PATCH CABLE, RESPIRATORY ADAPTER, AND RESPIRATORY GAS DETECTION SYSTEM FOR DETECTING CONCENTRATION OF RESPIRATORY GAS - Patent application

Abstract

The present invention relates to a patch cable for connecting a respiratory module 103 to a respiratory adapter 101, for example, which is part of a capnography system. The patch cable 110 includes: a) a module connector 113; b) an adapter connector 114 including a photodetector; c) a light guide; and d) an electrical cable for transmitting an electrical detection signal generated by the photodetector from the adapter connector to the module connector. The adapter connector is configured such that an end of the light guide is positioned to provide light into a gas cavity of the respiratory adapter. The adapter connector is configured such that, when the adapter connector is connected to the respiratory adapter, the photodetector detects light provided by the end of the light guide that has interacted with gas provided into the gas cavity. This can improve the accuracy of respiratory gas detection.

Description

[Technical field]

[0001] The present invention relates to a patch cable, a respiratory adapter, a respiratory module, and a respiratory gas detection system that can be used in the field of respiratory gas detection. [Background technology]

[0002] Detecting respiratory gases in a patient's breath generally relies on the absorption of light in a specific wavelength range by the respiratory gas to be detected. This approach requires the provision of a light source (most often a thermal mid-infrared source) and the detection of the absorption of light in a specific wavelength range by each respiratory gas in the patient's breath to determine the concentration of each respiratory gas in the patient's breath. One example of such an application is capnography, in which the carbon dioxide CO2 concentration in the patient's breath is detected. In many approaches, to detect respiratory gases, the patient's exhaled gas is pumped through a cannula and a sampling tube to a monitoring module that contains the necessary technology to detect the breath, specifically, a mid-infrared source, a spectral filter, a photodetector, and detection electronics. In such approaches, the pump consumes a large amount of power, which inhibits the development of small, battery-powered mobile devices for detecting breath gases. In addition, the tributary sampling tube causes signal delays and distortions due to gas transport, and is prone to clogging due to respiratory secretions and humidity.

[0003] Another approach uses a near-infrared diode laser source and optical fibers to guide light from a laser in the monitoring module to a respiratory adapter, such as an oronasal cannula, and guides unabsorbed light from the respiratory adapter to the monitoring module. In this case, a pump can be omitted since gas does not need to be transported from the patient's airway to the detector. In this approach, a small, low-power monitoring module can be constructed by using tunable diode laser absorption spectroscopy (TDLAS) and a vertical cavity surface emitting laser (VCSEL) as the light source provided in the monitoring module. Such a capnography module can be battery-powered and portable by the patient, reducing the number of cables attached to the patient. Alternatively, the electronics for respiratory gas detection can be incorporated into a small, portable vital signs patient monitor. The general concept of such an approach is described, for example, in US2011 / 0066061A1, WO2015 / 104531A1, and WO2017 / 162804A1. Summary of the Invention [Problem to be solved by the invention]

[0004] However, this technique also has some challenges. For example, in capnography, tunable near-infrared diode lasers are often used and CO2 is detected based on the optical absorption of the delivered laser light, because fiber and semiconductor laser technology is well developed in the near-infrared range. However, the absorption of CO2 in the near-infrared is much smaller than that in, for example, the mid-infrared wavelength range. In addition, the technique using optical fibers often suffers from signal quality degradation due to interference effects caused by reflections at the surfaces of optical components in the light path or internal interference in multimode fibers. These quality degradation effects are also called spectral background and can affect the accuracy of respiratory gas concentration detection. Another major problem is that to obtain a proper and stable CO2 signal without distortion, single-mode fibers are required as light guides from the laser to the CO2 detection cavity and from the CO2 detection cavity to the remote detector. This results in placement and alignment tolerances of the order of one micrometer. As a result, the robustness and reliability of the device are reduced and the manufacturing costs increase. It would therefore be beneficial to provide a breath detection approach that allows for improved accuracy, robustness, and reliability of breath gas concentration detection while maintaining the advantage of providing a compact device for detecting breath gas.

[0005] It is an object of the present invention to provide a patch cable, a respiratory adapter, a respiratory module, and a respiratory gas detection system that allows for improved detection of respiratory gas contained in a patient's breath and provides a lightweight and compact respiratory gas detection system. [Means for solving the problem]

[0006] In a first aspect of the present invention, a patch cable is provided for connecting a respiratory module to a respiratory adapter, the respiratory adapter including a gas cavity, the respiratory adapter and the gas cavity configured such that respiratory gas from a patient can enter the gas cavity when the respiratory adapter is placed in functional contact with the patient's mouth and / or nose, the respiratory module processes data indicative of a concentration of the respiratory gas based on a signal provided via the patch cable, the patch cable comprising: a) a module connector connecting a first end of the patch cable to the respiratory module; and b) an adapter connector connecting a second end of the patch cable to the respiratory adapter, the adapter connector including a light detector. , c) a light guide that guides light from the module connector to the adapter connector, the adapter connector being configured such that an end of the light guide is positioned to supply light into a gas cavity of the respiratory adapter when the adapter connector is connected to the respiratory adapter; and d) an electrical cable that transmits an electrical detection signal generated by the light detector from the adapter connector to the module connector, the adapter connector being configured such that when the adapter connector is connected to the respiratory adapter, the light detector detects light supplied by the end of the light guide that has interacted with gas supplied into the gas cavity, and the detection signal generated by the light detector is indicative of the concentration of respiratory gas supplied into the gas cavity.

[0007] The patch cable includes not only a light guide for guiding light from the module connector to the adapter connector, but also an electrical cable for sending an electrical detection signal generated by a photodetector disposed in the adapter connector to the module connector, the adapter connector being configured such that the photodetector detects the light provided by the end of the light guide interacting with the gas provided in the gas cavity, and the detection signal generated by the photodetector indicates the concentration of the respiratory gas provided in the gas cavity, so that the respiratory gas can be detected locally, i.e., directly in the patient's airway. Therefore, there is no signal delay, no distortion of the capnogram caused by gas transport, and there is also no problem of clocking of the tributary tube. Furthermore, since the photodetector is integrated in the adapter connector, the light can be focused on the photodetector instead of the light guide, and the area of ​​the detector is larger than the cross-sectional area of ​​the fiber core, the tolerance to optical alignment deviations is greatly increased. This allows the accuracy of respiratory gas detection to be improved, and at the same time, a robust system for respiratory gas detection and a small and lightweight respiratory module can be developed.

[0008] A patch cable generally provides a connection between a respiratory module and a respiratory adapter of a respiratory gas detection system. A patch cable can be provided as a single cable, but can also be provided as multiple cables, i.e., a patch cable set, with each of the multiple cables attached to the adapter connector and the module connector. For example, a patch cable may include one cable including a light conductor and one cable including an electrical cable, both of which are attached to the same respiratory adapter, but attached to different module connectors. Additionally, a patch cable may include a split where the patch cable is split into two or more branches, i.e., cables. For example, a patch cable may include one branch including a light conductor and one branch including an electrical cable. Thus, a patch cable may also be considered a patch cable set providing one or more cable branches that together form a patch cable.

[0009] The respiratory adapter can be provided in several different forms, and is generally configured to capture respiratory gas, i.e., respiratory gas in the patient's airway, so that it can enter a gas cavity provided in the respiratory adapter. In this context, being in functional contact with the patient's mouth and / or nose refers to being located in a position that allows at least a portion of the patient's exhaled and / or inhaled gas to enter the gas cavity provided by the respiratory adapter. The respiratory adapter may be a nasal cannula for sampling nasal breath, or an oronasal cannula for patients who sometimes breathe through their nose and other times breathe through their mouth. The respiratory adapter may also be part of a ventilation circuit for a patient undergoing ventilation therapy. In that case, the respiratory adapter is an airway adapter and is provided as part of the ventilation tubing used in ventilation therapy. Furthermore, the respiratory adapter is configured to be connected to the respiratory module by an adapter connector of a patch cable. In general, the combination of the respiratory adapter and a correspondingly configured patch cable, as described below, can be considered to form a respiratory gas detection signal supply unit configured to supply a detection signal indicative of the concentration of the respiratory gas to the respiratory module.

[0010] The respiratory module includes at least some circuitry configured to process data indicative of the concentration of the respiratory gas. In one embodiment, the respiratory module is configured to determine the concentration of the respiratory gas in the patient's breath directly using the detection signal provided by the detector via the electrical cable of the patch cable. The respiratory module may be configured to process data indicative of the concentration of one or more selected respiratory gases based on the signal provided via the patch cable. Furthermore, the respiratory gas module may be configured to provide the processing results to a user, for example, via a small display or some other visible or audible output, for example, an alarm may be provided if a concentration threshold of one or more respiratory gases is exceeded. Furthermore, the respiratory module may be configured to be connected, for example, via a wireless connection, to a vital signs patient monitor or other monitoring module for monitoring the patient, such as a cardiac activity monitoring device or a blood pressure monitoring device.

[0011] The respiratory module may also be configured to include a light source providing light that is guided by the light conductors of the patch cable to the respiratory adapter. However, in another embodiment, the light source may be incorporated into the module connector and the respiratory module may be configured to provide the power required for the light source to generate light via a connection to the module connector. Because the respiratory module does not need to provide a pump or a light detector, the respiratory module can be small and lightweight, and therefore wearable by a patient, for example, by using suitable attachment means.

