Patent Description:
In anesthesia and in intensive care, the condition of a patient is often monitored by analyzing the gas inhaled and exhaled by the patient for its content. For this reason, either a small portion of the respiratory gas is delivered to a gas analyzer or the gas analyzer is directly connected to the respiratory circuit. In a non-dispersive infrared (NDIR) gas analyzer, the measurement is based on the absorption of infrared (IR) radiation in the gas sample. A radiation source directs a beam of infrared radiation through a measuring chamber to a radiation detector whose output signal depends on the strength of the absorption of the radiation in the sample gas.

The radiation source typically comprises an electrically heated filament or surface area and radiation collecting optics and emits radiation within a spectral region. The gas sample to be analyzed is fed through the measuring chamber. The measuring chamber can be a tubular space, for example, with inlet and outlet for the sample gas and provided with windows that are transparent at the measurement IR wavelength and permit transmission of the IR wavelength through the chamber. Radiation is absorbed by the gas sample when passing through the measuring chamber, and thus the amount of the measurement IR wavelength that is transmitted through the chamber (i.e., from one window to the other) is indicative of certain gas component amount(s) in the gas sample.

The radiation detector generates an electrical signal that depends on the radiation power falling on its sensitive area. The detector type in a gas analyzer depends on its measurement wavelength. For measurement within a broad spectral range, a thermal detector is convenient because its sensitivity only depends on the efficiency of the conversion of radiation to heat. To make the detector's output signal sensitive to a certain gas component, the wavelength band of the radiation coming to the detector is selected so that the gas component absorbs radiation within it. This selection is made using an optical bandpass filter whose bandwidth may be, for example, <NUM>%-<NUM>% of the center wavelength.

Gas analyzers can be configured to measure different gas components. The absorption of the gas sample is measured at a wavelength band selected to match the absorption spectra of the gas component(s) of interest. Measurement of more than one gas component can be accomplished by using one radiation detector and by changing the optical bandpass filters on the optical path in succession. It is also possible to use several radiation detectors, combined with corresponding bandpass filters. Different respiratory gases have widely spaced wavelength regions of absorption. Carbon dioxide and nitrous oxide can be measured between <NUM> and <NUM> whereas anesthetic agents absorb in the <NUM> to <NUM>,<NUM> region.

<CIT> describes an NDIR sensor, sampling method and system for breath analysis. <CIT> describes an airway adapter for monitoring constituents of a patient's breath. <CIT> describes a gas flow system, adaptor, and method. <CIT> describes a gas flow channel device for measuring human respiration. <CIT> describes an airway adaptor and respiratory flow rate sensor. <CIT> describes an airway adaptor. <CIT> describes a breathing mask for ventilating a patient and gas analyzer for respiratory gas measurement.

The present invention provides an airway adaptor as defined in claim <NUM>. Further preferred embodiment of the present invention are defined in the dependent claims.

In one embodiment, an airway adaptor providing a measurement chamber for gas measurement by a mainstream gas analyzer includes a body having a first end and a second end and configured to connect in a ventilation circuit carrying ventilation gas to and from a patient. The body forms a primary path that includes the measurement chamber and is configured to allow ventilation gas to pass between the first end and the second end and at least one secondary path separated from the primary path and located on an outer perimeter of the primary path. The at least one secondary path is configured to contain liquid away from the measurement chamber.

One embodiment of a neonatal airway adaptor providing a measurement chamber for gas measurement within the neonatal ventilation circuit by a mainstream gas analyzer has a body with a first end and a second end and configured to connect in the neonatal ventilation circuit carrying ventilation gas to and from a neonate patient. The body forms a primary path that includes the measurement chamber and is configured to allow the ventilation gas to pass between the first end and the second end, and at least one secondary path located on an outer perimeter of the primary path. The at least one secondary path is separated from the primary path and configured such that a flow rate through the secondary path is less than a flow rate through the primary path. For example, a volume of the secondary path may not exceed <NUM>% of the volume of the primary path. The at least one secondary path is configured to contain liquid away from the measurement chamber.

Various other features, objects, and advantages of the disclosure will be made apparent from the following description taken together with the drawings.

