U.S. patent application number 11/937898 was filed with the patent office on 2008-11-27 for apparatus and method for respiratory tract therapy.
Invention is credited to Owen S. Bamford, Dirk Ten Broeck, Felino V. Cortez, JR., William F. Niland, Gary Schroeder.
Application Number | 20080289631 11/937898 |
Document ID | / |
Family ID | 22619012 |
Filed Date | 2008-11-27 |
United States Patent
Application |
20080289631 |
Kind Code |
A1 |
Schroeder; Gary ; et
al. |
November 27, 2008 |
APPARATUS AND METHOD FOR RESPIRATORY TRACT THERAPY
Abstract
An apparatus is provided for delivering heated and humidified
air to the respiratory tract of a human patient for respiratory
tract therapy and treatment. The apparatus includes a supply unit
and a delivery tube that can be releasably connected to the supply
unit. Methods of respiratory tract therapy and treatment are also
provided.
Inventors: |
Schroeder; Gary;
(Londonderry, NH) ; Broeck; Dirk Ten; (Nashua,
NH) ; Bamford; Owen S.; (Linthicum Heights, MD)
; Niland; William F.; (Arnold, MD) ; Cortez, JR.;
Felino V.; (Bowie, MD) |
Correspondence
Address: |
Joshua L. Cohen;Ratner & Prestla
Suite 301, One westlakes , Berwyn, P.O. Box 980
Valley Forge
PA
19482-0980
US
|
Family ID: |
22619012 |
Appl. No.: |
11/937898 |
Filed: |
November 9, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10149356 |
Jan 29, 2003 |
7314046 |
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PCT/US00/33346 |
Dec 8, 2000 |
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11937898 |
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60170213 |
Dec 10, 1999 |
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Current U.S.
Class: |
128/204.17 |
Current CPC
Class: |
A61M 16/1075 20130101;
A61M 16/109 20140204; A61M 16/16 20130101; A61M 16/1095 20140204;
A61M 16/0808 20130101; A61M 16/107 20140204; A61M 2016/0027
20130101; A61M 2205/3368 20130101; A61M 16/1055 20130101; A61M
16/0841 20140204; A61M 16/145 20140204; A61M 16/026 20170801; A61M
16/162 20130101; A61M 16/0666 20130101 |
Class at
Publication: |
128/204.17 |
International
Class: |
A61M 16/10 20060101
A61M016/10 |
Claims
1. A tubing assembly for delivering gas to a patient from a supply
unit having a port defining a gas outlet, a fluid outlet, and a
fluid inlet, said tubing assembly comprising: a tube having a gas
passage to deliver gas toward a patient and a fluid passage to
circulate fluid and transfer heat to gas in the gas passage; a
fitting connected to said tube, said fitting having a gas inlet
oriented to provide gas flow between the gas outlet of the supply
unit and said gas passage of said tube, said fitting further
comprising a fluid inlet oriented to provide fluid flow between the
fluid outlet of the supply unit and said fluid passage of said
tube, and said fitting further comprising a fluid outlet oriented
to provide fluid flow between said fluid passage of said tube and
the fluid inlet of the supply unit; said fitting of said tubing
assembly being configured to provide flow communication between the
gas outlet, the fluid outlet, and the fluid inlet of the supply
unit and said gas passage and said fluid passage of said tube upon
insertion of said fitting of said tubing assembly into the port of
the supply unit.
2. The tubing assembly defined in claim 1, said fitting of said
tubing assembly being coupled to a proximal end of said tube.
3. The tubing assembly defined in claim 2, said tubing assembly
further comprising a supply fitting coupled to a distal end of said
tube.
4. The tubing assembly defined in claim 1, said gas passage of said
tube of said tubing assembly extending from a proximal end to a
distal end of said tube.
5. The tubing assembly defined in claim 1, said fluid passage of
said tube comprising a fluid supply passage extending from a
proximal end to a distal end of said tube and a fluid return
passage extending from said distal end to said proximal end of said
tube, said fluid passage being configured to circulate fluid from
said proximal end to said distal end of said tube through said
fluid supply passage and from said distal end to said proximal end
of said tube through said fluid return passage.
6. The tubing assembly defined in claim 5, said tubing assembly
defining a passage for fluid flow between said fluid supply passage
and said fluid return passage adjacent said distal end of said
tube.
7. The tubing assembly defined in claim 5, said fluid inlet of said
fitting of said tubing assembly being positioned for flow
communication with said fluid supply passage of said tube adjacent
said proximal end of said tube.
8. The tubing assembly defined in claim 7, said fluid outlet of
said fitting of said tubing assembly being positioned for flow
communication with said fluid return passage of said tube adjacent
said proximal end of said tube.
9. The tubing assembly defined in claim 1, said gas inlet of said
fitting of said tubing assembly extending axially for flow
communication with the gas outlet of the supply unit.
10. The tubing assembly defined in claim 1, said fluid inlet of
said fitting of said tubing assembly being configured for
longitudinal alignment with the fluid outlet of the supply
unit.
11. The tubing assembly defined in claim 1, said fluid outlet of
said fitting of said tubing assembly being configured for
longitudinal alignment with the fluid inlet of the supply unit.
12. The tubing assembly defined in claim 1, said fluid inlet of
said fitting of said tubing assembly extending radially for flow
communication with the fluid outlet of the supply unit.
13. The tubing assembly defined in claim 1, said fluid outlet of
said fitting of said tubing assembly extending radially for flow
communication with the fluid inlet of the supply unit.
14. The tubing assembly defined in claim 1, said fluid inlet and
said fluid outlet of said fitting of said tubing assembly extending
along a common axis oriented at an angle to the longitudinal axis
of said tube.
15. In combination with the tubing assembly defined in claim 1, a
supply unit configured to supply gas for delivery to a patient and
to supply fluid for heating the gas; said supply unit comprising a
port defining a gas outlet, a fluid outlet, and a fluid inlet, said
fitting of said tubing assembly being releasably engaged in said
port of said supply unit; said gas outlet of said supply unit being
in flow communication with said gas inlet of said fitting of said
tubing assembly; said fluid outlet of said supply unit being in
flow communication with said fluid inlet of said fitting of said
tubing assembly; and said fluid inlet of said supply unit being in
flow communication with said fluid outlet of said fitting of said
tubing assembly.
16. The combination defined in claim 15, said supply unit being
configured to humidify gas and to deliver humidified gas to said
gas outlet of said supply unit.
17. The combination defined in claim 15, said supply unit being
configured to heat fluid and to circulate heated fluid from said
fluid inlet of said supply unit to said fluid outlet of said supply
unit.
18. The combination defined in claim 15, said gas inlet of said
fitting of said tubing assembly and said gas outlet of said supply
unit extending along the longitudinal axis of said tube of said
tubing assembly.
19. The combination defined in claim 15, said fluid inlet and said
fluid outlet of said fitting of said tubing assembly extending
radially outwardly.
20. The combination defined in claim 19, said fitting of said
tubing assembly comprising a flange configured to engage a surface
of said port for rotation of said fitting into locking engagement
with said port, said fluid inlet and said fluid outlet of said
fitting of said tubing assembly being in flow communication with
said fluid outlet and said fluid inlet of said port, respectively,
upon said rotation of said fitting into locking engagement with
said port.
21. The combination defined in claim 15, said port of said supply
unit comprising valves to close said fluid inlet and said fluid
outlet upon removal of said fitting of said tubing assembly from
said port.
22. The combination defined in claim 21, said valves of said port
being configured to be opened upon insertion of said fitting of
said tubing assembly into said port, thereby permitting flow
communication between said fluid inlet and said fluid outlet of
said port and said fluid passage of said tubing assembly.
23. The combination defined in claim 15, said supply unit further
comprising a sensor mounted to detect the presence of liquid in gas
delivered to said gas outlet.
24. The combination defined in claim 23, said sensor being
configured to sense the intensity of a light beam generated through
the gas, wherein the presence of liquid in the gas decreases the
intensity of said light beam.
25. The combination defined in claim 23, said supply unit being
configured to prevent the delivery of gas to said gas outlet when
the presence of liquid is detected in the gas.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of U.S. patent
application Ser. No. 10/149,356 filed Jan. 29, 2003, which is a
U.S. National Stage Application of PCT Application No.
US2000/33346, filed Dec. 8, 2000, which claims priority from U.S.
Provisional Patent Application Ser. No. 60/170,213, filed Dec. 10,
1999.
FIELD OF THE INVENTION
[0002] This 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. This invention also relates to methods for
respiratory tract therapy.
BACKGROUND OF THE INVENTION
[0003] It has been recognized that the delivery of oxygen and
oxygen-enriched air to the respiratory tract of a patient often
results in discomfort to the patient, especially when the air is
delivered over an extended period of time. It has also been
recognized that the delivery of air having relatively low absolute
humidity can result in respiratory irritation.
[0004] Several devices have been proposed to overcome these
problems. U.S. Pat. No. 4,632,677, issued to Richard H. Blackmer,
the disclosure of which is incorporated herein by reference,
describes an oxygen-enriching apparatus including means for
increasing or regulating the humidity of the air. The Blackmer
apparatus employs an array of membrane cells, a vacuum pump to draw
a flow of humidity-and-oxygen-enriched air from each cell, low- and
high-temperature condensers connected to receive air drawn from the
cells, and a proportioning valve connected to the condensers for
providing a desired humidity level of the air.
[0005] According to the Blackmer '677 patent, air supplied to the
patient may be heated by circulation of warm air over delivery
tubing, use of electric resistance heaters, and circulating warm
liquid co-linearly with the delivery tubing. With regard to warm
liquid heating, warm water is circulated through a tubing jacket
comprised of feed and return tubes, which trace the delivery air
line, by means of a motor-driven pump. A feed tube extends from the
pump and a return tube connects to a water reservoir. Regarding
warm air circulation, a blower delivers warmed air to a tube which
co-axially surrounds the oxygen-enriched air delivery tubing.
Electrical resistance heating may also be used according to the
Blackmer '677 patent.
[0006] Another system is described in U.S. Pat. No. 4,773,410,
issued to Richard H. Blackmer et al., the disclosure of which is
incorporated herein by reference. The apparatus described by the
Blackmer et al. '410 patent includes a permeable membrane to permit
a liquid-vapor boundary, as well as means for delivering a
substantially condensation-free saturated vapor-gas stream to a
respiratory tract. In one embodiment described in the Blackmer et
al. '410 patent, the apparatus uses a delivery tube with electrical
heating elements that heat the air as it passes through the tube.
In another embodiment, a heater heats water which is then delivered
through a separate tube that is connected to the delivery tube near
the delivery tube's exit port. The heated water then flows
counter-current to the air flow to heat the air and exits the
delivery tube near its opposite end.
[0007] Nevertheless, there remains a need for an improved apparatus
for respiratory tract therapy that can be used in various settings
including clinical, hospital, and home settings. There also remains
a need for improved methods of respiratory tract therapy.
SUMMARY OF THE INVENTION
[0008] A tubing assembly is provided for delivering gas to a
patient from a supply unit having a port defining a gas outlet, a
fluid outlet, and a fluid inlet. The tubing assembly includes a
tube having a gas passage to deliver gas toward a patient and a
fluid passage to circulate fluid and transfer heat to gas in the
gas passage. The tubing assembly also includes a fitting connected
to the tube. The fitting has a gas inlet oriented to provide gas
flow between the gas outlet of the supply unit and the gas passage
of the tube. The fitting also includes a fluid inlet oriented to
provide fluid flow between the fluid outlet of the supply unit and
the fluid passage of the tube. Finally, the fitting further
includes a fluid outlet oriented to provide fluid flow between the
fluid passage of the tube and the fluid inlet of the supply unit.
The fitting of the tubing assembly is configured to provide flow
communication between the gas outlet, the fluid outlet, and the
fluid inlet of the supply unit and the gas passage and the fluid
passage of the tube upon insertion of the fitting of the tubing
assembly into the port of the supply unit.
[0009] In combination with the tubing assembly, this invention also
provides a supply unit configured to supply gas for delivery to a
patient and to supply fluid for heating the gas. The supply unit
includes a port defining a gas outlet, a fluid outlet, and a fluid
inlet, wherein the fitting of the tubing assembly is releasably
engaged in the port of the supply unit. The gas outlet of the
supply unit is in flow communication with the gas inlet of the
fitting of the tubing assembly. The fluid outlet of the supply unit
is in flow communication with the fluid inlet of the fitting of the
tubing assembly. Finally, the fluid inlet of the supply unit is in
flow communication with the fluid outlet of the fitting of the
tubing assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Aspects of the present invention will now be described by
non-limiting example with reference to the following drawings, of
which:
[0011] FIG. 1 is a perspective view of an embodiment of an
apparatus according to aspects of this invention.
[0012] FIG. 2 is a schematic representation of the apparatus
illustrated in FIG. 1.
[0013] FIG. 3 is a top plan view of an embodiment of a supply unit
adapted for use as a component of the apparatus illustrated in FIG.
1, with the housing removed to reveal internal details.
[0014] FIG. 4A is a cross-sectional side view of an embodiment of a
delivery tube assembly adapted for use as a component of the
apparatus illustrated in FIG. 1.
[0015] FIG. 4B is an end view of the delivery tube assembly
illustrated in FIG. 4A.
[0016] FIG. 5 is a cross-sectional end view of an embodiment of a
tube adapted for use as a component of the delivery tube assembly
illustrated in FIGS. 4A and 4B.
[0017] FIG. 6A is a cross-sectional side view of an embodiment of a
delivery tube insert adapted for use as a component of the delivery
tube assembly illustrated in FIGS. 4A and 4B.
[0018] FIG. 6B is an end view of the delivery tube insert
illustrated in FIG. 6A.
[0019] FIG. 7 is a side view of an end portion of the delivery tube
assembly illustrated in FIGS. 4A and 4B.
[0020] FIG. 8A is a cross-sectional side view of a sleeve adapted
for use as a component of the delivery tube assembly illustrated in
FIGS. 4A and 4B.
[0021] FIG. 8B is an end view of the sleeve illustrated in FIG.
8A.
[0022] FIG. 9 is a schematic representation of another embodiment
of an apparatus according to aspects of this invention.
[0023] FIG. 10 is a perspective view of an embodiment of a supply
unit of the apparatus illustrated in FIG. 9.
[0024] FIG. 11A is a front perspective view of a back plate
assembly of the supply unit illustrated in FIG. 10.
[0025] FIG. 11B is a back perspective view of the back plate
assembly illustrated in FIG. 11A.
[0026] FIG. 12 is a front perspective view of a sensor printed
circuit board assembly adapted for use in the back plate assembly
illustrated in FIG. 11A.
[0027] FIG. 13 is a side view of a power printed circuit board
adapted for use in the back plate assembly illustrated in FIG.
11A.
[0028] FIG. 14 is a front view of a display printed circuit board
adapted for use in the back plate assembly illustrated in FIG.
11A.
[0029] FIGS. 15A and 15B provide a perspective view and a
cross-sectional view of a bubble trap assembly adapted for use in
the back plate assembly illustrated in FIG. 11A.
[0030] FIG. 16 is a perspective view of a water pump and water
heater assembly adapted for use in the back plate assembly
illustrated in FIG. 11A.
[0031] FIG. 17 is a perspective view of a manifold assembly adapted
for use in the back plate assembly illustrated in FIG. 11A.
[0032] FIG. 18 is a perspective view of a cover assembly adapted
for use in the supply unit illustrated in FIG. 10.
[0033] FIG. 19 is an embodiment of a display adapted for use with
the cover assembly illustrated in FIG. 18.
[0034] FIG. 20 is a perspective view of a main housing component of
the cover assembly illustrated in FIG. 18.
[0035] FIG. 21 is a perspective view of an embodiment of a housing
door component of the cover assembly illustrated in FIG. 18.
[0036] FIG. 22 is a perspective view of an embodiment of a delivery
tube assembly of the apparatus illustrated in FIG. 9.
[0037] FIG. 23 is an end view of an embodiment of a tube adapted
for use in the delivery tube assembly illustrated in FIG. 22.
[0038] FIGS. 24A-24D provide views of an embodiment of an inlet
fitting adapted for use in the delivery tube assembly illustrated
in FIG. 22.
[0039] FIGS. 25A-25C provide views of an embodiment of an outlet
fitting adapted for use in the delivery tube assembly illustrated
in FIG. 22.
[0040] FIGS. 26A-26B provide views of the manifold assembly
illustrated in FIG. 17.
[0041] FIGS. 27A-27B provide views of an embodiment of a manifold
adapted for use in the manifold assembly illustrated in FIGS. 26A
and 26B.
[0042] FIG. 28 illustrates an embodiment of a locking mechanism
adapted for use with the apparatus according to this invention.
[0043] FIG. 29 illustrates another embodiment of a bubble trap
assembly adapted for use with the apparatus according to this
invention.
[0044] FIG. 30 illustrates a perspective view of an embodiment of a
body component of the bubble trap assembly illustrated in FIG.
29.
[0045] FIG. 31 illustrates a top view of the body component
illustrated in FIG. 30.
[0046] FIG. 32 illustrates a front view of the body component
illustrated in FIG. 30.
[0047] FIG. 33 illustrates a cross-sectional side view of the body
component illustrated in FIG. 30.
[0048] FIG. 34 illustrates a perspective view of a lid component of
the bubble trap assembly illustrated in FIG. 30.
[0049] FIG. 35 illustrates a top view of the lid component
illustrated in FIG. 34.
