U.S. patent application number 17/652734 was filed with the patent office on 2022-08-11 for humidification of respiratory gases.
The applicant listed for this patent is Fisher & Paykel Healthcare Limited. Invention is credited to Michael John Andresen, Dexter Chi Lun Cheung, Stephen David Evans, Laith Adeeb Hermez, Anthony James Newland, Hamish Adrian Osborne.
Application Number | 20220249788 17/652734 |
Document ID | / |
Family ID | 1000006290887 |
Filed Date | 2022-08-11 |
United States Patent
Application |
20220249788 |
Kind Code |
A1 |
Hermez; Laith Adeeb ; et
al. |
August 11, 2022 |
HUMIDIFICATION OF RESPIRATORY GASES
Abstract
A system for humidifying respiratory gases has a humidification
apparatus, a humidification chamber, a heating apparatus and a
sensor. The sensor is configured to determine a characteristic of
the gases flow and communicate this to a controller which controls
the power supplied to the heating apparatus with respect to
information regarding the characteristic of the gases flow. A
structure partially encloses the humidification chamber and allows
energy loss through a wall of the humidification chamber. The
humidification chamber may have features to promote heat loss
through the wall of the chamber.
Inventors: |
Hermez; Laith Adeeb;
(Auckland, NZ) ; Evans; Stephen David; (Auckland,
NZ) ; Osborne; Hamish Adrian; (Auckalnd, NZ) ;
Andresen; Michael John; (Auckland, NZ) ; Newland;
Anthony James; (Auckland, NZ) ; Cheung; Dexter Chi
Lun; (Auckland, NZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fisher & Paykel Healthcare Limited |
Auckland |
|
NZ |
|
|
Family ID: |
1000006290887 |
Appl. No.: |
17/652734 |
Filed: |
February 28, 2022 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15525257 |
May 8, 2017 |
11278689 |
|
|
PCT/NZ2015/050193 |
Nov 17, 2015 |
|
|
|
17652734 |
|
|
|
|
62080814 |
Nov 17, 2014 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 2016/003 20130101;
A61M 2205/3334 20130101; A61M 16/161 20140204; A61M 16/109
20140204; A61M 16/0003 20140204; A61M 16/16 20130101; A61M
2016/0033 20130101; A61M 2205/3606 20130101; A61M 2205/3368
20130101; A61M 2205/02 20130101; A61M 16/024 20170801; A61M
2205/0244 20130101; A61M 2205/502 20130101; A61M 2205/362
20130101 |
International
Class: |
A61M 16/00 20060101
A61M016/00; A61M 16/10 20060101 A61M016/10; A61M 16/16 20060101
A61M016/16 |
Claims
1. (canceled)
2. A chamber configured for use within a humidification system,
comprising: a wall; an inlet; and an outlet; wherein the chamber is
configured to hold a volume of liquid, and the chamber is
configured to allow gases to pass over the volume of liquid from
the inlet of the chamber to the outlet of the chamber, and the wall
of the chamber is configured to facilitate heat loss from the
chamber.
3. The chamber of claim 2, wherein the outlet is configured to
receive a sensor.
4. The chamber of claim 3, wherein the sensor is configured to
measure a temperature of a gases flow.
5. The chamber of claim 2, wherein the chamber comprises a
substantially large surface area to facilitate energy loss from the
chamber.
6. The chamber of claim 5, wherein the chamber comprises a passive
cooling mechanism.
7. The chamber of claim 6, wherein the passive cooling mechanism
comprises a fin.
8. The chamber of claim 2, wherein the wall of the chamber bulges
between a base and an upper surface of the chamber.
9. The chamber of claim 2, wherein the wall of the chamber is
shaped to increase surface area between a gases flow and the volume
of liquid in the chamber.
10. The chamber of claim 2, wherein the wall of the chamber
comprises a region of thermally conductive material.
11. A system for humidifying respiratory gases comprising: a
humidification apparatus comprising a heating apparatus and a
controller; and the chamber of claim 2, wherein chamber is
configured to be coupled with the humidification apparatus, wherein
the controller is configured to determine an amount of power to be
provided to the heating apparatus to alter a gases flow such that a
characteristic of the gases flow approaches a predetermined value
at the outlet of the chamber.
12. The system of claim 11, wherein the chamber is configured to be
received within a recess of the humidification apparatus.
13. The system of claim 11, wherein the chamber is configured to be
at least partially enclosed by a structure that is permanently
coupled with the humidification apparatus.
14. The system of claim 11, wherein the chamber is configured to be
at least partially enclosed by a structure that is integral with
the humidification apparatus.
15. The system of claim 11, wherein the chamber is configured to be
at least partially enclosed by a structure that is removably
coupled with the humidification apparatus.
16. The system of claim 11, wherein the heating apparatus directly
heats the volume of liquid, and indirectly heats a gases flow as
the gases flow passes over the volume of liquid.
17. A chamber configured for use within a humidification system,
comprising: an inlet configured to receive respiratory gases from a
ventilator; a wall; an outlet configured to output the respiratory
gases to a patient interface; a base connected to the wall; and a
cooling structure coupled to the wall or the base, configured to
reduce temperature of the respiratory gases.
18. The chamber of claim 17, wherein the outlet is configured to
receive a sensor.
19. The chamber of claim 18, wherein the sensor is configured to
measure a temperature of the respiratory gases.
20. The chamber of claim 17, wherein the wall of the chamber bulges
between the base and an upper surface of the chamber.
Description
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 15/525,257, filed May 8, 2017, which is a
national stage application based on International Application No.
