BRPI0702864A2 - gas measurement system - Google Patents

Abstract

GAS MEASUREMENT SYSTEM. A gas measurement system (100) of this invention includes a housing (250) adapted to be mounted on an air passage adapter, and a luminescence cooling gas measurement set (236) arranged in the housing. The luminescence cooling gas measurement set includes a source (243) arranged in the foreground, and at least one detector (238, 239) also arranged in the foreground. A filter (233) is provided by at least one detector for passing radiation wavelengths related to cooling luminescence and substantially blogs others. An optical protector (234) is arranged around at least part of the source.

Description

"GAS MEASURING SYSTEM" PRIORITY CLAIM

In accordance with the requirements of 35 U.S.C. §120 / 365, this application claims the benefit of application US11 / 368.832, filed March 6, 2006.

TECHNICAL FIELD

The present invention relates to a mainstream respiratory gas metering system with integrated signal processing and improved optical design, and a method of mounting such a system.

BACKGROUND OF THE INVENTION

Respiratory gas measurement systems include gas sensing, measurement, processing, communication and display functions. They are considered to be both deviation, ie side current, and non-deviation, ie main current. A bypass gas metering system transports a portion of the sampled gases from the sampling site, which is typically a breathing circuit or the patient's airway, through a sampling tube to the gas sensor where the dog constituents are measured. A non-bypass or mainstream gas metering system does not carry gas away from the breathing circuit or airway, but measures gas constituents through the breathing circuit using a gas sensor arranged in the breathing circuit.

Conventional mainstream gas metering systems include gas sensing, metering components and signal processing required to convert the detected or metered signal, for example, a voltage to a value such as transmittance that can be used by the system to determine a constituent. of a gas being measured. In a conventional mainstream gas metering system, a gas sensor is coupled to a sample detecting cell that is placed in the breathing circuit. The gas sensor located on the airflow adapter disposed in the breathing circuit only includes the components required to produce a signal corresponding to a property of the gas to be measured. Placing the sample detecting cell directly into the breathing circuit results in a "fast" waveform that reflects in real time the partial pressure of the measured gas, such as carbon dioxide or oxygen, into the airway. The sample cell, which is also referred to as a crucible or airflow adapter, is located in the. respiratory gas flow, preventing the need for sampling and cleaning as required in a side-by-side gas metering system.

For a conventional gas metering system that is capable of measuring carbon dioxide, the gas sensor includes a source that emits infrared radiation, which includes a carbon dioxide absorption band. Infrared radiation is emitted in a direction that is normal to the flow path of the respiratory gas stream. Carbon dioxide inside the sample gas absorbs radiation at some wavelengths and passes other wavelengths. Conventional gas sensor includes photodetectors that measure transmitted radiation.

For gas metering systems that are capable of depleting oxygen using deluminescent cooling metering techniques, the gas sensor may include an excitation source that emits visible radiation, which excites a light-sensitive chemical disposed on or within a substrate. , and a detector, which measures the radiation emitted by the chemist upon exposure to oxygen. Gas concentration can be determined from the luminescence response time using known correlations, such as the Stern-Volmer ratio.

A conventional mainstream host system contains the electronics that control the emitter on the gas sensor, and provides the measurement functions of the gauges based on the output signals from the detector.

Mainstream gas metering systems known in the art transmit analog signals over a cable, typically 6 to 8 feet (1.82 to 2.43 meters) in length, between the host system and the gas sensor and , as a whole, are subject to electromagnetic interference (EMI).

This is particularly important given the tendency towards compliance with the increased levels of electromagnetic immunity in international medical device standards. An example of such conventional main current measuring systems is shown in US Patents 4,914,720 issued to Knodle et al. e5,793,044 issued to Mace et al.

With the metering and signaling electronics located in the host system, existing mainstream gas metering systems are complex and easy to interface with host systems. The host system conventionally includes a set of circuits for performing functions such as (1) creating synchronization signals; (2) provide pulsatile energy for a solid state infrared emission; (3) accurately measuring and controlling the temperature of infrared detectors (4) measuring and controlling an airway adapter heater; (5) signal conditioning including filtering and programmable adjustment; and (6) vigilant circuitry to prevent accidental destruction of the infrared emitter.

Additionally, to be admitted for clinical use, a mainstream gas metering system must be designed in a robust manner such that it is not affected by typical mechanical misuse and environmental variations in temperature and humidity. The instrument, or at least the gas measurement system part of the instrument, should be small and light in weight so as not to interfere with patient movements, or other medical equipment or treatments. In order to achieve the goals of being small and light, the optical part of the gas metering system must also be designed in such a way that it occupies as little space as possible and weighs as little as possible.

Given these known complexities of conventional gas metering systems, it is desirable to provide a small mainstream gas metering system that is small, lightweight and simpler to interface with host systems. It is also desirable for such a system to provide improved mounting methods over known gas metering systems.

DISCLOSURE OF INVENTION

Thus, it is an object of the present invention to provide an optical bench that overcomes the optical bench deficiencies of known luminescence-based gas measurement systems. This objective is achieved in accordance with the present invention by providing a gas metering system assembly including a housing adapted to be mounted on an airway adapter and a cooling gas metering assembly. luminescence arranged in the housing. The luminescence cooling gas metering assembly includes a radiation source arranged in the foreground, and at least a detector also arranged in the foreground. A filter is provided over at least one detector for passing radiation-related radiation wavelengths of light and substantially blocking others. An optical shield is arranged around at least part of the source. This configuration provides a relatively compact configuration for the luminescence cooling gas measurement set.

These and other objects, features and features of the present invention, as well as the methods of operation and functions of related structural elements and the combination of parts and workmanship, will become more apparent upon consideration of the following description and claims. appended with reference to the attached drawings, all of which form a part of this specification, where like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are provided for illustration and description purposes only and are not intended as a definition of the limits of the invention.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a perspective view of a gas metering system coupled to a host system and configured to be removably attached to an air duct adapter mounted with the components of a patient breathing circuit according to FIG. with the principles of the present invention;

Figure 2 is a perspective view of the gas metering system configured to be coupled to a host system;

Figure 3 is a perspective view of the gas metering system configured to be removably attached to an air passage adapter;

Figure 4 is an exploded view of a gas metering system with a cover and electro-gas gas metering system shown;

Figure 5 is an exploded view of an electromagnetic gas metering system assembly;

Figure 6 is an exploded view of a gas metering system with the cover, electronic circuit boards and optical gas metering assembly shown; Figure 7 is an exploded view of the gas metering optic assembly with the structural base element, detector assembly and source assembly shown;

Figure 8 is an exploded view of the detector assembly;

Figures 9 and 10 are exploded views of the optical housing assembly of the detector assembly;

Figure 11 is a cross-sectional view of the assembled optical housing assembly;

Figure 12 is an exploded view of the front assembly;

Figure 13 is an exploded view of the emitter housing portion of the source assembly;

Figure 14 is a cross-sectional cross-sectional view of the gas metering system mounted along line 14-14 of Figure 4;

Figure 15 is a plan view of the assembled components of the gas metering system prior to placement in the housing;

