Moisture removal, condensation, and humidity control device for respiration circuit

Abstract

To provide a moisture removal, condensation, and humidity control device for a respiration circuit.SOLUTION: A moisture removal, condensation, and humidity control device 10 for a respiration circuit includes a respiration circuit tube body 11 for determining a respiratory gas conduit tube 12. The respiratory gas has a first humidity level and a predetermined moisture level. A dry gas conduit tube 14 is adjacent to at least part of the respiratory gas conduit tube. A dry gas flow is configured so as to have a second humidity level lower than the first humidity level. A moisture permeable route is provided between the respiratory gas conduit tube and the dry gas conduit tube so that the humidity in the flow of the respiratory gas is reduced and the moisture is transferred to the dry gas flow. The moisture permeable route can be provided by a moisture permeable part that is permeable to steam, but is not permeable to liquid water, or by one or two or more small holes that allow the liquid water to be discharged from the respiratory gas conduit tube to the dry gas conduit tube.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Application No. 62 / 148,077, filed April 15, 2015, the disclosure of which is incorporated herein by reference in its entirety. The present invention relates generally to medical devices, and more particularly to a moisture removal and condensation and humidity control apparatus for placement in a breathing circuit. [Background technology]

[0002] Breathing circuits deliver medical gases to patients under pressure at a predetermined volume and respiratory rate. Medical gases are often humidified by a humidifier located at or near the ventilator or respirator. An optimal breathing circuit delivers 100% RH medical gas to the patient while reducing the amount of moisture and subsequent condensation that is returned to the ventilator through the expiratory limb. Therefore, the humidified gas must pass through all or most of the tubing and has time to cool. Cooling of the gas leads to rainout or condensation in the breathing tubing and water collection within the breathing circuit.

[0003] Several viable solutions to the rainout problem have been proposed. One such proposed solution is a heated wire that runs along the length of the tubing. The heated wire can be located inside the tubing or can be integrated along the inside of the tubing. The heated wire heats the humidified gas passing through the tubing to prevent the gas from cooling, thus preventing the problem of water condensation from the gas passing through the breathing circuit. However, manufacturing such a heated breathing circuit is time-consuming and expensive.

[0004] Another possible solution that eliminates the heating wire is to provide a water collection device somewhere in the breathing circuit. The water collection device is typically placed in the expiratory limb of the breathing circuit and allows excess condensation to collect and be manually removed before the gas enters the ventilator or respirator. It is known that excess condensation entering the ventilator or respirator from the expiratory limb of the breathing circuit can damage the device.

[0005] Most often, water collection devices are designed to trap condensed water vapor in a removable container. When the container is removed, a valve activates, creating an airtight seal against the breathing circuit. However, this type of water collection device requires monitoring and manual draining, creating an infection risk for the patient or caregiver. Moisture removal and condensation management are not automatic. Furthermore, the removable container is often located at only one discrete point along the breathing circuit, requiring a lowered height to collect the liquid by gravity, which may be impractical.

[0006] Another possible solution is to provide a permeable membrane in the breathing circuit tubing that is permeable to water vapor but not liquid water, allowing moisture within the breathing gas stream within such tubing to dissipate through such membrane to the outside of the tubing and into the ambient air surrounding the tubing. The problems with this solution are at least twofold: first, a thin-walled membrane exposed to the ambient environment can be easily ruptured or damaged; and second, due to the relatively high humidity in ambient conditions, the humidity differential between the breathing gas stream and the ambient environment can be limited, limiting the ability of moisture to passively dissipate through the permeable membrane into the ambient environment.

