WO2016005710A1

WO2016005710A1 - Improved method for dispensing a gaseous mixture of medical oxygen o2 and another medical gas

Info

Publication number: WO2016005710A1
Application number: PCT/FR2015/051923
Authority: WO
Inventors: Jacques-Alexis VERRECCHIA
Original assignee: Nixys
Priority date: 2014-07-10
Filing date: 2015-07-10
Publication date: 2016-01-14
Also published as: FR3023488A1; EP3177352A1

Abstract

The invention relates to a method which is carried out by means of a device for dispensing a gaseous mixture, including a gaseous mixture outlet connected to a first gas source including oxygen O₂ as well as to a second gas source including, for example, nitrous oxide N₂O, via means for mixing gases and means for monitoring the gaseous mixture. A step of initialising (61) the dispensing of the gaseous mixture is carried out by activating a first parametrisable program controlling the monitoring means such as to follow a predetermined rising curve (64) of variation over time of the concentration of N₂O in the mixture.

Description

Improved dispensing method of a gaseous mixture of medical oxygen and other medical gas

The present invention relates to the distribution of gaseous mixtures. More particularly, the invention relates to the distribution of a gas mixture for medical purposes, including sedative.

In known manner, to put a sedated patient, it is made to e.g. inhale a gas mixture of oxygen 0 ₂ medical and nitrous oxide N ₂ 0 Medical.

A medical gas is a gas for medical use constituting a health product.

Sedation by inhalation of a gas mixture of 0 ₂ and N ₂ 0 is the technique of choice for most medical or paramedical procedures that require to be performed under sedation.

Since most treatments can be performed under sedation and sedation with a gaseous mixture of 0 ₂ / N ₂ 0 has no disabling side effects, the use of the mixture of these gases is becoming more common.

The gaseous mixture sedation of 0 ₂ / N ₂ 0 is suitable for the treatment of most patients: people with disabilities, children, people with particular anxieties or people who have to undergo long and / or complex interventions.

In particular, dentistry, more and more technical, requires long sessions that are tiring without sedation. This leads more and more practitioners to turn to gaseous sedation of 0 ₂ / N ₂ 0 to increase the comfort and / or safety of their patients.

However, like any sedation method, gaseous sedation of 0 ₂ / N ₂ 0 requires precautions in order not to threaten the health of the patient:

it is desirable not to exceed a concentration of more than 70% by mass in N ₂ 0 in the mixture administered to avoid any risk of hypoxemia,

- it is desirable to terminate any sedation by an oxygenation step to rid the body of any patient inhaled N ₂ 0 to allow the patient to recover more quickly its normal state,

it is desirable to start the sedation by a gentle and controlled incrementation of the concentration of N ₂ 0 inhaled by the patient to help prevent a feeling of discomfort or discomfort encountered in 30% of patients during an administration immediately titrated around 50% in N ₂ 0.

Sedation is intended to increase the comfort of a patient during a painful intervention or to soothe a patient subject to anxiety, it can be counterproductive and even potentially dangerous, during an intervention of dentistry, to generate a stressful situation, such as a malaise, due to a sudden inhalation of a rate of N ₂ 0 too high. It is thus in the interest of everyone, practitioners as patients to avoid these stressful situations.

To this end, the invention proposes a method for dispensing a mixture of medical gases by means of a gas mixture dispensing device, comprising a gas mixture outlet connected to, on the one hand, a first source of a gas mixture first medical gas comprising medical oxygen 0 ₂ and, secondly, a second source of a second medical gas, via means for mixing medical gases, and means for controlling the gas mixture, characterized in that a step of initialization of the distribution of the medical gas mixture is carried out by activating a first parameterizable program controlling the control means so as to follow a predetermined increasing curve of evolution as a function of the time of the concentration of the second medical gas in the mixture.

Medical gases used for sedative purposes may, when inhaled too quickly in too large quantities, have troublesome side effects. Gradually varying the concentration of the second medical gas in the mixture of inhaled gas by a patient eliminates the risk of causing the patient, stress situations that may have potentially worse consequences than the absence of sedation. However, the variation of the concentration of the second medical gas in the distributed gas mixture must not impact the flow rate of the distributed gas mixture. This requires precise management of the two gas sources by activating the program controlling the control means so as to follow a predetermined increasing curve of evolution as a function of time of the concentration of the second medical gas in the mixture, a variation of the concentration of the second medical gas efficiently and securely.

Preferably, the predetermined increasing curve is a ramp of evolution as a function of time of the concentration of the second medical gas in the mixture.

Advantageously, at least one parameter of the first program selected from the duration of the initialization step and the flow rate of the mixture is defined.

