U.S. patent application number 11/153667 was filed with the patent office on 2006-12-21 for tourniquet cuff with improved pneumatic passageway.
This patent application is currently assigned to Western Clinical Engineering Ltd.. Invention is credited to Kenneth L. Glinz, Kevin B. Inkpen, Michael Jameson, James A. McEwen.
Application Number | 20060287672 11/153667 |
Document ID | / |
Family ID | 37531907 |
Filed Date | 2006-12-21 |
United States Patent
Application |
20060287672 |
Kind Code |
A1 |
McEwen; James A. ; et
al. |
December 21, 2006 |
Tourniquet cuff with improved pneumatic passageway
Abstract
A tourniquet cuff has minimal flow restrictions within its
pneumatic passageway under normal operating conditions, has a
substantially reduced likelihood of partial or complete
obstructions or interruptions of the pneumatic passageway under
foreseeable operating conditions, can indicate exposure of the cuff
to external agents that are capable of affecting the integrity of
the pneumatic passageway before use, and can be manufactured
economically.
Inventors: |
McEwen; James A.;
(Vancouver, CA) ; Glinz; Kenneth L.; (Richmond,
CA) ; Inkpen; Kevin B.; (Vancouver, CA) ;
Jameson; Michael; (North Vancouver, CA) |
Correspondence
Address: |
PATRICK W. HUGHEY
P.O. BOX 6553
PORTLAND
OR
97228
US
|
Assignee: |
Western Clinical Engineering
Ltd.
|
Family ID: |
37531907 |
Appl. No.: |
11/153667 |
Filed: |
June 15, 2005 |
Current U.S.
Class: |
606/202 |
Current CPC
Class: |
A61B 2017/00955
20130101; A61B 2090/0807 20160201; A61B 17/135 20130101 |
Class at
Publication: |
606/202 |
International
Class: |
A61B 17/00 20060101
A61B017/00 |
Claims
1. A tourniquet cuff comprising: an inflatable bladder having a
width dimension at a port location and a length dimension
sufficient for encircling a patient's limb at a desired location; a
port attached to the bladder at the port location and releasably
connectable to a tourniquet instrument, wherein the port includes a
pneumatic passageway that enables the inflatable bladder to
communicate pneumatically with the connected tourniquet instrument;
and an indicator applied to the cuff and reactive to an agent that
is capable of affecting the integrity of the pneumatic passageway
and for producing an indication if the agent reaches a
predetermined level.
2. The apparatus as described in claim 1 wherein the agent to which
the indicator reacts is a predetermined sterilizing agent and
wherein the indication is a change of color.
3. The apparatus as described in claim 1 wherein the indication is
remotely detectable by a tourniquet instrument.
4. The apparatus as described in claim 1 wherein the indicator is
carried on the port.
5. The apparatus as described in claim 1 wherein the port is formed
from a blend of thermoplastic material and the indicator.
6. The apparatus as described in claim 1 wherein the indication is
perceptible by a user.
7. The apparatus as described in claim 1 wherein the agent to which
the indicator reacts is water.
8. The apparatus as described in claim 1 wherein the agent to which
the indicator reacts is exposure to a temperature above a
predetermined level.
9. The apparatus as described in claim 1 wherein the agent is
capable of affecting the integrity of the inflatable bladder.
10. A tourniquet cuff having an improved pneumatic passageway,
comprising: an inflatable bladder having a bladder length
sufficient for encircling a patient's limb at a desired location,
port tubing communicating pneumatically with the inflatable bladder
and having a port tubing end, a port tubing length and a
substantially cylindrical outer surface that contains a pneumatic
passageway of predetermined cross-sectional area along the port
tubing length and through the port tubing-end, and a port connector
configured for establishing a pneumatic connection between the port
tubing and a tourniquet instrument, wherein the pneumatic
connection established by the port connector has a cross-sectional
area that is not less than the predetermined cross-sectional area
of the pneumatic passageway.
11. The apparatus as described in claim 10 wherein the port
connector receives the port tubing end and wherein the connector is
attached to the outer surface of the port tubing near the port
tubing end by an attachment means having a strength sufficient to
maintain the attachment to the outer surface in the presence of a
force along the port tubing length in a direction away from the
connector that is greater than a maximum force anticipated during
surgical use.
12. The apparatus as described in claim 10 wherein the port
connector is a predetermined shape formed on the outer surface of
the port tubing near the port tubing end and wherein the shape is
adapted to be received by a tourniquet instrument connector of the
tourniquet instrument to establish the pneumatic connection.
13. A tourniquet cuff having an improved pneumatic passageway,
comprising: an inflatable bladder having a bladder width and having
a bladder length sufficient for encircling a patient's limb at a
desired location, a port communicating pneumatically with the
bladder and including port tubing, wherein the port tubing is
formed of thermoplastic material having a substantially cylindrical
outer surface, a port tubing length greater than the bladder width,
a bladder end and a port tubing end, wherein the port tubing
contains a pneumatic passageway between the bladder end and the
port tubing end, and wherein the passageway has a predetermined
non-circular cross-sectional shape.
14. The apparatus as described in claim 13 wherein the port tubing
includes a ridge adjacent to the pneumatic passageway that extends
from the bladder end to the port tubing end.
15. The apparatus as described in claim 13 wherein the port tubing
includes a plurality of ridges adjacent to the pneumatic passageway
that extend from the bladder end to the port tubing end.
16. The apparatus as described in claim 13 and including a port
connector that is non-releasably bonded to the outer surface of the
port tubing near the port tubing end and wherein the connector is
adapted for connection to a tourniquet instrument to establish a
gas-tight passageway between the bladder and the instrument.
