FR2981158A1 - Gas analysis module for use in anesthesia ventilator for analyzing concentration of compounds present in e.g. inspiratory flow of patient, has hollow optical fiber guiding infra-red signal emitted by transmitter to detector - Google Patents

Abstract

The module (4) has a sampling line (41) provided with an inlet (41a) and an outlet (46b). A detection module (44) is arranged on the sampling line between the inlet and the outlet. The detection module includes an infra-red signal transmitter (442) to emit an infra-red signal. An infra-red signal detector (444) determines concentration of a gas compound contained in the gas. A hollow optical fiber (443) conveys to be analyzed gas from the inlet of the sampling line and guides the infra-red signal emitted by the infra-red signal transmitter to the infra-red signal detector. An independent claim is also included for a ventilation apparatus.

Description

The present invention relates to a gas analysis module for analyzing the concentration of one or more gaseous compounds present in the inspiratory and / or expiratory flow of an individual. Breathing patients with ventilators, whether temporarily in anesthesia for surgery or for longer periods in a critical care unit, requires reliable data for the care staff and relevant. These data contribute to the security of the act practiced on the patient or to the implementation of a therapeutic strategy. Exploitation of the patient's airway pressure exerted by the ventilator as a means of protecting the lungs from possible overpressure is a common example. However, there are other data, equally essential, that allow the specialist to intervene effectively in case of need, including the monitoring of the concentration of gas, whether administered to the patient or from this patient, c that is, expired. Thus, it is customary to monitor and track the oxygen fraction inspired by the patient or FiO 2 and / or, conversely, the fraction of oxygen exhaled by the patient or FeO 2. Fi02 corresponds to an oxygen concentration usually of 21% in air but may be in a higher proportion in the inhaled mixture after the air has been enriched with oxygen in the ventilator, via an additional supply of oxygen. Generally, the fraction inspired by the patient is greater than the exhaled fraction because, upon inhalation, the oxygen diffuses through the lungs to enrich the blood while at the same time an an inverse phenomenon in which CO2, the metabolic residue of tissues, crosses the lining of the lungs to be in the gaseous state and is partly expelled at the expiration of the patient. In a similar manner, we speak of a fraction of CO2 inspired and exhaled by the patient or FiCO2 and FeCO2, respectively. However, the real-time monitoring of these values is extremely useful for the practitioner because he participates in the assessment of the patient's condition and leads to the establishment of alternative ventilatory strategies. In addition to these indications, it is equally essential to have reliable values of the concentrations of the other compounds administered to the patient, for example in the context of a general anesthesia, in order to avoid the harmful consequences of under-dosing. or an overdose of anesthetic agents. Therefore, it is essential for the practitioner to have a precise and real-time knowledge of concentrations of nitrous oxide or N20, halogenated agents (Desflurane, Isoflurane ...) or xenon when these products are used. as anesthetic agents. In order to meet such a requirement, there are devices for measuring the concentration of the multiple compounds contained in a gas mixture.

Thus, CO2 and anesthetic agents (N20, Desflurane ...) can be monitored by devices, such as external modules, coming to connect mechanically and / or electrically to the fan. Most of these modules are based on a measurement by infrared (IR) technology, that is to say they use an infrared light source passing through a gaseous medium to be analyzed and then collected by a detector. Some chemical compounds react to such an exposure by absorbing under a specific wavelength a part of the radiation generally emitted at an IR wavelength of between 1 and 15 ig. For example, the CO2 absorbs the light wave at 4.26 ium, while the N20 absorbs it at 4.70 nm. On the other hand, some gases, such as oxygen or xenon, do not absorb IR radiation and can not be detected in this way. The higher the CO2 concentration, the more the light wave traveling through the gaseous media encounters the CO2 particles, is then affected by the absorption mechanism and loses intensity over the characteristic wavelength of the gas (ie 4, 26 ium for CO2). If we consider the detector as a filter, that is to say an element that measures the light intensity of the source at a given wavelength, then the higher the light intensity received, the lower the light intensity. the concentration of CO2, and vice versa. Such a characteristic of infrared detectors is made possible by associating them with pass-band filters which have the particularity of allowing a specific wavelength to pass while not allowing the other wavelengths to pass. For example, a detector equipped with a 4.26-μm bandpass filter can measure a CO2 concentration. This IR technology has the advantages of low drift over time and a very fast response time. Indeed, only the decrease in the intensity of the light source, after prolonged use, requires calibration of the measuring assembly and moreover, determining a given gas concentration requires only a few hundred milliseconds to compare with a ten seconds for the electrochemical cells. The implementation of these IR technology modules is via a deviated flow or side stream, commonly called "sidestream" in English.

