EP1962935A2

EP1962935A2 - Respiratory anaesthesia apparatus with device for measuring the xenon concentration

Info

Publication number: EP1962935A2
Application number: EP06842137A
Authority: EP
Inventors: Christian Daviet; Richard Blandin; Noureddine Kissi
Original assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Current assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date: 2005-12-14
Filing date: 2006-12-11
Publication date: 2008-09-03
Also published as: WO2007068849A2; CA2633000A1; FR2894486A1; FR2894486B1; US20090090359A1; WO2007068849A3; US8141552B2

Abstract

Apparatus for respiratory anaesthesia of a patient by administration of a gas containing gaseous xenon, with a main gas circuit (CP) which is open or closed and has an inhalation branch (16) and an exhalation branch (18), means (1, 2) for supply of gaseous xenon to the inhalation branch (16) of the main circuit (CP), and means for determining the xenon concentration. The means (S6; M1) for determining the xenon concentration comprise at least one hot-wire sensor (S6-E; M1-D) having at least one electrically conducting wire in direct contact with the gaseous flow containing the xenon, calculating means (3; S6-D; M1-C) that cooperate with the hot-wire sensor(s) in order to determine the xenon concentration (Xe%) in the flow, means for generating an electrical current in order to generate a current in at least one hot wire, and means for voltage measurement that can measure at least one voltage value (V) at the terminals of at least one hot wire or at least one resistance arranged in series with at least one hot wire. The calculating means cooperate with the voltage measurement means in such a way as to determine the xenon concentration (Xe%).

Description

Ventilation anesthesia apparatus with xenon concentration measuring device

The present invention relates to an anesthesia apparatus using xenon with a device for measuring xenon concentration.

In other words, a device for measuring the concentration of xenon for integration into an anesthesia machine (integrated system), the ventilatory anesthesia apparatus comprising a main circuit for conveying gas flow for administering to the patient an anesthetic gaseous mixture containing xenon and a ventilatory system for ventilating the anesthetized patient.

Numerous ventilatory anesthesia machines can be used to perform the anesthesia of a patient undergoing surgery or the like, by administering to him by inhalation a conventional anesthetic gaseous mixture composed of N ₂ O, of halogenated agents ( for example SEVOFLURANE, ISOFLURANE, DESFLURANE, etc.). As such, reference can be made for example to EP-A-983771 and EP-A-1120126.

Of the gaseous mixtures that can be used, those based on xenon will be increasingly used with indications particularly adapted to fragile patients (elderly patients, operations, long, cardiac surgery, neurosurgery ...), in particular because of the incidence almost zero on blood pressure during anesthesia and the absence of side effects and harmfulness of Xenon.

However, anesthesia performed with xenon requires monitoring or monitoring of the xenon concentrations in the gas flow administered to the patient, that is to say requires to be able to determine in real time the concentration of xenon in the anesthetic flow.

As such, reference may be made for example to EP-A-1499377, EP-A-1318797 or EP-A-523315.

Currently, to measure a concentration of xenon in such a gas mixture, it is conventional to use a mass spectrometer or a chromatograph. However, these techniques have drawbacks of cost and especially difficulty of implementation because their integration into existing anesthesia devices requires very significant development and adaptation efforts.

The invention proposes to solve all or part of the aforementioned problems of the prior art, in particular the invention aims to provide a xenon respiratory anesthesia apparatus for accurately determining the xenon concentration delivered to the patient during anesthesia. in order to guarantee anesthesia efficacy and increased patient safety, while being of simple architecture and low cost.

In other words, the invention relates in particular to the problem of monitoring or monitoring the xenon gas concentrations in a gaseous mixture of xenon-based anesthesia containing, moreover, in a variable amount, that is to say 0 to 100% by volume, of one or more of the following main compounds: oxygen (O ₂ ), nitrogen (N ₂ ), nitrous oxide (N ₂ O), carbon dioxide (CO ₂ ), halogenated compounds isoflurane, enflurane, desflurane, sevoflurane or halotane, ethanol, and possibly traces or small amounts (<1%) of one or more of the following minor compounds: acetone, methane, carbon monoxide (CO), argon, helium...

In other words, the invention aims to provide particular means for determining efficiently, easily and with sufficient accuracy the xenon content in a flow of anesthetic gas, said means can be embedded on a new device or in an existing device, c. that is to say constitute an integrated monitoring system, or can be associated with existing devices, that is to say form an external and autonomous monitoring system.

For this purpose, the invention proposes an apparatus for ventilatory anesthesia of a patient by administering a gas containing xenon gas, comprising:

a main open or closed circuit gas circuit comprising an inspiratory branch for conveying a gaseous mixture containing xenon to the patient and an expiratory limb for conveying the gaseous mixture containing expired xenon by the patient, xenon gas supply means connected to the main circuit for supplying the inspiratory branch of the main circuit with a gas containing xenon,

- Xenon concentration determination means for determining the xenon gas content in at least a portion of the main circuit.

The apparatus according to the invention is characterized in that said xenon concentration determination means comprises:

at least one sensor with hot wire (s) comprising at least one wire of electrically conductive material, preferably of metal, in direct contact with at least a portion of the gaseous flow containing xenon, and

calculating means co-operating with the hot wire sensor (s) so as to determine the xenon concentration (Xe%) in said gas flow,

- Power generating means, preferably adjustable, adapted to and designed to generate an electric current, continuous or not, in the hot son or son of said at least one sensor hot wire (s) adjustable, and

voltage measuring means capable of measuring at least one voltage value across at least one hot wire or resistor placed in series with at least one hot wire, when said at least one hot wire is in contact with said gas flow and is traversed by an electric current of intensity (I),

and in that the calculation means cooperate with the voltage measuring means so as to determine, from the voltage measurement performed by said voltage measuring means, the xenon concentration (Xe%) in said flow.