[0007] It would therefore be desirable to provide an improved apparatus for removing or reducing water vapor, moisture, or condensation in a breathing circuit. Furthermore, it would be desirable for an improved apparatus for removing water vapor, moisture, or condensation from a breathing tubing that eliminates the need to monitor the water collection device or heat the expiratory limb of the breathing tubing, is independent of the positioning of the water collection device, protects the water collection device and its moisture and moisture transmission mechanisms from damage, and enhances moisture removal and condensation management in a breathing circuit. Summary of the Invention [Problem to be solved by the invention]

[0008] The above-mentioned needs are largely met by the present invention, in which a moisture removal and condensation and humidity control device for a breathing circuit disposed between a patient and a ventilator is provided, the device comprising a breathing circuit tubing defining a breathing gas conduit for a flow of breathing gas, the breathing gas having a first humidity level and a predetermined humidity or condensation level. A dry gas conduit is disposed adjacent to at least a portion of the breathing gas conduit for a dry gas flow in the dry gas conduit, the dry gas flow being configured to have a second humidity level lower than the first humidity level. A moisture permeable pathway is included between the breathing gas conduit and the dry gas conduit, reducing humidity in the breathing gas flow and allowing moisture or condensation in the breathing gas flow to be transferred to the dry gas flow. The dry gas conduit is closed to ambient air surrounding the device.

[0009] In one embodiment of the invention, the breathing circuit tubing includes a permeable portion that is permeable to water vapor but not to liquid water, such that the permeable portion of the breathing circuit tubing provides a moisture transmission path.

[0010] In another embodiment of the invention, the breathing circuit tubing is formed by an inner tubing defining a breathing gas conduit, the dry gas conduit is formed by an outer tubing surrounding the inner tubing, and the dry gas conduit is defined by an annular flow conduit defined between the inner and outer tubing.

[0011] In another embodiment of the invention, the breathing circuit tubing is formed by an inner tubing defining a breathing gas conduit, the dry gas conduit is formed by an outer tubing surrounding the inner tubing, an annular space is defined between the inner and outer tubings, and a partition is formed between the inner and outer tubings in the annular space to divide the dry gas conduit into a first delivery conduit for flow of dry gas from the first end of the device to the second end of the device and a second return conduit for flow of dry gas from the second end of the device to the first end of the device.

[0012] In another embodiment of the present invention, the permeable portion of the breathing circuit tubing is a permeable membrane that forms a portion of the breathing circuit tubing.

[0013] In another embodiment of the invention, the breathing circuit tubing includes one or more small holes that allow liquid water to escape from the breathing gas conduit to the dry gas conduit, such that a moisture transmission path is provided by such one or more small holes in the breathing circuit tubing.

[0014] In another embodiment of the invention, the breathing circuit conduit and the dry gas conduit share a common bulkhead having a moisture permeable pathway.

[0015] In another embodiment of the invention, the common partition wall includes a permeable portion that is permeable to water vapor but not to liquid water, such permeable portion of the common partition wall providing a moisture vapor transmission path.

[0016] In another embodiment of the invention, the permeable portion of the breathing circuit tubing is a permeable membrane that forms part of the common septum described above.

[0017] In another embodiment of the invention, the common partition includes one or more small holes that allow liquid water to escape from the breathing gas conduit to the dry gas conduit, such one or more small holes in the common partition providing a moisture transmission path.

[0018] In another embodiment of the invention, an outlet port is provided on the device for a dry gas conduit having a filter, through which the dry gas escapes into the ambient environment surrounding the device.

[0019] In another embodiment of the invention, an input port is provided on the device for a dry gas conduit having a flow or volume control element for the dry gas flow.

[0020] In another embodiment of the invention, an outlet port is provided on the device for a dry gas conduit connected to a suction source.

[0021] In another aspect of the present invention, a method of removing moisture or controlling condensation in a breathing circuit is provided, comprising providing an apparatus as disclosed in any of the above-described embodiments of the present invention. The apparatus is constructed and arranged to be placed between a ventilator and a patient. Respiratory gas is supplied to the patient via the breathing circuit tubing. Dry air is supplied through a dry gas conduit to remove moisture or liquid water condensate from the breathing gas conduit. In another embodiment, one or more of the first and second humidity levels can be monitored using a humidity sensor. In one or more further embodiments, the breathing circuit tubing is the expiratory limb of the ventilator circuit.

[0022] Certain embodiments of the invention have been generally described herein in order that the detailed description thereof may be better understood, and in order that the present contribution to the art may be better appreciated. Additional embodiments of the invention exist that will be described below and will form the subject of the claims appended hereto.

[0023] In this regard, before describing at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments in addition to those described and of being practiced and carried out in various ways. Similarly, it is to be understood that the phraseology and terminology employed in this method specification, as well as the abstract, are for the purpose of description and should not be regarded as limiting.

