Patent Description:
A breathing circuit delivers medical gas to a patient under pressure in a prescribed volume and breathing rate. The medical gas is often humidified by a humidifier located at or near the ventilator or respirator. The optimum respiratory circuit delivers <NUM>% RH medical gases to the patient while reducing the amount of humidity and subsequent condensate delivered back to the ventilator through the expiratory limb. Therefore, the humidified gas has to travel through all or most of the tubing and has time to cool. Cooling of the gas leads to rainout or condensation in the breathing tube and collection of water within the breathing circuit.

Several possible solutions to the problem of rainout have been developed. One such proposed solution is a heating wire provided along the length of the tube. The wire may be provided within the interior of the tubing or alternatively may be embedded along the interior of the tubing. The wire heats the humidified gas traveling through the tubing to prevent the gas from cooling, thus preventing the problem of water condensing out of the gas traveling through the breathing circuit. However, the manufacture of such heated wire respiratory circuits can be time consuming and costly.

Another possible solution, which eliminates the heated wire, is to provide a water collection device somewhere within the breathing circuit. A water collection apparatus is typically placed in the expiratory limb of the respiratory circuit to collect and allow for manual removal of excessive condensation prior to the gases entering the ventilator or respirator. It is known that excessive condensate entering a ventilator or respirator from the expiratory limb of a respiratory circuit can harm the device.

Most frequently, the water collection device is designed to trap the condensed water vapor in a removable container. When the container is removed, a valve can be actuated to create a gas tight seal for the breathing circuit. However, this type of water collection device has to be monitored and manually emptied, causing risk of patient or caregiver infection. The removal of moisture and condensation management is not automatic. Furthermore, the removable container is often only at one discrete point along the breathing circuit, and may need to be lowered to gravitationally collect liquid, which may be impractical.

Another possible solution is to provide a permeable membrane in the breathing circuit tubing which is permeable to water vapor but impermeable to liquid water, such that moisture inside the breathing gas flow inside such tubing dissipates to outside the tubing via such a membrane, and out to the ambient air surrounding the tubing. The problem with this solution is at least two-fold: first, such a thin walled membrane which is exposed to the surroundings can be easily punctured or damaged; and second, due to a relatively high humidity in the ambient conditions, there can be a limited humidity differential between the breathing gas flow and the ambient surroundings, so that the capacity for moisture to dissipate passively through the permeable membrane to ambient surroundings can also be limited.

<CIT> describes a conduit for a breathing circuit including a heater associated with a hydrophilic layer. The purpose of the heater is to evaporate any condensed liquid collecting in the conduit, which is first sucked up by the hydrophilic layer. The heated wick reduces the risk of collected water being passed to the patient and causing choking fits or discomfit. It is preferred that the heated wick lies freely in the conduit to settle at low points in the conduit where condensation may collect. <CIT> discloses a breathing circuit of the closed circuit type has improved means for removing water vapor to prevent condensation within the circuit. A dryer is placed in the breathing circuit, downstream of the CO2 absorber, for removing water vapor from the breathing gases, including that entrained in the breathing gases during passage through the CO2 absorber. The dryer may utilize a thermoelectric cooling element or a water vapor permeable membrane.

Accordingly, it is desirable to provide an improved apparatus for removing or decreasing water vapor, moisture, or condensate in a breathing circuit. It is further desirable that the improved apparatus for removing water vapor, moisture or condensate from the breathing tube, eliminates the need to monitor the device or to heat the exhalation limb of the breathing tube, and is not dependent on the positioning of the device, protects the device and its moisture and humidity transmission mechanism from damage, and increases its capacity for moisture removal and condensation management in a breathing circuit.

The foregoing needs are met, to a great extent, by the present technology, wherein a moisture removal and condensation and humidity management apparatus for a breathing circuit arranged between a patient and a ventilator is provided, comprising a breathing circuit tubing defining a breathing gas conduit for a flow of breathing gas therein, the breathing gas having a first humidity level and a level of moisture or condensate therein. A dry gas conduit is disposed adjacent at least a portion of the breathing gas conduit for a dry gas flow in said dry gas conduit, the dry gas flow being configured to have a second humidity level lower than the first humidity level. A moisture transmission pathway is included between the breathing gas conduit and the dry gas conduit, such that humidity in the flow of breathing gas is lowered and moisture or condensate in the flow of breathing gas is transferred to the dry gas flow. The dry gas conduit is closed to ambient air around the apparatus.