The present inventor has recognized that a problem with existing airway adaptors, or cuvettes, for facilitating gas measurement by a mainstream gas analyzer is that liquids and vapors collect inside the measurement chamber of the airway adaptor. The liquids accumulate on the windows of the airway adaptor through which the gas analyzer makes measurements such that accurate measurements cannot be performed by the gas analyzer. This is particularly a problem for neonatal airway adaptors where the measurement chamber and connection path through the neonatal airway adaptor has a smaller volume than for an adult airway adaptor to reduce the dead space in the neonatal ventilation circuit. In neonatal airway adaptors, the optical window size is typically the same size as used for adult cuvettes and thus the windows occupy a larger relative portion on the side of the measurement chamber and thus accumulation of liquids in the measurement chamber quickly and significantly impacts performance of gas measurements by the gas analyzer. Given the smaller volume and the proportionally larger window size, problems with liquid accumulation in neonatal gas measurement applications are particularly prevalent. A greater proportion of liquid accumulated in the neonatal ventilation circuit tends to hit the neonatal airway adaptor windows than in the adult airway adaptors and liquid in the measurement path, such as the path of the infrared transmission, attenuates the radiation and prevent accurate gas measurement.

In view of the foregoing problems and challenges in the relevant art, the inventor developed the disclosed airway adaptor having a separate path for accumulated liquid that is configured to contain accumulated liquids away from the primary path. The disclosed airway adaptor has a primary path that includes the measurement chamber and is configured to allow the ventilation gas to pass through the airway adaptor from end to end. The airway adaptor includes at least one secondary path separated from the primary path, wherein the at least one secondary path is configured to contain liquid away from the primary path to isolate as much of the accumulated liquid as possible away from the measurement chamber and particularly optical windows. Thus, the one or more secondary paths are positioned such that most, or as much as possible, of the liquid flows through the secondary path, or is otherwise contained in the secondary path away from the measurement chamber.

In various embodiments, the secondary path may extend the full length of the airway adaptor between the first end and the second end or may be configured such that the secondary path only extends a portion of the length of the airway adaptor. The at least one secondary path is located along an outer perimeter of the primary path. For example, the at least one secondary path may be on a lower half or bottom side of the body below the primary path where liquid has a greater tendency to accumulate due to gravity. In one embodiment, the secondary path may be centered below the primary path on a bottom side of the body. In another embodiment, multiple secondary paths may be distributed on a lower half of the outer perimeter of the primary path.

The system may be configured such that the airway adaptor is positioned at an angle, such as at an angle away from the patient where the end of the airway adaptor on the patient side is higher than the end of the airway adaptor on the ventilator side. In such an embodiment, system may be configured such that the liquid is channeled out of the second end, the ventilator end, of the airway adaptor away from the patient. Alternatively, in embodiments where the airway adaptor is in a horizontal position, liquid may accumulate and be maintained in the secondary path and remain there. If the liquid accumulation volume significant, it may completely fill and block the secondary path and may even accumulate above the secondary path entrance and in the primary path. However, a substantial portion of the liquids are still maintained in the secondary path away from the primary path, and particularly away from the measurement chamber.

The secondary path, or group of secondary paths, may be configured so that it does not significantly impact the dead space created by the airway adaptor. This is particularly important for neonatal applications where minimizing dead space is important given the small lung size and breath volume of the neonatal patient. Thus, the at least one secondary path may be configured such that it restricts the flow rate therethrough to minimize dead space while still enabling collection of liquid in the secondary path. The collective flow rate through the at least one secondary path may be configured such that it is <NUM>% or less of the flow rate through the primary path. In other embodiments, the flow rate through the one or more secondary paths does not exceed <NUM>% of the flow rate through the primary path. In still other embodiments, the total flow rate through the secondary path does not exceed <NUM>% of the flow rate through the primary path. In still other embodiments, the total flow rate through the at least one secondary path does not exceed <NUM>% of the flow rate through the primary path.

To reduce flow rate through of the secondary path, and thus to reduce dead space created by the secondary path, the secondary path may have a narrowed section comprising a portion of the length of the secondary path which has a smaller cross-sectional area than the cross-sectional area of other sections of the secondary path. For example, the narrowed section may be in the center portion of the body of the airway adaptor such that the narrowed section is approximately centered along the length of the secondary path. In certain examples, the narrowed section of the secondary path may be aligned with and beneath the windows. In other embodiments the narrowed section may be elsewhere along the secondary path closer to one end.