[0012] The patch cable includes a module connector and an adapter connector. Preferably, the patch cable includes one module connector and one adapter connector. However, for example, when the patch cable refers to a patch cable set, the patch cable can also include multiple module connectors and multiple adapter connectors. Furthermore, the module connector and the adapter connector may include multiple parts, and each part may be individually connected to the respiratory module and the respiratory adapter. For example, the adapter connector may include two parts, and when both parts of the adapter connector are connected to the respiratory adapter, one part is configured to provide the light detector to the gas cavity and the other part to provide the end of the light guide to the gas cavity.

[0013] The module connector is configured to connect the patch cable to the respiratory module. In particular, the module connector and the respiratory module each include a connection configured to allow them to be connected to each other, for example using a plug and socket mechanism. Furthermore, the adapter connector also includes a connection configured to be connected to a corresponding connection of the respiratory adapter. In particular, the connection between the adapter connector and the respiratory adapter is configured such that, when the adapter connector is connected to the respiratory adapter, the light provided by the end of the light guide is provided to the gas cavity and the light passing through the gas in the gas cavity can be detected by the light detector. Preferably, the respiratory adapter provides a connection in the form of an opening in the housing of the respiratory adapter, into which the cable connection of the adapter connector can be fitted such that the light provided by the end of the light guide can reach the gas cavity and the light from the gas cavity can reach the light detector. The opening may be separated from the gas cavity by a transparent window, allowing the light provided by the end of the light guide and the light detected by the light detector to pass through the transparent window.

[0014] The light guide of the patch cable is configured to guide light from the module connector to the adapter connector. The light guide may refer to one optical fiber, but may also refer to multiple optical fibers, for example, each of which is configured to guide a different wavelength of light to the respiratory adapter. These optical fibers may be selected to be optimal for detecting CO2, O2, or a volatile anesthetic agent. Preferably, one or more optical fibers of the light guide are single-mode optical fibers. Single-mode optical fibers have the advantage that the spectral background in the optical fiber can be neglected. In particular, the light guide preferably includes a single-mode silicate fiber suitable for guiding light of wavelengths close to 2 μm, which corresponds to the CO2 absorption wavelength. In another embodiment, the light guide may include a multimodal optical fiber.

[0015] The electrical cable of the patch cable is configured to transmit the electrical detection signal generated by the photodetector from the adapter connector to the module connector. The electrical cable includes one or more electrical wires. For example, the electrical cable can include a wire configured as a signal line for transmitting the electrical signal generated by the photodetector from the adapter connector to the module connector, and can further include an electrical wire configured as a power line for providing power from the module connector to the photodetector.

[0016] The light detector provided as part of the adapter connector is preferably a photodiode configured to convert light impinging on its surface into an electrical signal. In particular, the photodiode may be configured to be particularly suitable for converting light of the wavelength provided by the light guide into an electrical signal. Preferably, the light detector is an InGaAs detector configured to detect light in the near infrared spectrum.

[0017] In one embodiment, the adapter connector includes a first connector portion and a second connector portion, the first connector portion including a light detector and the second connector portion including an end of a light guide, and the first connector portion and the second connector portion connect the adapter connector to the respiratory adapter such that when the adapter connector is connected to the respiratory adapter, light fed through the end of the light guide and passing through a gas cavity of the respiratory adapter is detected by the light detector.

[0018] The first and second connector portions of the adapter connector may be provided, for example, by splitting the patch cable at a point in the patch cable into a first cable portion including an electrical cable connected to the photodetector and a second cable portion including a light conductor providing light to an end of the light conductor. Splitting of the patch cable may be performed at any length of the patch cable, for example, the patch cable may be provided directly as a patch cable set including the first and second cable portions. The breathing adapter may be configured such that the first and second connector portions are provided on different sides of the gas cavity, for example, by providing two different connection portions on different sides of the gas cavity to which the first and second connector portions can be connected to connect the adapter connector to the breathing adapter. Alternatively, the breathing adapter may be configured to provide the connector portions on the same side of the gas cavity. In this embodiment, a reflector, such as a mirror, is provided on the opposite side of the gas cavity so that when the adapter connector is connected to the breathing adapter, light provided by the end of the light guide in the second connector portion can be detected by a photodetector provided in the first connector portion.

[0019] In one embodiment, the adapter connector has a U-shape, the end of the light guide is disposed on one side of the U-shaped adapter connector, and the light detector is disposed on the other side of the U-shaped adapter connector, and when the adapter connector is connected to the respiratory adapter, the light provided through the end of the light guide and passing through the cavity of the respiratory adapter is detected by the light detector. Specifically, in this embodiment, the end of the light guide is disposed on one side of the U-shaped adapter connector, and the light detector is disposed on the other side of the U-shaped adapter connector, and when the adapter connector is connected to the respiratory adapter, the end of the light guide and the light detector face each other through the gas cavity. In this embodiment, the respiratory adapter is configured to provide a connection configured to connect to the U-shaped adapter connector. For example, the respiratory adapter may include a connector opening as a connection, into which the two sides of the U-shaped adapter connector can be fitted, such that the light provided by the light guide can be provided to the gas cavity and the light passed through the gas cavity can be detected by the light detector.

[0020] In one embodiment, the respiratory adapter provides at least one reflector as part of the respiratory adapter on the side of the gas cavity opposite the connection side where the adapter connector can be connected to the respiratory adapter, the adapter connector being configured such that when the adapter connector is connected to the respiratory adapter, the end of the light guide and the light detector are oriented in substantially the same direction and light provided by the end of the light guide into the gas cavity and reflected by the at least one reflector provided as part of the respiratory adapter is detected by the light detector. In this embodiment, the respiratory adapter may be configured to provide a connection, such as a connector opening, on one side of the respiratory adapter into which the adapter connector can fit, such that the end of the light guide can provide light into the gas cavity and the light detector can detect the light provided into the gas cavity. Specifically, the respiratory adapter may have a reflector, such as a mirror, arranged on the opposite side of the gas cavity, such that the light provided by the end of the light guide is reflected by the reflector to hit the light detector, in this embodiment. The reflector may include a metal layer, preferably an aluminum layer, or a dielectric multilayer coating as a reflective layer.

[0021] In one embodiment, the end of the light guide includes a lens integrated into the adapter connector. In a preferred embodiment, the lens is a gradient index lens (GRIN lens). In another embodiment, the lens can be a plastic lens or a ball lens. The lens may be configured to focus the light provided by the end of the light guide to a particular point, for example to focus the light on the photodetector. The characteristics of the lens may therefore be determined by the dimensions and configuration of the breathing adapter, and in particular the gas cavity provided by the breathing adapter. For example, the focal length of the lens may refer to the length of the optical path followed by a light beam between the surface of the lens through the gas cavity and the surface of the photodetector. By providing a lens in front of the end of the light guide, i.e. between the gas cavity and the end of the light guide, the light can be focused on the surface of the detector. The diameter of the focused spot can be much smaller than the diameter of the detector. Even if the spot is off-center relative to the detector due to placement tolerances, the light can still be detected if the detector surface is large enough. This allows for a large placement and alignment tolerance.

[0022] In one embodiment, the photodetector is connected to an integrated circuit (IC) integrated into the adapter connector. Preferably, the IC is an amplification IC that amplifies the detection signal of the photodetector so that the electronic signal from the photodetector to the respiratory module is less susceptible to external disturbances.

[0023] In one embodiment, the adapter connector is configured such that the surface of the photodetector, where the light is detected, is positioned at an angle to the beam direction of the light detected by the photodetector. In general, the beam direction of the light detected by the photodetector can be defined as the average beam direction, which refers to the spatial average of all light beams fed by the ends of the light guide and impinging on the photodetector. The beam direction may also be defined by a central light beam fed at the center of the light guide and following a path through the gas cavity according to the optical arrangement of the breathing adapter and the adapter connector. Furthermore, the angle between a surface and a line, e.g., a beam direction, can be defined as the angle between the line and a normal to the surface. The photodetector is positioned at an angle to the beam direction of the light detected by the photodetector, so that the light reflected by the detector surface cannot again be part of the light beam impinging on the detector surface. Thus, the contribution of the light reflected at the detector surface to the spectral background can be reduced. Preferably, the angle of the detector surface to the beam direction is between 3° and 20°.

[0024] In one embodiment, the surface at the end of the light guide provides an angle with respect to the beam direction of the light provided by the end of the light guide into the gas cavity when the adapter connector is connected to the breathing adapter. In particular, the surface at the end of the light guide provides an angle with respect to the side wall of the light guide. Furthermore, if the breathing adapter provides at least one reflector as part of the gas cavity on the side of the gas cavity opposite to the side where the end of the light guide provides light into the gas cavity, the surface at the end of the light guide can provide an angle with respect to the reflective surface of the gas cavity. Furthermore, if the end of the light guide includes a lens, the surface of the lens facing the gas cavity when the adapter connector is connected to the breathing adapter may be provided with the angle. In this case, the angle can be defined with respect to the central plane of the lens. Preferably, the angle of the surface at the end of the light guide with respect to the side of the light guide is between 2° and 20°, in particular 8°.