[0024] As such, those skilled in the art will appreciate that the conception on which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be interpreted as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic diagram illustrating an apparatus incorporated within or as part of a breathing gas circuit, in accordance with one or more embodiments of the present invention. [Figure 2] 2 is a schematic cross-sectional view illustrating the device of FIG. 1 in accordance with one or more embodiments of the present invention. [Figure 3] 2 is a schematic cross-sectional view illustrating the device of FIG. 1 in accordance with one or more additional embodiments of the present invention. [Figure 4] 1 is a schematic cross-sectional view of an apparatus incorporated within or as part of a breathing gas circuit, in accordance with one or more additional embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will now be described with reference to the drawings, in which like elements are designated by like reference numerals throughout. One or more embodiments according to the present invention provide a moisture removal and condensation and humidity control device for a breathing circuit that rapidly removes water vapor or condensate from humidified medical gas passing through the breathing circuit between a ventilator and a patient or between a patient and a ventilator. As used herein, a "breathing circuit" or "breathing gas circuit" is any arrangement of tubing or conduits that carries gas to be administered between a patient, such as from a ventilator, and may include additional attached accessories or devices. Such "breathing gas" may include oxygen, air, or any combination thereof, and is configured to absorb or humidify a high level of moisture prior to or during administration to a patient, as appropriate for medical use.

[0027] FIG. 1 is a schematic diagram illustrating an apparatus incorporated into or as part of a breathing gas circuit according to one or more embodiments of the present invention. The moisture removal and condensation and humidity control apparatus 10 for a breathing circuit includes a section or length of breathing circuit tubing 11 defining a breathing gas conduit 12 for a flow of breathing gas (B). The breathing gas flows from a first, upstream end 10A of the apparatus 10 through the conduit 12 defined within the apparatus 10 to a second, downstream end 10B of the apparatus 10. The breathing gas is configured to have a first humidity level and a predetermined humidity level, which can be calibrated based on the patient's needs. In one embodiment, such a length of breathing circuit tubing 11 can be located in the expiratory limb of the breathing circuit, for example, anywhere between the patient and the ventilator. In the apparatus 10, a dry gas conduit 14 is defined adjacent at least a portion of the breathing gas conduit 12 between the first end 10A and the second end 10B for the dry gas flow (D). The dry gas stream (D) is configured to have a second humidity level that is lower than the first humidity level in the breathing gas conduit (B). The dry gas stream is coupled to one or more input ports 40 that deliver the dry gas stream (D) from a dry gas source (not shown) to the dry gas conduit 14, where it then flows substantially parallel to or around the breathing gas conduit 12.

[0028] Figure 2 is a schematic cross-sectional view of the device of Figure 1 in accordance with one or more embodiments of the present invention. As shown in Figure 2, the dry gas conduit 14 can be an annular flow space concentric with the breathing gas conduit 12. In the embodiment shown in Figure 2, the breathing circuit tubing 11 can be formed by an inner tubing 20 that defines the breathing gas conduit 12, and the dry gas conduit 14 is formed by an outer sleeve or tubing 22 that surrounds the inner tubing 20, thereby defining the dry gas conduit 14 as an annular flow conduit 24 defined between the inner tubing 20 and the outer tubing 22. One or both of the inner and outer conduits can be formed by corrugated tubing. Alternatively, the inner tubing 20 can define the dry gas conduit 14, and the annular space 24 between the inner and outer tubings 20, 22 can be the breathing gas conduit 12. In the present invention, as further described below, a sufficient stretch of surface area is shared along the breathing circuit tubing 11 between the breathing gas conduit 12 and the dry gas conduit 14 so that a water and moisture permeation path is possible between the two conduits.

