Humidifying Means

Abstract

A humidifying means has a container for water which is removable from a source of heat, with the container being provided with a cover defining an air space with an inlet for gases and an outlet for gases and water vapor, the whole being removable for sterilization or other purposes. Temperature control means are provided externally of the container to control the temperature of the water in the container. A hose connects the outlet for gases and water vapor to a patient undergoing assisted or artificial respiration and this hose has a heating element therein arranged longitudinally to reduce or obviate condensation in the hose.

Description

BACKGROUND OF THE INVENTION

This invention relates to humidifying means.

In humidifying means, for use, for example for humidifying and heating air or gases which is to be breathed by a patient undergoing artificial respiration, there is a need for a humidifying means which is capable of having portions thereof readily sterilized yet enabling adequate and accurate control of the temperature, and the saturation of the air passed through the humidifying means. In order to control the temperature and the humidity of the air at any selected temperature, elaborate and sophisticated controls are necessary, usually electronic, and of course such electronic apparatus may not be immersed in water, for example, for the purpose of sterilizing.

It is, therefore, an object of the present invention in one aspect to provide humidifying apparatus which is simple to construct yet effective in use, and which will at least go a considerable way towards meeting the foregoing desiderata or which will at least provide the public with a useful choice.

SUMMARY OF THE INVENTION

Accordingly, in one aspect, the invention consists in apparatus for humidifying and heating air, comprising a container for water to be converted into water vapor at a desired temperature, said container being adapted to be heated externally, and being adapted to be removed from the source of heat for the purpose of sterilization or other purposes, cover means for said container adapted to provide an air space above the level of water, heat transfer means adapted to be mounted within said container and comprising conducting means adapted to conduct heat to evaporating surfaces in said air space above the level of water in said container, air inlet means adapted to admit gases into said air space, vapor transfer means adapted to transmit vapor from said air space to gases passing therethrough, gas and vapor outlet means, heating means separate from said container, means for maintaining said container in thermal contact with said heating means, and control means to sense the temperature of the water contained in said container, with the construction and arrangement being such that, in use, on said container being heated by said heating means, such heat will be transferred by conduction through said conducting means to said evaporating surface in said air space for transfer into the gases passing through said air space so that a mixture of water vapor and gases can be transferred from said air space, said heat control means being adapted to control the temperature and, therefore, the moisture content of such gases transferred from said air space.

We have also found that it is desirable to provide further heating means in a tube forming part of humidifying means and which connects the humidifying source to, for example, a patient to whom humidified gases are to be provided. Previously, it had been thought that spiral electric heating means were necessary to maintain adequate heating, but such heating means are complicated and expensive to produce.

It is therefore, an object of the present invention in a further aspect, to provide humidifying apparatus which will obviate or minimize the foregoing disadvantage in a simple yet effective manner or which will at least provide the public with a useful choice.

Accordingly, in a further aspect, the invention consists in apparatus for humidifying and heating air to be breathed by a patient undergoing assisted or artificial respiration, comprising humidification and heating means adapted to heat air to a suitable temperature which does not exceed, under steady operating conditions, the maximum desired temperature at which the air is desired to be admitted into the patient's body, and to substantially saturate the air with water vapor at that output temperature, and further heating means to further heat the substantially saturated air from said output temperature, with the air heated by said further heating means being carried, in use, through auxiliary apparatus into the patient's body, characterized in that said further heating means comprise a tube adapted to carry humidified air from said humidification and heating means, to said auxiliary apparatus, said tube carrying at least one insulated electrically energizable heating wire arranged longitudinally of said tube, the construction and arrangement being such that in use, the increase in temperature of the air to be breathed which is imparted by said further heating means at the output thereof, is selected to be equal to or to exceed the temperature drop which occurs in the air so heated in its passage between said output of said further heating means and the patient's body and, in any event, the temperature increase is adjusted to ensure that the air is delivered to the patient at no more than said maximum desired temperature.