[0025] In one embodiment, the adapter connector further comprises a front part made of a transparent material, the front part being arranged between the end of the light guide and / or the photodetector and the gas cavity when the adapter connector is connected to the breathing adapter. The front part made of a transparent material, for example glass, may have a predetermined thickness and have the form of an angled or circular plate made of a transparent material. In a preferred embodiment, the front part of the end of the light guide and / or the front part of the photodetector, i.e. the transparent front part located between the end of the light guide and / or the photodetector and the gas cavity, is an optical window, which is inclined with respect to the beam direction of the light detected by the photodetector and / or the light provided by the end of the light guide passing through the optical window. Preferably, the inclination angle is between 3° and 20°, in particular 5°. In a further preferred embodiment, the space formed between the front part and the light guide and / or the photodetector is filled with an optical gel, for example an optical gel having a predetermined refractive index. The refractive index may be, for example, 1.44 or another refractive index close to the refractive index of the optical window.

[0026] In one embodiment, the module connector further includes: i) a light supply unit for supplying light through the light guide; and ii) a processing unit for receiving the electrical detection signal provided by the photodetector, the processing unit generating a data signal representative of the concentration of the respiratory gas based on the electrical detection signal. The light supply unit may be a laser light supply unit provided in the module connector. Preferably, the light supply unit is a VCSEL unit. The processing unit may be a dedicated circuit configured to receive the electrical detection signal provided by the photodetector and generate the data signal by determining the respiratory gas concentration based on the electrical detection signal. However, the processing unit may also refer to a software unit running on a general-purpose or dedicated processing device that is part of the module connector.

[0027] Since the light supply unit and the processing unit are provided as part of the module connector of the patch cable, the respiration module does not need to provide a corresponding light supply unit or a corresponding processing unit and can be constructed even more lightweight. In this case, the respiration module only needs to provide electricity to the module connector to power the light supply unit and the processing unit of the module connector, so the connection between the module connector and the respiration module can also be simplified to an electrical connector, and there is no need to provide a connector for, for example, a light guide. The main function of the respiration module here is to provide capnography data to the user and to obtain input from the user regarding capnography settings. In this embodiment, the patch cable can be considered as a smart patch cable, which is defined by providing additional functions beyond providing a simple connection between the respiration module and the respiration adapter. In another embodiment, the module connector of the patch cable may include only one of the above units, i.e., only the light supply unit or only the processing unit.

[0028] In another aspect of the invention, a respiratory adapter is provided for connection to an adapter connector of a patch cable as described above, the respiratory adapter including a gas cavity, the respiratory adapter and the gas cavity being configured such that when the respiratory adapter is in functional contact with a patient, respiratory gas from the patient can enter the gas cavity, the respiratory adapter further connecting to the adapter connector such that light provided by an end of the light guide can be detected by a light detector of the adapter connector after passing through the gas cavity to interact with the respiratory gas provided in the gas cavity. For example, the respiratory adapter can provide a connector portion, e.g. a connector opening, to which a connector portion of the adapter connector can be connected.

[0029] In one embodiment, the surface of the gas cavity has an angle with respect to the beam direction of the light beam fed through the end of the light guide when the adapter connector is connected to the breathing adapter. Preferably, the angle between the beam direction of the light beam fed through the end of the light guide and the surface of the gas cavity is greater than 3°, preferably 5°. Because the surface of the gas cavity has an angle with respect to the beam direction of the light beam fed through the end of the light guide when the adapter connector is connected to the breathing adapter, light that hits the surface of the gas cavity is not reflected back to the light guide or the photodetector and therefore does not contribute to the spectral background.

[0030] In one embodiment, the respiratory adapter includes at least one reflector, the at least one reflector being arranged such that when the adapter connector is connected to the respiratory adapter, the light provided by the end of the light guide is reflected by the at least one reflector and detected by the light detector after reflection at the at least one reflector. In particular, the position and configuration of the at least one reflector in the respiratory adapter depends on the position and orientation of the end of the light guide and the light detector when the adapter connector is connected to the respiratory adapter. For example, as described above, when the adapter connector is configured such that the end of the light guide and the light detector are provided on the same side of the gas cavity when the adapter connector is connected to the respiratory adapter, at least one reflector may be provided on the opposite side of the gas cavity. Furthermore, as also described above, when the adapter connector is configured such that the end of the light guide and the light detector are provided on different sides of the gas cavity when the adapter connector is connected to the respiratory adapter, at least one reflector may be provided on each side of the gas cavity such that the light provided by the end of the light guide is reflected more than once before being detected by the light detector. Such a configuration using two or more reflectors may also be used in embodiments in which the end of the light guide and the light detector are provided on the same side of the gas cavity when the adapter connector is connected to the breathing adapter, in which case the light is reflected at least three times after being delivered by the end of the light guide and before being detected by the light detector.

[0031] In one embodiment, the reflector may be tilted relative to the beam direction of the light provided by the light guide into the gas cavity. Specifically, the reflector may be tilted to reflect the light to the light detector. The tilt may then be predetermined based on the position of the end of the light guide and the light detector when the adapter connector is connected to the breathing adapter.

[0032] In a preferred embodiment, at least one of the at least one reflectors provided is a spherical reflector for focusing the light beam provided by the end of the light guide onto the light detector when the adapter connector is connected to the breathing adapter. For example, the spherical reflector may be a spherical mirror having a predetermined radius that may be determined based on the position and orientation of the end of the light guide and the light detector when the adapter connector is connected to the breathing adapter. The spherical reflector may focus the light onto the surface of the detector. The diameter of the focused spot may be much smaller than the diameter of the detector. Even if the spot is off-centered relative to the detector due to placement tolerances, the light can still be detected if the detector surface is large enough. This allows for a large placement and alignment tolerance. Also, in this embodiment, the spherical reflector may be tilted with respect to the beam direction of the light provided by the light guide.

[0033] In another aspect of the present invention, a respiratory gas detection signal providing unit is provided comprising a respiratory adapter as described above and a patch cable as described above, the respiratory adapter and the patch cable being configured such that when the adapter connector is connected to the respiratory adapter, light provided by an end of a light conductor provided by the adapter connector can be detected by a light detector provided by the adapter connector after interacting with gas in a gas cavity provided by the respiratory adapter.

[0034] In another aspect of the invention, a respiratory module is presented that is configured to be connectable to a module connector provided by a patch cable as described above, the respiratory module being configured to determine a concentration of a respiratory gas based on a signal provided by the patch cable, the respiratory module including an output unit for outputting the determined concentration of the respiratory gas. The respiratory module may be configured to determine the gas concentration based on a detection signal of the photodetector or, if the module adapter of the patch cable includes a processing unit, based on a data signal provided by the processing unit that represents the concentration of the respiratory gas. The output unit may, for example, be a display for displaying the determined concentration of the respiratory gas. However, the output unit may also be configured to provide another form of output, for example an audible or visible output provided by a loudspeaker or an LED, respectively, the output being indicative of the determined concentration of the respiratory gas. In particular, an alarm may be provided by the output unit if a predefined threshold value of the concentration of the respiratory gas is exceeded.

[0035] In one embodiment, the respiratory module further includes: i) a light supplying unit configured to supply light to the light guide of the patch cable via the module connector when the patch cable is connected to the respiratory gas detection module; and ii) a processing unit configured to receive an electrical detection signal provided by the light detector when the patch cable is connected to the respiratory gas detection module, the processing unit configured to determine the respiratory gas concentration based on the electrical detection signal. In this embodiment, the patch cable does not refer to a smart patch cable, i.e., the patch cable itself does not provide the light supplying and / or gas concentration determining functions. In this case, it is preferred that the respiratory module provides the light supplying unit and the processing unit for determining the gas concentration.

[0036] In one embodiment, the light supply unit is configured to supply light having a wavelength substantially equal to an absorption wavelength of the respiratory gas whose concentration is to be determined. For example, the light supply unit may be configured to supply light in the near infrared or mid infrared spectrum, which refers to wavelengths known to be absorbed by CO2 as the respiratory gas.

[0037] In a preferred embodiment, the light providing unit is configured to modulate the wavelength of the light provided to be in the vicinity of an absorption wavelength of the respiratory gas whose concentration is to be detected, such that the detection signal provided by the photodetector is also modulated, and the processing unit is configured to determine the concentration of the respiratory gas based on the detected signal at the second harmonic of the modulation frequency.

[0038] In another aspect of the present invention, a respiratory gas detection system is provided, including a respiratory gas module as described above, a respiratory adapter as described above, and a patch cable as described above for connecting the respiratory gas module to the respiratory adapter. In particular, the respiratory gas module, the respiratory adapter, and the patch cable are configured such that the patch cable can be used to connect the respiratory gas module to the respiratory adapter, and the respiratory gas detection system is configured to determine a concentration of the respiratory gas. The respiratory gas detection system may refer to any technically suitable combination of the above embodiments of the respiratory gas module, the respiratory adapter, and the patch cable.

[0039] It will be appreciated that the patch cable, the respiratory adapter, and the respiratory module together form a respiratory gas detection system, and that the configuration of one of the elements of the respiratory gas detection system may affect the configuration of other elements of the respiratory gas detection system, in particular as described in the dependent claims.

