SE434339B - STERILIZABLE EVAPORATIVE HUMIDIFIER - Google Patents

Description

_ '.. n-nlnlw. 10 15 20 25 30 35 .-: *, vaevs11Äs 2 flow, required for adults. The humidification unit should also be able to provide an almost instantaneous heating and humidification, so that the unit is ready for immediate use in the event of an accident without the need to resort to a heating period and a continuous state can be achieved quickly, thereby minimizing temperature variations due to an extended heating period. be from 10 min to 60 min in now known_and available humidifiers. Respiratory systems often include an artificial respirator, which generates pulses of breathing gas to the patient via flexible connecting hoses. The respirator can produce either pulses of a given pressure or a given volume. The device can be set to produce pulses which are adapted to a particular patient, such as minors with small lung capacity or adults with large lung capacity. Normally the respirator is placed at a distance from the patient, so that the connecting hose contains a significant volume, which makes it difficult to accurately regulate the pulses. The humidifier is normally located on the connecting tube for feeding the breathing pulses, so that the internal volume of the humidifier also contributes more or less significantly to the connection volume between the respirator and the patient. Consequently, it would be advantageous if the internal volume of the humidifier were made as small as possible.

When the humidifier is used together with a. artificial respirator obviously pulses of respiratory gas will pass through the humidifier. These gas pulses have an instantaneous flow value, which starts at no fl. at the beginning of the pulse, increases to a maximum value and then drops again to zero at the end of the pulse. This maximum flow value is called the "peak value inhalation flow".

A humidifier can typically absorb inhalation flows with peaks exceeding the maximum continuous flow value of the humidifier, since the humidifier preheats the volume of gas present in the humidifier chamber between the pulses in addition to heating the pulsating gas through the pulsating gas. 10 15 20 25 30 35 7807917-5 3 rates. The stagnant gas will then be heated to a higher temperature than the pulsating gas and mixed in the humidification chamber, the mixed, humidified gas at the outlet of the humidifier having a substantially uniform temperature and pulse frequency.

Medical humidifiers mainly consist of three types: l) mist formers or spray types, 2) bubble types and 3) evaporative types or steam types. Other types or variations have been suggested from time to time, but these three categories, which will be described below, are the ones currently most used. l FOG FORMERS Fog formers are devices that are used for two different but sometimes combined purposes. In the simplest form, liquid from a container is passed through a tube, which terminates in a nozzle, at the outlet opening of which the liquid stream is atomized in fine droplets by means of a passing gas stream in about the same manner as the well-known atomizers used to atomize many ordinary liquid products for home use. Fog formers are useful for transferring a fine mist of drug in liquid form to a patient together with the respirator gas stream. The particle size of the droplets determines to some extent whether the mist will end up in the upper or lower airways. When used for humidification instead of inhalation therapy, ie when you only want humidification, some mist forms have screen walls to separate larger droplets, means for heating or other means for removing or evaporating the fine water droplets. None of the methods known today are completely satisfactory for complete removal of water droplets from the gas stream. Excess drops can not only have a traumatic effect on a weakened patient but also form organs for transporting microorganisms into the patient's respiratory organs. Such microorganisms are not so easily transported by means of humidifying gas in the absence of water droplets. It is also difficult to achieve heating of respirator air to a physiologically acceptable temperature in an atomizer process. n 10 lsl 20 25 30 '35 '1807917-5 2 BUBBLE HUMIDIFIERS These humidifiers usually work by blowing air through a pipe and releasing the air near the bottom of a water tank, after which the air is allowed to bubble up through the water. Since the normal ascent of the bubbles along a short distance in the water does not provide sufficient humidification and / or heating of the gas bubbles, these devices are usually equipped with screen walls, porous filling or the like for dividing the bubbles and slowing their ascent rate.