[0029] The present invention provides one or more embodiments that provide a moisture permeable pathway between the breathing gas conduit 12 and the dry gas conduit 14, reducing humidity in the breathing gas (B) flow and allowing moisture in the breathing gas (B) flow to be transferred to the dry gas stream (D). In FIG. 2, such a moisture permeable pathway (T) occurs between the more humid breathing gas in conduit 12 and the less humid dry gas in conduit 14. A user can increase or decrease the level of dry gas supplied to the conduits to manage or remove condensate that may transfer from the breathing gas (B) to the dry gas conduit. In this manner, moisture levels are reduced within the breathing gas flow and can be transferred to the dry gas stream. In one or more embodiments, such as that shown in FIG. 2, the breathing circuit tubing 11 includes a permeable portion (not shown) along some or all of the inner conduit 20 that is permeable to water vapor but not liquid water, such that the moisture permeable pathway (T) is provided by such a permeable portion of the breathing circuit tubing. The material comprising the permeable portion is water vapor permeable, allowing the passage of water vapor, as is well known to those skilled in the art. The permeable portion can form part or all of the wall of the breathing gas conduit 12, such as the inner tube 20, and can include a single layer or multiple outer layers of a water vapor permeable medium. In one embodiment, an additional wicking layer can be added to the permeable portion. In the embodiment shown in FIG. 2, the additional wicking layer can be disposed as an inner layer of the inner conduit 20 configured in contact with the breathing gas flow (B) inside the conduit. Such a wicking layer can be made of a wicking material that uses capillary action to adsorb and / or absorb both moisture and water in any phase, gas or liquid, while the outer layer of the water vapor permeable medium allows the passage of only water vapor, not liquid water.

[0030] Examples of wicking materials for the inner layer include knitted or nonwoven fabrics or textiles, synthetic fibers, polyester, polyester and polypropylene blends, nylon, polyethylene, or paper, and microfilament or microfiber materials such as Evolon® brand woven materials manufactured by Freudenberg & Co. KG. A specific example of a wicking material is a nonwoven material made of 70% polypropylene and 30% polyester. Another example of a wicking material is Evolon® brand woven materials with a weight of 60 or 80 grams per square meter. An example of a water vapor breathable medium for the outer layer is a Sympatex® brand water vapor permeable membrane made from polymers manufactured by Sympatex Technologies, including a monolithic hydrophilic polyester ester membrane with a thickness of 12 microns.

[0031] In another embodiment of the present invention, the breathing circuit tubing 11 includes one or more small openings or perforations (not shown) in the inner tubing 20 that allow liquid water to escape from the breathing gas conduit 12 to the dry gas conduit 14, such that another separate moisture transmission pathway T1 is provided by such perforations between the breathing gas stream (B) and the dry gas stream (D), as shown in FIG. 2.

[0032] Figure 3 is a schematic cross-sectional view of the apparatus of Figure 1 in accordance with one or more additional embodiments of the present invention. In Figure 3, a partition 30 is formed between the inner and outer tubes 20 and 22 in the annular space between the tubes, dividing the dry gas conduit into a first delivery conduit 32 for flow of dry gas (D1) from the first end of the apparatus 10 to the second end of the apparatus and a second return conduit 34 for flow of dry gas (D2) from the second end of the apparatus to the first end of the apparatus 10. In this manner, the dry gas stream can be reused, such as in a closed-loop system. One or more moisture permeable pathways can be defined between the gas flow conduit (B) and one or both of the dry gas conduits (D1, D2), including a permeable membrane incorporated in the inner tube 20, as described herein, or a series of small holes in the inner tube 20, as also described herein. The permeable membrane is permeable to water vapor but not to liquid water, and may include one or more layers, including a wicking layer, as described above.

[0033] Figure 4 is a schematic cross-sectional view of an apparatus 100 for incorporation into or as part of a breathing gas circuit according to one or more additional embodiments of the present invention. In Figure 4, the breathing circuit tubing 101 defines a breathing gas conduit 112 for flow of a breathing gas stream (B), the breathing gas having a first humidity level and a predetermined moisture level, and a dry gas conduit 114 is formed adjacent to at least a portion of the breathing gas conduit 112 for a dry gas stream (D), the dry gas stream being configured to have a second humidity level lower than the first humidity level. In Figure 4, a moisture permeable pathway (T2) is provided between the breathing gas conduit 112 and the dry gas conduit 114 to reduce humidity in the breathing gas stream (B) and allow moisture in the breathing gas stream (B) to be transferred to the dry gas stream (D). 4, the breathing gas conduit 112 and the dry gas conduit 114 share a common partition 130 having a moisture permeable pathway (T2) that may be provided by a permeable membrane incorporated into part or all of the partition 130 as described herein, or by a series of small holes in part or all of the partition 130 as also described herein. The permeable membrane is permeable to water vapor but not to liquid water, and may include one or more layers, including a wicking layer, as described above.

