FR2985190A1 - Gas heating device for use in ventilation installation unit for artificial respiration of patient, has main gas pipe and heater in mechanical contact with part of wall so that heat emitted by heater crosses part of wall before heating pipe - Google Patents

Abstract

The device has a main gas pipe (10) crossed by an internal passage (10'), where the pipe is made of plastic and metallic material. A heating compartment (40) includes an external casing (70) with a peripheral wall (72) that delimits an internal volume (60). A heater (50) is arranged in the internal volume. The main gas pipe and the heater are arranged on both sides of a part (71) of the peripheral wall, and arranged in mechanical contact with the part of the peripheral wall such that heat emitted by the heater crosses the part of the wall before heating the main gas pipe. An independent claim is also included for a ventilation installation unit.

Description

The present invention relates to a gas heating device intended for an artificial respiration installation, that is to say intended to be connected to a respirator, so as to prevent or limit the condensation of moisture within said respirator . In other words, the invention relates to a respiratory anti-condensation device.

In an artificial respiration installation, different sources of humidity are present: - the moisture naturally present in the gas, in particular when the gas delivered is composed in whole or in part, of air taken from the room, - the expired moisture generated by the patient; and humidification devices, sometimes added to moisten the inspired gases. The water transported in the form of water vapor is likely to condense if the gas cools, whether during the flow in the patient circuit or in the exhalation assembly of the respirator, namely the elements that are located downstream of the patient in the direction of the gas flow. Such condensation is likely to degrade the performance of the respirator, or even to damage the constituent elements, including its sensors. In addition, there are hygiene concerns, since the condensed water flows into or out of the respirator since the water is able to carry germs or the like. A known solution is to equip the patient circuits and / or expiratory sets of water traps respirators, which recover the condensed water. Such a water trap is described in GB-A-1456570. However, such water traps have the major disadvantage of having to be emptied regularly and only recover water after condensation, that is to say when it is already in liquid form. However, some flow sensors called "hot wire", consisting of a very fine platinum wire, are likely to be damaged by the smallest droplet. It has therefore been necessary to develop alternative solutions.

Thus, another solution is to prevent condensation by heating the gas itself or the walls of the elements it passes through. Some respirators offer an integrated solution in which the expiratory assembly is equipped with a heating system, ensuring the absence of condensation. Similarly, some humidifiers, such as that described in DE-A-202005008152, are provided with a heating element which, fixed in the expiratory branch of the patient circuit, is used to heat the gas and the elements of the expiratory assembly. , thus avoiding any condensation. However, such a heating element has the disadvantage of being dedicated to a given device, respirator or humidifier, and therefore to bring significant constraints on the design thereof.

It is therefore understandable that no truly ideal solution exists to date. In addition, it is also necessary to sterilize or replace, between two successive patients, the elements in contact with the exhaled gas to avoid the risk of cross-contamination. Known solutions require tedious disassembly of the most fragile elements for autoclaving or expensive replacement of certain elements. This generates significant costs, a waste of time and generates waste that is not or difficult to recycle. The problem that arises is therefore to propose a device which, when associated with a respirator, avoids the condensation of the humidity of the gas in liquid form in the expiratory assembly of the latter, which device can be matched to any respirator without altering the performances of the latter. In addition, the device must be easily dismounted between two uses, to allow simple and effective sterilization of the parts in contact with the exhaled gas and without generating significant waste.