The water can be heated in a bubble humidifier. The main disadvantage of bubble humidifiers is probably the pressure required to press the air down to the bottom of the liquid container, whereby a pressure drop then formed effectively precludes the use of oxygen / gas venturi mixers. 3 EVAPORATIVE HUMIDIFIER This type of humidifier is the latest type and has quickly gained recognition due to its advantages over the two previously mentioned types of humidifiers.

In the simplest form of evaporative humidifier, the gas absorbs moisture by passing it past a wet surface. The efficiency, which is determined by the increase in humidity, can be increased by increasing the wet contact surface in the form of a two-dimensional surface or by increasing the surface porosity or structure. The efficiency can be further increased by heating the water directly or indirectly by heating the evaporative surface or by heating the air.

Further increase of the evaporation can be achieved by increasing the flow rate of the air or increasing the turbulence at the boundary layer. Heating of the air by means of the evaporative surface can be effected by supersaturation of the air, whereby the air is heated, which, however, can lead to mist formation. Evaporative humidifiers provide advantages over other types of humidifiers by achieving a high moisture content per unit volume without the formation of water droplets. The present invention relates to an evaporative humidifier having a humidification chamber having an inner humidifier. - ~ --- ~ - ~ - ----- 77807917-5 5 volume of approximately 200 cm3 and an inlet opening and an outlet opening for gas, a liquid container and a removable porous evaporating element with an open cylindrical shape, which, ¿When it is dry, with spills fit in the humidification chamber but 5 which, when wet, swells and forms good thermal contact, with the side walls of the chamber and extends down into the liquid container. The chamber is tightly surrounded by a heating element, so that little heat is transferred directly to the chamber walls next to the porous, removable evaporation element and not to the liquid container. The heating element is preferably equipped with suitable electronic control means for measuring the heat transfer surface temperature and switching off the element, when the temperature exceeds a predetermined level. The humidifier is designed so that the gases reaching the patient will have 100% relative humidity under most gas flow conditions and heater temperature settings. The invention will be described in more detail below with an exemplary embodiment with reference to the accompanying drawing. Fig. 1 shows from above and partly in section a humidifier according to the present invention and Fig. 2 shows a longitudinal section of the humidifier according to the invention.

A humidifier 10 has a substantially cylindrical housing 11, which includes a central humidification chamber 25 having an inner volume of about 200 cm 3, a removable airflow cover §15, to which suitable hoses (not shown) are connectable, and a removable bottom cover 24 The cover: 15 is fitted by friction and mechanical engagement to the upper part of the housing by means of a bayonet socket and an O-ring 30 '18, which provides a leak-proof seal. An air inlet pipe 16 and a air outlet pipe 17, the size of which is such that the commonly used corrugated respiration hoses can be quickly and easily attached thereto, are made in one piece with the housing 15, as shown in Fig. 1. An air rectifier 35 'pipe 19 projects downwardly from the housing 15 and serves to direct the inflowing air from the air inlet pipe 16 to the interior of the humidifier 10, so that inflowing air must flow upwards along most of the length of the humidifying chamber 20 and an evaporation element 35. A water inlet 21 7897917-5 10 15 20 25 30 35 6 6 is also made in one piece with the cover 15 and a water supply pipe 22 projects downwards from the water inlet 21. The cover 15 can be provided with a sensor element for the outlet gas temperature, e.g. a thermistor , which can measure the temperature of the exhaust gas and switch off the heating element, when the temperature exceeds a preset level. The air flow cover 15, which is removable from the housing 11 of the humidifier 10, facilitates cleaning and / or sterilization of the unit. Alternatively, the air flow cover 15 can be made integral with the housing 11, so that only the bottom cover 24 is removable. The cover 15 is preferably formed of polypropylene with 20% glass blend, although it could be made of die-cast metal or other polymeric materials, such as nylon, epoxy, etc. However, it is preferred that the material used be able to withstand repeated cycles of sterilization. Less durable materials should be gas sterilizable.