[0040] It is to be understood that a preferred embodiment of the invention can also be any combination of the dependent claims or the above embodiments with the independent claims.

[0041] These and other aspects of the invention will be elucidated and elucidated with reference to the embodiments described hereinafter. [Brief description of the drawings]

[0042] [Figure 1] FIG. 1 illustrates, in a schematic and exemplary manner, an embodiment of a respiratory gas detection system according to the present invention. [Diagram 2] FIG. 2 illustrates, in a schematic and exemplary manner, an embodiment of a respiratory gas detection system according to the present invention. [Diagram 3] FIG. 3 illustrates diagrammatically and exemplarily an embodiment of a respiratory adapter according to the invention. [Figure 4] FIG. 4 illustrates, in a schematic and exemplary manner, an embodiment of a respiratory gas detection system according to the present invention. [Figure 5A-5E] 5A-5E show schematic and exemplary different embodiments of a breathing adapter and patch cable according to the present invention. [Figure 6-7] 6 and 7 show simulated optical paths in an exemplary embodiment of a respiratory adapter connected to a patch cable according to the present invention. [Figure 8] FIG. 8 shows, diagrammatically and exemplarily, a detailed embodiment of a respiratory adapter and patch cable according to the invention. [Figure 9] FIG. 9 shows a schematic and exemplary embodiment of a breathing module according to the invention. [Figure 10A-10B] 10A and 10B show schematic and exemplary two embodiments of a nasal cannula together with a patch cable connector. [Figure 11] FIG. 11 illustrates, in a schematic and exemplary manner, an embodiment of a respiratory adapter having a connector receptacle insert. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] FIG. 1 shows an embodiment of a respiratory gas detection system according to the present invention in a schematic and exemplary manner. In this exemplary embodiment, the respiratory gas detection system is worn by a patient 120 and comprises a respiratory adapter 101, a patch cable 110, and a respiratory gas module 103. In this exemplary embodiment of the respiratory gas detection system, the respiratory module 103 may include a battery pack, a processing unit configured to process a received electrical detection signal indicative of a respiratory gas concentration, and an optical supply unit for supplying light within an absorption wavelength range of the respiratory gas to be detected. Furthermore, the respiratory module 103 may comprise a wireless connection unit configured to connect the respiratory module 103 to a patient monitor that may be used to indicate, for example, a processing result of the detection signal. Furthermore, the respiratory module 103 is configured to be connected to the patch cable 110. For example, the respiratory module 103 may comprise a connection portion configured to be connectable to a connection portion of the patch cable 110. Specifically, in this embodiment, the connection portion includes an optical interface for providing an optical connection between the optical supply unit and an optical conductor of the patch cable 110. The optical interface is configured to couple the light provided by the optical supply unit to the optical conductor of the patch cable 110. Furthermore, in this embodiment, the respiratory module 103 includes an electrical signal interface that provides an electrical connection between the processing unit and the electrical cable of the patch cable 110 to pass the electrical detection signal from the patch cable 110 to the processing unit.

[0044] The respiratory adapter 101 is configured to be placed in functional contact with the airway of the patient 120 and to provide a gas cavity through which the breath of the patient 120 can pass. In the embodiment shown in Figure 1, the respiratory adapter 101 has the form of a disposable cannula that is attached to the patient's airway, in this case the patient's nose and mouth. Additionally, the respiratory adapter 101 is configured to be connected to the adapter connector 114 of the patch cable 110.

[0045] The patch cable 110 comprises a module connector 113 for connecting a first end of the patch cable 110 to the respiratory module 103. Additionally, the patch cable 110 comprises an adapter connector 114 for connecting a second end of the patch cable 110 to the respiratory adapter 101. The adapter connector 114 further comprises a light detector for detecting light in the wavelength range provided by the light providing module and referencing the absorption wavelength range of the respiratory gas to be detected.

[0046] Furthermore, the patch cable 110 comprises a light guide for guiding light from the module connector 113 to the adapter connector 114, and an electrical cable for transmitting an electrical detection signal generated by the light detector from the adapter connector 114 to the module connector 113. The adapter connector 114 and the respiratory adapter 101 are configured relative to each other such that when the adapter connector 114 is connected to the respiratory adapter 101, the light provided by the end of the light guide passes through the gas cavity of the respiratory adapter 101 and can be detected by the light detector. Thus, the respiratory adapter 101 and the patch cable 110 can be considered as a gas detection signal providing unit for providing a gas detection signal to the respiratory module 103. In general, the respiratory adapter may be disposable after use by a patient. Preferably, the patch cable is washable, for example by wiping it with a special disinfectant, and reusable for other patients. HHH However, in other embodiments, the respiratory adapter may also be washable and reusable. Furthermore, in other embodiments, the patch cable may be disposable after use by a patient.

[0047] In the embodiment shown in FIG. 1, the patch cable 110 includes two cable sections both connected to one module connector. Furthermore, the two cable sections may both be connected to the same adapter connector, or the adapter connector may include a first section and a second section, with each cable section being connected to the respiratory adapter 101 via one of the sections of the adapter connector. In this embodiment, the respiratory adapter 101 may be an oronasal cannula with prongs for sampling respiratory air through the nose and a mouth cap for sampling inhaled and exhaled air through the mouth. The two cable sections in this embodiment have the advantage that the cable sections may split under the patient's face, for example, as shown in FIG. 1, to allow the respiratory adapter 101 to be in functional contact with the patient's airway, i.e., to be positioned in front of the patient's nose and / or mouth. In this configuration, one of the cable sections may include a light guide for guiding light from the respiratory module 103 to the respiratory adapter 101, and the other patch cable section may include an electrical cable for transmitting an electrical detection signal generated by a light detector to the respiratory module 103.

[0048] In Fig. 2, a schematic and exemplary overview of another embodiment of a respiratory gas detection system according to the present invention is provided, which will be described below. Patients with respiratory problems often need supplemental oxygen directly to their airways. Thus, in this embodiment, the respiratory gas detection system 200 includes an oxygen source including an oxygen supply tube 204 and an oxygen supply connector 206, in addition to a respiratory adapter 201, a patch cable 210, and a respiratory module 203. The oxygen supply connector 206 is configured to connect to an oxygen source configured to supply oxygen to the patient via the oxygen supply tube 204. To combine the oxygen source with the respiratory adapter 201, a flow path may be provided in or on the respiratory adapter 201 for directing supplemental oxygen to the patient's airways, for example the patient's nose. Preferably, the respiratory adapter 201 is configured such that the oxygen flow passes outside a gas cavity provided in the respiratory adapter 201 that is used to detect the concentration of respiratory gas contained in the patient's breath. This prevents the oxygen provided via the oxygen supply tube 204 from mixing with the patient's exhaled breath in the gas sensing cavity and affecting respiratory gas detection.

[0049] In the exemplary embodiment shown in Figure 2, patch cable 210 is provided as only one patch cable, in contrast to patch cable 110 shown in Figure 1. Thus, patch cable 210 in this embodiment includes an adapter connector that does not have two connector portions. Note that the adapter connector is not directly shown in Figure 2. Instead, in this embodiment, the adapter connector and respiratory adapter 201 are configured such that the adapter connector of patch cable 210 can be connected to one side of respiratory adapter 201 such that oxygen supply tube 204 can be connected to another side of respiratory adapter 201, preferably the opposite side of respiratory adapter 201.

[0050] Additionally, in this exemplary embodiment, an adjustable slider 205 is provided around the patch cable 210 and the oxygen delivery tube 204. The adjustable slider 205 may be used to secure the oxygen delivery tube 204 and patch cable 210 to the patient, for example, by routing the patch cable 210 and oxygen delivery tube 204 behind the patient's ear and adjusting the adjustable slider 205 to secure the patch cable 210 and oxygen delivery tube 204 under the patient's chin, thereby fixing the position of the patch cable 210, oxygen delivery tube 204, and breathing adapter 201 relative to the patient's head. Thus, the adjustable slider 205 associated with the patch cable 210 and delivery tube 204 may be considered an attachment means that allows the breathing adapter 201 to be attached to the patient.

[0051] In the embodiment shown in FIG. 2, the respiratory adapter 201 and the patch cable 210 are configured such that the patch cable 210 is connected to the respiratory adapter 201 only from one side of the respiratory adapter 201. However, as shown in more detail in FIG. 3, the patch cable may also be configured to include a first connector portion 311 and a second connector portion 312, as already shown with respect to FIG. 1. In such an embodiment, the respiratory adapter 301 may be configured such that the first connector portion 311 and the second connector portion 312 are connectable to the respiratory adapter 301 on opposite sides of the respiratory adapter 301, specifically, on opposite sides of a gas cavity provided within the respiratory adapter 301. A portion of the patient's nasal respiratory flow may pass through the prongs 313 and the gas cavity provided by the respiratory adapter 301. In such an embodiment, if an oxygen supply tube 204 is present, the oxygen supply tube 204 may be provided independent of the respiratory adapter 301, i.e., not connected to the respiratory adapter 301. Alternatively, the respiratory adapter 301 may provide an additional path for an oxygen source to which the oxygen delivery tube 204 can be connected. Preferably, the oxygen delivery tube 204 is positioned on the respiratory adapter 301 and coupled to a separate prong 314. This embodiment allows for easy combination of the oxygen delivery tube with embodiments of the respiratory gas detection system 100 such as that shown in FIG.