The solution of the invention is a gas heating device comprising a main conduit of gas through which an internal passage passes; and a heating compartment comprising an outer casing comprising a peripheral wall defining an internal volume; a heating element arranged in the internal volume; and a locking mechanism for detachably receiving the main gas duct, and wherein the device, the main gas duct and the heating element are arranged on either side of a portion of the peripheral wall of the outer casing, and are in mechanical contact with said peripheral wall portion so that heat from the heating element passes through said peripheral wall portion prior to heating the main gas duct. Depending on the case, the device of the invention may comprise one or more of the following technical characteristics: the peripheral wall portion of the outer casing is sandwiched between the main gas duct and the heating element; . the heating element comprises electrical connections; the outer envelope comprises an internal volume filled with gas, in particular air, or with a thermally insulating material. alternatively, the outer envelope comprises an internal volume evacuated, that is to say in depression (<1 atm), so as to constitute a thermal insulator. - The heating element comprises a heating resistive cartridge - the heating element comprises a resistive electrical track deposited on a flexible electrically insulating support. the main duct is formed of at least one metallic or plastic material. the main duct has a length of between 2 and 15 cm. - The wall of the main duct has a thickness of between 1 and 5 mm The invention further relates to a ventilation system comprising a respirator comprising a patient circuit loop with an inspiratory branch and an expiratory branch, and a device according to the invention. , that is to say as described above, arranged on the expiratory branch. The invention will now be better understood thanks to the following description given with reference to the appended figures in which: FIG. 1 shows a conventional artificial ventilation installation in which the device of the present invention is inserted; FIG. sectional view of an embodiment of the central duct, - Figure 2b shows a sectional view of an embodiment of the central duct and the main body, - Figures 3a and 3b (sectional view) are diagrams of an embodiment of the heating element, and - Figure 4 is a diagram of the electrical connections of an embodiment of the invention incorporating a temperature control. Figure 1 shows a conventional artificial ventilation system of a patient 140, in which is inserted a heating device according to an embodiment according to the present invention 200. The device 200 for heating expired gases can heat the expired gases by the patient 140 so as to prevent the condensation of gases, that is to say water vapor, in the expiratory assembly 105 of the ventilator 100. The device of the invention is external to the respirator and is inserted in series between the expiratory branch of the patient circuit and the exhalation assembly of the ventilator. As detailed below, the exhaled gas heating device 200 of the invention comprises an internal duct through which the exhaled gas passes, which internal duct is heated by a heating system, and may also be equipped with a heating card. control-command to ensure an effective and safe heating in all circumstances.

More specifically, the exhaled gas heating device 200 is incorporated in the patient circuit 150 which forms a loop circuit between the ventilator 100 and the patient 140, immediately upstream of the expiratory assembly 105 of the ventilator 100, that is to say ie at the downstream end of the expiratory limb 130 of the patient circuit 150. The ventilator 100 is therefore connected to the patient 140, via an inspiratory branch 120 of the patient circuit 150, so as to supply it with inspiratory gas, and the patient 140 is connected to the ventilator 100 by the expiratory limb 130 of the patient circuit 150, so as to return the exhaled gas from the patient 140, rich in CO2, to the ventilator 100, as shown in FIG. 1. That the expired gas has been wetted by the upper airway of the patient 140 and / or a humidifier 110 placed on the inspiratory branch 120 of the circuit 150, the exhaled gas is usually saturated with moisture, i.e. has a relative humidity of 100% by volume, and is at the temperature of the human body, generally about 37 ° C. The gas is then conducted by the expiratory limb 130 of the patient circuit 150, which is in a room whose ambient temperature is typically between 10 and 35 ° C.

