U.S. patent application number 11/780856 was filed with the patent office on 2009-01-22 for patient delivery tube for humidified oxygen.
Invention is credited to Ronny Bracken.
Application Number | 20090020118 11/780856 |
Document ID | / |
Family ID | 40263832 |
Filed Date | 2009-01-22 |
United States Patent
Application |
20090020118 |
Kind Code |
A1 |
Bracken; Ronny |
January 22, 2009 |
Patient Delivery Tube for Humidified Oxygen
Abstract
A patient delivery tube for the delivery of a heated, humidified
gas. The patient delivery tube includes an elongated tubing member
molded from a flexible polymer, said elongated tubing member
comprising a first end, a second end and an axially aligned
passageway extending therethrough and an electric heater comprising
a conductive material, said electric heater arranged along said
axially aligned passageway for perimetrically heating said axially
aligned passageway. A method of delivering a heated, humidified gas
to a patient is also provided.
Inventors: |
Bracken; Ronny; (Conyers,
GA) |
Correspondence
Address: |
BRIAN M. BURN, ESQ.;C. R. BARD MEDICAL DIVISION
P.O. BOX 52050, c/o PORTFOLIOIP
MINNEAPOLIS
MN
55402
US
|
Family ID: |
40263832 |
Appl. No.: |
11/780856 |
Filed: |
July 20, 2007 |
Current U.S.
Class: |
128/204.17 |
Current CPC
Class: |
A61M 16/1095 20140204;
A61M 2202/0208 20130101; A61M 16/08 20130101; A61M 16/1075
20130101; A61M 16/0875 20130101; Y10S 261/65 20130101 |
Class at
Publication: |
128/204.17 |
International
Class: |
A61M 16/10 20060101
A61M016/10 |
Claims
1. A patient delivery tube for the delivery of a heated, humidified
gas, comprising: (a) an elongated tubing member molded from a
flexible polymer, said elongated tubing member comprising a first
end, a second end and at least one axially aligned passageway
extending therethrough; and (b) an electric heater comprising a
conductive material, said electric heater arranged along said
axially aligned passageway for perimetrically heating said axially
aligned passageway.
2. The patient delivery tube of claim 1, wherein said flexible
polymer is chosen from polyurethane, polyethylene, polypropylene,
polyester, and copolymers, terpolymers and blends thereof.
3. The patient delivery tube of claim 2, wherein said elongated
tubing member further comprises first and second lumens, said first
and second lumens positioned so as to at least partially surround
said axially aligned passageway.
4. The patient delivery tube of claim 3, wherein said conductive
material of said electrical heater comprises a conductive gel, said
conductive gel contained within at least one of said first and
second lumens of said elongated tubing member.
5. The patient delivery tube of claim 4, wherein said conductive
gel is formed by dispersing a plurality of conductive particles
within a gelatinous dielectric medium
6. The patient delivery tube of claim 5, wherein said conductive
particles are chosen from silver-coated nickel particles,
silver-coated glass particles, carbon particles, silver spheres,
silver flakes and mixtures thereof.
7. The patient delivery tube of claim 6, wherein said gelatinous
dielectric medium comprises silicone gel.
8. The patient delivery tube of claim 2, wherein said elongated
tubing member is a single lumen tube having an outer surface.
9. The patient delivery tube of claim 8, wherein said conductive
material comprises a conductive ink, said conductive applied to
said outer surface of said elongated tubing member
10. The patient delivery tube of claim 8, further comprising an
elongated protective cover, wherein said elongated protective cover
is positioned over said outer surface of said elongated tubing
member.
11. The patient delivery tube of claim 10, wherein said conductive
ink is a positive temperature coefficient ink.
12. The patient delivery tube of claim 10, wherein said conductive
ink is chosen from a carbon ink, a silver ink and blends
thereof.
13. The patient delivery tube of claim 12, wherein said conductive
ink is a carbon ink having a resistivity ranging from about 25 to
about 500 ohms per square cm at 15 microns dried film
thickness.
14. The patient delivery tube of claim 12, wherein said conductive
ink comprises a blend of carbon and silver inks having a
resistivity ranging from about 0.05 to about 25 ohms per square cm
at 15 microns dried film thickness.
15. A method of delivering a heated, humidified gas to a patient
comprising: (a) placing a patient delivery tube in communication
with an airway of a patient; the patient delivery tube comprising
an elongated tubing member molded from a flexible polymer, the
elongated tubing member comprising a first end, a second end and at
least one axially aligned passageway extending therethrough; and an
electric heater comprising a conductive material, the electric
heater arranged along the axially aligned passageway for
perimetrically heating the axially aligned passageway; (b)
delivering a heated, humidified gas to the patient delivery
tube
16. The method of claim 15, wherein the flexible polymer is chosen
from polyethylene, polypropylene, polyester, and copolymers and
terpolymers thereof.
17. The method of claim 16, wherein the elongated tubing member
further comprises first and second lumens, the first and second
lumens positioned so as to at least partially surround the axially
aligned passageway.
18. The method of claim 17, wherein the conductive material of the
electrical heater comprises a conductive gel, the conductive gel
contained within at least one of the first and second lumens of the
elongated tubing member.
19. The method of claim 18, wherein the conductive gel is formed by
dispersing a plurality of conductive particles within a gelatinous
dielectric medium.
20. The method of claim 19, wherein the conductive particles are
chosen from silver-coated nickel particles, silver-coated glass
particles, carbon particles, silver spheres, silver flakes and
mixtures thereof.
21. The method of claim 20, wherein the gelatinous dielectric
medium comprises silicone gel.