To do this, a portion of the inhaled and exhaled gas flows are taken by the patient for analysis. In general, the sampling point is located closer to the patient, that is to say in part Y of the patient circuit. A sample line provides the connection between the sample point Y and the IR module so as to transfer the portion of gas to be analyzed by means of a pump placed in the analysis module in order to collect a constant quantity. of gas, typically 50 to 200 ml / min. The gas thus taken passes through one or more sources and IR detectors to determine the concentration of gases covered by the analysis module. A measurement of the oxygen present in the gas can also be carried out by using a different technology, often of paramagnetic type. The "deviated flow" technology is widely used in anesthesia where several gaseous compounds must be measured simultaneously. The module is most often integrated into the anesthesia station to allow its power supply and exchange with it measured data, especially for display purposes. However, the technology "deviated flow" is not free of drawbacks. First of all, the sampling line that sucks the gases in part Y of the circuit deprives the patient of a portion of the gas.

However, in pediatrics, this removal of a portion of the gas must be taken into account carefully because a sample of 200 ml / min by the pump may represent a significant portion of the volume administered to the child. Attempting to remedy this by decreasing the sampling rate is not simple and induces other problems, especially when the flow rate drops below 50 ml / min.

Indeed, a sampling rate of the order of 50 ml / min seems to be a low limit, because of the use of a chamber through which the gas flows. On either side of this chamber are the transmitter and the IR receiver, respectively. The IR light beam passes through the chamber during reflections on the walls of the latter and is absorbed at specific wavelengths by the gas molecules present. It follows then that the volume of the chamber is correlated in diameter to the size of the emitters and detectors and in length to the distance necessary for the light beam to hit enough molecules to correctly detect the concentration of gases. It appears in practice that a sampling rate lower than 50 ml / min has the consequence of not filling the chamber fast enough to quickly perform gas sampling after each other, which then adds a reaction time that is to say, a response time, too important to ensure effective monitoring in real time measures. The problem to be solved is therefore able to minimize the drawbacks associated with the sampling rate and the response time so as to be able to take samples, even at a low flow rate, that is to say <50 ml / min, in particular in pediatrics.

The solution of the invention is a gas analysis module comprising a sampling line with an inlet and an outlet, and a detection module being arranged on the sampling line between the inlet and the outlet, characterized in that said detection module comprises: an infrared signal transmitter adapted to and designed to emit an infrared signal; an infrared signal detector capable of and designed to determine the concentration of at least one gaseous compound contained in said gas to be analyzed, and a hollow optical fiber carrying the gas to be analyzed coming from the inlet of the sampling line and guiding the infrared signal emitted by the infrared signal transmitter to the infrared signal detector. Depending on the case, the gas analysis module of the invention may comprise one or more of the following technical characteristics: the infrared signal transmitter and the infrared signal detector are connected to a control unit, preferably a control card control unit. a pump is arranged on the sampling line between the detection module and the output. the infrared signal transmitter is integrated into an input medium and / or the infrared signal detector is integrated into an output medium. the infrared signal transmitter and the infrared signal detector are electrically connected to the control unit by means of electrical connections so as to transmit to the control unit at least one electrical signal representative of at least one concentration of the gaseous compound (s) analyzed. the pump is controlled by the control unit so that the flow rate of gas flowing through the sampling line is less than 50 ml / min. a filter element is arranged in the sampling line between the inlet and the detection module. the filter element comprises a porous membrane, preferably ceramic and / or having pores smaller than 100 μm. a first valve element, electrically controlled by the control unit, is arranged on the sampling line between the inlet and the detection module. the detection module further comprises a device for measuring the oxygen concentration of the gas. the infrared beam emitter comprises an optical lens. the hollow optical fiber has a diameter less than or equal to 1 mm, preferably a diameter less than or equal to 750 μm. a second valve element, electrically controlled by the control unit, is arranged on the sampling line between the detection module and the output. the hollow optical fiber is fixed by its input end to said input medium and by its output end to said output medium. Furthermore, the invention also relates to a ventilation apparatus comprising a gas circuit and a module according to the invention connected to said gas circuit, in particular an anesthesia ventilator.