[0050] FIG. 36 illustrates a front view of the lid component
illustrated in FIG. 34.
[0051] FIG. 37 illustrates a cross-sectional side view of the lid
component illustrated in FIG. 34.
[0052] FIG. 38 provides a diagram of an embodiment of a system
according to this invention.
[0053] FIG. 39 provides another diagram representing the system
illustrated in FIG. 38.
[0054] FIG. 40 provides a flow diagram of an embodiment of software
adapted for use with the apparatus according to this invention.
[0055] FIG. 41 illustrates a front perspective view of another
preferred embodiment of a back plate assembly of the supply
unit.
[0056] FIG. 42 illustrates changes in FEV.sub.1 and FVC normalized
to baseline (left) and placebo (right) in asthmatic patients in
connection with Example 1.
[0057] FIGS. 43A and 43B illustrate work of breathing, mean tidal
volume, and minute volume in connection with Example 2.
[0058] FIG. 44 illustrates inspiratory time (COPD) in connection
with Example 2.
[0059] FIG. 45 illustrates core rewarming rate for patients
receiving routine oxygen therapy (Control) or warmed, humidified
oxygen therapy (Test) in the initial postoperative hour in
connection with Example 3.
[0060] FIG. 46 illustrates change in core temperature from
baseline, measured upon admission to the postanesthesia care unit,
in connection with Example 3.
[0061] FIG. 47 illustrates that patients in the Test group had a
lower incidence of dry mouth in the postoperative period in
connection with Example 3.
DETAILED DESCRIPTION OF THE INVENTION
[0062] Aspects of this invention will now be described with
reference to specific examples and embodiments selected for
illustration in the figures. It will be appreciated that the spirit
and scope of this invention is not limited to the selected examples
and embodiments, and that the scope of this invention is defined
separately in the appended claims. It will also be appreciated that
the figures are not drawn to any particular proportion or scale,
and that many variations can be made to the illustrated embodiments
without departing from the spirit of this invention.
[0063] Referring to the figures in general, according to one aspect
of this invention an elongated member such as a delivery tube 28 is
provided for delivering fluid from a fluid inlet such as an air
inlet opening 58 at a proximal end portion of the elongated member
to a fluid outlet such as a tubing connector 82 at a distal end
portion of the elongated member for receipt by a patient (not
shown). The elongated member is adapted to heat the fluid as it is
delivered to the patient.
[0064] The elongated member includes a delivery lumen such as an
air lumen 72 defined by the elongated member from the fluid inlet
at the proximal end portion to the fluid outlet at the distal end
portion. The delivery lumen is configured for the flow of the fluid
distally from the fluid inlet toward the fluid outlet. The
elongated member also includes a heating fluid inlet such as a
water inlet opening 60 defined by the elongated member at the
proximal end portion as well as a heating supply lumen such as a
heating fluid lumen 74 defined by the elongated member adjacent to
the delivery lumen from the heating fluid inlet to the distal end
portion.
[0065] Also included as a part of the elongated member is a heating
fluid outlet such as a water outlet opening 62 defined by the
elongated member at the proximal end portion as well as a heating
return lumen such as a return lumen 76 defined by the elongated
member adjacent to the delivery lumen from the distal end portion
to the heating fluid outlet. The heating supply lumen and the
heating return lumen are connected to one another (adjacent to
tubing connector 82, for example) for flow therebetween at the
distal end portion.
[0066] The heating supply lumen and the heating return lumen of the
elongated member are configured for the flow of the heating fluid
distally from the heating fluid inlet toward the distal end portion
through the heating supply lumen, and for flow of the heating fluid
proximally from the distal end portion toward the heating fluid
outlet through the heating return lumen. Heat is thereby
transferred from the heating fluid to the fluid in the delivery
lumen as it is delivered to the patient.
[0067] According to another aspect of this invention, an apparatus
such as a supply unit 11 is provided for respiratory tract therapy.
The apparatus includes a housing such as housing 11A that is
configured to receive air and water. A humidified air outlet such
as an air outlet port or connector 40 is defined in the housing for
delivering humidified air from the apparatus. A water supply outlet
such as a water outlet port or connector 42 is defined in the
housing for delivering heated water from the apparatus. Finally, a
water return inlet such as a water inlet port or connector 44 is
defined in the housing for returning heated water to the
apparatus.
[0068] The humidified air outlet, the water supply outlet, and the
water supply inlet of the apparatus are positioned proximal to one
another for releasable connection to an elongated member such as
delivery tube 28 that is configured for delivering the humidified
air from the housing toward the respiratory tract of a patient. The
elongated member is also configured for circulating heated water
from the water supply outlet to the water return inlet to transfer
heat from the heated water to the humidified air as it is delivered
to the patient.
[0069] According to yet another aspect of this invention, an
apparatus such as a system 100 is provided with a supply unit such
as supply unit 102 having an air inlet 152 configured for
releasable connection to a source of pressurized air. The apparatus
is also provided with a port such as port 130 providing a
humidified air outlet for delivering humidified air from the supply
unit, a fluid supply outlet for delivering heated fluid from the
supply unit, and a fluid return inlet for returning heated fluid to
the supply unit.
[0070] An elongated member such as delivery tube assembly 104 is
releasably connected to the supply unit. The elongated member
defines a delivery lumen such as air lumen 260 configured to
deliver humidified air toward a patient. The elongated member also
defines a fluid supply lumen such as heating fluid lumen 262 (or
264) and a fluid return lumen such as return lumen 264 (or 262),
each extending adjacent to the delivery lumen. The fluid supply and
fluid return lumens are configured to circulate the heated fluid
between the fluid supply outlet of the supply unit and the fluid
return inlet of the supply unit to transfer heat from the heated
fluid to the humidified air as it is delivered to the patient.
[0071] An apparatus according to this invention will now be
described with reference to the specific embodiment selected for
illustration in FIG. 1. Generally speaking, the apparatus is
adapted to deliver heated and humidified air to the respiratory
tract of a human patient. The apparatus illustrated in FIG. 1 is
compact in size and portable, so as to be adapted for use in a
variety of settings and for transport between locations. The
apparatus can be used in the home by a patient and at the patient's
bedside, if desired. The apparatus can also be used in hospitals,
clinics, and other settings, as well.
[0072] The apparatus includes a supply unit that provides a source
for heating fluid such as heated water as well as a source of
humidified air. The heating fluid provided by the supply unit is
used to heat the humidified air as the humidified air is delivered
from the supply unit to the patient's respiratory tract.
[0073] The apparatus also includes a delivery tube assembly that is
releasably attached to the supply unit. The delivery tube assembly
is designed so that it can be used by a particular patient and then
discarded after one or a number of uses. The delivery tube assembly
provides a passageway for the flow of humidified air to the
patient's respiratory tract. The delivery tube assembly also
provides passageways for the flow and return of heating fluid in
such a way as to promote heat transfer from the heating fluid to
the humidified air as it is delivered.
[0074] Throughout the descriptions of apparatus 10 and, especially,
delivery tube assembly 24, reference is made to portions of the
figures to define directions for flow and the position of various
features. The terms "proximal" and "distal" will also be used to
indicate such positions. Specifically, as used herein, the term
"proximal" refers to a position toward the supply unit (away from
the patient), and the term "distal" refers to a position toward the
patient (away from the supply unit).
[0075] Referring now to the embodiment selected for illustration in
FIG. 1, apparatus 10 includes a supply unit 11 having a
substantially enclosed housing 11A that is adapted to rest on a
table top or other surface or stand in a portable configuration.
Supply unit 11 is provided with an air exhaust 13 defined by
openings in the housing of supply unit 11. An air inlet (not shown)
permits the flow of air into the interior of the housing. A water
supply 15 in the form of a water container or reservoir is
releasably connected in the top portion of the housing of supply
unit 11 so that it can be removed and refilled to provide a supply
of water to apparatus 10.
[0076] A display panel 17 on a surface of the housing of supply
unit 11 permits a user to control aspects of apparatus 10 and also
displays information that can be used by the patient or the
patient's assistant. For example, in this embodiment of apparatus
10, display panel 17 includes "UP" and "DOWN" buttons (indicated by
arrows) so that the user can adjust the air temperature. Display
panel 17 also includes a temperature output display as well as a
display for the minimum and maximum set temperatures. Display panel
17 also includes indicators for the maintenance of apparatus 10: an
"ADD WATER" light indicates that water should be added via water
supply 15; a "DELIVERY TUBE" light indicates that a delivery tube
assembly 24 (described later) must be reconnected; a "CARTRIDGE"
light indicates that a cartridge (to be described later) needs
maintenance; a "CLEANING" light indicates that aspects of apparatus
10 should be cleaned; and a "CHANGE CARTRIDGE" light indicates that
the cartridge should be changed.
[0077] The delivery tube assembly 24 is releasably connected to the
housing of supply unit 11 by means of a connector block 26. The
connection between supply unit 11 and delivery tube assembly 24 can
be easily broken to remove assembly 24 for cleaning, for
maintenance, or for disposal and replacement. Quick disconnects
(described later) are provided on connector block 26 and supply
unit 11 to facilitate the removal and replacement of assembly 24. A
delivery tube 28 extends from connector block 26 to a nasal cannula
29 that extends from delivery tube 28 to the patient's respiratory
tract during use. Nasal cannula 29 and associated fittings used for
supplying air to the nares of a patient are readily available
components that are well known in the art.
[0078] Referring now to FIG. 2, which provides a schematic
representation of apparatus 10, arrows have been provided to
indicate the flow of air "A" and water "W" through the system. As
described earlier, air flows into the interior of the housing of
supply unit 11 via air inlet openings (not shown), and water flows
into the interior of supply unit 11 via water supply 15 (FIG. 1).
The flow of air and water in apparatus 10 will now be
described.
[0079] Air introduced into the housing of supply unit 11 passes
through a vacuum muffler 12. An air compressor 14 pressurizes the
air downstream of vacuum muffler 12. A variety of air compressors
can be used, and such air compressors are well known in the art.
One example of a suitable air compressor is manufactured by Thomas
Compressors of Norcross, Ga. and sold under the model number
007CA13F. Other compressors can be substituted. A check valve 16 is
provided downstream from air compressor 14 in order to release
excessive air pressure.
[0080] Air flows from air compressor 14 to a flow control valve 18,
which is used to control or regulate the air pressure in system 10.
Air then flows to an air filter 20 that is adapted to remove
contaminants from the air so that they are not delivered to the
patient's respiratory tract. Air then flows through a membrane
cartridge 22 and through delivery tube assembly 24. More
specifically, air that has been pressurized by air compressor 14
enters connector block 26 and flows outwardly toward the patient
through delivery tube 28. An inlet 30 is provided for the optional
introduction of oxygen into connector block 26 in order to enrich
the proportion of oxygen in the air delivered to the patient.
[0081] Referring now to the flow of water through apparatus 10 as
illustrated in FIG. 2, water "W" is introduced by means of a
reservoir 32 that is fed by water supply 15 (FIG. 1). A water pump
34 is used to deliver a fluid, such as water, from the reservoir 32
to a fluid heater 36 which heats the water to a predetermined
temperature or temperature range, as will be described in more
detail later. The heated water then flows into delivery tube
assembly 24. More specifically, heated water enters connector block
26 and flows into delivery tube 28. In a manner that will be
described in more detail later, water then returns from delivery
tube assembly 24 into the housing of supply unit 11, and a
thermister 38 is used to monitor the temperature of the returning
water. The temperature measured by thermister 38 is used to control
water heater 36 in order to maintain the temperature of the water
within a predetermined range.
[0082] A portion of the returned water can flow directly to the
reservoir 32 so that it can be recycled through apparatus 10.
Another portion of the returned water can flow through membrane
cartridge 22 before returning to reservoir 32. Alternatively, all
of the water can flow to the membrane cartridge 22. Water is passed
through membrane cartridge 22 in order to add water vapor to the
air that is flowing in counter-current arrangement through membrane
cartridge 22 (as shown in FIG. 2).
[0083] Membrane cartridge 22 is preferably a hollow fiber filter
module having a microporous membrane that permits the flow of water
vapor from the heated water into the air. More specifically, the
heated water flows through a housing of the membrane cartridge in
contact with the outside surfaces of the hollow fiber membranes.
The air flows through the hollow fiber membranes in a direction
that is counter-current to the direction of the water in the
housing of cartridge 22. Water vapor is transferred through pores
in the hollow fiber membranes from the heated water to the air in
order to humidify the air for delivery to the respiratory tract of
the patient. Although a wide variety of filters can be employed to
perform this function, a hollow fiber membrane is preferred. Such
filters are available from SPECTRUM MICROGON of Laguna Hills,
Calif. under part number M11S-260-01N.
[0084] Referring now to FIG. 3, an exemplary preferred embodiment
of supply unit 11 is illustrated with the housing removed to reveal
the internal details of supply unit 11. The flow of air "A" and
water "W" through portions of supply unit 11 will now be described
with reference to FIG. 3. Ambient air enters air compressor 14,
which is powered by compressor motor 9, for pressurization. An
exhaust fan 19 is positioned adjacent to compressor motor 9 in
order to withdraw heat from supply unit 11 that is generated by air
compressor 14 and compressor motor 9. Air travels from air
compressor 14 and past relief valve 16 for delivery to air filter
20 (not shown in FIG. 3) and membrane cartridge 22 (not shown in
FIG. 3). Humidified air from membrane cartridge 22 arrives at the
tubing illustrated at the lower left-hand side of FIG. 3, as
indicated by an arrow, and travels to an air outlet port 40.
[0085] At the same time, water is introduced from reservoir 32 (not
shown in FIG. 3) into an inlet line 25 through which it is
delivered to water pump 34, which is driven by water pump motor 35.
Water then travels from water pump 34 to an inlet on the right-hand
portion of water heater 36. Heated water then travels from an
outlet on the left-hand portion of water heater 36 to a heated
water outlet port 42. Water is returned to the interior of the
housing of supply unit 11 via a water inlet port 44.
[0086] Air outlet port 40, water outlet port 42, and water inlet
port 44 are provided by connectors such as quick disconnects that
are attached to the housing of supply unit 11 via a bracket 46. The
ports 40, 42, and 44 are arranged closely adjacent to one another
at the surface of the housing of supply unit 11 so that they can be
simultaneously engaged and disengaged to the delivery tube assembly
24 (not shown), as will be described later in more detail.
[0087] Referring now to FIGS. 4A and 4B, aspects of an exemplary
delivery tube assembly according to this invention will now be
described. Delivery tube assembly 24 is shown in a cross-sectional
side view in FIG. 4A and in an end view in FIG. 4B. Delivery tube
assembly 24 includes a connector block 26 and a delivery tube 28,
as described before, as well as a sleeve 50 inserted into one end
of a lumen 51 that extends through the connector block 26 along its
axis. Delivery tube assembly 24 also includes a delivery tube
insert 52 that is positioned in the opposite end of lumen 51. A
length of tubing 54 extends between lumens defined by sleeve 50 and
delivery tube insert 52, and a coupling 56 is optionally threaded
onto an end of delivery tube insert 52 in order to couple delivery
tube 28 to delivery tube insert 52.
[0088] Connector block 26 has an air inlet 58, a water inlet 60,
and a water outlet 62 in the form of holes formed in a surface of
connector block 26. Air inlet 58, water inlet 60, and water outlet
62 provide access for the flow of air and water through connector
block 26 to delivery tube 28. Connectors such as disconnects are
mounted on connector block 26 at openings 58, 60, and 62 for
connection to air outlet port 40, water outlet port 42, and water
inlet port 44, respectively.
[0089] Referring now to FIG. 5, which provides a cross-sectional
end view of delivery tube 28, further details of delivery tube 28
will now be described. Delivery tube 28 can be formed from a
variety of materials by a variety of processes. Preferably,
delivery tube 28 is formed from polymeric material such as
polyurethane. In one embodiment, delivery tube 28 is formed from
PELLETHANE #2363-80AE, which has a durometer of Shore 80A. Delivery
tube 28 is preferably clear to permit visualization of the water
flowing through it. Delivery tube 28 is preferably extruded in long
lengths having a substantially constant cross-sectional shape.
Although various lengths are contemplated for delivery tube 28, a
length of about 10 feet has been discovered to provide adequate
performance and adequate versatility to the patient. Other lengths
are of course contemplated, depending on the usage of the
apparatus, the length of nasal cannula 29, and the heat transfer
characteristics from the heated fluid to the air, and matters of
cost and design choice.
[0090] Delivery tube 28, in the preferred embodiment illustrated,
includes a substantially circular outer wall 64 spaced
concentrically around a substantially circular inner wall 66.
Boundary walls or webs 68A and 68B extend from the inner surface of
outer wall 64 to the outer surface of inner wall 66. A plurality of
longitudinally extending ribs 70 extends radially inwardly from the
inner surface of inner wall 66 and along the axis of delivery tube
28. Inner wall 66 and ribs 70 together define an air lumen 72 that
extends along the length of delivery tube 28. In the embodiment
illustrated in FIG. 5, six ribs 70 are uniformly spaced. Ribs 70
help to prevent constriction of air lumen 72 in the event that
delivery tube 28 is bent in use or otherwise kinked
unintentionally.