The air deflector pipe 19 has a cross-sectional area which is comparable in size to the cross-sectional area of the air inlet pipe 16, so that excessive pressure drops do not occur. The pressure drop in the humidifier according to the present invention is very small and in the order of 0.1 cm of water column at a continuous flow of 30 l / min. For the same reason, the space between the air deflector tube 19 and the surrounding evaporation element 35 should have a comparable cross-sectional area. The air deflector tube 19 projects downwards and terminates close to the bottom of the humidification chamber 20, so that the air must flow upwards along most of the length of the evaporation element 35. The effect would only be reduced slightly if the pipe was shortened and compensating means were designed by shaping the pipe outlet as a slightly throttling nozzle or into a circular or cyclone-shaped gas outlet with only a slightly increasing pressure drop. Alternatively, the gas flow could be reversed, i.e. inflow of gas from the right according to Fig. 1, downwards around the air deflector tube 19, up through this tube and out to the left. Other air flow paths are also within the scope of the present invention, for example air inlets or air outlets in the upper or lower part of the humidifier 10. The water inlet 211 shown at the top of the humidifier 10 according to Fig. 1 can be connected to a supply pipe (not shown) from a container with distilled water, for example an Iv container, which is located high for flow through the action of gravity. The water supply pipe 22 is made of a stainless steel pipe of quality 316 (American standard AISI) with an outer diameter of 0.313 cm and an inner diameter of 0.173 cm. For better flow restriction, a valve nozzle 23 is arranged in the lower end of the water supply pipe 22 and formed with a restricted opening, the inner diameter of which is 0.050 cm. It is also within the scope of the invention to provide an enlarged water container at the bottom of the apparatus, which container allows use of the apparatus for a long time without water having to be supplied from the outside, provided that such a water container is placed so that the water in the container is not in contact with a heating pipe 31.

In the preferred embodiment, the bottom cover 24 acts as a liquid container. A central, upright guide pin 25 is integral with the bottom cover 24 and serves to locate a float 26, although it allows the float to move freely up and down depending on the level of liquid in the container. The float 26 has a valve seat 29, which shuts off the flow of water from the valve nozzle 23, when the water level in the container reaches a predetermined level.

The bottom cover 24 is preferably formed of clear, unmixed polycarbonate, so that the amount of water in the container can be observed from the outside. The cover is screwed onto the housing 11 for abutment against a sealing O-ring 30 so that the cover can be easily removed and replaced without the use of tools and provide a leak-proof engagement. The bottom cover 24 can of course be formed as part of the housing 11, the air flow cover 15 having to be removable for cleaning the humidifier 10 and replacing the evaporator element 35. This would be a preferred construction when an enlarged water tank is desired.

The float 26 is normally made of two separate, clear polycarbonate elements, which are constituted by an upper part 27 and a lower part 28, which are assembled in a leak-proof manner by, for example, ultrasonic welding. Of course, an adhesive can be used to assemble the two elements. The float upper part 27 comprises a valve seat 29 of a 0.15 cm thick silicone rubber, which is typically retained by means of a suitable glue.

The housing 11 is also made of polypropylene with 20% glass mixture and carries the removable heating tube 31, which is an aluminum tube with an outer diameter of 4.688 cm.

An electric heating element 32 (200 W, 120 V) in the form of a layer embedded in silicone rubber is wound around the heating tube 31 and preferably vulcanized thereon. A thermally insulating layer 33, which is preferably a 0.156 cm thick silicone sponge rubber layer, covers the heating element 32. At least one temperature sensing element, for example a thermistor 34, is attached to the heating element 32.

The housing 11 is made in two parts, which are assembled by means of a plurality of locking fingers, which are placed around and hang down from the periphery of an annular upper part 12.

An O-ring 14 forms a seal between the upper portion 12 and a lower portion 13. The heating element 32 and the heating tube 31 are permanently mounted and "sealed" in the housing 11. An O-ring 14a forms a substantially leak-proof seal around the bottom periphery of the tube 31. Alternatively, the entire outer cavity can be filled with thermal insulation material, such as foam plastic.