22. The method of claim 16, wherein the elongated tubing member is
a single lumen tube having an outer surface.
23. The method of claim 22, wherein the conductive material
comprises a conductive ink, the conductive applied to the outer
surface of the elongated tubing member.
24. The method of claim 22, further comprising an elongated
protective cover, wherein the elongated protective cover is
positioned over the outer surface of the elongated tubing
member.
25. The method of claim 24, wherein at least one conductive ink is
a positive temperature coefficient ink.
26. The method of claim 24, wherein at least one conductive ink is
chosen from a carbon ink, a silver ink and blends thereof.
27. The method of claim 26, wherein at least one conductive ink is
a carbon ink having a resistivity ranging from about 25 to about
500 ohms per square cm at 15 microns dried film thickness.
28. The method of claim 26, wherein the conductive ink comprises a
blend of carbon and silver inks having a resistivity ranging from
about 0.05 to about 25 ohms per square cm at 15 microns dried film
thickness.
29. The method of claim 26, wherein the heated, humidified gas
comprises oxygen.
30. The method of claim 26, wherein the heated, humidified gas
comprises oxygen and air.
Description
[0001] The present invention relates to an apparatus and method for
respiratory tract therapy. More particularly, this invention
relates to an apparatus adapted to heat and humidify air and to
deliver heated and humidified air to the respiratory tract of a
human patient.
[0002] Oxygen therapy is a key treatment in respiratory care. Such
therapy serves to increase oxygen saturation in tissues where the
saturation levels are too low due to illness or injury. Some of the
conditions in which oxygen therapy is used include hypoxemia,
severe respiratory distress (e.g., acute asthma or pneumonia),
severe trauma, acute myocardial infarction and short-term therapy,
such as post-anesthesia recovery. Hyperbaric oxygen therapy is used
in cases of gas gangrene, decompression sickness, air embolism,
smoke inhalation, carbon monoxide poisoning and cerebral hypoxic
events.
[0003] In the delivery of oxygen and oxygen-enriched air, it is
recognized that significant discomfort is often experienced by the
patient, especially when the air is delivered over an extended
period of time. Moreover, it is generally known that it is far more
beneficial for the patient to receive such gases under conditions
of somewhat elevated heat and humidity, rather than to supply the
patient with a cool dry gas. It has also been recognized that the
delivery of air having relatively low absolute humidity can result
in respiratory irritation It has been found, for example, that when
the inhaled gas is both heated and humidified, the patient is more
receptive to the gas, with other potential respiratory diseases
minimized.
[0004] One example is rhinitis, which can be caused by viral
infections such as the common cold, influenza and allergies.
Rhinitis can also be caused by failure of the nasal defense system
as the result of, for example, cystic fibrosis. The nasal defense
system utilizes a layer of mucus that traps particles such as
bacteria. Tiny cilia hairs on the cells of mucous membrane move the
mucus with trapped particles to the back of the nose where it
enters the throat and is swallowed. If this system fails because
the mucus is insufficient or too thick, bacterial infection and
inflammation can result.
[0005] The introduction of heated and humidified air into the
respiratory tract helps to treat rhinitis by the thinning of mucus,
which leads to improved secretion clearance. Also, high humidity
promotes the healing of inflamed mucus-producing and ciliated
cells. Also, high temperature is believed to reduce the rate of
viral replication. Accordingly, breathing of heated and humidified
air can be a beneficial treatment for many types of rhinitis.
[0006] Asthma remains a serious and growing public health problem.
Asthma is not considered to be curable, and the treatment of asthma
consists largely of attempts at control. The process underlying
asthma appears to be inflammatory leading to hyper-reactivity of
the airways when they constrict in response to a variety of
stimuli. Although inhaled medications have been proposed to reduce
inflammation and to relax the bronchial muscle directly, there have
been concerns raised over abuse of the medications and the
side-effects associated with such medications. Recently, it has
been suggested that the delivery of warm humid air to the entire
respiratory tract can be of benefit to asthma sufferers, without
the risk and side-effects of the drugs in present use.
[0007] In the delivery of heated and humidified air to a patient,
it may be desirable to reduce the precipitation of water and
maintain a suitable air temperature In this regard, electrically
heated hoses have been used to add additional heat to the flowing
air, counteracting the heat lost along the length of the hose.
Conventional electrically heated hoses or tubing employ a heating
element, in the form of a solid or stranded resistance wire, which
is either embedded in the wall or wound around the circumference of
the hose. In some cases, the resistance wire is spirally wrapped
around a supporting thread before it is wrapped around the hose.
These hoses apply heat at the walls, which is communicated to the
fluid passing within the hose by convection. Alternatively, the
heating element may be loosely strung within the lumen of the hose.
In this case, heat is conducted to the fluid passing within the
lumen from the heating element through insulation placed over the
heating element.
[0008] A problem particular to spirally wound heater wire elements
is the formation of localized hot spots from variations in power
density. The variation in power density is caused by inconsistency
of the spiral pitch over a short section of the element. The
winding pitch seems to be particularly difficult for manufacturers
of this element to maintain and necessitates specialized testing
and equipment to detect in a high speed extrusion operation. This
localized hot spot can melt through the hose wall and pose a fire
threat.
[0009] One design proposed to overcome these problems includes a
flexible ribbon that spans the width of a flexible tubing and
extends generally through the length of the tubing, the flexible
ribbon carrying a heating element. The heating element proposed is
an electrically conductive wire or plurality of wires, connected to
a power supply in order to heat the flow of gas traveling within
the tube. The flow is heated as it passes over and around the
heating element. The flexible ribbon supporting the heating element
can be integral with the tubing or comprise an insertable unit
which fits into the tubing.