It follows that the moist gas cools during its course in the circuit 150, in particular in the exhalation branch 130, especially since its flow rate, usually between 1 and 200 l / min, is low. However, a physical property of gas and gas mixtures, such as a mixture of nitrogen, oxygen and carbon dioxide exhaled by a patient 140, is to be able to transport a growing amount of moisture depending on its temperature. Also, during the cooling of the gas during its journey in the patient circuit 150, all the moisture present in the gas in the form of water vapor can no longer be transported and it condenses in liquid form, essentially on the walls of the ducts. and elements that transport it, especially in the components of the expiratory assembly 105 of the respirator 100. To remedy this problem of condensation, the device 200 according to the present invention is used to heat the gas before it flows into the expiratory assembly 105 of the respirator 100, thus avoiding condensation phenomena in this assembly. As illustrated in FIGS. 2a and 2b, the exhaled gas heater 200 according to the invention comprises a main gas duct 10 through which an internal passage 10 'extends between a gas inlet 20 and a gas outlet At both ends thereof, and a heating compartment 40 comprising an outer shell 70 comprising a peripheral wall 71, 72 defining an internal volume 60. A heating element 50 is arranged in the internal volume 60 of the heating compartment 40. Moreover, a locking mechanism serving as a connection means is arranged on or in the outer wall of the outer casing 70 and allows detachable, that is to say removable, receiving the main conduit 10 of gas, so as to be able to secure it or, conversely, to separate it from the heating compartment 40, as explained hereinafter. In addition, the main conduit 10 of gas and the heating element 50 are arranged on either side of a portion or portion 71 of the peripheral wall 71, 72 of the outer casing 70 while being kept in mechanical contact. with said peripheral wall portion 71 so that the heat emitted by the heating element 50 passes through said wall portion 71 before reaching and heating the gas main conduit 10. In other words, a peripheral wall portion 71, 72 of the outer shell 70 is "sandwiched" between the main gas pipe 10 and the heating element 50 so that the heat produced by the element heating 50 diffuses first through the wall 71 of the casing 70, then through the wall 11 of the main duct 10 so as to warm the gas flowing in the internal passage 10 'of the main conduit 10 of gas. In operation, the exhaled gas heating device 200 is inserted on the exhalation branch 130, upstream of the ventilator 100, as illustrated in FIG.

More specifically, the central duct 10 is a hollow element, for example of tubular shape or the like, for conveying gas from the end of the expiratory branch 130 of the patient circuit 150 to the inlet of the expiratory assembly 105 of the Respirator 100. In order to guarantee the compatibility of the central duct 10 with most of the patient circuits 150 and the existing respirators 100, a preferred geometry of the central duct 10 is that of a cylinder having at its ends 20, 30, connection cones. or the like, male and / or female, for example 22 mm, 15 mm or 10 mm in diameter. Such an embodiment has the advantage of not opposing additional resistance, with respect to the patient circuit 150, to the flow of gas in said circuit 150. In fact, the central duct 10 is used to perform a heat exchange between the gas flowing therefrom and the heating element 50 of the main body 40 through the outer wall portion 71. Advantageously, the duct 10 is formed of an effective thermal conduction material, for example a metallic material. Its length is a few centimeters, typically between 2 and 10 cm, preferably about 5 cm.

Alternatively, the conduit 10 is made of a plastic material, in particular for aesthetic reasons. In order to achieve a sufficient heat exchange, the conduit 10 then typically measures between 3 and 15 cm, preferably about 10 cm. In order to meet the need for sterilization, the material may advantageously be selected to withstand sterilization processes by autoclaving.

Whatever the material used, the walls of the duct 10 are of small thickness, typically between 1 and 5 mm, preferably of the order of 2 mm, in order to ensure efficient heat exchange. The central duct 10 is made removable to undergo the sterilization process.