17. A tourniquet cuff having an improved pneumatic passageway,
comprising: a first layer having a width dimension, a length
dimension and a sealing surface, a second layer having a width
dimension, a length dimension and a sealing surface positioned
against the sealing surface of the first layer and sealed around a
perimeter to form an inflatable bladder within the perimeter, a
port having a bladder sealing flange sealed to the first layer
sealing surface around the flange to establish a pneumatic
passageway from a distal port end outside the first layer through
the port and into the bladder along a channel formed in the
flange.
18. The apparatus as described in claim 17 and including a
plurality of parallel channels formed in the flange to establish a
plurality of pneumatic passageways through the flange.
19. The apparatus as described in claim 17 wherein the port further
contains a normal channel of predetermined cross-sectional area
extending through the flange and into the bladder in a direction
normal to the first layer and wherein the pneumatic passageway into
the bladder further includes the normal channel when the second
layer is not in contact with the flange.
20. A tourniquet cuff having an improved pneumatic passageway,
comprising: a first layer of flexible thermoplastic material having
a first layer sealing surface, a second layer of flexible
thermoplastic material having a second layer sealing surface facing
the first layer sealing surface, a perimeter seal establishing a
gas-tight seal between the first layer sealing surface and the
second layer sealing surface around a predetermined perimeter to
form an inflatable bladder within the perimeter seal, wherein the
perimeter seal includes a bead protruding into the inflatable
bladder and having a bead thickness greater than a predetermined
bead thickness to separate the first sealing surface from the
second sealing surface, thereby establishing a bladder pneumatic
passageway near the bead.
21. The apparatus as described in claim 20 and including a port
having a bladder sealing flange of predetermined thickness and
predetermined circumference sealed to the first layer sealing
surface around the circumference and passing through the first
layer to establish a port passageway from a distal port end outside
the first layer through the port and into the bladder near the edge
of the bladder sealing flange along a channel formed in the port
seal flange.
Description
FIELD OF THE INVENTION
[0001] This invention pertains to pneumatic tourniquet cuffs
commonly used for stopping arterial blood flow into a portion of a
surgical patient's limb to facilitate the performance of a surgical
procedure, and for facilitating intravenous regional
anesthesia.
BACKGROUND OF THE INVENTION
[0002] A typical surgical tourniquet system of the prior art
includes a tourniquet cuff for encircling a patient's limb at a
desired location and a tourniquet instrument that includes flexible
instrument tubing for connecting to the tourniquet cuff. The
tourniquet cuff typically includes an inflatable portion, and the
inflatable portion of the cuff is typically connected through a
cuff port having a port connector to the flexible instrument tubing
of the tourniquet instrument, thereby establishing a pneumatic
passageway from the tourniquet instrument through the instrument
tubing and the cuff port into the inflatable portion of the cuff.
In some prior-art systems, the tourniquet instrument includes a
pressure transducer to sense the pressure of gas at the instrument
end of the pneumatic passageway and to enable the sensed pressure
to be displayed for surgical staff. Some prior-art tourniquet
instruments include a pressure regulator to increase and decrease
the pressure of gas in the pneumatic passageway, and to maintain
the pressure in the inflatable portion of the cuff at a pressure
above a minimum pressure required to stop arterial blood flow past
the cuff during a time period suitably long for the performance of
a surgical procedure. Many types of pneumatic surgical tourniquet
systems, including tourniquet cuffs and tourniquet instruments,
have been described in the prior art, such as those described by
McEwen in U.S. Pat. No. 4,469,099, U.S. Pat. No. 4,479,494, U.S.
Pat. No. 5,439,477 and by McEwen and Jameson in U.S. Pat. No.
5,556,415 and No. 5,855,589.
[0003] Some tourniquet cuffs of the prior art have only a single
port for connection to the tourniquet instrument and thus establish
only a single pneumatic passageway between a tourniquet instrument
and the inflatable portion of such cuffs. The pressure in the
inflatable portion of such single-port tourniquet cuffs must be
sensed indirectly from the tourniquet instrument, through the same
pneumatic passageway that is used by the tourniquet instrument to
increase, decrease and regulate cuff pressure during surgery. The
flow resistance of the pneumatic passageway affects the accuracy
and speed of regulation of pressure within the inflatable portion
of such single-port tourniquet cuffs as well as the accuracy of the
indirectly sensed tourniquet cuff pressure.
[0004] Other tourniquet cuffs of the prior art have dual ports to
establish two separate pneumatic passageways between the tourniquet
instrument and the inflatable portion of the cuff, to achieve
increased safety and performance by enabling the tourniquet
instrument to provide surgical staff with a more accurate
indication of cuff pressure and by enabling the tourniquet
instrument to increase the speed and accuracy of cuff pressure
regulation. Representative dual-port tourniquet cuffs of the prior
are described in U.S. Pat. No. 4,635,635, U.S. Pat. No. 5,454,831,
U.S. Pat. No. 5,439,477, U.S. Pat. No. 5,741,295 and U.S. Pat. No.
5,649,954. In one dual-port tourniquet system of the prior art,
described in U.S. Pat. No. 4,469,099, the pneumatic pressure
regulation elements within the tourniquet instrument communicate
with the inflatable portion of the tourniquet cuff through one
pneumatic passageway of the tourniquet cuff, and a pressure sensor
within the tourniquet instrument communicates pneumatically with
the inflatable portion of the cuff through a separate pneumatic
passageway of the cuff.