[0010] The U S. Food and Drug Administration has issued a Safety
Alert detailing the hazards of heated-wire breathing circuits. In
this Alert, the FDA notes that it has learned of instances in which
improperly used heated-wire breathing circuits have overheated,
softened, or melted, causing diminished gas delivery, fires and
burns to patients and caregivers.
[0011] In response to the aforementioned problems associated with
heated-wire breathing circuits, a number of heated-water breathing
circuits have been proposed. One such device includes a tubing
assembly for delivering a gas to a patient from a supply unit
having a gas outlet, a fluid outlet, and a fluid inlet, the tubing
assembly including a tube having a gas passage to deliver gas
toward a patient and a fluid passage to circulate heated fluid and
transfer heat to gas in the gas passage. However, it must be noted
that a direct interface between water and air must be avoided in
such a system so that the output gas is substantially free of
bacteria, viruses and allergens.
[0012] As such, there remains a need for an improved patient
delivery tube and apparatus for respiratory tract therapy that
overcomes the problems associated with current designs.
[0013] In one aspect, provided is a patient delivery tube for the
delivery of at least one of a heated gas and a humidified gas. The
patient delivery tube includes an elongated tubing member molded
from a flexible polymer, the elongated tubing member comprising a
first end, a second end and at least one axially aligned passageway
extending therethrough and an electric heater comprising a
conductive material, the electric heater arranged along the axially
aligned passageway for perimetrically heating the axially aligned
passageway.
[0014] According to one aspect, the gas is heated. According to
another aspect, the gas is heated and humidified.
[0015] In another aspect, provided is a method of delivering at
least one of a heated gas and a humidified gas to a patient. The
method includes the steps of placing a patient delivery tube in
communication with an airway of a patient, the patient delivery
tube including an elongated tubing member molded from a flexible
polymer, the elongated tubing member comprising a first end, a
second end and at least one axially aligned passageway extending
therethrough and an electric heater comprising a conductive
material, the electric heater arranged along the axially aligned
passageway for perimetrically heating the axially aligned
passageway and delivering a heated, humidified gas to the patient
delivery tube.
[0016] The patient delivery tubes disclosed herein may be provided
with any number of lumens, including one, two, three, four or more
lumens, and may be of any cross-section, including substantially
circular, oval, octagonal, etc.
[0017] In one embodiment, the elongated tubing member includes
first and second lumens positioned so as to at least partially
surround the axially aligned passageway. The first and second
lumens are filled with a conductive gel, so as to form an electric
heater. The conductive gel may be formed by dispersing a plurality
of conductive particles within a gelatinous dielectric medium, the
conductive particles chosen from silver-coated nickel particles,
silver-coated glass particles, carbon particles, silver spheres,
silver flakes and mixtures thereof. The gelatinous dielectric
medium may comprise a silicone gel
[0018] In another embodiment, the elongated tubing member is a
single lumen tube having an outer surface. The conductive material
includes a conductive ink applied to the outer surface of the
elongated tubing member A protective cover may be positioned over
the outer surface of the elongated tubing member to insulate and
protect the heater of the patient delivery tube. The conductive ink
may be a positive temperature coefficient ink, capable of self
regulation Alternatively, the conductive ink may be chosen from a
carbon ink, a silver ink and blends thereof. When a carbon ink is
employed, such an ink may have a resistivity of between about 25 to
about 500 ohms per square cm at 15 microns dried film thickness.
When a blend of carbon and silver inks is employed, such an ink may
have a resistivity of between about 0.05 to about 25 ohms per
square cm at 15 microns dried film thickness.
[0019] These and other features will be apparent from the
description taken with reference to accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The invention is further explained in the description that
follows with reference to the drawings illustrating, by way of
non-limiting examples, various embodiments of the invention
wherein:
[0021] FIG. 1 is a partial perspective view of one embodiment of a
patient delivery tube, depicting a three lumen elongated tubing
member;
[0022] FIG. 2 is a cross-sectional end view of the patient delivery
tube of FIG. 1 taken along line 2-2 of FIG. 1;
[0023] FIG. 3 is a side view of a patient delivery tube assembly
employing the patient delivery tube of FIG. 1;
[0024] FIG. 4 is a partial perspective view of another embodiment
of a patient delivery tube, depicting another three lumen elongated
tubing member;
[0025] FIG. 5 is a cross-sectional end view of the patient delivery
tube of FIG. 4 taken along line 5-5 of FIG. 4;
[0026] FIG. 6 is a side view of a patient delivery tube assembly
employing the patient delivery tube of FIG. 4;
[0027] FIG. 7 is a partial perspective view of another embodiment
of a patient delivery tube, depicting a single lumen elongated
tubing member;
[0028] FIG. 8 is a cross-sectional end view of the patient delivery
tube of FIG. 7 taken along line 8-8 of FIG. 7; and
[0029] FIG. 9 is a side view of a patient delivery tube assembly
employing the patient delivery tube of FIG. 7.
[0030] Various aspects will now be described with reference to
specific embodiments selected for purposes of illustration. It will
be appreciated that the spirit and scope of the patient delivery
tube disclosed herein is not limited to the selected embodiments.
Moreover, it is to be noted that the figures provided herein are
not drawn to any particular proportion or scale, and that many
variations can be made to the illustrated embodiments. Reference is
now made to FIGS. 1-9, wherein like numerals are used to designate
like parts throughout.