Preferably, after the initialization step, a steady-state step is carried out by activating a second parameterizable program controlling the control means so as to follow a predetermined curve for maintaining the concentration of the second medical gas in the course of time. mixing to a target value.

Once the patient is sedated, the practitioner begins his intervention. Since some delicate procedures require the practitioner's full attention, it may be difficult for him to monitor, in addition, the patient's condition and the rate of the second medical gas in the gaseous mixture administered to him. The steady state stage overcome this disadvantage because this monitoring is supported by the process.

Advantageously, at least one parameter of the second program selected from the duration of the steady-state stage, the target value and the flow rate of the mixture is defined.

Preferably, during the initialization step, the predetermined increasing curve is replaced by a corrected evolution curve as a function of time of the concentration of the second medical gas in the mixture.

It may happen that the practitioner performs, during the initialization step, that the modification of certain parameters would increase the comfort of his patient. It is therefore important to be able to change these parameters if the need arises.

Advantageously, the control means of the gaseous mixture are controlled according to a physiological parameter of a patient inhaling the mixture, preferably the pulse oximetry (or oxygen saturation Sp0 ₂ ) of the patient.

The physiological parameter measured by the first sensor makes it possible to adjust the device in real time according to the specific state of each patient and no longer only according to theoretical gas mixing rules. Thus the practitioner can very quickly detect an abnormal state of his patient even when the practitioner has scrupulously respected the theoretical rules of gas mixing. The invention thus enables the practitioner to take into account the real and real needs of each of his patients.

Sp0 ₂ is easily measured in a non-invasive way. The conventional sensors performing such a measurement are generally placed around a finger and are not traumatic. This is a great advantage when one considers that sedation is used on anxious patients.

Preferably, an alarm is triggered when undesired predetermined conditions are fulfilled, and if this alarm is maintained beyond a predetermined time, the second source of second medical gas is isolated.

The attention of the practitioner may be retained by a delicate step of his intervention on the patient, he may momentarily not pay attention to the values displayed by the interface means. The alarm means can attract his attention when needed. The practitioner can then concentrate entirely on his patient, needing to focus on the device only in case of problems.

The practitioner can also be busy when triggering the alarm means, it is reassuring and reassuring for the patient and the practitioner to know that the device can take the hand and trigger an emergency action.

Preferably, following a gas mixture dispensing stop command, the second source of second medical gas is isolated so as to distribute, for a predetermined duration, only the first medical gas comprising medical oxygen 0 ₂ .

This step accelerates the evacuation of residual N ₂ 0 in the body of a patient for a faster return to an unsatured state.

Advantageously, the second source of the second medical gas (17) comprises at least one medical gas chosen from:

nitrous oxide N ₂ 0,

nitric oxide NO,

- Helium He,

- carbon dioxide C0 ₂ ,

- compressed air,

a control gas,

a tracer gas,

- Heliox,

- MEOPA.

The invention also relates to a computer program comprising program code instructions for performing the steps of a method of dispensing a mixture of medical gases according to the invention.

The invention further relates to a data recording medium comprising program code instructions for performing the steps of a method of dispensing a gas mixture according to the invention.

The invention also relates to a device for dispensing a mixture of medical gases, comprising:

a gaseous mixture outlet connected to, on the one hand, a first source of a first medical gas comprising medical oxygen 0 ₂ and, on the other hand, a second source of a second medical gas, by intermediate means for mixing medical gases, and

means for controlling the gaseous mixture,

characterized in that

it comprises means for initializing the distribution of the medical gas mixture by activating a first parameterizable program controlling the control means so as to follow a predetermined increasing curve of evolution as a function of time of the concentration of the second medical gas in the mixed.

According to other optional features of this dispensing device:

the predetermined increasing curve is a ramp of evolution as a function of time of the concentration of the second medical gas in the mixture;

the first program can be parameterized according to at least one parameter selected from the duration of the initialization step and the flow rate of the mixture;

the dispensing device comprises stationary steady-state means by activating a second parameterizable program controlling the control means so as to follow a predetermined curve for maintaining the concentration of the second medical gas in the mixture over a period of time at a value target;

the second program can be parameterized as a function of at least one parameter chosen from the duration of the stationary regime stage, the target value and the flow rate of the mixture;

the dispensing device comprises interface means allowing the replacement of the predetermined increasing curve by a corrected evolution curve as a function of time of the concentration of N ₂ 0 in the mixture. The invention will be better understood on reading the appended figures, which are provided by way of examples and are in no way limiting, in which:

FIG. 1 is a perspective view, three quarter front view, of a carriage carrying a device for dispensing a gaseous mixture according to the method of the invention,

FIG. 2 is a perspective view, three quarter rear, of the carriage of FIG. 1,

FIG. 3 is a schematic view of the device allowing the distribution of a gaseous mixture according to the process of the invention,

FIG. 4 is a front view of the interface means of the device allowing the distribution of a gaseous mixture according to the method of the invention,

FIG. 5 is a curve of evolution of Sp0 ₂ as a function of time according to the method of the invention, at the beginning of sedation.