[0034] In one or more embodiments of the present invention, the dry gas conduit 14, 32, 34, 114 can be closed to the ambient air surrounding the device. The dry gas conduit can thus be configured to provide a dry gas stream at a humidity level significantly lower than that in the breathing gas conduit 12, 112. The outlet port for the dry gas conduit can further include a filter, and the dry gas flows out through the outlet port to the ambient environment surrounding the device. Such an outlet port can also be connected to a suction source. The input port for the dry gas conduit can include a flow or volume control element for the dry gas flow.

[0035] Thus, the present invention takes advantage of the difference in humidity or moisture content between the respective flows in the breathing gas conduit 12, 112 and the dry gas conduit 14, 32, 34, 114, thereby allowing for greater extraction or diffusion of moisture and humidity from the breathing gas stream to the dry gas stream, which is further assisted by the convective action of the dry gas stream along the common surface area shared between the breathing gas conduit 12, 112 and the dry gas conduit 14, 32, 34, 114, such as along the inner conduit 20 or common partition 130.

[0036] The present invention therefore provides a superior method of removing moisture or water vapor from a breathing circuit, better than water traps or other fluid dissipation or moisture removal devices known in the prior art. As a result of the disclosed device of the present invention, when the device is coupled to a breathing circuit, rainout or condensation on the breathing tube and water collection within the breathing circuit are significantly reduced. The present invention therefore allows for the removal of condensation that has collected on the inner wall of the breathing gas conduit, which is then delivered through the outer sleeve, which provides a dry gas conduit. The outer tube of the device can also serve to protect the inner tube from damage or rupture, which may be particularly susceptible to damage or rupture when a permeable membrane and / or small holes are incorporated, as described herein. Additional outer cover structures can be added to the device to provide reinforcement and rupture protection. The present invention therefore represents an improvement over the known prior art by providing the advantages of (a) reducing or eliminating user control of condensation levels within the breathing circuit, and / or (b) lowering humidity output from the expiratory limb of the breathing circuit, reducing condensate collection on the ventilator.

[0037] The many features and advantages of the present invention will become apparent from this specification, and it is, therefore, intended by the appended claims to cover all such features and advantages of the present invention that fall within the spirit and scope of the invention. Further, because numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and therefore, all suitable modifications and equivalents may be resorted to that fall within the scope of the invention. [Explanation of symbols]

[0038] 10 equipment 10A First End 10B Second end 11 Breathing circuit tubing body 12 Breathing gas conduit 14 Dry gas pipeline 20 Inner tube 22 Outer tube body 24 Annular flow conduit, annular space 40 input ports B. Breathing gas flow D Dry gas flow

Claims

1. 1. A moisture removal and condensation and humidity control device for a breathing circuit disposed between a patient and a ventilator, comprising: a breathing circuit tubing defining a breathing gas conduit for a flow of breathing gas having a first humidity level and a predetermined moisture or condensation level; a dry gas conduit adjacent at least a portion of the breathing gas conduit for a dry gas flow configured to have a second humidity level lower than the first humidity level; a moisture permeable pathway between the breathing gas conduit and the dry gas conduit, which reduces humidity in the breathing gas stream and allows moisture or condensate in the breathing gas stream to be transferred to the dry gas stream; 10. The apparatus, wherein the dry gas conduit is closed to the ambient air surrounding the apparatus.

2. 2. The device of claim 1, wherein the breathing circuit tubing includes a permeable portion that is permeable to water vapor but not to liquid water, such that the moisture permeable path is provided by such permeable portion of the breathing circuit tubing.

3. 3. The apparatus of claim 2, wherein the breathing circuit tubing is formed by an inner tubing defining the breathing gas conduit, the dry gas conduit is formed by an outer tubing surrounding the inner tubing, and the dry gas conduit is defined by an annular flow conduit defined between the inner and outer tubing.