Advantageously, the apparatus of the invention may comprise one or more of the following characteristics:

it comprises adjustable current generation means adapted to and designed to generate an electric current in the or each of the hot wires of said at least one hot-wire sensor, said current generation means being designed for and able to control the intensity of the electric current flowing through the hot wire or wires of the at least one hot wire sensor in such a way that whatever the composition of the gas passing through said at least one hot wire sensor (s), the intensity of the current flowing through the hot wire (s) is kept substantially constant and / or the temperature of the hot wire (s) of said wires. minus one sensor (s) with hot wire (s) is kept substantially constant. In other words, the current generation means make it possible to control the intensity of the current flowing through the wire, whatever the composition of the gas, in such a way that

- either, the intensity I is kept constant. In this case, the xenon concentration variations around the wire cause a temperature variation which leads to a variation in the resistance R of the wire. Since the current I is kept constant or approximately constant in the hot wire of the hot wire sensor (s), the voltage V (equal to R. I) across the hot wire of the hot wire sensor (s) will be measured. (s) to deduce the concentration Xe% by the linear curve corresponding to the flow D measured or known, as detailed below in the description.

- Or, the temperature of the wire is kept constant. In this case, the variations of the current I are adjusted to maintain constant or approximately constant, the temperature of the hot wire and thus compensate the effect of xenon concentration variations around the wire. If the concentration Xe increases, this increase will tend to cause an increase in the temperature of the wire, and the current generating means will then react to cause a decrease in the current I through the wire since such a decrease will tend to lower the temperature. wire according to Joule's law and thus converge towards a balance allowing to stay at constant temperature. On the other hand, if the concentration Xe decreases, this decrease will tend to cause a decrease in the temperature of the wire, and the current generation means will then react to cause an increase in the current I crossing the wire since this increase will tend to to increase the temperature of the wire and thus to converge towards a balance allowing to remain at constant temperature. We will then choose to measure the voltage V across a resistor Rs placed in series with the hot wire of the hot wire sensor (s), V being equal to Rs I, to deduce the concentration. Xe% by the linear curve corresponding to the flow D measured or known, as explained in detail below in the description.

the calculation means use at least one voltage value transmitted by the voltage measuring means and at least one flow rate of the anesthetic gas containing xenon to determine the concentration of xenon (Xe%) in said flow of gas.

- The hot wire sensor (s) is arranged on a branch line fluidly communicating with the main circuit. The connection of the branch line to the main circuit is made on the inspiratory branch and / or on the expiratory branch and / or in a site located immediately close to the patient's mouth, preferably at a connection site between the inspiratory branch and the exhalation branch of said main circuit for example at a Y connection piece or a bacteriological filter arranged on the main circuit, that is to say at the junction of the inspiratory and expiratory branches of the main circuit. This type of architecture using a branch line is known as the "type side-stream".

- Gas flow control means, in particular a suction pump, are arranged on the bypass line so as to obtain a known anesthetic gas flow rate, preferably a constant and / or stable gas flow rate. By constant and / or stable flow, it is meant that the flow rate varies at the most by a few% with respect to its average value, for example about 3% maximum, that is to say that the amplitude of variation of the flow rate , more or less, relative to said average flow rate has a negligible impact on the various sensors and measuring means used.

the gas flow control means make it possible to control the flow rate of the xenon-containing gas so as to ensure a desired, preferably constant and / or stable, flow rate of said gas carried by the bypass line and brought into contact with minus a hot wire.

- The gas flow control means comprise a gas suction pump, preferably the suction pump is associated with a control electronics of said pump, that is to say an electronics that manages the pump of suction to draw a desired flow rate in the main circuit, accurate and stable in time gas containing xenon to be analyzed. The ANDROS BGA4800 gas analyzer contains an example of such means associating a suction pump and a control electronics of the pump.

- The calculation means are incorporated in a gas analyzer module to be connected to the main circuit.

- one or more sensor (s) hot wire (s) is or are arranged (s) directly on the main circuit, for example, on the inspiratory branch and / or expiratory and / or at the junction between the branches the device comprising means for measuring the inspiratory flow rate and / or the expiratory flow rate and / or the main flow rate at the junction between the inspiratory and expiratory branches of the gas flow flowing in the main circuit, preferably those flow measurement means comprising an inspiratory flow sensor and an expiratory flow sensor, respectively arranged on the inspiratory and expiratory branches of the main circuit (also called "patient circuit"), for measuring the inspiratory and respiratory flows in said branches and transmitting the measurement signals thus obtained to control means for determining, in combination with the voltage measurements transmitted by the associated voltage measurement means one or more hot wire sensor (s) arranged directly on the main circuit, the xenon concentration in the inspiratory limb and / or the expiratory limb and / or at the junction between inspiratory and expiratory limbs. This type of architecture does not use a branch line and is known as the "main-stream type".

the calculation means are incorporated in the fan control module.

the sensor (s) with hot wire (s) comprises or comprise one or more platinum wires,

the hot-wire sensor (s) comprises or comprises several wires having different orientations relative to the gas flow, preferably two hot wires,

the calculation means are incorporated or form control means of the apparatus, the calculation means are incorporated or form control means of the gas analyzer module,

the calculation means comprise at least one electronic card and / or a computer program for carrying out all or part of the calculations making it possible to determine the xenon content in the anesthetic gas,

the apparatus comprises means for measuring a concentration of at least one additional gas distinct from Xenon such as I ¹ O ₂ , CO ₂ , N ₂ O, halogenated gases and ethanol; calculation device cooperating with the means for measuring a concentration of at least one additional gas to determine at least one of the following concentrations of Xenon: instantaneous, average, inspired, exhaled,

the means for measuring a concentration of at least one additional gas comprise means of the infra-red type (for additional gases such as CO ₂ , N ₂ O, halogen or ethanol) and / or of the paramagnetic or chemical type (for additional gases such as I ¹ O ₂ ).