Fig. 16 is a radius plot of the optical path within the gas metering system in accordance with the principles of the present invention;

Figure 17 is a block diagram of the gas metering system in accordance with the principles of the present invention;

Figure 18 is a schematic diagram of a four channel optical system in a linear configuration for the detector assembly optical assembly according to the principles of the present invention;

Figure 19 is a graph showing a modalities of beam dissociator wavelengths relative to filter wavelengths;

Figure 20 is a schematic diagram of a four channel optical system in a zigzag configuration;

Fig. 21 is a schematic diagram of a four channel optical system in a square array configuration;

Fig. 22 is a schematic diagram of a four channel optical system in a linear lens configuration system;

Figure 23 is a schematic diagram of a four-channel zigzag optics with lens configuration;

Fig. 24 is a schematic diagram of a four-channel optical system in a footprint configuration;

Fig. 25 is a schematic diagram of a four channel optical system in a serpentine configuration;

Fig. 26 is a schematic diagram of a four channel optical system in a tunnel configuration;

Figure 27 is a side view of a four-channel optical system in a linear configuration;

Figure 28 is an exploded view of an optical assembly part of a gas metering system according to the principles of the present invention; and Fig. 29 is an exploded view of the luminescence cooling metering circuit board in the gas metering system of Fig. 28.

BEST MODES FOR CARRYING OUT THE INVENTION

A gas metering system 100 according to the principles of the present invention includes all the signal and data processing required to produce continuous values of a partial pressure or concentration of a gas flowing through a flow-through airflow adapter. with an airway of the patient. The measuring system is located in a "measuring head" that fits an air passage adapter. The measuring system includes the electronic circuitry required to measure and compute a continuous value for infrared absorbing gases, such as carbon dioxide, and luminescent cooling gases, such as oxygen, and the interface of the metering system. gas to a host system. In an exemplary embodiment, the gas metering system 100 acquires and processes analog signals, then transmits patient and digitized waveform parameters via an interface cable 120 as a serialized data stream.

The gas metering system of the present invention eliminates the need for an additional electronic component board within a host system that would otherwise be required to process the detector signal output, thereby preserving space within the host system and reducing costs. to the end user. Because of design efficiencies and miniaturization, the resulting gas metering system is almost as small and light as existing mainstream gas metering sensors. The addition of signal processing without any significant increase in Size or weight is particularly important in applications where the gas metering system is employed with an airflow adapter near the patient face at the distal end of an endotracheal tube or nasal cannula to monitor a patient's breath. .

An exemplary embodiment of an airflow adapter 40 and a gas metering system 100 constructed in accordance with and incorporating the principles of the present invention is shown in Figures 1-3. Conventional gas metering systems do not locate the electronic signal processing and control components in the gas metering system, but they do locate any such feature in the host system. The present invention takes advantage of the highly integrated digital signal processing (DSP) technology to perform many of the complex electronic interface functions within a small single chip processor that includes program and data storage as well as analog to digital conversion.

Many of the efficiencies achieved in the integrated respiratory gas measurement system are a consequence of relocating the electronics into the gas measurement system. For example, this relocation has affected design aspects of interface cable 120, such as conductor quantity, protection requirements, and therefore cable thickness, weight, and cost. The cable requires fewer conductors and is therefore smaller, lighter and more flexible providing less loading and dragging forces on the sensor. The exemplary mode uses 7 wires and one shield, while conventional devices use 16 wires and two shields.

The present invention has several additional advantages over conventional gas metering systems, including flexible / simplified interconnection with a host system 70, and enhanced immunity to radio frequency interference. With a simplified hardware and software interface, the 70 host system requires only a simple, small wired connector for a serial port, and a mains voltage coupling. In clinical application, adding weight to the patient circuit near the ET tube is always a concern, especially for pediatric and neonatal applications. The present invention offers a significant improvement in this regard because the resulting drag potential weight of the cable can be reduced. Existing host system cables are thicker in diameter, heavier and less flexible.

Conventional gas metering systems, with components in or near the patient's airway, often have difficulty meeting the existing 3-volt / meter immunity standard. Upgrades of international medical device electromagnetic compatibility standards have raised this test level to up to 20volts / meter. Conforming these standards to existing designs would be very difficult and expensive because of the susceptibility to interference from analog signals transmitted over a cable. In the present invention, the need to transmit analog signals on the cable to the host system is eliminated and all components and signals subject to the RFI are located near the sensing elements in the gas metering system.

Eliminating the need for all complex external interface electronic components results in exceptionally reduced system cost. Efficient use of interconnection technologies such as rigid / flexible circuit boards and other manufacturing efficiencies results in a total system cost that is less than the cost of existing mainstream gas metering systems. Alone.

The integration of the gas metering system's metering and signal processing electronics increases the waste heat generated within the 100 gas metering system. The compact nature of the design requires careful consideration of the thermal design. For example, the gas metering system 100 is configured to allow the lost heat produced by the emitter and the electronic components of the gas metering system to heat the airway adapter windows to reduce fogging. These features of the present invention allow the ceramic heater (also known as the cabinet heater) that has been used in conventional gas metering systems to be eliminated. In addition, the elimination of the ceramic heater, along with other design efficiencies, has allowed the total energy consumption for the invention to be reduced from approximately 5 Watts (W) to 1.25 W.

Figure 1 is a perspective view of the gas metering system 100 coupled to the host system 70 and configured to be removably attached to the airflow adapter 40, which is mounted with the components of a patient breathing circuit 20. The adapter 40 is typically mounted in the breathing circuit 20 between an elbow 25, which is a connection to a patient interface, such as an endotracheal mask or tube, and the "Y" piece 30 which is connected to a positive depression generator such as a fan. Host system 70 supplies the power to the gas metering system 100, receives the gas concentration signal and derived measurements produced by the gas metering system, and where the gas concentration signal is the carbon dioxide concentration, displays measurements such as: (a) concentration of carbon dioxide in patient exhales, (b) inspired carbon dioxide, (c) respiration rate and (d) final periodic carbon dioxide. Similarly, where the gas concentration signal is the oxygen concentration signal, host system 70 displays measurements such as: (a) the oxygen concentration in patient exhales, (b) inspired oxygen, ( c) respiration rate and (d) final periodic oxygen.

As noted above, cable 120 communicates gas metering system assembly 100 with host system 70. A distal end 110 of cable 120 is securely and removably connected to the host system.

A proximal end 123 of cable 120 includes a voltage reinforcing element 130 that allows voltage to be applied to cable 120 without affecting the conductor within it. Power is supplied to the gas metering system from the host through the cable. However, the present invention also considers that the gas metering system may be battery powered with a separate integrated battery module and wirelessly communicate its data to the host system, thereby eliminating the need for cable 120. Wireless communications using known technical protocols such as Bluetooth, Zigbee, UWB used in Body Area Networks (BAN) and Personal Area Networks (PAN) are considered. The gas metering system may also be connected via a cable to an interconnecting apparatus which integrates the signals from the gas metering systems with another physiological metering.

