U.S. patent application number 15/633557 was filed with the patent office on 2017-10-19 for components for breathing circuits.
The applicant listed for this patent is Fisher & Paykel Healthcare Limited. Invention is credited to David Peter Baldwin, Gavin Walsh Millar, Kevin Blake Powell, Daniel John Smith.
Application Number | 20170296769 15/633557 |
Document ID | / |
Family ID | 26652172 |
Filed Date | 2017-10-19 |
United States Patent
Application |
20170296769 |
Kind Code |
A1 |
Smith; Daniel John ; et
al. |
October 19, 2017 |
COMPONENTS FOR BREATHING CIRCUITS
Abstract
A breathing circuit component includes an inlet, an outlet and
an enclosing wall. The enclosing wall defines a gases passageway
between the inlet and the outlet. At least a region of the
enclosing wall is formed from a breathable material that allows the
passage of water vapor without allowing the passage of liquid water
or respiratory gases. The breathing circuit component may be the
expiratory limb of a breathing circuit.
Inventors: |
Smith; Daniel John;
(Auckland, NZ) ; Millar; Gavin Walsh; (Auckland,
NZ) ; Powell; Kevin Blake; (Auckland, NZ) ;
Baldwin; David Peter; (Ayrshire, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fisher & Paykel Healthcare Limited |
East Tamaki |
|
NZ |
|
|
Family ID: |
26652172 |
Appl. No.: |
15/633557 |
Filed: |
June 26, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
12328200 |
Dec 4, 2008 |
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15633557 |
|
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|
|
11371389 |
Mar 9, 2006 |
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|
12328200 |
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|
|
10622755 |
Jul 18, 2003 |
7140366 |
|
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11371389 |
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09850797 |
May 8, 2001 |
6769431 |
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|
10622755 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 2207/10 20130101;
A61M 2207/00 20130101; A61M 2205/7536 20130101; A61M 16/08
20130101; B29C 48/04 20190201; B29C 48/32 20190201; A61M 16/1065
20140204; B29C 53/585 20130101; A61M 2230/432 20130101; A61M
16/0875 20130101; B29C 53/70 20130101; B29L 2031/753 20130101; B29C
53/68 20130101; B29C 48/0019 20190201; B29L 2023/007 20130101; A61M
16/1045 20130101; A61M 16/0883 20140204; A61M 16/0833 20140204;
B29C 48/07 20190201; B29C 48/301 20190201; A61M 16/0808 20130101;
B29C 48/09 20190201; A61M 39/08 20130101; A61M 2039/082 20130101;
B29C 53/64 20130101 |
International
Class: |
A61M 16/08 20060101
A61M016/08; A61M 16/10 20060101 A61M016/10; B29C 47/00 20060101
B29C047/00; B29C 53/68 20060101 B29C053/68; B29C 53/58 20060101
B29C053/58; B29C 47/12 20060101 B29C047/12; A61M 16/08 20060101
A61M016/08 |
Foreign Application Data
Date |
Code |
Application Number |
May 10, 2000 |
NZ |
504439 |
Dec 20, 2000 |
NZ |
509041 |
Claims
1. A breathing circuit component including an inlet, an outlet and
an enclosing wall defining a gases passageway between said inlet
and said outlet, at least a region of said wall being of a material
that allows the passage of water vapor without allowing the passage
of liquid water or respiratory gases.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/328,200, filed Dec. 4, 2008, which is a
continuation of U.S. patent application Ser. No. 11/371,389, filed
Mar. 9, 2006, now abandoned, which is a division of U.S. patent
application Ser. No. 10/622,755, filed Jul. 18, 2003, now U.S. Pat.
No. 7,140,366, issued Nov. 28, 2006, which is a division of U.S.
patent application Ser. No. 09/850,797, filed May 8, 2001, now U.S.
Pat. No. 6,769,431, issued Aug. 3, 2004, which claims the benefit
of New Zealand Patent Application No. 504439, filed May 10, 2000
and New Zealand Patent Application No. 509041, filed Dec. 20, 2000,
all of which are incorporated by reference in their entirety. In
addition, any and all applications for which a foreign or domestic
priority claim is identified in the Application Data Sheet as filed
with the present application are incorporated by reference in their
entirety.
BACKGROUND TO THE INVENTION
1. Field of the Invention
[0002] The present invention relates to components for breathing
circuits and in particular to components for use in the expiratory
arm of a breathing circuit.
2. Summary of the Prior Art
[0003] In assisted breathing, particularly in medical applications,
gases having high levels of relative humidity are supplied and
returned through conduits of a relatively restricted size. Buildup
of condensation on the inside wall of the conduit is a frequent
result of this high humidity. In the prior art, attempts have been
made to reduce the adverse effect of this condensation by either
reducing the level of condensation or providing collection points
in the conduit for draining condensed liquid from the conduit
Reducing the condensation has generally been by maintaining or
elevating the temperature of the gases flow and/or of the conduit
wall to reduce the formation of condensation.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to provide a
component, with particular application to the expiratory limb of a
breathing circuit, which will at least go some way towards
improving on the above or which will at least provide the public
and the medical profession with a useful choice.