[0052] FIG. 4 shows, in a schematic and exemplary manner, another embodiment of a respiratory gas detection system. In this embodiment, a respiratory gas detection system 400 is combined with a ventilation system for ventilating the lungs of a patient. The respiratory gas detection system 400 in this case also comprises a respiratory adapter 401, a patch cable 410, and a respiratory module 403. In the exemplary embodiment shown in FIG. 4, the respiratory adapter 401 and the patch cable 410 provide a connection configuration similar to the connection configuration as shown in FIG. 3. Specifically, the patch cable 410 shown in FIG. 4 is similar to the patch cable shown in FIG. 3, and comprises a first connector portion 411 and a second connector portion 412 connectable to opposite sides of the respiratory adapter 401. However, in this embodiment, the respiratory adapter 401 is configured to be incorporated into a ventilation system for ventilating the lungs of a patient as an airway adapter. For example, the respiratory adapter 401 may be configured to be disposed between a first portion of a ventilation tube 404 used for intubating a patient and a second portion of the ventilation tube 404 connecting the ventilation tube 404 to a ventilation system or circuit. In one exemplary embodiment, the respiratory adapter 401 may be used as a connection between a first portion of the ventilation tube 404 and a second portion of the ventilation tube 404, such that the gas supplied for ventilation passes through the respiratory adapter 401, in particular through a gas cavity provided by the airway adapter 401. However, in other embodiments, the airway adapter 401 may be connected to the patient's ventilation system in other ways, such that the breath gases supplied to or coming from the patient pass through a gas cavity provided in the airway adapter 401. In general, this modification of the respiratory adapter that allows it to be part of the ventilation system can be combined with any of the exemplary configurations of the respiratory adapter described above or below.

[0053] Further, in FIG. 4, an exemplary embodiment is shown in which the patch cable 410 is provided as a smart patch cable. In particular, the patch cable 410 comprises a module connector 413 including an optical supply unit and a processing unit. In particular, the optical supply unit and the processing unit are integrated in the module connector 413. Since the optical supply unit for supplying light through the light guides of the patch cable 410 is part of the module connector 413, the module connector 413 only needs to be configured to provide an electrical connection between the module connector 413 and the respiratory module 403. An interface for providing an electrical connection is generally less prone to failure than, for example, an optical interface, and in this embodiment, there is no need to provide a technically more complex optical interface between the module connector 413 and the respiratory module. Thus, in this example, the power for the optical supply unit and the processing unit in the module connector 413 is obtained via the connection between the module connector 413 and the respiratory module 403.

[0054] Preferably, in this embodiment, the processing unit is configured to receive the electrical detection signal provided by the light detector and to generate, based on the provided electrical detection signal, a digital data signal representative of the respiratory gas concentration. The module connector 413 may then be configured to transmit the digital data signal from the module connector 413 to the respiratory module 403, rather than transmitting only power for the light supply unit and the processing unit from the respiratory module 403 to the module connector 413. This allows the respiratory module to be provided with a standardized connector configured to receive a module connector, e.g. a connector portion or interface of the module connector 413, but the connector of the respiratory module may also be configured to receive a connector interface of other smart cables having other sensor types and providing digital data signals representative of the measurements of these other sensor types.

[0055] The respiratory module 403 may further be configured to recognize, for example, the digital data signal provided by the processing unit of the module connector 413 and identify the source of the digital data signal, for example, identifying that the digital data signal is provided by a smart patch cable for determining a respiratory gas concentration. The respiratory module 403 may then process the digital data signal, if necessary, based on the identification of the digital data signal and provide results of the respiratory gas concentration detection and / or other measurements to the patient monitor 405. The patient monitor 405 may be configured to visualize the results of the respiratory gas concentration detection and / or other measurements, for example, on a display. Furthermore, the patient monitor 405 may be configured to analyze the measurement results or combine information from the measurements with other information, for example patient data provided by the hospital network or provided by other sources.

[0056] In the embodiment shown in FIG. 4, the respiratory module 403 is integrated into the patient monitor 405. However, in other embodiments, such as, for example, the embodiment shown in FIG. 1, the respiratory module may be a standalone system or may be connected to the patient monitor only, for example, via a wireless connection. In general, the different configurations of respiratory adapter, patch cable and respiratory module described in relation to the above embodiments in relation to FIGS. 1-4 can be easily combined. For example, a smart patch cable, i.e. a patch cable including a module connector with integrated light supply and processing units and a correspondingly configured respiratory module, may also be used with the respiratory adapter shown in FIG. 2 or FIG. 3.

[0057] In the following, different possible embodiments of the respiratory adapter and the patch cable forming the respiratory gas detection signal supply unit are described in more detail in relation to Figures 5A to 5E, when the adapter connector is connected to the respiratory adapter. All these embodiments can be combined with any of the above-mentioned embodiments of the respiratory module. In general, components that are the same as one of the other embodiments shown in Figures 5A to 5E are provided with the same reference numbers.

[0058] FIG. 5A illustrates a first exemplary embodiment of a patch cable 510a including an adapter connector 520a. The adapter connector 520a is shown connected to a breathing adapter 501a including a gas cavity 530. In general, the breathing adapter refers to the entire structure surrounding the gas cavity 530, as shown in FIGS. 5A-5E. In this first embodiment, the adapter connector 520a is U-shaped. An end of a light guide 514a is disposed on one side of the U-shaped adapter connector 520a, and a light detector 515 is disposed on the other side of the U-shaped adapter connector 520a, with the light detector 515 and the end of the light guide 514a facing each other. Specifically, the end of the light guide 514a and the light detector 515 are positioned on opposite sides of the U-shaped adapter connector 520a such that when the adapter connector 520a is connected to the respiratory adapter 501a, light 531 provided by the end of the light guide 514a passes through the gas cavity 530 and strikes the light detector 515.

[0059] To improve the signal-to-noise ratio, in this embodiment the end of the light guide 514a may be provided with a GRIN lens that focuses the light provided by the end of the light guide 514a onto a photodetector 515, which may be for example a photodiode. This embodiment has the advantage that the U-shape of the adapter connector 520a provides a firm fixation of the relative positions of the end of the light guide 514a and the photodetector 515. Also, if the light 531 provided by the end of the light guide 514a is focused onto the photodetector 515, for example by a GRIN lens, a very small photodetector is obtained, which further allows reducing the cost of the patch cable and reducing the size of the adapter connector and thus the size of the breathing adapter.

[0060] Furthermore, it may be advantageous to provide the end of the light guide 514a with a lens, e.g., a GRIN lens, to provide an angle with respect to the beam direction of the light beam 531 provided by the end of the light guide 514a to the gas cavity 530. The lens focuses the light 531 onto the surface of the detector. The beam direction of the light beam 531 may generally be defined by the direction of the central beam of the light beam 531 provided by the center of the light guide 514a. Such an angle prevents undesired reflections of the provided light that are reflected back into the light guide 514a or reflected back onto the photodetector, thus reducing the spectral background caused by light reflections at the surface of the end of the light guide 514a. Furthermore, it may be advantageous to provide the photodetector 515, specifically the surface of the photodetector 514a facing the gas cavity 530, with an angle with respect to the beam direction of the light beam 531 detected by the photodetector 515. This also makes it possible to reduce the spectral background caused by, for example, reflections of light hitting the photodetector 515 off the surface of the photodetector 515 and / or off different surfaces.

[0061] Fig. 5B shows another exemplary embodiment of a patch cable 510b connected to a breathing adapter 501b via an adapter connector 520b. The main difference with the embodiment described with respect to Fig. 5A is that in this embodiment, the adapter connector 520b and the breathing adapter 501b are configured such that the adapter connector 520b is connected to only one side of the breathing adapter 501b. In particular, the connection portion, here the connection opening, which is the portion by which the adapter connector 520b can be connected to the breathing adapter 501b, is provided only on one side of the gas cavity 530.

[0062] In this exemplary embodiment, the adapter connector 520b is configured such that the end of the light guide 514a, including, for example, a GRIN lens, and the light detector 515 face substantially in the same direction. Furthermore, in this embodiment, the respiratory adapter 501b includes a reflector 532b as part of the respiratory adapter 501b, which is located on the opposite side of the adapter connector 520b when the adapter connector 520b is connected to the respiratory adapter 501b. Thus, the light 531 provided by the end of the light guide 514a is reflected by the reflector 532b located on the opposite side of the gas cavity 530 and passes through the gas cavity 530 twice before reaching the light detector 515. This allows for substantially doubling the light absorption while passing through the gas cavity 530 filled with gases being breathed by the patient, including respiratory gases that can absorb at least a portion of the light 531 provided by the end of the light guide 514a. This increased absorption may, for example, improve the signal-to-noise ratio and thus improve the detection sensitivity or allow the detection sensitivity to be kept constant while shortening the length of the gas cavity 530. Also in this exemplary embodiment, the surface of the light detector 515 and the surface of the end of the light guide 514a may be provided at an angle to the light beam 531, as described above with respect to FIG.