PCT/NZ2015/050193, filed Nov. 17, 2015, which claims the priority
benefit of U.S. Provisional Application No. 62/080,814, filed Nov.
17, 2014, the entirety of which is hereby incorporated by reference
herein. Any and all applications for which a foreign or domestic
priority claim is identified in the Application Data Sheet as filed
with the present application are hereby incorporated by reference
under 37 C.F.R. .sctn. 1.57.
FIELD OF THE DISCLOSURE
[0002] The present disclosure generally relates to humidifying
respiratory gases. More particularly, the present disclosure
relates to a humidification apparatus that promotes heat loss from
the humidification chamber.
BACKGROUND
[0003] A humidification apparatus is used to provide heated and
humidified respiratory gases to a patient via a patient interface.
Respiratory gases delivered to a patient at 100% relative humidity
and 37.degree. C. mimic the transformation of air that occurs as
the respiratory gases pass through the upper airway to the lungs.
This may promote efficient gas exchange and ventilation in the
lungs, aid defense mechanisms in the airway and increase patient
comfort during treatment.
[0004] Respiratory gases entering a humidification apparatus are
heated and humidified by passing over the surface of the liquid
within the humidification chamber. Thus, they are substantially
saturated with vapour when they flow out of the humidification
chamber through the outlet port. A controller determines the amount
of power to supply to the heater so that the respiratory gases
comprise a predetermined characteristic such as temperature,
humidity or flow at the outlet port. The characteristic can be
measured by one or more sensors at the outlet port. Therefore, the
humidification apparatus heats and humidifies the respiratory gases
so that they are substantially saturated and comprise a
predetermined characteristic as they exit the humidification
apparatus.
BRIEF SUMMARY
[0005] A respiratory assistance system is disclosed that comprises
mechanisms to increase heat loss from a humidification chamber to a
surrounding ambient environment.
[0006] An embodiment discloses a structure that couples to a
humidification apparatus and at least partially encloses the
humidification chamber. The structure comprises integrated sensors
that protrude from the structure and extend at least partially into
the humidification chamber. The structure comprises alignment and
orientation features to better facilitate coupling with the
humidification chamber.
[0007] In some embodiments, the structure includes alignment
features, such as a shroud and a hood. The shroud facilitates
coupling with an inspiratory tube connector. The hood aligns with a
corresponding nose of the humidification chamber. The hood further
comprises rails that aid in alignment of the humidification
chamber. The hood comprises an opening that allows heat loss from
the humidification chamber to the surrounding ambient environment.
The sensors are positioned both within the shroud, and on a post,
which provides a platform to allow sensing within the
humidification chamber.
[0008] In some embodiments optional to any embodiment disclosed
herein, the structure includes an active cooling mechanism that
acts to blow air on or around the humidification chamber. An
example of an active cooling mechanism is a fan.
[0009] The humidification chamber includes apertures that can
receive the sensors. In some embodiments optional to any embodiment
herein, the humidification chamber includes a passive cooling
mechanism. The passive cooling mechanism is in the form of a heat
sink, for example, fins. The fins protrude from the humidification
chamber and extend in an upward direction. The fins encourage
additional heat loss from the humidification chamber.
[0010] In some embodiments optional to any embodiment disclosed
herein, the humidification chamber includes a wall that bulges
outwardly from between the base and an upper surface of the
humidification chamber. This increases the surface area of the
liquid within the humidification chamber, which increases the
amount of humidity that is transferred to the respiratory gases. In
some embodiments optional to any embodiment disclosed herein, a
humidification chamber may be used that includes altered geometries
such that the surface area of the liquid is optimised.
[0011] In some embodiments optional to any embodiment disclosed
herein, regions of the humidification chamber include a thermally
conductive material. This facilitates heat loss from the
humidification chamber without altering the overall geometry or
size of the humidification chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] These and other features, aspects, and advantages of the
present disclosure will be described with respect to the following
figures, which are intended to illustrate and not to limit the
disclosed embodiments.
[0013] FIG. 1 is a schematic of a respiratory assistance system
[0014] FIGS. 2-3 are perspective views of a humidification
apparatus according to an embodiment of the present disclosure.
[0015] FIG. 4 is a perspective view of a humidification chamber
according to an embodiment of the present disclosure.
[0016] FIG. 5A is a front perspective view of a structure according
to an embodiment of the present disclosure.
[0017] FIG. 5B is an isometric view of a structure according to the
embodiment of FIG. 5A.
[0018] FIG. 6 is a perspective view of a structure according an
embodiment of the present disclosure.
[0019] FIGS. 7-9 are perspective views of different embodiments of
a humidification chamber.
[0020] FIG. 10 illustrates an embodiment of a humidification
chamber with a cooling structure.
[0021] FIG. 11 illustrates embodiments of cooling structures having
different design parameters.
[0022] FIG. 12 illustrates the design parameters of the cooling
structures shown in FIG. 10.
[0023] FIG. 13 shows contact angle measurements for two different
materials that can be used to make the cooling structures.
[0024] FIG. 14 illustrates capillary height measurements for the
cooling structures of FIG. 10.
[0025] FIG. 15 shows example results corresponding to the change in
relative humidity from adding cooling structures to the
humidification chamber.
[0026] FIG. 16 illustrates an embodiment of a base structure that
can be used with the humidification chamber.
[0027] FIG. 17 illustrates a top view of the base structure of FIG.
16.