Exemplary embodiments of the disclosed airway adaptor and system comprising the disclosed airway adaptor are shown in <FIG> and variously discussed herein. The disclosed respiratory gas sensor system <NUM> includes an airway adaptor <NUM>, or cuvette, with a secondary path configured to contain liquids that have accumulated in that area of the ventilation circuit away from the primary path where the gas analyzer <NUM> is conducting measurements. The airway adaptor <NUM> has body <NUM> with a top side <NUM> and a bottom side <NUM>. The system <NUM> is generally configured such that the bottom side <NUM> is below the top side <NUM> such that gravity forces liquids downward toward the bottom side <NUM>. The body <NUM> has a first end <NUM> and a second end <NUM>, each end configured to attach to a respective element within the ventilation circuit. In the depicted example, the first end <NUM> on the patient-side of the body <NUM> is configured to connect to an endotracheal tube <NUM> and the second end <NUM> is configured to connect to spirometry adaptor <NUM> and/or to a Y-piece <NUM> that circulates gas to and from the ventilator <NUM>.

The gas analyzer <NUM> may removably connect to the airway adaptor <NUM>, such as by clips on the airway adaptor <NUM> configured to create a friction connection thereto. The top side <NUM> may be configured to connect to the gas analyzer <NUM>. In the depicted examples, the adaptor body <NUM> includes two opposing clips <NUM> (<FIG>, <FIG>, and <FIG>) configured to removably connect to the airway adaptor, which is positioned over the top side <NUM> of the center portion <NUM> of the airway adaptor <NUM> and extends over the sides of the center portion <NUM> so as to conduct gas measurements through the windows <NUM>.

As exemplified in <FIG>, a ventilation circuit with a medical gas analyzer is shown. A patient <NUM> is connected to a ventilator <NUM> using an endotracheal tube <NUM>, a Y-piece <NUM>, an inspiratory limb <NUM>, and an expiratory limb <NUM>. A gas analyzer <NUM> is connected to an airway adaptor <NUM>, which is connected to the intubation tube. The gas analyzer <NUM> is a mainstream gas analyzer measuring gases flowing between the ventilator <NUM> and the patient <NUM> without withdrawing samples of the gas to a separate gas analyzer.

The analyzer shown in <FIG> is electrically connected via cable <NUM> to the patient monitor <NUM>. The gas component measured may be carbon dioxide (CO<NUM>), nitrous oxide (N<NUM>O), or any of the volatile anesthetic agents-e.g., halothane, enflurane, isoflurane, desflurane, and sevoflurane. Additionally, there may be a spirometry adaptor <NUM> for measuring the gas flow in the respiratory circuit. In this example, the sensor <NUM> is located at the distal end of two pressure relying tubes <NUM>. The spirometry sensor may be separately connected as in <FIG> or it can be integrated into the mainstream gas analyzer.

In <FIG>, a different view of the gas analyzer <NUM> is depicted to better show the components within the gas analyzer and construction of the adaptor <NUM>, which may be disposable or reusable. It is provided with at least one optical window <NUM> for allowing the IR radiation to be absorbed by the gas components in the measuring chamber between the optical windows. Typically, there are two IR-transmitting optical windows <NUM>. IR emitter <NUM> is located on one side of the adaptor and one or more detector(s) <NUM> on the opposite side in such a way that the IR radiation is directed from the emitter <NUM>, through the windows <NUM> and to the detector(s) <NUM>.

The signals, or radiation measurement data, from each detector <NUM> gets amplified and modified to determine the concentration of the respiratory gas component to be measured. As mentioned above, the measured respiratory gas components can be any IR-absorbing component, such as carbon dioxide, nitrous oxide, or different volatile anesthetic agents. All these gases absorb IR radiation within some specific wavelength region and this region is selected (i.e., the measurement wavelength), such as using a narrowband filter, and the provided to the detector <NUM>.

<FIG> depict exemplary airway adaptors <NUM>, <NUM>', and <NUM> exemplifying embodiments and features of the disclosed airway adaptor with a secondary path. <FIG> depict a first exemplary neonatal adaptor <NUM>, and <FIG> depict a second exemplary neonatal adaptor <NUM>'. <FIG> depict an exemplary airway adaptor <NUM> configured for an adult application.