[0005] With both single and dual-port tourniquet systems, the speed
and accuracy of pressure regulation and indication are improved if
flow restrictions in the pneumatic passageway are minimized.
Typical port connectors of the prior art have a male barbed
connection portion which fits inside the pneumatic passageway of
the port, creating a region of reduced pneumatic flow area and
increasing flow resistance between the cuff and the tourniquet
instrument.
[0006] One hazard associated with all pneumatic tourniquet cuffs of
the prior art is the obstruction of the pneumatic passageway within
the cuff. For example, in a single-port tourniquet cuff, a complete
obstruction within the pneumatic passageway may allow the actual
pressure in the inflatable portion of the cuff to decrease
substantially below the desired tourniquet pressure to a level
where the cuff may be completely depressurized, or to increase
substantially above the desired tourniquet pressure, without any
indication to the surgical staff. In effect, the monitoring and
regulation of cuff pressure by a prior-art tourniquet instrument
stops at the location of the obstruction. As another example, a
complete obstruction within a region of the inflatable portion of
the cuff may isolate all or part of the inflatable portion and thus
may prevent the pressure throughout the entire inflatable portion
of the cuff from being sensed and regulated near the desired
pressure by the tourniquet instrument. Any isolated region may be
hazardous, either by permitting arterial blood to flow into the
limb past a region of lower cuff pressure or by requiring surgical
staff to set the tourniquet instrument to an unnecessarily high
pressure to stop blood flow past the cuff. Also, any complete
obstruction of the pneumatic passageway within a tourniquet cuff of
the prior art may render ineffective any audio-visual safety alarms
of a connected prior-art tourniquet instrument intended to warn of
hazardous over-pressurization or under-pressurization of the cuff,
such as the safety alarms described by McEwen in U.S. Pat. No.
4,469,099.
[0007] Another hazard associated with tourniquet cuffs of the prior
art is partial obstruction of the pneumatic passageway. A partial
obstruction of the pneumatic passageway at the port connector, or
elsewhere within the port or inflatable portion of a prior-art cuff
may increase the pneumatic flow resistance at the partial
obstruction, and thus may affect the ability of a connected
tourniquet instrument to rapidly and accurately regulate pressure
past the partial obstruction and throughout the inflatable portion
of the tourniquet cuff. Increased flow resistance from a partial
obstruction may also reduce the ability of a connected tourniquet
instrument to accurately and rapidly indicate changes of the
pressure in the tourniquet cuff to surgical staff. Further, a
partial obstruction of the pneumatic passageway within a region of
the inflatable portion of the cuff may affect the ability of the
tourniquet instrument to uniformly regulate pressure throughout the
entire inflatable portion of the cuff.
[0008] In addition to the hazards of complete and partial
obstructions that may affect the integrity of the pneumatic
passageway, another hazard associated with prior-art cuffs is the
interruption of the passageway due to unanticipated detachment of
the port connector from the tourniquet instrument, or detachment of
the port connector from the port, thus separating the inflatable
portion of the tourniquet cuff from the tourniquet instrument. A
related hazard is a leak at the port connector that is sufficiently
large to prevent a connected tourniquet instrument from maintaining
cuff pressure near the desired pressure. Such a large leak may
result, for example, from deterioration or deformation of the
connector of a single-use disposable tourniquet cuff as a result of
reprocessing and reuse of the disposable tourniquet cuff in
multiple surgical procedures in a manner neither intended nor
anticipated by the manufacturer.
[0009] Many disposable tourniquet cuffs of the prior art are
designed to be used in only one single surgical procedure and then
discarded. Many such disposable tourniquet cuffs are sterilized at
time of manufacture and supplied to users as sterile products,
because such cuffs are typically intended to be suitable for use
within sterile surgical fields. As a result, the design
characteristics of such prior-art cuffs are intended to allow them
to be applied and used safely and reliably within a sterile
surgical field during one surgical procedure, and to be discarded
cost-effectively after that procedure. For example, some disposable
tourniquet cuffs of the prior art have a port that includes a very
flexible thermoplastic tubing portion having a length sufficient to
allow a user to easily bend the port away from the surgical site
and position the port connector beyond the sterile surgical field.
Although such-long and flexible port tubing facilitates connection
of the port to non-sterile instrument tubing away from the sterile
surgical field, it may also increase the possibility of partial or
complete obstruction of the pneumatic passageway within the port,
for example by accidental kinking, bending, or pinching of the
tubing. The various materials and components from which such
prior-art disposable tourniquet cuffs are assembled are chosen to
be sufficiently inexpensive to allow the cuff to be economically
discarded after a single use, and also to be capable of
sterilization by exposure to a specific sterilizing agent within a
specific sterilizing process determined by the manufacturer, with
no significant deterioration or change of properties that would
impair the safety or performance of the cuffs after such
sterilization.
[0010] Efforts have been made to reprocess and reuse tourniquet
cuffs of the prior art that were originally supplied by their
manufacturers as sterile, single-use products. Reprocessing efforts
typically involve saving rather than discarding a disposable
tourniquet cuff after surgery, visually examining the cuff to
identify any obvious deterioration that might suggest reprocessing
is not appropriate, attempting to remove any blood and other
surgical debris by washing the cuffs with water combined with any
of a variety of detergents or other cleaning liquids, in some cases
conducting some functional tests of the cuff, re-packaging the cuff
and then sterilizing the re-packaged cuff by exposing it to a
sterilization agent within a sterilization process that may be
different from that determined by the original manufacturer to be
safe and effective. Reprocessing of disposable tourniquet cuffs may
be carried out within hospitals or surgery centers or by
third-party reprocessors, and the quality and methods of
reprocessing are highly variable.