One preferred form of the invention will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective exploded view of a humidifying apparatus according to the invention, a delivery module, a humidifying module and a heater module shown detached one from the other,

FIG. 2 is a plan view of the construction shown in FIG. 1 with the delivery module detached,

FIG. 3 is a section on the line A--A of FIG. 2 the view looking in the direction of the arrows,

FIG. 4 is a wiring diagram for the heating and control apparatus utilized in the humidifying apparatus shown in FIGS. 1 to 3.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, the humidifying apparatus shown in FIGS. 1 to 3, is referred as a matter of convenience in the following into a delivery module 1, a humidifying module 2, and a heater module 3. The delivery module 1 comprises a cap member 4, having an inlet 5 for humidified gases e.g. air and oxygen hereinafter referred to simply as air, and an added outlet 6, with the outlet 6 being connected to a tube 7 which has therein a heating element 8 in the form of a wire hairpin, that is to say, the wire extends from a terminal unit 9 or near to the opposite end of the tube 7, and then returns to the terminal unit 9. The terminal unit 9 is supplied through a cable 10, connected to the heater module 3 as will later be described. The cap 4 also includes a water filler cap 11 which may be removed for adding water to a container 12 forming part of the humidifying module 2, as will further described.

The air inlet 5 of the cap 4 fits on an air outlet 13, leading from the humidifying module 2. This module will now be described in detail.

The container 12, preferably of transparent material, has an open mouth 14, and a disc bottom 15, with the disc bottom being substantially flat so as to have a considerable bearing surface on a heating plate 16 forming part of the heater module 3. The container 12 is provided with lugs 17 and 18. A cover 19 is provided, having the air outlet 13, and also an air inlet 20. The cover 19 is also preferably of a transparent material so that water levels can be examined within the container 12, and the cover is sealed to the container 12 by an O-ring 21. It is a feature of the invention that the container 12 may not be over-filled without it being clearly obvious to the attendant, since filling to the level of the open-mouth 14 will cause overflow into a space 22, between the cover and the container 12, so that the container may be readily filled with a predetermined amount of water i.e. to the level of the mouth 14. It is to be noted that the inlet 20 is an inlet for air and the other gases, e.g. added oxygen to be humidified.

Mounted within the container 12 are conducting means which, preferably, comprise a scroll 23 preferably of metal e.g. aluminum plate of a suitable gauge, e.g. 12g., and having a sufficient number of turns as to provide an adequate evaporating surface area, to evaporating means or vapor transfer means associated with the scroll comprising, e.g. blotting paper 24 placed in contact with the surface of the scroll in the air space 25 in an cover 19 above the open mouth 14 of the container 12, with the blotting paper also dipping into the water. We have been surprised by the fact that there has been adequate transfer of heat from the floor of the container to the scroll.

The air space and the filled water space are about equal in volume in use. The cover 19 is fixed to the container 12 by the cover 19 also having lugs 26 and a ring 27 has an annulus 28 and lugs 29, with the annulus 28 pressing against the lugs 26 and the lugs 29 engaging below the lugs 17 of the container. The ring is given a twist action in use so that spaces, not shown, between the lugs 29 can pass over the lugs 17 for separating the cover from the container.

This completes the container, and it will be seen that the container and its cover are of extremely simple construction which may be removed readily, and may be sterilized or otherwise dealt with without hindrance by temperature control devices or other features which would otherwise prevent adequate sterilization.

As stated above, the heater module 3 includes a heater plate 16 and the plate is provided with a heating element 31 therein. The heater plate 16 is mounted on springs 32 equipped with holding bolts 33, and for example, three such spring mountings are provided. The purpose thereof is to ensure that there is close contact between the plate 16 and the bottom 15 of the container 12. Normally, the plate 16 stands above members 34, but when the container is pressed onto the plate 16, and the lugs 18 held onto heater module body 35 by a ring 36 having a flange and annulus 37 which has lugs 38 engaging with further lugs 39 forming a part of the body 35. Again rotation of the ring 36 engages or disengages the lugs 38 and 39.

In order to control the temperature of the water in the container 12, a temperature sensing device is provided in contact with the bottom 15 of the container, thus a thermister 40 is mounted in an opening in the heating plate and being insulated therefrom by a heat insulant 41. Thus, the thermistor is arranged to be in close contact with the bottom plate 15, and we have found that to a satisfactory extent this enables close control of the temperature in the water of container 12, while permitting removal of that container for sterilizing purposes.

Indicating lights are provided to indicate satisfactory operation of the apparatus and, for example, lights 42 and 43 are arranged to shine through a lens 44 which is a transparent plate fitted in the body 35, a a green filter 45 is interposed between the lights and the lens 34. A main switch 46 controls supply to the equipment and a thumb screw 47 forms part of a clamp 48 which may be fixed to a standard to prevent the apparatus being knocked over.

Turning now to the circuit shown in FIG. 4, the circuit is divided into blocks or modules comprising a hose heater control module generally referenced 48, a heater thermostat module 49, a power control module 50 and other associated equipment which will be referred to further in the following.

