CN101589302B - Gas measurement system - Google Patents

Abstract

A gas measurement system (100) of this invention includes a housing (250) adapted to be mounted on an airway adapter, and a luminescence quenching gas measurement assembly (236) disposed in the housing. The luminescence quenching gas measurement assembly includes a source (243) disposed in a first plane, and at least one detector (238, 239) also disposed in the first plane. A filter (233) is provided over the at least one detector to passes wavelengths of radiation related to luminescence quenching and substantially blocks others. An optical shield (234) is disposed around at least a portion of the source.

Description

Gas Measurement System

priority claim

This application claims priority to US application 11/368,832, filed March 6, 2006, under 35 U.S.C. § 120/365.

technical field

The present invention relates to a mainstream respiratory gas measurement system with integrated signal processing and improved optical design, and a method of combining the same.

Background technique

The respiratory gas measurement system has gas detection, measurement, processing, communication and display functions. It is considered to be either turning or sidestream or non-turning or mainstream. A diverted gas measurement system transports a portion of the sampled gas from a sampling point, usually a breathing circuit or patient flow path, through a sampling tube to a gas sensor that measures the gas composition. Non-diverted or mainstream gas measurement systems do not allow gas to escape from the breathing circuit or airway, but measure the composition of the gas flowing through the breathing circuit using a gas sensor placed on the breathing circuit.

Conventional mainstream gas measurement systems include the gas detection, measurement and signal processing elements required to convert a detection or measurement signal, such as a voltage, to a value, such as transmittance, that can be used by the system to determine the detected gas composition. In conventional mainstream gas measurement systems, the gas sensor is connected to a sample cell placed in the breathing circuit. A gas sensor located on an airway adapter disposed in a breathing circuit includes only the elements necessary to output a signal corresponding to a characteristic of the gas to be detected. Placing the sample cell directly on the breathing circuit results in a "clear" waveform that reflects in real time the bias of the measured gas such as carbon dioxide or oxygen in the airway. The sample cell, also known as a cuvette or airway adapter, is located in the flow of breathing gas, eliminating the gas sampling and purge required in sidestream gas measurement systems.

For conventional gas measurement systems capable of measuring carbon dioxide, the gas sensor includes a source that emits infrared radiation that includes the absorption band of carbon dioxide. Infrared rays are emitted in a direction perpendicular to the breathing airflow path. Carbon dioxide in the sample gas absorbs radiation at some wavelengths and passes others. Conventional gas sensors include photodetectors that measure emitted radiation.

For a gas measurement system capable of measuring oxygen using a luminescence quenching measurement technique, the gas sensor may include an excitation source that excites a photosensitive chemical disposed on or within a substrate and emits visible light rays, and measures the change in temperature when the chemical is exposed to oxygen. A detector that emits radiation. Gas concentrations can be determined from the time response of luminescence using known relationships such as the Stern-Volmer relationship.

Conventional mainstream host systems include electronics that control the transmitter in the gas sensor and provide gas measurement functionality based on the detector's output signal. Mainstream gas measurement systems known in the art transmit analog signals along a cable between the host system and the gas sensor, typically 6 to 8 feet in length, and are also susceptible to electromagnetic interference (EMI). This is particularly important in line with the trend toward increased electromagnetic immunity levels required and in international medical device standards. Examples of such conventional mainstream gas measurement systems are shown in US Patent Nos. 4,914,720 issued to Knodle et al. and 5,793,044 issued to Mace et al.

The measurement and signaling electronics are located in the host system, and existing mainstream gas measurement systems are complex and expensive to interface to the host system. The host system typically includes circuitry to perform functions such as: (1) generating a time signal; (2) supplying pulsating energy to a solid-state infrared emitter; (3) measuring and precisely controlling the temperature of an infrared detector; (4) measuring and controlling an airway adapter heater; (5) signal conditioning including filtering and programmable gain settings; and (6) a monitor circuit to prevent accidental destruction of the infrared emitter.

In addition, for clinical use, mainstream system measurement systems must be designed robust so that they are not affected by common mechanical misuse and environmental changes in temperature and humidity. The instrument, or at least the gas measurement system portion of the instrument, must be small and lightweight so as not to impede the movement of the patient or other medical equipment or treatment. To achieve the goal of being small and light, the optical part of the gas measuring system must also be designed such that it occupies as little space and weighs as little as possible.

Given these known complexities of conventional gas measurement systems, it would be desirable to provide mainstream gas measurement systems that are small, lightweight, and more easily interfaced to host systems. It is also desirable that the system provide an improved method of assembly over known gas measurement systems.

Contents of the invention

It is therefore an object of the present invention to provide an optical platform that overcomes the disadvantages of known optical platforms for luminescence quenching based gas measurement systems. This object is achieved according to the present invention by providing a gas measurement system assembly comprising a cover adapted to be arranged on an airway adapter and a luminescence quenching gas measurement assembly arranged within the cover. The luminescence quenching gas measurement assembly includes a light source disposed in a first plane, and at least one detector also disposed in the first plane. A filter is provided on the at least one detector to pass wavelengths of radiation related to luminescence quenching and to substantially block other wavelengths. A light shield is disposed around at least a portion of the light source. This structure provides a relatively compact structure of the luminescence quenching gas measurement assembly.

These and other objects, nature and characteristics, as well as methods of operation and functions and combinations of parts of the associated structural elements and costs of manufacture of the present invention will become more apparent from a consideration of the following description and appended claims with reference to the accompanying drawings, all of which form this specification , wherein like reference numerals designate corresponding parts in the various drawings. However, it is to be clearly understood that the drawings are for illustration and illustration only, and not for defining the limitations of the invention.

Description of drawings

1 is a perspective view of a gas measurement system coupled to a host system and configured to be removably secured to an airway adapter assembled with patient breathing circuit components in accordance with the principles of the present invention;

2 is a perspective view of a gas measurement system configured to connect to a host system;

3 is a perspective view of a gas measurement system configured to be removably secured to an airway adapter;

Fig. 4 is an exploded view of the gas measurement system with the cover and gas measurement system electro-optical assembly shown;

Fig. 5 is an exploded view of the electro-optical assembly of the gas measurement system;

6 is an exploded view of the gas measurement system with the cover, electronic circuit board, and gas measurement system optical components shown;

Figure 7 is an exploded view of the gas measurement system optical assembly with the structural base unit, detector assembly and source assembly shown;

Figure 8 is an exploded view of the detector assembly;

9 and 10 are exploded views of the reticle assembly portion of the detector assembly;

FIG. 11 is a cross-sectional view of a combined photomask assembly;

Figure 12 is an exploded view of the source assembly;

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

Figure 14 is a cross-sectional perspective view of the combined gas measurement system taken along line 14-14 of Figure 4;

Figure 15 is a flattened view of the gas measurement system assembly prior to placement in an enclosure;

Figure 16 is a ray tracing of the optical path within a gas measurement system in accordance with the principles of the present invention;

Fig. 17 is a structural diagram of a gas measuring system according to the principles of the present invention;