[0011] Reprocessing, cleaning and re-sterilizing of disposable
tourniquet cuffs may result in hazards for the surgical patients on
whom such cuffs are subsequently used. The hazard arises from the
use of any of a variety of chemical or physical agents that are
attendant with the reprocessing, cleaning or re-sterilizing
processes. For example, exposure of a cuff to liquids during
cleaning may allow the liquids to enter the pneumatic passageway of
the cuff, where they may remain to partially or complete obstruct
the pneumatic passageway of the cuff within the port or inflatable
portion. Water remaining within the pneumatic passageway after
cleaning may subsequently react chemically with ethylene oxide, a
sterilizing agent commonly used in reprocessing, to form ethylene
glycol, a sticky substance that may completely or partially block
the pneumatic passageway. Exposure of prior-art cuffs to
sterilizing agents different than the sterilizing agent employed at
the time of manufacture may produce a change and deterioration in
the properties of some cuff materials and components, for example
due to a chemical reaction or exposure to radiation. Exposure of a
prior-art cuff containing flexible thermoplastic materials to an
elevated temperature during cleaning or sterilization by known
prior-art processes may soften thermoplastic materials and
components, increasing the likelihood of hazardous deformation of
some components. For example, an elevated temperature during
reprocessing may result in substantial deformation of the
thermoplastic stiffener included in some prior-art cuffs, thus
impairing the application of pressure by such a cuff to an
underlying limb upon subsequent use in surgery. Also, an elevated
temperature during reprocessing may deform the thermoplastic
connectors of some prior-art cuffs, or may weaken the retention
force of typical thermoplastic barb-type port connectors, so that
such connectors cannot establish or reliably maintain a gas-tight
passageway between the tourniquet cuff and tourniquet instrument
upon reuse. An elevated temperature associated with cleaning or
re-sterilization increases the likelihood that the pneumatic
passageway within the cuff may become partially or completely
obstructed, as described above, as a result of such reprocessing.
Repeated cleaning, re-sterilization and reuse of a disposable
tourniquet cuff in multiple surgical procedures may progressively
increase the hazard for the surgical patients on whom the cuff is
used.
[0012] There is a need for a tourniquet cuff that has minimal flow
restrictions within its pneumatic passageway under normal operating
conditions, that has a substantially reduced likelihood of partial
or complete obstructions or interruptions of the pneumatic
passageway under foreseeable operating conditions, that can
indicate exposure of the cuff to one or more external agents that
are capable of affecting the integrity of the pneumatic passageway
before use, and that can be manufactured economically. The present
invention addresses this need.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a pictorial representation of the preferred
embodiment in a surgical application.
[0014] FIG. 2 shows the cuff portion of the preferred
embodiment.
[0015] 3a is a section taken from FIG. 2, with the uninflated cuff
applied to the patient's limb as shown in FIG. 1.
[0016] FIG. 3b is a section taken from FIG. 2, with the cuff
applied to the patient's limb and inflated.
[0017] FIG. 4 is a view looking on the bottom surface of the
bladder sealing flange.
[0018] FIG. 5 is a section taken from FIG. 4.
[0019] FIG. 6a is a section taken from FIG. 2, showing the
preferred embodiment.
[0020] FIG. 7a is a detail view of the areas indicated in FIG. 3a
and FIG. 3b, showing the preferred embodiment.
[0021] FIG. 7b is a detail view of the areas indicated in FIG. 3a
and FIG. 3b, showing an alternate embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] FIG. 1 is a pictorial representation of the preferred
embodiment in a surgical application, showing the tourniquet cuff
10 applied to patient limb 12 and pneumatically connectable to
tourniquet instrument 14. Cuff 10 includes cuff port 16, which
comprises bladder sealing flange 18, port tubing 20, and port
connector 22. In the preferred embodiment shown, cuff 10 is a
single port cuff, where cuff port 16 provides a single pneumatic
passageway to the inflatable portion of cuff 10. Those skilled in
the art will appreciate that the features described in the
preferred embodiment may also be applied to tourniquet cuffs having
more than one port, such as those described by U.S. Pat. No.
4,469,099, U.S. Pat. No. 4,479,494, and U.S. Pat. No. 5,254,087.
Cuff port 16 is pneumatically connected to tourniquet instrument 14
via instrument connector 24 and instrument tubing 26. In the
preferred embodiment cuff port 16 is of sufficient length to allow
pneumatic connection between cuff 10 and instrument 14 to be made
outside a sterile surgical field. Port connector 22 is a locking
connector (based on the connector of the tourniquet cuff described
by McEwen in U.S. Pat. No. 5,649,954 and similar in some design
aspects to connector DSM2202, Colder Products Company, St. Paul,
Minn.) which allows cuff port 16 to form a releasable pneumatic
connection with instrument connector 24.
[0023] As described below, cuff 10 is constructed of materials that
are appropriate for a single-use sterile disposable tourniquet
cuff. To permit cuff 10 to be used in a sterile surgical field,
cuff 10 is sterilized at time of manufacture by exposure to a
sterilizing agent within a sterilizing process determined to be
safe and effective. To prevent deterioration of the cuff, and to
maintain the integrity of the pneumatic passageways within cuff 10,
a sterilization agent and process that will not harm the materials
or components of cuff 10 is selected by the manufacturer. In the
preferred embodiment cuff 10 is sterilized by exposure to gamma
radiation or electron beam radiation.