[0005] In a first aspect the invention consists in a breathing
circuit component including an inlet, an outlet and an enclosing
wall defining a gases passageway between said inlet and said
outlet, at least a region of said wall being of a material that
allows the passage of water vapor without allowing the passage of
liquid water or respiratory gases.
[0006] In a further aspect the invention consists in a breathing
circuit limb having both inspiratory and expiratory gases
passageways, each having a respective inlet and outlet and a wall
defining a gases passageway extending from said inlet to said
outlet, at least a region of the wall of the expiratory conduit
being of a material that allows the passage of water vapor without
allowing the passage of liquid water or respiratory gases.
[0007] In a still further aspect the invention consists in a
catheter mount including: [0008] a short length of breathing
conduit for connecting at one end to a patient interface component
and at the other end to, directly or indirectly, the dual arms of a
breathing circuit, [0009] a dividing partition extending for at
least a substantial part of the length of said breathing conduit
and dividing, in cross section, said conduit into a plurality of
gases passageways each having a defining passageway wall, [0010] at
least one of: [0011] an inspiratory flow director for directing at
least the bulk of an inspiratory air flow to a first selection of
said passageways, and [0012] an expiratory flow director for
directing at least the bulk of an expiratory flow to a second
selection of said passageways, said second selection being
exclusive of said first selection, [0013] and at least a region of
the walls of said second selection of passageways being of a
material that allows the passage of water vapor without allowing
the passage of liquid water or respiratory gases.
[0014] In a still further aspect the invention consists in a
dedicated water vapor exchanger including an inspiratory gases
pathway and an expiratory gases pathway having a common wall
therebetween, said common wall including one or more regions of a
material that allows the passage of water vapor without allowing
the passage of liquid water or respiratory gases.
[0015] In a still further aspect the invention consists in
apparatus for forming a breathing circuit conduit comprising:
[0016] a former, onto which a tube wall can be deposited and which
advances said deposited tube wall in an advance axis and rotates
said deposited tube wall about said advance direction, the speed of
said advance and the speed of said rotation together defining a
pitch, [0017] at least one film laying head which deposits a film
on said former, the combined width of said film deposited by said
film laying heads being wider than said pitch such that adjacent
turns of laid film overlap to form an overlap seam, [0018] a bead
laying head for each said film laying head, each said bead laying
head laying a reinforcing bead on an overlap seam, [0019] an axial
thread laying head, said thread laying head fitted over and around
said former and carrying a plurality of thread feeds, each thread
feed allowing the drawing of a thread from a reserve, and [0020] a
rotator to rotate said axial thread laying head at substantially
the same speed as the expected rotation speed of said tube.
[0021] Hereinafter, throughout the description, a material that
allows the passage of water vapor without allowing the passage of
liquid water or respiratory gases is described as a "breathable"
material. Materials may be breathable due to their composition,
physical structure a combination thereof.
[0022] To those skilled in the art to which the invention relates,
many changes in construction and widely differing embodiments and
applications of the invention will suggest themselves without
departing from the scope of the invention as defined in the
appended claims. The disclosures and the descriptions herein are
purely illustrative and are not intended to be in any sense
limiting.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a cross sectional elevation of a conduit for the
expiratory limb of a breathing circuit according to one embodiment
of the present invention,
[0024] FIG. 2 is a cross sectional view of a section of conduit
wall according to one possible construction,
[0025] FIG. 3 is a cross sectional view of a co extrusion die head
for extruding a conduit including two longitudinal strips of
permeable material, similar to the conduit of FIG. 1,
[0026] FIG. 4 is a cross sectional elevation of a coaxial breathing
circuit according to a further embodiment of the present invention
and incorporating a conduit in accordance with the present
invention,
[0027] FIG. 5 is a side elevation in partial cross section of the
coaxial breathing circuit of FIG. 4,
[0028] FIG. 6 is a side elevation partially in cross section of an
expiratory limb conduit according to a further embodiment of the
present invention,
[0029] FIG. 7 is a cross sectional side elevation of an expiratory
limb for a breathing circuit according to a further embodiment of
the present invention,
[0030] FIG. 8 is a cross sectional side elevation of an expiratory
limb for a breathing circuit according to a still further
variant,
[0031] FIGS. 9a-9i demonstrate a range of conduit constructions
including longitudinal reinforcement of varying types,
[0032] FIG. 10 is plain view of a conduit forming device for
forming a reinforced twin walled conduit according to the present
invention, such as the conduit depicted in FIG. 9h or 9i,
[0033] FIG. 11 is a plain view of a conduit forming device for
forming a reinforced conduit according to FIG. 7,
[0034] FIG. 12 is a plain view of a similar conduit forming device
for forming a reinforced conduit according to FIG. 8, and
[0035] FIG. 13 is a cross sectional side elevation of a catheter
mount incorporating the present invention.
DETAILED DESCRIPTION
[0036] Referring to FIG. 1 in one embodiment of the invention the
conduit 4 of the expiratory limb of a breathing circuit is formed
having one or more longitudinal strips 2, 3 of breathable membrane
as part of the wall 1 thereof.