Figure 18 is a schematic diagram of a four-channel optical system in a simple linear configuration of a detector assembly optical assembly in accordance with the principles of the present invention;

Figure 19 is a graph showing one embodiment of the wavelength of the beam splitter versus the wavelength of the filter;

Fig. 20 is the schematic diagram of four-channel optical system in the zigzag structure;

21 is a schematic diagram of a four-channel optical system in a square array structure;

22 is a schematic diagram of a four-channel optical system in a linear system with a lens structure;

Fig. 23 is the schematic diagram of four-channel optical system in the zigzag structure with lens structure;

24 is a schematic diagram of a four-channel optical system in a dogleg configuration;

25 is a schematic diagram of a four-channel optical system in a serpentine structure;

26 is a schematic diagram of a four-channel optical system in a channel structure;

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

28 is an exploded view of a portion of a gas measurement system optical assembly in accordance with the principles of the present invention; and

FIG. 29 is an exploded view of the luminescence quenching measurement circuit board in the gas measurement system of FIG. 28 .

Detailed ways

The gas measurement system 100 in accordance with the principles of the present invention includes all signal and data processing required to produce continuous values of the partial pressure or concentration of gas flowing through the airway adapter that communicates with the patient's airway. fluid communication. The gas measurement system is located on a "measurement head" mounted to the airway adapter. The gas measurement system includes the electronic circuitry required to measure and calculate continuous values of infrared absorbing gases such as carbon dioxide and luminescent quenching gases such as oxygen, and to interface the gas measurement system to a host system. In the exemplary embodiment, gas measurement system 100 acquires and processes analog signals, then transmits digitized patient parameters and waveforms through interface cable 120 as a serial data stream.

The gas measurement system of the present invention does not require additional electronic boards in the host system that are required to process the detector output signals, thereby saving space within the host system and reducing cost to the end user. Through design efficiency and through miniaturization, the resulting gas measurement system is nearly as small and lightweight as existing mainstream gas measurement sensors. Addition of signal processing without significant increase in size or weight is particularly important in applications where the gas measurement system has an airway adapter in close proximity to the patient's face at the distal end of the endotracheal tube or nasal cannula to monitor patient breathing.

An exemplary embodiment of an airway adapter 40 and gas measurement system 100 constructed in accordance with and employing the principles of the present invention is shown in FIGS. 1-3. Conventional gas measurement systems do not place signal processing and control electronics in the gas measurement system, but instead place any of these features in the host system. The present invention utilizes highly integrated digital signal processing (DSP) technology to perform many complex electronic interface functions in a small single-chip processor including program and data storage and analog-to-digital conversion.

Much of the efficiencies gained in integrated respiratory gas measurement systems is the result of relocating electronics within the gas measurement system. For example, this relocation affects design aspects of the interface cable 120, such as conductor count, shielding requirements, and thus cable thickness, weight, and cost. The cable requires fewer conductors and is therefore smaller, lighter and more flexible, while placing less load and strain on the sensor. The exemplary embodiment uses 7 wires and one shield, while the conventional device uses 16 wires and two shields.

The present invention has several additional advantages over conventional gas measurement systems, including free/simplified connection to the host system 70, and increased immunity to radio frequency interference. With a simplified hardware and software interface, the host system 70 requires only a simple, small connector to the serial port, and a few supply voltages. In clinical applications, there is often concern about adding weight to the patient circuit near the endotracheal tube (ET tube, endotracheal tube), especially in children and neonates. The present invention provides a significant improvement in this regard, as the weight and potential drag of the cables can be reduced. Existing cables to the host system were larger in diameter, heavier and less flexible.

Conventional gas measurement systems with components located on or near a patient's airway often struggle to meet the existing immunity standard of 3 volts/meter. An update to the International Standard for Electromagnetic Compatibility of Medical Devices increases this test level to 20 V/m. Meeting these standards with existing designs would be difficult and expensive due to susceptibility to interference from analog signals transmitted over the cable. In the present invention, it is not necessary to transmit analog signals via cables to the host system, and all components and signals susceptible to radio frequency interference (RFI) are located near the measurement elements in the gas measurement system.

Not requiring all the complex external interface electronics greatly reduces system cost. Efficient use of interconnection technologies such as rigid-flex circuit boards and other manufacturing efficiencies keeps the total system cost lower than that of existing stand-alone mainstream gas measurement systems.

Integrating the measurement and signal processing electronics of the gas measurement system increases the waste heat generated in the gas measurement system 100 . The compact nature of the design requires careful consideration of thermal design. For example, the gas measurement system 100 is configured to allow waste heat generated by the transmitter and electronics of the gas measurement system to heat the windows of the airway adapter to reduce fogging. This feature of the invention allows for the elimination of the ceramic heaters (also called box heaters) used in conventional gas measurement systems. Additionally, removal of the ceramic heater along with other benefits of the design reduces the overall power consumption of the present invention from approximately 5 watts (W) to 1.25W.

FIG. 1 is a perspective view of a gas measurement system 100 coupled to host system 70 and configured to be removably secured to airway adapter 40 , which is combined with patient breathing circuit 20 components. The airway adapter 40 is typically assembled within the breathing circuit 20 between the elbow 25, which is the connection to the patient interface, such as a mask or an endotracheal tube, and the "Y" tube 30 to which the "Y" tube 30 is connected. To positive pressure generators such as ventilators. The host system 70 supplies power to the gas measurement system 100, receives the gas concentration signal and the measurement value output from the gas measurement system, and displays the measurement value under the condition that the gas concentration signal is a carbon dioxide concentration signal such as: (a) carbon dioxide in the patient's exhalation Concentration, (b) inhaled carbon dioxide, (c) respiratory rate, and (d) end-tidal carbon dioxide. Similarly, where the gas concentration signal is an oxygen concentration signal, the host system 70 displays measurements such as (a) oxygen concentration in the patient's exhaled breath, (b) inspired oxygen, (c) respiratory rate, and (d) tidal end of oxygen.

As mentioned above, the cable 120 connects the gas measurement system assembly 100 and the host system 70 together. The distal end 110 of the cable 120 is securely and detachably connected to the host system. The proximal end 123 of the cable 120 includes a strain relief element 130 that allows tension to be applied to the cable 120 without affecting the conductors therein. Power is supplied to the gas measurement system from the host system via this cable. However, the present invention also contemplates that the gas measurement system could be powered by an integrated or separate battery pack and wirelessly transmit its data to the host system, thereby eliminating the need for cable 120 . Consider wireless communication using protocols known from the prior art such as Bluetooth, Zigbee, Ultra Wideband (UWB) employed in Body Area Networks (BAN) and Personal Area Networks (PAN). The gas measurement system can also be cabled to a network hub that integrates the gas measurement system's signal with other gas physiological measurements.