[0024] The cost of materials is an important consideration in the
manufacture of tourniquet cuffs intended for a single use and then
disposal. To minimize the cost of materials and assembly of cuff
10, materials are selected which are not intended to withstand
exposure to subsequent sterilization and cleaning processes. The
subsequent sterilization or cleaning of cuff 10 by agents and
processes commonly used in health care facilities, such as ethylene
oxide gas sterilization, hydrogen peroxide gas sterilization, high
temperature and pressure steam sterilization, sterilization by
other chemical agents, and pasteurization, are all capable of
adversely affecting the integrity of the pneumatic passageways of
cuff 10. As described further below, cuff 10 includes one or more
components that act as visual indicators to warn a user that cuff
10 has been subjected to a subsequent sterilization or cleaning
process capable of adversely affecting cuff 10 and that cuff 10 may
no longer be safe to use.
[0025] FIG. 2 shows the cuff 10 of the preferred embodiment, which
is similar in design and construction to the cuffs described by
McEwen in U.S. Pat. No. 5,741,295, U.S. Pat. No. 5,649,954, U.S.
Pat. No. 5,484,831 and by Robinette-Lehman in U.S. Pat. No.
4,635,635. In the preferred embodiment shown, cuff 10 is
rectangular with a length sufficient to encircle an adult arm as
shown in FIG. 1. Those skilled in the art will appreciate that the
features described in the preferred embodiment may also be
incorporated in cuffs of various sizes and shapes, such as those
described by McEwen in U.S. Pat. No. 5,649,954. In addition to cuff
port 16, cuff 10 comprises tie ribbon 28, loop material 30, edge
trim 32, sewn joint 34, and hook material 36. In use, cuff 10 is
wrapped snugly around the limb 12 (see FIG. 1) and secured
circumferentially around the limb when the user engages hook
material 36 to loop material 30. Tie ribbon 28 is a soft fabric
ribbon material (Grosgrain 5/8'' wide, Dynatex Textiles Inc.,
Toronto, Ontario, Canada) and allows the user to pull cuff 10 snug
around the limb. When cuff 10 is in position and secured
circumferentially around the limb, the user ties tie ribbon 28 as
shown in FIG. 1 to help prevent the cuff from sliding proximally or
distally on the limb when inflated. Edge trim 32 is made of similar
material to tie ribbon 28 and helps prevent chafing of the
patient's limb by the edges of cuff 10.
[0026] FIG. 3a is a section taken from FIG. 2, however with cuff 10
applied to the limb 12 (as shown in FIG. 1) and cuff 10 uninflated.
Top layer 38 and bottom layer 40 are made of woven nylon cloth
coated with thermoplastic material (for example, 200 Denier nylon
cloth coated in thermoplastic polyurethane 0.006'' thick) on the
surfaces that face middle layer 42. Middle layer 42 is made of
thermoplastic sheet material (for example, 0.020'' thick
polyurethane). Stiffener 44 is made of plastic sheet cut to a
rectangular shape fitting within the perimeter of cuff 10. The
stiffener 44 has greater stiffness than layers 38, 40, and 42 but
is flexible enough to be wrapped around the limb (for example
0.020'' thick polyethylene sheet). Top layer 38, middle layer 42,
and bottom layer 40 are joined around a continuous perimeter within
the perimeter of cuff 10 at bladder seal 46, thereby forming
inflatable bladder 48 between middle layer 42 and bottom layer 40
and enclosing thermoplastic stiffener 44 between top layer 38 and
middle layer 42. Bladder 48 therefore has a width at the port
location as shown in FIG. 3a, a typical value being 3.5 inches, and
a length extending along the length of the cuff (see FIG. 2) and
sufficient to encircle the limb. When secured circumferentially
around the limb as shown in FIG. 1, stiffener 44 helps direct the
expansion of inflatable bladder 48 radially inwards towards the
limb upon inflation of the cuff. The stiffener thus provides
uniformly distributed pressure onto limb 12.
[0027] Bladder seal 46 is formed by a heat and pressure joining
process, typically radio-frequency welding using a selected sealing
die. The heat of the joining process is selected to temporarily
melt a portion of the thermoplastic materials in layers 38, 40, and
42, causing them to fuse together in the area of bladder seal 46.
The pressure of the joining process in combination with the shape
of the sealing die is selected to squeeze a predetermined portion
of the melted thermoplastic materials in layers 38, 40, and 42 out
of the area of bladder seal 46, forming a continuous bead 50 along
the perimeter of inflatable bladder 48. When the joining process is
complete, bead 50 solidifies back to the original rigidity of the
thermoplastic materials in layers 38, 40, and 42 and has thickness
51 (shown in FIG. 3b only for clarity). Thickness 51 is
proportional to the selected amount of thermoplastic material
squeezed out during the formation of bladder seal 46, and is
selected to be large enough to form and maintain bladder pneumatic
passageway 52 when bottom layer 40 is compressed against middle
layer 42 during certain conditions of use, which are described in
more detail below.
[0028] Cuff port 16 of cuff 10 comprises port connector 22, port
tubing 20, and bladder sealing flange 18, which are permanently
joined together with pneumatically sealed joints to form port
tubing pneumatic passageway 54 and port connector pneumatic
passageway 55 (see FIG. 7a) which form a continuous pneumatic
passageway extending from distal port end 53 to inflatable bladder
48. Bladder sealing flange 18 has flange top surface 56 which is
permanently joined to middle layer 42 by a heat sealing process
similar to that used to form bladder seal 46 (as described above).