<FIG> depicts a perpendicular cross-sectional view through a center portion of the airway adaptor and <FIG> depicts a cross-sectional view along the length of the neonatal airway adaptor <NUM>. The neonatal airway adaptor <NUM> comprises a body <NUM>, such as formed of a molded plastic. The body <NUM> has a first end <NUM>, such as configured to connect to an endotracheal tube <NUM> or some other patient interface, and a second end <NUM>, such as configured to connect to a Y-piece <NUM>, and additional measurement section or some other element forming the neonatal ventilation circuit. The body <NUM> forms a patient end portion <NUM> from the first end <NUM> to a center portion <NUM>, and a ventilator end portion <NUM> between the center portion and second end <NUM>. The measurement chamber is in the center portion <NUM>, which has two windows <NUM> positioned on opposing sides of the measurement chamber and configured to allow gas measurement by the mainstream gas analyzer <NUM>. Gas analyzer <NUM> fits over the top side <NUM> of the center portion <NUM> and conducts gas measurements through windows <NUM>. The airway adaptor <NUM> is configured to receive and connect to the gas analyzer <NUM> on the topside <NUM> via clips <NUM>, like the arrangement shown in <FIG>.

The neonatal airway adaptor <NUM> provides a primary path <NUM> that includes a measurement chamber in the center section <NUM> configured to allow ventilation gas to pass through the measurement chamber between the first end <NUM> and the second end <NUM> of the airway adaptor body <NUM>. The primary path <NUM> of the neonatal adaptor <NUM> has a smaller volume than a primary path for an adult airway adaptor and is configured to restrict flow through the secondary path so as to reduce the added dead space in the neonatal ventilation circuit. For example, the primary path <NUM> in the neonatal embodiment may be narrower than that of the adult embodiment such that it has a lesser volume and flow rate in the primary path of the neonatal airway adaptor given the smaller lung capacity of the neonate compared to an adult.

The secondary path <NUM> is positioned below the primary path <NUM> toward the bottom side <NUM> of the body <NUM>. In the depicted example, one secondary path is provided. In other embodiments, two or more secondary paths may be included, such as arranged on an outer perimeter of the primary path <NUM>. For example, two or more secondary paths may be arranged around the primary path <NUM>, such as arranged around a lower half of the perimeter of the primary path <NUM> and below the windows <NUM>.

The secondary path <NUM> is configured to restrict flow rate compared to that of the primary path <NUM>. For example, the peak flow rate through the primary path <NUM> in the neonatal adaptor <NUM> may be tens of milliliter per second (mL/s), which is a common flow rate for neonatal airway adaptors. In such an example, the total flow rate through the secondary path <NUM> is less than <NUM>% of the primary path flow rate. In certain examples, the flow rate through the secondary path <NUM> may not exceed <NUM>%. In still further examples, the secondary path flow rate may be even more restricted, such as not exceeding <NUM>%, <NUM>%, or even <NUM>%of the primary path flow rate. As described above, reducing the flow rate through the secondary path <NUM> is necessary to reduce the dead space created by the neonatal airway adaptor <NUM>, and thus narrowing the secondary path significantly, may be necessary depending on the neonatal application, such as the size and development stage of the neonate. Only that part of the volume of the secondary path through which gas is traveling is calculated to be dead space volume. The volume of the portion of the secondary path that is not ventilated, i.e., has no flow pathway through the adaptor108, is not considered to be a part of the dead space. Thus, when flow rate through the secondary path is small due to a restriction in the secondary pathway, the amount of added dead space is also small.

Where two or more secondary paths are included, the neonatal airway adaptor <NUM> may be configured so that the total flow rate through the secondary paths does not exceed the threshold relative flow rate through the primary path, which may be any of the forgoing examples as appropriate for the particular neonatal application and the constraints on the dead space.

Further, the one or more secondary paths <NUM> may be configured such that liquids accumulate and thereby reduce the available dead space. Namely, liquids accumulated in the secondary pathway <NUM> reduce the volume occupied by gasses, including the patient's exhalation gases, and thus the dead space is reduced over the period of use.