The humidifier 10 according to the present invention is intended to be connected to a separate unit, which comprises suitable electronic control devices and electrical power supply connection means. It is of course possible to tightly enclose the electronic control devices in the housing 11 in a waterproof manner, so that the external connecting means, which is necessary, becomes the electrical connection cable. The electronic control means of conventional design provide the necessary functions for switching the humidifier on and off, measuring and regulating the temperature of the heat transfer surface of the heating tube 31 and the temperature of the gases reaching the patient. The heat transfer surface temperature of the heating tube 31 is sensed by the thermistor 34, which is embedded in the heating element 32. This information is fed to a thermostatic control circuit of the electronic control means, the temperature being maintained at a constant value of one. a selected setting. The heat transfer surface temperatures that can be selected are between 40 and 100 ° C.

If the heat transfer surface temperature exceeds a certain predetermined temperature (eg 127 ° C or 139 ° C), a thermal shut-off device (not shown) in the heating element 32 will melt and break the heating circuit and inactivate the heating element 32. The primary (and possibly the only) situation , when this could occur, there would be such a fault in the thermostat control circuit that the heating element is set to full power. The thermal shut-off device will thus protect the humidifier housing 11 from melting or burning.

Experience has shown that the evaporative element or wick 35 should be arranged so that it can be removed, discarded and replaced after each use, thereby eliminating a potential source of infection. Since the cost of a disposable article is significant, the wick should be made of relatively inexpensive materials.

By using evaporation as in the present invention, wherein the evaporation element or wick 35 is in direct contact with the heat transfer surface of the heating tube 31 over a short distance, the degree of evaporation is greatly increased and the evaporation value per unit area becomes very high, which allows the use of a very small evaporation surface. With this high evaporation value per unit area, it is necessary that the liquid absorption capacity is also high, so that the rapidly evaporated water is exchanged quickly. Unfortunately, materials with good wet strength properties have reduced liquid wicking ability due to the fact that the water-resistant reinforcement materials provide reduced wettability to the reinforced structure.

It has been unexpectedly found that certain types of paper tend to swell a lot when wetted, thereby increasing their outer diameter. Paper is, of course, a suitable material due to its low cost and natural wettability, which contributes to good liquid wicking ability. To take full advantage of this phenomenon, it is crucial that both the wick 35 and the heat transfer surface of the heating tube 31 be either cylindrical or frustoconical and that the wick be so disposed within the heat transfer surface that the wick 35 may be shrunk when dry, and swell to good thermal contact with the heat transfer surface, when wet.

The preferred form of the wick 35 comprises a laminate of two layers of absorbent material, the inner layer having good rigidity and dimensional stability, especially when the layer is wet, and the outer layer having good liquid absorbency and swelling properties. In this embodiment, the wick 35 consists of an outer layer of "Scott Hi-Loft 3055 non-woven paper" having a basis weight of 25 kg from "Scott Paper Company, Chester, Pennsylvania" and an inner layer of "Jamer River - Pepperrell. , Inc., P 2212, Grade 06101A, Bleached Absorbent Wet Strength Kraft paper "with a basis weight of approximately 43 kg. Lamination can be achieved by gluing, heat sealing, needling, etc. but must not cause a complete moisture barrier between the two layers , because the outer, highly absorbent layer must be able to transfer water horizontally to the inner layer, so that the inner layer with relatively poor liquid absorption capacity does not have to depend solely on its own vertical liquid absorption capacity to remain wet when water evaporates from the layer. To prevent the formation of a complete moisture barrier between the layers, glue or heat is applied to one of the primary properties of the highly absorbent outer layer. sealing material, if used, in the form of thin strips or stains.