End sections of Airway Adapter 40 (Figures 1 and 3) are designed for connection to patient breathing and interface systems. For example, the airway adapter may be disposed between an endotracheal tube (not shown) inserted into the patient's trachea and the breathing circuit of a positive pressure generator or ventilator 75. The gas metering system 100 in exemplary embodiment , is used to measure a patient's carbon dioxide and oxygen levels. The particular airway adapter 40 illustrated in Figures 1 and 3 is not in itself part of the present invention. As such, the present invention considers that the gas metering system of the present invention may be used with any conventional air duct adapter, including luminescence absorption or cooling adapters. An adapter that has been adapted to measure gases by both infrared absorption and luminescence cooling is disclosed in US patent application 09 / 841,451 to Mace et al., Publication US 2002/0029003 (the "application 451"), whose contents are incorporated herein by reference. The air flow adapter 40 is typically molded from polycarbonate or a comparable polymer.

In an exemplary embodiment of the present invention shown in FIGS. 3 and 14, the air passage adapter 40 has a generally parallelepiped shaped central section 42 and two cylindrical end sections 44 and 46 with a sampling passage 47 extending end-to-end. through the adapter. End sections 44 and 46 are axially aligned with central section 42. Center section 42 provides a seat for gas metering system 100. An integral U-shaped frame element 48 positively locates gas metering system 100 longitudinally on the adapter and also on that transverse direction indicated by the arrow 50 in figures 1 and 3.

Arrow 50 also shows the direction in which the air flow adapter 40 is displaced when mounted on the gas metering system 100. The openings 52, 53 and 54 are formed in the central section 42 of the air flow adapter. 40. With gas metering system 100 mounted on the airway adapter, apertures 52 and 54 are aligned along an optical path 56 as shown, for example, in Figure 14. The optical path 56 extends from a source or emitter assembly 400 in the gas metering system 100 transversely to the airway adapter 40 and through the gas or gases flowing through the airway adapter. The optical path continues from the airway adapter to a detector assembly 300 in the gas metering system 100. To prevent gases flowing through the airway adapter 40 from escaping through openings 52 and 54 without acceptable attenuation of radiation. infrared through the optical path 56, and to keep foreign material away from the interior of the airway adapter, these openings are typically sealed by the infrared transmission windows 58 and 60. In addition, the aperture 53 is covered by a screen. 49. In physical communication with window 49 and located within the airway adapter 40 is a sensing film with a light-sensitive chemical. This chemical emits radiation in response to an excitation when the chemical is exposed to a gas such as oxygen. It should be understood that the airway adapter may include one or more of the openings 52, 53 and 54, together with one or more gas metering techniques using these openings.

Fig. 4 is an exploded view of the gas metering system 100 which includes a polymeric cover 210 and an electromagnetic gas metering assembly 220. The electromagnetic gas metering system assembly 220, which is perhaps better 4 and 7, includes the following components: a) an infrared radiation source assembly 400 (shown in more detail in Figures 12-13), b) an infrared radiation detector assembly 300 (shown more details in figures 8-11), and c) an optional luminescence cooling metering circuit board 235. In the gas-mounted metering system, voltage gauge 130 is retained in place by grids 214 and 252 provided on a base 250. and in the coverage210. Wall 214 matches wall 252 when the cover is attached to the base, which is accomplished using any conventional technique, such as a biting or friction locking configuration.

The electromagnetic measuring system assembly 220 shown in Figs. 5-6 assembled with a flexible circuit 230, a bracket 232, a luminescence cooling metering circuit board 235, and an optimally indicated assembly 240, which includes the optical elements for the gas metering system. The source and detector assemblies in the optical assembly are coupled to the U-shaped base 250 and mechanically and electrically connected to the flexible circuit board, which is folded around these assemblies and fixed to the 250 base. The performance of the active components of the gas metering system is tested as a unit rather than individually prior to assembly. As a consequence, it is not necessary to wait until a degas measurement system is fully assembled to determine if it will meet performance specifications. The result is significant cost savings, an objective that is further enhanced by reduced wiring and a significant reduction in assembly cost.

Fig. 5 is an exploded view of the electrototic gas metering assembly 220 with flexible circuit 230, the bracket 232, and the luminescence cooling metering circuit board 235 separated from the gas metering system assembly 240. FIG. Flexible circuit 230 comprises the rigid plate portions 225, 226, 227 and 228 (see Figure 15). The rigid parts are joined together by the flexible parts. The flexible circuit board includes the analog and digital circuitry required to drive the infrared source and to convert signals from the detector assembly to output values for infrared absorbing gases such as carbon dioxide, and / or to convert signals from the cooling set. luminescence in output values for gases such as oxygen. The 235 circuit board includes circuitry and optics components for oxygen measurement by luminescence cooling techniques. Optical assembly 240 includes detector assembly 300, source assembly 400, and flexible heater circuit 245 for controlling the temperature of the oxygen film. The flexible heater circuit 245 is mounted on the gas metering optics 240 at the top of the "U" shaped base 250. The pins 246 at the distal end of the flexible heater circuit 245 are inserted into the corresponding teeth. holes 237 in the end portions of the luminescence cooling metering circuit board 235 prior to brazing. Similarly, pins 381 of detector flexible point connection 380 are inserted into corresponding holes 231 along an edge of plate portion 226 of flexible circuit 230.

Fig. 6 is an exploded view of the gas metering system 100 showing the cover, the electronic circuit boards and the optical metering system assembly.

Electromagnetic gas metering system assembly 220 with flexible circuit 230, bracket 232, and circuit board 235 is shown separate from the optical gas metering system assembly 240.

Figure 7 is an exploded view of the gas metering system optic assembly 240 showing structural base member 250, detector assembly 300, and source assembly 400. Base element 250 of gas metering system 100 supports the source assembly 400 in a source assembly compartment 253 and supports the detector assembly 300 in a detector assembly compartment 254. A generally rectangular gap 66 is disposed between compartments 253 and 254 The gap 66 is configured to fit the center section 42 of the through-pass adapter 40. Defined largely by the sidewalls and edges of the base member 250, two pairs of complementary cavities in a first end section 258 and a second section. 257 cooperate to define the infrared radiation source compartment 253 and the infrared radiation detector compartment 254, respectively. The base measuring system step 250 may be molded from a polycarbonate or any other suitable polymer. In the exemplary embodiment illustrated, the base member 250 has a flat side wall and an integral edge oriented at right angles to the side wall.

A source aperture 256 is defined in a housing wall to provide an optical path for radiation from the source assembly 400 to enter the sample cell portion of the airway adapter. A detector aperture 255 is defined in a housing wall to provide an optical path for radiation from exiting the air passage adapter to reach detector assembly 300. In the illustrated embodiment, a luminescent cooling aperture 260, the which corresponds to the aperture 53, is also provided in the housing to measure aluminescence of oxygen-cooled material in the sample gas. It is to be understood that the deluminescence cooling feature of the present invention and the absorption feature of the present invention may be used alone or in combination. Thus, depending on whether one or both of these gas metering techniques are used, apertures 255, 256 and 260 may be eliminated.

