Surgery – Respiratory method or device – Means for mixing treating agent with respiratory gas
Patent
1998-03-26
1999-12-07
Weldon, Kevin
Surgery
Respiratory method or device
Means for mixing treating agent with respiratory gas
239433, A61G 1500
Patent
active
059965762
DESCRIPTION:
BRIEF SUMMARY
This application Ser. No. 09/043,679 is the National Stage of PCT/EP96/04153.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to atomising nozzles used for hand held sprayers such as so-called aerosols and pump type atomisers, intended for the application of liquid pharmaceutical products.
2. Description of the Related Art
Aerosol type sprayers are used throughout the world for dispensing a wide range of products, for example, hair lacquer, furniture polish, cleaners, paint, insect killers and medicaments. Until recently, chlorofluorocarbons (CFC's) were the most common of the propellant gases used in aerosols because they are inert, miscible with a wide range of products, are easily liquefied under low pressures, give a substantially constant product flow-rate, and can produce sprays of droplets having mean diameters in the range of 3 to over 100 micrometers. However, in the 1970's it was confirmed that CFC's were probably responsible for depleting the Earth's protective ozone layer, and in 1987, most countries signed the Montreal Protocol to phase out the use of CFC's and have since agreed to stop use of CFC's for non-essential applications by the end of 1995. One notable exemption to this deadline for cessation of use is in relation to metered dose inhalers (MDI's) for medicaments, which are regarded as an essential use of CFC's, but even this use of CFC's will eventually be phased out.
Gases such as air and nitrogen have the advantages of causing no environmental damage, being non-flammable and causing no ill effects if inhaled. Such gases can be used to propel liquid from a canister, but with a simple orifice or a swirl orifice very high pressures are required to produce a fine spray suitable for an MDI.
Other types of aerosol generators for delivery of liquid pharmaceutical products exist for research and hospital applications, such as nebulisers. However, these generally contain baffles to remove larger droplets and use high air flowrates so making them unsuitable for use in portable, convenient atomisers.
It is also possible to force liquid at high pressure through a very small hole (5-10 micrometers diameter) to produce droplets of about 5 micrometers diameter, but these methods are unsuitable or uneconomic for large scale manufacture, mainly because of the difficulty in making very small holes in a suitable material, and, to prevent blockage of the hole, the need for exceptional cleanliness in the manufacture of the parts, together with ultrafiltration of the fluid to be sprayed.
Many of the drugs used in the treatment of respiratory disorders are insoluble in vehicles such as water and are dispensed as suspensions. The drug particles are produced in a respirable size of 1-5 micrometers. Particles of this size tend to block the very small holes (5-10 micrometers) used by known devices.
For veterinary and some human vaccination applications, high pressure (125-500 bars) spring or gas operated pumps (so-called needle-less injectors) are in common use to inject a jet of drug through the skin ("intra-dermal injection") without the use of needles, and attachments are available to convert the jet to a spray for administering drugs to the nasal passages of large animals such as swine. However, the smallest droplet size obtainable is in the order of 40 micrometers, and the range of applications for these injectors is limited.
Compressed air atomisers such as air brushes and commercial paint sprayers consume large quantities of air, and to obtain droplets of 5 micrometers with water for example, a gas to liquid mass ratio of over 36:1 is required which is impractical for convenient, portable sprayers.
Spray nozzles in which a liquid is atomised by impingement of multiple jets of fluid on each other, e.g. air and liquid jets, are known. U.S. Pat. No. 5,385,304 describes an air assisted atomising spray nozzle in which a jet of liquid is atomised within a mixing chamber by the shearing action of several jets of air directed in substantially perpendicular relation to the liquid
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Glaxo Group Limited
Weldon Kevin
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