[0037] One possible material for the breathable regions is an
activated perfluorinated polymer material having extreme
hydrophilic properties. An example of this polymer material is
marketed under the trade mark NAFION by DuPont Fluoro products of
Fayetteville USA. This material is useful due to its extreme
hydrophilic properties and due to its ability to be extruded,
particularly to be co-extruded in combination with other plastic
materials.
[0038] Alternative materials are also envisaged including: [0039]
(a) Hydrophilic thermoplastics, [0040] (b) woven treated fabric
products exhibiting breathable characteristics
[0041] The preferred material is a hydrophilic polyester block
copolymer formed into a homogeneous flat film. An example of such a
film is sold under the brand SYMPATEX. This material is
particularly suited to thin film productions.
[0042] Referring to FIG. 6 an alternative embodiment of the
expiratory limb is shown in which the entire flexible wall membrane
of the conduit is formed from a breathable plastic membrane,
extruded and wound helically with edges of adjacent turns sealed to
one another.
[0043] Further variations on the embodiment of FIG. 6 are
depictured in FIGS. 9a to 9i, 7 and 8. In these figures the
flexible wall membrane of the conduit is supplemented by
reinforcing to provide resistance to lateral crushing and to
longitudinal stretching of the conduit. Further variations are
shown including variants having multiple breathable plastic
membranes. Apparatus for forming such conduits is described with
reference to FIGS. 10, 11 and 12.
[0044] Referring to FIGS. 4 and 5 a further aspect of the present
invention is shown in which an expiratory limb conduit according to
the present invention is provided as the inner conduit of a coaxial
conduit configuration, such that expiratory gases and inspiratory
gases each flow in one of the inner conduit or the space between
the inner conduit and the outer conduit and in use water vapor but
not liquid water is transmitted from the expiratory gases
passageway to the inspiratory gases passageway.
[0045] A further component that may usefully include the present
invention is a catheter mount. The application of the invention to
a catheter mount is described with reference to FIG. 13.
[0046] It would be possible alternatively, to have one or more
longitudinal sections (lengths) of the conduit being formed of the
breathable material or isolated regions of the conduit wall being
formed from the material. However the embodiments described herein
are preferred due to their apparent simplicity of manufacture,
being capable of linear manufacture, either by continuous
stitching, gluing or welding, by co-extrusion or by winding onto a
former.
[0047] As a corollary of material cost it is preferred that the
conduit wall be manufactured to have a relatively low wall
thickness, so much so that the conduit wall membrane may be
insufficiently sturdy to be self-supporting.
[0048] Referring to FIGS. 2, 6, 9a to 9i, 7 and 8, a spiral or
helical internal (or external) reinforcing members, or a series of
annular hoop reinforcing members, may be provided outside (or
inside) the tubular membrane to provide support. The helical,
spiral or hoop supporting members may for example be formed from
polymer plastic materials, such as the material used in the wall of
the conduit (not being the breathable regions), or alternatively
may for example be a metal wire support, such as drawn steel
wire.
[0049] The conduit shown in FIG. 2 may be formed in any one of a
number of methods. For example the tubular membrane may be supplied
in a continuous tube. Alternatively it might be supplied in tape
form, which may result in the conduit of FIG. 6. Supplied as
extruded tape, the membrane may be wound helically onto a former.
The helical supporting rib, provided in a semi molten state is then
laid on the overlap between adjacent turns. The heat from the
helical supporting rib bonds the two adjacent strips with the rib
forming a flexible resilient conduit once cooled.
[0050] Referring to FIG. 6 an additional sheathing layer 83 may be
provided over the outside of the conduit. The sheathing layer 83 is
supported on the apexes of the ribs 30. The sheathing layer 83 may
be a further strip or tape of extruded plastic film wound helically
onto the conduit formed on the former. This additional sheath may
have a number of purposes and benefits. The sheathing layer 83 may
be formed to provide additional strength, reinforcement and
protection, for example by selecting an appropriate material or by
selecting an appropriate material thickness. The material may be a
breathable material, such as that which may be the basis of the
inner conduit wall or may be formed from a less expensive
non-permeable material. In that case a series of holes or
perforations 85 are preferably provided along the strip or tape 84
to provide egress of water vapor or collected condensed water. The
holes or perforations 85 may advantageously be formed by pricking
holes in the tape 84 using a heated lance during the forming
process. Shrinking of the plastic film away from the heated lance
has been found to produce consistent and suitably sized holes with
an annulus of built up material providing reinforcing at the lip of
the hole. The sheath 83, in addition to providing reinforcement and
protection for the inner conduit, also provides a barrier to air
flow over the inner conduit thereby providing an insulating effect.
The insulating effect is greater where there are no perforations 85
through the sheath 83.
