MEDICAL BREATHING APPARATUS

Abstract: A breathing apparatus of the kind having a water chamber (9) in which a heating element (23) is immersed, the temperature of said element being controlled so that air drawn over the heated water (14) is maintained at or close to a required humidity and temperature at an outlet, the volume of the air passing through the apparatus being substantially greater than that required for breathing and being directed into a face mask (5) connectable to the outlet which is formed with vents (7) through which excess moist/heated air together with air exhaled by the user can pass to atmosphere, is characterised in that the casing (1) for the apparatus is in two parts, comprising a base (2) and a removable housing (3), in that the base (2) accommodates a water tank (9) and has a column (4) extending upwards therefrom which defines an air path from the water tank (9), in that the face mask (5) is connected to the upper, outlet end of the column (4), and in that the heating element (23) is carried by and projects from said removable housing (3) such that it is immersed into the water of said tank (9) when said housing (3) is fitted into position on said base (2).

Description: Medical Breathing Apparatus This invention relates to breathing apparatus for medical purposes. It is known that humid air at around 90% relative humidity and a critical temperature of 43°C, when breathed by a patient for period of 15 to 20 minutes, is effective in rendering groups of viruses in the upper respiratory tract inactive, which results in the body being able to counteract colds, allergies, etc. efficiently and thereby reduce dramatically the patient's recovery time. The Applicant's co-pending U.K Patent Speci¬ fication No. 2192136, describes apparatus which incorporates an efficient temperature control arrangement by which air drawn through the apparatus is supplied to the user at or close to the critical humidity and temperature requirements. This apparatus has proved particularly successful in clinical trials conducted by the Medical Research Council. The object of the present invention is to provide a development of the apparatus described in our said co-pending Patent Specification which, compared with the various embodiments described therein, has further mainly constructional, advantages. According to this invention breathing apparatus of the kind having a water chamber in which a heating element is immersed, the temperature of said element being controlled so that air drawn over the heated water is maintained at or close to a required humidity and temperature at an outlet, the volume of the air passing through the apparatus being substantially greater than that required for breathing and being directed into a face mask connectable to the outlet which is formed with vents through which excess moist/heated air together with air exhaled by the user can pass to atmosphere, is characterised in that the casing for the apparatus is in two parts, comprising a base and a removable housing, in that the base accommodates a water tank and has a column extending upwards therefrom which defines an air path from the water tank, in that the face mask is connected to the upper, outlet end of the column, and in that the heating element is carried by and projects from said removable housing such that it is immersed into the water of said tank when said housing is fitted into position on said base. Preferably, the heating element is of the PTC (Positive Temperature Co-efficient) type and is surrounded by a shroud, which may be detachable, and which generally encloses said element, but provides openings near the top - of the shroud, the arrangement being such that, when the apparatus is not in use the heating element cannot be touched if the removable housing is removed, and when the apparatus is in use water at the required temperature tends to be concentrated within the shroud and across the water surface, thereby providing a reduced thermal mass and a consequent improvement in temperature control. The base and removable housing may be so shaped that, when fitted together, they provide a casing which tapers progressively to a small dimension in plan from its lower to its upper end, thereby providing stability to the apparatus in use, in which case a frontal part of the apparatus projects upwardly from the base and is inclined to the vertical away from the user, said frontal part preferably comprises front and side walls which are generally of U-cross-section, and the side walls thereof co-operate when fitted with a similarly inclined front wall of said removable housing to define said column. The removable housing may conveniently accommodate all the electrical/electronic components for the apparatus, which includes a fan and fan motor, said heating element, and a circuit arrangement therefor. The circuit arrangement may include provision for temperature control including a temperature sensor for monitoring the temperature of the moist/heated air being inhaled, which is fitted in the removable housing so as to project into said column at or close to its outlet. Conveniently, the water tank is removable from the base for easy filling and cleaning. In order that the invention may be readily understood, one embodiemnt of breathing apparatus in accordance therewith will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the apparatus, Figure 2 is a cross-sectional side view, on the line II-II of Figure 1, and Figure 3 is a section on the line III-III of Figure 2. Referring to Figure 1, it will be seen that the casing 1 is generally in two parts consisting of a base 2. and a removable housing 3, the split line being along the thickened line X-X (see also the chain dotted outline of the housing 3 in Figure 2). The front wall of the base (i.e the wall facing the user) includes a column 4 which projects upwardly, but is inclined to the vertical away from the user. The upper end of the column supports a face mask 5 via pivoted mountings 6, said face mask being provided with a series of slit openings 7, as described in our said co-pending Patent Specification No. 2192136. Referring to Figure 2, the base 2 has a continuous horizontal ledge 8 extending around its front and side walls (see also Figure 3) which support an open water tank 9, via a flange 10 extending around the top of said tank. The inclined column 4 is generally of U-cross section and the side walls 11 thereof (see also Figure 1) co-operate (when fitted) with a similarly inclined front wall 12 of - the removable housing 3 to define a path, denoted by arrows 13 r above the tank 9, for the flow (in use) of moist/heated air passed across the surface of water 14 contained in the tank, to the face mask 5. The removable housing 3 accommodates all the electrical/electronic components for the apparatus, which are fed from a suitable power supply via an electric cable 17 (see Figure 1). The components include a fan 18, which is rotatable within a volute casing 19 mounted on one (rearward facing) face of a support wall 20 extending vertically within the housing 3, a fan motor 21 supported on the other face of the wall 20 which is coupled to the fan via a drive shaft 22 extending through an opening in said wall, a PTC heating element 23, and, in this embodiment, a temperature control circuit board 24, and a temperature sensor 25. The circuit board 24 is also supported on said other face of the wall 20 and provides a control arrangement, which is designed:- (i) to provide a power supply to the PTC heating element 23, which projects from the lower wall of the housing 3 so that (with the housing fitted) , it is immersed in the water of the tank 9, (ii) to provide a regulated power supply to the motor 21 so that the fan 20 passes air drawn via slit openings 26 in the rear wall 15 of the housing 3 across the water in the tank 9 to the face mask 5 via air path 13 in a volume which (as described in our co-pending Patent Specification No. 2192136) is greater than that required for inhaling, (iii) to monitor the temperature of the air being breathed by the user via the sensor 35, which comprises a probe mounted on the wall 12 of the housing 3 so as to project into the air flow path 14 close to its upper outlet end, and (iv) to control the speed of the fan 18 to adjust the temperature of the air at the sensor probe position, as appropriate, to maintain the critical temperature As mentioned hereinbefore, the control arrangement would also include a timer and/or alarm circuit to warn, and preferably switch-off the apparatus automatically, after a pre-set time period, e.g 15 or 20 minutes. Also, the circuit includes an indicator light 30 to show when the power is on and which is preferably arranged to flash when the apparatus is initially switched on until a stable working condition is reached. The PTC heating element 23 is provided with a detachable shroud 27, which generally encloses said element, but provides openings 28 near the top of the shroud (see Figures 1 and 2) of a suitable plastics material which can withstand the temperature conditions, e.g. The shroud ensures that the user cannot directly touch the PTC element when the housing 3 is removed from the base 2, thereby ensuring safety from burns. However, it is has been found that temperature control of the air passing to the face mask 5 is effected more efficiently with such a shroud fitted, probably in view of the fact that the water in the tank 9 below the water surface is at a significantly lower temperature, due to the insulating effect of the plastics shroud. This leads to water at the required temperature being concentrated within the shroud and across the water surface, thereby providing a reduced thermal mass. Tests have shown that, in use, due to the inherent temperature stability of the PTC element and the further stability provided by the surrounding shroud, it is not essential to provide control means, including the sensor 25, to monitor and adjust the temperature of the air being inhaled, thus enabling significant cost savings to be achieved.