the apparatus comprises means for measuring the relative humidity of the gaseous flow analyzed, the calculation means cooperating with these means for measuring the relative humidity in order to improve the calculation accuracy of at least one of the following concentrations; Xenon: instant, average, inspired, expired,

the apparatus comprises means for measuring the temperature of the gas analyzed, the calculation means cooperating with these temperature measuring means to improve the calculation accuracy of at least one of the following concentrations of Xenon: instantaneous, average, inspired and / or expired.

the apparatus further comprises an auxiliary gas circuit comprising an auxiliary inspiratory branch for conveying a breathing gas containing xenon to the patient by means of a manual insufflator, the means for determining the xenon concentration being adapted and adapted to be connected to said auxiliary gas circuit for xenon content determination, when xenon-containing gas is delivered to the patient via said auxiliary gas circuit, especially in case of shutdown or malfunction of the main circuit. the calculation means use the voltage (V) and flow (D) values to determine a xenon concentration (Xe%) in the gas flow from one or more linear curves stored in memory storage means; apparatus, preferably one or more lines of type: a. [Xe] + b = V where: V is the voltage, [Xe] is the xenon content and a and b are positive or negative coefficients corresponding to a given gas flow D.

the curve or curves, for as much flow value (Dn) as desired or necessary, are calibrated (with a flow rate established at the value (Dn) of gas whose xenon content is known, namely pure Xenon; and / or pure 02 and / or pure AIR) before storage and / or periodically updated and automatically during use of the apparatus.

the connection of the branch line to the main circuit is done at a site located in the immediate vicinity of the patient's mouth, preferably still at a connection site between the inspiratory branch and the exhalation branch of said main circuit, by example at a Y connection piece or a bacteriological filter arranged on the main circuit.

The invention also relates to a method of anesthesia of a patient in which an inhalatory gas containing xenon is administered in the patient's upper airways so as to perform a gas anesthesia of said patient, and the xenon content of the gas is determined. administered to the patient by means of an anesthesia machine according to the invention.

The present invention is therefore based on a use of one or more sensor (s) hot wire (s) to determine in real time, the instantaneous and / or average concentration of xenon present in the anesthetic gas.

The principle of measuring the flow rate of anesthetic gas by means of a sensor with hot wire (s) is as follows.

In general, when a given electric current (I) is passed through a wire (F) of metal (conventionally using a platinum wire) of given section (S), placed in a gas flow of anesthesia, at rest or not, ie at zero flow or not, its temperature stabilizes at a given temperature (T) and the voltage across the wire or a resistor placed in series with said wire is then established at a given value (V). Conventionally, but not mandatory, if it is desired to work with a hot wire maintained at a constant temperature, the current being controlled so as to obtain this characteristic, it is chosen to perform the measurement of voltage (V) across a placed resistor in series with said hot wire. In the case where it is desired to work at constant current, the choice is made to carry out the voltage measurement (V) at the terminals of the hot wire.

Therefore, when this metal wire, always traversed by the current (I), is placed in a flow (D) of anesthesia gas, devoid of xenon, the voltage across the wire or the resistance placed in series with said wire varies as a function f ₀ of the flow rate D according to the following formula:

V = _0.02 %, N20%, AA%, CO2%, HR, Tg ° (D)

The function f _o is also dependent on the content O ₂ % by volume in the gas, the content by volume N ₂ O% nitrous oxide, the content AA% of the anesthetic agent (halogen for example), the CO2 content of carbon dioxide and the relative humidity RH of the gas, the measured gas being at a temperature Tg ⁰ .

The function f ₀ 02%, N20%, HR, τ _g ° can be obtained conventionally by piece linearization or by a least squares approximation from calibration points (on a test bench) as numerous as possible. than necessary to achieve the desired accuracy.

This function f ₀ is, however, little dependent on the contents 02%, AA%, CO2% and N20%, and the relative humidity RH and the temperature Tg ⁰ of the gas.

Thus, by measuring the voltage V across the wire or the resistor placed in series with said wire traversed by the given electric current (I), one can deduce the flow (D) of anesthesia gas without xenon sweeping the metal wire by the formula:

D = fo 02%, N20%, AA%, CO2%, HR, Tg ° ^- (V)

Moreover, when this metal wire, always traversed by the current (I), is placed in a flow of anesthetic gas containing a non-zero proportion of xenon Xe%, the voltage V across the wire varies according to the following formula: V = f χ _e %, θ2%, N2θ%, AA%, co2%, HR, τG ° (D)

The current (I) can be pre-set in the factory or adjusted by user-initiated periodic calibration or machine to center the voltage measurement (V) within a given voltage range, calibration can be performed on a first reference gas (AIR or pure O2) containing no Xenon (0%) or possibly a second reference gas comprising Xenon in a significant amount (from 50 to 100% for example).

Thus, as previously, by measuring the voltage (V) across the metal wire traversed by the given current (I) or across the resistor in series with the wire, the gas flow (D) can be deduced therefrom. anesthesia with xenon content Xe% in which the metal wire is located using the formula:

D = f Xe%, O2%, N2θ%, AA%, CO2%, HR, Tg ° ^" (V)

Conventionally and simply, the hot wire sensor (s) can be made using a single wire placed for example perpendicular to the direction of the gas flow whose Xenon concentration is to be measured.