A transformer 51 supplies current at suitable voltages. In particular, it supplies 24v. to the heater wire 8. The transformer 51 also has a 19v. supply 52, to be later discussed.

The hose heater control module 48 comprises a bridge rectifier circuit having rectifiers 52 and 72 supplying a silicon controlled rectifier 53. A variable resistance 54 enables control of the supply to the heater 8 manually, and a pre-set control 55 is a trimmer control normally pre-set to adjust the phase shift of the supply to a 90.degree. phase shift, that is to say, supplying minimum supply current to the heater 8.

The thermostat control module 49 is supplied from a 19v. tap 56 and has a bridge circuit comprising resistors 58, 59 and 60 which are fixed resistors, and in the fourth arm of the bridge, there is the thermistor 40 together with a calibrating variable resistor 61. The bridge is supplied through a resistance 63 and regulated by a zener diode 62 supplying a balanced voltage feed into the differential input of an operational amplifier 64, for example, a m.mu. A741C as made by Fair-child Semi-conductors Inc. The amplified drive from the amplifier 64 supplies a reed relay 65, the contacts of which are shown at 66, and will be referred to later. A positive feed back is given through lead 66a, and resistor 67 to a non-inverting input 68 of the amplifier 64 for the purpose of giving added stability resulting in a small differential to be used in operation.

The power module 50 is fed at the input voltage, e.g. 230 volts 50 Hz and heating element 31 in FIG. 3 is divided into two sections 33A and 33B in the wiring diagram. These elements are supplied through a Triac 69 which is triggered by operation of the switch contacts 66 which apply a signal to the gate 67 of the Triac. It is a particular feature of the invention that the arrangement of the reed relay 65 is such that the low voltage circuits are electrically isolated from the mains voltage circuits of which the contacts 66 of the reed relay form part. A resistor 70 is provided to control the potential applied to the gate 67 to eliminate random and spurious triggering of the Triac 69.

Display units are provided to indicate operation of the circuitry, and as mentioned above, the lights 42 and 43 are arranged to show through the green filter 45 when operation is normal, and thus, the lights 42 and 43 form the load of a silicon controlled rectifier 71.

The operation is as follows and refers to the positive half-cycle of the 24v line 57. Owing to the turn-on delay of the S.C.R. 53, the potential at the junction of diodes 52 is such that S.C.R. 71 will be turned on prior to the turn on of S.C.R. 53. If, for any reason, pin 73 is at zero potential relative to lead 74, the S.C.R. 71 will not turn on, and, consequently, lights 42 and 43 will not be illuminated. Since the supply is still connected through lead 75, the potential at the anode of S.C.R. 71 will go positive, and through diode 76 will charge capacitor 77, forward biasing diode 78 which is connected through lead 79 to inverting input 80 of the amplifier 64. This turns the amplifier off, thus removing power by opening contacts 66 of the reed relay 65. Consequently, the heater does not come on under these circumstances. The potential at pin 73 can be zero either through the hose heater 8 being open circuited or not plugged in. Resistor 81 is connected in the circuit to ensure that if there is any reasonably high resistance across the heater terminals 9, the safety features will still operate. Resistor 82 ensures that the safety features will still operate, even if lamps 42 and 43 are open circuited. Resistors 83 assist in lengthening the life of the bulbs by restricting current surges when switching on.

In the case of over-heat conditions, when a back up thermostat 84 closes, it either open circuits fuse 85 or the element section 33. This reduces power to the heater circuitry and, as a result thereof, there is a circuit through red neon lights 86 indicating this malfunction. This circuit is now a high-resistance circuit, because added resistors 87 are of a high value and, consequently, the power is reduced to transformer 51 through lead 88 because of such high resistance in series with the transformer primary. Because of the feed through the transformer primary, the neon lights 86 remain illuminated even though the switch 84 may reopen, until either fuse 85 or the heater section 33 has been repaired.

The tube 7 is connected to auxiliary apparatus, for example, a mouthpiece or other device through which air may be supplied to a patient undergoing artificial respiration. A suitable type of heating element for the hair pin or hair pins 8 would be the resistance wire utilized for electric blanket manufacture.