DETAILED DESCRIPTION
[0028] FIG. 1 discloses a respiratory assistance system 100 that
includes a gases source 110. The gases source 110 utilises a gases
supply tube 120 to supply respiratory gases to a humidification
apparatus 130. In some embodiments, the gases source 110 and the
humidification apparatus 130 are within the same housing. In some
embodiments, the gases source 110 and the humidification apparatus
130 are in different housings. The humidification apparatus 130
includes a base unit 135 and a humidification chamber 140. The
humidification chamber 140 can be mounted on the base unit 135. The
humidification chamber 140 can hold a volume of liquid, for
example, water. The humidification chamber 140 further includes an
inlet port 142 and an outlet port 144. Respiratory gases are
humidified as they pass through the humidification chamber 140 via
the outlet port 144 and into an inspiratory tube 150 where they are
transported to a patient interface 160. In some embodiments, an
expiratory tube 170 transports exhaled gases away from a
patient.
[0029] Respiratory gases entering the humidification chamber 140
are heated and humidified by passing over the surface of the
liquid. Thus, they are substantially saturated with vapour when
they exit the humidification chamber 140 through the outlet port
144. The base unit 135 includes a heater plate 240. A controller
132 of the humidification apparatus 130 determines the amount of
power to supply to the heater plate 240 to heat the humidification
chamber 140 when the humidification chamber 140 is mounted on the
base unit 135 so that the respiratory gases include a predetermined
characteristic at the outlet port 144 as measured by a sensor (not
shown in FIG. 1) at or near the outlet port 144. Therefore, the
humidification apparatus 130 acts to heat and humidify the
respiratory gases so that they are substantially saturated and
include a predetermined characteristic. In some embodiments, a
controller 128 of the gases source 110 may communicate with the
controller 132 as part of the operations of the controller 132
herein described. In some embodiments, the controller 128 may
execute part or all of the operations of the controller 132 herein
described.
[0030] In some embodiments, the predetermined characteristic is a
gases temperature. In some embodiments, the predetermined
characteristic may be a relative humidity, an absolute humidity, or
a flow rate of gases. The temperature of the respiratory gases at
the inlet port 142 is typically less than a temperature of the
respiratory gases at the outlet port 144. Thus, a temperature
differential exists between the inlet port 142 and the outlet port
144. This, in effect, is a temperature differential that exists
between the incoming gases and the outgoing gases, respectively.
The controller 132 determines how much power to supply to the
heater plate 240 to bring the temperature of the respiratory gases
to a value similar to the predetermined temperature at the outlet
port 144. As the heater plate 240 heats the respiratory gases to
the predetermined temperature, the respiratory gases can be
humidified during the process of heating.
[0031] In some cases, the temperature of the respiratory gases at
or near the outlet port 144 may already be at or close to the
predetermined temperature. This may be due to a high ambient
temperature, gases supplied from the gases source 110 to the
humidification apparatus 130 at a higher temperature, heating
effects from within the humidification apparatus 130, or heating
effects from within the gases source 110. As a result, the
controller 132 determines that less heating is necessary to heat
the respiratory gases to the predetermined temperature and supplies
less power to the heater plate 240. Thus, although the respiratory
gases leaving the humidification chamber 140 are substantially
similar to the predetermined temperature, less humidity is added to
the respiratory gases.
[0032] The humidification apparatus 130 includes mechanisms to
facilitate heat loss from the humidification chamber 140 to allow a
greater temperature differential between the inlet port 142 and the
outlet port 144. A greater temperature differential causes more
power to be supplied to the heater plate 240 to heat the
respiratory gases. This allows more humidity to be added to the
respiratory gases. In some embodiments, a structure 220 includes
mechanisms to promote heat loss. In some embodiments, the
humidification chamber 140 includes mechanisms to improve heat
loss. The mechanism may correspond to a shape, design, or an
insert.
[0033] FIGS. 2-3 illustrate an embodiment of the humidification
apparatus 130 that includes the base unit 135, a display 210, the
structure 220, the humidification chamber 140, and the heater plate
240. The structure 220 includes sensors 230. In some embodiments,
the sensors 230 are permanently mounted onto the structure 220. In
some embodiments, the sensors 230 may be removably coupled to the
structure 220. The sensors 230 may be positioned to protrude into
the inlet port 142 and/or the outlet port 144 when the
humidification chamber 140 is mounted on the base unit 135. In the
illustrated embodiment, two of the sensors 230 are positioned to
measure at least one characteristic of the gases flow at the inlet
port 142, and one of the sensors 230 is positioned to measure at
least one characteristic of the gases flow at the outlet port 144.
In some embodiments, one of the sensors 230 is positioned to
measure at least one characteristic of the gases flow at the inlet
port 142, and two of the sensors 230 are positioned to measure at
least one characteristic of the gases flow at the outlet port 144,
when the humidification chamber 140 is mounted on the base unit
135. In some embodiments, two of the sensors 230 are positioned to
measure at least one characteristic of the gases flow at the inlet
port 142, while one sensor is positioned at the outlet port 144.
The sensors 230 can also be arranged in other configurations with
different combinations at the inlet port 142 and the outlet port
144. The structure 220 can also include more than 3 sensors or less
than 3 sensors.
[0034] In some embodiments, the sensors 230 are mounted in planes
parallel or substantially parallel with respect to each other.
Further, the sensors 230 can be oriented in the same direction with
respect to each other. In the illustrated embodiment in FIG. 2, the
sensors 230 are situated parallel to the x-y plane and extend along
the x-axis. In some embodiments, the placement of the sensors 230
advantageously enables for the humidification chamber 240 to slide
into the humidification apparatus 130 with respect to the structure
220 (as shown in FIG. 3). Moreover, as seen in FIG. 2, the sensors
230 are all placed perpendicular to a vertical plane. Two of the
sensors 230 are positioned in a different but substantially
parallel horizontal planes. Accordingly, one of these sensors may
measure characteristic of a gas at a different point in time as the
gas flows through the humidification chamber 140 because of the
difference in location. That is, a first sensor is positioned such
that the gas passes over it shortly before the gas passes over the
second sensor. In some embodiments, two of the sensors 230 may be
mounted in the same horizontal plane or substantially the same
horizontal plane so that the sensors 230 can measure characteristic
of the gas flow at the same time. In some embodiments, if the
sensors are measuring different characteristics, it may be
advantageous to have them measure the characteristics at the same
point in time of gas flow for the purposes of comparison.