[0063] Another embodiment of a breathing adapter 501c that can be connected to the adapter connector 520b is shown in FIG. 5C. The main difference between the embodiment shown in FIG. 5C and the embodiment shown in FIG. 5A is that the reflector 532c of the breathing adapter 501c is provided as a spherical reflector. In this embodiment of the patch cable 510c, the lens, e.g., a GRIN lens, at the end of the light guide 514c is omitted and the spherical reflector 532c may focus the light provided by the end of the light guide 514c to the photodetector 515. Thus, when a diverging light beam 531 is provided by the end of the light guide 514c, the light is still focused by the reflector 532c to the photodetector 515. Preferably, again, the end of the light guide 514c is angled with respect to the direction of the light beam provided by the end of the light guide 514c to prevent back reflection interference that may contribute to the spectral background and instability of the diode laser light source. In this embodiment, the lens at the end of the light guide 514c is omitted, allowing the size of the adapter connector 520b to be reduced. Alternatively, the space otherwise occupied by the lens may be used to increase the size of the photodetector 515, making the system less susceptible to disturbances in the light path.

[0064] FIG. 5D shows another exemplary embodiment of a breathing adapter 501d to which the adapter connector 520b can be connected. In this embodiment, in addition to the first reflector 532c already shown in FIG. 5C, a second reflector 532d is provided as part of the breathing adapter 501d. Preferably, the second reflector 532d is also a spherical mirror. The first reflector 532c and the second reflector 532d are arranged in the breathing adapter 501d within the gas cavity 530 so that the light 531 provided by the end of the light guide 514c can pass through the gas cavity 530 four times before being focused on the light detector 515. Thus, in this embodiment, the signal-to-noise ratio can be further improved or the size of the gas cavity 530, specifically the length of the gas cavity 530, can be further shortened. Furthermore, in other embodiments, more reflectors may be provided to allow the light to pass through the gas cavity 530 more times.

[0065] A further embodiment of the patch cable 510e and the breathing adapter 501e is shown in Fig. 5E. In this embodiment, the adapter connector of the patch cable 510e includes a first connector portion 511 and a second connector portion 512, where the first connector portion 511 includes a light detector 515 and the second connector portion 512 includes an end of the light guide 514a. In this embodiment, the first connector portion 511 and the second connector portion 512 are configured to be connected to the breathing adapter 501e on opposite sides of the gas cavity 530. In particular, the breathing adapter 501e is configured to provide two connection portions, e.g., two connection openings, located on opposite sides of the breathing adapter 501e, to which the first connector portion 511 and the second connector portion 512, respectively, can be connected. The respiratory adapter 501e is specifically configured to provide a connector portion such that when the first connector portion 511 and the second connector portion 512 are connected to the connector portion of the respiratory adapter 501e, light provided by the end of the light guide 514a can impinge on the light detector 515.

[0066] As above, in this embodiment, the end of the light guide 514a may include a lens, for example, a GRIN lens. Furthermore, in this embodiment, the surface of the photodetector 515 and the surface of the end of the light guide 514a, for example, the surface of the GRIN lens, may be provided at an angle with respect to the beam direction of the light beam 531. This embodiment also shows that an IC 516 may be provided in the second connector portion 512 and connected to the photodetector 515. The IC 516 may be used to amplify the detection signal provided by the photodetector 515 and make the signal transport less susceptible to disturbances. The IC may also be provided in any of the other embodiments described above as part of the adapter connector and connected to the photodetector.

[0067] In all of the embodiments described above in connection with Figures 5A-5E, the respiratory adapter may be formed from a plastic, such as polycarbonate, that has limited absorption at the wavelengths used for detecting respiratory gases. For example, if the respiratory gas to be detected is CO2, then the respiratory adapter, or at least the portion of the respiratory adapter through which light passes, should have limited absorption at the wavelengths used for CO2 detection. The respiratory adapter may be manufactured, for example, using injection molding. However, other manufacturing methods may be contemplated.

[0068] Preferably, in all of the above embodiments, the surface of the gas cavity has an angle with respect to the beam direction of the light beam delivered through the end of the light guide when the adapter connector is connected to the breathing adapter. This allows for further reduction of the spectral background. Also, although not shown in Figures 5A-5E, the breathing adapter of all embodiments allows the beam delivered by the end of the light guide to enter the gas cavity and from the gas cavity to the photodetector without being substantially obstructed by any component of the breathing adapter. For example, the breathing adapter can be transparent for the preferred wavelength of light or can include a transparent window between the end of the light guide / photodetector and the gas cavity. Alternatively, the breathing adapter can provide an opening to the gas cavity that is closed by the adapter connector when the adapter connector is connected to the breathing adapter, and light can enter the gas cavity through this opening and also from the gas cavity to the photodetector.

[0069] Furthermore, in all of the above embodiments, the adapter connector may have a front portion made of a transparent material located in front of the end of the light guide and / or in front of the photodetector, i.e., located between the end of the light guide / photodetector and the gas cavity. This transparent front portion may be used to disperse the light beam provided by the end of the light guide, so that the diameter of the outgoing and returning light beams at the surface of the front portion is larger, making the light detection less likely to fail, for example due to light blocking by small dust particles.

[0070] In all of the above embodiments, a lens may be provided at the end of the light guide, the lens being preferably a GRIN lens. However, the lens may also be a commonly known spherical or aspheric plastic lens, for example part of the adapter connector. Furthermore, the plastic lens may be provided as part of the breathing adapter, specifically as part of the interface of the breathing adapter where the adapter connector is connected. Additionally or alternatively, in all embodiments, a lens, for example a small plastic collecting lens, may be provided in front of the light detector. This allows the effective size of the light detector to be increased. If the respiratory gas to be detected is CO2 and therefore the light provided by the end of the light guide is in the near infrared wavelength range, the light detector may be an InGaAs detector.

[0071] In the following, a very detailed embodiment of the adapter connector and the breathing adapter corresponding to the embodiment described with respect to FIG. 5C is exemplarily described in relation to FIGS. 6 to 8. In particular, FIGS. 6 and 7 show a simulation of the path of the light beam provided by the end of the light guide when the adapter connector is connected to the breathing adapter of this embodiment. The illustrated simulation was obtained using an optical ray tracing algorithm. The embodiment shown in FIGS. 6 and 7 exemplarily shows different measures that can be taken to avoid undesired reflections in the gas cavity that may cause interference effects and contribute to the spectral background of the measured optical signal. Furthermore, in FIGS. 6 to 8 some exemplary dimensions of the breathing adapter and the adapter connector are provided, where all length dimensions are provided in mm.

[0072] The first drawing of FIG. 6 shows an example of an embodiment of the breathing adapter described in relation to FIG. 5C and the light path followed by the light delivered by the end of the light guide in such an embodiment. The upper part of FIG. 6 shows a schematic view of the breathing adapter 601 in the yz plane, while the lower part of FIG. 6 shows a schematic view of the breathing adapter 601 in the xz plane. In this simulation, the wavelength of the near infrared light beam was simulated to be 2000 nm and guided to the breathing adapter 601 by a single mode fiber of the light guide 614. In this example, the end of the optical fiber 614 has an angle of 8° with respect to the y axis and with respect to the beam direction following the x axis in order to avoid back reflection of the beam into the fiber. Furthermore, in this example, a front part in the form of a glass window 617 having an angle of 8° with respect to the y axis, through which the light beam is transmitted, is provided. In this simulation, the glass is selected as BK7 type. Furthermore, the photodetector 615 is selected as an InGaAs near infrared photodetector also configured with an angle of 8° with respect to the y axis. In this example, the space between the front portion 617 and the detector 615 is filled with an optical gel 618 having a refractive index of 1.44 to avoid reflections between the front portion surface and the detector surface. In this example, the respiratory adapter 601 is formed from injection molded polycarbonate.

[0073] The light beam provided at the end of the light guide 614 enters the respiratory adapter 601 through a window in the surface of the respiratory adapter 601. This window has a wedge shape and has an inclined surface in the gas cavity with an angle of 7.5° to the y-axis to avoid undesired reflections that may result in interference effects. The beam is then reflected by a spherical mirror 632 placed in the gas cavity of the respiratory adapter 601 and focused on a detector. In this example, the radius of the spherical mirror is 16.0 mm. The reflective material of the mirror can be a metal layer, for example aluminum, or a dielectric multilayer coating. The spherical mirror 632 has an angle of 2.15° to the y-axis. The polycarbonate surface of the respiratory adapter 601 in front of the mirror has an angle of 5.7° to the y-axis. Also, the diameter of the detector is selected to be 0.2 mm.

[0074] As shown in the simulated measurement results in the lower right corner of Figure 6, in this configuration the light spot detected on the detector surface when light is provided by the end of the light guide is much smaller than the diameter of the detector. The diameter of the light spot is about 20 micrometers. The square detector has dimensions of 0.2x0.2mm, which results in a maximum tolerance of 0.1mm for the detector position, which makes it easier to manufacture the adapter connector and the breathing adapter.