Fig. 8 is an exploded view of the detector assembly 300 of the gas metering system 100 and Fig. 9 is an exploded view of an optical detector assembly 350. Detector assembly 300 includes detectors 340 and 345 mounted on a heatsink. 330, a heatsink spacer 320, and a detector assembly circuit board 310. The heatsink 330 is coupled to the heatsink spacer 320, which is attached to a circuit board. 310. The resulting support assembly 325 is mounted to the detector optical assembly 350 by the alignment holes 335, 336, and 337 on an optical block 370 with corresponding heat sink locating pins 330. The optical assembly Detector 350 includes optical components such as lens 364, filters356 and 358, mirror 354 and beam splitter 352, and is mounted with detector holder assembly 325.

Mounted on the heatsink recesses 330 are the data and reference detectors 340 and 345, which are aligned in the same plane (i.e. coplanar), thus allowing more effective temperature regulation of the detectors. These detectors are preferably fabricated with lead selenide detector elements, because of the sensitivity of this material to infrared radiation having wavelengths that are suitable to be of interest. In addition, lead selenide reference data detectors 340 and 345 are extremely temperature sensitive. Therefore, it is critical that these two detectors are kept at the same temperature, preferably within a tolerance of no more than 0.02 ° C. Detectors 340 and 345 are maintained at the selected operating temperature by a detector heating system including detector heating elements 391 and 392, a temperature monitoring thermistor (not shown), and an operating circuit. / control (not shown), which is located on the detector assembly circuit board 310 and flexible circuit 230.

Detectors 340 and 345 are connected to detector assembly circuit board 310 to which a biasing voltage is applied across portions of infrared dimming elements configured and sized in the same manner as detectors. The gaps between the detectors and the contour of the detector receiving recesses in the isothermal support serve to electrically isolate the detectors from the conductive isothermal support.

A thermistor (not shown) is positioned to be centrally located in a slot 322 of the heat sink spacer 320. The heating elements 391 and 392 are located at the ends of the heat sink 330e and are in close contact with each other. the heat sink. Heating elements 391 and 392 include a flexible circuit portion having a distally located surface mount resistor for heat delivery.

The two pins 388 and 389 are provided on the heating elements to connect them to the detector assembly circuit board 310. The flexible circuit portion of the heating elements 391 and 392 is placed in close contact with the heat sink. 330. In the exemplary embodiment, an epoxy, preferably with a high thermal conductivity, is employed to secure the flexible circuit portion of one of the heating elements to the heat sink30. Pins 388 and 389 of heating elements 391 and 392 insert into corresponding holes 386 and 387 in the detector assembly circuit board 310. A flexible detector jumper 380 interfaces the circuit assembly circuit board. detector 310 with plate portion 226 of flexible circuit 230. Pins 382 of detector flex bridge 380 are inserted into corresponding holes 383 along an edge of detector circuit board 310. Pins 381 of the detachable detector jumper 380 are inserted into the holes 231 of the flexible circuit board part 230.

Optical detector assembly 350 will be described with reference to Figures 9-11. Optical detector assembly 350 includes beam splitter 352, mirror 354, filters 356 and 358 and detector lens 364. The beam splitter has a generally para-parallelepiped configuration. This component is made of a material such as silicon or sapphire, which is essentially transparent to electromagnetic energy at wavelengths of interest. The exposed front surface of the defect dissociator is completely covered with a coating capable of reflecting that electromagnetic energy colliding with the beam dissociator having a wavelength greater than a selected value. In the exemplary illustrated embodiment of the invention, the coating will reflect energy for the data filter 356 and data detector 340 having a wavelength greater than about 4 microns. The shortest wavelength energy is instead transmitted through beam splitter 352 to mirror 354 and reference filter 358 and reference detector 272.

The beam dissociator 352 is fixed in place by epoxy or by other means of gluing the defect protrusion dissociator 351 which is integral to the optical block 370. This exactly positions the beam dissociator 352 within the optical block 370 with the advantage that subsequent adjustments of the beam decoupler orientation are not required. Similarly, mirror 354 is fixed in place by means of epoxy or otherwise by gluing the mirror to protrusion 353, which is also integral with optical block 370. Also, the electromagnetic assembly of the present invention has a focal optimized length; which makes it possible to employ a smaller and cheaper gas metering system detector set.

The bandpass filters 356 and 358 limit the infrared radiation energy reflected by and transmitted from the beam splitter 352 and collide with the data and reference detectors 340 and 345 for energy at selected bandwidths. In the exemplary embodiment of the present invention and discussed in the drawing, reference detector filter 358 is nominally centered on a 3.7 micron wavelength. A filter such as this transmits maximum energy near the carbon dioxide band absorbed by data detector 340. This maximum energy absorption at an adjacent bandwidth is selected such that the output of reference detector45 will be at least as large as the output. detector 340. This notably contributes to the accuracy of the gas concentration indicative signal subsequently obtained by providing the data and reference signals.

The data detector bandpass filter 356 is nominally centered at a wavelength of 4.26 microns. The carbon dioxide absorption curve is reasonably narrow and strong, and the bandpass filter 356 centers the transmission band within that absorption curve. Therefore, if there is a change in carbon dioxide level (s) gas (s) being analyzed, the maximum modulation for a given change in carbon dioxide level is obtained. Data and reference bandwidth filters 356 and 358 are attached to recesses 360 and 362 of optical block 370. When optical oblique 370 is attached to the detector circuit board, data and reference bandwidth filters 356 and 358 are aligned with data and reference detectors 340 and 345 respectively.

All energy over the full and same range of infrared radiation beam propagated along optical path 56 and reaching detector assembly 300 at a wavelength greater than the selected cutoff is reflected to data detector 340. Similarly, the shorter wavelength energy is transmitted through beam splitter 286 to reference detector 345. Because of this, the physical relationship of detectors 340 and 345 discussed above, and the sizing and configuration of elements Interception-sensing sensors from these detectors, both detectors "come" with the same image of the electromagnetic energy beam. This contributes notably to the accuracy provided by detector assembly 300.

In other words, and optically, with the data and reference detectors 340 and 345 positioned exactly relative to one another, and the beam splitter 352 in the manner described above, these components function as if the two detectors were precisely stacked. one on top of the other. Therefore, the electromagnetic energy of the beam reaches both detectors in spatially identical mode. By making both detectors 340 and 345 spatially coincident from an optical point of view and electronically sampling detector outputs at the same time, the adverse effects on accuracy attributable to the collection of foreign material in one or the other of the optimal adapter windows 58 and 60 and window 460 of the source assembly described above, or a subsequent description 364 of the detector assembly 300 are also effectively eliminated by subsequent provisioning of the data detector and deferring output signals.

Electromagnetic energy in the beam propagated along the optical path 56 reaches the beam dissociator 352 through an aperture 366 defined in a front wall339 of the optical block 370. A sapphire-transparent transparent lens 364 extends over aperture 366 and prevents that carbon dioxide and other foreign material penetrates inside the optical block 370. Alente 364 is glued to the optical block in any convenient and appropriate manner.