Bladder sealing flange 18 also has bottom surface 58. Port tubing
20 has a length between bladder end 59 and port connector 22, which
is at minimum greater than the bladder width at the port location,
and preferably 30 inches, which is sufficient to extend outside the
sterile surgical field. Bladder sealing flange 18 forms a portion
of pneumatic passageway 54 extending from port tubing bladder end
59 and formed to enter inflatable bladder 48 in a direction normal
to top surface 56 and bottom surface 58 of bladder sealing flange
18, and thereby normal to the area of middle layer 42 around
bladder sealing flange 18.
[0029] FIG. 3b is a section taken from FIG. 2, however with cuff 10
applied to the limb 12 (as shown in FIG. 1) and cuff 10 inflated.
Inflatable bladder 48 is shown expanded radially inwards towards
the limb.
[0030] FIG. 4 is a view looking on bottom surface 58 of bladder
sealing flange 18. Bladder sealing flange 18 is made of
thermoplastic polyurethane by injection molding (in a similar
manner to existing sealing flanges such as 167ACU-BK, Halkey
Roberts Corp., St. Petersburg, Fla. which are currently used in
tourniquet cuffs). A plurality of channels 60 are formed in surface
58 extending from the outer perimeter of flange 18 to port
pneumatic passageway 54.
[0031] FIG. 5 is a section taken from FIG. 4, showing a typical
channel 60 formed in the area between flange bottom surface 58 and
flange top surface 56. Because bladder sealing flange 18 must be
heat sealed to middle layer 42, channels 60 may be formed in to
surface 58 by correspondingly shaped ridges on the sealing die and
therefore are formed during the heat sealing process of bladder
sealing flange 18 to middle layer 42 with no additional per item
cost compared to the typical prior-art tourniquet cuffs.
[0032] Referring to FIGS. 1, 3a, 4, and 5, when port connector 22
is connected to instrument 14, a pneumatic passageway is
established from instrument 14 through port pneumatic passageway 54
(formed by the openings in port connector 22, port tubing 20, and
bladder sealing flange 18), channels 60 in bladder sealing flange
bottom surface 58 into inflatable bladder 48. Bead 50 acts to hold
open the bladder 48 near the bladder seal 46 thereby establishing a
bladder pneumatic passageway 52 around the perimeter of inflatable
bladder 48, allowing pneumatic communication throughout the
bladder.
[0033] If bladder sealing flange 18 is compressed against limb 12
(for example if the flange area of the cuff is lying between the
limb and the operating room table or bolster on which the limb is
resting, or cuff 10 is applied to limb 12 too tightly), bottom
layer 40 may be pressed against flange bottom surface 58 as shown
in FIG. 3a. On bladder sealing flanges typically used in tourniquet
cuffs of the prior art (for example see 167ACU-BK, Halkey Roberts
Corp., St. Petersburg, Fla.), surface 58 is flat and smooth. Using
prior-art flanges in the condition shown in FIG. 3a, pneumatic
communication between inflatable bladder 48 and port pneumatic
passageway 54 is closed off or restricted. In the current
invention, however, channels 60 form a plurality of pneumatic
passageways between inflatable bladder 48 and port pneumatic
passageway 54 in the area between flange bottom surface 58 and
flange top surface 56, which remain open when bottom layer 40 is
compressed against flange bottom surface 58.
[0034] Furthermore, if any area of the cuff containing inflatable
bladder 48 is compressed against the limb, bottom layer 40 may be
pressed against middle layer 42 in some areas (as shown in FIG. 3a)
which may restrict or close pneumatic communication between
different regions of inflatable bladder 48. Bead 50 separates
middle layer 42 and bottom layer 40, thereby establishing bladder
pneumatic passageway 52 extending around the entire perimeter of
inflatable bladder 48 as noted above. The size of bead 50 is
selected such that bladder pneumatic passageway 52 is maintained
under the compression forces between bottom layer 40 and middle
layer 42 expected in surgical use, thereby maintaining pneumatic
communication among all regions of bladder 48.
[0035] In addition to the conditions described above which may
occur during the normal use of cuff 10, exposure of cuff 10 to an
elevated temperature or pressure, or exposure of cuff 10 to certain
chemicals, or a combination of these conditions may occur during
storage, shipping, or subsequent cleaning and sterilization
processes and may cause bottom layer 40 to adhere to flange bottom
surface 58 or areas of middle layer 42 by softening the
thermoplastic materials. If the materials adhere, pneumatic
passageways will nonetheless be maintained by bead 50 and channels
60.
[0036] FIG. 6a is a section taken from FIG. 2, showing the
cross-sectional profile of port tubing 20 of cuff port 16,
extending from bladder end 59 (see FIGS. 3a and 3b) to port tubing
end 61 (see FIG. 7a). Port tubing 20 is formed by an extrusion
process and is made of a blend of thermoplastic polyurethane and
sterilization indicator formulated to change color when exposed to
certain agents that, as noted above, may have a deleterious effect
on the integrity of the pneumatic passageway. In this embodiment,
the sterilization indicator does not react to change color during
the initial sterilization of cuff 10 by gamma or electron beam
radiation at time of manufacture. In the preferred embodiment, the
thermoplastic material is formulated to undergo a distinct and
permanent color change upon exposure to predetermined minimum
levels of one or more selected sterilizing agents different than
the agent employed at time of manufacture and typical of those
commonly used within health care facilities and by reprocessors.