[0051] Referring to FIGS. 9a-9i it has been found that one of the
difficulties with using a breathable membrane such as SYMPATEX is
its low elastic yield strength. Accordingly under longitudinal
force the SYMPATEX membrane may be easily stretched non-elastically
leading to loss of aesthetic appearance and a constriction in the
tube diameter. The multiple walled embodiment described with
reference to FIG. 6 goes some way toward overcoming this
difficulty, providing as it does a second layer of breathable
material. Furthermore in the perforated form the outer plastic
membrane may be formed from a plastic material having a greater
elastic yield strength than the preferred SYMPATEX.
[0052] An alternative structure may be used as a longitudinal
reinforcement for the tube. This reinforcement is preferably
provided in a form of an additional sheath having an open or mesh
structure. For example the sheath may be provided by a plurality of
parallel extruded polymer threads running parallel to the axis of
the conduit, a plurality of extruded polymer threads braided or
similarly arranged about the conduit and having a substantial axial
component in their direction, or by a preformed or continuously
formed mesh, formed to make a sheath in a similar fashion to the
method used for forming the breathable wall. Such a mesh material
may be produced by forming a non-woven or woven mesh of individual
polymer threads or by stretching a micro perforated sheet to make
an expanded mesh, or by other suitable processes. Part or each of
these processes may be conducted at the time of, or immediately
preceding, using the mesh in forming the reinforcing sheath.
[0053] A variety of alternative conduit embodiments incorporating a
reinforcing sheath, such as introduced above, are depicted in FIGS.
9a to 9i. Two other preferred forms are depicted in FIGS. 7 and 8.
These embodiments have various advantages and/or disadvantages.
[0054] Referring to FIG. 9a a conduit is formed from an extruded
tape 200 helically wound on a former to form the breathable wall. A
mesh sheath 202 is formed from a mesh tape helically wound onto the
outside of the breathable membrane 200. The overlapping edges of
the mesh tape and the breathable membrane tape coincide and a
molten plastic bead 201 is laid along these edges. The molten bead
preferably provokes thermal bonding of all four coinciding layers,
two of breathable membrane and two of polymer mesh. It will be
appreciated that the polymer mesh may be on the inside or outside
of the breathable membrane. However it is preferred that the
internal surface of the conduit wall be smooth and hence it is
preferred that the mesh tape be applied to the outside of the
breathable membrane. It will be appreciated that each turn of mesh
tape may be applied directly over each turn of breathable membrane
contemporaneously so that the edges of adjacent turns overlap an
edge of mesh tape comes between the edges of adjacent turns of
breathable membrane tape, which is alternative to how it is
depicted in FIG. 9a. It will also be appreciated that either or
both of the breathable membrane tape and the mesh tape may be
formed contemporaneously with forming the conduit therefrom and the
mesh and membrane may accordingly bond over some or all of their
contacting surfaces in addition to bonding achieved by heat from
the bead 201.
[0055] Referring to FIG. 9b a conduit is formed having the same
construction of breathable membrane 200, mesh 202 and bead 201. In
addition a further sheath of breathable membrane 203 may be applied
to the outside of the conduit, with the edges of adjacent urns 203
pressed onto and bonded to the outside of bead 201. This provides
additional thermal insulation while allowing for dehumidification
of the space between the inner and outer walls.
[0056] Referring to FIG. 9c the conduit of 9a is shown having
breathable membrane wall 200, mesh sheath 202 and bead 201. In the
embodiment of FIG. 9c a further breathable membrane sheath 204 is
provided on the outside of the mesh sheath 202. The effect of this
is to encapsulate the mesh 202 providing an improved aesthetic
appearance and more acceptable external surface. A disadvantage of
his constriction is the multitude of layers which the heat from
bead 201 is required to thermally bond. Accordingly a construction
of this type may require additional localized heating to thermally
weld the overlapping edges of adjacent turns of membranes 200, 202,
and 204.
[0057] Referring to FIG. 9d a variation on the embodiment shown in
FIG. 9c is depicted. In this embodiment the outer breathable
membrane 205 is inflated away from the mesh membrane 202 where in
FIG. 9c the outer breathable membrane 204 lay against or bonded
with the mesh membrane 202. In FIG. 9d the breathable 205 is
supported away from the underlying membranes 200, 202 by an
inflated pocket 211. This may be considered a variant of FIG. 9b
wherein the bead 201 is provided entirely on the outside of the
conduit. The multitude of layers at adjoining edges poses the same
forming difficulties as the embodiment of FIG. 9c.
[0058] Referring to FIG. 9e a section of the conduit in which the
mesh sheath is provided spaced from the breathable membrane conduit
wall 200. The mesh sheath 206 is provided over the bead 201 at
least in the vicinity of the joining of adjacent turns of the
breathable membrane 200. Where the mesh sheath is formed from a
wound tape, then adjacent turns 206 of the wound tape bond over the
bead 201 upon action of the heat residing in the bead 201. This
embodiment reduces the number of adjacent layers required to be
bonded by the bead 201 and allows the layers of breathable membrane
and mesh respectively to operate independently making this tube
more supple than for example for tube in FIG. 9a.