In one embodiment of the present disclosure, the breathing circuit tubing comprises a permeable portion which is permeable to water vapor but impermeable to liquid water, such that the moisture transmission pathway is provided by such permeable portion of the breathing circuit tubing.

In anotherembodiment of the present disclosure, the breathing circuit tubing is formed by an inner tube defining the breathing gas conduit, and the dry gas conduit is formed by an outer tube surrounding the inner tube, the dry gas conduit being defined by an annular flow conduit defined between the inner tube and outer tube.

In anotherembodiment of the present disclosure, the breathing circuit tubing is formed by an inner tube defining the breathing gas conduit, and the dry gas conduit is formed by an outer tube surrounding the inner tube, an annular space being defined between the inner tube and outer tube. Furthermore, a dividing wall is formed between the inner tube and outer tube in the annular space to divide 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.

In anotherembodiment of the present disclosure, the permeable portion of the breathing circuit tubing is a permeable membrane which forms a portion of said breathing circuit tubing.

In anotherembodiment of the present disclosure, the breathing circuit tubing comprises one or more perforations which permit drainage of liquid water from the breathing gas conduit to the dry gas conduit, such that the moisture transmission pathway is provided by such one or more perforations of the breathing circuit tubing.

In anotherembodiment of the present disclosure, the breathing circuit conduit and dry gas conduit share a common dividing wall, the common dividing wall having the moisture transmission pathway.

In anotherembodiment of the present disclosure, the common dividing wall comprises a permeable portion which is permeable to water vapor but impermeable to liquid water, such that the moisture transmission pathway is provided by such permeable portion of the common dividing wall.

In anotherembodiment of the present disclosure, the permeable portion of the breathing circuit tubing is a permeable membrane which forms a portion of said common dividing wall.

In anotherembodiment of the present disclosure, the common dividing wall comprises one or more perforations which permit drainage of liquid water from the breathing gas conduit to the dry gas conduit, such that the moisture transmission pathway is provided by such one or more perforations of the common dividing wall.

In anotherembodiment of the present disclosure, an exit port is provided on the apparatus for the dry gas conduit having a filter, the dry gas exiting via the exit port to the ambient environment surrounding the apparatus.

In anotherembodiment of the present disclosure, an input port is provided on the apparatus for the dry gas conduit having a flow or volumetric control element for the dry gas flow.

In anotherembodiment of the present disclosure, an exit port is provided on the apparatus for the dry gas conduit which is connected to a source of suction.

In anotheraspect of the present disclosure, method of removing moisture or controlling condensation in a breathing circuit is provided, comprising providing an apparatus as disclosed in any of the preceding recited embodiments of the present disclosure, The apparatus is configured and arranged to be disposed between a ventilator and a patient. Breathing gas is supplied via the breathing circuit tubing to a patient. And dry air is supplied through the 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 may be monitored using a humidity sensor. In one or more further embodiments, the breathing circuit tubing is an expiratory limb of a ventilator circuit.

There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional embodiments of the invention that will be described below and which form the subject matter of the claims appended hereto.

In this respect, before explaining at least one embodiment of the disclosure in detail, it is to be understood that the technology is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The technology is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.

The technology will now be described with reference to the drawing figures, in which like parts are referred to with like reference numerals throughout. One or more embodiments in accordance with the present technology provide a moisture removal and condensation and humidity management apparatus for a breathing circuit to rapidly remove water vapor or condensate from a humidified medical gas traveling through a breathing circuit between a ventilator and a patient or the patient and the ventilator. As used herein, a "breathing circuit" or "breathing gas circuit" is any arrangement of tubing or conduits which carries gases to be administered to and from a patient, such as from a ventilator, and which may include additional accessories or devices attached to it. Such "breathing gases" may include oxygen, air or any component thereof, and are configured for absorbing high levels of moisture and/or being humidified prior to administration to a patient, or during administration to a patient, suitable for medical applications.