[0091] Outer wall 64 and inner wall 66 together define with
boundary walls or webs 68A and 68B a pair of opposed lumens that
have a substantially arcuate cross-sectional shape and that
substantially surround air lumen 72. More specifically, a heating
fluid lumen 74 extends longitudinally along the tube through the
lower half of delivery tube 28, and a return lumen 76 extends
longitudinally along the tube through the upper half of delivery
tube 28. The heating fluid lumen 74 substantially surrounds the
lower portion of air lumen 72, and return lumen 76 substantially
surrounds the upper portion of air lumen 72. Together, lumens 74
and 76 together cooperate with one another to substantially
surround air lumen 72.
[0092] Referring again to FIGS. 4A, 4B, and 5, the flow of air "A"
and water "W" through delivery tube assembly 24 will now be
described. Air enters delivery tube assembly 24 through inlet 58
from air outlet 40 on supply unit 11 and travels to the left in
FIG. 4A through the passageway defined by tubing 54. Air then
travels into the air lumen 72 of delivery tube 28 and toward the
respiratory tract of the patient through the nasal cannula 29
(shown in FIG. 1). If supplemental oxygen or another gas or
medicine is to be introduced to the respiratory tract, a source of
such a gas or fluid or medication can be attached to the right-hand
end of sleeve 50 where a threaded opening is provided. In such a
manner, oxygen or other fluids or medicines can be mixed with air
for delivery to the patient.
[0093] The manner with which water travels through delivery tube
assembly 24 will now be described in further detail with reference
to FIGS. 6A and 6B, which illustrate details of delivery tube
insert 52. Delivery tube insert 52 includes two extension portions
75 and 77 which are shaped to extend into the lumens 74 and 76,
respectively, of delivery tube 28. Extension 77 has a substantially
semi-circular cross-sectional shape that corresponds to the shape
of return lumen 76 so that extension portion 77 can extend into the
interior of return lumen 76 and create a seal. Similarly, extension
portion 75 is shaped to fit within heating fluid lumen 74 of
delivery tube 28. Although insert 52 can be formed from a variety
of materials, aluminum or other metals or plastics can be used.
Insert 52 can be formed by molding, machining, or by other known
forming methods.
[0094] Apertures 78 extend through extension 77 and through the
entire length of delivery tube insert 52 from end to end. In this
specific embodiment, six apertures 78 are provided to extend from
one end of delivery tube insert 52 to the other. Apertures 79,
however, extend through extension portion 75 from one end of
delivery tube insert 52 but terminate at a location before the
opposite end of delivery tube insert 52. In other words, apertures
79 are "blind" in that they do not extend fully through the insert
52. Instead, a side opening 80 (FIG. 6A) is provided for access to
at least some of the apertures 79 that extend through extension
portion 75. It will be appreciated, as is illustrated in FIG. 4A,
that side opening 80 in delivery tube insert 52 is positioned and
sized to correspond to water inlet opening 60 that is defined in
the connector block 26 of delivery tube assembly 24.
[0095] The flow of water through delivery tube assembly 24 will now
be described with reference to FIGS. 4A, 5, and 6A. Water enters
connector block 26 of delivery tube assembly 24 through water inlet
opening 60 from water outlet 42 (FIG. 3) of supply unit 11. Water
then travels to the left in FIG. 4A through apertures 79 that
extend through extension portion 75 so that water can enter heating
fluid lumen 74. In this embodiment, heated water is the heating
fluid. The heated water then travels through delivery tube 28
toward the opposite end of the tube.
[0096] In a manner that will be described later in more detail,
heating fluid lumen 74 is connected to return lumen 76 at the
opposite end of delivery tube 28 so that heated water can flow from
lumen 74 into lumen 76 for return toward connector block 26. The
water then returns through return lumen 76 and enters apertures 78
that are defined in the extension portion 77 of delivery tube
insert 52. The water then can flow from one end of delivery tube
insert 52 to the other until it can enter the central lumen 51 of
connector block 26. Water can then exit connector block 26 through
water outlet opening 62 and can return to supply unit 11 through
water inlet 44 (FIG. 3).
[0097] It will be appreciated that air is caused to flow through
the length of delivery tube 28 to the patient and that heated water
is caused to flow through the heating fluid and return lumens 74
and 76 in close proximity to the air flow lumen 72. This
arrangement has been discovered to provide highly efficient heat
transfer from the heating fluid (such as heated water) to the
flowing air. Water at its highest temperature (in the upstream
portion of the path through the delivery tube) flows through
heating fluid lumen 74 in the same direction as air flows through
air lumen 72. Water at a slightly lower temperature, due to some
heat loss and heat transfer, then travels through return lumen 76
in a counter-current flow pattern with the air in air lumen 72.
[0098] Referring now to FIG. 7, the opposite end of delivery tube
28 is illustrated together with a termination that provides access
for heating fluid flow between lumens 74 and 76. More specifically,
referring back to FIG. 5, the webs or boundaries 68A and 68B are
cut and removed in the end portion of delivery tube 28 and a tubing
connector 82 is inserted into the end of tubing 28 between inner
and outer walls 66 and 64. Connector 82 therefore provides a flow
path for air from air lumen 72. Connector 82 also prevents the
leakage of water from return lumen 76 or heating fluid lumen 74,
yet permits water flow from heating fluid lumen 74 to return lumen
76. The tubing connector 82 is configured to be connected to a
cannula connector 86 that extends to a fitting that can be used to
introduce the heated and humidified air into a nasal cannula for
the delivery of air to the nasal passageway of a patient for
respiratory tract treatment or other therapies as described
herein.
[0099] FIGS. 8A and 8B illustrate further details of the sleeve
component 50 of delivery tube assembly 24 in order to clarify the
manner in which air is delivered through air inlet 58 from the air
outlet 40 of supply unit 11. Sleeve 50 can be formed from metallic
or polymeric materials. In one preferred embodiment, sleeve 50 is
molded or machined from clear polycarbonate. As illustrated in
FIGS. 8A and 8B, sleeve 50 has a longitudinally extending lumen 88
and a series of three radially openings 90A-90C. The radial
openings 90A-90C extend between lumen 88 and an annular recess 92.
Accordingly, air introduced through air inlet 58 from air outlet 40
travels into the annular recess 92 and then travels through
radially oriented openings 90A-90C into lumen 88. It will be
appreciated that the rotational orientation of sleeve 50 within
connector block 26 is not critical because of annular recess 92 so
that the air inlet 58 will never be blocked. Air can therefore flow
from lumen 88 of sleeve 50 into the interior of tubing 54 which
extends into lumen 88.
[0100] A threaded opening 94 is provided at the right-hand side of
sleeve 50 as it is illustrated in FIG. 8A. Threaded opening 94
provides for threaded engagement with a source of oxygen or some
other gas or fluid or medication that is intended to be introduced
into the air stream delivered into the patient's respiratory
tract.
[0101] Another embodiment of an apparatus according to this
invention will now be described with reference to FIGS. 9-28.
Generally, this embodiment of the apparatus is adapted for portable
use such as in a hospital in order to provide respiratory care.
More specifically, it is well adapted for conditioning gas from a
wall gas outlet or tank source and for delivering the conditioned
gas to a patient via a delivery tube assembly that is connected to
a nasal cannula or other narrow-gauge cannula, or to a mask. Unlike
system 10 this embodiment of the apparatus need not have an
on-board air compressor or flow control valve. Accordingly, it can
be produced in a significantly smaller and lighter package as
compared to system 10. This makes it possible to mount this
embodiment of the apparatus on an IV pole next to a patient, such
as in a hospital setting.
[0102] An inlet connector is provided on the back of the apparatus
in order to receive gas from a source of air or oxygen at a set
flow rate and oxygen concentration, such as in a hospital. The gas
is then heated and humidified in a controlled manner and the
conditioned gas is delivered through a delivery tube assembly to a
patient through a face mask, nasal cannula, or other cannula at a
selected temperature and saturated humidity, without condensation.
The patient inspires this controlled gas mixture and any excess
respiratory gas is supplied from entrained air that enters around
the cannula.
[0103] In one exemplary use of this embodiment of the invention,
the apparatus is used in a hospital care setting next to the
patient. Nurses, nurse's aides or assistants, or respiratory
therapy personnel can easily set up and control the operation and
daily maintenance of the apparatus. Maintenance personnel can
easily perform periodic cleaning and maintenance of the unit
between patients. The delivery tube assembly is intended to be
disposable, for single patient use.
[0104] The compact apparatus can be mounded on a standard IV pole,
3/4 to 11/4 inch diameter, by a clamping mechanism on its back. The
weight of the apparatus is preferably less than about 6 pounds,
excluding a water filled reservoir. The vertical size of the
apparatus is preferably less than about 10 inches when mounted on
an IV pole, and the width is preferably less than about 4.5 inches.
The depth of the apparatus is preferably less than about 3 inches,
excluding the clamp and fittings for engagement to the IV pole.
[0105] The heat-moisture exchange cartridge, which will be
described later in further detail, is preferably accessible for
service without disassembly or removal of the apparatus from the IV
pole. One example of a cartridge that can be used in an apparatus
according to this invention is provided by Spectrum under part
number M11S-260-01N or by Vapotherm, Inc. under part number VT01-A.
Other configurations of this cassette may be considered in order to
increase surface area and reduce pressure drop. The hollow fibers
of one preferred cartridge have a wall thickness of about 55 to
about 60 microns. Other hollow fibers can of course be
utilized.
[0106] The preferred elimination of the compressor and flow control
valve makes it possible to reduce the noise level associated with
operation of this embodiment of the apparatus. For example, the
sound pressure can be maintained at a level not exceeding about 55
dBA, excluding an audio alarm to be described later.
[0107] Gas (air, oxygen, or some combination) is supplied to the
apparatus via a tube at about 50 psi maximum pressure. Gas flow can
be regulated by a user-supplied restricting valve at the source of
the gas so that it can be controlled between preferred flows of
about 5 to 501/min, more preferably between about 5 to 40 l/min.
Water can be supplied to the apparatus from a bag of water via an
unconstricted tube of at least about 3/8'' internal diameter and
not more than about 9'' long. An example of a suitable bag and tube
set is supplied by Vapotherm, Inc. under part number WR1200. A
delivery tube assembly can be attached at the front of the
apparatus via a manifold that interfaces to a gas supply port and
to heating water supply and return ports. The delivery tube
assembly is preferably installed into the manifold by a
push-and-turn retaining mechanism.
[0108] The unit preferably operates on standard 115 VAC, 60 Hz, and
power consumption is preferably about 250 VA. A standard hospital
grade power cord can be supplied with the unit. The software code
for the apparatus can be written in "C" language and can be
developed and tested in accordance with FDA Software Design Control
Validation Requirements.
[0109] The apparatus according to this embodiment preferably
includes a two (2) digit, seven (7) segment LED display in order to
indicate a set point temperature when the temperature is being
adjusted. The display can then convert to measured temperature
after a short period such as about 5 seconds. The controls for the
system, as will be described later in further detail, are
preferably tactile feedback switches in a membrane panel. An up and
down arrow can be used to set temperature controls. Power on/off
can be provided via a single control on the membrane panel. Also,
alarm silence/reset controls can be provided via a single membrane
switch.
[0110] The apparatus in this embodiment preferably includes alarm
condition indicators, such as LED's. Such indicators can be labeled
with identification or international symbols, as desired. An audio
annunciator can be provided to sound when any alarm condition
exists, and an alarm silence button can be provided to quiet the
alarm for a set period of time such as two minutes. The alarms can
be configured to reset if the alarm condition no longer exists. All
temperature-related alarms can be defeated until warm up of the
apparatus is complete, or until the apparatus has run for a set
period of time such as 10 minutes. Other alarms can be defeated for
a set period of time, such as 2 minutes, upon start up.
[0111] The apparatus in this embodiment can be provided with a
"WATER LOW" alarm in order to indicate that the water reservoir is
not supplying water in a quantity sufficient to maintain the
humidification level at full capacity. The system can remain
running for up to 4 minutes if the "WATER LOW" condition continues,
before the system is halted.
[0112] The apparatus in this embodiment can also be provided with a
"SYSTEM FAILURE" alarm in order to indicate that water has entered
the gas system and that the supply of gas has been halted or that a
so-called "watchdog" timer has failed. Upon a "SYSTEM FAILURE"
alarm, the system can be halted and a continuous auto alarm can be
activated. Also, the digital display can show "88".
[0113] The apparatus in this embodiment can also include a "HIGH
TEMP" alarm in order to indicate that the water has overheated to a
temperature above a predetermined maximum temperature, such as a
temperature about 45.degree. C. Upon such an alarm, the heater and
airflow can shut down while the water pump can continue to
operate.
[0114] The apparatus can also be provided with a "CARTRIDGE" alarm
in order to indicate that the humidification cartridge lifetime has
been exceeded. The system will continue to operate normally.
[0115] A "BLOCKED TUBE" alarm can also be provided. A "BLOCKED
TUBE" alarm can indicate that the delivery tube to the patient is
either kinked or blocked. Upon such an alarm, the water pump of the
apparatus can stop delivering water, and gas flow can be turned off
until the condition is corrected.
[0116] Various caution and advisory conditions can also be
indicated by the apparatus. An indication of such condition can be
provided without an audio alarm. For example, a "CLEANING" caution
condition can be provided to indicate that the unit is in a special
mode for cleaning the gas supply system and that normal controls
and alarms are not active. This caution condition indicator can be
a yellow back-lit symbol, for example. An example of an advisory
condition could be a "POWER ON" indicator to provide an indication
that the unit is running. Such an indicator can be green, for
example.
[0117] The apparatus in this embodiment can be operated in a wide
range of ambient temperatures (at least about 15 to about
40.degree. C.) and ambient relative humidity (at least about 20 to
about 90% rH). The apparatus can be used at ambient pressure
conditions in the absence of hyperbaric conditions.
[0118] Preferably, the apparatus in this embodiment 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 35.0.degree. C. to about
43.0.degree. C.; a display temperature of from about 15.degree. C.
to about 50.degree. C. measured at the water outlet from the
cartridge; 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.
[0119] The delivery tube assembly, which will be described later in
further detail, is hydronically heated. The delivery tube
preferably has a reduced pressure drop at the maximum flow of gas
as compared to the delivery tube of the first embodiment. This
reduction in pressure drop is provided by means of axial gas
connectors at the ends of the delivery tube to provide a straight,
unobstructed gas flow path between the apparatus and the delivery
tube outlet. Details of the delivery tube connectors will be
described later.
[0120] The water heater used in the apparatus in this embodiment
can be 150 VA, 115 VAC, PID software feedback controlled from a
water temperature measured at the outlet of the cartridge. Power to
the water heater can be cut off if the heater's surface exceeds a
predetermined temperature such as 60.degree. C.
[0121] The water pump in the apparatus in this embodiment
preferably circulates heating water at a flow rate of from about
0.6 to about 2.01/min. The pressure drop of the water pump
preferably does not exceed about 10 psi.
[0122] Referring now to FIGS. 9-28, exemplary features of an
apparatus adapted for portable use such as in a hospital will now
be described. Referring first to the schematic representation
provided in FIG. 9, an apparatus 100 includes a supply unit
assembly 102 and a delivery tube assembly 104, which is adapted to
be removably attached to supply unit assembly 102. Supply unit
assembly 102 is provided with an inlet 106 for receiving gas from a
wall source or from a compressor or a tank or other source. The gas
is most preferably provided with a flow rate from about 5 to about
35 l/min. Down stream from inlet 106 is a gas shutoff solenoid
valve 108 to prevent gas flow when desired. An exchanger 110 is
provided to humidify the gas by means of counter-current flow of
water and gas through the exchanger 110. A leak detector 112 and a
pressure transducer 114 are provided down stream of exchanger 110.
The gas then travels outwardly through delivery tube assembly 104
in order provide a supply of heated, humidified gas as indicated at
"A".
[0123] Supply unit assembly 102 is configured to receive water from
a water bag 116. A pump 118, which can be provided with a 12 VDC
power supply, urges the water through supply unit assembly 102. A
pressure transducer 120 is provided down stream of pump 118 to
sense the pressure of the water in the system. The water is then
heated in heater 122, which can be provided with a 115 VAC power
supply. The water, as indicated at "W," advances through supply
unit assembly 102 into delivery tube assembly 104. Water W is
preferably delivered from supply unit assembly 102 at a flow rate
of about 0.6 l/min., and at a pressure of about 8 psi.
[0124] The heated water flows through the delivery tube assembly
104 in a manner that will be described in further detail later. The
water then returns to supply unit assembly 102 for flow through
exchanger 110. The temperature of the water is sensed at a location
down stream from the exchanger 110. The water then repeats the
circuit through the system in a circulating manner. Water from
water bag 116 supplements the recirculating water.
[0125] Referring to FIG. 10, an embodiment of supply unit assembly
102 is illustrated with a portion of its cover opened to reveal
internal details. Supply unit assembly 102 includes a back plate
assembly 126 and a cover assembly 128. Within a portion of cover
assembly 128 a cartridge for exchanger 110 is provided. Also, a
delivery tube port 130 is provided in supply unit assembly 102 in
order to facilitate connection of delivery tube assembly 104.
[0126] Referring now to FIGS. 11A and 11B, preferred features of
back plate assembly 126 will now be described. Back plate assembly
126 includes a back plate 132 to which various electronic and
plumbing components are connected. A solenoid 134 (corresponding to
solenoid 108 shown in FIG. 9) is connected to back plate 132
adjacent to a power printed circuit board 136. Also connected to
back plate 132 is a water pump and water heater assembly 138
(corresponding to water pump 118 and water heater 122 shown in FIG.