FIGS. 6 and 7 are curves of evolution of Sp0 ₂ as a function of time according to the method of the invention, with the intervention of a user,

FIGS. 8 and 9 are curves of evolution of Sp0 ₂ as a function of time according to the method of the invention, without the intervention of a user.

Referring now to Figures 1 and 2 showing a carriage 10 carrying a device 12 for dispensing a gas mixture according to the method of the invention and Figure 3 showing the dispensing device 12 in detail.

If it is desired to carry out a sedation, the dispensing device 12 makes it possible to carry out this sedation by implementing a method for dispensing a mixture of medical gases, in particular comprising steps automatically performed by a computer program.

This dispensing method, more particularly intended to distribute a mixture 0 ₂ and N ₂ 0 gas by means of the dispensing device 12, comprises in particular:

an initialization step,

a stationary regime step, and

a step of managing the consequences of an alarm.

Various subprograms of the computer program mentioned above contribute to the achievement of these steps. In the following, the subroutine participating in carrying out the initialization step is called the first program, the routine participating in the steady state step is called the second program and the subroutine participating in alarm suite management step is called third program.

The computer program and its subroutines include program code instructions for performing steps of the process of dispensing a medical gas mixture.

As can be seen in FIG. 3, the device 12 comprises an electropneumatic circuit 13 which includes a gaseous mixture outlet 14 intended to be connected to conventional means allowing a patient who is desired to sedate to inhale the distributed gas mixture. This outlet 14 is also connected, by means of gas mixing means, on the one hand, to a first medical gas source 16 comprising medical oxygen 0 ₂ and, on the other hand, to a second source medical gas 17 comprising, in this example, nitrous oxide N ₂ 0 medical.

Conventionally, the two medical gas sources 16, 17 comprise insulatable gas bottles of the electropneumatic circuit 13 of the device 12 by closing two solenoid valves 16A, 17A.

In the example illustrated in FIG. 3, the gas mixing means comprise a first solenoid valve 18 connected to the first gas source 16 and a second solenoid valve 19 connected to the second gas source 17. The first solenoid valve 16 makes it possible to adjust the flow rate of 0 ₂ in circulation in the distribution device 12 and the second solenoid valve 19 makes it possible to regulate the flow rate of N ₂ 0 in circulation in the device 12. The O 2 and N ₂ O are mixed downstream of the solenoid valves 18, 19, in a branch M of the circuit 13 connected to the output 14.

The solenoid valves 18, 19 of the device 12 are preferably miniature solenoid valves with thermal compensation according to the European RoHS directive (2002/95 / EC). They provide the desired adjustment independently of external conditions, in accordance with the usual requirements of a medical device.

The device 12 also comprises means for controlling the gas mixture. These control means 20 may, for example, comprise a microcontroller 20M provided with a memory so as to form a recording medium of the computer program and its subroutines, that is to say a support of registering program code instructions for performing steps of the dispensing process of a medical gas mixture. To perform these steps, the microcontroller 20M is driven by the computer program and its subroutines.

The microcontroller 20M controls the solenoid valves 16A, 17A, 18, 19 as a function of at least one parameter 21 measured by a sensor 30. This parameter 21 is a physiological parameter of a patient to whom it is desired to administer the gas mixture distributed by the device. 12. As the sensor 30 is, in this example, a pulse oximeter, the physiological parameter 21 measured is the oxygen saturation Sp0 ₂ of the patient.

The oxygen saturation Sp0 ₂ can be measured simply, reliably, non-invasively and continuously. It corresponds to the oxygen saturation of the arterial blood. In fact, only the blood circulating in the arteries is subjected to heartbeat, the blood circulating in the veins being set in motion by other processes.

Pulse oximetry makes it possible to measure Sp0 ₂ by emitting two lights through the flesh of a patient, for example through his finger, namely:

- a red light (wavelength of 660 nm)

infrared light (wavelength 940 nm),

and the measurement of their differential absorption by the hemoglobin molecules in the blood.

The pulse oximeter is a sensor that usually includes a fingernail carrying two diodes emitting respectively red light and infrared light.

