Electric resistance heating devices – Heating devices – Continuous flow type fluid heater
Patent
1998-07-06
2000-06-20
Leung, Philip H.
Electric resistance heating devices
Heating devices
Continuous flow type fluid heater
392478, 392485, 219536, F24H 110
Patent
active
060787309
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to respiratory humidifiers and more particularly though not solely to heated respiratory humidifier conduits used in the breathing circuits of respiratory humidification systems to provide humidified gases to a patient or other person in need of such gases and methods of constructing such humidifier conduits.
BACKGROUND ART
In order to supply gases, for example humidified gases, to a patient or other person in need of such gases, flexible conduits have been used both from a gases supply to the patient (inspiratory conduit) and from the patient back to the gases supply (expiratory conduit). When the supplied gas is humidified, it is desirable to minimise the amount of condensation (known as "rain out") occurring on the inner walls of the conduit as this condensation soon accumulates, requiring regular draining. Some existing respiratory humidifier conduits incorporate heating wires to heat the conduit walls in an attempt to reduce condensation and also to assist in the control of the temperature of the humidified gases being delivered to the patient.
An example of a respiratory humidifier conduit incorporating a heating wire is disclosed in our prior United Kingdom Patent Application published as GB2284356A on Jun. 7, 1995. The heating wire disclosed is a looped heating element with the two free ends of the loop emerging from one end of the conduit for connection to a source of alternating voltage on the humidifier. This form of heated conduit where the heating wire lies in a random path along the bottom of the conduit has the disadvantage that gases passing through the conduit are not uniformly heated across the width of the conduit. In addition, the random nature of the wire's distribution allows for localised regions of the conduit walls to be at a temperature sufficiently low so as to allow condensation (or "rain out") to occur while other areas are heated excessively.
Some humidifier conduits have a heating wire wound around the outside of the conduit in an attempt to evenly apply heat to the conduit wall (both around the conduit and along the length of the wall) to overcome the problem of condensation. Examples of externally wound heated humidifier conduit may be seen in U.S. Pat. No. 4,686,354 to the BOC Group Plc and German patent publication number DE4244493 to Heinz Eilentropp. Both of these configurations, however, require the power drawn by the heating element to be sufficient to transmit heat through the conduit walls and into the gases. Accordingly, the power drawn by the heater wire is excessive as is the temperature of the wire. In addition, as heat from the heater wire must first pass through the conduit wall, the time taken to heat the gases is excessive, and the temperature of the outer surface of the conduit could possibly be high enough to burn a patient or care giver.
DISCLOSURE OF THE INVENTION
It is, therefore, an object of the present invention to provide a heated gases transportation pathway which goes at least some way towards overcoming the above disadvantages or which will at least provide the industry with a useful choice.
Accordingly, in a first aspect, the invention consists in a heated gases transportation pathway for use in a ventilation system adapted to supply a gases flow within said gases transportation pathway:
a conduit of a predetermined length having an internal surface and a longitudinal axis,
a heating means of a predetermined length adapted to heat said gases flow and/or said conduit wherein said heating means is positioned within said conduit means and in said gases flow wherein said heating means are elastically flexible and are formed into a predetermined shape which circumscribes a volume which is a portion of the volume of said conduit.
In a further aspect the invention consists in a heated gases transportation pathway for use in a ventilation system which creates a gases flow comprising:
a conduit adapted to channel said gases flow,
a heating means adapted to, upon energisation, supply heat to said gases flow wi
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Cambridge Malcolm H
Huddart Brett J
Campbell Thor
Fisher & Paykel Limited
Leung Philip H.
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