[0059] FIG. 9f is a variation of the embodiment of FIG. 9e. While
an air space was provided between the mesh layer 206 and the
breathable membrane layer 200 in FIG. 9e, in FIG. 9f the mesh layer
207 is shrunk, vacuumed or collapsed to lie adjacent the breathable
membrane layer 200. Where one or more of the breathable membrane
and mesh are formed contemporaneous with forming of the conduit
then where these layers 207 and 200 meet they may bond across some
or all of their contacting area. This embodiment provides the
formative advantages of FIG. 9e and a construction having similar
qualities to that of FIG. 9a.
[0060] Referring to FIG. 9g, in a further embodiment, an additional
breathable membrane is provided to the embodiment of FIG. 9f,
spanning between turns of bead 201 and the outside of the mesh 207.
To assist with bonding and for further reinforcement purposes a
further bead 209 may be provided on the outside of the second
breathable layer 208.
[0061] Referring to FIG. 9h a still further embodiment is shown,
which is a variation of the embodiment shown in FIG. 9g. In the
embodiment of FIG. 9h a second layer of breathable membrane 210 is
provided on the outside of second bead 209. This is instead of
being between the second bead 209 and the mesh layer 207 as the
second breathable layer 208 was in the embodiment FIG. 9g. This
provides a larger included air space between breathable layers 202
and 210 and at any time only a double thickness of polymer, film or
mesh is required to be bonded by the beads 201 or 209.
[0062] Referring to FIG. 9i a still further embodiment is shown,
being a variation of the embodiment shown in 9h. In the embodiment
of 9i the mesh layer 206 rather than being the deflated, collapsed
or vacuumed form as in FIGS. 9f-9h, it is taut between turns of
bead 201, in the fashion of 9e. This provides a pair of air spaces
between the breathable layers 200 and 210, with the mesh layer 206
partially inhibiting the free air flow between the layers. However,
this construction has the disadvantage that the freely suspended
mesh 206 may encourage rain out in the space enclosed between the
breathable membranes 200 and 210, thereby retaining liquid water
within the helical wall cavity.
[0063] All of the above described configurations are considered to
provide additional longitudinal reinforcement, with each having
advantages and disadvantages, some of which have been specified. In
forming these constructions bonding is required between some or all
of the various layers, for example between the breathable membrane
and one or other bead, the bead and the mesh, the mesh and
breathable membrane. Accordingly, it is preferred that
appropriately compatible materials are used for each element of the
construction. For example while a molten polyester bead may
mechanically bond adequately with nylon or polypropylene mesh a
brittleness may develop and/or this impeded the simultaneous
bonding of the bead with an adjacent layer of polyester based
breathable membrane, for example in the embodiment of FIG. 9a.
Consequently it is preferred that all three elements have the same
base polymer, and for example, for SYMPATEX which is polyester
based product, a polyester bead and mesh are preferred.
[0064] Further variations on the above embodiments may include
replacement of the outer breathable layer in FIGS. 9b, c, d, g, h
and i with a perforated non permeable layer, as desired. However,
such variation does not provide the full insulative effect while
retaining liquid vapor transmission from the insulating space to
allow for further transmission through the conduit wall.
[0065] An example of forming apparatus suitable for manufacturing
the product the breathing tube according to the embodiments
described in FIGS. 9a-9i is shown in FIG. 10. In particular the
apparatus is shown forming a conduit according to FIG. 9h or 9i.
The apparatus includes a former 300 preferably of a known type
including a plurality of rotating rods arranged around a central
support rod. The rods extend from and are rotated by a gearbox
within a machine stock 301. At least in the tube forming region the
rotating rods follow a helical path. The pitch angle of the rods
relative to the support rod controls the pitch angle of the tube
being formed. An example of such a machine is a spiral pipeline
mandrel available from OLMAS SRL of Italy. Tube being formed on the
former is rotated and advanced in the direction of arrow 303 by the
movement of the rotating rods. The advance speed of the former is
selected relative to the rotational speed so that the pitch of the
helical laying of the strip or tape on to the former 300 is a
little less than the width of the strip so that adjacent turns
narrowly overlap. A first extruder 304 extrudes a tape 314 of
breathable polymer materials. The tape 314 deposits on the former
300 in a helical fashion by action of the former. The pitch of the
helical disposition of tape 314 is slightly less than the width of
tape 314. The helical deposition of tape 314 forms the inner
breathable wall 200 of the conduit. A second extruder 305 extrudes
a bead 315 of polymer material. The bead 315 deposits on the former
over the joint or overlap between adjacent turns of tape 314
forming a raised bead 201 along this join. A tape 316 of
reinforcing membrane is unrolled from a reel 306 to have edges
depositing on adjacent turns of bead 201. The helically deposited
reinforcing tape 316 forms reinforcing layer 206. A third extruder
307 extrudes a second molten polymer bead 317. The bead 317 is
helically deposited along the overlap between adjacent turns of
reinforcing tape 316. A fourth extruder 308 extrudes a second tape
318 of breathable polymer. The second tape 318 of breathable
polymer is deposited on the former 300 to span between adjacent
turns of second bead 317. Adjacent us of tape 318 overlap while
sufficiently molten to fuse above the second bead 209, forming
outer breathable sheath 210.