The depicted secondary path <NUM> includes a narrowed section <NUM>. The narrowed section <NUM> extends for at least a portion of the length of the secondary path <NUM> and is configured to restrict flow rate therethrough. In the depicted example, the narrowed section <NUM> is positioned in the center portion <NUM> and is centered along the secondary path <NUM> below the windows <NUM>. The narrowed section <NUM> has a smaller cross-sectional area than portions of the secondary path <NUM> that are not in the narrowed section. The narrowed section may have a consistent cross-sectional area or may have a tapered form where the cross-sectional area progressively changes-e.g., diameter MD of the secondary path <NUM> progressively decreases and/or increases along the length BL.

In the example at <FIG>, the narrowed section <NUM> includes three subsections, including two tapered subsections. The narrowed section <NUM> has a first tapered subsection having length TL1 and a second tapered subsection having length TL2 on either side of a narrowed middle subsection having length NL. The narrowed section NL is formed by a ledge <NUM> extending upward from the bottom wall or side of the secondary path <NUM> and provides a consistent, further narrowed cross-sectional area in the center of the length of the secondary path <NUM>, which is below the windows <NUM>.

In various embodiments, the ledge <NUM> may have a length NL forming the narrowed middle subsection that is at least as long as the diameter WD of the windows <NUM>. In certain embodiments, the length NL may be <NUM> times the window diameter WD. For example, where the window diameter WD is <NUM>, the length NL may be <NUM>. In such an embodiment, the diameter MD of the narrowed middle subsection NL may be <NUM>. The restriction may be set based on the desired flow relationship between primary and secondary path.

The ledge <NUM> forming the narrowed middle subsection NL may extend from the bottom side of the secondary path, the top side of the secondary path, or from the surrounding perimeter such as the cross-sectional area of the narrowed middle subsection NL is circular as shown in <FIG>.

The cross-sectional areas of each tapered section TL1 and TL2 progressively decrease toward the center up to the ledge <NUM>. In the depicted example, the ledge <NUM> and the tapered edges in the tapered section TL1 and TL2 extend from the bottom side of the secondary path <NUM>. However, in other embodiments the ledge and tapered edges extend downward from a top side of the secondary path <NUM>, such as from the bottom of the divider <NUM>. In still other examples, the narrowed section may be created by protrusions from both the top and bottom sides, and/or around the entire perimeter of the secondary path <NUM>. For example, the narrowed section <NUM> may have a circular cross-section across its length.

In one embodiment, the cross-sectional area may consistently decrease such that there is no ledge <NUM> and instead the tapered sections TL1 and TL2 extend all the way to the center. For example, the smallest cross-sectional area may be beneath the windows <NUM> at the approximate center of the length BL of the neonatal airway adaptor <NUM>.

In still other embodiments, the tapering may be eliminated and the ledge <NUM> may extend the full length of the narrowed section <NUM>, which may be longer or shorter than the center section <NUM>.

In the depicted example, the narrowed section <NUM> extends substantially the length of the center portion <NUM> of the airway adaptor <NUM>. The narrowed section <NUM> is centered under the windows <NUM>. In other embodiments, the narrowed section <NUM> may extend for only a portion of the center portion <NUM>, such as a portion centered under the windows <NUM>. For example, the narrowed section <NUM> may be at least as long as the window diameters WD, and in some embodiments may be at least <NUM> times the window diameter WD.

In other embodiments, the narrowed section <NUM> may be longer than the center portion <NUM>, such as extending into one or both of the patient end portion <NUM> and the ventilator end portion <NUM>. For example, the tapered sections TL1 and TL2 may extend further outward towards the ends <NUM> and <NUM>. In certain embodiments, the tapered sections TL1 and TL2 may extend all the way to the ends <NUM> and <NUM>. In such an embodiment, the secondary path <NUM> may have a circular cross-section across its length, and the cross-section of the circle may progressively decrease toward the center between the ends <NUM>, <NUM>.