The transport of oxygen 0 ₂ in the blood is made predominantly by the hemoglobin molecules. The absorption of red and infrared light by these molecules varies according to whether they are in reduced form (Hb), that is to say non-oxygenated or in the form of oxyhemoglobin (Hb0 ₂ ), that is, to say oxygenated. Hb0 ₂ absorbs infrared light and lets red light through while Hb absorbs red light and lets infrared light through. The portion of unabsorbed light is collected by the pulse oximeter and analyzed. If the light collected is mainly infrared light, it is deduced that there is little Hb0 ₂ present in the blood and therefore that the patient on whom the measurement is made can potentially be in hypoxemia, which is dangerous . Conventionally, it is generally considered that a Sp0 ₂ value of a patient in a normal state must be greater than 93%. In particular for a patient under anesthesia, the measurement of Sp0 ₂ allows the early detection of hypoxaemia, well before the appearance of a cyanosis that can be very late onset in anemic patient or difficult observation in a patient very pigmented.

Furthermore, the microcontroller 20M controls the gas mixture by controlling the solenoid valves 16A, 17A, 18, 19 as a function of other parameters 22, 23, 24, 25, 26 measured by different sensors 32, 33, 34, 35, 36:

a first static pressure sensor 32 connected to the first gas source 16 which measures the static pressure of O ₂ 22 in the part of the pneumatic circuit 13 which carries the O ₂ ,

a second static pressure sensor 33 connected to the second gas source 17 which measures the static pressure of N ₂ 0 23 in the part of the pneumatic circuit 13 which carries the N ₂ 0,

- a first flow meter 34 connected to the first gas source 16 that measures the flow rate of 0 ₂ 24 of the pneumatic circuit 16,

a second flowmeter 35 connected to the second gas source 17 which measures the flow rate of N ₂ 0 25 of the pneumatic circuit 16, and

a third flowmeter 36 connected to the two gas sources 16, 17 which measures the flow rate of the gaseous mixture 26 which passes into the pneumatic circuit 16. The various sensors 32 to 36 and valves 16A, 17A, 18, 19 of the pneumatic circuit 13 are components with analog outputs that are usually less energy-consuming and more robust than digital output electrical components. The flow meters 34 to 36 and the static pressure sensors 32, 33 are preferably thermally compensated.

FIG. 3 also shows a conventional interface between the pulse oximeter 30 and the microcontroller 20M.

The static pressure sensors 32, 33 make it possible to detect very quickly any unexpected pressure drop in the pneumatic circuit 13.

The transport of the gases from the sources 16, 17 to the outlet 14 is through a set of flexible pipes 38 of thermoplastic polyurethane elastomer suitable for transporting medical gases.

The carriage 10 is made mobile by wheels and also carries electrical supply means 40 of the device 12 and interface means 42 between a user of the device 12 and the control means 20 of the gas mixture.

Preferably, conventional means of current cutting are integrated with the power supply means 40 to allow adaptability to different power grids of different countries. The power supply means 40, visible in FIG. 2, comprise a power supply provided by a switched-mode power supply which allows adaptability to different electrical networks of different countries.

To ensure perfect patient safety, safety loops implemented by conventional electronic means ensure, each time the device 12 is turned on, that the battery is sufficiently charged to allow the device 12 to operate for at least 20 minutes.

The interface means 42 allow:

the reading by the user of at least one value of the parameter 21 to 26 measured by each sensor 30 to 36, and

the recording in the control means of a set point for the gas mixture.

The interface means 42 comprise for example:

two segment displays 44A, 44B,

an LCD 46, and

- buttons

to read, control and control the various parameters 21 to 26.

The segment displays 44A, 44B provide the user with a very good visibility of certain selected parameters of the device 12, for example the percentage of N ₂ 0 in the gas mixture and the flow rate of the gaseous mixture 26.

The screen 46 displays the values of these selected parameters, as well as the values of the parameter 21 measured by the pulse oximeter connected to the patient. The screen 46 also displays device status parameters 12, battery reserves, time elapsed since the start of the device 12, etc.

Preferably, the device 12 can not be started until the 20M microcontroller does not receive a value SP0 _{February 21} desired. The proper connection of the pulse oximeter 30 to the electropneumatic circuit 13 is thus made mandatory in order to start the sedation.

The device 12 also comprises alarm means 50, of which the microcontroller 20M is part, activated at least when the first parameter 21 reaches an undesired value, for example not respecting a particular standard.

If disconnection of the pulse oximeter 30 occurs during sedation, sudden lack of value SP0 _{February 21} immediately activates the alarm means 50 and an alert message warns the user.