[0066] In addition to the bonding of the film overlap by
application of the molten bead other active fusing techniques may
be applied. This may be particularly useful where a layer of
longitudinal reinforcement or scrim is provided immediately
adjacent the breathable film layer. Active methods may include hot
air welding, hot rollers or radio frequency welding. In hot air
welding a stream of hot air is blown on to the overlap of adjacent
turns of breathable film, melting or fusing the adjacent edges
together. This method has been found reasonably successful.
[0067] For hot roller welding a heated roller or rollers run in
contact with the overlap and melt the film together Like hot air
welding hot roller welding relies on the application of a localized
direct heating to the film overlap.
[0068] For radio frequency welding the film acts as an insulation
layer between a pair of plates. A charge is passed between the
plates melting and fusing the plastic film overlap together. The
plates may take the form of a pair of rollers, one inside and one
outside the tube, or a roller and one of the rotating rods of the
former. Providing the plates as rollers (or as roller and forming
mandrel) may render the radio frequency welding a continuous
process with similar advantages to hot air welding and hot roller
welding.
[0069] In a further variation on the manufacturing process the
breathable film tube may be manufactured having a longitudinal seam
rather than being formed as a continuous helical strip. In such an
embodiment a wider web of film would be wrapped around a mandrel as
it is extruded or unrolled from a reel. Longitudinal edges would
overlap and be seam welded by any of the above mentioned methods. A
rotary extruder may then extrude a reinforcing bead or beads on to
the plastic film. Further reinforcing or film layers and helical
beads may be applied by additional wrapping stations or rotating
extruders as required.
[0070] Still other embodiments of a expiratory breathing conduit
including longitudinal reinforcement are depicted in FIGS. 7 and 8.
These embodiments utilize longitudinal reinforcing threads running
parallel to the axis of the conduit.
[0071] In the embodiment of FIG. 7 the conduit includes an inner
breathable polymer wall 250 with a plurality of axially extending
reinforcing reads 251 running the length of said wall and spaced
around the perimeter of the tube. The threads 251 are aligned
parallel to one another and to the major axis of the conduit. A
layer of additional longitudinal reinforcement 252, such as
described earlier, and which may be a woven or non-woven mesh,
aligned in any suitable orientation (although preferably aligned
with the principal threads running at an angle to the major axis of
said conduit) encloses the breathable permeable wall and
reinforcing threads. A helical bead 253 is fused or adhered to the
outside of the mesh 252.
[0072] A preferred method of forming the tube according to the
embodiment of FIG. 7 is described with reference to the apparatus
shown in FIG. 11. In particular in the apparatus of FIG. 11 both
the inner, breathable, tube 250 and longitudinal reinforcement
layer 252 are formed by helically wrapping a preformed tape or
strip of the base material (breathable polymer strip 260 or mesh
strip 262 respectively) on to a rotating former 270 (such as
described earlier with reference to FIG. 10). The strip 260 or 262
unrolls from reels 273 and 274 respectively. Adjacent turns of
breathable polymer 260 overlap at their edges. These overlapping
edges are fused by thermal welding. Thermal welding is conducted as
a continuous process by a hot air welding head 275. Rotation and
advancement of the former 270 by the rotation head 271 continually
passes the seam between adjacent edges of tape 260 past the head
275. A freely rotatable thread laying head 276 is located over the
former 270 at a position between the hot air welding head 275 and
the mesh spool 274. The rotating head 276 carries a plurality of
spools 279 holding the reinforcing threads 251. The head 276 is
rotatable by an electric motor and drive belt 277 and 278
respectively. The head 276 is preferably rotated at a speed
synchronized with the speed of rotation of the former 270.
Advancement of the former 270 draws thread 280 from the spools 279
to be laid as parallel threads 251 on the outside of the breathable
membrane 250. The tape 262 of longitudinal reinforcement is
subsequently applied over the threads 251 as a helical arrangement
with edges of adjacent turns overlapping to form a continuous
sheath. A bead 263 is extruded by an extruder 281 on to the overlap
between adjacent turns of the mesh tape 262 to thereby form the
helical reinforcing bead 253.
[0073] This embodiment of the invention provides a breathable
exhalation limb reinforced against crushing by the helical bead and
against longitudinal extension by the axial threads 251. The mesh
sheath 252 protects the axial threads from snagging or pulling.
[0074] In the embodiment of FIG. 8 the conduit includes an inner
breathable polymer wall 350. A helical bead 353 is fused or adhered
to the inner breathable wall 350. A plurality of reinforcing
threads 251 running the length of the wall and spaced around the
perimeter of the tube are aligned parallel to one another and to
the major axis of the conduit. The threads 351 are supported on the
helical bead 353, with the threads spanning the spaces between
turns of the helical bead. In this embodiment it is important to
choose the reinforcing threads (material, gauge and number) such
that the threads are sufficiently stiff to resist buckling under
the transiently reduced internal pressures that could be expected
during patient breathing. Unrestrained or excessive buckling of the
threads could lead to unacceptable levels of conduit axial
contraction. The axial threads 351 may be a spun or braided fibers,
drawn or extruded mono filaments or other equivalent forms.