Non-mandatory, more sophisticated but more accurate, the hot wire sensor (s) can be made using two metal wires, one placed perpendicular to the direction of the gas flow (wire 1 traversed by a current 11) and the second more or less in the axis of the same gas flow (wire 2 traversed by a current 12), the formulas for connecting the voltage to the flow rate and to the different concentrations of Xenon, CO2, O2, AA, N2O and HR are as follows:

V = f Xe%, O2%, N2θ%, AA%, CO2%, HR, Tg ^(b (D) = f1 X0%, O2%, N2O%, AA%, CO2%, HR, Tg ° (D) Xθ%, O2%, N2O%, AA%, CO2%, HR, Tg ° (D) and

D = f Xe%, O2%, N2O%, AA%, CO2%, HR, Tg ° ^" (V)

The principle of measuring the flow rate of an anesthetic gas whose composition (and in particular the concentration of Xenon) is known by means of a hot wire sensor (s) having been described, reverses the reasoning leading to the realization of the Xenon concentration measurement system ... Knowing the flow rate or the flow measurement, we deduce the Xenon concentration in the gas analyzed. Thus, in a respiratory anesthesia apparatus, measurement of the xenon flow can be performed in the main flow or in a flow derived from said main gas flow.

When the hot wire (s) sensor (single-wire or two-wire metal) is placed in a stream derived from gas taken from the main gas stream (see Figures 1 to 4 below). after), such as a known anesthetic gas suction flow (Dc), obtained for example by means of a suction pump, it is possible to deduce the Xe% concentration of xenon inspired and / or exhaled and / or average and / or instantaneous from the voltage measurement V according to the following formula:

Xe% = h Dc, 02%, N20%, AA%, CO2%, HR (V) ^β V ^β C

V = f Xe%, O2%, N2θ%, AA%, CO2%, HR (Dc) (1) in which the function h DC, O2%, N2O%, AA%, CO2%, HR is found to be linear and can be obtained by calibration with a flow rate Dc of known concentration gas (pure Xenon and / or pure O2 and / or pure AIR)

Thus, for as many suction flow values Dc as desired or necessary, a linear curve is stored in the storage means of the device, ie a line of type b + a. [Xe] = V where V is the voltage, [Xe] the xenon content and a and b are positive or negative coefficients corresponding to each given value of flow Dc, a and b being obtained by calibration with a flow rate Dc of gas at known concentration (pure Xenon and / or pure 02 and / or pure AIR)

When used in operation, the calculation means then use the voltage values (V) and the flow rate value (Dc) to determine a xenon concentration (Xe%) in the gas flow from the stored linear curve. in storage means of the device corresponding to the selected flow rate value Dc.

Advantageously, the curves are, for as much value (s) of flow (Dc) as desired or necessary, are calibrated (with a flow rate established at the value (Dc) of gas whose xenon content is known, namely Xenon pure and / or pure 02 and / or pure AIR) before storage and / or periodically updated and automatically during use of the device. Figures 9a and 9b appended represent an example of such arrays of curves (for 3 Dc rate values) showing the linearity existing between the xenon content (Xe%) and the voltage (V).

Alternatively, when the single-wire hot or two-wire sensor is placed directly into the anesthetic gas flow infused into and / or exhaled by the patient, i.e., the main flow of gas (see Fig. 5 to 8), provided that the measurement of said main flow (Dp) of gas blown and / or exhaled, for example obtained in a regulatory manner by the inspired flow monitoring system, is available and exhaled with patient gas, it is possible to deduce the Xe concentration xenon inspired and / or expired and / or average and / or instantaneous from the voltage measurement V according to the following formula:

Xβ% ⁼ h Dp, O2%, N2O%, AA%, CO2%, HR, Tg ° (V) with V = f Xe%, O2%, N2θ%, AA%, CO2%, HR, Tg ° (Dp ) (2) in which the function H D _P , O 2%, N 2 O%, AA%, CO2%, HR is found to be linear and can be obtained by calibration with a flow Dp of gas at known concentration (pure xenon and / or O ₂ pure and / or pure air)

Thus, for as many suction flow values Dp as desired or necessary, a linear curve is stored in the storage means of the device, ie a line of type b + a. [Xe] = V where V is the voltage, [Xe] the xenon content and a and b are positive or negative coefficients corresponding to each given flow value Dp, a and b being obtained by calibration with a flow rate Dp of gas at known concentration (pure Xenon and / or pure O2 and / or AIR pUr) ₁

During use in operation, the calculation means then use the voltage values (V) and the flow rate value (Dp) to determine a xenon concentration (Xe%) in the gas flow from the stored linear curve. in storage means of the device corresponding to the selected flow rate value Dp.

Advantageously, the curves are, for as much value (s) of flow (Dp) as desired or necessary, are calibrated (with a flow rate established at the value (Dp) of gas whose xenon content is known, namely Xenon pure and / or 02 pure and / or pure AIR) before storage and / or refreshed periodically and automatically during the use of the device.

Figures 9c and 9d appended represent an example of such networks of curves (for as many flow values Dp as desired or necessary) showing the linearity existing between the xenon content (Xe%) and the voltage (V).

In all cases, if it is desired to obtain the xenon content (Xe%) with little accuracy, the dependencies at concentrations 02% and / or AA% and / or CO2% and / or N2O% and / or or the relative humidity of the HR gas. If, on the other hand, it is desired to obtain the xenon content (Xe%) with greater precision, these parameters will be taken into account. Nevertheless, it should be noted that these formulas (1) and (2) are not very dependent on the contents of O 2 and N 2 O and the relative humidity RH of the gas, let alone the contents of CO 2 and AA.

The invention will be better understood thanks to the following description given with reference to the appended figures, among which:

FIG. 1 represents a first embodiment of an apparatus according to the invention that can be used for xenon anesthesia with the possible use of halogens and with hot wire (s) placed in a stream derived from gas,

FIG. 2 represents a first variant of the embodiment of the apparatus of FIG. 1,

FIGS. 3 and 4 represent respectively a second and third variant of the embodiment of the apparatus of FIG. 1, usable for anesthesia under xenon only, without the use of halogens,

FIG. 5 represents a second embodiment of an apparatus according to the invention that can be used for xenon anesthesia with the possible use of halogens and with hot wire (s) placed in the main stream of gas,

FIG. 6 represents a first variant of the embodiment of the apparatus of FIG. 5, and

FIGS. 7 and 8 respectively represent a second and third variant of the embodiment of the apparatus of FIG. 5, usable for xenon anesthesia only, without the use of halogens. FIG. 1 illustrates a first embodiment of an anesthetic apparatus according to the invention including means for real-time measurement of the xenon flow in a stream derived from gas via the use of a sensor. with hot wire (s) so as to deduce the instantaneous and / or average concentrations of xenon in the main circuit, as well as means for measuring in real time the flow rate of gas insufflated to the patient and exhaled by it in the main circuit, also called "patient circuit".