Ethylene oxide gas is one such secondary sterilizing agent that may
be used in a reprocessing sterilization process. Other agents are
hydrogen peroxide gas, high temperature steam, and other chemical
sterilizing agents. This color change occurs over the length of
port tubing 20 and is visually perceptible by the user to indicate
that cuff 10 has undergone a subsequent sterilization capable of
affecting the pneumatic communication described above and shown in
FIG. 3a. To enhance the appearance of the color change that takes
place within port tubing 20 upon exposure to a subsequent
sterilizing process, a portion of port tubing 20 may be marked with
a substance that does not change color upon exposure to the
sterilization process. For example, port tubing 20 may be formed
from a thermoplastic material that normally has a clear color and
changes to a brown color upon exposure to the ethylene oxide
sterilization process. Port tubing 20 may also be marked with a
white stripe which runs the length of port tubing 20. When port
tubing 20 is exposed to the sterilization process the printed white
stripe provides visual contrast to the underlying, brown-colored
tubing.
[0037] In the preferred embodiment the secondary sterilization
indicator described above is formulated from a color-forming
compound pre-selected to react with a predetermined minimum level
of ethylene oxide in a secondary sterilization process.
Color-forming compounds such as 4-(hydrazinocarbonyl) pyridine,
4-nitrobenzylpyridine, or other pyridines that react with ethylene
oxide may be used alone or in combination to produce a
non-reversible color change reaction upon exposure to ethylene
oxide gas. The color-forming compound may also include catalysts
that further promote the color change reaction. To increase
utility, the secondary sterilization indicator of the preferred
embodiment may be mixed with additional color-forming compounds
known in the art that react to change color in the presence of
hydrogen peroxide gas or high temperature steam. The sterilization
indicator may also include other non-reactive pigments pre-selected
to enhance the visibility of the color-forming compound in its
reacted state, thereby making a color change more visually
perceptible by a user.
[0038] To further indicate to a user that cuff 10 has been exposed
to a second sterilization agent within a sterilization process
different than that used at time of manufacture, the secondary
sterilization indicator may be carried on another component of cuff
10, such as a label attached to cuff 10, or the surface of port
tubing 20 or the surface of tie ribbon 28. For example, tie ribbon
28 may be selected to be initially white in color and upon the
subsequent sterilization of cuff 10 by ethylene oxide sterilization
change color to brown.
[0039] To indicate exposure of cuff 10 to a physical agent such as
heat at a temperature that is capable of deforming, obstructing or
otherwise adversely affecting the integrity of pneumatic
passageways 54 or 55 or portions of inflatable bladder 48, an
irreversible thermochromic indicator compound is carried on a
selected surface of cuff 10, for example a surface of port tubing
20. Thermochromic indicators are known in the art and may be
formulated to react by irreversibly changing color at a
predetermined temperature to indicate that exposure to the
predetermined temperature has taken place. The preferred
thermochromic indicator is unaffected by the initial sterilization
of cuff 10 at time of manufacture. By carrying the preferred
thermochromic indicator on a selected surface of cuff 10, an
indication perceptible by a user of cuff 10 is produced when cuff
10 has been exposed to a potentially damaging and hazardous
temperature. Alternately, exposure of cuff 10 to an elevated
temperature that is potentially damaging and hazardous may be
indicated by a temperature-indicating compound that liquefies at
the predetermined temperature. For example, a
temperature-indicating compound (Tempilaq G TL0175, Tempil Inc.,
South Plainfield, N.J., which is applied like paint, re-liquifies
upon reaching the predetermined temperature, then re-solidifies
upon cooling below the predetermined temperature) may be carried on
port tubing 20. Port tubing 20 of the preferred embodiment is made
of a transparent thermoplastic polyurethane having a clear color
and thus a distinct pattern of temperature-indicating compound
having a different color may be applied or printed in a particular
pattern along inner surface 64 so that, if inner surface 64 reaches
or exceeds the predetermined temperature, the compound reacts by
liquefying and, causing the pattern to spread out and change to a
colored smear. This distinct change of the printed pattern carried
on inner surface 64 provides a visual indication perceptible by a
user cuff 10 has been exposed to an elevated temperature at least
equal to the predetermined temperature and that cuff 10 thus may be
unsafe to use.
[0040] A water-indicating compound (such as a water-soluble ink)
may be formed into a printed pattern carried on a selected surface
of cuff 10, as described in the preceding paragraph for an elevated
temperature-indicating compound. Introduction of water or other
liquid agents into pneumatic passageway 54 during any reprocessing
could partially or completely obstruct pneumatic passageway 54.
Moreover, the water could indirectly obstruct the passageway by
reacting chemically with secondary sterilizing agents such as
ethylene oxide. A water-soluble pattern of colored ink carried on
inner surface 64 of port tubing 20 would react to and indicate the
introduction of water into pneumatic passageway 54 by changing the
pattern, and the change would be readily perceptible by a user.
[0041] It will be appreciated that the indicating compounds
described above for water, temperature and secondary sterilizing
agents may be used alone or in combination, and carried on selected
surfaces of cuff 10 or combined when forming components of cuff 10,
to indicate to a user that cuff 10 has been subjected to a
subsequent sterilization or cleaning process capable of adversely
affecting cuff 10 and that cuff 10 may no longer be safe to
use.