9) as well as a manifold assembly 140. An elbow 142 is mounted to
back plate 132 by means of a clamp 144. Also mounted to back plate
142 is a sensor printed circuit board assembly 146 as well as a
plate fitting 148 for engagement of a bubble trap assembly 150.
[0127] Referring specifically to FIG. 11B, which shows a
perspective view of the back of back plate 132, back plate assembly
126 also includes a gas inlet fitting 152, a fuseholder 154, and an
electric cord attachment 156. Also provided on the back surface of
back plate 132 is an IV pole clamp 158, which is provided with a
knob 160 in order to facilitate engagement of supply unit assembly
102 to an IV pole. Also provided is a bubble trap assembly.
[0128] Referring now to FIG. 12, preferred features of sensor
printed circuit board 146 will now be described. Assembly 146
includes a printed circuit board 162 on which are mounted three
pressure sensors 164, 166, and 168. Fewer pressure sensors can be
used, if desired. Also connected to printed circuit board 162 are
connectors 170 and 172. One or two of the sensors are pressure
transducers that are connected to the manifold assembly 140 to
monitor the pressure of heating fluid as it flows out from, and
returns to, the supply unit assembly 102. These sensors can,
therefore, detect any blockage in the delivery tube assembly 104 or
other condition that could result in an abnormal pressure drop
between the heating fluid outlet and inlet. The remaining pressure
sensor is a pressure transducer that is connected to the manifold
assembly 140 to monitor the pressure of air as it is delivered from
the supply unit assembly 102 into the delivery tube assembly
104.
[0129] Although three (3) pressure sensors 164, 166, and 168 are
illustrated in FIG. 12, it will be appreciated that one or two such
sensors can be utilized as well. For example, two of the three
sensors 164, 166, and 168 can be used to sense pressure so that a
pressure differential can be calculated in the system.
Alternatively, in order to reduce the number of pressure sensors
from three to two, a straight measurement of pressure can be used
as opposed to as pressure differential.
[0130] Referring now to FIG. 13, preferred features of the power
printed circuit board 136 are illustrated. Assembly 136 includes a
printed circuit board 174. Mounted on the printed circuit board 174
is a power supply 176.
[0131] FIG. 14 illustrates an embodiment of a display printed
circuit board 178 that is adapted for connection to the back plate
assembly 126 illustrated in FIGS. 11A and 11B. The display printed
circuit board 178 includes a printed circuit board 180 on which is
mounted a display 182, such as an LED or LCD display, in order to
display to the user of the system a set point temperature or a
sensed temperature. Display printed circuit board assembly 178 also
includes a series of indicators 184 such as LEDs. The purpose of
these indicators will be described later with reference to FIG.
19.
[0132] Referring now to FIG. 15, exemplary features of bubble trap
assembly 150 are illustrated. The bubble trap assembly 150 helps to
remove bubbles from the water as it flows through the system.
Assembly 150 includes a fitting 186 on which a water temperature
probe 188 is mounted. Probe 188 is used to monitor the temperature
of the heating fluid that is circulating through the system.
[0133] Referring now to FIGS. 29-37, exemplary features of another
embodiment of a bubble trap assembly 400 are illustrated. Bubble
trap assembly 400 operates in a manner similar to bubble trap
assembly 150 in that it helps to remove bubbles from the
circulating water as it flows through the system. Bubble trap
assembly 400 includes a body component 402, a lid component 404,
and a fitting component 406.
[0134] Exemplary features of the body component 402 of the bubble
trap assembly 400 are illustrated in FIGS. 30-33. Body component
402 defines a chamber 408 configured to contain fluid such as water
that is circulated through the system. An inlet port 410 is
provided to introduce fluid into the interior of the chamber 408.
Positioned below inlet port 410 is an outlet port 412, which is
provided to permit the flow of water from the chamber 408. Body
component 402 of bubble trap assembly 400 also includes a sensor
port 414, which is provided so that a temperature sensor (not
shown) can be mounted to the bubble trap assembly 400 to monitor
the temperature of water as it passes through the chamber 408.
Sensors to monitor other conditions of the water or other fluid can
be exchanged for the temperature sensor.
[0135] Referring specifically to FIG. 32, the outlet port 412 is
provided with a diameter D.sub.1 to receive a fitting such as the
fitting 406 illustrated in FIG. 29. Sensor port 414 is provided
with a diameter D.sub.2 sized to receive a temperature or other
sensor. Outlet port 412 is spaced a distance S.sub.1 from the
bottom of a flange portion of the body component 402. The center of
outlet port 412 is spaced a distance S.sub.2 from the center of the
sensor port 414.
[0136] An exemplary embodiment of a lid component 404 of the bubble
trap assembly 400 is illustrated in FIGS. 34-37. Lid component 404
includes a lid 416 sized and shaped to enclose the opening at the
top of the chamber 408 of the body component 402 of the bubble trap
assembly 400. Lid component 404 also includes an upwardly-extending
inlet port 418, which is configured for mating connection to a
source of supplemental fluid such as a water bag. Specifically, a
water bag can be connected to inlet port 418 to permit the flow of
water from the water bag (not shown) into the bubble trap assembly
400. Lid component 404 also includes a downwardly-extending wall
420 that provides for an extension of the inlet port 418 into the
interior of the chamber 408 of the bubble trap assembly 400.
[0137] As is illustrated in FIG. 37, the wall 420 that extends the
inlet port 418 terminates at an angled tip 422. The inlet port 418
is provided with a height H so that it can be mated to a source of
water. The inlet port 418 is tapered at an angle .alpha. to
facilitate sealing engagement between the inlet port 418 and the
water supply (not shown). Also, an upper end of inlet port 418 is
provided with a diameter D.sub.3 suited for mating engagement with
a water supply and for the flow of water and air (as described
below).
[0138] Although it is shown only in phantom in FIG. 29, it will be
understood that the wall 420 that extends inlet port 418 into the
interior of chamber 408 extends downwardly, substantially parallel
to the rear wall of chamber 408. The tip 422 of the wall 420, and
the length of the tubular wall 420, are configured such that the
tip 422 terminates at a point below the axis of the inlet port 410
of the body component 402. The tip 422 of the tubular wall 420 also
extends to a position above the axis of the outlet port 412
provided on the body component 402. In other words, the tip 422 of
wall 420 extends downwardly into the chamber 408 to an elevation
above that of outlet port 412 and below that of inlet port 410.
[0139] Referring generally to FIGS. 29-37, the operation of bubble
trap assembly 400 will now be described. As is indicated by the
arrows shown in FIG. 29, circulating water will enter the bubble
trap assembly 400 through the inlet port 410; the circulating water
will exit the bubble trap assembly 400 through outlet port 412 and
fitting 406; and supplemental water will enter the bubble trap
assembly 400 through the inlet port 418 in the lid component 404 of
the bubble trap assembly 400.
[0140] The chamber 408 of the bubble trap assembly 400 is
substantially enclosed by virtue of the engagement between the lid
416 of the lid component 404 and the upper surface of the body
component 402. As water (or another liquid or fluid) is circulated
through the system, air bubbles or air otherwise entrained within
the circulating water will be trapped within the chamber 408. The
circulating water received in the chamber 408 flows toward the
bottom of the chamber 408 and then outwardly through the outlet
port 412 and the outlet fitting 406. A small reservoir of water
will form in the chamber 408 as indicated by the water level 421
illustrated in FIG. 29. The air that separates from the circulating
water within the chamber 408 accumulates at the top of chamber
408.
[0141] In operation, circulating water with air bubbles enters the
bubble trap chamber 208 by an inlet tube 410 near the top of the
bubble trap assembly 400. Air collects in the top of the chamber
408 while the circulating water falls to the bottom and leaves by
the outlet 412 and the outlet fitting 406. A third tube, defined by
the wall 420, is connected to the reservoir and enters the top of
the bubble trap assembly 400, normally terminating at a tip 422
positioned below the water surface within the chamber 408. As the
volume of trapped air increases, it lowers the water surface 421 in
the bubble trap chamber 408. When the water surface 421 is below
the level of the tube 420 from the supply reservoir, air bubbles
are formed in the tube 420 and pass upwardly through the tube 420
into the water supply bag. To avoid bubbles blocking the water tube
420 and inlet tube 418 from the reservoir, the internal diameter is
preferably about 3/8 inch or greater. The length and shape of the
tube 420, and the internal volume of the bubble trap chamber 408,
are selected to collect an optimum amount of air bubbles when the
system according to this invention is operating. The water level
421 preferably remains sufficiently high to avoid recirculation of
air through the outlet port 412 at the lower end of the chamber
408.
[0142] Accordingly, the bubble trap assembly 400 removes air from
circulating water and allows the air to return to the water supply
reservoir. Although the bubble trap assembly (400 or 150) is not a
critical feature of the system according to this invention, the
bubble trap assembly helps to prevent air from blocking water
circulation, which blockage could affect the operation of the
system. Also, the water pump of the system may not operate properly
if it becomes filled with air.
[0143] The bubble trap assembly 400 is particularly beneficial for
use with a compact version of the system that is capable of being
attached to an I.V. pole. In such a system, there is no room for a
built-in open reservoir into which circulating air could simply
vent through the water surface. Instead, a compact version of the
system utilizes an external reservoir such as a bag of water. A bag
is preferably used because it can change volume with no substantial
change in pressure and because it is light, easy to change, and
easy to hang on the I.V. pole. However, the use of an external
reservoir such as a water bag closed the water circulating system
and, therefore, the bubble trap assembly 150 or 400 is adapted to
allow circulating air to be displaced into the reservoir bag where
it has no effect on the operation of the system. Displaced air is
automatically replaced with its own volume of supplemental water
form the reservoir.
[0144] Referring to FIG. 41, another preferred embodiment of a back
plate assembly adapted for use in the supply unit is illustrated.
It differs from the assembly illustrated in FIG. 11A in that it
includes a bubble trap assembly 400. Other modifications are also
illustrated in FIG. 41.
[0145] Preferred features of a water pump and water heater assembly
138 are illustrated in FIG. 16. Assembly 138 includes a water pump
190 as well as a water heater 192. Water pump 190 and water heater
192 are mounted by means of a heater and pump strap 194 and a screw
196 to a pump base 198.
[0146] Referring now to FIG. 17, an enlarged view of manifold
assembly 140 is provided. Manifold assembly 140 provides delivery
tube port 130 into which an end of the delivery tube assembly 104
can be inserted. Further details of the connection between delivery
tube assembly 104 and manifold assembly 140 will be provided later
with reference to FIGS. 26A and 26B.
[0147] FIG. 18 illustrates preferred features of cover assembly 128
of supply unit assembly 102. Cover assembly 128 includes a main
housing 200. Display printed circuit board 178 (illustrated in FIG.
14) can be mounted to main housing 200, and a membrane panel 202
can be provided for user control of the supply unit assembly 102.
Main housing 200 is provided with a magnetic latch 204. Cover
assembly also includes a housing door 206 which is mounted to main
housing 200 by means of a hinge 208. A magnetic plate 210 on
housing door 206 provides for releasable engagement between housing
door 206 and main housing 200 in order to maintain housing door 206
in the closed position during operation of apparatus 100.
[0148] Preferred features of membrane panel 202 are illustrated in
FIG. 19. Membrane panel 202 includes a display window 212 through
which a digital temperature display in the form of an LED or LCD
display can be viewed by the user. Membrane panel 202 also includes
windows for alarm indicators such as a window 214 for a "WATER LOW"
indicator, a window 216 for a "SYSTEM FAILURE" indicator, and a
window 218 for a "HIGH TEMP" indicator, a window 220 for a
"CARTRIDGE" indicator, and a window 222 for a "BLOCKED TUBE"
indicator. A mute symbol 224 is provided on membrane panel 202 as
well as an "ON/OFF" indicator. Up and down arrows 228 and 230
respectively are also provided on membrane panel 202 for increasing
or decreasing a set temperature.
[0149] Although not shown in the appended figures, an optical
detector is optionally provided as part of the system in order to
detect water that might enter the air passages. For example, an
optical detector can be provided to detect the leakage of water if
water were to leak from the water passage to the air passage by
means of the vapor exchange cartridge. If the membrane material of
the exchanger cartridge should weaker or fail, water could enter
the air stream.
[0150] The preferred detector utilizes a light beam that passes
through the air stream leaving the cartridge. The intensity of the
light beam is continuously measured during operation of the system.
Drops of water in the air stream tend to attenuate the light beam.
If the intensity of the light beam drops below a preset value, the
operating software can be configured to close the air inlet
solenoid and cause a "system failure" alarm in order to shut off
the system.
[0151] FIG. 20 provides a perspective view of main housing 200 of
cover assembly 128. Main housing 200 has an opening 232
corresponding in size to membrane panel 202 (see FIG. 19). Main
housing 200 also includes an opening 234 for access to the delivery
tube port 130 in manifold assembly 140 (see FIG. 17). Main housing
200 also includes a base portion 236 to provide full coverage of
back plate assembly 126 even when housing door 206 is in the open
position as illustrated in FIG. 18.
[0152] As is illustrated in FIG. 21, housing door 206 of cover
assembly 128 includes a pair of recessed portions 238 and 240.
These recessed portions 238 and 240 of housing door 206 conform to
the base portion 236 of main housing 200 to provide a closed
housing when housing door 206 is in a closed position (not shown).
It will be understood that exchanger 110 will be enclosed between
surfaces of main housing 200 and housing door 206 when housing door
206 is in the closed position. Nevertheless, when opened by a user
of the system, housing door 206 provides easy access to exchanger
110 for maintenance and/or replacement.
[0153] Referring now to FIG. 22, preferred features of delivery
tube assembly 104 are illustrated. Delivery tube assembly 104
includes an inlet fitting 242 on which three o-rings 244, 246, and
248 are mounted for sealing engagement with an interior surface of
manifold assembly 140 (see FIG. 17). Delivery tube assembly 104
also includes an extruded tube 250, which is preferably provided
with a length of about 7 feet to extend between supply unit
assembly 102 and the patient. Delivery tube assembly 104 also
includes an outlet fitting 252 mounted at the opposite end of
extruded tube 250 in order to facilitate connection to a nasal
cannula or mask, which makes it possible to introduce heated and
humidified gas to the respiratory tract of the patient.
[0154] Generally, the inlet fitting 242 of the delivery tube
assembly 104 is provided to retain the delivery tube assembly in
place; to allow quick, reliable connection and disconnection of the
delivery tube assembly; to connect two (2) water passages and one
(1) air passage; and to maintain separation between the water and
air passages. The delivery tube has a central air channel enclosed
by two (2) water channels. Each channel is connected to a
corresponding channel in the base connector. The air channel is
axial and passes straight through the connector. The two (2) water
channels are brought out through the sides of the connector
diametrically opposite one another.
[0155] When the connector is inserted into a manifold such as
manifold 140 in the base unit and releasably locked into place, the
two (2) water channels in the connector line up with matching water
channels in the manifold. Ball valves closing the manifold water
channels are automatically opened by the action of inserting the
connector, so that when the connector is fully inserted and locked
into position the water can flow from the manifold into a water
channel in the connector, and thence into a water channel in the
delivery tube. Returning water from the delivery tube flows through
the opposite side channel of the connector and into the manifold
through the matching channel.
[0156] Leakage to the outside is prevented by an o-ring seal around
the connector. Leakage to the air channel is prevented by two (2)
o-rings around the connector between the water channels and the air
channel. All three (3) o-rings are compressed between the connector
and the manifold when the connector is inserted, so that water and
air passages are effectively isolated.
[0157] Regarding the manifold (such as manifold 140), the manifold
is provided to make connections with the delivery tube; to maintain
separation of water and air passages; and to retain water in the
base unit when the delivery tube is disconnected. The preferred
manifold 140 has all three (3) fluid passages integrated into a
single block, providing improved dimensional stability as well as
being compact and allowing quick replacement of delivery tubes. In
operation, the manifold compresses the o-rings of the delivery tube
base fitting and effectively separates the water and air
circulations. As an additional safety measure, a seep hole is
preferably provided in the manifold. Any water that passes the
first of the o-rings separating the water and air circulation leaks
out through this seep hole and does not reach the second o-ring
seal. Water leaks into the air passage are therefore minimized or
preferably avoided entirely, even if the first o-ring fails.
[0158] Regarding the tip connector (such as the outlet fitting 252)
of the delivery tube, the tip connector terminates the delivery
tube; connects outgoing and return fluid passages in the delivery
tube; and provides for connection to the air passage. The tip
connector permits rapid assembly and reduces the resistance to
water flow through the delivery tube assembly. The connector has an
elongated, tapered axial tube that makes a gas-tight fit with the
central air passage in the delivery tube. The shell of the
connector has a slight inside taper that provides a water-tight
seal with the outside of the delivery tube after assembly. Internal
passages in the tip connector allow water to flow between the two
(2) water channels, removing the need to modify the tubing
material.
[0159] Exemplary details of additional preferred embodiments of the
delivery tube assembly will now be described.
[0160] Referring to FIG. 23, the extruded tube 250 includes an
outer tube 254 and an inner tube 256, wherein inner and outer tubes
254 and 256 share a common axis. Inner tube 256 is connected to
outer tube 254 by means of a pair of webs 258A and 258B that extend
across the annular space between outer tube 254 and inner tube 256.
Inner tube 256 defines an inner lumen 260 through which gas flows
from the supply unit assembly 104 toward the patient.