The apparatus or fan of FIG. 1 comprises an input block 1 comprising connecting means to which the source of xenon and the other gas sources supplying the anesthesia apparatus are connected, such as gas bottles or a wall network, in particular for air (AIR), oxygen (O ₂ ) and / or nitrous oxide (N ₂ O) sources.

This block 1 is in fluid communication with the inlet of a mixer 2 where the mixture of xenon is mixed with the other gas or gases which are intended to form the anesthetic gas mixture, in particular oxygen in an amount sufficient to the patient (non-hypoxic)

The output of the mixer 2 feeds into a gaseous mixture, a halogenated tank 14, mounted on a tank support 13, containing a halogen compound, such as SEVOFLURANE, ISOFLURANE or DESFLURANE (the most commonly used), HALOTHANE or ENFLURANE (less used), intended to be entrained by the flow of anesthetic gas to the patient 15.

The halogen gas mixture leaving the tank 14 is introduced into a main circuit or patient circuit comprising an inspiratory branch 16 for conveying said gas mixture to the patient 15 and an expiratory branch 18 to recover all or part of the exhaled gas (loaded with CO ₂ ) by the patient 15. The inspiratory 16 and expiratory 18 branches form a loop circuit or closed circuit.

The connection between the inspiratory and expiratory limbs 18 with the patient 15 is via, for example, a Y-piece 17 and a respiratory mask, a tracheal tube or the like.

Inspiratory 7 and exhalation check valves 8 are preferably arranged respectively on said inspiratory and expiratory limbs 18. The exhalation branch 18 comprises a CO ₂ absorber device 9 comprising a tank filled with an absorbent material, such as lime, for removing the CO ₂ expired by the patient 15 and carried by the exhaled gas in the exhalation branch 18 the main circuit, and an exhaust valve 10 for evacuating any excess gas and / or any gaseous pressure in the exhalation branch 18.

Furthermore, the fan of the invention comprises, in a manner known per se, a bellows 4a for mechanical ventilation incorporated in an enclosure 4b, and a manual ventilation tank 5, which can be selectively fluidly connected to the main circuit CP for supply it with pressurized gas, via a 6 bellows / balloon selector.

In the example, the main circuit CP, indifferently called "patient circuit", consists of all the elements that have just been mentioned, namely: the elements 4a, 4b, 5 to 12 and 16 to 18.

Control means 3 comprising, for example, at least one control electronic card and one or more embedded software or computer programs make it possible to collect at least part of the information or signals coming from all or part of the sensors of the apparatus and from treat them and / or perform all the calculations necessary for monitoring the gas concentrations and / or the control of the various elements of the apparatus.

In particular, an inspiratory flow sensor 11 and an expiratory flow sensor 12, respectively arranged on the inspiratory 16 and expiratory 18 branches of the main circuit (CP), measure the inspiratory and respiratory flow rates in said branches and transmit the measurement signals as well. obtained by the control means 3 via suitable electrical connections. In this way, the control means 3 are able to control the bellows 4 and / or the opening of the exhaust valve 10 and / or the entry of the appropriate gases into the inlet block 1 to which said means of connection are connected. control 3, via dedicated electrical connections, as shown in FIG. 1.

In order to be able to measure and effectively monitor the xenon content of the gas mixture, the apparatus of the invention incorporates an S6 module. gas analysis system known as a "gas bench" including a sensor with hot wire (s) swept by a flux derived from anesthetic gas.

The gas analysis module S6 is represented a second time in an enlarged and detailed manner in FIG. 1 (see the end of the curved arrow).

More precisely, as can be seen in FIG. 1, part of the xenon gas flow conveyed by the main circuit CP of gas is taken off at the piece 17 in Y, via a sampling line S1 which communicates fluidly with said the main circuit CP.

The line S1 conveys the anesthetic gas to the module S6 by first passing through a water trap S2, where the water vapor it contains is removed before being conveyed, via a transfer line S3, until 'to module S6.

The S6 gas analysis module comprises, meanwhile, arranged on the passage of the gas flow:

a suction pump S6-A (for example of the type used on the BGA4800 or BGA4700 gas benches from ANDROS or AION by ARTEMA) to create a known anesthetic gas suction flow (Dc),

a sensor with hot wire (s) S6-E, constituted in the example of a single platinum wire, traversed by an electric current of intensity (I) given, for example an intensity of about 100 mA , with measurement of the voltage (V) across said wire when it is in contact with the flux containing the xenon,

an infra-red cell S6-B (of the type for example that fitted to the BGA4800 or BGA4700 gas banks of the company ANDROS or that fitted to the AION gas bench of the company ARTEMA) for measuring the instantaneous and / or average concentrations and / or inspired and / or exhaled of CO ₂ dioxide, N ₂ O, halogenated, ethanol or any other gas measurable by this infra-red technology,

a paramagnetic cell at O2 or a chemical battery S6-C (of the type for example of those equipping the gas banks BGA4800 or BGA4700 of the company ANDROS or AION of the company ARTEMA according to the options) for measuring the instantaneous and / or average concentrations and / or inspired and / or expired from O2, control means S6-D with software integrated on an electronic control board (of the type for example that fitted to the gas banks BGA4800 or BGA4700 of the company ANDROS or AION of the company ARTEMA),

appropriate links connecting the infra-red cell S6-B and the oxygen cell S6-C to the control means S6-D.

