parameters):
12.09 psig for Ex. 11 B, 17.14 psig for Ex. 11A, and 18.11 psig for
Ex. 11. The ratio of Fill Volume of 200 ml/Tube Vol is
approximately 28.
TABLE-US-00010 TABLE 10 Pressure, PSI for: Reservoir Tube Ex. 11B
Tube Exterior 0.555'' OD .times. Dimensions 3.05'' L Wall thickness
0.10'' Vol, ml to Fill Vol After 24 hrs 0 0 0 25 12.53 6.56 50
11.92 5.25 75 11.79 5.03 100 12.09 5.35 125 12.77 6.28 150 13.41
7.13 175 14.00 8.33 200 14.53 --
[0071] Comparative examples that further support the unique
criteria of the invention are found from U.S. Pat. No. 7,704,230;
such comparative examples use reservoirs made of silicone that
match the material parameters of the invention, yet their
structural parameters are different from those found to be
acceptable for the invention. Within U.S. Pat. No. 7,704,230 are
descriptions of certain silicone reservoirs made of NUSIL 4025 that
are understood to have cylindrical tube shapes that "hold about 300
milliliters". These reservoirs are stated to have the following
dimensions: Comp. Ex. 1 has "a preferred axial length of about 3.5
inches, a preferred outer diameter of about 0.130 inches and a
preferred inner diameter of about 0.080 inches"; Comp. Ex. 2 and
Comp. Ex. 3 each "preferably has a wall with a thickness of about
0.063 inches" and is presumed to have the same axial length and
either the inner or the outer diameter of Comp. Ex. 1. Calculations
for structural parameters and ratios like those of Table 8 are made
for these comparative examples based on these stated dimensions;
these are listed in Table 11. An additional comparative example,
Comp. Ex. 4, is given with an axial length of 3.5 inches and an
inner diameter of 0.080 inches but with a wall thickness of 0.0315
inches (half of 0.063 inches).
TABLE-US-00011 TABLE 11 Examples: Comp. Comp. Comp. Comp. item Ex.
1 Ex. 2 Ex. 3 Ex. 4 a) ID, in 0.080 0.080 0.004 0.08 b) OD, in
0.130 0.206 0.130 0.143 c) t (Wall), in 0.025 0.063 0.063 0.0315 d)
L (Length), in 3.50 3.50 3.50 3.50 e) Tube Vol, in.sup.3 0.115
0.396 0.186 0.154 f) Fill Vol, in.sup.3 18.31 18.31 18.31 18.31 g)
Fill Vol, ml 300 300 300 300 h) r (=ID/2), in 0.040 0.040 0.002
0.040 i) R (=OD/2), in 0.0625 0.103 0.0625 0.0715 j) t/r 0.625
1.575 31.5 1.575 k) t/R 0.400 0.612 1.008 0.881 l) Fill Vol/
159.217 46.185 98.573 118.464 Tube Vol
[0072] Referring again to FIGS. 6 and 7, it appears the tubes
generally follow Hooke's law between zero pressure and a yield
point above the designed operating pressure for the infusion pump
(i.e., 6 psi). This Hooke's law behavior is observed for both the
inflation profile and the deflation cycle profile. For the present
invention, the more important yield point is a "deflation yield
point" that appears at about 7 to 8 psi in the deflation portion of
the inflation/deflation cycle for all sizes of the infusion pumps
(i.e., 100 ml to 400 ml).
[0073] With reference to FIGS. 6 and 7 as well as Table 6, the plot
of pressure versus volume during inflation of "Ex.11 to fill"
illustrates that pressure of fluid in the inflatable elastomeric
tube increases in a substantially linear manner from zero to an
inflation yield point (at about 13.4 psig) that is above the target
operating pressure (about 6 psig) as the volume increases from 0
milliliters to a volume of about 25 milliliters. As another
example, the plot of pressure versus volume during inflation of
"Ex. 41 to fill" illustrates that pressure of fluid in the
elastomeric tube increases in a substantially linear manner from
zero to an inflation yield point (at about 18.5 psig) that is above
the target pressure (about 6 psig) as the volume increases from 0
milliliters to a volume of about 25 milliliters.
[0074] Once the pressure exceeds the inflation yield point, the
pressure-volume relationship is generally non-linear. That is, as
the volume of the fluid in the inflatable elastomeric tube
increases, the pressure of the fluid in the inflatable elastomeric
tube has a less predictable response and will increase or decrease
with changes in volume changes. This response is non-Hookean (i.e.,
does not follow Hooke's law) and is attributed to stretching and
deformation of the inflatable tube. As can be seen from FIGS. 6 and
7, the plot of pressure versus volume during inflation of "Ex.11 to
fill" illustrates that pressure of fluid in the inflatable
elastomeric tube increases in a generally non-linear manner from
the inflation yield point (at about 13.4 psig) to the end of the
inflation cycle as the volume increases from about 24 milliliters
to a volume of about 100 milliliters. As another example, the plot
of pressure versus volume during inflation of "Ex. 41 to fill"
illustrates that pressure of fluid in the elastomeric tube responds
in a generally non-linear manner from the inflation yield point (at
about 18.5 psig) to the end of the inflation cycle as the volume
increases from about 15 milliliters to a volume of about 600
milliliters.
[0075] During deflation of the inflatable elastomeric tube, the
pressure-volume relationship is generally non-linear until the
pressure decreases below a deflation yield point. For example, the
plot of pressure versus volume during deflation of "Ex.11 from
fill" illustrates that pressure of fluid in the inflatable
elastomeric tube decreases in a generally non-linear manner from
the end of the inflation cycle/beginning of the deflation cycle to
the deflation yield point (at about 8 psig) as the volume decreases
from about 100 milliliters to a volume of about 25 milliliters. As
another example, the plot of pressure versus volume during
deflation of "Ex. 41 from fill" illustrates that pressure of fluid
in the elastomeric tube responds in a generally non-linear manner
from the end of the inflation cycle/beginning of the deflation
cycle to the deflation yield point (at about 7.8 psig) as the
volume decreases from about 600 milliliters to a volume of about 25
milliliters.
[0076] Referring to "Ex. 11 from fill" and to "Ex. 41 from fill",
as the pressure decreases below the deflation yield point, the
pressure and volume decrease in a substantially linear relationship
until the volume decreases to 0 ml. It is believed that providing a
deflation yield point that is above the target operating pressure
of the infusion pump allows for the reliable and generally complete
evacuation or depletion of the contents of the infusion pump.
[0077] Accordingly, the improved elastomeric pump can be described
as an infusion pump providing a modified hysteresis profile with a
deflation yield point that is above the target operating pressure
of the pump. The additional thickness (>0.100'') and choice of
material (NuSil 4025A) in the inflatable tube provides an extended
range of Hooke's law response which is important in providing a
uniform flow rate--particularly at low volumes associated with
depletion of the pump contents. Normally, the silicone elastomer
(even NuSil 4025A) is non-Hookean as elasticity is stress dependent
which can readily be seen in the other portions of the
inflation-deflation profile.
[0078] While various patents have been incorporated herein by
reference, to the extent there is any inconsistency between
incorporated material and that of the written specification, the
written specification shall control. In addition, while the
disclosure has been described in detail with respect to specific
embodiments thereof, it will be apparent to those skilled in the
art that various alterations, modifications and other changes may
be made to the disclosure without departing from the spirit and
scope of the present disclosure. It is therefore intended that the
claims cover all such modifications, alterations and other changes
encompassed by the appended claims.
* * * * *