[0042] Referring again to the cross-sectional profile of port
tubing 20 shown in FIG. 6a, port tubing 20 has outer surface 62
having a circular cross-sectional shape, inner surface 64, and
ridge 66. Outer surface 62, inner surface 64, and ridge 66 together
form wall 68 having a non-uniform thickness, and pneumatic
passageway 54 which has a non-circular cross-sectional shape. Ridge
66 protrudes into pneumatic passageway 54 and thereby prevents
complete occlusion of pneumatic passageway 54 if port tubing 20 is
kinked or flattened. In contrast, existing flexible tubing
typically used in tourniquet cuffs has inner and outer surfaces of
a circular cross-sectional shape, and do not have ridge 66. Due to
the stiffening properties of the cross-sectional shape shown in
FIG. 6a the cross-sectional area of wall 68 is selected to be
similar or less than that of existing flexible tubing currently
used in disposable tourniquet cuffs, resulting in an equivalent
volume of material per unit length, and the constant
cross-sectional shape of port tubing 20 allows manufacture by well
proven and cost -effective extrusion methods as used for prior-art
tubing, resulting in a cost of manufacture of port tubing 20 that
is similar to that of the prior-art tubing.
[0043] FIG. 6b is a section taken from FIG. 2, showing an alternate
cross-sectional profile of port tubing 20 of cuff port 16, having a
plurality of ridges 66 providing increased resistance to occlusion
compared to the cross section shown in FIG. 6a. Those skilled in
the art will recognize that the size, shape, and number of ridges
66 may be selected to provide an anti-occlusive effect for a
particular overall size and stiffness of port tubing 20, and
selected to minimize the required cross-sectional area of wall 68
and thereby minimize the cost of port tubing 20.
[0044] FIG. 7a is a detail view taken from FIGS. 3a and 3b, showing
the preferred embodiment. Port connector 22 is formed by an
injection molding process, like the process used to form connectors
of type DSM2202 (Colder Products Company, St. Paul, Minn.) that are
used in commercial tourniquet cuffs derived from the cuff described
by McEwen in U.S. Pat. No. 5,649,954. However, unlike these
prior-art connectors, port connector 22 is made of a blend of
thermoplastic polyethylene and sterilization indicator formulated
to change color when exposed to the predetermined conditions
described above for port tubing 20. The polyethylene component of
the material used to make port connector 22 is selected to have
similar stiffness, strength, sliding, and sealing properties to the
polyethylene material of the connectors in the McEwen '954 cuff and
of the DSM2202 connectors in related commercial cuffs of the prior
art, thereby ensuring compatibility with female connectors intended
for use with the DSM2202 connector. The secondary sterilization
indicator of unauthorized reprocessing is as described above for
port tubing 20. Alternatively or in addition, port connector 22 may
carry a temperature indicating compound on one or more selected
surfaces as described above for port tubing 20. Port connector 22
may also carry a water-indicating compound on one or more selected
surfaces, as described above for port tubing 20.
[0045] A change in the color of port connector 22 from a first
predetermined color to a second predetermined color as described
above provides an indication that is visually perceptible by a user
of cuff 10. Further, the above-described change of color of port
connector 22 can be remotely and automatically detected by
connected tourniquet instrument 14, for example by incorporating
the apparatus described by McEwen in U.S. Pat. No. 6,682,547 and
U.S. Patent Application No. 20030167070, both of which documents
are hereby incorporated by reference. In this regard, the
instrument is provided with a light emitter and light detector
(such as a photodiode) arranged so that changes in the color of the
port connector (or the color change of other part of the cuff that
is in the optic path between the emitter and detector) will
corresponding alter the light intensity reaching the detector so
that the output signal associated with the detector is indicative
of the color change, hence automatically indicating the exposure to
the agent that caused the color change.
[0046] Port connector 22 includes actuating flange 70, annular
groove 72, and deformable ring 74 as described by McEwen in U.S.
Pat. No. 5,649,954 and similar in design to the existing DSM2202
connector, thereby making port connector 22 compatible with female
connectors intended for use with the DSM2202 connector. However
while the prior-art connectors typically have a male barbed portion
that fits inside flexible plastic tubing having a circular inner
cross section, port connector 22 is adapted for easy assembly to
port tubing 20 that has inner surface 64 of a non-circular cross
section (see FIGS. 6a and 6b). Port connector 22 is joined to port
tubing 20 by sliding female cylindrical flange 76 over outer
surface 62 and bonding at the mating surface. This arrangement
forms port connector pneumatic passageway 55 extending from port
tubing end 61 to distal port end 53 and provides greater pneumatic
flow area compared to the existing DSM2202 connector by eliminating
the male barbed portion of the connector inside pneumatic
passageway 54 and allowing the cross-sectional area of the port
connector pneumatic passageway 55 to be equal to or greater than
that port tubing pneumatic passageway 54 of port tubing 20. This
greater flow area improves the speed of inflation and deflation of
cuff 10 and makes pneumatic passageways 54 and 55 less likely to
become occluded by kinking, compression, or debris. Furthermore
bonding port connector 22 to port tubing 20 on outer surface 62
increases bond area compared to the typical arrangement seen in the
prior art (inserting a male connection portion of the port
connector into the inner surface of the flexible plastic tubing),
which improves the strength and pneumatic sealing properties of the
bond. The volume of material in female cylindrical flange 76 is
similar to that of the male barbed portion of the existing DSM2202
connector, and the mold required to form female cylindrical flange
76 is simpler, so the cost of manufacture of port connector 22 is
similar to or less than that of the prior-art connector.
[0047] FIG. 7b is a detail view taken from FIGS. 3a and 3b, showing
an alternate embodiment in which port connector 22 (see FIG. 7a) is
integrated with port tubing 20 to reduce manufacturing cost. In
this embodiment, the end of port tubing 20 is formed to create
actuating flange 70, annular groove 72, and deformable ring 74. The
thermoplastic material is as described above for port connector 22
and undergoes a distinct color change upon exposure to
predetermined conditions. This alternate embodiment eliminates the
assembly and bonding of port connector 22 to port tubing 20 as
described in the preferred embodiment.
* * * * *