WO2000021602A1

WO2000021602A1 - Respiratory humidification chamber

Info

Publication number: WO2000021602A1
Application number: PCT/NZ1999/000172
Authority: WO
Inventors: Neil Donald Prime
Original assignee: Fisher & Paykel Limited
Priority date: 1998-10-13
Filing date: 1999-10-13
Publication date: 2000-04-20
Also published as: AU1084000A

Abstract

A method for adhering a plastic dome to a metallic base using an ultra-violet activated acrylic glue. The dome and the base together form a humidification chamber which holds a body of water which is heated through the metallic base such that gases passing through the top of the dome will be humidified. The humidification chamber is designed to be used in a breathing assistance apparatus in order to provide pressurised humidified gases to a user.

Description

RESPIRATORY HUMIDIFICATION CHAMBER

TECHNICAL FIELD

This invention relates to seals and more particularly though not solely to humidification apparatus in which a water tight seal between a plastics chamber and a metallic base is provided.

BACKGROUND ART

Humidification systems suitable for use in providing a humidified supply of gases to a patient in a medical environment usually include a humidification chamber which contains a volume of water with a gases space above the surface of the water through which a gases flow is passed. The humidification chamber is positioned atop a heat source so that water vapour is formed in the gases space and combined with the gases flow to the patient. An example of the aforementioned medical humidification system incorporating a humidification chamber may be seen in our United States patent numbers 4,913,140 and 5,445,143.

In order for efficient heat transfer to occur between the chamber and the heat source, the base of the chamber is formed from a highly heat conductive material such as Aluminium. The humidification chamber however is designed to retain heat and also to allow a user to easily be able to view the level of water within the chamber so that it may be refilled when necessary. Accordingly, the humidification chamber has been formed from plastics material. In order to form a watertight seal it has been necessary to form the base (which is usually circular) and chamber with special flanges and to then crimp the edge of the base over the flange of the chamber with a rubber gasket there between. It has been found that seals formed by the above existing process may eventually fail either due to the warm and moist environment and the long durations of on/off cycling which they are subjected to or because the crimp applied to the base is not sufficiently tight.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to provide a seal which will at least go some way towards overcoming the above-mentioned disadvantages or which will at least provide the public with a useful choice.

Accordingly, in a first aspect, the invention may broadly be said to consist in a humidification chamber adapted to hold a volume of water and to be used in a respiratory humidification system, said humidification chamber comprising: housing means, formed from a substantially plastics material adapted to hold substantially said volume of water, and having a peripheral edge surrounding an open side, a base, formed from a substantially metallic material and adapted for connection to said housing means thereby sealing off said open side, and adhesive means bonding said base and said housing means together around said peripheral edge thereby forming a watertight seal.

In a second aspect, the invention may broadly be said to consist in a method of sealing a metallic base to a plastics chamber, said method comprising the steps of: a) forming flanged surfaces on said base and said chamber, b) applying ultra-violet activated adhesive means to at least one of said flanged surfaces, c) joining said flanged surfaces together thereby forming a joint, d) applying external pressure on at least one of said flanged surfaces thereby compressing said joint, and e) activating said adhesive means by subj ecting said j oint to an ultra-violet light source. The invention consists in the foregoing and also envisages constructions of which the following gives examples.

BRIEF DESCRIPTION OF THE DRAWINGS

One preferred form of the present invention will now be described with reference to the accompanying drawings in which;

Figure 1 is a plan view of a humidification chamber according to the preferred embodiment of the present invention,

Figure 2 is an exploded cross-sectional front elevation of the humidification chamber of Figure 1 ,

Figure 3 is a block diagram showing the apparatus used to manufacture the present invention,

Figure 4 is a flowchart showing the process of manufacture, and Figure 5 is a schematic drawing of a respiratory humidification system incorporating the humidification chamber of Figure 1.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to the drawings, and in particular Figures 1 and 2 initially, a respiratory humidification chamber 1 is shown in accordance with the preferred form of the present invention. The respiratory humidification chamber 1 substantially comprises two parts, a chamber means or dome 2 and a base means or base 3. Dome 2 is preferably formed from a plastics material which is transparent or at least semi-transparent to allow the contents to be visible externally. It can be seen that dome 2 has a substantially inverted cup like shape (as shown in Figure 2) having a circular flange 8 protruding substantially perpendicularly to side wall 9.