[0031] Referring now to FIGS. 1 and 2, an exemplary embodiment of a
patient delivery tube 10 includes an elongated tubing member 12
molded from a flexible polymer. Elongated tubing member 12 includes
a first end 14, a second end 16 and an axially aligned passageway
18, extending therethrough. Elongated tubing member 12 also
includes an electric heater 20 comprising a conductive material 22.
As shown, electric heater 20 is arranged along the axially aligned
passageway 18 for perimetrically heating axially aligned passageway
18
[0032] Referring now to FIG. 3, a patient delivery tube assembly 30
that employs patient delivery tube 10 is shown. Patient delivery
tube assembly 30 is utilized for delivering a heated, humidified
gas from an apparatus 40 capable of providing heated, humidified
air, oxygen or an air/oxygen blend. The air, oxygen or an
air/oxygen blend is supplied by apparatus 40 to patient delivery
tube assembly 30 via gas tube 42. Gas tube 42 includes a connector
44 for receiving patient delivery tube connector 32 of patient
delivery tube assembly 30. As shown, a first patient delivery tube
connector 32 mates with first end 14 of elongated tubing member 12
of patient delivery tube 10. A second patient delivery tube
connector 34 mates with second end 16 of the elongated tubing
member 12 for connection via connector 46, for example, to a
conventional nasal cannula (not shown) for receipt by a patient. As
will be described in more detail below, the patient delivery tube
10 is adapted to heat the gas as it is delivered to the respiratory
tract of a patient.
[0033] As indicated above, the elongated tubing member includes an
axially aligned passageway 18, or gas lumen, which is defined by
the elongated tubing member 12 and runs from the first end 14,
which serves as the gas inlet, to the second end 16, which serves
as the gas outlet. The elongated tubing member 12 also includes an
electric heater 20 that comprises a conductive material 22. As
shown, conductive material 22 of electric 20 is contained within
first lumen 24 and second lumen 26, with first lumen 24 and second
lumen 26 positioned so as to at least partially surround the
axially aligned passageway 18.
[0034] Conductive material 22 of electrical heater 20 includes a
conductive gel-like material. As is known by those skilled in the
art, a conductive gel is formed by dispersing a plurality of
conductive particles within a gelatinous dielectric medium. In
order to form a fully conductive gel, the concentration of the
conductive particles in the dielectric medium should be at least
equal to or above the percolation threshold; the percolation
threshold being the lower limit of a volumetric concentration of
randomly distributed conductive particles within a dielectric
medium which would result in bulk conductivity. The conductivity
threshold is generally on the order of 20 to 25% by volume of the
conductive particles in a dielectric medium. The concentration of
conductive particles may be between about 25 and about 30%, by
volume of conductive gel. Nevertheless, it should be noted that
anisotropic, or unidirectional conductivity may be achieved in thin
films by limiting the concentration of the conductive particles to
the order of about 10% by volume.
[0035] Overall properties of the conductive gel are attributable to
the dielectric medium employed. This dielectric medium may be
selected so that the conductive gel will exhibit a certain
memory-like viscosity. The dielectric gel may also tend to
self-heal and return to its original shape. The conductive gel may
be conformable to the interface between the connectors 32 and 34
and the electrical conductors 36 and 38. In other words, the
gelatinous dielectric medium may form a coherent nonflowable
mass.
[0036] While a wide variety of gels are available that would have
utility in the patient delivery tube 10 disclosed herein, silicone
gels exhibit the physical characteristics described hereinabove.
One such silicone gel is a dielectric two-component transparent
silicone encapsulant specifically marketed under the trademark
Sylgard.RTM. 527 by Dow Corning Corporation of Midland, Mich. When
the two components of this material are mixed in a one-to-one
ratio, the consequent material forms a cushioning, self-healing,
resilient gel-like mass. This gel has some of the stress relief and
self-healing properties of a liquid but is dimensionally stable and
nonflowing, enabling the conductive particles to remain uniformly
distributed within the gel. The material is hydrophobic and forms a
seal with the electrical conductors 36 and 38, inserted therein.
The material is deformable and will conform to the contours of the
first lumen 24 and second lumen 36 into which it is deposited, as
well as conforming to the interface with conductors 36 and 38,
inserted into engagement therewith.
[0037] The conductive particles distributed within the gel to form
the conductive gel of conductive material 22 can comprise any of a
number of conventionally available conductive particles. For
purposes of example and not by way of limitation, silver-coated
nickel particles, silver-coated glass particles, solid silver
spheres, silver flakes, carbon particles or mixtures thereof, can
be employed.
[0038] Referring still to FIG. 3, in use current is applied to
conductors 36 and 38 of a first patient delivery tube connector 32
and second patient delivery tube connector 34, respectively, of
patient delivery tube assembly 30. As described above, conductors
36 and 38 are in electrical communication with the conductive
material 22 contained within first lumen 24 and second lumen 26 of
heater 20 and produces heat as current is applied thereto. The heat
so produced is thereby transferred from the heater 20 to the gas in
the axially aligned passageway 18, so as to deliver heated and
humidified air to the respiratory tract of a patient.
[0039] The patient delivery tube 10 described herein may be
employed with an apparatus that provides a source for heated,
and/or humidified air, oxygen or blends thereof, such as apparatus
40. Such an apparatus may be adapted for use in a variety of
settings and for transport between locations. The apparatus 40 may
be used in the home by a patient and at the patient's bedside, if
desired. The apparatus 40 can also be used in hospitals, clinics,
and other settings, as well. An apparatus 40 capable of supplying
humidified air is known in the art
[0040] The patient delivery tube assembly 30 may be designed so
that it can be used by a particular patient and then discarded
after one or any number of uses. The patient delivery tube assembly
30 provides a passageway for the flow of humidified air to the
patient's respiratory tract. The patient delivery tube assembly 30
may be connected to a nasal cannula (not shown) that extends from
patient delivery tube assembly 30 to the patient's respiratory
tract during use. Nasal cannula and associated fittings used for
supplying air to the nares of a patient are readily available
components that are well known in the art.