[0075] A preferred method of forming the tube according to the
embodiment of FIG. 8 is described with reference to the apparatus
shown in FIG. 12. In particular in the machine of FIG. 12 the
breathable tube 350 is formed by helically wrapping a preformed
tape or strip of breathable polymer strip 360 on to a rotating
former 370. The strip 360 unrolls from reels 373. Adjacent turns of
breathable polymer 360 overlap at their edges. These overlapping
edges are fused by thermal welding. Thermal welding is conducted as
a continuous process by a hot air welding head 375. Rotation and
advancement of the former 370 continually passes the seam between
adjacent turns of tape 360 past the head 375. A bead 363 is
extruded by an extruder 381 on to the overlap between adjacent
turns of the breathable tape 362 to thereby form the helical
reinforcing bead 353. A freely rotatable threadlaying head 376 is
located over the former after the bead extruder 381. The rotating
head 376 carries a plurality of spools 379 holding the reinforcing
threads 351. The head 376 is rotatable by an electric motor and
drive belt 377 and 378 respectively. The head 376 is preferably
rotated at a speed synchronized with the speed of rotation of the
former 370. Advancement of tube along the former 370 draws thread
380 from the spools 379 to be laid as parallel threads 351 on the
outside of the reinforcing bead.
[0076] This embodiment of the invention provides a breathable
exhalation limb reinforced against crushing by the helical bead and
against longitudinal extension by the axial threads 351. The
spanning threads prevent direct contact between a user and the
surface of the breathable tube, reducing the risk of punctures and
the like.
[0077] It should be appreciated that with all of the forming
methods involving winding of a narrow tape or strip to create a
tube, it would be possible to wind two or more tapes or strips
simultaneously onto the former so that the turns created by each
tape are interposed by turns of other tapes, edges overlapping and
being bonded together. For example a pair of tapes may be laid as a
double helix. This would require a multiplication in the number of
forming stations associated with the wound on components of the
tube or conduit.
[0078] Referring to FIG. 3 other forms of the conduit, such as that
shown in FIG. 1, may be formed by co extrusion of the breathable
material (where the material is a suitable extrudable material)
with a plastic material forming the remainder of the conduit wall.
A suitable co extrusion die 9 is depicted in FIG. 3 in which a pair
of circumferential sections 7 of the die opening have the
breathable plastic material extruded therethrough, and the
remainder sections 8 of the annular extrusion opening have the
non-permeable plastic wall material extruded therethrough.
[0079] The purpose of the breathable region or regions of the
conduit wall is to allow diffusion of water vapor from the
expiratory limb of the breathing circuit along the path thereof
independent of specific drain locations. This eliminates the
buildup of condensation within the expiratory limb by drying the
humidified gases during their flow through the expiratory limb.
This furthermore reduces the humidity of the gases arriving at
ancillary equipment, such as filters, ventilators and the like
reducing the risk of condensation accumulation, thereby improving
their operation.
[0080] In accordance with a further aspect of the invention, and as
exemplified in FIGS. 4 and 5 the conduit incorporating one or more
longitudinal strips of breathable membrane may further be
incorporated in a coaxial breathing circuit as a passive
humidification device. In particular referring to the cross section
in FIG. 4 the coaxial breathing circuit may include an outer
conduit 11 and an inner conduit 10. Preferably, for heat transfer
reasons, the inner conduit 10 carries the inspiratory flow in the
space 12 there within. The expiratory flow is preferably carried in
the space 13 between the inner conduit 10 and the outer conduit 11.
This airflow configuration is indicated by arrows 20, 19
respectively in FIG. 5.
[0081] The inner conduit 10 is formed having one or more
longitudinal strips 2, 3 of breathable membrane in the wall 1
thereof, as has previously been described with reference to FIGS.
1, 2 and 3. Thus humidity in the expiratory flow space 13 may pass
through the sections 2, 3 of breathable membrane to humidify the
inspiratory flow in inspiratory flow space 12.
[0082] The breathable membrane works on relative partial pressures
of water vapor so, with the flows in a counter flow arrangement
substantial passive humidification of the inspiratory flow can be
achieved.
[0083] Referring to FIG. 5 a circuit configured including the
coaxial conduit depicted in FIG. 4 is represented. In this circuit
the conduit has a patient end connector 15 and a ventilator end
connector 16 having inspiratory port 17 and an expiratory port 18.
The inspiratory 20 and expiratory 19 counter flows are
indicated.
[0084] With the coaxial conduit the ventilator may not become aware
of the leak in the interior conduit. Such a leak may short circuit
the patient meaning that the patient will not be supplied with
sufficient oxygen. Such a short circuit may be detected by
placement of a sensor at the patient end. Preferably this sensor
may be located in the patient end connector 15. A short circuit
closer to the ventilator will lead to continued patient rebreathing
of the air volume close to the patient. This will lead to a rise in
the concentration of carbon dioxide in the conduit close to the
patient which can be detected directly by a CO.sub.2 sensor. Such a
sensor may comprise any one of a number of such sensors as is
currently commercially available. Alternatively this re breathing
may be detected by monitoring the temperature of the gases at the
patient end connector 15, wherein a rise in temperature above a
predetermined level indicates that rebreathing is occurring.