Dome 2 is preferably provided with a gases inlet 4 and a gases outlet 5, both of which protrude from the upper surface 6 thereof. Dome 2 is also provided with a water inlet 7 which may further be provided with a valve mechanism to regulate the flow of water into the respiratory humidification chamber 1. We have found that a suitable plastics material from which the dome may be formed is a combination of general purpose styrene and K-resin in about equal amounts. The base 3 is substantially flat and "disk" shaped having a main supporting section 11 surrounded by a "raised" circular flange 10 protruding from the edge thereof substantially parallel to the main supporting section. A layer of adhesive means or glue 12 are applied between the flanges 8 and 10. As will be described below, it is necessary for base 3 to possess good thermal conductivity properties and we have found that a good material from which base 3 may be formed is anodised aluminium.

We have discovered that a good watertight seal can be formed between the dome 2 and base 3 when the adhesive means 12 are, for example, an ultra-violet light cured acrylic adhesive certified for use in medical applications. While a number of adhesives are recognised in the art as being suitable for use with rigid/flexible PVC and polycarbonate, they are not known for use with general purpose styrene. The adhesive used according to the preferred embodiment of the present invention typically contains the following ingredients (percentages are by weight):

- High boiling acrylate (between about 50% to about 55%)

- Aliphatic urethane acrylate oligomer (between about 20% to about 25%) - Modified acrylamide (between about 15% to about 20%)

- Photo initiator (between about 1% to about 3%)

- Substituted silane (between about 1% to about 3%).

Using the adhesive described above, the aluminium base 3 and the plastic dome 2 are joined about their respective flanges 10 and 8 at their periphery. The process illustrated in Figure 4 of bonding (using an apparatus shown in Figure 3), according to the preferred embodiment of the present invention is as follows:

(a) Dispense the adhesive onto the flange 10 of aluminium base 3; (b) Assemble the base 3 onto the plastic dome 2; (c) Using a clamp or press 50 apply a 1.5kg load onto the joint of the two flanges 8 and 10 resulting in a pressure of 6.8 kPa;

(d) Cure the glue joint under a 40mW/sqcm, 365nm light source at a range of 110mm for 10 seconds; (e) Release the joint from the 1.5kg load once the 10 second cure is complete. This results in a joint approximately of 25 microns when cured.

Samples of the bonded joint were tensile and fatigue tested to establish if the failure pressure limit for the chamber glued joint between the aluminium base and plastic chamber dome is greater than expected loads during use. The approximate pressure on the joint with a chamber pressure of 100 cm H₂0 is 0.043 N/mm². A chamber pressure of 100cm H₂0 is considered to be extreme for humidification chambers. Various types of joints were tested to simulate the complex stresses that would be exerted on the humidification chamber. Lap joints simulate any hoop or radial stress, butt/peel joints simulate the peeling action exerted by the chamber pressure acting the top of the plastic dome, and the fatigue test simulates the high fluctuating pressures seen in certain modes of ventilation.

Many types of adhesives are compromised when exposed to hot / wet / aging environments. The tested samples were pre-conditioned to allow for these factors. The test samples were aged in an environmental chamber then left in water at 66 degrees Celsius for 7 days. The results of the lap joint and butt/peel joint tests are shown in Table 1.

Table 1: Results of Joint Testing

Assuming an internal chamber pressure of 100cm H₂0 (lOkPa), the peel joint has a factor of safety (F.O.S) of 35. The lap joint's F.O.S is 110.