The energy supplied to the resistance wire 8, in the tube is, of course, controlled so that in use, the increase in temperature of the air to be breathed which is imparted by the resistance element is selected to be equal to or exceed the temperature drop which occurs in the air so heated in its passage between the output of the humidifying means and the patient's body, and in any event, the temperature increase is adjusted to ensure that the air is delivered to the patient at no more than a maximum desired temperature. The tube 7 is selected so that it has reasonable flexibility, having regard to the use for which it is intended, and the tube wall a reasonable thickness and/or insulating properties so that the heat from the heating element is contained within the tube rather than being dissipated from the outer wall of the tube. A suitable material is a plasticized PVC.

In the foregoing, it can be seen that a humidifying apparatus is provided in which the humidifying module can be readily detached from the heating module, for sterilization filling, changing of the blotting paper, or for other servicing or other requirements, very simply and quickly. The safety devices result in operation which will have a considerable regard to the patient's safety, with the construction being such that should one module fail, other modules are cut off from the electrical supply or the electrical supply is reduced so that the patient gets simply saturated air and other gases, e.g. oxygen at room temperature which is preferable to his obtaining overheated air.

Claims

We claim:

1. An apparatus for humidifying and heating air to be breathed by a patient undergoing artificial respiration, comprising humidification and heating means to heat air to a suitable temperature which does not exceed, under steady operating conditions, the maximum desired temperature at which the air is to be admitted into the patient's body, and to substantially saturate the air with water vapor at that output temperature; said humidification and heating means comprising a body portion having a first part thereof defining a water container adapted to be pressurized and adapted to have water introduced therein from time to time in use; and a second part cooperable with the first part for providing an air space above the level of water in the first part, external heating means for said first part, said first part being adapted to be maintained in thermal contact with said external heating means, and control means to sense the temperature of the water contained in said first part and control the external heating means to maintain the temperature of the water at the desired level, releasable clamping means clamping said first part to said external heating means to permit said first part to be removed from the external heating means for sterilization or other purposes, a heat conductive plate defining a tortuous path provided with suitably spaced convolutions defining a core with a central axis therethrough, said heat conductive plate being located partly in said first part and partly in said air space defined by the first and second parts; a water absorbent material disposed along the tortuous path defined by said heat conductive plate; said second part having first and second air passage defining means providing communication between the interior of the body portion and the exterior thereof, said first air passage defining means adapted to be put in flow communication with a patient and said second passage defining means being adapted to be connected with a source of gas, at least the entrance of said first air passage defining means constituting an air outlet being above water level and in flow communication with the core of the tortuous path, with said water absorbent material being partially immersed in water in the first part, said heat conductive plate arranged with its axis substantially vertical in use and also being partially immersed in water in the first part to provide a lower seal for said tortuous path, said conductive plate having a top surface substantially in sealing engagement with said first part so that substantially all the air passing in either of said first or second air passage defining means in the inlet passage can only leave via the other air passage defining means and after passing through said tortuous path during which it gains an increased heat and water vapor content.

2. Apparatus as claimed in claim 1, wherein said second part is a cover, with the cover having sufficient volume as to provide the air space above the first part, the construction and arrangement being such that over filling of the first part is not readily possible.

3. Apparatus as claimed in claim 1, wherein said heat conducting plate is a scroll having a base adapted to rest on the floor of said first part, so that heat may be conducted from the floor or said first part to said scroll.

4. Apparatus as claimed in claim 3, wherein said scroll is faced on at least one surface with blotting paper which constitutes the water absorbent material.

5. Apparatus as claimed in claim 1 including a heating module, said heating means being spring mounted on said heating module, and the floor of said first part being pressed against the spring mounted heating means to provide good contact between the heating means and the floor of the first part.

6. Apparatus as claimed in claim 5, wherein said releasable clamping means includes a ring having a flange adapted to press against lugs on said first part, and said ring having further lugs adapted to engage lugs for said heating module, with rotation of the ring engaging the lugs to clamp the first part to the heating module.

7. Apparatus as claimed in claim 6, wherein the second part is held to said first part by a ring having a flange adapted to engage lugs on the second part, and said ring having flanges adapted to engage flanges for said first part, with rotation of said ring causing engagement of said lugs to hold the second part to the first part.

8. Apparatus as claimed in claim 7, wherein said second part is sealed to said first part by an O-ring between adjacent walls of the first and second parts.

9. Apparatus as claimed in claim 1, including a tube attached to said first air defining means to carry gases and vapor from said air outlet through an auxiliary apparatus into the body of a patient and said tube carrying at least one insulating electrical energizable heating wire arranged longitudinally thereof to further heat the substantially saturated air from the outlet temperature.