"NEBULISER"

FIELD OF THE INVENTION The present invention relates to a nebuliser and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.

BACKGROUND OF THE INVENTION

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.

Nebulisers are widely employed in a number of applications, e.g. nebulisation of liquid fuel, moisturisation of air and for sterilisation purposes. One common application is in the medical field. Medical nebulisers provide an aerosol of medication for pulmonary delivery of drugs for the treatment of certain conditions and diseases. Nebulisers have applications for conscious, spontaneously-breathing patients and for controlled, ventilated patients. An important consideration in the design of medical nebulisers is the ability to prevent unwanted loss of nebulisable liquid from the nebulisation chamber. Most prior art devices have a direct line of access from the atmospheric air inlet to the nebulisation chamber, and if these devices are inadvertently knocked over then any drug that escapes the chamber is wasted and the user invariably suffers considerable inconvenience by coming into contact with the liquid, and cost since the liquid is typically relatively expensive. Furthermore, this also means that the electronics of the nebuliser may come into contact with liquid, which may irreparably damage the device. See for example,

U.S. Patent No.'s 6,357,671; 6,283,118, 3,901,443 and 5,429,302, and International PCT Publication No. WO 94/08727.

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the abovementioned prior art, or to provide a useful alternative.

DISCLOSURE OF THE INVENTION

In a first aspect the present invention provides a nebuliser, comprising: a nebulisation chamber having an air inlet, an outlet, a well adapted to contain a nebulisable liquid, an energy source operatively associated with said well for nebulising said nebulisable liquid, and at least one selective flow means for substantially preventing egress of nebulisable liquid from the chamber through said air inlet while still permitting sufficient ingress of air into the chamber. The selective flow means is provided on or in the air inlet. In one embodiment the selective flow means is in the form of a plurality of baffles. The baffles are preferably disposed in an overlapping relationship within the air inlet, and may be sufficiently numbered, sized and/or positioned such that air may pass relatively freely into the chamber but egress of nebulisable liquid from the chamber is substantially prevented. The baffles may also be sloped from the air inlet walls toward the nebulisation chamber such that any nebulised liquid impacting thereon is returned to the well for re-nebulisation. The free space between the baffles defines apertures which are sufficiently small such that the surface tension of the nebulisable liquid substantially prevents the egress of nebulisable liquid but sufficiently large to permit the ingress of air into the chamber. In related aspects the baffles are coated with a surface tension modifier for creating a substantially non-wetting surface thereon. In related embodiments the selective flow means is configured to provide a labyrinthine/circuitous

path in the air inlet. In further embodiments the selective flow means are adapted to substantially retain the nebulisable liquid within the nebulisation chamber if the nebuliser is rotated from its generally upright position. In other embodiments the selective flow means may be formed from a readily deformable elastomeric material. The term "selective flow means" as used herein is intended to refer to a device/apparatus/formation/barrier which simultaneously allows the flow of air through the inlet passage into the chamber whilst substantially preventing the egress of liquid. In other embodiments, for example, the Applicants contemplates a foraminous or multi- perforate plate having apertures of sufficient size, configuration and/or number such that air may pass therethrough and yet nebulisable liquids are substantially retained (within the nebulisation chamber). However, the skilled person will appreciate that the selective flow means may be embodied in other forms. It will also be appreciated that the selective flow means should not substantially restrict the passage of air through the chamber. For example, the air inlet should not be restricted to the point whereby the user is forced to draw excessively deep breaths to receive a dose of nebulised liquid, since this may affect the delivered dose. It will be appreciated that for the purposes herein the "air inlet" of the nebulisation chamber comprises the external aperture of the nebuliser and the conduit or tube which depends into the nebulisation chamber. The present Applicants have found that, unlike prior art devices, certain advantages arise in providing a selective flow means between the well and the air inlet of the nebulisation chamber. In most of the prior art, there is a direct unrestricted passage between the well containing the liquid drug and the air inlet to the chamber. Without wishing to be bound by theory, it is believed that this permits atmospheric air to proceed unhindered into and through the chamber where it entrains the nebulised liquid before being transported to the user via the outlet. However, such an arrangement has

drawbacks. For example, if the device is inverted or dropped the liquid drug contained in the chamber may inconveniently escape from the chamber via the air inlet passage. Arguably such a direct inlet passage also provides an avenue for contamination of the liquid drug. The Applicants have found that providing a selective flow means between the air inlet and drug well reduces the possibility of liquid drug escaping from the device whilst still enabling a sufficient flow rate of air into and through the chamber to entrain the nebulised liquid. Selective flow means in the form of baffles also assist in extending the life of the device and in its maintenance. The Applicants contemplate that the present invention is particularly suitable for the Nebuliser device as described in International PCT Application No. PCT/AU2006/001305, which is incorporated herein by reference.