[0161] The inner tube 256, outer tube 254, and webs 258A and 258B
together define a pair of outer lumens each having a semi-circular
cross-sectional shape. More specifically, a first outer lumen 262
and a second outer lumen 264 are defined by tubes 254 and 256 and
webs 258A and 258B. First and second outer lumens 262 and 264
provide passages for flow of warming fluid such as water that flows
outwardly from supply unit assembly 102 into delivery tube assembly
104 and then returns from delivery tube assembly 104 to supply unit
assembly 102 for re-circulation. It is the heat transferred from
warmed fluid in outer lumens 262 and 264 to gas within inner lumen
260 that provides the heating mechanism of the delivery tube.
[0162] It should be noted that outer lumens 262 and 264 according
to this invention need not be dedicated to a particular water or
fluid flow direction. More specifically, outer lumen 262 can
provide for outward water flow toward the patient or it can provide
for return flow toward the supply unit assembly 102. Likewise,
outer lumen 264 can provide for outward water flow toward the
patient or it can provide for return flow toward the supply unit
assembly 102. The direction of flow through the lumens will be
determined by the orientation of inlet fitting 242 with respect to
the extruded tube 250, which is not critical, and the orientation
of the inlet fitting 242 in port 130 of manifold assembly 140,
which is not critical. In other words, inlet fitting 242 of
delivery tube assembly 104 can be assembled without regard for
alignment of a particular outer lumen 262 or 264 with respect to
the orientation of the inlet fitting 242.
[0163] Referring now to FIGS. 24A through 24D, inlet fitting 242 of
delivery tube assembly 104 is provided with external,
circumferential grooves 266, 268, and 270. These grooves 266, 268,
and 270 accommodate the o-rings 244, 246 and 248 shown in FIG. 22.
It will be understood that, when inlet fitting 242 is inserted into
manifold assembly 140 at the delivery tube assembly port 130,
o-ring 248 will provide a seal between inlet fitting 242 and an
inner surface of the manifold, and o-rings 244 and 246 will provide
a fluid-tight seal between inlet fitting 242 and a smaller diameter
region in the inside of the manifold. Inlet fitting 242 is also
provided with ports 272A and 272B for reasons that will be made
clear later.
[0164] An opening (not shown) is provided in the wall of inlet
fitting 242 at a location between o-ring grooves 266 and 268. This
opening provides a vent for any water that may leak past one of the
o-rings 244, 246. This vent helps to prevent any leaked water from
entering the air line so that circulating water will not be
delivered with the air to the patient. A port 313 in the manifold
298 (as shown in FIGS. 27A and 27B) provides a path for the flow of
any leaked water out of the system so that it will not be entrained
in the air supply that is delivered to the patient.
[0165] Also, inlet fitting 242 has a tubular inner extension 274
sized to fit within inner lumen 260 of inner tube 256 of tube 250
so as to create a seal between the outer surface of inner extension
274 and the inner surface of inner tube 256. Inlet fitting 242 is
also provided with intermediate extensions 276A and 276B which are
sized to extend within outer lumens 262 and 264 of extruded tube
250. More specifically, outer surfaces of intermediate extensions
276A and 276B form a seal against the inner surface of outer tube
254, and inner surfaces of intermediate extensions 276A and 276B
are sized to create a seal with outer surfaces of inner tube 256.
In other words, intermediate extensions 276A and 276B are
configured for sealing engagement with first and second outer
lumens 262 and 264.
[0166] A flow passage 282 is provided in intermediate extension
276A to permit fluid flow between an outer lumen of extruded tube
250 and the port 272A in inlet fitting 242. Similarly, a flow
passage 284 is provided in intermediate extension 276B to provide
such fluid flow between an outer lumen of tube 250 and port 272B.
Inlet fitting 242 is also provided with an outer extension 278,
wherein an inner surface of outer extension 278 is provided for
sealing engagement with an outer surface of outer tube 254 of
extruded tube 250. The outer surface of outer extension 278 is
preferably provided with ridges or other surface treatments to
facilitate the insertion of inlet fitting 242 into the manifold
assembly 140 of the supply unit assembly 102 by a user. Such
surface treatments can be selected to provide an ornamental
appearance that identifies the manufacturer of the delivery tube
assembly 104. The outlet fitting 252 can be provided with a
matching surface treatment.
[0167] In order to facilitate insertion of an end of extruded tube
250 into inlet fitting 242, wherein outer tube 254 extends into a
recess between outer extension 278 and intermediate extensions 276A
and 276B, a pressure release opening 280 is provided to release
trapped air upon assembly. A flow passage 286 extending along the
axis of inlet fitting 242 is provided to permit gas flow from the
supply unit assembly 102 into the inner tube 256 of extruded tube
250.
[0168] Inlet fitting 242 is also provided with a pair of opposed
detents 243A and 243B. Detents 243A and 243B provide for
orientation and locking engagement between inlet fitting 242 of
delivery tube assembly 104 and supply unit assembly 102. Further
details of this feature will be described later with reference to
FIG. 28.
[0169] Although not shown, inlet fitting 242 can be provided with a
radially extending flange about its circumference at a location
adjacent to opposed detents 243A and 243B. Also, it should be noted
that the configuration of the outer surface of inlet fitting 242 is
provided with a combination of ornamental features and surface
configurations. Such ornamental features provide the configuration
of the inlet fitting 242 and the tubular assembly 104 with an
ornamental appearance.
[0170] Referring now to FIGS. 25A through 25C, preferred features
of outlet fitting 252 are illustrated. Referring specifically to
FIG. 25C, outlet fitting 252 is provided with a tubular inner
extension 288 sized to fit in a sealing manner within inner tube
256 of extruded tube 250. Outlet fitting 252 also includes
semi-circular intermediate extensions 290A and 290B configured to
extend within outer lumens 262 and 264 of extruded tube 250. Like
extension portions 276A and 276B of inlet fitting 242, extensions
290A and 290B of outlet fitting 252 need not be dedicated to a
particular outer lumen. Accordingly, during assembly of outlet
fitting 252 and extruded tube 250, a particular one of extension
portions 290A and 290B need not be mated to a particular one of
outer lumens 262 and 264.
[0171] Outlet fitting 252 also includes a tubular outer extension
292 which is configured to provide sealing contact with an outer
surface of outer tube 254 of extruded tube 250. As with outer
extension 278 of inlet fitting 242, outer extension 292 of outlet
fitting 252 can be provided with a surface treatment, such as the
longitudinally extending ridges shown in FIGS. 24A and 25A, to
facilitate connection of outlet fitting 252 to a nasal cannula.
Surface treatments can also be applied to the outer surface of
outlet fitting 252 as an indicator of the identity of the
manufacturer or source of the delivery tube assembly 104.
[0172] Defined between intermediate extensions 290A and B and inner
extension 288 is an annular recess 294 which is deeper than the
recess between intermediate extensions 290A and 290B and outer
extension 292. When extruded tube 250 is inserted into outlet
fitting 252, annular recess 294 provides a passage for fluid flow
communication of warming fluid between outer lumens 262 and 264 of
extruded tube 250. In other words, when outer tube 254 of extruded
tube 250 bottoms in the recess between intermediate extensions 290A
and 290B and outer extension 292 of outlet fitting 252, a portion
of annular recess 294 remains open, thereby providing an annular
region for fluid flow between the first and second outer lumens 262
and 264 of the tubing. Outlet fitting 252 also includes a flow
passage 296 through which gas can flow from the inner lumen 260 of
extruded tube 250 to a cannula connected to outlet fitting 252 and
for delivery of gas to the patient.
[0173] Although not shown, the outlet fitting 252 can be modified
such that the flow passage 296 is shortened. Also, external
features of the outlet fitting 252 provide the outlet fitting 252
with an ornamental appearance by virtue of a variety of surface
contours and configurations.
[0174] FIGS. 26A and 26B illustrate preferred features of manifold
assembly 140 with inlet fitting 242 of delivery tubing assembly 104
inserted therein. As is best illustrated in FIG. 26B, water "W" is
introduced into a manifold block 298 through an inlet assembly 300,
which includes an elbow fitting. Water then enters port 272A (or
272B) for flow into and through flow passage 282 (or 284) in inlet
fitting 242. The heated water then flows through an outer lumen 262
(or 264) of the delivery tube 250, flows through the recess 294 in
outlet fitting 252, and returns through an outer lumen 264 (or 262)
of the delivery tube 250. The water then flows through flow passage
284 (or 282) in inlet fitting 242 to port 272B (or 272A). Water
then flows outwardly from manifold block 298 through an outlet
assembly 302. As described previously, the orientation of delivery
tube assembly 104 within manifold assembly 140, and the orientation
of extruded tube 250 with respect to inlet fitting 242, determine
the direction of flow through the ports of inlet fitting 242 and
the outer lumens of the delivery tube 250.
[0175] In this embodiment, outlet assembly 302 includes a ball
valve including a ball 304 and a spring 306. It will be understood
that spring 306 biases ball 304 against the flow opening when the
delivery tube assembly 104 is not connected to the port 130 of
manifold assembly 140. Accordingly, the ball valve provided by ball
304 and spring 306 prevents leakage of water from the supply unit
assembly upon removal of the delivery tube assembly 104 from the
manifold. A corresponding ball valve is also provided in inlet
assembly 300 in order to prevent the leakage of water (or other
heating fluid) from the system when the delivery tube assembly is
not in place.
[0176] Referring now to FIGS. 27A and 27B, block manifold 298
defines port 130 as well as ports for inlet assembly 300 and outlet
assembly 302. More specifically, as is illustrated in FIGS. 27A and
27B, the single port 130 of manifold 298 provides an outlet opening
316 for the flow of heating fluid such as water from the supply
unit assembly 102. Outlet opening 316 permits flow of heating fluid
from the supply unit for delivery into delivery tube assembly 104
via port 272A or 272B in inlet fitting 242 of assembly 104
(depending upon the rotational orientation of inlet fitting 242
within manifold 298).
[0177] Port 130 also provides an inlet opening 318 for the return
flow of heating fluid such as water into the supply unit assembly
102 for recirculation. Inlet opening 316 permits flow of heating
fluid from delivery tube assembly 104 into the supply unit via port
272A or 272B in inlet fitting 242 of assembly 104 (depending upon
the rotational orientation of inlet fitting 242 within manifold
298).
[0178] Port 130 also provides an outlet opening 320 for the flow of
heated and humidified air from the supply unit 102. Outlet opening
320 permits flow of air from the supply unit into delivery tube
assembly 104 via passage 286 in inlet fitting 242.
[0179] Accordingly, it will be appreciated that air and water
delivery from the supply unit, as well as water return to the
supply unit, are accomplished by means of a single port (such as
port 130) in the supply unit. It will also be appreciated that air
and water can be received into the delivery tube assembly, and that
water can be delivered from the delivery tube assembly, by means of
a single fitting (such as inlet fitting 242) in the delivery tube
assembly. These preferred features of the invention facilitate
rapid, accurate, and predictable connection between the delivery
tube assembly and the supply unit assembly. In other words, only a
single delivery tube inlet fitting need be inserted into a single
supply unit port in order to establish water and air flow
connections.
[0180] Manifold 298 is provided with female pipe threads 308 for
engagement of inlet assembly 300. Manifold 298 is also provided
with female pipe threads 310 for engagement of outlet assembly
302.
[0181] Port 130 of manifold 298 includes a portion 312 having a
larger diameter as compared to a portion 314 with a small diameter.
Q-ring 248 of inlet fitting 242 provides a fluid-tight seal against
the inner surface of large diameter region 312. O-rings 244 and 246
of inlet fitting 242 provide for fluid-tight seals against inter
surfaces of smaller diameter region 314.
[0182] Referring now to FIG. 28, which provides a cut-away view of
a portion of main housing component 200, a preferred locking
arrangement for locking assembly 104 to assembly 102 is
illustrated. Specifically, opening 234 of housing component 200 is
provided with a pair of opposed recesses 322A and 322B, which are
sized and positioned to receive the detents 243A and 243B of inlet
fitting 242. Opening 234 is also provided with a pair of ramps 324A
and 324B, each of which extends from one of the recesses 322A and
322B.
[0183] Also, a series of four detents 326A-326D are provided on a
surface of component 200 adjacent opening 234. Detents 326A-326D
are positioned to provide stops to limit the rotation of fitting
242 with respect to the manifold. More specifically, detents
326A-326D are contacted by detents 243A and 243B upon rotation. The
arrow 328 in FIG. 28 indicates a direction of rotation for engaging
fitting 242 in manifold 298. Although counterclockwise rotation for
engagement is illustrated in FIG. 28, it is actually preferred for
rotation to be clockwise for engagement, as is described later. To
accomplish clockwise rotation for engagement, the mirror image of
FIG. 28 can be employed.
[0184] Upon insertion of fitting 242 within opening 234 and
rotation of fitting counterclockwise, detents 243A and 243B of
inlet fitting 242 will stop after about a quarter turn upon contact
with detents 326B and 326C. Detents 326B and 326C are also
positioned to orient fitting 242 rotationally with respect to
manifold 298 so as to provide alignment of ports 272A and 272B of
inlet fitting 242 with ports 316 and 318 of manifold 298. Arrow 328
can be provided on a surface of housing component 200 in order to
indicate a direction of rotation to engage the fitting 242 within
the manifold 298.
[0185] In order to release fitting 242 from the opening 234
illustrated in FIG. 28, the fitting 242 is rotated in the clockwise
direction until detents 243A and 243B contact detents 326A and
326D. Upon such contact, detents 243A and 243B are aligned with
recesses 322A and 322B so that the fitting 242 can be extracted
from the opening 234.
[0186] It will be appreciated that a locking structure such as the
one illustrated in FIG. 28 can provide a quarter-turn,
bayonet-style locking engagement between the fitting and the supply
unit. Such a connection provides a reliable, one-step procedure for
connecting the delivery tube assembly.
[0187] The general flow of heating fluids such as water W and
therapeutic gas such as air A through the apparatus 100 will now be
described with reference to FIGS. 11A, 11B, 15A, 15B, 16, 17, 26A,
and 26B. Reference can also be made to the schematic diagram
provided in FIG. 9.
[0188] Referring first to the flow of water W through apparatus
100, water W.sub.1 is introduced into apparatus 100 via bubble trap
assembly 150 from a water source such as a water bag. Water W.sub.2
flows outwardly from bubble tube assembly 150 and into water pump
190. Water W.sub.3 then flows out from water pump 190, and water
W.sub.4 then flows into water heater 192 for heating. Water W.sub.5
flows outwardly from water heater 192, and water W.sub.6 then flows
into manifold assembly 140 through inlet assembly 300. After
flowing through delivery tube assembly 104 and returning to supply
unit assembly 102, water W.sub.7 flows outwardly from manifold
assembly 140 through outlet assembly 302. The water W.sub.7 then
flows into an elbow for delivery as water W.sub.8 into the membrane
cartridge 110 (FIG. 9). Water W.sub.9 flows outwardly from
cartridge 110 and into bubble trap assembly 150. The water is then
recirculated as water W.sub.2 through apparatus 100, together with
additional water W.sub.1 received from water bag 116 (FIG. 9).
[0189] Regarding the flow of air A through apparatus 100, air
A.sub.1 is introduced into the apparatus from a source into inlet
port 152. Air A.sub.2 then flows to exchanger 110 (FIG. 9) for
humidification by means of the transfer of water vapor. Air A.sub.3
then flows from exchanger 110 into elbow 142. Air A.sub.4 is then
directed into manifold assembly 140 for delivery into the delivery
tube assembly and to the patient.
[0190] Delivery tube assembly 104 can be easily and efficiently
connected to supply unit assembly 102 by simply inserting an end of
inlet fitting 242 into the port 130 of supply unit assembly 104, as
will be described in further detail later. Accordingly, this simple
insertion provides fluid flow communication between the supply unit
and the delivery tube for the flow of gas from the supply unit
toward the patient. Simultaneously, insertion of inlet fitting into
port 130 provides fluid flow communication for warming fluid, such
as water, which can then flow from the supply unit into the
delivery tube and return from the delivery tube into the supply
unit in a leak-free environment.
[0191] Also, it is significant to note that the interconnection
between inlet fitting 242 and port 130 provides for an axially
extending flow passage for gas from supply unit assembly 102 into
the inner tube of the delivery tube assembly 104. Also, at the
opposite end, an axial gas flow passage is provided for flow from
the inner tube of the delivery tube into the outlet fitting and
from the outlet fitting into a nasal cannula. The provision of such
axial flow passages has been discovered to provide a reduction in
pressure drop as the gas flows from the supply unit through the
delivery tube to the patient.
[0192] In use, the apparatus in this embodiment is adapted to be
clamped to a standard IV pole or hanger; ideally, it should be
mounted at approximately the same height as the patient's head
although a range of about four (4) feet above or below this level
should be acceptable. After the apparatus is clamped to the IV pole
or hanger and the power cord is plugged in, the water reservoir is
then filled. If the water supply has a high mineral content,
distilled water can be used. Otherwise, tap water is acceptable.
The reservoir tube is connected to the apparatus in order to
provide fluid flow into the apparatus.
[0193] The delivery tube is then connected to the port on the
apparatus. In order to do so, the delivery tube connector is
pressed firmly into the connection port and rotated 1/4 turn
clockwise (preferably) until it locks in place.
[0194] The power for the apparatus is then switched on and the
temperature setting is adjusted by pressing and holding an arrow to
display the set temperature. The up and down arrows are used to
change the setting. Upon the release of the arrow, the actual
temperature is displayed for all temperatures up to about
45.degree. C. At higher temperatures, the display can read
"HI".