Infrared radiation source assembly 400 will now be described with reference to Figures 12 and 13. Infrared radiation source assembly 400 emits infrared radiation in the form of a beam 480 (see Figures 14 and 16), which propagates along the optical path 56. The infrared radiation source assembly includes an infrared radiation emitter 445, switch / conductor frames 446 and 447 disposed in a ring assembly 420, and a lens 460 mounted on a bracket. lens 440 attached to source ring assembly 420. Infrared radiation emitter 445 includes a substrate formed of a material having low thermal conductivity. This is significant because it dramatically reduces the energy required to heat the emitter to operating temperature. When current is applied through an emissive layer 448 from the emitter 445, heating the emissive layer and the substrate, the substrate grows or increases in length because of thermal expansion, but this growth is accommodated by an elastic bonding agent instead. to be restricted. As a result, stresses, which would be imposed on the emitter if both ends were rigidly fixed, are avoided by eliminating damage to the emitter or complete failure of this component that could result if high mechanical voltages were imposed on it.

Emitter 445 of source assembly 400 is energized to heat to an operating temperature at which it emits infrared radiation in an appropriate range of bandwidth by running an electric current flow through the emissive layer 448 from an appropriate power supply. The power supply is connected to the emissive layer 448 by means of electrical conductors 451 and 452. These conductors are welded or otherwise physically and electrically connected to the opposite ends of switches 446 and 447.

Switches 446 and 447 are installed in ring 420 of source assembly 400. The environment in which the component operates can reach a high temperature by heating by the emissive layer 448 of infrared radiation emitter 445. The ring of source is therefore fa It is a polymer that remains structurally stable at the temperatures it reaches during operation of the infrared emitter 445. In the exemplary embodiment, the source ring 420 has a cylindrical configuration with an integral wall 454 and base 453. Projecting in the same direction from the base 453 are the 456, 457, 458, and 459 assembly locating bosses or brackets. The 456 and 457 spacing side by side and the 458 and 459 complementary brackets spaced side by side hug the opposing sides of 446 and 447. The bosses or brackets 461 and 462 separate the switch segments, providing gaps between them to electrically isolate the two switches. breaker segments. This is necessary so that a differential voltage can be created across the emitter 445 to cause operating current to flow through the emitter.

Referring now to Figures 14-16, as well as Figures 12 and 13, the infrared radiation produced by the emissive layer 448 of the infrared emitter 445 is focused and propagated along the optical path 56 through a lens 430 disposed in a holder. Lens material is prevented from entering the infrared radiation source assembly 400 by a sapphire or other infrared radiation transmission window 460 extending and closing the aperture into which the lens 430 is mounted. Window 460 is cemented or otherwise bonded to a protrusion 442 formed in the lens holder 440 of the infrared radiation array 400.

Energy in a specific band is absorbed by the gas of interest flowing through the throughpass adapter (typically carbon dioxide) to a proportional extent to the concentration of that gas. Next, the infrared beam attenuated through the opening 306 in the front wall 308 of the detector housing portion 210, is intercepted by the beam decoupler 352, and is reflected in the direction of the data detector 340 as transmitted to the detector. 345 reflected by mirror 354. Bandpass filters 356 and 358 in front of these detectors limit the energy reaching them to specified (and different) bands. Each of the 340 and 340 detectors produces an electrical signal proportional in magnitude to the energy intensity reaching that detector. These signals are amplified by the electronic circuitry on the detector system circuit board 310 and are fed to a digital signal processor on the flexible circuit board portion 225. The processor typically provides signals from the detectors to generate a third signal accurately reflecting gas concentration. being monitored.

Optical path 56, the distance traversed by the infrared radiation between the windows 58 and 60 mounted in the openings 52 and 54, respectively, and located within the integral U-shaped frame member 48 of the airway adapter 40, is shown. . The optical alignment features of base 250 are readily apparent from the cross-sectional view. The features of the lens holder 440 attached to the source ring assembly 420 serve to properly align the source assembly 400 to the base 250. Similarly, the features of the detector optical assembly 350 serve to properly align. detector set 300 on base 250.

Luminescence Cooling Optics236 is mounted on luminescence cooling metering circuit board 235. Luminescence cooling metering circuit board 235 includes the circuitry to drive excitation source 243 and measure the response to detectors 238 and 239 using both amplitude and phase based detection techniques. Exemplary luminescence cooling system 236 includes excitation source 243 and detectors 238 and 239 positioned on either side of excitation source 243 (see Figure 29).

Figure 15 is a plan view of the assembled components of the gas metering system prior to placement in the shop. Prior to mounting detector assembly 300 and source assembly 400 on the U-shaped base 250, these assemblies are physically and electrically interconnected to flexible circuit 230. Detector assembly 300 is connected to plate portion 226 of flexible circuit 230 with detector jumper 380 coupling (Figures 5 and 8).

The ends of the conductors 443 and 444 (Figure 12) of the source assembly 400, and the connectors on the cable 120 are connected to the flexible circuit board part 227. To mount the flat electromagnetic assembly 222 on the base 250, source assembly 400 and detector assembly are attached to base 250. The plate portion 225 of the flexible circuit 230 is placed on top of the "ü" of the base 250. The plate portion 228 is bent to fit into the detector assembly housing 254 and the plate portion 227 is bent to Fits into the 253 power supply enclosure.

Figure 16 is a radius plot of the optical path within the mounted gas metering system. Radii 480 in figure 16 are for illustration only and are shown as if the emitter layer 445 is a point source. Infrared beams from the emitter 445 are collimated by the half-sphere lens 430. The concave shape of the lens rotates to "focus" the rays in parallelism. The rays collide with the gases and infrared absorbent substances that are inside the airflow adapter and are absorbed and scattered. The remaining rays pass through the window of the air flow adapter into detector assembly 300. The rays cross through 364 and are collimated / focused on beam dissociator 352, where approximately half of the rays are reflected and traverses filter 356. and is directed to detector 340, and the other half is transmitted and reflected by mirror 354 to filter 358 and is directed to detector 345.

Figure 17 is a block diagram of the gas metering system 500 according to the principles of the present invention. A microprocessor 510 provides the signal control, measurement and processing functions of this invention. An exemplary processor is the TMS320F2812 DSP manufactured by Te-xas Instruments. Microprocessor 510 provides the source unsynchronization signals for source assembly 400, which is driven by a pulsed voltage of 5.0 V DC in an u-nipolar mode. A 511 source emitter watcher monitors source pulse width and keeps it within an allowable window. A system reset generator 520 is deployed during the wake-up sequence, so the processor will only restore once a stable voltage is reached and during shutdown sequences, an orderly shutdown sequence will occur.