A locking mechanism allows, in use, to make it integral with the main body 40. The locking mechanism may be for example a nut which, screwed on the body of the heating compartment 40, ensures the maintenance of the conduit 10 in the body of the heating compartment 40. Any other locking mechanism is, however, conceivable provided that it makes it possible to secure or separate, as desired by the user, the duct 10 to the heating compartment 40 in the manner described hereinabove. above. Preferably, it also comprises a locking mechanism for blocking the central duct 10 in position to prevent any rotation thereof relative to the heating compartment 40. This locking in rotation can be provided by another mechanical element of the invention or by the locking mechanism which then provides the two functions of fixing and locking in position. Furthermore, the heating compartment 40 comprises an outer envelope 70, that is to say a kind of protective shell, prohibiting the user and the patient access to all the interior elements, including when the conduit 10 is removed from the heating compartment 40 to be sterilized. In fact, the envelope of the heating compartment 40 is completely closed or closed, with the exception of openings arranged voluntarily to allow the insertion of the conduit 10 in the body of the heating compartment 40 and the connection of the conduit 10 to the expiratory assembly 105 of the ventilator 100 and at the end of the expiratory limb 130 of the patient circuit 150, and with the exception of an opening arranged voluntarily to allow the introduction of an electrical connector to ensure the supply of the heating element 50. In order to guarantee an efficient heating of the gas, via the duct 10, a portion 71 of the casing 70 of the heating compartment 40 preferably has the geometry of a conduit which marries the outer surface of the duct 10. It should be noted the importance of the mechanical adjustment between the portion 71 of the casing 70 and the duct 10. Typically, a mechanical clearance of less than 1 mm is desirable. ble, preferably less than 0.2 mm. Preferably, the same material is used for the realization of the duct 10 and the casing of the main body 70, to ensure the mechanical adjustment including when the various elements are raised in temperature. Whatever the material chosen, the envelope is of small thickness, typically between 1 and 5 mm, preferably about 2 mm, to ensure efficient heat exchange. In the particular case where the central duct is a cylinder, the envelope then has a portion 71 of cylindrical or semi-cylindrical surface whose inner diameter coincides with the outside diameter of the duct 10. It should be noted that only the surface portion 71 of the envelope 70 in contact with the conduit 10, hereinafter referred to as "heating surface of the envelope", must be adjusted to the shape and dimensions of the conduit 10, the rest of the envelope, hereinafter referred to as " cold surface of the envelope "72, which can have the geometry and any dimensions. The cold surface 72 of the envelope 70 protects the user against high contact temperatures, in order to avoid any risk of burns. Moreover, the performance of the heater is related to the thermal insulation of the casing 70 between the heating element 50 and the ambient air of the room. The better the thermal insulation, the more efficient is the heating. To this end, a thermally insulating material may be disposed inside the casing 70 of the heating compartment body 40, opposite the cold surface 72 of the casing 70. According to another embodiment, the casing within the heating compartment 40, a space 60 filled with air facing the cold surface 72 of the envelope 70, typically a space 60 filled with air having a size ranging from a few mm to a few cm, for example of the order of 1 cm. The space 60 filled with air, also called air gap, thus formed ensures thermal insulation between the heating element 50 and the cold surface of the envelope 72.

The heating element 50 placed in the body of the heating compartment 40 in contact with the heating surface 71 of the casing 72 generates the calories necessary for heating the gas flowing in the duct 10. An adequate mechanical adjustment, typically less than one millimeter ideally less than one-tenth of a millimeter, provides thermal conduction between the heating element 50 and the hot surface 71 of the casing 70. The heating element 50 may be formed of a heating resistive cartridge or a heating resistive wire. , which dissipates calories by ohmic effect According to another embodiment, the heating element 50 is formed of a resistive electrical track 51 deposited on a flexible electrically insulating support 52. This allows to distribute the heater over the entire heating surface 71 of the envelope 70, and the mechanical adjustment between the heating element and this surface can be achieved through an adhesive end 53, typically a few tens of microns thick, disposed between the heating element 50 and the heating surface 71 of the casing 70. In the particular case of a cylindrical duct and a cylindrical heating surface 71, heating element 50 then takes the form of a rectangle of length equal to the length of the heating surface 71 of the casing 70 and of width equal to the perimeter of the same cylindrical heating surface, as illustrated in FIGS. 3a and 3b. The resistive track 51, of ohmic resistance typically between 1 and 100 ohms, more particularly between 20 and 50 ohms, dissipates, when fed by an electric current, a thermal power equal to the square of the intensity of this current that multiply the value of its ohmic value.

According to another embodiment of the invention, the heating element 50 is an infrared light source oriented towards the heating surface 71. According to yet another embodiment, the heating element 50 is a source of a variable magnetic field. The eddy currents generated in the central tube 10, which must then be in a conductive material, heat it.

Moreover, a source of electrical energy 210 supplies the heating element 50 with electricity. This electrical source 210 may be disposed in the compartment 40 of the device of the invention, for example in the case of a battery, or outside thereof. When the electrical power source 210 is external to the compartment 40, an electrical connector 80, disposed in the compartment 40, allows the electrical connection of this external power source 210 to the heating element 50.

Such a power supply source may be the power supply network, usually delivering an alternating voltage between 110 and 230V, or a supply device delivering for example a DC voltage of between 5 and 48V, for example 12V.