[0195] A nasal cannula is then connected to the opposite end of the
delivery tube, and the wall source of air, oxygen or a blend is
connected to the inlet port of the apparatus. Using an external
flow regulator, the flow rate of the air, oxygen or blend can be
adjusted to a desired setting such as a setting between about 20
and about 40 lpm for adults, for example.
[0196] After the apparatus has reached operating temperature,
wherein the temperature indicated on the front panel of the
apparatus equals the set temperature, the nasal cannula is fit to
the patient. A periodic check for alarm conditions may be made.
However, the apparatus may be configured to shut down if
temperature safety limits are exceeded or if the water level is
low.
[0197] The delivery tube should be changed for each patient. To do
so, the base of the delivery tube is rotated 1/4 turn (preferably
counter-clockwise) and pulled straight down (when the apparatus is
mounted on the IV pole). A connector of a new delivery tube is then
inserted in the receptacle by pressing it firmly in place and
rotating it a 1/4 turn (preferably clockwise) to lock it in
place.
[0198] The humidifier cartridge can be changed periodically. In
order to do so, the water reservoir is disconnected from the
apparatus and the cover to the cartridge chamber is opened. Water
and air tubes from the cartridge are disconnected and reconnected
to a new cartridge. The new cartridge is then pressed into place
and the cover is closed.
[0199] In order to clean the apparatus, the delivery tube can be
removed and a drain tube can be inserted so that the water in the
apparatus can be drained. The delivery tube is then replaced. A bag
of cleaning solution can then be connected to the apparatus and the
apparatus can be turned on in order to circulate the cleaning
solution without heating. The power can then be shut off and the
apparatus can be drained of cleaning solution, and the delivery
tube can be discarded. The cleaning solution bag is then removed
and replaced with a water bag. A new delivery tube is then fit into
place, and the apparatus is again ready for use.
[0200] Referring now to FIGS. 38-40, a functional overview of a
preferred embodiment of the system will now be described. Referring
to FIG. 38, the software that supports the system is divided into
functional areas or logical "modules" which provide specific
related functionality. A System Initialization module is
responsible for the correct initialization of the system at power
up. This section of the software executes whenever the processor is
reset. A System Controller module is the code that executes after
system initialization or plug-in. The Timing Subsystem module
provides overall system timing. The Diagnostics and Communication
Subsystem module is responsible for formatting system parameters
into human readable form and transmitting this data to a terminal.
The Device Control Subsystem module provides facilities for the
control of the gas solenoid and heater. The Error Handling
Subsystem module provides functions to monitor the various system
parameters and the required logic to initial the appropriate error
handling response. The User Interface Subsystem module provides
keypad scanning and display control. Finally, the System Monitoring
Subsystem module implements routines for reading system
sensors.
[0201] Referring now to FIGS. 39 and 40, plug-in initialization is
performed when a processor reset occurs. After successful of
plug-in initialization, the system enters the plug-in state. When a
power key press is detected, and the system transitions to power-on
initialization. Following successful completion of power-on
initialization, the system enters the power-on state--this is the
main operating state of the instrument during which the
humidification process occurs. When a power-on/off key press is
detected during power-on, the system will transition to a cool down
mode. When the power-on/off and mute keys are simultaneously
depressed, the cleaning mode flag is set and the system enters
cleaning mode. Finally, when the system encounters an unrecoverable
error, it enters system failure mode.
[0202] A flow diagram illustrating one preferred embodiment of
software adapted for use with this invention is illustrated in FIG.
40.
[0203] The apparatus in this embodiment confers several significant
advantages. The apparatus is capable of producing a high flow of
highly humidified air (relative humidity greater than 95%),
virtually free of droplets, at body temperature or above. The water
content at 41.degree. C. is about 40-50 mg/liter, which is about
four times higher than can be achieved by humidification at room
temperature. Because the water is almost all in the vapor phase,
there is little or no impaction of water droplets in the upper
airway of the patient, and the vapor content is available to the
entire pulmonary airway. Heating of the air delivery tube using
circulating hot water maintains a substantially constant
temperature between the apparatus and the patient, thereby avoiding
condensation when the air is delivered with high water content.
[0204] Unlike conventional humidifiers, which may rely on either
evaporation from a liquid surface or on aerosolization of water,
the apparatus according to this invention need not have any direct
interface between water and air. Instead, the apparatus humidifies
by diffusion of water vapor through a microporous membrane into a
flowing air stream. The membrane pore size, which is preferably
less than about 0.1 micron, excludes particles so that the output
air is substantially free of bacteria, viruses and most
allergens.
[0205] The casing protects electrical components from accidental
water spills. Also, it is preferred that all external parts of the
apparatus have a service temperature not exceeding about 41.degree.
C. The system and apparatus are preferably protected against
overheating by software that monitors water temperature.
Specifically, an alarm sounds if the temperature rises above the
set point. Also, the apparatus is preferably shut off if the
temperature continues to increase.
[0206] In order to maintain bacteriological safety, air and water
are preferably separated by a biological barrier so that, even if
the water circulation should become colonised by bacteria, the air
would remain substantially sterile. In order to prevent circulating
water from entering the air tubing and being forced toward the
patient's airway, the presence of liquid water in the air tubing
can cause an instant shut down of the unit.
[0207] Treatment of Respiratory Tract Conditions
[0208] The apparatus according to this invention has been
discovered to confer significant and surprising benefits when used
for the treatment of the respiratory tract or for respiratory tract
therapy. The apparatus has been discovered to be uniquely adapted
for the introduction of heated and humidified air to the
respiratory tract of a human patient. The portability of the
apparatus has made it easily adaptable for home use as well as for
clinical use such as in the hospital setting.
[0209] It has been recognized that rhinitis, or the inflammation of
the soft tissues in the nasal airway, can be caused by viral
infections such as the common cold and influenza, and by 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 essentially includes a "conveyer belt" formed by a layer of
mucus, which 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 "conveyer belt" fails because the mucus is
insufficient or too thick or if the cilia do not "beat" correctly,
bacterial infection and inflammation can result.
[0210] It has been discovered that the introduction of heated and
humidified air into the respiratory tract helps to treat rhinitis
by 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 (up to
42.degree. C.) is believed to reduce the rate of viral replication.
Accordingly, breathing of heated and humidified air has been
discovered to be a beneficial treatment for many types of
rhinitis.
[0211] The introduction of heated and humidified air, by means of
an apparatus according to this invention for example, has been
discovered to provide several unique advantages as compared to
conventional humidifiers in connection with the treatment of
rhinitis and other respiratory tract conditions. For example, the
apparatus of this invention prevents contact between bulk water and
air so that water-borne pathogens cannot enter the airflow. Also,
by use of an apparatus according to this invention, water is
present in the output air only as vapor in the virtual absence of
aerosol particles so that particle deposition in the airway is
minimized.
[0212] It has been discovered that the use of a
temperature-controlled delivery tube according to this invention
ensures 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. All these benefits can be accomplished
according to this invention by delivering air through a nasal
cannula so that the patient can continue normal activities with
minimal interference.
[0213] It has also been discovered that the treatment method
according to this invention provides improved 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.
[0214] Despite intensive research, 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 (e.g.
steroids) and to relax the bronchial smooth muscle directly (e.g.
.beta.-adrenergic agonists), there have been concerns raised over
abuse of the medications and the side-effects associated with such
medications. For this reason, a treatment is needed that can help
control the symptoms of asthma without the risks and side-effects
of the drugs in present use.
[0215] It has been discovered that 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, in a preferred treatment method, a
patient is fit 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.
EXAMPLE 1
[0216] An evaluation was conducted to determine the impact of
breathing air at or above body temperature and saturated with water
vapor on pulmonary function in asthmatics with rhinitis. Part of
the bronchoconstriction occurring in asthmatics with rhinitis is
believed to driven by a nasopulmonary reflex stimulated by cooling
and drying of the nasal mucosa. Breathing warmed humidified air has
been discovered to remove the stimuli of cold and dryness and
remove or reduce this component of bronchoconstriction.
[0217] Asthmatic subjects studied in the evaluation had mild to
moderate asthma, with Forced Expiratory Volume after one second
(FEV.sub.1) between 45% and 75% normal at screening, were
non-smokers and had no other diagnosed conditions, or their
conditions were stable and controlled. Subjects were asked not to
use asthma medication on the day of the study. Control subjects had
normal pulmonary functions. All subjects were asked to fill in a
rhinitis score questionnaire for 14 consecutive days. Five control
and 11 asthmatic subjects were studied. Valid data were obtained
from 5 controls and 9 asthmatic subjects (age range 34-78).
[0218] The following protocol was used in the study: [0219] 1.
Baseline Pulmonary Function Test (PFT) and nasal resistance
measurement. [0220] 2. One hour of placebo breathing using a
delivery system set to <5 lpm flow at 34 C, connected to the
nasal cannula via a 6-foot oxygen tube. With this arrangement the
air emerged from the cannula at approximately 26 C, and the water
content per liter was approximately 1/4 that at 41 C. [0221] 3.
Placebo PFT and nasal resistance measurements. There was a 15
minute interval between the end of the placebo period and the nasal
resistance measurements, because preliminary tests showed some
rapid changes in the first few minutes after the placebo period.
[0222] 4. One hour test breathing with a delivery system set at 20
lpm, 41 C, using a short nasal cannula. Air temperature at the
nasal prongs was 39-40 C. [0223] 5. Final PFT's and nasal
resistance measurement.
[0224] In most asthmatic patients there was a fall in both Forced
Vital Capacity FVC and FEV.sub.1 between baseline and post-placebo
measurements. Taking the asthmatic subjects as a group, FVC
increased between placebo and tests (p=0.03). FEV.sub.1 decreased
between baseline and placebo (p<0.01) and then increased between
placebo and tests (p=0.016). The FEV.sub.1/FVC ratio, PEF and
FEF.sub.25-50 did not change consistently between placebo and
test.
[0225] The following table summarizes changes from placebo to
treatment (as % change from placebo (see FIG. 42)):
TABLE-US-00001 Avg. Min Max p-value FVC 5 -6 11 .03 FEV.sub.1 5 -5
13 .02 PEF -15 -50 8 n.s. FEF.sub.25-50 12 -6 50 n.s. FEV.sub.1/FVC
0.7 -10 18 n.s.
[0226] The changes reported in FIG. 42 are averaged changes over
the group.
[0227] The evaluation described in Example 1 revealed that
FEV.sub.1 and possibly FVC increase after 1 hour of treatment (20
lpm, 41 C; temperature at nasal prongs 39-40 C) compared with 1
hour placebo. Almost all of the subjects, both control and
asthmatic, liked the treatments and felt comfortable using the air
delivery system. Some asthmatic subjects reported feeling that
their nasal airways were unusually clear after treatment.
[0228] FIG. 42 illustrates changes in FEV.sub.1 and FVC normalized
to baseline (left) and placebo (right) in asthmatic patients. Most
patients showed an increase in both between placebo and test.
[0229] In another aspect of the method according to this invention,
it has been discovered that the introduction of heated and
humidified air can reduce the discomfort associated with chronic
rhinosinusitis in cystic fibrosis patients. It has been recognized
that many cystic fibrosis patients have chronic rhinosinusitis due
to infection, inflammation, and thickened secretions, and therefore
require continuous medication. Many such patients receive repeated
surgical procedures to drain the paranasal sinus when medical
treatment fails, but the effect of such surgery can be short-lived.
Standard therapy can include saline nasal washes and antibiotics,
and corticosteroids if nasal polyps are present. Accordingly,
improvements to such treatments of rhinosinusitis are needed. This
is especially true in cystic fibrosis patients because they tend to
produce mucus that is scanty and thick, and the mucoliary transport
system is sometimes unable to clear bacteria from the nasal mucosa.
Also, the low secretion volume may leave the mucosa susceptible to
drying out and injury. Infection and injury can then lead to
inflammation. Similarly, the introduction of heated and humidified
air has also been discovered to reduce the symptoms of refractory
rhinosinusitis.
[0230] Chronic obstructive pulmonary disease (COPD) has also been
associated with symptoms that can be effectively treated by the
introduction of heated and humidified air by means of the apparatus
and method of this invention. For example, the delivery for 30
minutes of high flow, humidified, heated room-air delivered by
nasal cannula to COPD patients at about 20 liters per minute of
flow has been discovered to provide an effective alternative or
delivery system for oxygen in COPD patients.
[0231] It has also been discovered that high nasal flow using a
system according to this invention decreases the work of breathing.
Specifically, it has been discovered that the introduction of
heated and humidified air or breathing gas into the nasal
passageway of a patient decreases work of breathing. Most
preferably, heated and humidified breathing gas delivered at about
25 to about 35 liters per minute, thereby reducing the work of
breathing. Reduction of work of breathing is clinically significant
in COPD patients who may have three times normal work of breathing
and may also be malnourished.
[0232] The introduction of heated and humidified breathing gas
according to this invention also reduces the retention of carbon
dioxide (CO.sub.2) and decreases shortness of breath. Specifically,
COPD patients frequently have rapid shallow breathing which can be
inefficient at clearing carbon dioxide from the lungs and can lead
to feelings of breathlessness. As is illustrated in the following
Example, it has been discovered that high nasal flow can both
reduce work of breathing and reduce breathing rates in normal
subjects.
EXAMPLE 2
[0233] Ten (10) normal subjects and five (5) COPD patients were
studied.
[0234] For the normal subjects, work of breathing and respiratory
responses to heated and humidified flow were measured.
Specifically, flow from 0 to 25 liters per minute was administered
to the normal subjects at rest and during exercise. The results are
provided in FIGS. 43A and 43B. The results indicate that, at rest,
the mean work of breathing was reduced progressively by increasing
nasal flow. When nasal flow increased from 0 to 20 liters per
minute, the mean work of breathing fell by 42%. The results
indicate a preferred range of flow rates from about 15 to about 20
liters per minute.
[0235] In the same group of normal subjects, mean tidal volume
(i.e., the volume of air per breath) increased about 52% from 0.42
liters to 0.64 liters as nasal flow increased from 0 to 25 liters
per minute. The results indicated that minute volume (volume
breathed per minute) did not change significantly. Nevertheless, it
was discovered that the breathing pattern was significantly
changed. As the nasal flow increased, breathing became slower and
deeper. Slow deep breathing is believed to be more effective than
rapid shallower breathing in removing carbon dioxide from the
lungs. Also, rapid shallow breathing is associated with the
sensation of breathlessness (dyspnea) found in disease conditions
such as COPD and acute asthma attacks.
[0236] Preliminary data from normal subjects during exercise
indicated approximately 30% decrease in work of breathing when
nasal flow was increased from 0 to 25 liters per minute.
[0237] With regard to COPD patients at rest, the COPD patients had
a base line respiratory rate of 27 per minute as compared to 17 per
minute for the normal subjects. COPD patients showed about a 20%
increase in the mean duration of inspiration (Ti) when the nasal
air flow was increased from 0 to about 20 liters per minute while
respiratory time did not change. There was an 11% decrease in
overall respiratory rate. The longer Ti indicates a change to a
more comfortable and less labored breathing pattern. See the
results illustrated in FIG. 44.
[0238] Another respiratory tract condition, obstructive sleep apnea
(OSA), affects about 4% of men and about 2% of women. If left
untreated it can be associated with significant mortality. Another
condition, UARS (also known as respiratory effort-related arousal,
RERA), has been recognized only recently as pathological and in
need of treatment. Physiologically, upper airway resistance
syndrome (UARS) is caused by an increase in upper airway resistance
short of complete obstruction, and appears to lie on a continuum
between non-symptomatic snoring at one end and clinically
significant OSA at the other. Unlike OSA, UARS does not include
significant desaturation or obstructive apnea. However, the patient
has a slightly increased arousal index and number of awakenings,
with snoring and daytime sleepiness.
[0239] Although continuous positive airway pressure (CPAP) has been
proposed for the treatment of OSA and UARS, it has been discovered
that compliance with CPAP treatment is poor. Patient complaints
relating to non-compliance include feelings of claustrophobia and a
perceived lack of benefit. Also, many CPAP patients report
significant side-effects such as nasal congestion, dry nose or
throat, and discomfort associated with cold air. Epistaxis occurs
infrequently but can be severe, and chronic nasal congestion may
compromise a patient's ability to successfully utilize CPAP.
[0240] An obstructive apnea is defined as cessation of airflow for
an extended period of time (such as more than 10 seconds)
accompanied by an arousal or desaturation. It is believed that the
introduction of 100% humidified air at a flow rate of 20 liters per
minute can reduce the effects of OSA and UARS. The partial (UARS)
or complete (OSA) airway blockage appears to be due to airway
collapse under the negative pressure caused by normal inspiration.
Conventional therapy (CPAP, BiPAP) depends on raising the airway
pressure and is uncomfortable and poorly tolerated by most patients
so that fewer than half of OSA patients routinely use their CPAP
treatment. It has been discovered that a high nasal airflow (such
as about 20 liters per minute, for example) will prevent or reduce
the negative pressure of inspiration and hence reduce the incidence
of airway collapse. Because high nasal flows of warm humid air will
be tolerated by patients, the use of the system according to this
invention for therapy of patients with OSA/UARS is beneficial.