The executable program, which may be stored in an EEPROM 530 or elsewhere, is communicated to microprocessor 510. The data and reference channel signals from detector assembly 300 are amplified by digital attenuation 540 prior to analog to digital conversion within 510. A detector heater 590 located within the detector assembly 300 is controlled by a feedback loop by the microprocessor 510. The low level signals from the detectors are AC coupled, amplified, and the level shifted to take into account. complete signal acquisition. Dual show-and-hold stages within the ADC provide simultaneous sampling of data and reference channels. Active gain and offset adjustment compensate for the optical and e-electronic variables in the signal chain. The detector heater driver controls the power delivery to the detectors while the detector thermistor driver provides the thermistor signals to the processor. A control algorithm such as a PID controller serves to regulate the temperature typically between 40 ° C and 50 ° C to within ± 0.02 ° C. The detector heater is powered by the +5 V DC supply, which is also used to power the analog circuit set regulator. Window heater 245 includes a temperature sensing component as well as heating component. Electronic components on the 235 circuit board, in conjunction with the microprocessor, control the delivery of power to the heating component. A control algorithm within the microprocessor 510, using the sensed temperature, maintains the temperature of the heating element at temperatures sufficiently above room temperature within the airway a-deaptor. The CODEC 555 is an ecoder decoder with integrated digital to analog converters and analog to digital converters. CODEC 555, which interfaces with microprocessor 510, modulates excitation source 243 using the output of detectors 238 and 239 in a manner to perform life-phase based measurements. Serial trigger 570 communicates bidirectionally using a indicated transmit and receive line TX and Rx respectively. Power supply 560 receives power from VSRS and VA lines with signal return and digital and analog ground provided.

The exemplary embodiment described above of the present invention has shown an optical array with an infrared detector system in a linear configuration that includes a single beam splitter, a single mirror, two filters and two detectors. This configuration is well suited for measuring a single gas flowing through the sample cell. However, there is a growing need to measure additional gases using a transducer that is the same size as the one used to measure a single gas. To this end, the present invention contemplates other embodiments for gas metering systems that include an infrared spectrometer portion capable of measuring multiple gases. For example, a four-channel system would allow quantification of concentrations of carbon dioxide, nitrous oxide and certain anesthetic agents, along with a reference channel. The present invention may also be adapted as an efficient non-dispersive infrared multi-channel gas analysis configuration using one or more of the following features and combinations:

a) multiple dichroic beam dissociators that divide the spectrum into a binary sequence, with narrow bandpass filters to select specific wavelengths;

b) combinations of two or more di-chromic dissociators on a single substrate;

c) geometric configurations in which all detectors are arranged in a single plane, and may use a single mirror rotating to multiple channels;

d) a broadband bandpass filter in place of two dichroic dissociators;

(e) toroidal focusing mirrors, and in combination with sapphire or germanium lenses; and / or

f) lenses on either side of a beam disassociating element to compactly provide independent control of reflected and transmitted light.

Figure 18 is a schematic diagram of an exemplary fashion of an optical system arranged in a linear configuration in accordance with the principles of the present invention. The optical system in this embodiment consisting of four channels, each having a narrow band and detector filter. Each of the 611, 612,613 and 614 filter / detector assemblies use similar detectors, but each filter with different passing bands. The beam from the infrared source, once it has passed through the sample cell, enters the optics. This beam is indicated by reference number 600 in the figures. The beam 600 reaches a first dichroic beam dissociator 601. The first dichroic beam dissociator 601 can be configured to pass both the shortest wavelength of interest and the longest wavelength of interest. All other wavelengths would be reflected. The other wavelengths, or channels, are separated from the reflected beam in sequence by the second and third dichroic beam dissociators 602 and 603. The sequence of beam dissociator wavelengths is somewhat arbitrary. The final element, the common mirror 604, reflects the final channel to the detector or filter / detector assembly 614. The use of this mirror allows all detectors to be in the same (i.e. coplanar) detector.

Figure 19 illustrates the characteristics of 605,606 and 607 short-pass beam decoupling filters as a function of the wavelength versus filter characteristics of the 615,616, 617, and 618 bandpass filters for each of the channels in the system. Figure 19. Each detector has a narrowband filter to select the wavelength required for detection with more specificity than can be done with dichroic beam dissociators. It should be noted that logic can be reversed in the sense that the first beam splitter can pass the longest wavelength, 618, and reflect the other wavelength for filters 615, 616, and 617.

Then the following beam dissociators may be small pass, in which case the sequence would be 617, 616 and 615, or they may be large pass, with a sequence 615, 616 and 617.

Alternatively, large and small passages may be mixed in certain sequences. It should be noted that dichroic beam splitters are used instead of the more conventional broadband beam splitters, in order to materially improve the amount of signal energy that will reach the detectors, especially the last detector. This linear system has the advantages of a simple design and all detectors being in the same plane. However, the beam spreads substantially along the path length to the final detector, so the energy collected by the last detector is less than that of the previous detectors.

Figure 20 is a schematic diagram of a systemotic having a zigzag configuration. This system makes use of the fact that a dielectric bandpass filter will reflect all wavelengths that are not transmitted. In fact, there is an energy conservation. In the case of zigzag, the first element is a mirror 621. Each of the beam splitters 626, 627, 628 and 629 is a narrow band pass filter. Because all energy that is not selected for a particular channel is reflected to other channels, the sequence of filter / detector sets 622,623, 624 and 625 is arbitrary. It should be noted that each filter must be designed to operate at the chosen angle (typically 40 ° to 45 °). The system has a shorter path length and a lower part count because narrow bandpass filters perform a dual function of channel misalignment as well as narrowly defining the desired wavelength. The detectors are now two planes, but the detector sets are identical. The system as drawn shows the light path from the source to the final detector in the same plane. For ease of conditioning, the assembly following mirror 621 can be rotated 90 degrees around the optical geometry axis, so that the source optical geometry axis would be normal to the zigzag plane.

Figure 21 is a schematic diagram of a systemotic having a quadrangular arrangement configuration. Dichroic beam dissociators are used in a more direct binary deselection process. For example, using the characteristics of the filters and beam dissociators shown in Figure 21, the first beam dissociator 631 can be set to 4 microns to divide the spectrum of interest in half. The reflected half is again divided into4,4 microns, with the reflected part going directly to the narrowband / detector 632 filter band, while the passing portion is subsequently reflected in the 636 mirror to the bandpass filter assembly. narrow / detector 633. The half passing through beam splitter 631 is reflected in mirror 638 to defect splitter 637, which is set at 3.45 microns. As in the first described path, the split beam splitter 637 directs the beam to the narrow-band filter / detector sets 634 and 635. The paths of beam channels 1 and 2, and channels 3 and 4 have been rotated around. optical geometry axis on mirror 636 and beam splitter 631 respectively. By this "twisting paths" device, all detectors can be placed close to each other in the same plane. Additionally, in this system, the two mirrors, shown as mirror 636, can be fabricated as a single piece, and beam dissociators, shown as beam dissociator 637, can also be formed on a single substrate.

It should be noted that the combination beam dissociator can be constructed as a pair of overlapping dichroic defect dissociators, with one on either side of a sapphire subtract, or it can be constructed as an extended bandpass filter where the band edges form the function of wavelength division. The following described systems may look somewhat similar in general architecture, but they contain focusing elements in sapphire-like shapes, concave spherical mirrors, or concave spherical mirrors.