The invention will now be better understood thanks to the following description given with reference to the appended figures in which: FIG. 1 is a general representation of an embodiment of a deviated flow gas analysis module according to the present invention; FIG. 2 is the representation of the module of FIG.1 with circulation of the gaseous mixture in a detection module; and - FIG. 3 is a detailed representation of the detection module of FIG. 2. Figure 1 is a general representation of a gas analysis module 4 according to the present invention integrated in a medical device 3, such as an anesthesia station for example. The gas analysis module 4 comprises a sampling line 41 preferably placed in Y part 21 of the patient circuit 2 in order to collect the gases inspired and exhaled by this patient 1 and this, for analysis purposes. A pump (not shown in Fig. 1) makes it possible to take the flow in piece Y 21 of the circuit 2 by means of the sampling line 41. As already explained, the sampling flows withdrawn into the modules according to the state of the typically vary between 50 and 200 ml / min.

In order to reduce this sampled flow rate (ie <50 ml / min), according to the invention, a sampling line 41 is used whose internal diameter, which conveys the gas, is very small, for example of the order of 300 microns. . In this case, the gas analysis module 4 can take a flow rate of the order of 5 ml / min, 10 to 40 times less than the flow rates taken according to the state of the art.

The propagation time of this flow in the sampling line 41 is then less than 1 sec per meter of line. It should be noted that with such a low flow (and volume) sampling and the simultaneous implementation of a sampling line 41 consisting of a material capable of removing the water vapor contained in the gaseous sample to analyze, typically a line coated NaftionTM marketed by Perma Pure Company, it can ensure a total elimination of excess moisture in the gas to be analyzed. It is thus possible to dispense with a water trap at the inlet of the gas analysis module 4, which simplifies the architecture of the device and exempts the user from periodically carrying out an emptying of the water trap acting as a dryer gas. Figure 2 shows in more detail one embodiment of a gas analysis module 4 according to the present invention. It can be seen that the sampling line 41 is directly connected to the inlet 41a of the module 4 without the interposition of a water trap. A pump 45 driven by a control card 50 via the electrical connection 45e, and placed at the end of the pneumatic arrangement of the gas analysis module 4, thus ensures the sampling of the gas at a fixed flow rate of a few ml / min, by Example 5 at 10 ml / min.

In order to avoid any contamination of the analysis module by the gas coming from the patient, a filter element 42 comprising a porous membrane is placed between the inlet 41a and the valve element 43. This membrane comprises, for example, pores of the order of 70 nm in diameter that prevent the passage of any contaminant, especially bacteria. For this purpose, it is possible for example to use the ceramic membrane marketed by Synkera Technologies under the trade name SM-73-50-30x30 which not only makes it possible to stop microorganisms having a size of more than 70 nm but also resistant (ceramic) and therefore lends itself perfectly to sterilization cycles, which allows reuse. The gas taken for analysis enters the gas module 4 through the pneumatic connection 42a having been previously cleared of possible pathogens by the filter 42. This gas then enters the valve element 43, also called zero solenoid valve and electrically controlled by the control card 50, via the electrical connection 43e, which ensures in normal operating condition the connection between the pneumatic line 42a and the detection module 44 for analysis. The detection module 44 is characterized by a very small volume while fulfilling the required detection requirements.

More specifically, the detection module 44 is formed of several components, namely an infrared transmitter 442 integrated with an input medium 441, a hollow optical fiber 443 carrying the gas and guiding the infra-red signal, and a detector 444 enabling the concentration analysis, itself integrated into an output support 446. Transmitter and infrared detector are also powered by the control card 50 through the electrical connections 442e and 444e, the 444e electrical connection also for transmitting a electrical signal representative of the concentration of the gas or gases analyzed in the control card 50. The detection module 44 makes it possible to perform a measurement of the IR type of carbon dioxide (CO2) type gas, nitrous oxide (N20) and halogenated agents, for example Halothane, Isoflurane, Enflurane, Sevoflurane, Desflurane, ...