[0035] Further, FIG. 3 illustrates the humidification chamber 140
attached to the base 135. As seen from the figure, some of the
portions of the humidification chamber 140 are occluded or covered
by the base 135, particular the top portions of the humidification
chamber 140. The covered portions may act as an insulator for the
humidification chamber 140 and trap heat inside the humidification
chamber 140. Accordingly, in some embodiments, it may be
advantageous to have more surface area of the humidification
chamber 140 exposed to the air to avoid the insulation effect. In
an embodiment, the base 135 as illustrated herein is designed to
increase exposure of the surface area of the humidification chamber
140 to external environment. For example, in the embodiments
illustrated, about 45% to about 50% of the chamber is exposed as
viewed from the top. In some embodiments, about 40% to about 45% of
the chamber is exposed as viewed from the top. The base 135 and the
humidification chamber 140 can also be designed to expose more than
50%, such as 60% or 70% of the chamber. In some embodiments, the
percentage can be calculated by measuring the entire surface area
of the humidification chamber 140 and dividing the exposed surface
area by the entire surface area.
[0036] In some embodiments, the sensors 230 each may measure one of
temperature, flow rate, or humidity. In some embodiments, the
sensors 230 may measure a combination of any one of temperature,
flow rate, and humidity. In some embodiments, two of the sensors
230 may be used in combination to derive a characteristic of the
gases flow; for example, two of the sensors 230 may be positioned
to measure gases temperature at the inlet port 142, and the
controller 132 may use the two measurements to derive a flow rate
of the gases. In some embodiments, one of the sensors 230 may be
positioned downstream of the humidification apparatus 130, for
example, near the patient interface 160. In some embodiments, one
of the sensors 230 may be positioned at the heater plate 240.
[0037] Heating of the heater plate 240 is controlled by the
controller 132. The controller 132 determines the amount of power
required to provide sufficient heat to the liquid within the
humidification chamber 140. The surface of the heater plate 240 is
in contact with a thermally conductive surface of the
humidification chamber 140. This provides a thermally conductive
pathway to enable the transfer of heat from the heater plate 240 to
the liquid within the humidification chamber 140.
[0038] In some embodiments, the structure 220 is removably coupled
to the base unit 135. In some embodiments, the structure 220 may be
permanently coupled to the base unit 135. In some embodiments, the
structure 220 may be integrally formed with the base unit 135. The
structure 220 can form a support structure for the sensors 230. The
structure 220 includes features that aid with alignment and
orientation of the humidification chamber 140 relative to the base
unit 135 and/or the sensors 230, which will be discussed in further
detail below, and as described in the embodiments disclosed in U.S.
Provisional Patent Application No. 62/059,339 and International
Application No. PCT/NZ2014/000201, the contents of which are hereby
incorporated by reference in their entirety.
[0039] The structure 220 is coupled to or integral with a portion
of the base unit 135 that is positioned above the heater plate 240.
This positions electronic components within the base unit 135 and
electronic components within the structure 220 above likely leak
points of the humidification chamber 140 when the humidification
chamber 140 is mounted on the base unit 135 in contact with the
heater plate 240. The display 210 is positioned on an upper surface
of the base unit 135 above the structure 220. This increases
visibility of the display 210 in use. As a result, the
humidification chamber 140 is mounted within a recess 250 formed by
the base unit 135. The structure 220 at least partially encloses
the humidification chamber 140 within the recess 250. This enables
the sensors 230 to protrude into the inlet port 142 and/or the
outlet port 144 of the humidification chamber 140 to determine a
characteristic of the gases flow. As discussed above, the
orientation and placement of the sensors 230 can enable the
humidification chamber 140 to be mounted within the recess 250.
[0040] FIG. 4 illustrates the humidification chamber 140 in more
detail. The humidification chamber 140 includes a nose 310 and
apertures 330. The nose 310 mates with a corresponding hood 420 (as
shown in FIGS. 5A-5B). The nose 310 aids alignment between the
humidification chamber 140 and the structure 220. In some
embodiments, the nose 310 includes rails 320, which mate with
corresponding grooves 430 in the structure 220 (as shown in FIGS.
5A-5B). The rails 320 also aid alignment between the humidification
chamber 140 and the structure 220. In some embodiments, the nose
310 does not include the rails 320 and the structure 220 does not
include the grooves 430. In some embodiments, the tongue 312 of the
nose 310 is tapered. The tapered tongue 312 can advantageously
prevent the humidification chamber 140 from rocking with respect to
the hood 420. Rocking may result in disconnection of sensors
230.
[0041] The apertures 330 can receive the sensors 230 that are
positioned on the structure 220 (refer to FIGS. 5A-5B). Thus, when
the humidification chamber 140 is mounted on the base unit 135, the
sensors 230 protrude into the apertures 330 of the humidification
chamber 140. The sensors 230 measure a characteristic of the gases
flow in the humidification chamber 140 through the apertures 330.
The apertures 330 are positioned at or near the inlet port 142
and/or the outlet port 144 of the humidification chamber 140. In
some embodiments, the apertures 330 each further include a seal or
barrier (not shown) to maintain a sealed pathway for the gases
flow. The seal can be an o-ring. In some embodiments, the apertures
330 can include a grommet or an elastic glove that can protect the
sensors 230 as they are inserted into the apertures 330.