4. the breathing circuit tubing is defined by an inner tubing defining the breathing gas conduit, the dry gas conduit being defined by an outer tubing surrounding the inner tubing, an annular space being defined between the inner tubing and the outer tubing; 3. The apparatus of claim 2, further comprising a partition formed between the inner and outer tubes in the annular space, the partition dividing the dry gas conduit into a first delivery conduit for flow of dry gas from a first end of the apparatus to a second end of the apparatus and a second return conduit for flow of dry gas from the second end of the apparatus to the first end of the apparatus.

5. 3. The device of claim 2, wherein the permeable portion of the breathing circuit tubing is a permeable membrane forming a portion of the breathing circuit tubing.

6. 6. The apparatus of claim 5, wherein the breathing circuit tubing is formed by an inner tubing defining the breathing gas conduit, the dry gas conduit is formed by an outer tubing surrounding the inner tubing, and the dry gas conduit is defined by an annular flow conduit defined between the inner and outer tubing.

7. the inhalation circuit tubing is defined by an inner tubing defining the breathing gas conduit, the dry gas conduit being defined by an outer tubing surrounding the inner tubing, an annular space being defined between the inner tubing and the outer tubing; 7. The apparatus of claim 6, further comprising a partition formed between the inner and outer tubes in the annular space, the partition dividing the dry gas conduit into a first delivery conduit for flow of dry gas from a first end of the apparatus to a second end of the apparatus and a second return conduit for flow of dry gas from the second end of the apparatus to the first end of the apparatus.

8. 2. The device of claim 1, wherein the breathing circuit tubing includes one or more small holes that allow liquid water to escape from the breathing gas conduit to the dry gas conduit, such that the moisture permeable pathway is provided by such one or more small holes in the breathing circuit tubing.

9. 9. The device of claim 8, wherein the inhalation circuit tubing is formed by an inner tubing defining the breathing gas conduit, the dry gas conduit is formed by an outer tubing surrounding the inner tubing, and the dry gas conduit is defined by an annular flow conduit defined between the inner tubing and the outer tubing.

10. the breathing circuit tubing is defined by an inner tubing defining the breathing gas conduit, the dry gas conduit being defined by an outer tubing surrounding the inner tubing, an annular space being defined between the inner tubing and the outer tubing; 10. The apparatus of claim 8, further comprising a partition formed between the inner and outer tubes in the annular space, the partition dividing the dry gas conduit into a first delivery conduit for flow of dry gas from a first end of the apparatus to a second end of the apparatus and a second return conduit for flow of dry gas from the second end of the apparatus to the first end of the apparatus.

11. 10. The device of claim 1, wherein the breathing circuit conduit and the dry gas conduit share a common partition having the moisture permeable pathway.

12. 12. The device of claim 11, wherein the common partition includes a permeable portion that is permeable to water vapor but not to liquid water, such permeable portion of the common partition providing the moisture permeable path.

13. 13. The device of claim 12, wherein the permeable portion of the breathing circuit tubing is a permeable membrane that forms a portion of the common partition.

14. 12. The apparatus of claim 11, wherein the common partition includes one or more small holes that allow liquid water to escape from the breathing gas conduit to the dry gas conduit, such that the moisture permeable path is provided by such one or more small holes in the common partition.

15. 10. The apparatus of claim 1, further comprising an outlet port for the dry gas conduit having a filter, the dry gas exiting the apparatus through the outlet port into an ambient environment surrounding the apparatus.

16. 10. The apparatus of claim 1, further comprising an input port for the dry gas conduit having a flow or volume control element for the dry gas flow.

17. 10. The apparatus of claim 1, further comprising an outlet port for the dry gas conduit connected to a suction source.

18. 1. A method for controlling moisture removal or condensation in a breathing circuit, comprising: Providing an apparatus according to claim 1; delivering or receiving breathing gas to or from a patient via the breathing circuit tubing; and supplying dry air through said dry gas conduit to remove moisture or liquid water condensate from said breathing gas conduit.

19. 20. The method of claim 18, further comprising monitoring one or more of the first and second humidity levels with a humidity sensor.

20. 20. The method of claim 19, wherein the breathing circuit tubing is the expiratory limb of a ventilator circuit.

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