Surgery – Respiratory method or device – Means for mixing treating agent with respiratory gas
Patent
1998-02-09
2000-09-26
Weise, John G.
Surgery
Respiratory method or device
Means for mixing treating agent with respiratory gas
12820312, 12820323, A61M 1500, A61M 1508
Patent
active
061230707
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for making it easier to empty a metering chamber of a powder dispenser, and in particular of a powder inhaler.
The use of powder inhalers is now widespread, particularly in the pharmaceutical field, and requirements concerning performance, efficiency, and manufacturing cost has become very tight.
One of the main requirements is to guarantee the best possible reproducibility of the quantity of substance that is dispensed each time the inhaler is actuated. This is particularly crucial when the inhaler contains medication that must be dosed very accurately, as is particularly the case for medication against asthma.
Also, the quality of pulverization is likewise important in ensuring that the expelled dose of powder does not include any clumps of powder. Such clumps prevent the powder from diffusing properly in the lungs and consequently reduce the effectiveness of the product.
In general, powder inhalers comprise a metering chamber filled with powder, which metering chamber is emptied when the inhaler is actuated, either by a flow of compressed air, or else by a flow of air generated by the user inhaling. An example of one such known apparatus is disclosed, in particular, in document WO 93/18812, and is shown in part in FIGS. 1 to 3. FIGS. 1 to 3 are respectively a longitudinal section, a cross-section, and a horizontal section of a metering chamber 10 having an expulsion channel 20 passing therethrough extending to a mouthpiece 30 of the dispenser. The metering chamber 10 is filled with substance from a supply of the substance (not shown), and when the apparatus is in operation, a flow of air represented diagrammatically by arrows in FIGS. 1 and 3, passes along said expulsion channel 20 to empty the metering chamber 10 and bring the dose of substance to the mouthpiece 30 of the dispenser from which it is dispensed to the user.
To obtain good dose reproducibility, it is necessary both for the metering chamber to be refilled completely after each utilization, and also for it to be emptied completely each time the apparatus is actuated. If the metering chamber is not emptied completely, then the volume of the dose as expelled no longer corresponds to the prescribed dose, and the powder remaining in the metering chamber can form powder build-up zones that prevent good dose reproducibility.
In such an apparatus, expulsion of the powder dose, i.e. emptying of the metering chamber, is an operation that is very difficult to perform, and it depends on numerous parameters, including: medication to be dispensed; shape of the metering chamber; thus, as can be seen in particular in FIG. 2, the metering chamber 10 is generally of cross-sectional area that is greater than that of the expulsion channel 20; speed; and dimensions of the expulsion duct.
In known devices, as shown in FIGS. 1 to 3, the expulsion duct 20 is generally cylindrical, and the air flow matches the shape of the duct. Thus, when the air flow penetrates into the metering chamber 10 while it is filled with powder, the flow follows a trajectory that is substantially rectilinear between the inlet and the outlet of said metering chamber. Under such circumstances, particularly when the metering chamber is of large volume, the flow of air tends, initially, to "dig a tunnel" through the powder, i.e. to form a passage as shown in dashed lines in FIG. 3 extending directly from the inlet to the outlet of the metering chamber 10, with said passage corresponding substantially to an extension of the expulsion channel 20 through the metering chamber. In this way, only a portion of the powder contained in the metering chamber is expelled. Thereafter, in a second step, if the metering chamber is not too large, the air flow entrains powder situated around said "tunnel".
Although that arrangement has been found to be effective for metering chambers that are relatively small, it suffers from considerable drawbacks when large doses are to be delivered. Under such circumstances, a portion of the powder lying in side zones of the meter
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Bruna Pascal
Stradella Giuseppe
Martin Todd M.
Valois S.A.
Weise John G.
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