Preferably, the activation (see arrow 51 in FIGS. 6 to 9) of the alarm means 50 is also done if the pulse oximeter 30 is connected to the circuit 13 but the SP0 ₂ values 21 received can not be used (e.g. due to a wrong position of the pulse oximeter 30 on the patient's finger).

In other cases, the interface means 42 also display messages to explain the reasons for the activation of the alarm means 50 to the user of the device 12. The screen 46 also allows, apart from any application of a sedation by the device 12, access to a menu that can allow:

to modify sedation parameters 22 to 26,

- Reset device 12,

- To give access to the operating information of the device 12 and the activation of a 50% clamping at N20 concentration.

The alarm means 50 are controlled by safety loops implemented by conventional electronic means which ensure the feedback control of the sedation parameters 22 to 26.

If the microcontroller 20M does not detect a response from a user in response to the activation of the alarm means 50, the device 12 then goes into automatic operation mode. Indeed, the microcontroller 20M forms automatic control means 52 mixing means 18, 19 activatable under predetermined conditions not desired such as for example the maintenance of the activation of the alarm means 50 beyond a predetermined time . These automatic control means 52 can take control of the mixing means 18, 19 following a non-deactivation of the alarm means 50, according to an automatic mode corresponding to the execution of the third program relating to the alarm management. .

These automatic control means 52 are also preferably triggered in the case where the microcontroller 20M does not receive the values of the Sp0 ₂ rate 21 due to a bad connection of the pulse oximeter 30: if at the end of one minute the pulse oximeter 30 is still not detected (or if the information is still not usable), then the device 12 goes into the automatic mode that provides the trigger (see reference 53 in Figures 7 and 9) an "O2 flush" mode which consists in isolating the source of N ₂ 0 17 and distributing only pure 0 ₂ .

The activation of the alarm means 50 may also be due to a sudden drop in pressure in the pneumatic circuit 16 or in one of the gas sources 16, 17 detected by one of the static pressure sensors 32, 33.

A user of the device may also decide not to wait for a state of emergency so that the automatic control means 52 take control of the management of the distributed gas mixture and decide to start the device 12 directly in automatic mode.

The automatic piloting means 52 thus allow the implementation of the step of managing the alarm sequences of the distribution process, in particular by executing the third program provided for this purpose.

The following will be described below, especially with reference to FIGS. 5 to 9, other steps of the method of dispensing a mixture of medical gases, namely:

the initialization step 61, and

the stationary regime step 62.

The initialization step 61 of the distribution of the gaseous mixture is carried out by activating the first program which is parameterizable. As shown in FIG. 5, this program automatically controls the control means 20 so as to follow a predetermined increasing curve 64 of evolution as a function of time of the concentration of N ₂ 0 in the distributed mixture.

In the example illustrated in FIG. 5, the predetermined increasing curve 64 is a so-called sedation ramp. This sedation ramp 64 is intended to increment the N ₂ 0 concentration little by little in order to provide gentle sedation to the patient.

The sedation ramp 64 is configurable via three setpoint variables that the user can modify through a menu accessible only when the device 12 is not dispensing the gas mixture. This menu, accessible through the screen 46 of the interface means 42, allows a user to parameterize:

- the ramp time 64 tdbie 66,

- the targeted concentration [N ₂ 0] _C ibie 68,

- the flow of mixture pdbie.

The time of ramp 64 tdbie 66 is the time at the end of which the concentration [N ₂ 0] dbie 68 must be reached in the distributed mixture. This is the time that the initialization step 61 lasts. The mixing rate (Pdbie is defined according to the patient's lung capacity and must remain constant throughout the sedation process.

The user thus defines at least one parameter 66, 68 of this first program selected from the duration 66 of the initialization step 61 and the flow rate (Pdbie of the mixture.

During this initialization step 61 of the dispensing process, the gaseous mixture is administered by the device 12 as indicated below.

At t = 0, the user triggers the start of the sedation, by pressing a start / stop button of the interface means 42. The gas mixture is then administered at the flow rate (Pdb and consists of 100% of 0 ₂ and 0% of N ₂ 0.

At t = t (with t <tdbie), the control means 20 progressively increase the concentration of N ₂ 0 in the mixture dispensed, to go from 0% (at t = 0) to the value [N ₂ 0] dbie 68 at the end of time tdbie 66.

It will therefore be noted that the start / stop button of the interface means 42 as well as the microcontroller 20M and the first program stored in its memory forming initialisation means for the distribution of medical gas mixture controlling the control means 20 so as to follow the ramp 64 changes as a function of the concentration time N ₂ 0 in the mixture.