[0041] Patient delivery tube 10 can be formed from a variety of
materials and by a variety of processes Patient delivery tube 10
may be formed from a polymeric material such as polyurethane,
polyethylene, polypropylene, polyester and copolymers, terpolymers
and blends thereof. Patient delivery tube 10 may be formed from a
polyetherurethane, such as Pellethane.RTM. 2363-80AE, which has a
durometer of Shore 80A. Pellethane.RTM. is available from The Dow
Chemical Company of Midland, Mich. According to various embodiments
patient delivery tube 10 is clear to permit a degree of
visualization and enable a user to ascertain that sufficient heat
is being applied so that no condensation occurs. Patient delivery
tube 10 is suitably extruded in long lengths having a substantially
constant cross-sectional shape. Although various lengths are
contemplated for patient delivery tube 10, a length of about 10
feet will provide adequate performance and adequate versatility to
the patient. Other lengths are of course contemplated, depending on
specific circumstances, the length of nasal cannula, heat transfer
characteristics and matters of cost and design choice.
[0042] In operation, gas (air, oxygen, or some combination) is
supplied to the apparatus 40 via a tube (not shown) at about 50 psi
maximum pressure. The gas flow can be regulated by a user-supplied
restricting valve at the source of the gas so that it can be
controlled between flows of about 5 to about 50 l/min, or between
about 5 to about 40 l/min A patient delivery tube assembly 30 can
be attached at the front of the apparatus 40 via a manifold (not
shown) that interfaces to a gas supply port. The apparatus 40 can
be designed to operate on standard 115VAC, 60 Hz. A standard
hospital grade power cord can be supplied with the unit. The
apparatus 40 can also employ a microprocessor to control heating,
gas flow, gas pressure, humidification, etc., as those skilled in
the art can readily understand.
[0043] The apparatus 40 is adapted to operate within predetermined
parameters. In one exemplary embodiment, the apparatus can operate
in a controlled air output temperature range of from about
35.degree. C. to about 43.degree. C.; an operating flow range of
about 5 to about 40 l/min; a gas pressure not to exceed about 60
psi; and a gas composition of dry air and/or oxygen, from about 21%
O.sub.2 to about 100% O.sub.2. According to various embodiments,
gas humidification exceeds about 95% relative humidity.
[0044] Referring now to FIGS. 4 and 5, another exemplary embodiment
of a patient delivery tube 100 includes an elongated tubing member
112 molded from a flexible polymer. Elongated tubing member 112
includes a first end 114, a second end 116 and an axially aligned
passageway 118, extending therethrough. Elongated tubing member 112
also includes an electric heater 120 comprising a conductive
material 122. As shown, electric heater 120 is arranged along the
axially aligned passageway 118 for perimetrically heating axially
aligned passageway 118.
[0045] Referring specifically now to FIG. 5, which provides a
cross-sectional end view of elongated tubing member 112, further
details of patient delivery tube 100 will now be described. Patient
delivery tube 100 includes a substantially circular outer wall 160
spaced concentrically around a substantially circular inner wall
162. Boundary walls 152 extend from the inner surface of outer wall
160 to the outer surface of inner wall 162. A plurality of
longitudinally extending ribs 154 extends radially inwardly from
the inner surface of inner wall 162 and along the axis of elongated
tubing member 112.
[0046] Inner wall 162 and ribs 154 together serve to define axially
aligned passageway 118 that extends along the length of elongated
tubing member 112. In the embodiment illustrated in FIG. 5, six
ribs 154 are uniformly spaced. Ribs 154 additionally serve to
prevent constriction of axially aligned passageway 118 in the event
that elongated tubing member 112 is bent in use or otherwise kinked
unintentionally. Outer wall 160 and inner wall 162 together define
with boundary walls 152 a first lumen 124 and a second lumen 126
that have a substantially arcuate cross-sectional shape and that
substantially surround axially aligned passageway 118.
[0047] Referring now to FIG. 6, a patient delivery tube assembly
130 that employs patient delivery tube 100 is shown. Patient
delivery tube assembly 130 is utilized for delivering a heated,
humidified gas from an apparatus 140 capable of providing heated
and/or humidified air, oxygen or an air/oxygen blend. The air,
oxygen or an air/oxygen blend is supplied by apparatus 140 to
patient delivery tube assembly 130 via gas tube 142. Gas tube 142
includes a connector 144 for receiving patient delivery tube
connector 132 of patient delivery tube assembly 130. According to
another embodiment (not shown), connector 132 is inserted directly
into apparatus 140. As shown, a first patient delivery tube
connector 132 mates with first end 114 of elongated tubing member
112 of patient delivery tube 100. A second patient delivery tube
connector 134 mates with second end 116 of the elongated tubing
member 112 for connection via connector 146, for example, to a
conventional nasal cannula (not shown) for receipt by a patient. As
will be described in more detail below, the patient delivery tube
100 is adapted to heat the gas as it is delivered to the
respiratory tract of a patient.