The ends of the airway adapter 40 (Figs. 1 and 3) are designed to connect to the patient interface and the respiratory system. For example, an airway adapter may be placed between an endotracheal tube (not shown) inserted into the patient's trachea and the breathing circuit of the positive pressure generator or ventilator 75 . In the exemplary embodiment, gas measurement system 100 is used to measure carbon dioxide and oxygen levels of a patient. The particular airway adapter 40 depicted in Figures 1 and 3 is not itself part of the invention. Also, the present invention contemplates that the gas measurement system of the present invention may be used with any conventional airway adapter, including absorption or luminescence quenching adapters. Adapters suitable for measuring gases via infrared absorption and luminescence quenching are disclosed in U.S. Patent Application No. 09/841,451 and U.S. Publication No. 2002/0029003 ("the '451 Application'") to Mace et al. Portfolio reference here. Airway adapter 40 is typically molded from polycarbonate or an equivalent polymer.

In the exemplary embodiment of the invention shown in FIGS. 3 and 14 , an airway adapter 40 has a generally parallelepipedal central portion 42 and two cylindrical end portions 44 and 46 with a sampling channel 47 passing through the adapter from end to end. End portions 44 and 46 are axially aligned with central portion 42 . Central section 42 provides a seat for gas measurement system 100 . The overall U-shaped box member 48 positively positions the gas measurement system 100 forward on the adapter, and in the transverse direction indicated by arrow 50 in FIGS. 1 and 3 . Arrow 50 also shows the direction in which to move airway adapter 40 to bring it and gas measurement system 100 together. Holes 52 , 53 and 54 are formed in central portion 42 of airway adapter 40 .

Gas measurement system 100 is assembled to the airway adapter by aligning holes 52 and 54 along optical path 56 as shown in FIG. 14 , for example. Optical path 56 extends laterally from light source assembly or emitter 400 in gas measurement system 100 through airway adapter 40 and the one or more gases flowing through the airway adapter. The optical path continues from the airway adapter to the detector assembly 300 in the gas measurement system 100 . To prevent gas flowing through the airway adapter 40 from escaping through holes 52 and 54 and unacceptably attenuate the infrared rays intersecting optical path 56, and to prevent foreign material from entering the airway adapter, infrared radiation is typically passed through windows 58 and 60 to seal the hole. In addition, the hole 53 is covered by the window 49 . In physical contact with window 49 and located inside airway adapter 40 is a sensitive membrane with a photosensitive chemical. The chemical emits radiation in response to 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 apertures 52, 53, and 54, and one or more gas measurement techniques employing the apertures.

FIG. 4 is an exploded view of gas measurement system 100 including polymer cover 210 and gas measurement system electro-optic assembly 220 . Gas measurement system electro-optical assembly 220, perhaps best shown in FIGS. 4 and 7, includes the following elements: (a) infrared radiation source assembly 400 (shown in greater detail in FIGS. 12-13 ), (b) infrared radiation detection device assembly 300 (shown in more detail in FIGS. 8-11 ), and (c) optional luminescence quenching measurement circuit board 235. In a combined gas measurement system, the strain relief element 130 is held in place by the walls 214 and 252 provided on the base 250 and cover 210 . Wall 214 and wall 252 mate when the cover is attached to the base, using any conventional technique such as a snap fit or friction lock arrangement to achieve this.

The gas measurement system electro-optical assembly 220 shown in FIGS. Together. The light source and detector assemblies in the optics assembly are connected to a "U" shaped base 250 and are mechanically and electrically connected to a flexible circuit board that is folded around these components and attached to the base 250 . This assembly allows the active components of the gas measurement system to be tested to be used as a unit rather than stand-alone prior to assembly. Therefore, it is not necessary to wait until a gas measurement system is fully assembled to determine whether it meets performance specifications. The result is a significant cost reduction, an objective facilitated by reduced wiring and a significant reduction in assembly expense.

5 is an exploded view of gas measurement system electro-optic assembly 220 with flex circuit 230 , bracket 232 , luminescence quenching measurement circuit board 235 separated from gas measurement system optical assembly 240 . Flexible circuit 230 includes rigid board portions 225, 226, 227, and 228 (see FIG. 15). The rigid sections are interconnected by flexible sections. The flexible circuit board includes the analog and digital circuitry required to drive the infrared source and convert the signal from the detector assembly to an output value for an infrared absorbing gas such as carbon dioxide, and/or convert the signal from the luminescence quenching assembly to an output value for a gas such as oxygen . Circuit board 235 includes circuitry and optics for oxygen detection by luminescence quenching techniques. Optical assembly 240 includes detector assembly 300, light source assembly 400, and heater flex circuit 245 for controlling the oxygen film temperature. The heater flex circuit 245 is combined with the gas measurement optics assembly 240 on top of the "U" shaped base 250 . The pins 246 at the distal end of the heater flex circuit 245 are inserted into corresponding holes 237 in the end of the luminescence quenching measurement circuit board 235 prior to soldering. Similarly, the pins 381 of the detector flex jumper 380 are inserted into corresponding holes 231 along the edge of the board portion 226 of the flex circuit 230.

FIG. 6 is an exploded view of the gas measurement system 100 showing the cover, electronic circuit board, and gas measurement system optical components. Gas measurement system electro-optical assembly 220 having flex circuit 230 , bracket 232 and circuit board 235 is shown separated from gas measurement system optical assembly 240 .

FIG. 7 is an exploded view of the gas measurement system optical assembly 240 showing the structural base element 250 , detector assembly 300 and source assembly 400 . Base member 250 of gas measurement system 100 supports source assembly 400 in source assembly chamber 253 and supports detector assembly 300 in detector assembly chamber 254 . A generally rectangular gap 66 is provided between the chambers 253 and 254 brackets. Gap 66 is configured to engage central portion 42 of airway adapter 40 . Two pairs of complementary cavities in first end 258 and second end 257, largely defined by the side walls and edges of base member 250, cooperate to define infrared radiation source chamber 253 and infrared radiation detector chamber 254, respectively. Gas measurement system base element 250 may be molded from polycarbonate or any other suitable polymer. In the depicted exemplary embodiment, base member 250 has flat side walls and integrated edges perpendicular to the side walls.

A source aperture 256 is defined in the housing wall to provide an optical path for radiation generated by the source assembly 400 to enter the sample cell portion of the airway adapter. A source aperture 255 is defined in the housing wall to provide an optical path for radiation passing through the existing airway adapter to reach the detector assembly 300 . In the depicted embodiment, luminescence quenching apertures 260 corresponding to apertures 53 are also provided in the enclosure to measure material luminescence quenched by oxygen in the sample gas. It will be appreciated that the luminescence quenching and absorbing features of the present invention may be used alone or in combination. Thus, holes 255, 256 and 260 may be eliminated depending on the use of one or both of these gas measurement techniques.