[0042] In the illustrated embodiment, two of the apertures 330 are
positioned near the inlet port 142 and one of the apertures 330 is
positioned near the outlet port 144. In some embodiments, one of
the apertures 330 is positioned near the inlet port 142 and two of
the apertures 330 are positioned near the outlet port 144. In some
embodiments, variations or different combinations of the apertures
330 may be positioned at or near each port. For example, multiple
of the apertures 330 may be positioned at both the inlet port 142
and the outlet port 144.
[0043] As discussed above, In some embodiments, the sensors 230 are
oriented in the same direction and positioned in same or parallel
planes. Accordingly, the apertures 330 may also be positioned on
the humidification chamber 140 such that they align with their
respective sensors 230. In some embodiments, the apertures 330 face
the same or substantially the same direction as illustrated in FIG.
4. Thus, as the humidification chamber 140 is slid horizontally
into the base 135, the sensors 230 align with the apertures 330 and
positioned to measure the characteristics of gas flow at particular
locations near the inlet port 142 and the outlet port 144. As a
result, the sensors are all positioned within the chamber in a
single connection step by a user such that the user does not need
to separately position the sensors in the chamber as is required by
prior art devices.
[0044] In some embodiments, the outlet port 144 (FIG. 4) includes a
vertical portion 144b and a horizontal portion 144a connected by a
curved portion 144c. While the illustrated embodiment shows an
L-shape or a right angle, the angle between horizontal portion 144a
and the vertical portion 144b can be greater than 90 degrees.
Higher angles may make the transition from the vertical portion
144b to the horizontal portion 144a smoother and as a result may
decrease turbulence in the air moving from the vertical portion
144b to the horizontal portion 144a. In some embodiments, the
horizontal portion 144a may advantageously enable a user to connect
a conduit with the humidification chamber 140 either before the
humidification chamber 140 is attached to the base 135 or after the
attachment with the base 135. In some embodiments, the inlet port
142 can also include a vertical portion, a horizontal portion, and
a curved portion as discussed above with respect to the outlet
port.
[0045] FIGS. 5A-5B illustrate different views of an embodiment of
the structure 220. The structure 220 includes a shroud 410, the
hood 420, the sensors 230, and a post 440. The shroud 410 can
receive a connector, for example, a connector configured to connect
the inspiratory tube 150 to the humidification apparatus 130. In
some embodiments, the connector is configured to form an electrical
connection between the inspiratory tube 150 and the humidification
apparatus 130. In some embodiments, the connector is configured to
form an electrical connection with the structure 220, and the
structure 220 is configured to form an electrical connection with
the base unit 135. As a result, the structure 220 includes
electrical contacts 415 within the shroud 410, as shown in more
detail in FIG. 5A. The shroud 410 helps to align the connector of
the inspiratory tube 150 with the structure 220. The shroud 410
facilitates pneumatic coupling between the inspiratory tube 150 and
the outlet port 144 of the humidification chamber 140. In the
illustrated embodiment, the structure 220 includes one of the
sensors 230 within the shroud 410. Thus, as connection is made
between the structure 220, the connector of the inspiratory tube
150, and the outlet port 144 of the humidification chamber 140, the
one of the sensors 230 within the shroud 410 protrudes into the
outlet port 144 and an electrical connection is formed between the
inspiratory tube 150 and the humidification apparatus 130. In some
embodiments, the shroud 410 protects the electrical contacts 415
from spills or other environmental conditions.
[0046] With continued reference to FIGS. 5A-5B, the hood 420 can
accommodate the nose 310 of the humidification chamber 140. In some
embodiments, the hood 420 includes grooves 430 to mate with the
optional rails 320 that protrude from the nose 310 of the
humidification chamber 140. The hood 420 can include an optional
opening 425. The opening 425 allows heat energy from the
humidification chamber 140 to dissipate to the surrounding ambient
environment. Thus, the opening 425 reduces the mechanical contact
between the humidification chamber 140 and the structure 220. This
improves cooling of the humidification chamber 140 as it is further
isolated from the structure 220.
[0047] In the illustrated embodiment, the post 440 includes two of
the sensors 230. Thus, the post 440 provides a platform that
facilitates coupling of the two of the sensors 230 with two of the
apertures 330 that are associated with the inlet port 142 of the
humidification chamber 140. The post 440 enables the two of the
sensors 230 to protrude into the two of the apertures 330 of the
inlet port 142. This enables the two of the sensors 230 to more
accurately determine a characteristic of the gases flow.
[0048] In some embodiments, the controller 132 adjusts the power
supplied to the heater plate 240 for adding energy into the
respiratory assistance system 100. The added energy from the heater
plate 240 can evaporate liquid in the humidification chamber 140.
The evaporated liquid can add humidity to the respiratory gases. In
some embodiments, the controller 132 can continue to supply power
to the heater plate 240 until a characteristic of the respiratory
gases at the outlet port 144 reaches a predetermined output
condition, or a set point. The characteristic of the respiratory
gases at the outlet port 144 can be measured by the sensors 230
(discussed above) at the outlet port 144. In some embodiments, the
characteristic of the respiratory gases can be measured at other
locations in the respiratory assistance system 100. For example,
the characteristic of the respiratory gases can be measured at the
patient interface 160. In some embodiments, characteristics of
respiratory gases can include humidity, temperature, and flow
rate.