<FIG> is a schematic view illustrating an apparatus incorporated into or as part of a breathing gas circuit in accordance with one or more embodiments of the present disclosure. A moisture removal and condensation and humidity management apparatus <NUM> for a breathing circuit includes a section or length of breathing circuit tubing <NUM> defining a breathing gas conduit <NUM> for a flow (B) of breathing gas therein. The breathing gas flows from a first, upstream end 10A of the device <NUM>, through the conduit <NUM> defined within device <NUM>, to a second, downstream end 10B of the device <NUM>. The breathing gas is configured to have a first humidity level and a level of moisture therein, which may be calibrated based on the needs of the patient. In one embodiment such a length of breathing circuit tubing <NUM> may be in an expiratory limb of a breathing circuit, such as, for example, somewhere between a patient and a ventilator. In the device <NUM>, a dry gas conduit <NUM> is defined adjacent at least a portion of the breathing gas conduit <NUM> between the first end 10A and second end 10B, for a dry gas flow (D) therein. The dry gas flow (D) is configured to have a second humidity level which is lower than the first humidity level within the breathing gas conduit (B). A dry gas flow is coupled from a dry gas source (not shown) to one or more input ports <NUM> which feed the dry gas flow (D) into the dry gas conduit <NUM>, which then flows substantially parallel to, or around the breathing gas conduit <NUM>.

<FIG> a schematic cross-sectional view illustrating the apparatus of <FIG> in one or more embodiments of the present disclosure. As shown in <FIG>, the dry gas conduit <NUM> may be an annular flow space which is concentric with breathing gas conduit <NUM>. In the embodiment shown in <FIG>, the breathing circuit tubing <NUM> may be formed by an inner tube <NUM> defining the breathing gas conduit <NUM>, and the dry gas conduit <NUM> is formed by an outer sleeve or tube <NUM> surrounding the inner tube <NUM>, the dry gas conduit <NUM> thereby being defined as an annular flow conduit <NUM> defined between the inner tube <NUM> and outer tube <NUM>. One, or both, of the inner and outer conduits may be formed by corrugated tubing. Alternatively, the inner tube <NUM> could define the dry gas conduit <NUM> and the annular space <NUM> between the inner and outer tubes <NUM>, <NUM> could be the breathing gas conduit <NUM>. In the present technology, a sufficient stretch of surface area is shared along the breathing circuit tubing <NUM> between the breathing gas conduit <NUM> and dry gas conduit <NUM> such that a moisture and humidity transmission pathway is enabled between the two conduits, as further described below.

The present technology provides one or more embodiments which provide a moisture transmission pathway between the breathing gas conduit <NUM> and the dry gas conduit <NUM>, such that humidity in the flow of breathing gas (B) is lowered and moisture in the flow of breathing gas (B) is transferred to the dry gas flow (D). In <FIG>, such a moisture transmission pathway (T) occurs between the higher humidity breathing gases in conduit <NUM> and the lower humidity dry gas flow in conduit <NUM>. A user can increase or decrease the level of dry gas supplied to the circuit to manage or remove the condensate which may be transmitted from the breathing gas (B) to the dry gas conduit. The moisture level thus may be reduced from within the breathing gas flow and transferred to the dry gas flow. In one or more embodiments, such as shown in <FIG>, the breathing circuit tubing <NUM> comprises a permeable portion (not shown) along part or all of the inner conduit <NUM> is provided, which is permeable to water vapor but impermeable to liquid water, such that the moisture transmission pathway (T) is provided by such permeable portion of the breathing circuit tubing. The materials comprising the permeable portion are water vapor breathable and allow passage of water vapor, as is well known to those of ordinary skill in the art. The permeable portion may form some or all of the walls of the breathing gas conduit <NUM>, such as inner tube <NUM>, and may include a single, or composite outer, layer of water vapor breathable medium. In one embodiment, an additional wicking layer may be added to the permeable portion. In the embodiment shown in <FIG>, the additional wicking layer may be disposed as an inner layer of inner conduit <NUM>, configured to be in contact with breathing gas flow (B) inside said conduit. Such a wicking layer may be made of wicking material which allows for adsorption and/or absorption of both moisture and water in any phase, gas or liquid, using a capillary action, while the outer layer of water vapor breathable medium permits the passage of water vapor only and not liquid water.

Examples of wicking material in the inner layer are a knit or non-woven cloth or fabric, and can be synthetic and made of polyester, polyester and polypropylene blends, nylon, polyethylene or paper, and can be microfilaments or microfiber material such as Evolon® brand fabric material made by Freudenberg & Co. A particular example of wicking material would be a non-woven material of <NUM>% polypropylene and <NUM>% polyester. Another example of the wicking material can be Evolon® brand fabric material having a weight of <NUM> or <NUM> grams per square meter. Examples of the outer layer of water vapor breathable medium are Sympatex® brand water vapor permeable membranes made of polymers made by Sympatex Technologies, including monolithic hydrophilic polyester ester membrane, including, as one example, a <NUM> micron thick membrane.