FIG. 8 is an exploded view of the detector assembly 300 of the gas measurement system 100 , and FIG. 9 is an exploded view of the detector optics assembly 350 . The detector assembly 300 includes detectors 340 and 345 disposed on a heat sink 330 , a heat sink spacer 320 and a detector assembly circuit board 310 . The heat sink 330 is connected to the heat sink spacer 320 which is connected to the detector assembly circuit board 310 . The resulting support assembly 325 is assembled to the detector optics assembly 350 by aligning the holes 335 , 336 , and 337 in the light block 370 with the corresponding alignment pins in the heat sink 330 . Detector optics assembly 350 includes optical elements such as lens 364 , filters 356 and 358 , mirror 354 and beam splitter 352 and is combined with detector support assembly 325 .

Disposed in the recesses of the heat sink 330 are data and reference detectors 340 and 345 aligned in the same plane (ie, coplanar), allowing more efficient temperature regulation of the detectors. Due to the sensitivity of lead selenide to infrared radiation including wavelengths of interest, the detector is preferably fabricated with a lead selenide detector element. Additionally, the lead selenide data and reference electrodes 340 and 345 are very sensitive to temperature. It is therefore important to maintain the two detectors at the same temperature preferably within a tolerance of 0.02°C. Detectors 340 and 345 are maintained at a selected operating temperature by a detector heating system comprising detector heating elements 391 and 392, temperature control thermistors (not shown), and detector assembly circuit boards 310 and Operation/control circuitry (not shown) in flexible circuit 230 .

Detectors 340 and 345 are connected to a detector assembly circuit board 310 to which a voltage bias is applied across portions of the detector infrared radiation detecting elements of the same configuration and size. The gap between the detector and the boundary of the detector-accommodating recess in the thermostatic support serves to electrically isolate the detector from the conductive, thermostatic support. A thermal resistor (not shown) is positioned so that its center is located in the slot 322 of the fin spacer 320 . The heating elements 391 and 392 are located at the ends of the diffusion sheet 330 and are in close contact with the cooling sheet. Heating elements 391 and 392 comprise flexible circuit portions with distal surface disposed resistors for transferring heat.

Two pins 388 and 389 are provided in the heating element to connect it to the detector assembly circuit board 310 . The flex circuit portions of heating elements 391 and 392 are in intimate contact with heat sink 330 . In the exemplary embodiment, an epoxy, preferably having a high thermal conductivity, is used to bond the flex circuit portion of each heating element to heat sink 330 . Pins 388 and 389 of heating elements 391 and 392 are inserted into corresponding holes 386 and 387 on detector assembly circuit board 310 . A detector flex jumper 380 interfaces the detector assembly circuit board 310 to the board portion 226 of the flex circuit 230 . The pins 382 of the detector flex jumper 380 are inserted into corresponding holes 383 along the edge of the detector assembly circuit board 310 . The pins 381 of the detector flex jumper 380 are inserted into the holes 231 in the board portion of the flex circuit 230 .

The detector optics assembly 350 will be described with reference to FIGS. 9-11. Detector optics assembly 350 includes beam splitter 352 , mirror 354 , filters 356 and 358 , and detector lens 364 . The beam splitter is generally a parallelepiped structure. The element is fabricated from a material such as silicon or sapphire that is substantially transparent to electromagnetic energy at the wavelength of interest. The exposed front surface of the beam splitter is completely covered with a coating capable of reflecting electromagnetic energy impinging on the beam splitter with a wavelength longer than a selected value. In the described embodiment of the invention, the coating will reflect energy at wavelengths greater than about 4 microns to data filter 356 and data detector 340 . Instead, shorter wavelength energy is emitted through beamsplitter 352 to mirror 354 and reference filter 358 and reference detector 272 .

Beam splitter 352 is held in place by epoxying or otherwise gluing beam splitter 352 to shelf-like protrusion 351 integral with light block 370 . Precise positioning of the beam splitter 352 within the light block 370 has the advantage of eliminating the need for subsequent adjustment of the beam splitter orientation. Similarly, mirror 354 is held in place by epoxying or otherwise gluing the mirror to shelf-like protrusion 353 , which is integral with light block 370 . Furthermore, the electro-optical assembly of the present invention has an optimal focal length which allows the use of smaller, less expensive detector assemblies for gas detection systems.

Bandpass filters 356 and 358 limit the infrared radiant energy that reflects from beamsplitter 352 and emits from beamsplitter 352, respectively, and strikes data and reference detectors 340 and 345 into selected bandwidths. In the exemplary embodiments and applications of the invention discussed and depicted in the figures, the reference detector filter 358 is nominally centered on a wavelength of 3.7 microns. Such a filter emits the maximum energy near the carbon dioxide band absorbed by the data detector 340 . The maximum energy absorption in the adjacent bandwidth is chosen so that the output of the reference detector 345 will be at least as large as the output of the data detector 340 . This has the distinct advantage of increasing the accuracy of the gas concentration representative signal obtained by subsequently determining the ratio of the data and reference signals.

Data detector bandpass filter 356 is nominally centered on a wavelength of 4.26 microns. The carbon dioxide absorption curve is very narrow and strong, and the bandpass filter 356 is centered on the emission band within this absorption curve. Thus, if there is a change in the level of carbon dioxide in one or more gases analyzed, the maximum modulus of the specified change in the level of carbon dioxide can be obtained. Data and reference bandpass filters 356 and 358 are glued into slots 360 and 362 of light block 370 . When light block 370 is connected to the detector circuit board, data and reference bandpass filters 356 and 358 are aligned with data and reference detectors 340 and 345, respectively.

All energy propagating along optical path 56 and reaching detector assembly 300 at wavelengths greater than all and at the same interval of the selected intercepted infrared beam is reflected to data detector 340 . Similarly, shorter wavelength energy is transmitted through beam splitter 286 to reference detector 345 . Because of this, the physical relationship between detectors 340 and 345 described above, and the size and configuration of the energy intercept sensing elements of those detectors, both detectors "see" the same image of the beam of electromagnetic energy rays. This significantly improves the accuracy of the detector assembly 300 .

In other words, optically, with the data and reference detectors 340 and 345 positioned precisely relative to each other and the beamsplitter 352 arranged in the manner described above, these elements behave 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 a spatially identical pattern. By optically making the two detectors 340 and 345 spatially coincident, and simultaneously electronically sampling the detector outputs, it is also possible to effectively eliminate the effect of the subsequent ratio of the data and reference detector output signals on the The accuracy of foreign material collected by any of the track coupler optical windows 58 and 60, the window 460 of the source assembly, or the window 364 of the detector assembly 300 described below may be adversely affected.

Electromagnetic energy in the light beam propagating along optical path 56 reaches beam splitter 352 through aperture 366 defined in front wall 339 of light block 370 . Infrared radiation transparent lens 364 , typically made of sapphire, spans aperture 366 and prevents carbon dioxide and other foreign materials from entering the interior of light block 370 . The lens 364 is bonded to the light block in any convenient and suitable manner.