The detection module 44 also contains a device 445 for measuring the oxygen concentration, the supply and collection of the electrical signal representative of the actual concentration of the oxygen gas being provided by the control card 50 and the electrical connection 445e. The pump 45, connected to the detection module 44 via the link 44a, sends the gas to the outlet solenoid valve 46 via the pneumatic link 45a. This output solenoid valve 46 thus closes the step of the pneumatic arrangement and redirects the gas to the pneumatic connection 46a and then the output 46b of the gas analysis module 4 in the normal operating condition to reinject it into the circuit 2. It can be seen that the pump can be associated with a flow sensor, controlled by the control card of the control unit 50, via the electrical connection 45e, so that the flow taken is kept constant, of the order of a few ml / min. The control card of the control unit 50 may also have the pressure and temperature information to which the sampled gas is subjected in order to effect the appropriate compensations of the measurements collected. In addition to these compensations, to guarantee the constant validity of the measurements may suppose to carry out periodically, a "zero" of the various sensors, that is to say to supply all the pneumatic disposition not of a gas coming from the part in Y 21 of circuit 2 but ambient air. This may be necessary in particular to calibrate the oxygen sensor 445. For this purpose, the zero solenoid valve 43 may be controlled by the control card of the control unit 50, via the electrical connection 43e, in order to make a connection between the ambient air inlet 43c via the pneumatic connection 43b and the detection module 44. The pump 45 then provides a sampling of the ambient gas, the oxygen concentration 02 is then equal to 21%. In order to avoid any pollution of the circuit 2 by a foreign gas (the ambient air), the outlet solenoid valve 46 can be controlled by the control card of the control unit, via the electrical connection 46e, in order to realize a connection between the pump 45, via the pneumatic connection 45a, and an exhaust air 46d, via the pneumatic connection 46c. Fig. 3 makes it possible to better understand why the volumes involved are small, that is to say much lower than in the analysis modules of known devices. In advance, it should be noted that the aspects of electrical connections of the components with the control card of the control unit 50 have been intentionally truncated so as to focus only on the mechanical aspect and not to hinder the understanding of the 'invention. In fact, Figure 3 describes the mechanical arrangement of the detection module 44. There are the inlet ports 441a and 446a outlet through which the gas to be analyzed is circulated due to the suction created by the pump 45. The emitter of the infra-red beam 442 is fixed to the input support 441. This emitter 442 comprises three elements making it possible to focus the IR beam, namely: the IR emitter itself, preferably of thermal type, for example the transmitter available from the company Cal Sensors under the reference CAL.SVF360-8M3, a lens 442a transmitting the infra-red beam and which makes it possible to collimate this IR beam at a given focal point, for example at a distance of 5 mm of the transmitter, a "cap" or securing element 442b which makes it possible to make the emitter-lens assembly 442a integral.

In order to optimize the response time of the gas analysis module 4, it is noted that the input support 441 is designed to optimize the volumes. For this purpose, this input support 441 can be manufactured in a material allowing the IR to pass and enclose the emitter in a chamber 441b having no contact with the gas to be analyzed.

This same input support 441 makes it possible to fix the hollow optical fiber 443 whose diameter will not exceed 750 μm. The positioning of this hollow optical fiber 443 is such that the focal point of the infrared transmitter 442 coincides with its input so that the entire light beam passes through the fiber 443.

By the clearance of the pump 45 which forces the gas to be analyzed to pass successively through the inlet 441a and outlet 446a, the interior volume of the optical fiber 443 is filled with a constantly renewed gas. The length of the optical fiber is determined according to the nature of the gas to be detected and the concentrations involved, that is to say typically from a few% by volume to a few ppm by volume. In the context of an anesthetic gas analysis module, the length of the optical fiber is a few cm, for example of the order of 10 cm. Similarly, the other end of the optical fiber 443 is fixed to the output support 446 so that it is closer to the infrared detector 444, also attached to the output support 446.

The IR light beam, attenuated at specific wavelengths by the many contacts it has had with the gas to be analyzed and more precisely with the compounds it contains, such as CO2 or N20, comes out of the fiber The infrared detector 446 can be provided with different channels each tuned to a specific wavelength in order to simultaneously measure the concentrations of the different gases present. As such, one can use the IR detector available from the company InfraTec under the reference LIM-054-. In order to obtain the measurement of the oxygen concentration, it can be seen that next to the infrared detector 444 is implanted a miniature sensor element 445 which, via a fluorescence principle, produces a rapid and accurate measurement of the concentration. in oxygen.