[0049] In some embodiments, the respiratory assistance system 100
does not include a humidity sensor to directly measure humidity
conditions of the respiratory gases. In such an embodiment, the
controller 132 can control the heater plate 240 to deliver a target
humidity condition using temperature and/or flow rate measurements
provided by the sensors 230 to estimate humidity conditions of the
respiratory gases delivered by the humidification apparatus 130 and
to use such estimated humidity conditions to control the heater
plate 240 to generate humidity. Some conditions of the gases
supplied to the humidification apparatus 130 by the gases source
110 may compromise the ability of the humidification apparatus 130
to add sufficient humidity.
[0050] In some embodiments, the controller 132 relying on estimated
humidity conditions based on temperature measurements to control
the heater plate 240 may result in compromised humidity generation.
For example, when the gases source 110 is drawing in ambient gases
to supply to the humidification apparatus 130, the characteristics
of the gases drawn in by the gases source 110 can fluctuate
depending on ambient conditions. In a desert environment, the
ambient air may have high temperature and low humidity. When
respiratory gases enter the humidification chamber 140, the
controller 132 may initially provide power to the heater plate 240
to add heat to the liquid in the humidification chamber 140 to
evaporate liquid and add humidity to the gases; however, when the
incoming gases are already at a high temperature, the controller
132 may stop providing power to the heater plate 240 before
sufficient humidity or vapor has been added to the respiratory
gases. Consider an instance where the temperature of the ambient
gases drawn in by the gases source 110 is 34 degrees Celsius and
the set point temperature of the gases at the outlet port 144 is 37
degrees Celsius. The controller 132 may provide power to the heater
plate 240 until the respiratory gases reaches 37 degrees at the
outlet port 144. However, since the ambient gases temperature is
already close to the set point temperature, the heater plate 240
may not need to add much heat for the respiratory gases to reach
the set point temperature. The amount of heat needed may not be
enough. In particular, if the incoming ambient gas is dry, the
gases delivered at the patient interface 160 may not have
sufficient humidity for patient comfort.
[0051] Moreover, humidity addition may further be compromised
because of the flow rate of the gases and the design constraints of
the respiratory assistance system 100. In some embodiments, a high
flow therapy may be required. Accordingly, there may be even less
time to add humidity to the gases because of the higher flow.
Furthermore, there may be competing constraints of reducing the
size of the humidification chamber 140 and the available surface
area of the liquid interacting with the volume of respiratory gases
in the humidification chamber 140. Accordingly, in some
embodiments, it may be advantageous to decrease the temperature of
the respiratory gases. Further, in some embodiments, it may be
advantageous to increase the surface area of liquid interacting
with the volume of the respiratory gases flowing through the
humidification chamber 140. The humidification chamber 140 can be
modified as described below to improve heat transfer and/or
increase surface area between the liquid and the flowing
respiratory gases.
[0052] The structure 220 at least partially encloses the
humidification chamber 140 when it is mounted on the base unit 135.
As discussed, features on the structure 220 facilitate coupling of
the humidification chamber 140 with the sensors 230 to provide more
accurate determinations of characteristics of the gases flow. The
features on the structure 220 also aid with alignment and
orientation of the humidification chamber 140 with respect to the
base unit 135 or the sensors 230. The humidification chamber 140
being partially enclosed facilitates greater heat loss between the
humidification chamber 140 and the surrounding ambient
environment.
[0053] FIG. 6 illustrates an embodiment wherein a structure 500
includes an active cooling mechanism 540 to facilitate heat loss
from the humidification apparatus 130 to the surrounding ambient
environment. The active cooling mechanism 540 moves air onto and
around the humidification chamber 140. This encourages heat loss
from the humidification chamber 140 to the surrounding ambient
environment. In some embodiments, the active cooling mechanism 540
includes a fan. In some embodiments, the active cooling mechanism
540 may include a blower. In some embodiments, the structure 500
includes an air inlet to allow the active cooling mechanism 540 to
draw air into the structure 500 from the surrounding ambient
environment. In some embodiments, the structure 500 includes an air
outlet to allow the active cooling mechanism 540 to expel air from
the structure 500 out to the surrounding ambient environment. The
active cooling mechanism 540 may aid heat loss in the structure
500.
[0054] In the illustrated embodiment, the structure 500 including
the active cooling mechanism 540 provides an increased enclosure
effect on the humidification chamber 140 relative to the structure
220 illustrated in FIGS. 5A-5B. For example, a hood 520 does not
include an opening such as the opening 425 of the hood 420 to
encourage further heat loss. In another example, the body of the
structure 500 extends such that it interacts more fully with the
humidification chamber 140. In some embodiments, the active cooling
mechanism 540 may be combined with the structure 220 in FIGS. 5A-5B
to further enhance heat loss. In some embodiments, the structure
220 or the structure 500 may include a thermally insulating
material to slow the spread of heat therein. In some embodiments,
the thermally insulating material may be combined with the active
cooling mechanism 540.
[0055] FIG. 7 is an example of a humidification chamber 600
including a passive cooling mechanism 650. The passive cooling
mechanism 650 may be any mechanism that passively encourages heat
transfer to occur between the humidification chamber 600 and the
surrounding ambient environment, for example, a heat sink including
fins or pins. The passive cooling mechanism 650 acts to increase
the surface area of the humidification chamber 600 that can be
utilised for heat loss.
[0056] In some embodiments, the passive cooling mechanism 650 may
be permanently coupled to the humidification chamber 600. Permanent
coupling of the passive cooling mechanism 650 could be using a
snap-fit mechanism, clipping, adhesives or welding mechanisms. In
some embodiments, the passive cooling mechanism 650 may be an
integral part of the humidification chamber 600. In some
embodiments, the passive cooling mechanism 650 may be removably
coupled to the humidification chamber 600. Removable coupling of
the passive cooling mechanism 650 allows the humidification chamber
600 to couple with different structures, for example, the structure
220 or the structure 500.