According to a second aspect, the present invention provides a method of nebulising a nebulisable liquid, comprising the steps of: i. providing a nebulisation chamber having an air inlet, an outlet and a well adapted to contain a nebulisable liquid; ii. providing a nebulisable liquid contained within said well; iii. providing an energy source operatively associated with said well to nebulise said liquid; and iv. nebulising said nebulisable liquid, wherein said nebulisation chamber comprises at least one selective flow means for substantially preventing egress of nebulisable liquid from the chamber through said air inlet while still permitting sufficient ingress of air into the chamber.

According to a third aspect, the present invention provides a method of preventing loss of nebulisable liquid via an air inlet of a nebuliser, the nebuliser having a nebulisation chamber, an air inlet and an outlet for the nebulised liquid, the method

comprising: providing at least one selective flow means within the nebuliser for

substantially preventing egress of nebulisable liquid from the chamber through the air

inlet while still permitting sufficient ingress of air into the chamber. Preferably the selective flow means is provided within the air inlet.

An embodiment of the invention provides the energy source in the form of an ultrasonic transducer which is preferably formed of piezoelectric ceramic material. The

energy source may also include a curved energy transmission surface which is preferably parabolic.

The well may be operatively associated with the energy source by a contact

medium having a high energy transmission efficiency. Preferably the contact medium is

chosen from the group consisting of water, rubbery polymer, gel and oil, or mixtures thereof.

In preferred embodiments the nebulisable liquid is chosen from the group consisting of: a drug, a solution of a drug and a suspension of a drug. Preferably the

well may contain up to 8 mL of a nebulisable liquid.

Unless the context clearly requires otherwise, throughout the description and the

claims, the words 'comprise', 'comprising', and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the

sense of "including, but not limited to".

Other than in the operating examples, or where otherwise indicated, all numbers

expressing quantities of ingredients or reaction conditions used herein are to be

understood as modified in all instances by the term "about".

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by way of

example only, with reference to the accompanying drawings in which:

Figure 1 is a sectional side view of a nebuliser according to the present invention, shown prior to operation and charged with a nebulisable liquid; and

Figure 2 is a view similar to Figure 1 but showing the nebuliser rotated such that the nebulisable liquid is now undesirably contained in the air inlet passage with the selective flow means substantially preventing the unwanted loss of nebulisable liquid out from the air inlet.

PREFERRED EMBODIMENT OF THE INVENTION Referring to the drawings, the nebuliser 1 includes a nebulisation chamber 2 having a well 3 adapted to contain a nebulisable liquid 4 to be nebulised and an air inlet 5 and an outlet 6. Preferably, the liquid 4 is a drug solution 7. The well 3 is preferably disposed at the deepest part of the nebulisation chamber 2 and may contain any amount of drug according to the size of the nebuliser 1. However in the preferred embodiment the well contains up to 8 mL of liquid. An energy source in the form of an ultrasonic transducer 8 is operatively associated with the well 3 for nebulising the drug 7.

The air inlet 5 includes at least one selective flow means 8 for substantially preventing loss of nebulisable liquid 4 from the chamber 2 while still permitting sufficient ingress of air into the chamber 2. The selective flow means 9 is shown as a plurality of baffles 10 however it will be appreciated by those skilled in the art that other structures may be used for the selective flow means 9. Preferably the selective flow means 9 is configured to provide a labyrinthine or circuitous path in the air inlet 5.

The baffles 10 are preferably disposed in an overlapping relationship within the air inlet 4 and may be numbered, sized and/or positioned closely together such that air may pass substantially freely into the chamber 2 but egress of nebulisable liquid from the chamber 2 is substantially prevented. The free space between the baffles 10 defines apertures which are sufficiently small such that the surface tension of the nebulisable

liquid 4 substantially prevents the egress of nebulisable liquid 4 through the air inlet 5, as best shown in Figure 2. However, the apertures are sufficiently large to permit the ingress of air into the chamber 2. Also, the baffles 10 are preferably sloped from the air inlet 5 walls toward the nebulisation chamber 2 such that any nebulised liquid impacting thereon is returned to the well 3 for re-nebulisation. Further, the baffles 10 may be coated with a surface tension modifier for creating a substantially non- wetting/hydrophobic surface thereon.

It will also understood by persons skilled in the art that it is not essential that the selective flow means 9 completely prevents flow of liquid out of the nebuliser 1. Rather, it is intended to restrict the flow of the liquid to such an extent that when the nebuliser 1 is inverted, knocked over or rotated from its generally upright position, the flow of liquid out of the nebuliser 1 is substantially reduced such that the orientation of the nebuliser 1 can be corrected without loss of the entire volume of liquid contained in the nebuliser 1.

Another embodiment for example may be a single, or multiple tapered orifices. These orifices may be configured such that they permit ingress of air into the chamber but prevent or at least reduce liquid leaving the chamber. The selective flow means 8 may be formed from a readily deformable elastomeric material.

It will be appreciated that the illustrated nebuliser is effective, economical, convenient and simple to use. Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.