The infrared ray source assembly 400 will now be described with reference to FIGS. 12 and 13 . Infrared radiation source assembly 400 emits infrared radiation in the form of beam 480 (see FIGS. 14 and 16 ) that propagates along optical path 56 . The infrared radiation source assembly includes an infrared radiation emitter 445 , converters/lead frames 446 and 447 disposed in the light source ring assembly 420 , and a lens 460 disposed in a lens holder 440 connected to the light source ring assembly 420 . The infrared ray emitter 445 includes a substrate formed of a low thermal conductivity material. This is important because it significantly reduces the energy required to heat the emitter to operating temperature. When current is applied across the emissive layer 448 of the emitter 445, the emissive layer and substrate are heated, the substrate grows or increases in length due to thermal expansion, the growth is accommodated rather than constrained by the elastic adhesive. Thus, the stresses that would be exerted on the emitter if the two ends were rigidly fixed are avoided, which eliminates possible damage to the emitter or complete failure of the element if high mechanical strains are applied.

Emitter 445 Energizing the emitter 445 of the light source assembly 400 heats it to an operating temperature at which it emits infrared radiation over a suitable bandwidth range by affecting a current from a suitable power source through the emissive layer 448 . The power source is connected to the emitter layer 448 via conductive leads 451 and 452 . The leads are soldered or otherwise physically and electrically connected to opposite ends of the bonders 446 and 447 .

Adapters 446 and 447 are installed into source ring 420 of source assembly 400 . Due to the heating of the emission layer 448 by the infrared radiation emitter 445 , the environment in which the component operates can reach an increased temperature. The source ring is therefore made of a polymer which remains structurally stable at the temperatures to which the infrared radiation emitter 445 is operating. In the depicted exemplary embodiment, the source ring 420 has a cylindrical structure including an integrated wall 454 and a bottom 453 . Protruding in the same direction from bottom 453 are component placement bosses or protrusions 456 , 457 , 458 and 459 . Spaced protrusions 456 and 457 and complementary spaced protrusions 458 and 459 surround opposite sides of adapters 446 and 447 . Bosses or protrusions 461 and 462 separate the adapter portions while providing a gap therebetween to electrically isolate the two adapter portions. This is necessary so that a voltage can be developed on the emitter 445 to allow the operating current to flow through the emitter.

Referring now to FIGS. 14-16 and FIGS. 12 and 13 , infrared radiation output by infrared radiation emitter 445 emitting layer 448 is focused and propagated along optical path 56 by lens 430 disposed within lens holder 440 . The exterior material is separated from the interior of the infrared radiation source assembly 400 by a sapphire or other infrared radiation transmissive window 460 spanning and closing the aperture in which the lens 430 is disposed. Window 460 is bonded or otherwise bonded to a shelf-like protrusion or slot 442 formed in lens holder 440 of infrared radiation source assembly 400 .

The energy of the particular entrainment is absorbed by the gas of interest (usually carbon dioxide) flowing through the airway adapter to a degree commensurate with the concentration of the gas. Thereafter, the beam of attenuated infrared rays passes through the aperture 306 in the front wall 308 of the detector portion of the housing 210 , is intercepted by the beam splitter 352 , and is either reflected towards the data detector 340 or transmitted to the reference detector 345 after being reflected by the mirror 354 . Bandpass filters 356 and 358 in front of those detectors limit the energy arriving thereon to specific (and distinct) energy bands. Each detector 340 and 345 outputs an electrical signal commensurate in magnitude with the intensity of energy striking that detector. This signal is amplified by the electronic circuitry on the detector system circuit board 310 and transmitted to a digital signal processor on the board portion 225 of the flexible circuit 230 . The processor typically scales the detector's signal to produce a third signal that accurately reflects the concentration of the gas being monitored.

Optical path 56 is shown, the distance being traversed by infrared rays between windows 58 and 60 provided in holes 52 and 54 , respectively, and within the overall "U" shaped box element 48 of airway adapter 40 . The optical alignment features of bottom 250 are readily apparent from the cross-sectional view. A feature of the lens holder 440 attached to the source ring assembly 420 is used to properly align the source assembly 400 in the base 250 . Similarly, features of detector optics assembly 350 are used to properly align detector assembly 300 in base 250 .

A luminescence quenching optical system 236 is assembled to the luminescence quenching measurement circuit board 235 . Luminescence quenching measurement circuit board 235 includes circuitry that drives excitation source 243 and measures the response of detectors 238 and 239 using amplitude or phase based detection techniques. An exemplary luminescence quenching optical system 236 includes an excitation source 243 and detectors 238 and 239 on each side of the excitation source 243 (see FIG. 29 ).

Figure 15 is a flattened view of the gas measurement system assembly before it is placed in the enclosure. Prior to assembling detector assembly 300 and source assembly 400 to "U" shaped bottom 250 , these assemblies are physically and electrically connected to flex circuit 230 . The detector assembly 300 is connected to the board portion 226 of the flex circuit 230 with a detector flex jumper 380 (see FIGS. 5 and 8 ). The ends of leads 443 and 444 ( FIG. 12 ) of source assembly 400 and the connector of cable 120 are connected to board portion 227 of flexible circuit 230 . To assemble the flattened electro-optic assembly 222 to the base 250 , the source assembly 400 and the detector assembly are attached to the base 250 . The board portion 225 of the flexible circuit 230 rests on top of the “U” shape of the bottom 250 . Plate portion 228 is folded to accommodate detector assembly compartment 254 , while plate portion 227 is folded to accommodate source assembly compartment 253 .

Figure 16 is the ray trace of the light path in the combined gas measurement system. Ray 480 in FIG. 16 is merely descriptive and is represented as if the emissive layer of emitter 445 was a point source. Infrared rays originating from the emitter 445 are collimated by the hemispherical lens 430 . The shape of the airway side of the lens is used to "focus" the rays into parallel lines. The rays strike infrared absorbing gases and substances that are within the airway adapter and are absorbed and scattered. The remaining radiation passes through the window of the airway adapter and enters the detector assembly 300 . The rays pass through lens 364 and are collimated/focused onto beamsplitter 352, where approximately half of the rays are reflected and pass through filter 356 and detector 340, while the other half are transmitted and reflected by mirror 354 to filter 358 and toward the detector 345.

Figure 17 is a block diagram of a gas measurement system 500 in accordance with the principles of the present invention. Microprocessor 510 provides the control, measurement and signal processing functions of the present invention. An exemplary processor is a TMS320F2812 DSP manufactured by Texas Instruments. Microprocessor 510 provides a source timing signal to source assembly 400, which is driven by a 5.0 VDC pulsed voltage in unipolar mode. Source emitter monitor 511 monitors the source pulse width and maintains it within an allowable window. A system reset generator 520 is employed during the power up sequence so that the processor is only reset when a stable voltage is reached and during the power down sequence so that an orderly power down sequence will occur.