At t = 66, the device 12 goes to the steady state stage 62 of the method and the ramp 64 is transformed into a predetermined curve in the form of a bearing 70, during which the gaseous mixture is administered at the flow rate Φ and to concentration

The steady state step 62 is performed by automatic activation of the second program, which is parameterizable. This second program automatically controls the control means 20 of the device 12 so as to follow the predetermined curve 70 which maintains over time the concentration of N ₂ 0 in the mixture at a target value 68.

The user can define at least one parameter of the second program selected from the duration of the steady-state step, the target value 68 and the flow rate of the mixture _C ibie.

It will therefore be noted that the microcontroller 20M and the second program stored in its memory form stationary steady-state means 62, when the second program is activated, driving the control means 20 so as to follow the predetermined curve 70 of maintaining during the time of the N ₂ 0 concentration in the mixture at the target value 68.

Even if the device 12 is in autopilot, the user always retains control over the composition of the gas mixture. In particular during the initialization step 61, the user can, at any moment, influence the evolution of the sedation ramp 64 without forcing the device 12 out of operation in automatic piloting.

An action of the user on the buttons 71, 72, 73, 74 of the interface means 42 (FIG. 3) makes it possible to modify the sedation ramp 64 and if the parameters of the sedation ramp 64 are modified by a user. they are according to the following rules:

- If at a given instant 76, the user presses the button 71 designated for example by "[N ₂ 0] +", the device 12 responds by immediately inducing a jump 78 of + 5% of the concentration of N ₂ 0 distributed gas mixture. A new sedation ramp 79 is obtained.

- If at a given instant 80, the user presses the button 72 designated for example by "[N ₂ 0] -", the device 12 responds by immediately inducing a jump 82 of

-5% of the N ₂ 0 concentration of the distributed gas mixture. A new sedation ramp 83 is obtained. In both cases, the microcontroller 20M continues to evolve the sedation ramp 64 taking into account both the unchanged parameters and the modified parameter.

Thus, during the initialization step 61, the predetermined increasing curve 64 can be replaced at any time by a corrected curve 79, 83 of evolution as a function of time of the concentration of N ₂ 0 in the distributed mixture.

If at the moment when the user presses the button 71 "[N20] +" the value in N ₂ 0 requested 84 is greater than [N ₂ 0] _C ibie 68, the device 12 passes immediately from the step of initialization 61 in the steady state step 62, replacing the ramp 64 by a step 84 where the value of [N ₂ 0] _C ibie 68 is replaced by the new value of [N ₂ 0] 84.

Pressing the buttons 73 designated for example by "Φ +" or 74 designated for example by "Φ-" immediately modifies the output flow of the mixture 26, maintaining the concentration parameters 66, 68 of the ramp 64 unchanged.

A user can not change the tdbie parameter 66. The only solution to change this parameter 66 is to release the device 12 from the autopilot mode to enter manual mode. The setting of tdbie 66 can only be done via the menu, accessible only by the interface means 42 outside of any gas distribution by the device 12.

The transition from automatic mode to manual mode is done by simply pressing a dedicated button interface means 42.

If switching from automatic mode to manual mode is done during the initialization step 61, then the ramp 64 is immediately interrupted and the device 12 distributes a mixture of gases with a concentration of N ₂ 0 stabilized around the value of [N ₂ 0] 86 which defined the gaseous mixture dispensed at the time of exit from the automatic mode.

Throughout the entire dispensing process, the means for controlling the gas mixture are controlled according to a physiological parameter of a patient inhaling the mixture. The physiological parameter 21 measured is preferably the pulse oximetry (or oxygen saturation Sp0 ₂ ) of the patient.

Several cases are illustrated in Figures 6 to 9.

In Figure 6, the evolution is observed, depending on the time of the SP0 ₂ 21 of a patient inhaling a gas mixture delivered by the device 12.

The variable Sp0 ₂ 21 is tracked over time and its evolution is stored in the memory of the microcontroller 20M. There is no absolute value to be respected. That is, a patient can have a Sp0 ₂ level of 90% while still perfectly fine, while the same value for another patient may mean a condition critical physiological. The values of Sp0 ₂ generally considered "normal" are between 94 and 99%.

The dispensing method triggers an alarm 51 when undesired predetermined conditions are realized and, if this alarm 51 is maintained beyond a predetermined duration 92, isolating the second gas source 17 comprising N ₂ 0.