The system advantage of the added focusing elements is an exceptionally improved energy collection efficiency on each detector. Without focusing elements, the beam from the source will be much larger than the detectors in the detector plane. This oversized size happens for two reasons: system expansion, and aberrations. The ratio of Source Numeric Aperture to Numeric Aperture in the detector is the magnification. Numeric Aperture is the sine of half the beam angle and the Refractive Index (equal to 1 in this mode). Depending on where the focus is set, the magnification will be in the range of 5 to 7. The source is about 0.02 "(0.51 mm) in diameter, so a detector plane image will be in the range of 0.16" (4.06 mm) to 0.2 "(5.08 mm) But detectors are typically 0.08 "(2.03 mm) in diameter (larger detectors are possible, but the cost grows rapidly with size).

In addition, while the source lens gives a very good image in the center of the field, dots on the source edge are blunted, which increases the basic image magnification. However, if positive focusing elements can be placed near the detectors, magnification can be radically reduced, and aberrations can also be reduced in absolute terms. In present systems, a compact beam can improve detection efficiency by a factor of four or more. It should be noted that in view of the beam aberration condition, it is not feasible for a single lens to form a good detector image, but in fact once the objective is to collect exactly as many IR rays as possible, a good image cannot is required.

Fig. 22 is a schematic diagram of a systemotic having a linear system configuration with lenses included in the optical assembly. This configuration is similar to the linear configuration of Figure 18, with the addition of a lens 645 inserted along the optical path, typically between beam splitters 642 and 643 and filter / detector assemblies 652 and 653. Lens function It compresses beam energy to detector set 653 and detector set 654, which will improve the detection efficiency of these channels. The action of the lens is to reduce the magnification of the system. In addition, the 655-658 lenses can be added to each channel, thereby further reducing the magnification and improving and equalizing the efficiency of all detectors.

Figure 23 is a schematic diagram of a systemic having a zigzag configuration with new lenses included in the optical assembly. In this configuration, which is essentially a modification of that shown in Figure 20, the lenses are added to each channel to compress the beam size. If a single lens is added between the beam splitter and the detector, only the transmitted beam will be affected, and the reflected beam will expand more than desired through the last channel. But if a single lens added in front of the beam decoupler that is strong enough to compress the beam properly for that detector, the effect on the reflected beam will be doubled and also strong.

The present invention solves this dilemma by dividing the lens into two components, one part in one or the other of a narrow bandpass filter. For example, split lens / filter assembly 669 comprises lenses 666 and 668 and filter 667. By dividing the lens in this mode into each channel, each of the portion that is transmitted and the portion that is reflected gains the effect of a lens. entire. Alternatively, the two lenses in each channel may be different, so that, for example, the transmitted beam may be more strongly compressed when compared to the reflected beam. It should be noted that with this system the beam-decoupling dissociators are eliminated. .

Fig. 24 is a schematic diagram of a systemic having a dog paw configuration. This configuration is similar to the quadrangular arrangement in which dichroic beam dissociators are used to divide the beam by wavelengths in a binary manner. Dichroic beam dissociator 682 makes the first division. The reflected beam goes to the reflector 681. This is one of four focusing mirrors that are added to compress the beam to improve detection efficiency. These mirrors may be spherical, but preferably they are aspherical.

This preference arises because a spherical element at a high angle of incidence will produce two different focal points, one in the plane of incidence, the other perpendicular to it. In other words, a mirror like this will produce an astigmatic image. By executing a radius of curvature different in the two geometric axes, astigmatism can be corrected. Anospheric is a general term for a non-spherical surface. The mirrors shown here are toroidal, a subset of the general class. In the present case, even if a good image is not required, an aspherical mirror can produce a more uniform circular beam pattern.

The reflected and refocused beam is again divided into the dichroic beam dissociator 675. Again the reflected beam is refocused to the bandpass / detector 672 assembly. The transmitted beam goes to the filter / detector assembly. 671. The beam transmitted by the beam dissociator 682 is refocused by the focusing mirror 683, and divided by the defect dissociator 678. As with the other two channels, the beam goes to the filter / detector assembly 674, or to the filter / detector assembly. 673 by means of the focusing mirror 677. It should be noted that this system provides high collection efficiency and a unique flat compact detector arrangement.

Figure 25 is a schematic diagram of a systemic having a serpentine configuration. The "serpentine" architecture is similar to the linear arrangement except that the focusing mirrors 691-694 are added to each channel. The initial division is done by the dichroic beam dissociator 681, followed by the beam dissociators 682 and 683, and the mirror 684. Focusing mirrors may be spherical, but aspherical mirrors promote a significant improvement in the efficiency of collect. In an exemplary embodiment of the present invention, the mirrors are made in a single large molding. The filter / detector assemblies 685, 686,687 and 688 consist of a narrowband and detector filter, the same as in the other embodiments described above.

Figure 26 is a schematic diagram of a systemic having a tunnel configuration. Infrared energy can be distributed to a planar array of detectors in a different mode. Energy from the source 698 may be directed into a tube 696 by the holder 699, or what may be termed an optical tunnel. If an interior 695 of the tube is a mirror, and if the tubofor is long enough (on the order of ten times the diameter), the energy at the end of the tube will be well mixed, formageometric. That is, any structure in the incoming beam, for example because of an airway imperfection, or a drop of liquid in an airway window, will not be detectable at the exit (although the total energy level may be low). . Similarly, if the input beam is not exactly at the right place, or at the right angle, there is essentially no effect on the output.

The idea of this embodiment is to place a planar arrangement 697 of narrow bandpass filters and associated detectors at the output. The tunnel action will distribute the energy symmetrically to the detectors. It should be noted that the energy output is radially symmetrical but not uniform over the area. The system as described is not efficient because the pipe outlet is circular, although the arrangement is square (for four detectors), and additionally the area of each detector is a fraction of the total outlet area.

This loss in efficiency may be alleviated by running the square tube to match the detector arrangement, or alternatively, a set of funnels may be placed in the outlet. These funnels, as a group, would accept all the energy from the pipe, split it in multiple ways to match the number of channels, and concentrate the energy below the detector size. In the figure, the side of the tube (and the source mirror) has been cut for illustration. The detector plane does not show the arrangement. Figure 27 is a side view of a four channel optical system 700 arrangement arranged in a linear configuration on a substrate 705. Infrared radiation enters the detector / optical assembly 700 upon first passing through the lens. 710. Infrared radiation is then divided and reflected successively by defect dissociators 743, 753, and 763. Infrared radiation transmitted through filters 740, 750, and 760 before detectors 745, 755, and 765, respectively. The remaining infrared radiation passing through the beam splitter 763 is reflected by the focusing mirror 720 through the filter 770 and to the detector 775. Heaters 735 and 730 serve to keep the detector block 780 at a constant temperature.

In the embodiments described above, multiple absorption type detector assemblies are provided for detecting more than one gas constituent in the gas flowing in the sample cell. It should be understood that the present invention also considers providing multiple gases for the luminescence cooling type of the gas detectors, either alone or in combination with the type of detector absorption. The type of multiple luminescence cooling of the gas detectors would require multiple sources, detectors, filters and multiple chemicals in the airway adapter substrate.