An executable program, which may be stored in electrically erasable programmable read-only memory (EEPROM) 530 or elsewhere, is transferred to microprocessor 510 . The data and reference channel signals originating from detector assembly 300 are amplified by digital attenuation 540 prior to analog-to-digital conversion within microprocessor 510 . Detector heater 590 located within detector assembly 300 is controlled by microprocessor 510 through a feedback loop. The low level signal from the detector is AC coupled, amplified and level shifted to fully acquire the signal. Double sampling and holding the plateau in the ADC allows simultaneous sampling of the data and reference channels. Active gain and offset adjustments compensate for optical and electronic variables in the signal chain. The detector heater driver controls sending energy to the detector while the detector thermistor driver provides thermistor signal to the processor. A control algorithm such as a PID controller is used to regulate the temperature, typically between 40°C and 50°C, to within ±0.02°C. The detector heater is powered by a +5V DC power supply, which is also used to power the analog circuit regulator. The window heater 245 includes a temperature detection element and a heating element. Electronics on circuit board 235 in conjunction with the microprocessor control the delivery of power to the heating elements. A control algorithm in the microprocessor 510 employs temperature sensing to maintain the temperature of the heating element at a temperature well above the ambient temperature within the airway adapter. CODEC 555 is a decoder and encoder with integrated digital-to-analog converter and analog-to-digital converter. CODEC 555 coupled to microprocessor 510 uses the outputs of detectors 238 and 239 to modulate excitation source 243 in a manner to perform phase-based lifetime measurements. The serial driver 570 communicates bi-directionally using transmit and receive lines, denoted Tx and Rx, respectively. Providing signal returns and analog and digital grounds, the power supply 560 receives power from the VSRS and VA lines.

The above exemplary embodiment of the present invention shows an optical assembly of an infrared detector system having a linear configuration, which includes a single beam splitter, a single mirror, two filters and two detectors. This configuration is ideal for detecting a single gas flowing through the sample chamber. However, there is a growing need to measure additional gases with transducers of the same size as those used for single gas measurements. To this end, the present invention contemplates other embodiments of gas measurement systems that include an infrared spectrometer portion capable of measuring multiple gases. For example, a four-channel system will allow the quantification of concentrations of carbon dioxide, nitrous oxide, and certain anesthetics along with a reference channel. The present invention is also suitable as an efficient non-dispersive infrared multi-channel gas analysis arrangement employing one or more of the following novel features and combinations:

a) Multiple dichroic beam splitters that split the spectrum into binary sequences, with narrow bandpass filters to select specific wavelengths;

b) Combining two or more two-color separators on a single substrate

c) a geometric configuration in which all detectors are arranged on a single plane and a multi-channel single-turning mirror can be employed;

d) a broadband bandpass filter instead of two dichroic beam splitters;

e) annular focusing mirrors, and associated sapphire or germanium lenses; and/or

f) Lenses located on both sides of the beam splitting element to compactly provide independent control of reflected and transmitted light. *

Fig. 18 is a schematic diagram of an exemplary embodiment of an optical system disposed in a linear configuration in accordance with the principles of the present invention. The optical system in this example consists of four channels, each with a narrow bandpass filter and detector. Each filter/detector assembly 611, 612, 613 and 614 employs a similar detector, but each filter has a different bandpass. After passing through the sample chamber, the beam of the infrared source enters the optical system. This light beam is indicated with reference numeral 600 in the figure. The light beam 600 strikes a first dichroic beam splitter 601 . The first dichroic beam splitter 601 may be configured to pass either the shortest wavelength of interest or the longest wavelength of interest. All other wavelengths will be reflected. Other wavelengths or channels are split from the reflected beam by second and third dichroic beam splitters 602 and 603 in turn. The order of the splitters is somewhat arbitrary. The final element, mirror 604 , reflects the final channel to filter/detector assembly 614 . Using this mirror allows all detectors to be in the same plane (ie co-planar).

Figure 19 depicts the filter characteristics of the short (low) bandpass splitters 605, 606 and 607 as a function of wavelength, relative to the filter characteristics of the bandpass filters 615, 616, 617 and 618 per channel of the linear system of Figure 19 feature. Each detector has a narrowband filter to select the desired wavelength for detection, with more features than can be accomplished with dichroic beamsplitters. Note that this logic can be reversed, meaning that the first splitter can pass the longest wavelength 618 while reflecting the other wavelengths to filters 615 , 616 and 617 . Then, the lower splitter can be short pass, where the sequence would be 617, 616, and 615, or it can be long pass, where the sequence is 615, 616, and 617.

Alternatively, the long and short bandpasses can be mixed in some order. Note that dichroic beamsplitters are employed instead of more conventional broadband beamsplitters to substantially improve the amount of signal energy that will reach the detectors, especially the final detector. This linear system has the advantage of a simple design and all detectors are on the same plane. However, the beam extends substantially along the path length to the final detector, so the energy collected by the final detector is less than that of the preceding detectors.

Fig. 20 is a schematic diagram of an optical system with a zigzag structure. This system takes advantage of the fact that a dielectric bandpass filter will reflect all wavelengths not transmitted. In essence, there is a conservation of energy. In the case of a zigzag, the first element is a mirror 621 . Each splitter 626, 627, 628 and 629 is a narrow bandpass filter. Not all energy selected from a particular channel is reflected to other channels, so the order of filter/detector components 622, 623, 624 and 625 is arbitrary. Note that each filter must be designed to operate at a chosen angle (typically 40° to 45°). Because the narrow bandpass filter performs the dual function of ordering the channels and narrowly defining the desired wavelength, the system has a shorter path length and a lower parts count. The detector is now on two planes, but the detector components are the same. The system shown shows the optical path from the light source to the final detector on the same plane. For ease of packaging, the assembly behind the mirror 621 can be rotated 90 degrees about the optical axis so that the optical axis of the light source is perpendicular to the zigzag plane.

Fig. 21 is a schematic diagram of an optical system with a square array structure. A dichroic beam splitter is employed in a more straightforward binary selection process. For example, using the filter and beam splitter characteristics shown in Figure 21, the first beam splitter 631 can be set at 4 microns to split the spectrum of interest in half. The reflected halves are separated again at 4.4 microns, the reflected portion goes directly to narrow bandpass filter/detector assembly 632 , while the passed portion is then reflected at mirror 636 to narrow bandpass filter/detector assembly 633 . The passing half of beam splitter 631 is reflected at mirror 638 to beam splitter 637 set at 3.45 microns. As in the first described leg, beam splitter 637 splits the beam and directs the beam to narrow bandpass filter/detector assemblies 634 and 635 . The paths of beam channels 1 and 2 and channels 3 and 4 are rotated about the optical axis at mirror 636 and beam splitter 631, respectively. By "rotating the legs" of the device, all detectors can be placed very close together on the same plane. Additionally, in this system, the two mirrors, shown as mirror 636, can be fabricated as a single piece, and the beam splitter, shown as beam splitter 637, can also be formed on a single substrate.

It should be noted that the combined beamsplitter can be configured as a pair of overlapping dichroic beamsplitters, one on each side of the sapphire substrate, or it can be configured as a wideband pass filter where the bandedges form the wavelength division function. The systems described below may be similar in general structure, but include focusing elements in the form of sapphire lenses, concave spherical mirrors, or non-concave spherical mirrors.