The output of the S6-A suction pump of the S6 module is connected to the exhalation branch of the main circuit, via a re-injection line S4, so as to return the gas that has been withdrawn through the sampling line. S1.

Moreover, as shown, the measurement signals obtained with the hot wire sensor (s) S6-E are transmitted to the control means S6-D via a suitable connection S6-F, said control means S6-F D being themselves connected, via a suitable electrical connection S5, to the control means 3.

The calculations, in particular the xenon concentrations of the anesthetic gas, are carried out by the control means S6-D of the module S6.

The gas analysis module S6 is for example a module of the BGA4800, BGA4700 or BGA4900 type from ANDROS or AION from ARTEMA, to which has been added in particular sensor means with hot wire (s) such as, for example, a HOT FIL sensor from TAEMA.

This gas analysis module S6 thus makes it possible to carry out on the gas sucked by the sampling line S1 at a continuous flow rate, preferably adjustable to some ten or hundreds of mL / min, at least:

a real-time measurement of O ₂ , AA (halogen present, the nature of which will have been automatically detected or selected by the user according to the type of gas bench used), N ₂ O, CO ₂ so as to obtain the contents or corresponding concentrations: 0 ₂ %, C0 ₂ %, AA% and N ₂ 0%,

a measurement of the fractions inspired by the patient for these same gases so as to obtain the values of corresponding inspired fractions: FiO ₂ , inCO ₂ , FiAA and FiN ₂ O, and

a measurement of the expired fractions by the patient for these gases so as to obtain the corresponding expired fraction values: FeO ₂ , etCO ₂ , FeAA and FeN ₂ O. It should be noted that the sensor with hot wire (s) S6-E, although represented at the input of the module S6 and upstream of the cell S6-C, can also be inserted elsewhere, in particular downstream of the suction pump S6-A and / or upstream of or on the re-injection line S4, the latter being connected or not to the main circuit.

The hot wire sensor (s) S6-E realizes, in real time, the measurement of the voltage (V) at the terminals of the hot wire generated by the sucked gas and transmits it via the link S6-F, with a known delay, more or less short, a few tens or even a few hundred ms depending on the set suction rate, the control software S6-D of the anesthetic gas analyzer for it to deduce, via formula (1) above, in particular:

a real-time measurement of the xenon content (Xe%) by using the suction flow adjustment value of the anesthesia gas analyzer S6 and the real-time measurement of the hot wire tension, possibly compensated by real-time concentration measurements 02%, CO2%, AA%, N2O% and / or

a measurement of the xenon-inspired fraction (FiXe) using the real-time measurement of the xenon content (Xe%) at the time of insufflation, the calculation window and FiXe determination being phased on that of calculation and determination; of the measurement inCO2, and incidentally FiO2, FiAA and FiN2O and / or

a measurement of the fraction expired in xenon (FeXe) using the real-time measurement of the xenon content (Xe%) at the time of expiration, the calculation window and determination of FeXe being phased on that of calculation and determination; of measurement and CO2, and incidentally FeO2, FeAA and FeN2O.

Alternatively, the gas analysis module S6 can be used to perform a mean xenon concentration measurement using the real time measurement (Xe%) obtained using the analyzer suction flow setting value. of anesthesia gas S6 and the mean value of the hot wire voltage measurement (V) calculated from the real-time measurement of the hot wire voltage, possibly compensated by the average concentration measurements 02%, CO2%, AA%, N20% itself calculated from real-time measurements 02%, C02%, AA%, N20%, using formula (1). In order to guarantee increased safety of use, the main circuit is doubled by an auxiliary circuit 26 connected to the line 27 for supplying the gas containing the xenon which itself feeds the main circuit.

This auxiliary circuit 26 is used in case of stop or malfunction of the main circuit.

The auxiliary circuit 26 comprises a manual insufflator 28 fluidly connected to said auxiliary circuit 26 which is manually operable by the user, that is to say the caregiver so as to send anesthetic gas to the patient 15. Downstream of the auxiliary circuit 26 is arranged a patient interface, such as a respiratory mask or a tracheal tube, supplying the upper airway of said patient with anesthetic gas, when the physician or the like activates the insufflator 28, which conventionally comprises a balloon and an inspiratory valve. and expiratory.

According to the invention, the branch line S1 can be fluidly connected to the auxiliary circuit 26 at a site 30 situated between the insufflator 28 and the patient 15, as represented by the line 29, by means of suitable connection means, for example a fitting or a filter or a mask equipped with a connection port of the sampling line, for example, a LUER type connector.

In this case, the monitoring of the xenon concentration is done in the auxiliary circuit 26 and no longer in the main circuit CP.

The auxiliary circuit 26 is advantageously arranged in the various embodiments of the invention shown in FIGS. 1 to 8.

In the embodiments of Figures 2 to 4, the elements identical to those described above for Figure 1 are designated by the same references and are not described in detail a second time.

FIG. 2 represents a first variant of the embodiment of the apparatus of the figurel, according to which the measurement signals coming from the sensor with hot wire (s) S6-E are transmitted, in this case, to the means of control 3 via a specific direct link S5-A. In particular, the calculations of xenon concentrations of the anesthetic gas are carried out in the control means, such as detailed previously. In addition, in this case, the control means S6-D are also connected, via a suitable electrical link S5-B, to the control means 3. The monitoring of the xenon concentration is thus carried out by the control means 3 of the fan and not by the S6 module.

FIG. 3 represents a second variant of the embodiment of the apparatus of the figure that can be used to carry out anesthesia under xenon only, without the use of halogens.

In this case, the measurements made by the module S6 are identical to the measurements made in the case of FIG. 1, with the exception of those relating to the halogens, which are no longer carried out because of the elimination of the halogen tank. 14 and the tank support 13. Indeed, as seen in Figure 3, the gas flow from the mixer 2 is sent directly (without loading halogen compounds, tank fault) to the main circuit.