Conventionally, there (SP0 ₂₎ o 90 the value of the SP0 _{February 21} in the patient at the start of sedation that is to say at t = 0. This value 90 is taken as reference for the patient in question: if the rate of SP0 ₂ 21st falls below 0.9x (SpO ₂₎ ₀ during the predetermined time period 92, then the alarm means 50 is triggered.

In this embodiment, the predetermined duration 92 is set to 1 minute. However, as an absolute threshold is fixed: as the SP0 _{February 21} is less than 80% sedation can not start because the device 12 considers the patient as poorly oxygenated which could pose a risk to it.

Similarly, if during the sedation, the Sp0 ₂ 21 falls below the threshold value of

80%, an alarm 51 is immediately triggered, accompanied by a message on the screen 46.

At each instant t, the program stored in the memory of the microcontroller 20M compares the value of the ratio of Sp0 ₂ 21 to (SpO ₂ ) ₀ :

if (SpO ₂ ) (t)> (SpO ₂ ) ₀ , the device 12 continues to apply the method normally;

if (SpO ₂ ) (t) <(SpO ₂ ) ₀ for less than one minute, sedation is considered to proceed normally and has no major impact on the physiological state of the patient and the device 12 continue to apply the process normally;

if (SpO ₂ ) (t) <(SpO ₂ ) ₀ for all t for more than one minute, the situation is considered abnormal and an alarm 51 is activated to warn the user.

If, within a period of ten seconds after the activation 51 of the alarm means 50, the user presses the button 91 designated for example by "OK" (FIG. 4) to signify his / her understanding of the information then a new delay 96 of 20 seconds is put in place. During this period, if the user changes the parameters 22 to 26 to reduce the N ₂ 0 concentration of the dispensed mixture and there is a correction 97 of the Sp0 ₂ 21 rate, i.e. Sp0 ₂ 21 returns above 90% (SpO ₂ ) ₀ , so device 12 continues to apply the second stage 62 of the process normally.

If, as shown in FIG. 7, the correction 97 of the Sp0 ₂ 21 rate is not done following the intervention 95 of the user, then there is triggering 53 of the "0 ₂ flush" mode, and the sedation only resumes when the Sp0 ₂ 21 is ironed above the threshold 0.9x (SpO ₂ ) ₀ . If, as shown in FIG. 8, there is no intervention 95 of the user after the trigger 51 of the alarm means 50, a delay 98 of one minute is set up. If during this time the correction 97 of the Sp0 ₂ 21 takes place, the anomaly is considered resolved, and the device 12 continues to dispense the gas mixture. However, a permanent message remains on the screen 46 to indicate the past anomaly.

If, as shown in FIG. 9, the correction 97 of the Sp0 ₂ 21 rate is not done during the minute 98 following the alarm 50, then there is triggering 53 of the "O2 flush" mode.

The trigger 53 of the "0 ₂ flush" mode can also be done, at any time, manually by the user via the interface means 42. A pressure on the button 100 designated for example by "0 ₂ flush" isolates indeed immediately the second gas source 17. The flow deficit 25 of N ₂ 0 in the flow 26 of the gas mixture is compensated by the increase of the flow 24 of 0 ₂ to reach the previously specified set point

by the user via the interface means 42. This operation aims to rid the patient's body of inhaled N ₂ 0 during sedation.

The trigger 53 of the "0 ₂ flush" mode can be used by the user at the end of sedation to ensure a smooth sedation exit to the patient and allow him to recover faster from sedation.

Thus, at the end of the sedation, the user presses the start / stop button to end the gas distribution. This action on the start / stop button is a gas mixture dispense stop command that automatically triggers the "0 ₂ flush" mode. This mode "0 ₂ flush" consists, as already described above, in isolating the source of N ₂ 0 (0% of N ₂ 0 distributed) to distribute only pure Γ0 ₂ (100% of 0 ₂ distributed), this for a predetermined time, for example one minute. This final step makes it possible to accelerate the evacuation of the residual N ₂ 0 in the patient's body for a faster return to an unsatured state. At the end of this final stage, the gas distribution is completely interrupted.

It goes without saying that the invention is not limited to the example described above and other embodiments of the invention will become apparent to those skilled in the art.

It is in particular possible to replace the N ₂ O with another medical gas comprising, for example, at least one gas among nitrogen monoxide NO, helium He, carbon dioxide C0 ₂ , compressed air, a control gas, a tracer gas, Heliox or MEOPA.

It is also possible to use the device 12 in an application that would not be dentistry. Indeed, the sedation of a restless or anxious patient can also be to be very useful in pediatrics, psychiatry or geriatrics, for example. The use of the device 12 can also be conceived as a way to encourage ambulatory care, to increase the threshold of tolerance to pain and to simply perform non-invasive but painful or anxiety-provoking acts.