The advantage to the system of adding focusing elements is the greatly improved energy collection efficiency at each detector. Without focusing elements, the light beam from the source would be much larger than the detector at the detector plane. The oversize is due to two reasons: system magnification, and distortion. The ratio of the numerical aperture on the light source to the numerical aperture on the detector is the magnification. The numerical aperture is the sine of the refractive index beam half-angle time (1 in this example). Depending on where the focus is set, the magnification ranges from 5 to 7. The source diameter is about 0.02", so the image on the detector plane will be in the range of 0.16" to 0.2". But the detector diameter is typically 0.08" (larger detectors are possible, but cost increases rapidly with size ). Also, while the source lens produces a very good image in the center of the field, the points at the edge of the source are distorted, which increases the base image magnification. However, if a positive focusing element can be placed close to the detector, the magnification can be reduced radially, and the distortion can also be reduced in an absolute sense. In example systems, compressing the beam can improve detection efficiency by a factor of four or more. Note that it is not feasible to make a good image on the detector with a simple lens given the deformation of the beam, but in practice a good image is not required since the goal is simply to collect as much infrared radiation as possible.

Figure 22 is a schematic diagram of an optical system having a linear system configuration including lenses in the optical assembly. This configuration is similar in arrangement to the linear configuration of FIG. 18 with the addition of lens 645 interposed along the optical path, typically between beamsplitters 642 and 643 and filter/detector assemblies 652 and 653 . The function of the lenses is to compress the beam energy to the detector assembly 653 and detector assembly 654, which will improve detection efficiency in these channels. The function of the lens is to reduce the magnification of the system. Additionally, lenses 655-658 can be added to each channel, further reducing magnification and improving and balancing the efficiency of all detectors.

23 is a schematic diagram of an optical system having a zigzag configuration in which the lens is again included in the optical assembly. In this configuration, which is essentially a modification of the configuration shown in Figure 20, lenses are added at each channel to compress the beam size. If a single lens is added between the beamsplitter and detector, only the transmitted beam will be affected, and the reflected beam will be magnified more than desired for the final pass. But if you add a single lens in front of a beamsplitter strong enough to compress the beam for that detector, the effect on the reflected beam will be doubled and will be too strong.

The present invention solves this problem by splitting the lens into two elements, with one section on either side of the narrow bandpass filter. For example, split lens/filter assembly 669 includes lenses 666 and 668 and filter 667 . By splitting the lens on each channel in this way, the transmissive and reflective parts are each subjected to the effect of a full lens. Alternatively, the two lenses on each channel may be different such that, for example, the transmitted beam is compressed more than the reflected beam. Note that with this system the dichroic beam splitter is eliminated.

Fig. 24 is a schematic diagram of an optical system with a bent structure. The structure is similar to a square array in that a dichroic beamsplitter is used to split the beam by wavelength in a binary fashion. The dichroic beam splitter 682 performs the first split. The reflected beam reaches reflector 681 . This is one of four focusing mirrors 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 with a high angle of incidence will create two distinct foci, one in the plane of incidence and the other perpendicular to the plane of incidence. In other words, such a mirror will produce astigmatism. Astigmatism can be corrected by making the radii of curvature different in the two axes. Aspherical is a general term for non-spherical surfaces. The mirrors shown here are rings, a subset of the general category. In this case, even though a good image is not required, the aspheric mirror produces a more uniform circular beam pattern.

The reflected and refocused beam is split again at dichroic beam splitter 675 . Again, the reflected beam is refocused onto the bandpass filter/detector assembly 672. The transmitted beam reaches the filter/detector assembly 671 . The light beam transmitted from the beam splitter 682 is focused again by the focusing mirror 683 and split again by the beam splitter 678 . Like the other two channels, the beam reaches filter/detector assembly 674, or passes through focusing mirror 677 to filter/detector assembly 673. Note that this system offers high collection efficiency and a compact single-plane detector array.

Fig. 25 is a schematic diagram of an optical system having a serpentine structure. The "snake" configuration is similar to a linear array, except that focusing mirrors 691-694 are added to each channel. The initial division is performed by dichroic beam splitter 681 , followed by beam splitters 682 and 683 and mirror 684 . Focusing mirrors can be spherical, but collection efficiency is greatly improved with aspherical mirrors. In an exemplary embodiment of the invention, the mirror is constructed in a single long pattern. Filter/detector assemblies 685, 686, 687 and 688 consist of narrow bandpass filters and detectors, as in the other previously described embodiments.

Fig. 26 is a schematic diagram of an optical system with a channel structure. Infrared energy can be distributed to the planar array of detectors in different ways. Energy from source 698 may be directed to tube 696 by mirror 699, or may be channeled optically. If the interior 695 of the tube is a mirror, and if the tube is long enough (on the order of ten times the diameter), the energy at the end of the tube will be geometrically well mixed. That is, any configuration of the input beam will not be detectable on output (although the total energy level will drop), eg due to insufficient airway or liquid falling onto the airway window. Similarly, if the input beam is not exactly in the correct position or at the correct angle, there will be virtually no effect at the output.

The concept of this embodiment is to place a planar array 697 of narrow bandpass filters and associated detectors at the output. The effect of the tunnel is to distribute the energy symmetrically to the detectors. Note that the energy at the output is radially symmetric, but will not be uniform over this area. Since the tube output is circular, but the array is square (for four detectors) and further the area of each detector is a fraction of the total output area, the described system is not very efficient. The loss of efficiency can be mitigated by square-shaped tubes to match the detector array or alternatively placing a set of channels at the output. These channels will receive all the energy of the pipeline as a group and divide it in various ways to match the number of tunnels and converge the energy down to the detector size. In this figure, the sides of the tube (and source mirror) are cut away for illustration. The detector plane does not show the array.

FIG. 27 is a side view of an embodiment of a four-channel optical system 700 disposed within a linear structure on a substrate 705 . Infrared rays enter detector/optical assembly 700 by first passing through lens 710 . The infrared rays are then successively split and reflected by beam splitters 743 , 753 and 763 . The transmitted infrared rays pass through filters 740, 750 and 760 before entering detectors 745, 755 and 765, respectively. The remaining infrared rays reflected by focusing mirror 720 through beam splitter 763 pass through filter 770 and onto detector 775 . Heaters 735 and 730 are used to maintain detector block 780 at a constant temperature.

In the embodiments described above, multiple absorption-type detector assemblies are provided to detect multiple gas components in the gas flowing into the sample chamber. It will be appreciated that the present invention also contemplates providing a luminescence quenching type gas detector with multiple gases, either alone or in combination with absorption type detectors. A multiple luminescence quenching type gas detector would require multiple sources, detectors, filters and multiple chemistries to be placed on the substrate of the airway adapter.

FIG. 28 is a perspective exploded view of the gas measurement system optical assembly 240 and the luminescence quenching measurement circuit board 235 with the bracket 232 . Detector filter 233 removed from luminescence quenching optics 236 is shown in FIG. 29 and incorporated into luminescence quenching measurement circuit board 235 . Luminescence quenching measurement circuit board 235 includes circuitry to drive excitation source 243 and measure the response of detectors 238 and 239 using known detection techniques.