[0075] FIG. 7 shows the same exemplary configuration of the adapter connector and breathing adapter as in FIG. 6, with the light path simulation simulating possible reflections of light at the detector surfaces. The upper part of FIG. 7 shows the breathing adapter configuration in the yz plane as above, and the lower part of FIG. 7 shows the breathing adapter configuration in the xz plane as above. As can be seen from this figure, such possible reflections do not strike the photodetector and therefore do not contribute to the spectral background. Further simulations can also show that for this exemplary configuration, any unintended reflected light by any of the breathing adapter surfaces does not reach the photodetector. This configuration therefore allows for a significant reduction in unwanted interference effects and spectral background.

[0076] FIG. 8 shows a more detailed exemplary embodiment of the respiratory adapter and adapter connector. In particular, FIG. 8 provides some exemplary dimensions of the respiratory adapter and adapter connector according to the present invention, with the length dimensions provided in the drawings being provided in mm. FIG. 8 shows exemplary dimensions of the respiratory adapter 801 and the adapter connector 820, with the configuration of FIG. 8 corresponding to the embodiment described in relation to FIG. 5C. Furthermore, some exemplary arrangements of the patch cable 810, the respiratory adapter 801, the adapter connector 820, the light guide 814, and the detector 815 are shown on the left side of FIG. 8. In general, in this configuration, it has been found to be advantageous for the length of the gas cavity in the direction of the light beam provided by the end of the light guide to be 7.7 mm. The respiratory adapter 801 shown in FIG. 8 refers to an injection molded polycarbonate respiratory adapter, with the respiratory adapter 801 being designed as a disposable product. The respiratory adapter 801 as shown in FIG. 8 is configured to be directly connected to the adapter connector 820 without providing further optical-electrical alignment. Photodetector 815 in this embodiment refers to an InGaAs near infrared detector. Due to the value of photodetector 815, patch cable 810 may be configured as a reusable product.

[0077] In general, all of the means for reducing the spectral background provided by the above configurations, such as the angles provided by the surfaces of the gas cavity, can be applied to any of the above embodiments of the respiratory adapter and adapter connector. Furthermore, while the dimensions provided are the preferred dimensions for the embodiment shown in the above figures, other dimensions can provide the same effect as above.

[0078] In the following, an exemplary embodiment of a respiratory module according to the invention is described in relation to FIG. 9. In FIG. 9, a respiratory adapter 901, through which respiratory gas is guided, and a patch cable 910 are shown in a schematic manner. The respiratory adapter 901 and the patch cable 910 may refer to any of the embodiments described above. The patch cable 910 is connected to a respiratory module 903, which in this case is shown as a capnography module via a module connector 913. In this embodiment, the respiratory module 903 comprises a light supply unit 931 for supplying light to the light guide of the patch cable 910. In this example, the light supply unit 931 refers to a VCSEL having a wavelength close to one of the CO2 absorption lines around 2 μm. The light provided by the VCSEL is guided to the light guide of the patch cable 910 and then through the light guide to the respiratory adapter 901. The light that is not absorbed by the respiratory gas in the gas cavity of the respiratory adapter 901 is detected by a photodetector integrated with the patch cable 910. The detection signal is then fed from the photodetector to the detection electronics 932, i.e. processing unit, of the respiratory module 903 via the electrical cable of the patch cable 910. Generally, in all embodiments, the electrical cable may be shielded or a preamplifier may be provided at or near the photodetector to improve signal quality.

[0079] Preferably, the wavelength delivered by the VCSEL is modulated at tens of kHz by modulating the injection current of the VCSEL. In this case, an electrical signal proportional to the CO2 concentration is received by lock-in detection using the second harmonic f2 of the modulation frequency. The advantage of using the second harmonic of the modulation frequency instead of the first harmonic to obtain a signal proportional to the CO2 concentration is that the second harmonic is less susceptible to offsets in the electrical signal. To compensate for the intensity drift of the VCSEL and the variable optical losses in the path to and within the breathing adapter, the electrical signal may be normalized to the DC f0 of the optical detection signal. To stabilize the temperature of the VCSEL, a thermoelectric cooling (TEC) unit may be provided near the VCSEL, for example in the VCSEL housing. The temperature of the VCSEL together with the current supplied to the VCSEL determines the wavelength of the light delivered. To stabilize the VCSEL to deliver light near the desired absorption line of the breathing gas, for example CO2, a control loop is provided using the third harmonic f3 signal, as shown in the schematic diagram of the electronics, i.e. processing unit 932. The third harmonic f3 signal crosses zero at the center of the absorption line of the respiratory gas. The processing unit 932 and the respiratory module 903 shown in FIG. 9 show an exemplary electrical processing scheme for this signal processing. However, other electrical processing schemes may be used, or the processing unit 931 may refer to a general electronic processing unit, such as a computing unit having software that allows the processing of the above signal processing. Furthermore, other signal processing schemes may be used to determine the gas concentration from the electrical signal provided by the photodetector. For example, instead of lock-in detection using the zero crossing of the third harmonic signal f3 and peak detection of the second harmonic f2 to determine the concentration of the respiratory gas, the wavelength of the light provided by the VCSEL may be swapped continuously over the wavelengths corresponding to the absorption lines and then fitted to a stored reference linear shape. The peak intensity of the resulting signal may then be derived and the center of the wavelength sweep may be determined and, if necessary, corrected based on subsequent sweeps.

[0080] Preferably, the VCSEL light passes through an isolator in the optical interface where the breathing module 903 and the module connector 913 are connected. This prevents optical feedback to the VCSEL from introducing laser noise and spectral background from the VCSEL unit.

[0081] 10A and 10B show nasal cannula configurations with patch cable connectors. These oronasal cannula configurations are suitable for diode laser capnography and allow accurate capnography waveforms to be recorded by taking care that the CO2 concentration in the cannula is equal to that in the respiratory air during a complete respiratory cycle.

[0082] More specifically, a cross section of a nasal cannula 1001 according to the invention is shown in FIG. 10A. During exhalation, a portion of the exhaled air passes successively through the prongs forming the inlet section 1002, the gas sensing cavity 1003, and the outlet section with the constriction 1004. During inhalation, air passes through the cannula in the opposite direction. The flow path is smooth, so no significant vortexes are generated during breathing, resulting in a uniform distribution of CO2 in the gas sensing volume. On both sides of the cannula, there are receptacles for patch cable connectors 1005. One patch cable connector incorporates a light guide and its exit face, a lens to focus the light, and an exit window. The light beam passes through the walls of the gas sensing cavity and the cavity. The other patch cable connector incorporates a window and a photodetector to detect the transmitted light. The inside of the cavity wall is coated to prevent scattering and absorption of light by water droplets. To increase the absorption length while keeping the overall volume small, the angle θ between the mean flow direction and the direction of the light beam in this embodiment is about 45°. The cannula is preferably injection molded from a plastic material that is transparent at the absorption wavelength of CO2. Polycarbonate may be used for this purpose. The inlet and outlet sections may be separate parts made of a different material than the cannula section with the gas sensing cavity. The inlet section with the prongs and the outlet section may be made of a soft material, for example silicone, and may be moved or fitted into the center section during manufacture.

[0083] FIG. 10B shows a cross section of a cannula 1011 suitable for nose and mouth breathing. During exhalation, a portion of the exhaled air passes successively through the prongs forming the inlet section 1012 and / or the mouth cap forming another inlet section 1016, the gas sensing cavity 1013, and the outlet section with the constriction 1014. In this design, the angle θ between the average flow direction and the beam direction in the gas sensing cavity 1013 is close to 10° to provide a long absorption path. The beam is reflected by a curved mirror 1017 on one side of the cannula and passes through the gas sensing cavity twice, which doubles the absorption length. The patch cable connector 1015 incorporates the window, the fiber and its exit face, and the photodetector. In this case, there is no lens in the connector. The diverging beam from the fiber is collimated by a mirror that is part of the injection molded cannula. After molding, a reflective metal layer can be evaporated onto the surface of the curved mirror. The flow direction in the gas sensing cavity is the same for mouth and nose breathing. Because the outlet port 1014 is located away from the nose and mouth, during inspiration, the air in the gas sensing cavity is replaced by ambient air with low CO2 concentrations, resulting in a capnogram close to the zero level.

[0084] Both configurations require that the angle between the respiratory flow and the direction of the light beam is less than 90°. The cannula must contain both an inlet section to effectively sample the nasal or oral flow and an outlet section to limit the exchange of carbon dioxide CO2 by diffusion. The flow resistance of the central gas-sensing cavity is small compared to the inlet and outlet sections, and the cavity has a larger cross section in the flow direction. For a cannula suitable for nasal and oral breathing, the flow path has the same flow direction through the gas-sensing cavity for nasal and oral breathing, and the outlet section of the flow path is away from the nose and mouth.

[0085] According to another embodiment of the present invention, there is provided a respiratory adapter receptacle having a receptacle insert in the form of a gel or soft rubber at the interface between the adapter connector of the patch cable and the respiratory adapter, the gel or soft rubber contacting the adapter connector window after insertion and having a refractive index close to that of the front window of the adapter connector and also close to that of any fingerprints that may be present.