[0241] Another condition that has been discovered to be treatable
using the method and apparatus of this invention is xerostomia,
occurring in post-irradiated head and neck cancer patients. Many
people are diagnosed each year with head and neck cancer, and
radiotherapy is an important treatment in head and neck cancer
patients. However, some patients are kept awake at night because of
troublesome oral dryness, and xerostomia can cause difficulty with
mastication, deglutition, and articulation. It can also alter
taste, change pH, and is associated with dental decay, infection,
skin break down, and bone loss.
[0242] Current medical therapy for xerostomia includes frequent
sips of water, chewing gum, using artificial saliva, and taking
oral pilocarpine. Such therapies, however, have failed to provide
adequate relief even when used in combination. Also, xerostomic
patients find little benefit from standard bedside humidification
devices, and previous attempts at humidification via nasal cannula
have only worsened the problem by drying out the oronasal
passageways from the increased airflow.
[0243] It is believed that hydrating the respiratory tract with
warm, saturated (100% relative humidity) air at controlled variable
flow rates through a nasal cannula of up to about 40 liters of
water-saturated air per minute at dew points from room temperature
to about 43.degree. C. can provide a significant benefit. More
specifically, at about 41.degree. C., 57 milligrams of water per
liter of air can be delivered to the patient's respiratory tract,
which is five times the water vapor of normal room air.
[0244] Accordingly, it is believed that the introduction of heated
and humidified air while the patient is sleeping as well as during
periods of waking hours should reduce the severity of the symptoms
associated with xerostomia.
[0245] It is also recognized that premature infants in natal
intensive care units may require supplemental oxygen after they are
weaned from mechanical ventilation. For example, premature infants
may require supplemental oxygen and airflow for the following
conditions: respiratory distress syndrome secondary to lung
immaturity, transient tachypnea of the newborn, pneumonia, chronic
lung disease, and/or apnea and bradycardia of prematurity.
[0246] Premature infants being weaned from mechanical ventilation
are typically given nasal continuous positive airway pressure
(NCPAP) for some period to keep the airway open. Conventional
equipment is bulky and poorly tolerated, and there can be some risk
of injury to the infant's nose from the patient interface and from
the flow of inadequately humidified breathing gas. The
administration of high flow fully humidified breathing gas by nasal
cannula can provide sufficient respiratory support for such
premature infants with reduced risk of trauma.
[0247] Conventionally, room-temperature, dry oxygen is delivered to
premature infants. However, frequent adjustment of flow rate is
necessary to maintain consistent oxygenation, and the amount of
oxygen that can be delivered is limited by the drying effect of
high nasal flow. It has been discovered, therefore, that
conditioning of an air-oxygen mixture by warmth and humidity will
allow a higher flow rate which will result in more consistent
oxygenation. It has also been discovered that more oxygen can be
safely delivered by this method than with dry cold oxygen flow so
that infants with larger oxygen requirements can be supplied by
nasal cannula. This is especially true in view of the fact that
premature infants in natal intensive care units can sometimes
undergo episodes of hypoxia despite the constant monitoring and
adjustment of settings.
[0248] Stable oxygenation is especially important in the treatment
of premature infants having respiratory distress syndrome. Even
after a premature infant's syndrome has improved to the point that
mechanical ventilation is no longer needed, the infant frequently
will require supplemental oxygen and low continuous distending
pressure that is delivered via nasal continuous airway pressure
(CPAP). However, in the smallest infants, the diameter of the NCAP
prongs is larger than the diameter of the infant's nares. When
supplemental oxygen must be delivered by nasal prongs, it is dry
and cold, thereby increasing the risk of mucous plugs and reflex
bronchoconstriction, which would increase the work of
breathing.
[0249] It has been discovered that the ability to deliver warm and
humidified oxygen to infants makes it possible to deliver oxygen at
higher flow rates than with conventional systems with less risk of
airway damage. Accordingly, the method according to this invention
of delivering supplemental oxygen to infants is especially
beneficial in that it maintains a more constant level of
oxygenation than with conventional systems, and it provides mild
distending pressure with higher flow rates that will allow earlier
respiratory development of the smallest infants. Also, since
essentially all of the inspired air will come from the delivery
system, infants will breathe sterile filtered air with almost no
increased risk of infection. Also, heated and humidified air can be
delivered to the infant for up to or more than two hours at a
temperature set so that the air reaches the nose at a temperature
of about 33-35.degree. C.
[0250] For similar reasons the method according to this invention
is also beneficial for use with infants with Broncho Pulmonary
Dysplasia (BPD) for treatment in a step-down unit. Such infants
require continuous supplemental oxygen to maintain their
saturation. Conventional therapies use low-flow 100% oxygen, and it
has been discovered to be difficult to maintain saturation within
therapeutic limits. It has been discovered, however, that warmed,
humidified air-oxygen mixtures can be supplied according to this
invention at lower flows (such as about 5 liters per minute), in
order to provide a more consistent oxygen saturation with fewer
interventions.
[0251] The delivery of warm and humidified oxygen is also believed
to be beneficial for rewarming of small premature infants after
delivery and during stabilization. Small premature infants have
little fat stores and lose heat quite rapidly after delivery and
can become significantly hypothermic during the transition from
delivery room to the neonatal intensive care unit. Even though
these infants are stabilized on radiant warmers, the smallest of
infants can still become hypothermic during catheter placement
procedures. In addition to heat loss, premature infants also have
high water losses secondary to immaturity of the skin. These fluid
losses can be excessive during stabilization after birth. Infants
less than 750 grams may have 100-200 cc/kg/day of insensible free
water losses during the first several days of life even when placed
in a heated, double-walled isolette. Humidified air or oxygen has
been discovered to provide a means to give additional free water
and warmth through the respiratory tract.
[0252] It is also believed that the introduction of heated and
humidified air can enhance the effect of inhaled bronchodilators
for the delivery of medication aerosol at body temperature. For
example, during an acute asthma exacerbation, one may tend to
breathe harder, faster and through the mouth thus decreasing the
body's warming and humidifying apparatus. Also, with the
administration of nebulized treatments, patients are offered cold
or cool aerosolized medications, which may exacerbate or at least
work against the desired effects. It is believed that pre-warming
of the inhaled aerosol from a nebulizer should reduce or abolish
any cold-induced bronchospasm and allow the medications to reach
more lung airways.
Re-Warming of Patients After Surgery
[0253] It has been recognized that reduced core body temperature
during recovery from anesthesia can be associated with increased
risk of heart attacks and infection. Many conventional re-warming
methods rely on surface heating (e.g. circulating water mattresses,
forced-air warming blankets) and can be slow to raise core
temperature. Ideally, heat should be transferred directly into the
core thermal compartment, but access to the core is difficult short
of using extracorporeal bypass.
[0254] Hypothermia is known to occur in the majority of surgical
patients since virtually all anesthetics impair the body's ability
to regulate temperature. It has been estimated that 50-70% of
patients leave the operating room with core temperatures less than
36.degree. C., and 33% of patients have a core temperature that is
less than 35.degree. C. Hypothermia presents a greater risk of
myocardial ischemia and cardiac morbidity. Anesthetic drugs are
more slowly metabolized and hypothermia prolongs the length of stay
of a patient in the recovery room. Hypothermia has also been
associated with increased incidents of infections and patient
discomfort. For these reasons, it has been recognized that it is
advantageous to aggressively re-warm patients after surgery to
restore body temperature.
[0255] It is also recognized that significant heat and moisture is
lost through the respiratory tract from breathing cool dry gases,
and therefore dry mouth is a common complaint after surgery. This
is a result of anticholinergic medication that is routinely given
as part of the anesthetic regimen.
[0256] It has been surprisingly discovered that breathing warm air
(above body temperature) in accordance with this invention will
transfer heat to the body core and will accelerate the re-warming
process. Air delivered at 100% saturation, a controlled safe
temperature, and a flow rate sufficient to supply almost all or all
of the inspired air flow (so no room air is entrained and the heat
transfer to the patient is maximized) can reduce the hypothermic
condition of the patient.
[0257] The high humidity has been discovered to ensure that the
patient's airways are not damaged by drying and significantly
reduces the discomfort from post-operative dryness caused by drugs
given during surgery. It has further been discovered that the
evaporative heat loss associated with breathing cool dry gases can
be eliminated by providing 100% humidified air. Heated and
humidified air can be introduced at about 20 liters per minute flow
through a nasal cannula to accomplish patient re-warming.
EXAMPLE 3
[0258] Thirty patients were studied who were scheduled to undergo
intra-abdominal surgical procedures. Exclusion criteria were
preoperative fever (>38 C), history of hypo- or hyperthyroidism,
and significant cardiac disease by history.
[0259] Intraoperatively, patients received a balanced general
anesthetic consisting of thiopental, fentanyl and/or hydromorphone,
rocuronium or pancuronium, and isoflurane or desflurane. All
intravenous fluids were prewarmed to between 37 C and 38 C.
Intraoperatively, one layer of surgical drapes and one layer of
cotton blankets were used to cover the patients, but no active
warming measures (i.e. forced-air devices) were used.
[0260] Upon admission to the recovery room, patients were randomly
assigned to receive either (1) anhydrous room temperature oxygen
delivered at 4 Lmin.sup.-1 by mask (control, n=15), or (2) warmed,
humidified oxygen therapy at 20 Lmin..sup.-1 (test, n=15). One
layer of warmed cotton blankets was used to cover the patients but
no other warming methods were utilized.
[0261] In the test group the oxygen was warmed to 42 C measured at
the tip of the nasal cannula. The therapy duration was 90 minutes
followed by an additional 30 minutes of temperature monitoring,
during which the subjects breathed room temperature anhydrous
oxygen at 4 Lmin.sup.-1. core temperature was measured at the
tympanic membrane using a tympanic thermocouple probe MONA-THERM
(Mallinckrodt Medical, St. Louis, Mo.) and an ISO-THERMEX
electronic thermometer (Columbus Instruments, Columbus, Ohio).
[0262] Discomfort from mouth dryness was evaluated using a 0-4
point scale where 0="as dry as your mouth has ever been," and 4="no
dry mouth discomfort." Dry mouth scores were analyzed as a
dichotomous outcome, with a score less than or equal to 1 defined
as a dry mouth.
[0263] The system used during this evaluation allows high flow
oxygen delivery that is 100% humidified and warmed. The system
consists of a main unit and a delivery tube. In the main unit, air
is taken in by a compressor and pumped through a Pall
bacteriological filter into a cartridge where it passes through
tubes of membrane material surrounded by water at about 41 C. The
membrane pore size is about 0.01 micron, allowing molecular water
vapor to pass but retaining bacteria and other particulates. Liquid
water is retained by the hydrophobic (non-wettable) nature of the
membrane material. On leaving the cartridge the air is sterile and
100% saturated with water vapor. The airway in the delivery tube is
surrounded by a jacket that is heated to about 42 C by water pumped
from the main unit, to maintain the air temperature and prevent
condensation.
[0264] The two groups were similar for age, height, and body mass
index. The test group had a greater body mass. (Table 1). The
duration of surgery and core temperature upon admission were
similar between the two groups (Table 2).
TABLE-US-00002 TABLE 1 Patient Demographics Control Test P Value N
15 15 Age (yr) 48 .+-. 4 49 .+-. 4 0.92 Weight (kg) 69 .+-. 3 82
.+-. 7 0.05 Height (cm) 167 .+-. 2 158 .+-. 18 0.48 Body Mass Index
(kg m.sup.2) 24.7 .+-. 0.9 26.6 .+-. 1.6 0.29
TABLE-US-00003 TABLE 2 Preoperative Data Control Test P Value N 15
15 Duration of surgery (min) 180 .+-. 29 134 .+-. 15 0.19 Core
temperature Upon PACU 35.9 .+-. 0.2 35.7 .+-. 0.1 0.57 Admit
(.degree. C.) Core Rewarming Rate*(.degree. C. hr.sup.-1) 0.35 .+-.
0.06 0.67 .+-. 0.08 0.003 *during the first postoperative hour
[0265] FIGS. 45-47 illustrate the results of the evaluation. FIG.
45 shows core rewarming rate for patients receiving routine oxygen
therapy (Control) or warmed, humidified oxygen therapy (Test) in
the initial postoperative hour. Rewarming was accelerated in the
Test treatment group (*-P=0.003 vs. Control). FIG. 46 shows change
in core temperature from baseline, measured upon admission to the
postanesthesia care unit. Core temperature increased more rapidly
in the Test treatment group (*-P<0.05 vs. Control). FIG. 47
shows patients in the Test group had a lower incidence of dry mouth
in the postoperative period (*-P<0.05 vs. Control).
[0266] In the initial postoperative hour, core rewarming rates were
greater in the test group (0.67.+-.0.08.degree. C. hr.sup.-1) than
in the control group (0.35.+-.0.06.degree. C.hr.sup.-1) (P=0.003)
(FIG. 45). The change in core temperature from baseline was greater
in the test group than in the control group at 1 hour
(0.6.+-.0.1.degree. C. vs. 0.4.+-.0.1.degree. C.) (P<0.03) and
at 2 hours (1.0.+-.0.1.degree. C. vs. 0.6.+-.0.1.degree. C.)
(P<0.04) (FIG. 46).
[0267] The incidence of dry mouth was similar upon PACU admission,
then lower in the test group during the treatment period
(P<0.05) (FIG. 47). After 90 min, when the treatment was
discontinued, the incidence of dry mouth was similar between
groups.
[0268] As illustrated in Example 3 above, the delivery of warmed,
humidified oxygen has been discovered to accelerate the rate of
core rewarming by approximately two-fold in mildly hypothermic
postoperative patients. This effect is believed to be partially
related to direct heat transfer though the respiratory tract into
the pulmonary vasculature. In addition, the elimination of
evaporative heat loss is believed to contribute to the accelerated
rate of rewarming.
[0269] It has been discovered that significant heat can be lost
through the respiratory tract from breathing cool dry gases, and
evaporative heat loss can be significantly reduced by providing
100% humidification. Active warming and humidification of the
inspired mixture can prevent heat loss and reduce the magnitude of
hypothermia in small children undergoing general anesthesia and
surgery. In adult patients, however, intraoperative warming and
humidification appears to have little or no effect on core
temperature. This age-related difference in effect is probably
explained by a relatively greater proportion of total heat loss
through the respiratory tract in children compared to adults.
[0270] Postoperatively, the percent of total body heat loss through
the respiratory tract is likely to be greater than during the
intraoperative period. Compared to the intraoperative period, there
should be less cutaneous heat loss via radiation since
anesthetic-induced vasodilatation is significantly less, and there
is less exposure of the body surface and body cavities to the
atmosphere. These intra- and postoperative differences may explain
the greater effect of warmed humidified breathing gases according
to this invention on body temperature in the postoperative
period.
[0271] An estimation of heat transfer can be calculated to compare
rewarming rates between the test and control groups if several
assumptions are made, i.e., that total body heat production and
heat losses are similar in the two groups, and that the respiratory
duty cycle and mean inspiratory flow rate are about 1:1 and 20
Lmin.sup.-1, respectively. Given the specific heat of the human
body (0.83 calkg.sup.-1.degree. C..sup.-1); 57 mg water vapor per
liter; 540 cal per gram of water for heat of condensation; and
using the average body mass of the subjects of the evaluation in
Example 3, the estimated effect of treatment on rewarming rate is
about 0.33.degree. C. per hour. Accordingly, the average patient
receiving treatment is believed to rewarm 0.33.degree. C. more
rapidly each hour relative to a patient breathing conventional
oxygen therapy.
[0272] There was a difference in body mass between the test and
control groups in Example 3, and the greater body mass in the test
group may have influenced rewarming. The effect of a greater body
mass, however, would be a decreased rewarming rate, since the
amount of heat transfer per unit of body mass would be decreased.
Therefore the average patient receiving treatment would be likely
to rewarm more than about 0.33.degree. C./hr faster as compared to
conventional therapy.
[0273] As discussed above, dry mouth is a common complaint after
surgery which often results from anticholinergic medications (i.e.
glycopyrrolate or atropine) that are routinely given as part of the
anesthetic regimen. Example 3 demonstrated that humidified warmed
breathing gases according to this invention alleviate this
discomfort. This effect is likely to increase patient satisfaction
following surgery.
[0274] In summary, the delivery of warmed, humidified oxygen as
described in Example 3 has been discovered to accelerate core
rewarming rate by approximately two-fold in mildly hypothermic
patients. In addition, there is less discomfort from dry mouth in
patients receiving this therapy.
[0275] Although the foregoing discussion generally relates to post
operative patients, it is recognized that the system and method
according to this invention can be utilized for any hypothermic
subject. In other words, the system and method of this invention
can be applied to raise the body temperature whenever needed and
for whatever reason.
Improvement of Peak Performance of Athletes
[0276] It has been surprisingly discovered that high flow,
humidified, heated room air can improve the pulmonary function and
peak exercise performance in human athletes. Moreover, many
professional and amateur athletic teams compete under dry-air
conditions (e.g. fall-to-winter sports, such as football, and
winter sports, such hockey, basketball, skiing, and skating). It
has been discovered that athletes performing in such conditions can
benefit from pre-exercise treatment by the introduction of heated
and humidified air. Also, it has been discovered that such
treatment can limit pulmonary stress and help to prevent
exercise-induced bronchospasm and bronchitis in a manner that is
not prohibited by regulations such as the regulations of the
International Olympic Committee. Such treatment can also provide
improved therapy for exercise-induced asthma.