[0048] The elongated tubing member includes an axially aligned
passageway 118, or gas lumen, which is defined by the elongated
tubing member 112 and runs from the first end 114, which serves as
the gas inlet, to the second end 16, which serves as the gas
outlet. The elongated tubing member 112 also includes an electric
heater 120 that comprises a conductive material 122 As shown,
conductive material 122 of electric 120 is contained within first
lumen 124 and second lumen 126, with first lumen 124 and second
lumen 126 positioned so as to at least partially surround the
axially aligned passageway 118.
[0049] As with the embodiment depicted in FIGS. 1-3, conductive
material 122 of electrical heater 120 includes a conductive
gel-like material formed by dispersing a plurality of conductive
particles within a gelatinous dielectric medium. In order to form a
fully conductive gel, the concentration of the conductive particles
in the dielectric medium should be at least equal to or above the
percolation threshold; the percolation threshold being the lower
limit of a volumetric concentration of randomly distributed
conductive particles within a dielectric medium which would result
in bulk conductivity. The conductivity threshold is generally on
the order of 20 to 25% by volume of the conductive particles in a
dielectric medium. The concentration of conductive particles may be
between about 25 and about 30%, by volume of conductive gel.
[0050] Overall properties of the conductive gel are attributable to
the dielectric medium employed. This dielectric medium may be
selected so that the conductive gel will exhibit a certain
memory-like viscosity. The dielectric gel may also tend to
self-heal and return to its original shape. The conductive gel may
be conformable to the interface between the connectors 132 and 134
and the electrical conductors 136 and 138. In other words, the
gelatinous dielectric medium may form a coherent nonflowable
mass.
[0051] While a wide variety of gels are available that would have
utility in the patient delivery tube 100 disclosed herein, silicone
gels exhibit the physical characteristics described hereinabove.
One such silicone gel, is a dielectric two-component transparent
silicone encapsulant specifically marketed under the trademark
Sylgard.RTM. 527 by Dow Corning Corporation of Midland, Mich. When
the two components of this material are mixed in a one-to-one
ratio, the consequent material forms a cushioning, self-healing,
resilient gel-like mass. This gel has some of the stress relief and
self-healing properties of a liquid but is dimensionally stable and
nonflowing, enabling the conductive particles to remain uniformly
distributed within the gel. The material is hydrophobic and forms a
seal with the electrical conductors 136 and 138, inserted therein.
The material is deformable and will conform to the contours of the
first lumen 124 and second lumen 136 into which it is deposited, as
well as conforming to the interface with conductors 136 and 138,
inserted into engagement therewith.
[0052] The conductive particles distributed within the gel to form
the conductive gel of conductive material 122 can comprise any of a
number of conventionally available conductive particles. For
purposes of example and not by way of limitation, silver-coated
nickel particles, silver-coated glass particles, solid silver
spheres, silver flakes, carbon particles or mixtures thereof, can
be employed.
[0053] Still referring to FIG. 6, in use, current is applied to
conductors 136 and 138 of a first patient delivery tube connector
132 and second patient delivery tube connector 134, respectively,
of patient delivery tube assembly 130. As described above,
conductors 136 and 138 are in electrical communication with the
conductive material 122 contained within first lumen 124 and second
lumen 126 of heater 120 and produces heat as current is applied
thereto. The heat so produced is thereby transferred from the
heater 120 to the gas in the axially aligned passageway 118, so as
to deliver heated and humidified air to the respiratory tract of a
patient. This arrangement can provide highly efficient heat
transfer from the heater 120 to the flowing gas or air.
[0054] The patient delivery tube 100 described herein may be
employed with an apparatus that provides a source for heated,
humidified air, oxygen or blends thereof such as apparatus 140.
Such an apparatus may be adapted for use in a variety of settings
and for transport between locations. The apparatus 140 may be used
in the home by a patient and at the patient's bedside, if desired.
The apparatus 140 can also be used in hospitals, clinics, and other
settings, as well.
[0055] The patient delivery tube assembly 130 may be designed so
that it can be used by a particular patient and then discarded
after one or any number of uses. The patient delivery tube assembly
130 provides a passageway for the flow of humidified air to the
patient's respiratory tract. The patient delivery tube assembly 130
may be connected to a nasal cannula (not shown) that extends from
patient delivery tube assembly 130 to the patient's respiratory
tract during use. Nasal cannula and associated fittings used for
supplying air to the nares of a patient are readily available
components that are well known in the art.
[0056] Patient delivery tube 100 can be formed from a variety of
materials and by a variety of processes. Patient delivery tube 100
may be formed from a polymeric material such as polyurethane,
polyethylene, polypropylene, polyester and blends thereof. Patient
delivery tube 100 may be formed from a polyetherurethane, such as
Pellethane.RTM. 2363-80AE, which has a durometer of Shore 80A.
Pellethane.RTM. is available from The Dow Chemical Company of
Midland, Mich. Patient delivery tube 100 is preferably clear to
permit some visualization and enable a user to ascertain that
sufficient heat is being applied so that no condensation occurs.
Patient delivery tube 100 is preferably extruded in long lengths
having a substantially constant cross-sectional shape. Although
various lengths are contemplated for patient delivery tube 100, a
length of about 10 feet will provide adequate performance and
adequate versatility to the patient. Other lengths are of course
contemplated, depending on specific circumstances, the length of
nasal cannula, heat transfer characteristics and matters of cost
and design
[0057] In operation, gas (air, oxygen, or some combination) is
supplied to the apparatus 140 via a tube (not shown) at about 50
psi maximum pressure. The gas flow can be regulated by a
user-supplied restricting valve at the source of the gas so that it
can be controlled between flows of about 5 to 50 l/min, or between
about 5 to 40 l/min. A patient delivery tube assembly 130 can be
attached at the front of the apparatus 140 via a manifold (not
shown) that interfaces to a gas supply port. The apparatus 140 can
be designed to operate on standard 115VAC, 60 Hz. A standard
hospital grade power cord can be supplied with the unit. The
apparatus 140 can also employ a microprocessor to control heating,
humidification, gas flow, gas pressure, etc., as those skilled in
the art can readily understand.