When the materials are joined, the resulting laminate is formed on a cylindrical core or folded so that the edges overlap each other slightly or are applied end to end and joined together by gluing, heat sealing, a sewing process or any other suitable means. Wicks 35 are then cut to appropriate lengths and flattened (if shaped on the cylindrical core) for packaging, transport and storage. By giving the wick 35 after manufacture a flat shape instead of a cylindrical shape, the necessary transport and storage space is reduced by approximately 80%.

The cylindrical shape required for normal operation of the wick 35 is quickly restored by pressing the wick in opposite directions along the opposite folding edges and inserting the wick into the heating tube 31. The rigidity of the inner layer material causes the wick 35 to easily open into a substantially cylindrical shape.

When the wick 35, which is made according to the technique above, regains its cylindrical shape, the outer diameter will vary slightly from wick to wick. This variation is not a problem because the wet swelling property of the wick allows good thermal contact despite this variation in outer diameter. The absorbency of this laminate is such that a water suction exceeding 5 cm in height is achieved within 60 s when the lower end of the wick is placed in a shallow water container. The degree of swelling, when the laminate is wetted, is sufficient to achieve a 1-3% increase in the outer diameter. Another form of wick comprises a laminate of at least three layers of absorbent material, the innermost layer having good wet strength properties and one of the outer layers having good liquid absorption and swelling properties. In this embodiment, the wick 35 comprises a composite outer layer of two sheets of "Scott Hi-Loft 3055 non-woven paper" having a basis weight of 25 kg and two inner layers of "Monadnock 1309-030 paper", which is a high wet strength paper and a basis weight of about 14 kg. The three separate layers are laminated and lightly glued together by successively winding each of the layers at an angle around a forming cylinder to provide a solid "core" and cut the core to desired lengths, similar to the process. used in the manufacture of cores for toilet paper rolls. It will be appreciated that this method of manufacture provides a cylinder with accurately dimensioned inner diameter but with variable outer diameter. However, this is not a problem due to the wet swelling properties of the wick, which allow good thermal contact despite outer diameter variation. The absorbency of this laminate is such that a suction exceeding 7.5 cm is achieved within 60 s, when the lower end of the wick is placed in a shallow water container. The degree of swelling of this wick, when wetted, is sufficient to bring about a 2-3% increase in the outer diameter. Another wick was made of a paper made of "100% Nersanier XJ pulp". Flat sheets of this paper measuring 13.7 x 11.4 x 0.102 were rolled into open cylinders at the ends which were 11.4 cm long and had an outer diameter of about 4.44 cm. The cylinders were sealed by heat sealing by means of a polyester-polypropylene laminate film adhesive strip along the joint. This construction provides low wet strength, so care must be taken when removing a wet wick from the humidifier without tearing the wick. The paper swelled when wetted, so that the thickness increased by about 85%, which resulted in an increase in the outer diameter of about 0.089 cm and resulted in good wet contact with the inner surface of the heating tube 31. The wicks had 5 cm absorption for 2 min, which was just pretty good but perfectly acceptable.

Other wicks are made by spirally wrapping four layers of "N-2380 non-woven webs" from C.H. Dexter Division of Decter Corporation "on a core to form a laminate.

Parts of the "web" strip of wrapping paper were covered with glue for joining the laminate. Each layer was approximately 0.25 cm thick.

The thickness of this wick increased approximately 33% when the wick was wetted, which resulted in an increase in the outer diameter of approximately 0.038 cm. The wet wicks could be easily removed from the humidifier without breaking. The finished wick had an absorption capacity of 7.5 cm for 2 minutes, which was more than sufficient.

The following is a description of the operation of the humidifier of the present invention. Before the humidifier 10 is put into use, it is dismantled and its various components are sterilized or otherwise treated sanitized depending on the hospital's practice and / or the patient's health condition. A new wick 35 is inserted into the heating tube 31 during the assembly of the humidifier either before or after sterilization, the electronic control means are connected and a water supply tube from a container of distilled water is connected to the water inlet 21.