[0057] In the illustrated embodiment, the passive cooling mechanism
650 includes a fin. In some embodiments, the passive cooling
mechanism 650 may include multiple fins. The fin 650 protrudes from
the humidification chamber 600 such that the alignment and
orientation features of the humidification chamber 600 are still
able to facilitate coupling between the humidification chamber 600
and the structure 220.
[0058] The fin 650 may comprise the same material as the
humidification chamber 600. In some embodiments, the fin 650 may
include a more thermally conductive material to further promote
heat loss from the humidification chamber 600. The geometry of the
fin 650 may depend on the geometry of the structure 220 to which
the humidification chamber 600 is to be coupled. For example, In
some embodiments, the fin 650 may extend substantially vertically
towards the ports of the humidification chamber 600. In some
embodiments, the fin 650 may extend substantially horizontally from
the humidification chamber 600. A combination of the above
geometries may also be used.
[0059] FIG. 8 illustrates an embodiment that includes a wall 750 of
a humidification chamber 700 that has been enlarged. The wall 750
includes at least a portion that bulges out between a base 760 and
an upper surface 770 of the humidification chamber 700. This
increases the surface area of the humidification chamber 700,
without substantially increasing its footprint. Thus, a greater
amount of humidity is transferred to the respiratory gases. The
humidification chamber 700 is mountable on the base unit 135 with
minimal or no changes required to the base unit 135. In some
embodiments, the humidification chamber 700 may include different
geometries that increase the surface area. Increasing the surface
area increases the area of contact between the liquid and the
respiratory gases, which promotes more efficient humidification of
respiratory gases. For example, the size of the humidification
chamber 700 may be increased, or the shape of the humidification
chamber 700 may be optimised to produce an optimal surface area
between the liquid and the respiratory gases. In another example,
the interior of the wall 750 may include microstructures as
disclosed in International Application No. PCT/NZ2013/000113, the
contents of which are hereby incorporated by reference in their
entirety.
[0060] FIG. 9 illustrates an embodiment wherein a humidification
chamber 800 includes regions 850 that facilitate improved heat
loss. The regions 850 include a material that has a higher thermal
conductivity than the material of the humidification chamber 800.
In the illustrated embodiment, two regions 850 are utilised. In
some embodiments, a single region 850 or multiple regions 850 can
be used to encourage heat loss from the humidification chamber 800
to the surrounding ambient environment. In some embodiments, the
material may be metal, for example, copper. The regions 850
facilitate greater heat loss through a wall 860 of the
humidification chamber 800. This enables heat loss to occur without
altering the geometry of the humidification chamber 800. In the
illustrated embodiment, the regions 850 are permanently coupled to
the humidification chamber 800. In some embodiments, the regions
850 may be integral to the humidification chamber 800. In some
embodiments, the entirety of the humidification chamber 800 or the
wall 860 of the humidification chamber 800 may be made from
thermally conductive material.
[0061] In some embodiments, the humidification chamber 140 may
include a cooling structure 1050 as shown in FIG. 10. The cooling
structure 1050 can be located inside the humidification chamber
140. In some embodiments, the cooling structure 1050 may be a
separate component that can be removably inserted in the
humidification chamber 140. The cooling structure 1050 may be
secured using a fastener or designed to fit around the shape of the
humidification chamber 140. In some embodiments, the cooling
structure 1050 is secured against the side walls 1060 of the
humidification chamber 1000. The cooling structure 1050 may
completely or partially cover the sidewalls 1060. In some
embodiments, the cooling structure 1050 is placed near the inlet
port 142. In some embodiments, placing the cooling structure 1050
near the inlet port 142 may result in increased humidity generation
because of a higher temperature gradient.
[0062] In some embodiments, the cooling structure 1050 may include
channels as shown in FIG. 11. The cooling structure 1050 may also
include microstructures as described in International Application
No. PCT/NZ2013/000113. The channels may run parallel to the x axis
or the y-axis or any angle between the x and y axes. The channels
may be straight or curved. In some embodiments, the channels can be
in the shape of spirals. The channels can reduce gas temperature
because of the increase in evaporative cooling. The channels can
also increase surface area of the interaction between liquid and
respiratory gases. For example, the channels located along the side
wall of the humidification chamber 140 can collect liquid through
capillary forces which evaporates directly from the side walls. In
some embodiments, adding the channels can increase the humidity
output by at least 7 mg/L.
[0063] FIG. 10 illustrates a portion of the channels discussed
above. Each zone has different design parameters as illustrated in
FIGS. 11 and 12. Modifying the design parameters can change the
wetting angle of the surface of the cooling structure 1050. As
discussed below, the wetting angle can determine capillary height
and also surface forces. In some embodiments, the channels are
designed to maximize the wetting angle. Increased wetting can
increase capillary height. The channels can also be designed to
stop or start capillary filling under certain conditions, such as,
at a particular location, or temperature, temperature gradient, or
humidity levels. In some embodiments, the design of channels can
provide controlled evaporative cooling according to predetermined
parameters. Accordingly, the channel parameters may affect
evaporation in the humidification chamber 140. In some embodiments,
the channel parameters are selected to maximize evaporation. In
some embodiments, the Lf parameter is the same as L.sub..infin. in
FIG. 14.