[0058] The apparatus 140 is adapted to operate within predetermined
parameters. In one exemplary embodiment, the apparatus can operate
in a controlled air output temperature range of from about
35.degree. C. to about 43.degree. C.; an operating flow range of
about 5 to about 40 l/min.; a gas pressure not to exceed about 60
psi; and a gas composition of dry air and/or oxygen, from about 21%
O.sub.2 to about 100% O.sub.2. According to various embodiments, as
humidification exceeds about 95% relative humidity.
[0059] Referring now to FIGS. 7 and 8, an exemplary embodiment of a
patient delivery tube 200 includes an elongated tubing member 212
molded from a flexible polymer. Elongated tubing member 212
includes a first end 214, a second end 216 and an axially aligned
passageway 218, extending therethrough. Elongated tubing member 212
also includes an electric heater 220 comprising a conductive
material 270. As shown, electric heater 220 is arranged along the
axially aligned passageway 218 for perimetrically heating axially
aligned passageway 218.
[0060] Referring now to FIG. 9, a patient delivery tube assembly
230 that employs patient delivery tube 200 is shown. Patient
delivery tube assembly 230 is utilized for delivering a heated,
humidified gas from an apparatus 240 capable of providing heated
and/or humidified air, oxygen or an air/oxygen blend. The air,
oxygen or an air/oxygen blend is supplied by apparatus 240 to
patient delivery tube assembly 230 via gas tube 242. Gas tube 242
includes a connector 244 for receiving patient delivery tube
connector 232 of patient delivery tube assembly 230. As shown, a
first patient delivery tube connector 232 mates with first end 214
of elongated tubing member 212 of patient delivery tube 200. A
second patient delivery tube connector 234 mates with second end
216 of the elongated tubing member 212 for connection via connector
246, for example, to a conventional nasal cannula (not shown) for
receipt by a patient. As will be described in more detail below,
the patient delivery tube 200 is adapted to heat the gas as it is
delivered to the respiratory tract of a patient.
[0061] As indicated above, the elongated tubing member includes an
axially aligned passageway 218, or gas lumen, which is defined by
the elongated tubing member 212 and runs from the first end 214,
which serves as the gas inlet, to the second end 16, which serves
as the gas outlet. The elongated tubing member 212 also includes an
electric heater 220 that comprises a conductive material 270.
[0062] In the embodiment depicted in FIGS. 7-9, the conductive
material 270 comprises a conductive ink, which will be explained in
more detail below. As shown, conductive material 270 of electric
heater 220 is applied to outer surface 260 of elongated tubing
member 212, so as to at least partially or fully surround the
axially aligned passageway 218. A wide variety of conductive inks
have utility in the fabrication of electric heater 220.
Carbon-based inks, silver-based inks and mixtures thereof may be
employed. Positive temperature coefficient (PTC) inks may also be
employed in cases where it is desirable that heater 220 regulates
itself. PTC inks can accomplish this since the resistance of the
ink increases as the temperature rises, thus reducing the power
density. PTC inks are usually based on highly crystalline resins
such as fluoropolymers. Such inks are available from Coates, a
division of Sun Chemical Corporation, of Parsippany, N.J., Dow
Corning Corporation of Midland, Mich. and other sources.
[0063] With regard to the design of heater 220, it should be noted
that the more electrically resistive the ink, the more difficult it
is to manufacture. Greater fluctuations in current density are also
likely with very resistive inks. As such, the blending of different
inks can serve to obtain the desired resistance. Very resistive
inks are also more likely to fail due to tracking; a condition
where a favored electrical path results in a very high local
current density and breakdown. Typical resistivities for carbon
inks are from about 25 to about 500 ohms per square unit at 15
microns dried film thickness (DFT). More conductive inks can be
made with a blend of carbon and silver inks ranging from about 0.05
to about 25 ohms per square unit.
[0064] A highly conductive silver ink, such as is available from
Dow Corning of Midland, Mich., may also be employed. Such inks are
available in both thermoset and thermoplastic forms that
incorporate bis-A polymers and are highly filled with silver to
enhance conductivity. These inks may be applied by screen-printing
and other techniques. Within the thermosetting inks, additives are
used that act upon the silver particles to increase the
particle-to-particle contact. The thermoplastic inks use additives
to achieve a tighter structure and more intimate
particle-to-particle contact. Each result in high electrical
conductivity levels.
[0065] A flexible tubular cover 280 can be installed over the
conductive ink coated outer surface 260 of elongated tubing member
212 to insulate and protect electric heater 220. PTC inks should be
covered with a material that has a similar coefficient of thermal
expansion as the ink itself.
[0066] Still referring to FIG. 9, the electrodes 236 and 238 may be
formed from a material such as copper or silver. Copper has the
advantage in both conductivity and solderability, although silver
can be applied as an ink, and may therefore be more cost effective.
In use, current is applied to conductors 236 and 238 of a first
patient delivery tube connector 232 and second patient delivery
tube connector 234, respectively, of patient delivery tube assembly
230. As described above, conductors 236 and 238 are in electrical
communication with the conductive material 270 of heater 220 and
produces heat as current is applied thereto. The heat so produced
is thereby transferred from the heater 220 to the gas in the
axially aligned passageway 218, so as to deliver heated and
humidified air to the respiratory tract of a patient.