Figure 28 is an exploded view in perspective optical assembly of gas metering system 240 and luminescence cooling metering circuit board 235 with holder 232. Detector filter 233 is shown in Figure 29 removed from luminescence optical cooling system 236, which is mounted on the luminescence cooling metering circuit board 235. Luminescence cooling metering board 235 includes the circuitry to drive excitation source 243 and measure the response with detectors 238 and 239 using known detection techniques.

29 is an exploded view in perspective luminescence cooling metering circuit board. The exemplary luminescence optics 236 includes excitation source 243, detectors 238 and 239 positioned on either side of excitation source 243, detector filter 233, optional excitation source filter 241, and shield 234. All are arranged in the same plane allowing size and weight to be reduced. An exemplary excitation source consists of a green light emitting diode. The excitation source 243 and detectors 238 and 239 are separated from each other by electrical protection and optical filters. An exemplary detector consists of a photodiode. It is to be understood that the present invention envisages providing a photodetector ring surrounding or partially surrounding source 243. This ring may be a single detector or a plurality of detectors and may have any suitable pattern, such as circular, quadrangular, triple-spaced. home, rectangular, etc.

Detector filter 233 in the exemplary embodiment is a rectangular filter structure with an aperture 229 through which radiation from the excitation source is emitted. The optical properties of the detector filter are such that the wavelengths of radiation related to the cooling of the detection / chemical film in response to contact with the measured gas or gases are substantially transmitted through the filter and Radiation unrelated to this interaction is not substantially transmitted through the filter. Detector filters can be bandpass, highpass, lowpass, or any other type of filter known in the art. In addition, an optional excitation source filter241 may be used to limit radiation emission for radiation wavelengths for which the detection film is excited, thus preventing undesirable wavelengths from reaching the detection film.

The detection film which is sensitive to a gas of interest is preferably arranged in a plane that is parallel to said foreground of the exemplary luminescence optics 236, and displaced therefrom. To minimize undesirable interaction between the excitation source and the detectors, shield 234 is placed around the excitation source. The inner surface of shield 234 in exemplary mode is substantially reflective of the radiation mitigated by the excitation source, thus serving two purposes. This allows it to redirect strange light back toward the detection film, improving system efficiency. Additionally, excitation sources, such as LEDs, emit light at a greater angle than that understood by the detection film. The shape of the shield is preferably designed to block light so that it does not reach the detectors directly and influence luminescence measurement.

In the exemplary embodiment shown, the radiation emitted by the excitation source 243 is transmitted through the filter 241 and through the convex window 247 and is incident on the detection film. Based on the oxygen concentration, the detection plate emits radiation at a different wave length that is transmitted back through the window 247 and filtered by the detector filter 233 and measured by the two detectors disposed within the detector filter 233.

Additionally, an index matching layer (not shown) may optionally be positioned between the detectors and the detector filter to minimize reflective loss. Radiation from the detection film is emitted in all directions and only a small fraction of the emitted radiation is directed to the detectors. Because of Fresnel reflections, this radiation is further enhanced at each interface along the optical path. Thus, filling the air gaps with a material, such as an index matching material, allows this reflective loss to be minimized.

The flexible heater circuit 245 is electrically interconnected with the luminescence cooling measurement circuit board 235 as noted earlier. Temperature control or compensation is required because the amount of luminescence emitted by the detection film is influenced by temperature. . To maintain a constant temperature in the film, the window heater 245 communicates thermally with the flat side of the window 247 which is conventionally sapphire. This heater keeps the window 247 at a constant temperature which in turn maintains the temperature of the detection film. The window heater245 is designed in a ring shape to stay out of the optical path. Window 247 is convex rather than flat to improve thermal contact with the detection film. The precise contact between these two components and the curved profile also has the effect of improving the amount of light transmitted through the detection film and back of the detectors. As noted above, an exemplary embodiment of a luminescence optical cooling system 236 suitable for use in the present invention is disclosed in application 451.

It should be understood that the luminescence cooling feature of the present invention and the absorption feature of the present invention may be used alone or in combination and also in a side current configuration.

Several alternative structures for the invention are currently considered. For example, the present invention contemplates using a prismatic lens or aspherical lens in front of the excitation source to distribute light more evenly over the detection film. It is also considered to change the position of the excitation source and detectors, that is, to use a single large detector that is surrounded by two or more excitation sources. The present invention has further considered or angled the detectors so that the detector face is substantially perpendicular to the radiation emitted by the luminescent material to improve detection efficiency.

The present invention also contemplates providing the display 800 (see Figure 3) in the gas metering system housing. The display can be any suitable display, such as an LED, OLEDs, LCD, etc. Providing a display in the gas metering housing allows the clinician or other user to view warnings or advisory messages, waveforms, trends, and other pertinent information directly from the patient's next unit, without repositioning the units themselves. to see a conventional monitoring screen, which is typically necessary because in a conventional system the monitoring screen is often several feet (meters) away from the patient. This would be of particular importance during an adverse clinical event that would require immediate attention and response from the clinician.

Although the invention has been described in detail for the purpose of illustration based on what is now considered to be the most practical and preferred embodiments, it should be understood that such detailing is solely for that purpose and that the invention is not limited. to the disclosed embodiments, but rather is intended to encompass equivalent modifications and arrangements within the scope and scope of the appended claims. For example, it should be understood that the present invention considers that, to the possible extent, one or more features of any modality may be combined with one or more features of any other embodiment.

Claims (10)

1. Gas metering system (100), characterized in that it comprises: (a) a housing (250) adapted to be fitted with an airway adapter, (b) a luminescent cooling gas metering assembly (236) disposed in housing, comprising: (1) a source (243) arranged in the foreground, and (2) at least one detector (238, 239) also arranged in the foreground, (c) a filter (233) over the detector , where the filter passes through radiation wavelengths related to luminescence cooling and substantially blocks other wavelengths; and (d) an optical shield (234) disposed around at least a portion of the source. System according to claim 1, characterized in that the at least one detector is arranged near the source. System according to claim 1, characterized in that the at least one detector includes a plurality of detectors. System according to claim 1, characterized in that the at least one detector includes a first detector disposed on a first side of the source, and a second detector disposed on a second side of the source. System according to claim 1, characterized in that the housing is generally U-shaped. A system according to claim 1, further comprising a processor (510) disposed in the housing, wherein the processor is programmed to measure a gas constituent of a gas flow in the airflow-based adapter. at a detector output. A system according to claim 1, further characterized by comprising an infrared absorption measuring assembly (240) arranged in the housing. A system according to claim 7, characterized in that the housing has a generally U-shaped configuration having a first leg and a second leg, wherein the infrared absorption gas metering set comprises a set. of the first leg and a detector assembly disposed on the second leg, and wherein the luminescent cooling gas metering assembly is disposed in the housing between the first leg and the second leg. A system according to claim 7, characterized in that the luminescence cooling gas metering assembly includes a detection film in communication with the gas flow in the conduit. System according to claim 9, characterized in that the sensing film is disposed on the air passage adapter.