Such an apparatus may be useful when, for example, it will be necessary to couple an inhalation anesthesia with xenon to an intravenous type anesthesia or the like since, in such a medical situation, anesthesia by halogenated products is not required because of the use of intravenous products.

FIG. 4 represents a third variant of the embodiment of the apparatus of FIG. 1. This variant can also be used to perform xenon anesthesia only, without the use of halogens, based on a combination of the embodiments of FIGS. and 3. More specifically, the apparatus of Figure 4 differs from that of Figure 2 only in that it does not include a halogen tank.

The embodiments of FIGS. 1 to 4 are particularly preferred embodiments of the invention.

FIG. 5 illustrates a second embodiment of an anesthesia apparatus according to the invention including means for measuring in real time the flow of xenon in the main flow of gas via, as previously, the use of of a sensor wire (s) hot (s) so as to deduce for example the instantaneous and / or average concentrations of xenon in the main circuit CP, and means for measuring in real time the flow of gas blown into the patient and expired by it in the main circuit. As can be seen in FIG. 5, the ventilation device comprises the same elements as those of FIG. 1, with the exception of the module S6 which has been deleted and replaced, in this case, by another module M1 gas analyzer coming from position yourself directly on the main gas circuit. In particular, the gas analyzer module M1 is plugged into patient connection means, such as a patient adapter M2, itself connected to the Y-shaped part 17 at the end of the main circuit. In this way, the analyzer module M1 can perform at least the same measurements on the gas insufflated with the patient and then exhaled by the latter, as in the case of FIG.

The module M1 that can be used for this purpose is, for example, the IRMA anesthesia or OR + anesthesia gas analyzer available (with its corresponding patient adapter M2) from the company PHASE IN and to which a wire sensor (s) has been added in particular. hot (s).

The module M1 is shown a second time in an enlarged and detailed manner in Figure 5 (see the end of the curved arrow).

More precisely, this module M1 receives control software from the control means 3 of the fan, with a known delay, more or less short, from a few tens to a few hundred milliseconds (ms), the real-time measurement of the gas flow. blown and exhaled, this flow rate being measured via the flow sensors 11 and 12 as explained above.

Moreover, the anesthetic gas coming from the Y-shaped part 17 penetrates the module M1 by passing through a hot wire sensor (s) M1-D, arranged in series, between an infrared cell M1-A and a probe intubation 18 to perform, in real time, the measurement of the voltage (V) at the terminals of the hot wire generated by the gas blown and expired, as before, and which transmits it via a connection M1-E, with a known delay more or less short, from a few tens to a few hundreds of ms, the calculation software M1-C control means of the M1 analyzer. As a variant, the hot wire sensor (s) M1-D is arranged between the Y-piece 17 and the infrared M1-A cell.

A cell M 1 -B to O ₂ of the module M1 makes it possible to measure the oxygen content. Sending the flow information by the fan control means 3 to the M1-C control means of the module M1 is via a link M3.

In addition, M1-C of the module M1 control means are themselves connected to the M1-B cell to O _2, the yarn sensor (s) hot (s) M1-D via link M1-E, and to the infra-red cell M1-A.

By applying formula (2) above, the M1-C control means can deduce the same concentrations, in particular that in xenon, and other information described in the case of Figure 1.

Of course, as previously (FIG. 1), it is also possible to perform an average xenon concentration measurement Xe% using the real-time measurement Xe% thus obtained, the latter being obtained by using the real-time measurement of the gas flow rate. blown and exhaled as well as the real-time measurement of the tension of the hot wire, possibly compensated by the average concentration measurements 02%, CO2%, AA% and N20% as explained previously.

In the embodiments of Figures 6 to 8, the elements identical to those described above for Figure 5 are designated by the same references and are not described in detail a second time.

FIG. 6 represents a first variant of the embodiment of the apparatus of FIG. 5, in which the monitoring of the average xenon concentration is carried out by the control means 3 of the fan and no longer in the module M1.

To do this, the measurement signals from the hot wire sensor (s) M1-D are transmitted via the link M3-A to the control software of the control means 3 of the fan. The fan control means 3 can thus deduce therefrom a measurement of the average xenon concentration Xe% by using the real time measurement Xe%, as previously and using formula (2) above.

The control means M1-C of the module M1 are in turn connected to the control means 3 of the fan via a dedicated line M3-B. FIGS. 7 and 8 respectively represent variants of the apparatus of FIG. 5 and FIG. 6, usable for anesthesia under xenon only, without the use of halogens, variants for which the halogen tank 14 and the support of tank 13 have been removed (as in the embodiments of Figures 3 and 4 above).

In the case of FIG. 7, the monitoring of the inspired / exhaled xenon concentrations is done in and by the module M1, as in the case of FIG. 5, whereas in the case of FIG. 8, it is operated in the fan by the control means 3, as for Figure 6.

The apparatus of the invention is usable in any circumstance and in any place, in particular in the operating theater, during the xenon anesthesia phases, so as to improve the safety of the patients and is part of the obligations of monitoring of anesthetic gases. In such a gas, the gaseous xenon is always mixed with oxygen alone, air or with oxygen and optionally one or more halogenated compounds and / or with nitrous oxide.

Of course, the hot wire sensor (s) according to the invention could use one or more son composed of any suitable electrically conductive material.