[0085] In addition to the above to reduce or eliminate the
formation of condensation within either the inner or outer conduit,
10 or 11 respectively, and to maintain a substantially uniform
temperature in the gases flow through the conduit, a heater means,
such as a resistance heater wire, may be provided within either the
inner or outer conduit, disposed within the gases spaces 12 or 13
or within the conduit walls themselves. In one possibility the
heater wire may also serve as a reinforcing support (helical wire
25 in FIG. 4) within the inner conduit 10 or in the outside conduit
as with coaxial conduit.
[0086] A further breathing circuit component to which the present
invention can be applied is catheter mounts. A catheter mount
connects between a patient interfacing component such as a mouth
piece, nasal mask or endotracheal tube and the dual limbs of a
breathing circuit. Connection with the dual limbs of the breathing
circuit is generally via a wye connector. In the patient inhalation
and exhalation cycle the dual limbs of the breathing circuit each
have a distinct role, one as inhalation conduit and one as
exhalation conduit. The catheter mount serves a dual role,
transporting both inhaled and exhaled gases. Accordingly, the
catheter mount can have significant disadvantages.
[0087] A volume of exhaled air remains in the catheter mount
between exhalation and inhalation. Accordingly some air is
re-breathed by the patient. While not unacceptable, rebreathing is
not generally desirable and where significant rebreathing is
likely, a boost in oxygen supply levels may be required.
[0088] Gases inhaled by a patient are, in a well-managed
ventilation system, delivered in a condition having humidity near a
saturation level and at close to body temperature, usually at a
temperature between 33.degree. C. and 37.degree. C. This
temperature may be maintained by a heater in the inhalation conduit
right up to the point where the gases enter the catheter mount.
Gases exhaled by a patient are returned fully saturated and are
subjected to further cooling as they flow through the catheter
mount. Accordingly, although little condensation forms on the
interior walls during patient inhalation, significant condensation
levels may form during patient exhalation. The condensation, or
rain out, occurring inside the catheter mount is particularly
deleterious due to its proximity to the patient. Mobile condensate
breathed or inhaled by a patient may lead to coughing fits or other
discomfort.
[0089] A catheter mount incorporating the present invention is
depicted in FIG. 13. The catheter mount incorporates the wye
connector at the ventilator end. An internal conduit 455 extends
coaxially with the outer conduit 456. The internal conduit 455 is
supported at its patient end on an internal conduit connector 457
which is turn is supported via support struts 458 from patient end
connector 459. The inner conduit 455 is supported at its other end
on an inner conduit connector 460 which forms part of the
ventilator end connector 461.
[0090] In the catheter mount of FIG. 13 the ventilator end inner
conduit connector 460 communicates with the inspiratory conduit
connector 462. The outer conduit 456 has at least a part of its
wall being made from a breathable material. Preferably the outer
conduit 456 is formed entirely from breathable material, and may
also include lateral reinforcement (a spiral reinforcing bead 467)
and longitudinal reinforcement (axially oriented threads 490) on
the outside thereof. When constructed according to the manner
earlier described with respect to FIGS. 12 and 8 the spiral bead
467 is laid on the overlap between consecutive turns of the
extruded tape and assists fusion of the overlap and reinforcement
against crushing.
[0091] Therefore in use the catheter mount according to FIG. 13 has
an inspiratory flow entering the catheter mount a s indicated by
arrow 470. The inspiratory flow passes through the inner conduit to
exit to the patient through the patient end connector 459 as
indicated by arrows 471. Upon patient exhalation, whether assisted
or otherwise, expired gases pass through connector 459 and into the
space surrounding the inner conduit 455 as indicated by arrows 472.
These gases pass along the inside of the wall of outer conduit 456
as indicated by arrows 473 and out through the expiratory tube
connector 463 of ventilation connector 461 as indicated by arrow
474. In passing through the catheter mount within the space between
the inner conduit 455 and the outer wall 456 water vapor may pass
through the water vapor permeable portions of the outer conduit
456. Preferably the entire of outer conduit 456, apart from any
reinforcing rib, is breathable. In this way, although the expired
gases may experience some temperature drop as they pass through the
catheter mount to the expiratory conduit connector 463, hand in
hand with this temperature drop is a reduction in humidity by water
vapor passing through the breathable membrane of the outer conduit.
Accordingly, relative saturation of the expiratory flow is reduced
and rain out is reduced.
[0092] The catheter mount incorporating features according to the
present invention includes explicit division of the inspiratory and
expiratory flows through the catheter mount, significantly reducing
rebreathing. Rain out is also reduced by reducing the humidity of
the expired gases even as the temperature of those gases
reduces.
[0093] While some embodiments of the present invention have been
described as preferred and convey particular advantages over other
embodiments many other combinations may prove commercially
useful.
* * * * *