A simple and inexpensive embodiment of the invention consists in directly supplying the heating element 50, electrically connected to the electrical connector 80, using the power source 210. In this case, the heating is effective when the power supply is connected. The temperatures reached by the heating element, the hot surface of the casing, and the gas at the outlet of the central duct are not measured. These temperatures depend on different parameters such as the temperature of the gas at the inlet of the central duct, the gas flow rate, the ambient room temperature, etc. Precise control of the heating performance is therefore not possible in this case. According to another embodiment, it is possible to use a control-command card 90 disposed in the compartment 40, which is electrically connected to the connector 80 and to the heating element 50, and to a temperature measuring element 95. , said "temperature sensor", electrically connected to the control-command card 90, and disposed in contact with the heating element 50 or the hot surface 71 of the casing 70, in order to measure the temperature. As a function of the temperature measured by the temperature sensor 95, the control-command card 90 then regulates the electric current or the electric voltage delivered to the heating element 50. This regulation makes it possible to maintain the heating element 50 and / or the hot surface 71 of the envelope 70 in the vicinity of a target temperature, typically between 35 and 80 ° C. Preferably, all-or-nothing regulation of the electrical voltage in the heating element 50 is carried out, targeting a given temperature, for example 50 ° C. A hysteresis of a few tenths of degrees, typically 1 ° C, may be added to avoid too many switching between the times when the heating element is powered and those when it is not. Of course, other embodiments are possible, for example those introducing a proportional control.

Another aspect of the invention consists in using different control elements, such as a switch, and warning, such as a light-emitting diode, allowing the user to stop the heating or to view the state of the heater or the good operation of the invention. These various elements can be, for example, electrically connected to the control-command card 90. It is also possible to provide security elements, such as an electric fuse, which can be arranged on the control-command card 90 in order to protect the device of the invention and the user, when using a non-compliant power supply 210. Similarly, it is possible to provide a thermal protection device that can be electrically connected in series with the heating element 50 and placed in contact with the heating element 50 or with the hot surface 71 of the envelope 70, making it possible to interrupt the power supply of the heating element 50 in case of abnormal overheating, for example when the temperature of the heating element exceeds 70 ° C. This device may or may not be resettable, whether by the user or when the temperature drops below a certain value, for example 60 ° C.

Claims (10)

REVENDICATIONS1. A gas heater (200) comprising: - a main gas duct (10) through which an internal passage (10 ') passes; - a heating compartment (40) comprising: an outer envelope (70) comprising a peripheral wall defining an internal volume (60), a heating element (50) arranged in the internal volume (60), and. a locking mechanism for detachably receiving the main gas duct (10), and wherein the gas main duct (10) and the heating element (50) are arranged on either side of the gas duct (10); a portion of the peripheral wall of the outer shell (70), and are in mechanical contact with said peripheral wall portion such that heat emitted by the heating element (50) passes through said peripheral wall portion prior to heating the main conduit (10) of gas. 2. Device according to the preceding claim, characterized in that said peripheral wall portion of the outer casing (70) is "sandwiched" between the main conduit (10) of gas and the heating element (50). 3. Device according to one of the preceding claims, characterized in that the heating element (50) comprises electrical connections 4. Device according to one of the preceding claims, characterized in that the outer casing (70) comprises an internal volume (60) filled with gas, in particular air, or a thermally insulating material, or said volume internal (60) is under vacuum. 5. Device according to one of the preceding claims, characterized in that the heating element (50) comprises a heating resistive cartridge30 6. Device according to one of claims 1 to 4, characterized in that the heating element (50) comprises a resistive electrical track (51) deposited on a flexible electrically insulating support (52). 7. Device according to one of the preceding claims, characterized in that the main conduit (10) is formed of at least one metal or plastic material. 8. Device according to one of the preceding claims, characterized in that the main duct (10) has a length of between 2 and 15 cm. 9. Device according to one of the preceding claims, characterized in that the wall of the main duct (10) has a thickness of between 1 and 5 mm Ventilation apparatus comprising a ventilator (100) comprising a looped patient circuit (150) with an inspiratory limb (120) and an expiratory limb (130), and a gas heater (200) according to one of the preceding claims arranged on the expiratory limb (130).