The fatigue test sample lasted at least 7 days (maximum duration on patient) when oscillated between pressures of 0 to 120 cmH₂0 @ 5 Hz , while under water at 66 degrees Celsius . Under these conditions the j oint was uncompromised at the end of the seven days. Since under normal conditions the maximum chamber pressure used in high frequency ventilation would be 40 cm H₂0, the F.O.S is 3. Assembled chambers were also life tested under severe operating conditions as a supplementary test. The chambers were tested for 30 days without any compromise of the glued joint. The joints were tested using the humidifier chamber test procedure specified in IS08185:1998 clause 11.6.1 and 11.6.2. This involves application of 8 kPa static pressure, before and after the test. To pass the test the leak rate must not exceed 10 ml/min.

With reference now to Figure 4, a respiratory humidification system is shown which incorporates the preferred form of respiratory humidification chamber 1 according to the present invention. In use, the respiratory humidification chamber 1, having been sealed as described above, is mounted upon the heater plate 13 of a respiratory humidifier 14. Humidification chamber 1 is provided with a volume of water 15, preferably supplied through water inlet 7 from an external source. Humidification chamber 1 may be provided with a float valve system such as that described in our United States patent number 5,445, 143 so that the water level within the chamber may be maintained at a desirable level. A gases supply or ventilator 18 provides a flow of gases (for example, oxygen or anaesthetic gases) to the gases inlet 4 of the humidification chamber 1. As the water within the chamber is heated it will release water vapour to the gases flow producing humidified gases at the gases outlet 5 which are carried to a patient 19 by an inspiratory conduit 21.

Respiratory humidifier 14 also includes control means (not shown) which are programmed to carry out a series of instructions which may include receiving input from a user as to a desirable heater plate 13 or water 15 temperature. Accordingly, temperature sensors may be provided to sense the temperature of the heater plate and temperature and/or flow sensors 16 and 17 may be positioned in the flow of gases exiting the humidification chamber to provide feedback to the controller. A heater wire 20 may be provided within inspiratory conduit 21 to eliminate or reduce the occurrence of condensation or "rain out" within the conduit.

Accordingly, at least in its preferred form, the present invention provides a reliable, water tight seal between a general purpose styrene dome and an aluminium base using a UV cured acrylic medically certified adhesive. We have found that the seal thus produced is suitable for use in the environment of a humidification chamber which is cyclically warm and substantially constantly wet. This provides a much improved method of sealing a humidification chamber than was known previously.

Claims

CLAIMS:

1. A humidification chamber adapted to hold a volume of water and to be used in a respiratory humidification system, said humidification chamber comprising: housing means, formed from a substantially plastics material adapted to hold substantially said volume of water, and having a peripheral edge surrounding an open side, abase, formed from a substantially metallic material and adapted for connection to said housing means thereby sealing off said open side, and adhesive means bonding said base and said housing means together around said peripheral edge thereby forming a watertight seal.

2. A humidification chamber as claimed in claim 1, wherein said plastics material comprises a mixture of general purpose styrene and K-Resin.

3. A humidification chamber as claimed in claims 1 or 2, wherein said plastics material comprises a mixture of approximately 50% general purpose styrene and approximately 50% K-Resin.

4. A humidification chamber as claimed in any one of claims 1 to 3 , wherein said metallic material comprises Aluminium.

5. A humidification chamber as claimed in any one of claims 1 to 4, wherein said metallic material comprises anodised Aluminium.

6. A humidification chamber as claimed in any one of claims 1 to 5, wherein said adhesive means comprise an ultra-violet light activated glue.

7. A humidification chamber as claimed in any one of claims 1 to 6, wherein said adhesive means comprises a mixture of high boiling acrylate, aliphatic urethane acrylate oligomer, modified acrylamide, photo initiator and substituted saline.

8. A humidification chamber as claimed in any one of claims 1 to 7, wherein said adhesive means comprises a mixture of between about 50% to about 55% high boiling acrylate, between about 20% to about 25% aliphatic urethane acrylate oligomer, between about 15% to about 20% modified acrylamide, between about 1 % to about 3% photo initiator and between about 1% to about 3% substituted saline.