Finally, suitable respirator hoses from the patient and the respirator are connected to the humidifier 17 or air inlet 16 of the humidifier 10, respectively. When the power supply cord is connected to a suitable power source, the electronic control means are set and the humidifier is turned on almost immediately. % relative humidity in the exhaust gas is achieved within 1-2 minutes.

The temperature sensing thermistor 34 attached to the heating element 32 allows the electronic control means to operate and deactivate the heating element 32 for short time intervals to control the temperature of the heating tube 31 within narrow limits, which in turn regulates the temperature within 1 ° C of the saturated gas, which when patients. The controller setting is controlled by the operator according to the temperature of the saturated air reaching the patient. The relationship between the setting and the air temperature at the patient will depend on the volumetric review of the system, which is a variable that changes from patient to patient.

The humidifier according to the present invention normally supplies the patient with respirator gases with 100% relative humidity at a temperature of 25-40 ° C and a continuous flow of 1-60 l / min and an inhalation flow with a peak value of up to 100 l / min. Due to the high evaporation value, the surface of the recovery pipe 31 will normally maintain a rather low temperature, eg 71 ° C, in comparison with the higher temperatures which have occurred with other known humidifiers. If for any reason the temperature selected by the operator is too high or the temperature is too high due to a fault in the thermostat control circuit, the temperature of the air, which reaches the patient, would increase. In this case, the exhaust gas sensor element or the temperature sensor arranged close to the patient would switch off the humidifier and activate a sound or visual alarm means. Shut-off of the humidifier normally occurs when the gas temperature of the patient exceeds 41 ° C.

As a further safety factor, the thermal shut-off device is caused to disconnect the energy source of the humidifier when an excessive temperature rise is present at the heat transfer surface of the heating tube 31.

Claims (5)

10 15 _20 25 30 i7ae7917-s 15 PATENTKRAV A sterilizable evaporative humidifier having a humidification chamber (20) having an inlet port (16) and a gas outlet port (17), a liquid container (24), and a disposable porous evaporator member (35), one end extends into the liquid container for absorbing the liquid in the whole body of the element, the holder having a float valve (26) for regulating the liquid level in the container; that the apparatus further has a heating element (31) isolated from the liquid container thereof, that said liquid container and electronically controlled; that the humidification chamber is so surrounded by the heating element that heat is transferred directly from the wall of the chamber to the evaporation element; that the porous evaporating element is a cylinder open at the ends, which in the dry state is loosely arranged inside the humidification chamber (20) and in the wet state swells to close contact with the side wall of the chamber; that the flow path for the gases into and through the chamber takes place from the inlet opening, along the inside of the porous evaporation element and then through the outlet opening; and that the apparatus is easily demountable in its components due to sterilization. 2. A humidifier according to claim 1, characterized in that the humidifier chamber (20) has an internal volume of about 200 cm 3; that the evaporation element has a vertical suction capacity of about 5 cm during the first minute; that the device allows supply of respirator gases to the patient with 100% relative humidity, a temperature of 25-40 ° C within 2 minutes from start-up, a continuous flow of from about 1 to about 60 liters / min and an inhalation flow with a peak value of about 10 to 100 liters / min, whereby the pressure drop in the apparatus is about 0.1 cm of water column at a continuous flow of 30 liters / min. 10 15 veovøiv-s Ü. .76 Humidifier according to claim 1, characterized in that the porous evaporation element (35) comprises cellulosic material which is assembled by means of a water-insoluble glue. Humidifier according to claim 3, characterized in that the porous evaporating element (35) is a laminate of a non-woven cellulosic paper with high liquid absorbency and a dimensionally stable, absorbent paper with high wet strength. Humidifier according to claim 1, characterized by electronic control means (34) for interrupting the power supply to the humidifier, when the temperature of the heating element (32) or the gases at the patient has exceeded a predetermined temperature level.