In another embodiment of the present disclosure, the breathing circuit tubing <NUM> comprises one or more small openings or perforations (not shown) in inner tube <NUM> which permit drainage of liquid water from the breathing gas conduit <NUM> to the dry gas conduit <NUM>, such that another, different, moisture transmission pathway T1 is provided by such one or more perforations between the breathing gas flow (B) and dry gas flow (D), such as shown in <FIG>.

<FIG> a schematic cross-sectional view illustrating the apparatus of <FIG> in one or more additional embodiments of the present disclosure, In <FIG>, a dividing wall <NUM> is formed between the inner tube <NUM> and outer tube <NUM> in the annular space between said tubes to divide the dry gas conduit into a first, delivery conduit <NUM> for flow of dry gas (D1) from a first end of the apparatus <NUM> to a second end of the apparatus, and a second, return conduit <NUM> for flow of dry gas (D2) from the second end of the apparatus to the first end of the apparatus <NUM>. In this way, the dry gas flow may be re-used, such as, for example, in a closed loop system. One or more moisture transmission pathways may be defined between breathing gas flow conduit (B) and one or both of dry gas conduits (D1, D2), including a permeable membrane incorporated into inner tube <NUM> as described herein, or a series of perforations in the inner tube <NUM>, as also described herein. The permeable membrane is permeable to water vapor but impermeable to liquid water and may include one or more layers, including a wicking layer, as described above.

<FIG> is a schematic cross sectional view of an apparatus <NUM> incorporated into or as part of a breathing gas circuit in accordance with one or more additional embodiments of the present invention. In <FIG>, a breathing circuit tubing <NUM> defines a breathing gas conduit <NUM> for a flow of breathing gas flow (B) therein, said breathing gas having a first humidity level and a level of moisture therein, and a dry gas conduit <NUM> is formed adjacent at least a portion of the breathing gas conduit112 for a dry gas flow (D) therein, said dry gas flow configured to have a second humidity level lower than the first humidity level. In <FIG>, a moisture transmission pathway (T2) is provided between the breathing gas conduit <NUM> and the dry gas conduit <NUM>, such that humidity in the flow of breathing gas (B) is lowered and moisture in the flow of breathing gas (B) is transferred to the dry gas flow (D). In <FIG>, the breathing gas conduit <NUM> and dry gas conduit <NUM> share a common dividing wall <NUM>, the common dividing wall <NUM> having the moisture transmission pathway (T2), which may be provided by a permeable membrane incorporated into part or all of the dividing wall <NUM>, as described herein, or a series of perforations in part or all of the dividing wall <NUM>, as also described herein. The permeable membrane is permeable to water vapor but impermeable to liquid water and may include one or more layers, including a wicking layer, as described above.

Claim 1:
A moisture removal apparatus (<NUM>, <NUM>) comprising:
a breathing circuit tubing (<NUM>, <NUM>) including:
a breathing gas conduit (<NUM>, <NUM>) that directs a flow of breathing gas in a first direction from a first end (10A) of the apparatus (<NUM>, <NUM>) to a second end (10B) of the apparatus (<NUM>, <NUM>); and
a dry gas conduit (<NUM>) that directs a first dry gas flow; and
a moisture transmission pathway between the breathing gas conduit (<NUM>, <NUM>) and the dry gas conduit (<NUM>, <NUM>) that lowers the humidity of the breathing gas by transferring the humidity to the first dry gas flow; and
wherein at least one of:
the dry gas conduit (<NUM>, <NUM>) directs the first dry gas flow in the first direction;
the moisture removal apparatus (<NUM>, <NUM>) includes a return conduit (<NUM>) that directs a second dry gas flow in a second direction from the second end (10B) of the apparatus (<NUM>, <NUM>) to the first end (10A) of the apparatus (<NUM>, <NUM>); or
the moisture removal apparatus (<NUM>, <NUM>) includes a dividing wall (<NUM>) that is flat, the dividing wall (<NUM>) dividing the breathing circuit tube (<NUM>) into the breathing gas conduit (<NUM>) and the dry gas conduit (<NUM>), the dividing wall (<NUM>) including a permeable portion that defines the moisture transmission pathway, the moisture transmission pathway being permeable to water vapor.