[0064] In some embodiments, the sidewalls 1060 may also include
heating elements on either the interior or exterior of the
humidification chamber 140. The cooling structure 1050 may also
include heating elements. The heating elements of the sidewall can
increase evaporative rate of the liquid adhering to the cooling
structure 1050. Further, In some embodiments, the heater plate 240
can be designed to directly heat the chamber walls. For example,
the back of the heater plate 240 can be arranged to directly
contact the chamber walls and heat the chamber walls directly. The
heater plate 240 can also have a diameter larger than the cooling
structure 1050. Thus, there may be a gap between the cooling
structure 1050 and the sidewall 1060. Accordingly, the heat from
the heater plate 240 can be trapped behind the sidewall and the
cooling structure 1050 and heat the cooling structure 1050.
[0065] In some embodiments, the cooling structure 1050 is
manufactured using injection moulding. The materials can be
polycarbonate, Arnitel VT3108, PP+Techsurf or any other
thermoplastics. The materials can also affect contact angle or the
wetting of the liquid on the cooling structure 1050 as shown in
FIG. 13. For a polycarbonate material, the contact angle for water
can be higher than a material like Arnitel. The contact angle can
determine wettability of the material. In some embodiments, higher
wettability may be desired to increase capillary height.
[0066] FIG. 14 illustrates example calculations of capillary
heights as a function of design parameters and materials of the
cooling structure 1050 shown in FIG. 11. Larger capillary height
can indicate that a column of liquid will rise higher along the
channels of the cooling structure 1050. When the liquid rises
higher, the surface area of the liquid available for evaporative
cooling can also increase. As discussed above, evaporative cooling
can decrease temperature of the respiratory gases in the
humidification chamber. In some embodiments, for the equation shown
in FIG. 14, c is the wetted x-sectional length of the channel, A is
the cross-sectional area, .sigma. is liquid/vapour surface tension,
.rho. is liquid density, .xi. is inclination of channel (which is
90 deg if vertical) and g is gravity constant.
[0067] FIG. 15 illustrates results from one of the embodiments
described above with the cooling structure 1050 having channels
attached to sidewalls near the inlet port 142 and the outlet port
144. The figure shows that the cooling structure 1050 including
channels placed inside the humidification chamber 140 can increase
the relative humidity added to the respiratory gases.
[0068] FIG. 16 illustrates an embodiment of the humidification
chamber 140 with a base structure 1602 placed on the base of the
humidification chamber 140. In some embodiments, the base structure
1602 can be integral of the base of the chamber. The base structure
1602 can also be removably inserted in the humidification chamber
140. The base structure 1602 can cover some or the entire portion
of the base of the humidification chamber 140. In some embodiments,
the base structure 1602 lies above the heater plate 240. The base
structure 1602 can be designed to hold a thin layer of liquid. An
embodiment of the base structure 1602 is shown in FIG. 17. A thin
layer of liquid may evaporate faster than a larger volume of
liquid. The thin layer of liquid can be continuously maintained
using a source (not shown). The base structure 1602 can include
channels as discussed above as shown in FIG. 17. Liquid can be fed
from a source and directed towards the channels. The design of the
channels can increase evaporation. For example, the height of the
channel or any other dimension may vary along the length of the
channel to account for variations in the base temperature or gas
conditions to prevent thin-film break-up (dry out) and maintain
high evaporation rates. In some embodiments, the wall tilt is
adjusted to maximize fluid recirculation (thus temperature
homogenization) via surface tension (Marangoni) driven
convection.
[0069] In some embodiments, the controller 132 can automatically
adjust the set point based on detecting the temperature of the
respiratory gases at the inlet port 142. The controller 132 can
also track humidity and/or flow rate of the respiratory gases at
the inlet port 142. In some embodiments, the controller 132 can
receive a humidity indication based on a user input. In some
embodiments, the controller 132 can receive humidity measurements
from a humidity sensor.
[0070] The controller 132 can measure a difference between the
inlet gas temperature and the set point. If the temperature
difference is small, the controller 132 can automatically increase
the set point temperature. This can enable the heater plate 240 to
run longer and add sufficient humidity to the respiratory gases. In
some instances, if the controller 132 determines that the humidity
in the gases at the inlet port 142 is not that different from the
set point humidity, the controller 132 may not change the
temperature set point. The controller 132 can also determine the
set point based on the flow rate. For a high flow rate, the
controller 132 may increase the temperature set point to increase
humidity generation.
[0071] Unless the context clearly requires otherwise, throughout
the description and the claims, the words "comprise", "comprising",
and the like, are to be construed in an inclusive sense as opposed
to an exclusive or exhaustive sense, that is to say, in the sense
of "including, but not limited to".
[0072] Reference to any prior art in this specification is not, and
should not be taken as, an acknowledgement or any form of
suggestion that that prior art forms part of the common general
knowledge in the field of endeavour in any country in the
world.
[0073] The disclosed apparatus and systems may also be said broadly
to consist in the parts, elements and features referred to or
indicated in the specification of the application, individually or
collectively, in any or all combinations of two or more of said
parts, elements or features.
[0074] Where, in the foregoing description reference has been made
to integers or components having known equivalents thereof, those
integers are herein incorporated as if individually set forth.
[0075] It should be noted that various changes and modifications to
the presently preferred embodiments described herein will be
apparent to those skilled in the art. Such changes and
modifications may be made without departing from the spirit and
scope of the disclosed apparatus and systems and without
diminishing its attendant advantages. For instance, various
components may be repositioned as desired. It is therefore intended
that such changes and modifications be included within the scope of
the disclosed apparatus and systems. Moreover, not all of the
features, aspects and advantages are necessarily required to
practice the disclosed apparatus and systems. Accordingly, the
scope of the disclosed apparatus and systems is intended to be
defined only by the claims that follow.
* * * * *