[0086] FIG. 11 shows an embodiment with gel. During manufacture, a drop of high viscosity gel (1111) is placed in the cannula receptacle (1101). The cannula / airway adapter is then packaged to keep the optical interface free of dust. Before use, the cannula is opened and a patch cable plug (1120) is inserted and secured in the cannula receptacle (1101). During insertion, the window in the front part of the plug is pressed into the gel (1111) and direct contact between the window and the gel is established. Excess gel (1111) is pressed into the excess channel (1112). At a wavelength of 2 μm, the gel has a small absorption and a refractive index of about 1.5, close to that of silica, window epoxy / glass, and the inner side of the cannula, e.g., polycarbonate. Various polydimethylsiloxane PDMS silicone compositions meet these requirements. Alternatively, gelled colloidal silica having a sufficiently small particle size, or a mixture of colloidal silica and silicone may be used.

[0087] Alternatively, the receptacle insert is a flexible rubber. For example, PDMS silicone can be prepared with various crosslink densities. In this way, the silicone can be made into a flexible rubber material suitable as an adaptive insert. By injection molding, an adaptive insert is formed with the appropriate dimensions and placed in the cannula receptacle during assembly of the cannula. The flexibility of the silicone and the dimensions of the adaptive insert are adjusted so that after inserting the plug into the receptacle, direct contact is established between the connector plug window and the adaptive insert. To allow for expansion during insertion, a small expansion volume can be present in the cannula along the circumference of the receptacle. The application of a porous flexible silicone rubber allows the silicone to be impregnated with a fluid. Preferably, the fluid is of low volatility and remains in the adaptive insert during storage of the cannula. When the connection between the patch cable and the cannula is established, the fluid is forced against the connector plug window, creating an interface without an air layer.

[0088] Another option is the diffusion receptacle insert. Light scattering particles, for example silica particles with a size comparable to or somewhat larger than the wavelength, are incorporated into the silicone rubber. When a light beam traverses an adaptive insert made of such a material, the adaptive insert acts as a diffuser and the coherence of the laser beam is reduced. The advantage of the diffusion receptacle insert is that it improves the quality of the capnography signal by reducing the interference of the laser light with the walls of the gas sensing cavity and thus the spectral background in the absorption signal.

[0089] 4, the light unit and the processing unit, e.g., detection electronics, may not be part of the respiratory module 903 but may be part of the module connector 913. In this case, the respiratory module 903 may only provide an electrical interface to the module connector 913, an interface capable of providing electrical power for the light supply unit and the processing unit, and may further be provided with a data interface, an interface capable of providing a data signal indicative of the concentration of the respiratory gas from the module connector 913 to the respiratory module 903.

[0090] In the above embodiment, the patch cable, respiratory adapter, and respiratory module are configured to detect CO2 as a respiratory gas, however, in other embodiments, the patch cable, respiratory adapter, and respiratory module, specifically the optical light guide and light source, may be configured to detect other respiratory gases, such as O2 or volatile anesthetic agents.

[0091] Other variations of the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention from the drawings, the disclosure, and the appended claims.

[0092] In the claims, the terms "comprise" and "include" do not exclude other elements or steps and the singular does not exclude a plurality.

[0093] A single unit or device may fulfill the functions of several items recited in the claims. The mere fact that several measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0094] Procedures such as the determination of the concentration of respiratory gas based on the signal provided by the photodetector, which are performed by one or several units or devices, may be performed by any number of other units or devices. For example, these procedures may be performed by a single device. These procedures may in particular be implemented as program code means of a computer program and / or as dedicated hardware.

[0095] Any reference signs in the claims should not be construed as limiting the scope.

[0096] The present invention relates to a patch cable for connecting a respiratory module to a respiratory adapter, e.g., part of a capnography system. The patch cable comprises: a) a module connector; b) an adapter connector including a light detector; c) a light guide; and d) an electrical cable for transmitting an electrical detection signal generated by the light detector from the adapter connector to the module connector. The adapter connector is configured such that an end of the light guide is positioned to provide light into a gas cavity of the respiratory adapter. The adapter connector is configured such that the light detector detects light provided by the end of the light guide that has interacted with gas provided in the gas cavity when the adapter connector is connected to the respiratory adapter. This can improve the accuracy of respiratory gas detection.

Claims

1. A patch cable for connecting the breathing module to the breathing adapter, a module connector connecting a first end of the patch cable to the respiratory module; an adapter connector connecting a second end of the patch cable to the respiratory adapter, the adapter connector including a photodetector; and a light guide for directing light from the module connector to the adapter connector, the adapter connector being configured such that an end of the light guide is positioned to provide the light into a gas cavity contained in the respiratory adapter when the adapter connector is connected to the respiratory adapter; and an electrical cable transmitting an electrical detection signal generated by the photodetector from the adapter connector to the module connector; the adaptor connector is configured such that a surface of the photodetector on which light is detected is disposed at an angle with respect to a first beam direction of light detected by the photodetector, the first beam direction of light detected by the photodetector being a beam direction of a spatial average of all beams of light impinging on the photodetector, and the angle between the detection surface of the photodetector and the beam direction being an angle between the first beam direction and a normal to the detection surface; the surface at the end of the light guide is at an angle to a second beam direction of light provided by the end of the light guide into the gas cavity when the adapter connector is connected to the breathing adapter, the second beam direction of light provided by the end of the light guide is a beam direction of a spatial average of all beams of light provided by the end of the light guide, and the angle between the surface at the end of the light guide and the second beam direction is an angle between the second beam direction and a normal to the surface; The adapter connector is configured such that when the adapter connector is connected to the respiratory adapter, the optical detector detects light provided by the end of the light guide that has interacted with gas provided in the gas cavity, and the electrical detection signal generated by the optical detector is indicative of a concentration of respiratory gas from a patient provided in the gas cavity.

2. 2. The patch cable of claim 1, wherein the adapter connector comprises a first connector portion and a second connector portion, the first connector portion comprising the light detector and the second connector portion comprising the end of the light guide, the first connector portion and the second connector portion connecting the adapter connector to the respiratory adapter such that when the adapter connector is connected to the respiratory adapter, light provided through the end of the light guide that passes through the gas cavity of the respiratory adapter is detected by the light detector.

3. 2. The patch cable of claim 1, wherein the adapter connector has a U-shape, the end of the light guide is disposed on one side of the U-shaped adapter connector, and the photodetector is disposed on an opposite side of the U-shaped adapter connector, and when the adapter connector is connected to the respiratory adapter, light provided through the end of the light guide that passes through the gas cavity of the respiratory adapter is detected by the photodetector.

4. The patch cable of claim 1 , wherein the end of the light guide includes a lens integrated into the adapter connector.

5. 5. The patch cable of claim 1, wherein the adapter connector further comprises a front portion formed from a transparent material, the front portion being positioned between the end of the light guide and the gas cavity and / or between the light detector and the gas cavity when the adapter connector is connected to the breathing adapter.

6. The module connector further comprises: a light supply unit that supplies light through the light guide; and a processing unit receiving the electrical detection signal provided by the optical detector, the processing unit generating a data signal representative of the concentration of the respiratory gas based on the electrical detection signal.

7. a respiratory adapter including a gas cavity, said respiratory adapter and said gas cavity configured such that when said respiratory adapter is placed in operative contact with a patient's mouth and / or nose, respiratory gas from the patient can enter said gas cavity; A patch cable according to claim 1 for connecting a respiratory module to the respiratory adapter; and the respiratory module processes data indicative of a concentration of a respiratory gas based on the signal provided via the patch cable.

8. 8. The respiratory gas detection system of claim 7, wherein the respiratory adapter provides at least one reflector as part of the respiratory adapter on a side of the gas cavity opposite a connection side where the adapter connector can be connected to the respiratory adapter, the adapter connector being configured such that when the adapter connector is connected to the respiratory adapter, the end of the light guide and the light detector face in substantially the same direction, and light provided by the end of the light guide into the gas cavity and reflected by the at least one reflector provided as part of the respiratory adapter is detected by the light detector.

9. A respiratory gas detection system as described in claim 7 or 8, wherein the respiratory adapter is further connected to the adapter connector such that light provided by the end of the light guide can be detected by the light detector of the adapter connector after passing through the gas cavity to interact with the respiratory gas provided within the gas cavity.

10. 10. The respiratory gas detection system of claim 9, wherein a surface of the gas cavity is at an angle relative to a beam direction of a light beam provided through the end of the light guide when the adapter connector is connected to the respiratory adapter.

11. 11. The respiratory gas detection system of claim 9 or 10, wherein the respiratory adapter includes at least one reflector, the at least one reflector being positioned such that when the adapter connector is connected to the respiratory adapter, light provided by the end of the light guide is reflected by the at least one reflector and detected by the light detector after said reflection at the at least one reflector.

12. 12. A respiratory gas detection system according to any one of claims 9 to 11, wherein the respiratory adapter includes both an inlet port for sampling nasal and / or oral flow and an outlet port for limiting exchange of carbon dioxide by diffusion, and the gas cavity has a larger cross-section at the gas sensing cavity than at the inlet and outlet ports.

13. 13. A respiratory gas detection system according to any one of claims 9 to 12, wherein a flow direction within the gas sensing cavity of the respiratory adapter has an angle of less than 90° with respect to the beam direction of light.

14. 14. A respiratory gas detection system according to any one of claims 9 to 13, wherein an interface between the adapter connector of the patch cable and the respiratory adapter is provided with a receptacle insert in the form of a gel or soft rubber.

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