Claims

An apparatus for ventilatory anesthesia of a patient by administering a gas containing xenon gas comprising:

an open or closed circuit gas circuit (CP) having an inspiratory leg (16) for conveying a gaseous mixture containing xenon to the patient and an expiratory limb (18) for conveying the gaseous mixture containing expired xenon by the patient,

xenon gas supply means (1, 2) connected to the main circuit for supplying the inspiratory branch (16) of the main circuit (CP) with a gas containing xenon,

xenon concentration determination means (S6, M1) for determining the gaseous xenon content in at least a part of the main circuit (CP), characterized in that said xenon concentration determining means (S6; M 1) ) include:

at least one hot wire sensor (S6-E; M1-D) having at least one electrically conductive wire in direct contact with at least a portion of the gaseous flow containing the xenon, and

calculation means (3; S6-D; M1-C) cooperating with the hot wire sensor (S6-E; M1-D) so as to determine the xenon concentration (Xe%) in said gas stream,

electrical current generating means adapted to and designed to generate an electric current in at least one hot wire of said at least one hot wire sensor (S6-E, M1-D),

voltage measuring means capable of measuring at least one voltage value (V) across at least one hot wire of said at least one hot wire sensor (S6-E, M1-D) or at the terminals of at least one resistor arranged in series with at least one hot wire of said at least one hot wire sensor (S6-E, M1-D), when said at least one hot wire is in contact with the gas flow and is traversed by a electric current of intensity (I),

and in that the calculation means (3; S6-D; M1-C) cooperate with the voltage measuring means so as to determine, from the measurement of voltage (V) effected by said voltage measuring means, the xenon concentration (Xe%) in said flow.

2. Apparatus according to claim 1, characterized in that it comprises adjustable current generating means adapted to and designed to generate an electric current in the or each of the hot son of said at least one sensor hot wire (s) (s) (S6-E, M1-D), said current generating means being designed for and able to control the intensity of the electric current flowing through the hot wire (s) of said at least one hot-wire sensor (S6-E , M1-D) such that, regardless of the composition of the gas passing through said at least one hot wire sensor (S6-E, M1-D), the intensity of the current flowing through the the hot wires is kept substantially constant and / or the temperature of the hot wire (s) of the at least one sensor (s) with hot wire (s) is kept substantially constant.

3. Apparatus according to any one of claims 1 or 2, characterized in that the calculation means use at least one voltage value (V) transmitted by the voltage measuring means and at least one flow value of the anesthetic gas containing xenon, to determine the concentration of xenon (Xe%) in said gas stream.

4. Apparatus according to any one of claims 1 to 3, characterized in that said at least one sensor hot wire (s) (S6-E) is arranged on a branch line (S1, S3, S4 ) communicating fluidly with the main circuit (CP), the connection of the branch line (S1, S3, S4) to the main circuit (CP) is made on the inspiratory branch (16) and / or on the expiratory branch (18) and / or at a site located immediately adjacent to the patient's mouth, preferably at a connection site (17) between the inspiratory limb (16) and the expiratory limb (18) of said main circuit (CP), for example at a Y connection piece or a bacteriological filter arranged on the main circuit (CP).

5. Apparatus according to claim 6, characterized in that gas flow control means (S6-A) are arranged on the bypass line (S1, S3, S4) so as to obtain a gas suction flow rate. known anesthetic (Dc), preferably a constant and / or stable flow rate.

6. Apparatus according to one of claims 4 or 5, characterized in that the gas flow control means (S6-A) make it possible to control the flow rate of the gas containing the xenon so as to ensure a desired flow rate, preferably constant and / or stable, said gas carried by the branch line (S1, S3, S4) and brought into contact with at least one hot wire.

7. Apparatus according to any one of claims 4 to 6, characterized in that the gas flow control means (S6-A) comprises a gas suction pump, preferably the suction pump is associated with a control electronics of said pump that can be programmed to generate a precise and stable suction flow rate at one or more predefined and known values.

8. Apparatus according to any one of claims 1 to 3, characterized in that said at least one sensor wire (s) hot (s) (M1-D) is arranged directly on the main circuit (CP) on the branch inspiratory (16) and / or expiratory (18) and / or at the junction (17) between the inspiratory (16) and / or expiratory (18) branches.

9. Apparatus according to any one of claims 1 to 8, characterized in that it comprises means for measuring the inspiratory flow (Dpi) and / or expiratory flow (Dpe) and / or the main flow (Dp) to the junction between the inspiratory (16) and expiratory (18) branches of the gas flow circulating in the main circuit (CP), preferably the flow measurement means comprise an inspiratory flow sensor (11) and a sensor (12) of expiratory flow, respectively arranged on the inspiratory (16) and expiratory (18) branches of the main circuit, for measuring the inspiratory and respiratory flow rates in said branches and transmitting the measurement signals thus obtained to control means (3; S6-D M1-C) to determine the concentration of Xenon in the inspiratory branch (16) and / or in the expiratory limb (18) and / or at the junction (17) between the inspiratory and expiratory limbs.

10. Apparatus according to any one of claims 1 to 9, characterized in that said at least one hot wire sensor (S6-E; M1-D) comprises several son having different orientations relative to the gas stream, preferably two hot wires.

1. Apparatus according to any one of claims 1 to 10, characterized in that the calculation means are incorporated in a module (S6; M1) gas analyzer to be connected to the main circuit.

12. Apparatus according to any one of claims 1 to 10, characterized in that the calculation means are incorporated in the fan control module (3).

13. Apparatus according to claims 1 to 12, characterized in that it further comprises a gas auxiliary circuit comprising an auxiliary inspiratory branch (26) for conveying a gas containing xenon to the patient by means of a manual insufflator (28), the xenon concentration determining means being designed and adapted to connect to said gas auxiliary circuit (26) to determine the xenon content, when xenon-containing gas is administered to the patient via said auxiliary circuit (26) of gas, in particular in the event of a stop or malfunction of the main circuit (CP).

14. Apparatus according to claims 1 to 13, characterized in that the calculation means use the values of voltage (V) and flow (D) to determine a concentration of xenon (Xe%) in the gas stream from one or more linear curves stored in storage means of the device, preferably one or more lines of type a. [Xe] + b = V where: V is the voltage, [Xe] the xenon content and a and b are positive or negative coefficients corresponding to a given gas flow (D).

15. Apparatus according to any one of claims 1 to 14, characterized in that the linear curve or curves for as many flow values as desired or necessary are calibrated before storage and / or updated periodically and automatically during the use of the device.