Claims: CLAIMS 1. Breathing apparatus of the kind having a water chamber in which a heating element is immersed, the temperature of said element being controlled so that air drawn over the heated water is maintained at or close to a required humidity and temperature at an outlet, the volume of the air passing through the apparatus being substantially greater than that required for breathing and being directed into a face mask connectable to the outlet which is formed with vents through which excess moist/heated air together with air exhaled by the user can pass to atmosphere, characterised in that the casing for the apparatus is in two parts, comprising a base and a removable housing, in that the base accommodates a water tank and has a column extending upwards therefrom which defines an air path from the water tank, in that the face mask is connected to the upper, outlet end of the column, and in that the heating element is carried by and projects from said removable housing such that it is immersed into the water of said tank when said housing is fitted into position on said base. 2. Apparatus according to Claim 1, characterised in that the heating element is a PCT element and is surrounded by a shroud, which generally encloses said element, but provides openings near the top of the shroud, the arrangement being such that, when the apparatus is not in use the heating element cannot be touched if the removable housing is removed, and when the apparatus is in use water at the required temperature tends to be concentrated within the shroud and across the water surface, thereby providing a reduced thermal mass and a consequent improvement in temperature control. 3. Apparatus according to Claim 1 or 2, characterised in that said base and removable housing are so shaped that, when fitted together, they provide a casing which- tapers progressively to a smaller dimension in plan from its lower to its upper end, thereby providing stability to the apparatus in use. 4. Apparatus according to Claim 1, 2 or 3, characterised in that a frontal part of the apparatus projects upwardly from the base is inclined to the vertical away from the user. 5. Apparatus according to Claim 4, characterised in that said frontal part comprises front and side walls which are generally of U-cross section and the side walls thereof co-operate when fitted with a similarly inclined front wall of said removable housing to define said - column. 6. Apparatus according to any one of Claims 1 to 5, characterised in that said removable housing accomodates all the electrical/electronic components for the apparatus, which includes a fan and fan motor, said heating element, and a circuit arrangement therefor. 7. Apparatus according to Claim 6, characterised in that the circuit arrangement has provision for temperature control and is operative to provide, a power supply to the heating element only when it is immersed in the water tank, a regulated power supply to the fan motor for controlling the speed of the far. so that it passes air in c the required volume in excess of that required for inhaling, and adjusts said speed as necessary to maintain the moist/heated air at its critical temperature. 8. Apparatus according to Claim 7, characterised in that said circuit arrangement includes a temperature 0 sensor which projects into said column at or close to its upper outlet end, which is operative to monitor the temperature of the moist/heated air being inhaled by the user via the sensor to initiate adjustment of the temperature if required. 9. Apparatus according to Claim 6, 7 or 8, Claims, characterised in that the circuit arrangement includes a timer and/or alarm circuit to provide a warning, and preferably switch-off the apparatus automatically, after a pre-set time period, and an indicator light to show when the power is on and which is arranged to flash until a stable working condition is reached.

Inventors: BEACHAM ALLAN, BEACHAM, ALLAN
Applicants: VIROTHERM LAB LTD, VIROTHERM LABORATORIES LTD.
Application year: 1989
Main classification: A61M15
IPC codes: A61M16