This sensor element 445 is also attached to the output support 446 and placed just before the outlet port 446a of the support. For example, the element referenced SMSI can be used by the company S4MS. It should be emphasized that it is perfectly possible to envisage additional provisions aimed at increasing the number of compounds detected, that is to say, in addition to oxygen, CO2 or N20 in particular. Thus, it is also possible to provide an additional detection module placed in series or parallel with the main detection module of the invention, for example to determine a xenon content, or to have one or more specific wavelength filters which would be on the principle of the rotating wheel, placed in front of the infrared transmitter 442. More generally, if the present invention has, for reasons of ease of understanding, taken the example of a gas analysis module used in anesthesia it will be apparent that any gas, as long as it responds with an absorption of infrared signals, can be detected by a module according to the present invention, by adjusting the length of the optical fiber and choosing an appropriate infrared detector Thus, mention may be made, inter alia, of the detection of nitric oxides (NO, NO 2) or even of carbon monoxide (CO). In all cases, according to the present invention, the optical fiber guides the light signal. IR emitter from the IR transmitter to the IR detector, which makes it possible to carry out a signal analysis within the control unit 50 and a determination of the concentrations or concentrations of the different compounds present in the gas flow. analyze. In addition to transmitting the wavelengths in the IR segment, the fiber also has the particularity of being hollow and filled with gas to be analyzed. By controlling the light signal from the IR emitter, it is possible to use an optical fiber whose diameter does not exceed 1 mm, which considerably reduces the volume required to analyze the gases. The analysis module 4 of the invention can be in the form of an independent box connectable to a ventilation apparatus comprising a gas circuit, in particular an anesthesia ventilator, in particular to the Y-piece of a such circuit, or according to the embodiment chosen, be integrated directly into such a ventilation device or the like.

Claims (15)

REVENDICATIONS1. Gas analysis module (4) comprising a sampling line (41) with an inlet (41a) and an outlet (46b), and a detection module (44) being arranged on the sampling line (41) between the input (41a) and output (46b), characterized in that said detection module (44) comprises: - an infrared signal transmitter (442) adapted to and adapted to emit an infrared signal, - an infrared signal detector (444) ) adapted for and designed to determine the concentration of at least one gaseous compound contained in said gas to be analyzed, and - a hollow optical fiber (443) conveying the gas to be analyzed from the inlet (41a) of the sampling line (41) and guiding the infrared signal emitted by the infrared signal transmitter (442) to the infrared signal detector (444). 2. Module according to the preceding claim, characterized in that the infrared signal transmitter (442) and the infrared signal detector (444) are connected to a control unit (50), preferably a control unit (50). to control card. 3. Module according to one of the preceding claims, characterized in that a pump (45) is arranged on the sampling line (41) between the detection module (44) and the outlet (46b). 4. Module according to one of the preceding claims, characterized in that the infrared signal transmitter (442) is integrated with an input medium (441) and / or the infrared signal detector (444) is integrated in a support of output (446). 5. Module according to one of the preceding claims, characterized in that the infrared signal transmitter (442) and the infrared signal detector (444) are electrically connected to the control unit (50) via links. electrical (442e, 444e) so as to transmit to the control unit (50), at least one electrical signal representative of at least a concentration of the gaseous compound (s) analyzed. 6. Module according to one of the preceding claims, characterized in that the pump (45) is controlled by the control unit (50) so that the flow of gas flowing through the sampling line (41) ) is less than 50 ml / min. Module according to one of the preceding claims, characterized in that a filter element (42) is arranged in the sampling line (41) between the inlet (41a) and the detection module (44). 8. Module according to one of the preceding claims, characterized in that the filter element (42) comprises a porous membrane, preferably ceramic and / or having pores less than 100 microns. 9. Module according to one of the preceding claims, characterized in that a first valve element (43), electrically controlled by the control unit (50), is arranged on the sampling line (41) between the input (41a) and the detection module (44). 10. Module according to one of the preceding claims, characterized in that the detection module (44) further comprises a device (445) for measuring the oxygen concentration of the gas. 11. Module according to one of the preceding claims, characterized in that the infrared beam emitter (442) comprises an optical lens (442a). 12. Module according to one of the preceding claims, characterized in that the hollow optical fiber (443) has a diameter less than or equal to 1 mm, preferably a diameter less than or equal to 750 itm. 13. Module according to one of the preceding claims, characterized in that a second valve element (46), electrically controlled by the control unit (50), is arranged on the sampling line (41) between the module detection (44) and the output (46b). Module according to one of the preceding claims, characterized in that the hollow optical fiber (443) is fixed at its inlet end to said input support (441) and at its output end to said output support (446). ). 15. Ventilation apparatus comprising a gas circuit and a module according to one of the preceding claims connected to said gas circuit, in particular an anesthesia ventilator.