[0067] The patient delivery tube 200 described herein may be
employed with an apparatus that provides a source for heated,
humidified air, oxygen or blends thereof, such as apparatus 240.
Such an apparatus may be adapted for use in a variety of settings
and for transport between locations. The apparatus 240 may be used
in the home by a patient and at the patient's bedside, if desired.
The apparatus 240 can also be used in hospitals, clinics, and other
settings, as well.
[0068] The patient delivery tube assembly 230 may be designed so
that it can be used by a particular patient and then discarded
after one or any number of uses. The patient delivery tube assembly
230 provides a passageway for the flow of humidified air to the
patient's respiratory tract. The patient delivery tube assembly 230
may be connected to a nasal cannula (not shown) that extends from
patient delivery tube assembly 230 to the patient's respiratory
tract during use. Nasal cannula and associated fittings used for
supplying air to the nares of a patient are readily available
components that are well known in the art.
[0069] Patient delivery tube 200 can be formed from a variety of
materials and by a variety of processes. Patient delivery tube 200
may be formed from a polymeric material such as polyurethane,
polyethylene, polypropylene, polyester and copolymers, terpolymers
and blends thereof. Patient delivery tube 10 may be formed from a
polyetherurethane, such as Pellethane.RTM. 2363-80AE, which has a
durometer of Shore 80A. Pellethane.RTM. is available from The Dow
Chemical Company of Midland, Mich. Patient delivery tube 200 is
preferably extruded in long lengths having a substantially constant
cross-sectional shape. Although various lengths are contemplated
for patient delivery tube 200, a length of about 10 feet will
provide adequate performance and adequate versatility to the
patient. Other lengths are of course contemplated, depending on
specific circumstances, the length of nasal cannula, heat transfer
characteristics and matters of cost and design choice.
[0070] In operation, gas (air, oxygen, or some combination) is
supplied to the apparatus 240 via a tube (not shown) at about 50
psi maximum pressure. The gas flow can be regulated by a
user-supplied restricting valve at the source of the gas so that it
can be controlled between flows of about 5 to 50 l/min, or between
about 5 to 40 l/min. A patient delivery tube assembly 230 can be
attached at the front of the apparatus 240 via a manifold (not
shown) that interfaces to a gas supply port. The apparatus 240 can
be designed to operate on standard 115VAC, 60 Hz. A standard
hospital grade power cord can be supplied with the unit. The
apparatus 240 can also employ a microprocessor to control heating,
humidification, gas flow, gas pressure, etc., as those skilled in
the art can readily understand.
[0071] The apparatus 240 is adapted to operate within predetermined
parameters. In one exemplary embodiment, the apparatus can operate
in a controlled air output temperature range of from about
35.degree. C. to about 43.degree. C.; an operating flow range of
about 5 to about 40 l/min.; a gas pressure not to exceed about 60
psi; and a gas composition of dry air and/or oxygen, from about 21%
O.sub.2 to about 100% O.sub.2. Gas humidification should preferably
exceed about 95% relative humidity.
[0072] The patient delivery tubes disclosed herein can yield
significant benefits when used for the treatment of the respiratory
tract or for respiratory tract therapy. The patient delivery tubes
disclosed herein can be uniquely adapted for the introduction of
heated and humidified air to the respiratory tract of a human
patient. Home use, hospital and clinical use are contemplated.
[0073] The introduction of heated and humidified air by using the
patient delivery tubes disclosed herein can provide several unique
advantages as compared to conventional humidifiers in connection
with the treatment of rhinitis and other respiratory tract
conditions. The use of a temperature-controlled patient delivery
tube of the type disclosed herein can ensure that saturated air is
delivered to the nose at body temperature or higher without heat
loss or condensation, and a high flow rate of heated and humidified
air ensures that almost all of the air breathed by a patient is
heated and humidified with little or no entrained room air. These
benefits can be accomplished by delivering air through a nasal
cannula so that the patient can continue normal activities with
minimal interference.
[0074] The patient delivery tubes disclosed herein can provide
relief to people who suffer from asthma. Conventionally, asthma
sufferers are recommended to keep humidity low because dust mites
are more common in moist environments Accordingly, the system
according to this invention provides the benefits of warm humid air
in the entire respiratory tract without the problems associated
with high ambient humidity
[0075] A supply of room air saturated with water vapor at about
40.degree. C. directly to the airway via a nasal cannula, thereby
avoiding problems of condensation and cooling associated with
conventional delivery of humidified air, reduces nasal irritation
by eliminating drying and cooling of the nasal mucosa and pharynx,
and is therefore therapeutic for asthma and rhinitis. More
specifically, a patient may be fitted with a nasal cannula, and air
is delivered to the patient at a flow rate of up to about 20 liters
or more per minute at about 40.degree. C., wherein the air is about
100% humidified.).
[0076] All patents, test procedures, and other documents cited
herein, including priority documents, are fully incorporated by
reference to the extent such disclosure is not inconsistent with
this invention and for all jurisdictions in which such
incorporation is permitted.
[0077] While the illustrative embodiments of the invention have
been described with particularity, it will be understood that
various other modifications will be apparent to and can be readily
made by those skilled in the art without departing from the spirit
and scope of the invention. Accordingly, it is not intended that
the scope of the claims appended hereto be limited to the examples
and descriptions set forth herein but rather that the claims be
construed as encompassing all the features of patentable novelty
which reside in the invention, including all features which would
be treated as equivalents thereof by those skilled in the art to
which the invention pertains.
* * * * *