One could also consider that the device 12 can operate in complete autonomy, without involving the intervention of a practitioner. Indeed, instead of triggering the alarm means 50, the device 12 could, via conventional control means, automatically make the correction that is required.

Claims

A method of dispensing a mixture of medical gases by means of a gas mixture dispensing device, comprising:

a gaseous mixture outlet (14) connected to, on the one hand, a first source of a first medical gas (16) comprising medical O ₂ oxygen and, on the other hand, a second source of a second medical gas (17), by means of mixing means (18, 19) of the medical gases, and

control means (20) for the gaseous mixture,

characterized in that

performing a step of initializing (61) the distribution of the medical gas mixture by activating a first parameterizable program controlling the control means (20) so as to follow a predetermined increasing curve (64) of evolution as a function of time the concentration of the second medical gas in the mixture.

Dispensing method according to the preceding claim, wherein the predetermined increasing curve (64) is an evolution ramp as a function of time of the concentration of the second medical gas in the mixture.

A method of dispensing according to claim 1 or 2, wherein at least one parameter (66, 68) of the first program selected from the duration of the initialization step (66) and the flow rate of the mixture is defined.

Dispensing method according to any one of the preceding claims, in which, after the initialization step (61), a steady-state step (62) is carried out by activating a second parameterizable program controlling the control means (20). in order to follow a predetermined curve (70) for maintaining the concentration of the second medical gas in the mixture over time at a target value (68).

Dispensing method according to Claim 4, in which at least one parameter (68) of the second program selected from the duration of the steady-state stage is defined, the target value (68) and the flow rate of the mixture.

A method of distribution as claimed in any one of the preceding claims, wherein, during the initialization step (61), the predetermined increasing curve (64) is replaced by a corrected curve (79, 83) of evolution. time function of the concentration of N ₂ 0 in the mixture.

Dispensing method according to the preceding claim, wherein the control means (20) of the gaseous mixture is controlled according to a physiological parameter (21) of a patient inhaling the mixture, preferably pulse oximetry (or oxygen saturation Sp0 ₂ ) of the patient.

8. A method of distribution according to any one of the preceding claims, wherein an alarm (51) is triggered when undesired predetermined conditions are realized, and, if this alarm (51) is maintained beyond a predetermined time (92), the second source is isolated

(17) second medical gas.

Dispensing method according to any one of the preceding claims, wherein, following a gas mixture dispensing stop command, the second source (17) of second medical gas is isolated, so as to dispense with during a predetermined period of time, that the first medical gas comprises medical oxygen 0 ₂ .

10. The dispensing method as claimed in any one of the preceding claims, wherein the second source of the second medical gas (17) comprises at least one medical gas chosen from:

nitrous oxide N ₂ 0,

nitric oxide NO,

- Helium He,

- carbon dioxide C0 ₂ ,

- compressed air,

a control gas,

a tracer gas,

- Heliox,

- MEOPA.

1 1. A computer program comprising program code instructions for performing the steps of a method of dispensing a medical gas mixture according to any one of claims 1 to 10.

A data recording medium comprising program code instructions for performing the steps of a method of dispensing a medical gas mixture according to any one of claims 1 to 10. 13. Dispensing device a mixture of medical gases, comprising:

control means (20) for the gaseous mixture,

characterized in that

it comprises means (20M) for initializing the distribution of the mixture of medical gases by activating a first parameterizable program controlling the control means (20) so as to follow a predetermined increasing curve (64) of evolution as a function of time of the concentration of the second medical gas in the mixture.

14. Dispensing device according to the preceding claim, wherein the predetermined increasing curve (64) is an evolution ramp as a function of time of the concentration of the second medical gas in the mixture.

15. Dispensing device according to claim 13 or 14, wherein the first program is parameterizable according to at least one parameter (66, 68) selected from the duration of the initialization step (66) and the flow rate of the mixed.

16. Dispensing device according to any one of claims 13 to 15, comprising means (20M) steady state (62) by activating a second parameterizable program controlling the control means (20) so as to follow a curve predetermined time (70) of maintaining the concentration of the second medical gas in the mixture at a target value over time

(68).

17. Dispensing device according to claim 16, wherein the second program is parameterizable as a function of at least one parameter (68) chosen from the duration of the steady-state stage, the target value (68) and the flow rate of the mixed.

18. Dispensing device according to any one of claims 13 to 17, comprising interface means (42) for replacing the predetermined increasing curve (64) by a corrected curve (79, 83) of evolution based the time of the concentration of N ₂ 0 in the mixture.