9. A humidification chamber as claimed in any one of claims 6 to 8, wherein said adhesive means are activated by ultra-violet light having a wavelength of approximately 365 nm.

10. A humidification chamber as claimed in any one of claims 6 to 9, wherein said adhesive means are activated by ultra-violet light having an intensity of approximately 40mW/cm².

11. A humidification chamber as claimed in any one of claims 6 to 10, wherein said adhesive means are activated by ultra-violet light for a duration of approximately 10 seconds.

12. A humidification chamber as claimed in any one of claims 1 to 11, wherein said adhesive means when activated by ultra-violet light are of a thickness of approximately 25 microns.

13. A humidification chamber as claimed in any one of claims 1 to 12, wherein said periphery of said open side of said housing means is provided with a flange along its length and the periphery of said base is provided with a complimentary flange, said adhesive means bonding said housing means and said base together between said flanges.

14. A humidification chamber as claimed in any one of claims 1 to 13, wherein said housing means is substantially cup shaped having a substantially circular peripheral edge and said base is substantially disk shaped.

15. A method of sealing a metallic base to a plastics chamber, said method comprising the steps of: a) forming flanged surfaces on said base and said chamber, b) applying ultra-violet activated adhesive means to at least one of said flanged surfaces, c) joining said flanged surfaces together thereby forming a joint, d) applying external pressure on at least one of said flanges surface thereby compressing said joint, and e) activating said adhesive means by subjecting said joint to an ultra-violet light source.

16. A method according to claim 15, wherein said metallic base and said plastics chamber together form a humidification chamber adapted to be used in a respiratory system.

17. A method as claimed in claim 15 or claim 16, wherein said plastics material comprises a mixture of general purpose styrene and K-Resin.

18. A method as claimed in any one of claims 14 to 17, wherein said plastics material comprises a mixture of about 50% general purpose styrene and about 50% K- Resin.

19. A method as claimed in any one of claims 15 to 18, wherein said metallic material comprises aluminium.

20. A method as claimed in any one of claims 15 to 19, wherein said metallic material comprises anodised aluminium.

21. A method as claimed in any one of claims 15 to 20, wherein said step of applying ultra-violet activated adhesive means comprises applying a mixture of high boiling acrylate, aliphatic urethane acrylate oligomer, modified acrylamide, photo initiator and substituted saline.

22. A method as claimed in any one of claims 15 to 21 , wherein said step of applying ultra-violet activated adhesive means comprises applying a mixture of between about 50% to about 55% high boiling acrylate, between about 20% to about 25% aliphatic urethane acrylate oligomer, between about 15% to about 20% modified acrylamide, between about 1% to about 3% photo initiator and between about 1% to about 3% substituted saline.

23. A method as claimed in any one of claims 15 to 22, wherein said step of activating said adhesive means comprises subjecting said joint to ultra-violet light having a wavelength of about 365 nm.

24. A method as claimed in any one of claims 15 to 23, wherein said step of activating said adhesive means comprises subjecting said joint to ultra-violet light having an intensity of about 40mW/cm².

25. A method as claimed in any one of claims 15 to 24, wherein said step of activating said adhesive means comprises subjecting said joint to ultra-violet light for a duration of about 10 seconds.

26. A method as claimed in any one of claims 15 to 25, wherein said step of subj ecting said j oint to an ultra-violet light source comprises positioning an ultra-violet light source at approximately 110 mm from said point.

27. A method as claimed in any one of claims 15 to 25, wherein said step of applying pressure results in a pressure of approximately 6.8 kPa on said joint.

28. A humidification chamber substantially as herein described with reference to and as illustrated by the accompanying drawings.

29. A method of sealing a metallic base to a plastics chamber substantially as herein described with reference to and as illustrated by the accompanying drawings.