EXAMPLE 4
[0277] The effects of pre-exercise breathing with high-flow,
humidified air were evaluated on treadmill-running time to
exhaustion in simulated sprinting and 10-kilometer endurance
running conditions in trained, well-conditioned athletes.
University at Buffalo Track Team members exercised to exhaustion in
two protocols: (1) short intense exercise to simulate sprinting
uphill on a treadmill 10% incline at 95% VO.sub.2max (n=15 runners,
mean VO.sub.2max=56.61 ml/kg/min); and (2) running with no incline
on the treadmill, at each runner's 10-kilomoeter racing speed (n=6
runners, mean VO.sub.2max=54.91 ml/kg/min.).
[0278] Runners were randomly assigned to either run with
pre-exercise breathing (37.degree. C.) or the control, without
pre-exercise breathing for one hour prior to exercise. Heart rate
(HR), respiratory rate (RR), minute ventilation (V.sub.E), oxygen
consumption (VO.sub.2), end-tidal carbon dioxide
(P.sub.ETCO.sub.2), and arterial oxygen saturation (S.sub.aP.sub.2)
were measured continuously. Subjective comments after each exercise
also were recorded.
[0279] The hyperthermic humidification system used in Example 4
provides warmed, soothing inhalation therapy. The system delivers a
100% humidified air stream directly to the patient via a high flow
nasal cannula at flow rates between 5-20 liters/min, safely heated
to just above body temperature (range, 34.degree. C.-41.degree.
C.). A replaceable microporous membrane cartridge accomplishes air
stream humidification into the vapor phase. Bacteria, molds, and
other pathogens cannot pass into the air circuit. The output of the
system contains molecular phase water with water particles 0.5
micron or less in size. This allows the inhaled water vapor to
reach the alveoli due to the small size of the water particles
having purely diffusive characteristics. The system does not tend
to produce aerosolized or nebulized particles of water, which may
precipitate in the upper airway of the nasopharynx
[0280] Humidifying the air stream to a dew point at temperatures
above 37.degree. C. provides many times the water vapor normally
available to the patient. At 41.degree. C., the system according to
this invention can deliver 57 mg of water per liter of airflow.
This is approximately five times the water vapor inhaled in a
typical hospital room at 21.1.degree. C. (70.degree. F.) room
temperature having only 30-40% relative humidity. During operation
of the system, the delivery tube can remain completely dry, thereby
eliminating condensation in the breathing line. Heating the
delivery tube with circulating liquid allows the device to carry
100% oxygen as safely as air.
[0281] In this Example, twenty university student athletes, male
and female, on the track team at the University at Buffalo were
selected. The following conditions were exclusionary: smoking,
exercise induced asthma, any cardio-pulmonary disease, taking any
medications, or having any upper respiratory illness.
[0282] Maximum oxygen consumption (VO.sub.2max) was pre-determined
for each experimental subject. Athletes were monitored by
electrocardiogram (ECG), a cardio-tachometer for instantaneous
heart rate, beat-to-beat measurement of transcutaneous arterial
oxygen saturation (SaO.sub.2), and breath measurement of
respiratory rate, minute ventilation, oxygen consumption and
end-tidal carbon dioxide.
[0283] Maximal exercise performance was defined as the duration of
exercise to exhaustion under both simulated, short duration (5-15
min) high-intensity sprinting and moderate duration (30-40 min)
endurance conditions. In the first study, the athletes exercised
twice on a treadmill at 10% incline, at 95% of their individually
pre-determined VO.sub.2max until they could not continue. Prior to
exercise, athletes were randomly assigned to either pre-exercise
breathe at body-temperature (37.degree. C.) inspired temperature
for 60 minutes at 30 lpm or to simply pre-exercise breathe room-air
as the control condition prior to exercise on a separate testing
day. During exercise testing, athletes breathed room air.
[0284] The second study simulated longer-duration running
conditions. The athlete ran with the treadmill level (0% incline)
at their individually pre-determined racing speed for a
10-kilometer race until they could not continue. These subjects
were randomly assigned to either pre-exercise breathe at 37.degree.
C. inspired temperature exercise at 31 lpm for 60 minutes prior to
exercise or pre-exercise breathe room-air.
The results of uphill sprinting and endurance running are
summarized in the tables provided below.
TABLE-US-00004 TABLE ONE Uphill Sprinting C With Treatment (@ A B
same time as With Without termination Treatment (@ Treatment (@
without Termination) Termination) Treatment) P value Time to 14.7
(9.25) 11.5 (5.36) -- A vs. B < 0.001 termination (min) (+24.2%)
VO.sub.2 53.3 (2.59) 55.8 (2.42) -- A vs. B < 0.051 (ml/kg/min)
(-4.4%) SaO.sub.2(%) 90.0 (1.33) 89.8 (1.23) 90.4 (1.64) NS
PetCO.sub.2 31.0 (0.89) 32.2 (0.99) 32.9 (0.90) A vs. B < 0.028
(mmHg) (-3.1%); A vs. C < 0.001 (-5.7%) RR (min.sup.-1) 61.4
(2.69) 59.4 (2.70) 56.8 (2.33) B vs. C < 0.038 (-4.4%); A vs. C
< 0.001 (+8.2%) V.sub.E (1/min) 120.8 (8.36) 120.8 (7.08) 116.0
(7.89) A vs. C < 0.008 (-3.9%); B vs. C < 0.008 (+4.1%) HR
(min.sup.-1) 191.7 (1.94) 188.2 (2.09) 189.7 (2.15) NS
VO.sub.2/VO.sub.2 max 93.8 (2.08) 98.3 (1.70) -- A vs. B < 0.048
(%) (-4.5%) Time to 109.9 (20.27) 79.5 (11.3) -- NS recovery to 97%
SaO.sub.2(sec) VO.sub.2 = peak oxygen consumption at steady state;
SaO.sub.2 = estimated arterial O.sub.2 saturation; P.sub.ETCO.sub.2
= end-tidal CO.sub.2; RR = respiratory rate; V.sub.E = minute
ventilation; HR = heart rate. (mean .+-. SE)
TABLE-US-00005 TABLE TWO Endurance Run C With Treatment (@ A B same
time as With Without termination Treatment (@ Treatment)@ without
Termination) Termination) Treatment) P value Time to 20.5 (3.22)
16.6 (2.52) -- A vs. termination B < 0.006 + 23.4%) (min)
VO.sub.2 50.5 (3.39) 49.1 (2.98) -- NS (ml/kg/min) SaO.sub.2(%)
92.5 (0.56) 93.7 (0.49) 92.8 (0.88) NS PETCO.sub.2 28.6 (1.69) 29.7
(1.97) 31.0 (1.75) A vs. C < 0.024 (mmHg) (-7.9%) RR
(min.sup.-1) 74.3 (5.08) 66.5 (4.36) 65.9 (6.34) NS V.sub.E (1/min)
108.1 (12.95) 102.6 (12.89) 98.4 (9.22) NS HR (min.sup.-1) 187.1
(7.85) 184.7 (7.27) 187.7 (5.43) NS VO.sub.2/VO.sub.2 max (%) 92.5
(3.50) 90.9 (2.85) -- NS Time to 140.0 (39.95) 63.3 (14.31) -- A
vs. B < recovery to 0.031 (+121.1%) 97% SaO.sub.2 (sec) VO.sub.2
= peak oxygen consumption at steady state; SaO.sub.2 = estimated
arterial O.sub.2 saturation; PETCO.sub.2 = end-tidal CO.sub.2; RR =
respiratory rate; V.sub.E = minute ventilation; Hr = heart rate.
(mean .+-. SE)
[0285] Twenty university student athletes were recruited to
participate in this study. Fifteen completed this study. The mean
age of the 15 experimental subjects, eight females and seven males,
in the uphill sprinting study was 18.9.+-.0.06 (SD) yrs. There was
a mixture of 8 sprinters and 7 mid-distance runners. For the uphill
sprinting study, the mean VO.sub.2max for all 15 runners was 56.61
ml/kg/min.+-.2.09 (SE). In the 10-Kilometer endurance running
study, the mean VO.sub.2max was 54.9 ml/kg/min.+-.4.4 (SE).
[0286] In the sprinting uphill study, the endurance running time
for all 15 runners without treatment was 11.54.+-.5.36 min (SD)
compared to pre-exercise breathing with treatment, 14.70.+-.9.25
(SD), an improvement of +24.23% (p<0.001). In the second study,
simulating 10-kilometer running conditions, the endurance running
time for all six runners without treatment was 16.60.+-.2.52 min
(SD) and with treatment was 20.54.+-.3.22 min (SD), an improvement
of +23.35% (p=0.006).
[0287] In the uphill sprinting study, the steady state oxygen
consumption was 55.76 ml/kg/min.+-.2.42 (SE) without treatment and
53.31 ml/kg/min.+-.2.59 (SE) compared to using treatment, a
difference of -4.39% (p=0.051). When these values are normalized by
percentage to the individual's maximum oxygen consumption
(VO.sub.2max), uphill running without treatment had a steady state
VO.sub.2 of 98.25%.+-.1.70 (SE) compared to 93.79%.+-.2.08 (SE)
with treatment, a reduction of -4.54% (p=0.048).
[0288] Following the 10-Kilometer endurance runs, there was an
increase (+121.6%, p=0.031) in the recovery time for SaO.sub.2 to
return to 97% using treatment (140.00 sec.+-.39.95 (SE)) compared
to not using treatment (63.33 sec.+-.14.31 (SE)). A Wilcoxon Signed
Rank Test was used to determine this significance.
[0289] In the uphill running study, there was a reduction of -3.11%
(p=0.028) in P.sub.ETCO.sub.2 at the termination of the longer runs
with treatment (31.04 mmHg.+-.0.89 (SE)) compared to the shorter
runs without treatment (32.16 mmHg.+-.0.99 (SE)). With treatment
there was also a reduction of -5.99% (p<0.001) in
P.sub.ETCO.sub.2 at the equivalent running time from not using the
treatment (32.90 mmHg.+-.0.90 (SE)) to the termination of these
runs with treatment (31.04 mmHg.+-.00.89 (SE)).
[0290] In the 10 kilometer endurance study, with treatment there
was a reduction (-7.86%, p=0.024) in P.sub.ETCO.sub.2 at the
equivalent running time from not using the treatment (31.03
mmHg.+-.1.75 (SE)) to the termination of these same runs with
treatment (28.59 mmHg.+-.1.69 (SE)).
[0291] In the uphill running study, there was a decrease (-4.39%,
p=0.038) in respiratory rate (RR) from the termination of the
shorter runs without treatment (59.41 breaths/min.+-.2.70 (SE)) to
the same equivalent running time with treatment (56.80
breaths/min.+-.2.33 (SE)). With treatment, there was an increase
(+8.17%, p<0.001) in RR at the equivalent running time from not
using the treatment (36.80 breaths/min.+-.2.33 (SE)) to the
termination of these same runs with treatment (61.44
breaths/min.+-.2.69 (SE)).
[0292] In the 10-kilometer endurance study, there was an increase
(+11.79%, p=0.03) in RR at the termination of runs without
treatment (66.49 breaths/min.+-.4.36 (SE)) compared to runs with
treatment (74.33 breaths/min.+-.5.08 (SE)).
[0293] In the uphill running study, there was a decrease (-3.94%,
p=0.008) between maximum minute ventilation (V.sub.E) from the
shorter runs without treatment (120.80 l/min (BTPS).+-.7.08 (SE))
compared to the same equivalent running time with treatment (116.04
l/min (BTPS).+-.7.89 (SE)). With treatment, there was an increase
(+4.080%, p=0.008) in V.sub.E at the equivalent running time from
not using the treatment (116.04 l/min (BTPS).+-.7.89 (SE)) to the
termination of these same runs with treatment (120.77 l/min
(BT).+-.8.36 (SE)).
[0294] Accordingly, pre-exercise breathing with treatment caused an
improvement in both uphill sprinting running time (+24.23%) and
simulated 10-kilometer endurance running time (+23.35). The use of
treatment was also accompanied by a reduction in steady state
VO.sub.2 (-4.54%), RR (-4.39%) and V.sub.E (-3.94%) at the
termination of the runs.
[0295] It is believed that pre-exercise treatment breathing may
prevent airway drying during exercise. Intense exercise can result
in the development of high hydrostatic pressure in the pulmonary
capillaries, subsequent interstitial pulmonary edema, limiting gas
exchange and resulting in hypoxemia. Pre-exercise breathing with
treatment is believed to improve gas exchange during intense
exercise by limiting hydrostatic damage to the pulmonary
vasculature. Also, it is believed that treatment may increase
running time by decreasing energy expenditures as suggested by a
reduction in VO.sub.2 (-4.54%). The decrease in V.sub.E after
treatment suggests that the work of breathing may be reduced
compared to without treatment. The decrease in RR and V.sub.E may
reflect a decrease in the work of breathing caused by
treatment.
[0296] It is recognized that the maximum airflow rate during
inspiration at rest is often about 30 to 35 liters per minute.
Preferably, heated and humidified breathing gas is introduced
according to this invention at a flow rate that is high enough to
ensure that almost all of a subject's inspired gas comes from the
nasal cannula so that they entrain a minimum amount of room air,
thereby avoiding dilution of the warm humid air with cool dry room
air. Under some circumstances, flows above about 40 liters per
minute can become uncomfortable and can start to make exhalation
more difficult. The most preferred range of flow rates is therefore
about 30 to about 35 liters per minute for pre-exercise
therapy.
[0297] Also, a temperature of introduced breathing gas of about
37.degree. C. is preferred. A higher temperature would deliver more
moisture but has also been discovered to raise body temperature. A
temperature lower than 37.degree. C. would deliver less
moisture.
[0298] Although a shorter or longer duration can be selected, a
duration of about one hour prior to exercise is preferred as an
upper limit although longer durations also appear to be
therapeutically beneficial.
[0299] Although the foregoing Example relates to pre-exercise
treatment, it has also been discovered that the delivery of high
flow oxygen at high humidity can improve performance during
exercise. Specifically, the delivery of heated and humidified
breathing gas to a subject can help reduce their work of breathing
and enhance exercise performance through the same mechanism as for
pre-exercise treatment. One example of treatment during exercise
might apply to pulmonary rehabilitation programs (e.g., after lung
surgery), which programs are based on improving lung function by
exposing the patient to exercise so that they exercise the
respiratory system. By enhancing exercise performance in such
patients according to this invention, they can do more work and
accelerate the rehabilitation process.
[0300] It has been discovered that another beneficial application
of the system and method of this invention is the introduction of
high flow oxygen to patients requiring supplemental oxygen. For
example, patients with severe lung disease often require
supplemental oxygen, but conventional systems often have a maximum
gas flow of about 6 liters per minute by nasal cannula. Higher flow
rates using conventional systems have been discovered to cause
drying and cooling in the upper airway. The drying and cooling can
cause discomfort and airway damage. If higher oxygen flows are
needed, it is often necessary to use a breathing mask, which causes
difficulty for the patient with respect to speaking and feeding.
Some patients are also claustrophobic and can be subject to panic
attacks while wearing a mask.
[0301] Using the system and method according to this invention, it
has been discovered that airflow rates up to about 40 liters per
minute (or even higher) by nasal cannula are well tolerated when
the humidity is greater than about 90% and the temperature is at or
above 37.degree. C.
[0302] In another application of the system according to this
invention, it has been discovered that the introduction of heated
and humidified breathing gas is beneficial for voice treatment. Dry
air inhalation can impair voice production and, for professionals
who depend on the use of their voice, this can reduce their ability
to work. The system and method of this invention provide an
improved manner in which heated and humidified breathing gas can be
introduced to the upper respiratory tract for voice treatment.
Also, the system and method according to this invention can be
comfortably administered while the subject is asleep.
[0303] It has further been discovered that atrophic rhinitis is
beneficially treated using the system and method according to this
invention. Maintenance of high humidity in the nasal passages is
believed to significantly promote healing of the lesions in
atrophic rhinitis with improvements in quality of life.
[0304] The supply unit according to this invention has also been
discovered to have application in connection with ventilator
weaning using a trans-tracheal cannula. Cannulas for delivering
breathing gas to the trachea of a patient are available under the
trademark SCOOP from Trans-Tracheal Inc. of Denver, Colo. Although
it is believed to be beneficial to provide breathing gas at flows 6
to 10 liters per minute, it has been discovered that some patients
benefit from higher flows of 15-20 liters per minute. Such higher
flows can be humidified according to the system and method of this
invention, thereby removing the risk of drying of the tracheal
airway. Flow rates of up to 15 liters/min, humidified according to
this invention, have been found effective in maintaining normal
blood oxygen levels in patients with severe obstructive lung
disease. Most preferably, flow rates of about 10 to about 15 liters
per minute are provided for oxygen saturation levels of about 90%
to about 98%.
[0305] It is also noted that nasal mucociliary clearance (mcc)
helps to move matter, including bacteria, away from the nasal
epithelia. If secretions are not moved, then they can dry and
become infected. The system and method of this invention can be
used to supply moisture and mobilize such secretions. More
specifically, the system and method of this invention makes it
possible to introduce heated and humidified breathing gas through a
nasal cannula over a prolonged period of time (e.g.,
overnight).
[0306] Although the apparatus and methods according to this
invention have been described with reference to particular
embodiments selected for illustration, and with reference to
particular examples, it will be appreciated that variations and
modifications to the described embodiments and examples can be made
without departing from the spirit and scope of this invention. The
scope is separately defined in the appended claims.
* * * * *