Fig. 29 is a perspective exploded view of a luminescence quenching measurement circuit board. The exemplary luminescence quenching optical system 236 includes an excitation source 243 , detectors 238 and 239 on each side of the excitation source 243 , a detector filter 233 , a selective excitation source filter 241 and a shield 234 . All components are arranged on the same plane allowing to reduce size and weight. An exemplary excitation source consists of a green light emitting diode. Excitation source 243 and detectors 238 and 239 are separated from each other by electrical shielding and optical filters. An exemplary detector consists of a photodiode. It will be appreciated that the present invention contemplates providing a ring of photodetectors surrounding or partially surrounding source 243 . The ring can be a single detector or multiple detectors and can have any suitable pattern, eg circular, square, triangular, rectangular, etc.

In an exemplary embodiment, the detector filter 233 is a rectangular filter structure having an aperture 229 through which radiation is emitted from the excitation source. The optical characteristics of the detector filter are such that the following wavelengths of radiation are substantially transmitted through the filter: such radiation is involved in the luminescence quenching of sensitive membranes/chemicals, and the response to contact with the gas or gases under test will not involve this The interacting rays are essentially not transmitted through the filter. The detector filter may be bandpass, highpass, lowpass, or any other filter type known in the art. Additionally, an optical excitation source filter 241 may be used to limit radiation emission to wavelengths of radiation that are excited by the sensitive film thereby preventing unwanted wavelengths from reaching the sensitive film.

The sensitive membrane sensitive to the gas of interest is preferably disposed in a plane parallel to and shifted from said first plane of the exemplary luminescence quenching optical system 236 . To minimize unwanted interactions between the excitation source and detector, a shield 234 is placed around the excitation source. The inner surface of shield 234 in the exemplary embodiment is substantially reflective to radiation emitted by the excitation source and serves two purposes. This allows it to redirect incoming light back to the sensitive membrane while improving the efficiency of the system. Additionally, excitation sources such as LEDs emit light at a greater angle than the sensitive film subtends. The shield is preferably shaped to block light from directly reaching the detector and affecting luminescence measurements.

In the exemplary embodiment shown, radiation emitted from excitation source 243 is transmitted through filter 241 and through hemispherical window 247 and is incident on the sensitive membrane. Depending on the concentration of oxygen, the sensitive membrane emits radiation at different wavelengths, which is transmitted back through the window 247 and filtered by the detector filter 233 and measured by the two detectors arranged in the detector filter 233 .

In addition, an index matching layer (not shown) is optionally placed between the detector and the detector filter to minimize reflection losses. The radiation emitted by the sensitive membrane is emitted in all directions and only a small fraction of the emitted radiation is directed towards the detector. This ray is further attenuated at each interface along the optical path due to Fresnel reflections. Therefore, filling the air gap with a material such as an index matching material allows minimizing this reflection loss.

The heater flex circuit 245 is electrically connected to the luminescence quenching detection circuit board 235 as described above. Because temperature affects the amount of light emitted by the sensitive film, temperature control or compensation is required. To maintain a constant temperature across the film, window heater 245 is in thermal communication with the flat side of window 247, typically sapphire. This heater maintains the window 247 at a constant temperature, which in turn maintains the temperature of the sensitive membrane. The window heater 245 is designed as a ring to remain outside the light path. The window 247 is hemispherical rather than planar to improve thermal contact with the sensitive film. The intimate contact between the two elements and the curvilinear profile also has the effect of improving the amount of light transmitted through the sensitive film and returned to the detector. As noted above, an exemplary embodiment of a luminescence quenching optical system 236 suitable for use in the present invention is disclosed in the '451 application.

It will be appreciated that the luminescence quenching features of the present invention and the absorbing features of the present invention may be employed alone or in combination and in lateral flow configurations.

Consider now several alternative configurations of the invention. For example, the present invention contemplates the use of prisms or aspherical lenses prior to the excitation source to more evenly distribute light across the sensitive film. It is also contemplated to interchange the positions of the excitation source and the detector, ie employing a single large detector surrounded by two or more excitation sources. The invention also contemplates turning or tilting the detector so that the detector face is substantially perpendicular to the rays emitted from the luminescent material to improve detection efficiency.

The present invention also contemplates providing a display 800 (see FIG. 3 ) on the housing of the gas measurement system. The display may be any suitable display, such as LEDs, OLEDs, LCDs and the like. Providing a display on the hood on the gas measurement system allows the physician or other user to display warning or report messages, waveforms, trends and other relevant information directly from the unit near the patient without having to reposition itself to see the conventional monitor screen, because This is usually necessary in conventional systems where the monitor screen is usually several feet away from the patient. This is especially important in adverse medical events requiring urgent attention and physician response.

Although the invention has been described in detail for purposes of illustration based on what are presently considered to be the most practical and preferred embodiments, it is to be understood that such detail is used for that purpose only and that the invention is not limited to the disclosed embodiments, but rather is intended to cover Changes and equivalent arrangements within the spirit and scope of the claims. For example, it is to be understood that the invention contemplates combining, where possible, one or more features of any embodiment with one or more features of any other embodiment.

Claims (7)

1. a gas measurement system (100) comprising:

(a) cover (250) is suitable for being fixed on the air flue contact maker;

(b) a luminescence quenching gasmetry assembly (236) is arranged in the cover, comprising:

(1) one be arranged in first plane source (243) and

(2) be arranged on first detecting device (238) on first side in described source (243) and be arranged on second detecting device (239) on second side in described source, wherein said first detecting device (238) and described second detecting device (239) are arranged in described first plane;

(c) wave filter (233) on described first detecting device (238) and described second detecting device (239), wherein said wave filter is by the beam wavelength relevant with luminescence quenching and stop other wavelength basically; And

(d) light shield (234), be arranged on described source at least a portion around;

Wherein said wave filter (233) comprises the hole (229) that is used for from the ray emission of described source (243).

2. the system as claimed in claim 1, wherein cover is a U-shaped totally.

3. the system as claimed in claim 1 also comprises a processor (510) that is arranged in the cover, wherein processor is programmed to measure the gas componant of air-flow in the air flue contact maker based on the output of detecting device.

4. the system as claimed in claim 1 also comprises the infrared ray absorbing gasmetry assembly (240) that is arranged in the cover.

5. system as claimed in claim 4, wherein cover comprises being U-shaped totally, has the structure of first leg and second leg, wherein infrared ray absorbing gasmetry assembly comprises the source component that is arranged in first leg and is arranged on detector module in second leg, and wherein luminescence quenching gasmetry assembly is arranged in the cover between first leg and second leg.

6. system as claimed in claim 4, wherein luminescence quenching gasmetry assembly comprise with conduit in the sensitive membrane of airflow connection.

7. system as claimed in claim 6, wherein said sensitive membrane is arranged on the air flue contact maker.

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