In the neonatal airway adaptor <NUM> depicted in <FIG>, the secondary path <NUM> extends along the entire length BL of the airway adaptor <NUM> between the first end <NUM> and the second end <NUM>. The secondary path <NUM> is divided and separated from the primary path <NUM> by divider <NUM>. In the depicted example, the divider <NUM> extends the length BL between the first end <NUM> and the second end <NUM>. However, in other embodiments, the divider <NUM> may extend only a portion of the length BL. For certain applications, and particularly for neonatal applications, it is desirable for the divider <NUM> to extend at least the length of the center portion <NUM>, and in some applications extend beyond the center portion <NUM> and into each of the patient end portion <NUM> and the ventilator end portion <NUM>. For example, the divider <NUM>, which separates the secondary path <NUM> form the primary path <NUM>, may be at least <NUM>% of the length BL of the airway adaptor <NUM>. In other embodiments, the divider <NUM> may be at least <NUM>% of the length BL of the airway adaptor <NUM>.

<FIG> depict another exemplary neonatal airway adaptor <NUM>'. <FIG> is an end view of the adaptor <NUM>' showing the first end <NUM> configured to connect to the patient interface, such as the endotracheal tube <NUM>. <FIG> is a perspective of a lengthwise cross-sectional view of the adaptor <NUM>'. In the depicted embodiment, the secondary path has a cylindrical narrowed section <NUM>' extending the length of the center portion <NUM>. The narrowed section <NUM>' has a consistent cross-sectional area except for a further narrowed subsection created by the ledge <NUM>'. The divider <NUM>' separating the primary path <NUM>' from the secondary path <NUM>' has a curved notch <NUM> at the first end which is configured to guide liquids exiting the patient airway into the secondary path <NUM>' and away from the primary path <NUM>'.

<FIG> depict an exemplary airway adaptor <NUM> such as may be appropriate for ventilation measurement in an adult patient. <FIG> depicts a perpendicular cross-sectional view of the airway adaptor <NUM> and <FIG> depicts a longitudinal cross-sectional view of the airway adaptor <NUM>. In this example, the divider <NUM> extends only a portion of the length BL' of the airway adaptor <NUM>. Thus, the secondary path <NUM> extends only a portion of the length BL' of the airway adaptor <NUM>. In the depicted example, the divider <NUM> extends approximately the length of the center portion <NUM> and does not substantially extend into the patient end portion <NUM> or the ventilator end portion <NUM>.

The adult airway adaptor <NUM> has a larger volume primary path <NUM> compared to the neonatal airway adaptor <NUM>. The primary path <NUM> is defined by the body <NUM> and extends between the first end <NUM> and the second end <NUM> of the airway adaptor <NUM>. The airway adaptor <NUM> comprises a center portion <NUM> providing the measurement chamber and configured to receive the gas analyzer <NUM> and incudes clips <NUM> on the top side <NUM> of the body <NUM>. The gas analyzer <NUM> fits over the top side <NUM> of the center portion <NUM> and conducts measurements through windows <NUM>, as described above. The secondary path <NUM> is situated toward the bottom side <NUM> of the airway adaptor <NUM> below the primary path <NUM>.

The secondary path <NUM> comprises only a portion of the length BL' of the airway adaptor <NUM>, which in the example extends across the center portion <NUM> housing the measurement chamber. The divider <NUM> likewise extends only a portion of the length BL' and through the center portion <NUM>. Thereby, the divider <NUM> creates the secondary path <NUM> to contain liquids away from the measurement chamber in the center portion <NUM>, and particularly away from the windows <NUM>. In other embodiments, the divider <NUM> may extend further along the length BL', such as extending the secondary path <NUM> partially or totally across the lengths of each of the patient end portion <NUM> and the ventilator end portion <NUM>.

Claim 1:
An airway adaptor (<NUM>, <NUM>, <NUM>') providing a measurement chamber for gas measurement by a mainstream gas analyzer (<NUM>), the airway adaptor comprising:
a body (<NUM>, <NUM>) having a first end (<NUM>, <NUM>) and a second end (<NUM>, <NUM>) and configured to connect in a ventilation circuit carrying ventilation gas to and from a patient (<NUM>);
a primary path (<NUM>, <NUM>') that includes the measurement chamber and is configured to allow the ventilation gas to pass between the first end to the second end;
at least one secondary path (<NUM>, <NUM>') separated from the primary path and located on an outer perimeter of the primary path;
wherein the at least one secondary path is configured to contain liquid away from the measurement chamber,
wherein the at least one secondary path has a narrowed section (<NUM>, <NUM>') comprising a portion of a length of the secondary path, the narrowed section being configured to restrict flow rate therethrough.