Surgery – Respiratory method or device – Means for mixing treating agent with respiratory gas
Reexamination Certificate
1997-09-04
2001-09-11
Lewis, Aaron J. (Department: 3761)
Surgery
Respiratory method or device
Means for mixing treating agent with respiratory gas
Reexamination Certificate
active
06286506
ABSTRACT:
BACKGROUND
The present invention relates to a device for inhalation of a pharmaceutically active substance comprising means for generating a negative pressure or vacuum and to a method by which any suitable substance may be prepared in a dispersed state.
Inhalable pharmaceutically active substances are generally used for the treatment of diseases in the bronchial and pulmonary area, such as asthma and chronic bronchitis. Various types of inhalation devices or apparatus are used for this purpose.
One type of inhalation device is the breath-actuated inhaler, particularly but not necessarily a dry powder inhaler, containing multiple doses of a medicament containing an active substance. The inhaler has a manoeuvring means comprising a manoeuvring element for loading one dose of the medicament to a dosing unit and providing said dose in a position for inhalation. An inhaler of the prescribed type is described in EP-A-0 069 715 and EP-A-0 237 507.
The function of this type of known device depends on the creation of an airflow through the inhalation device resulting from inhalation by the patient. The airflow causes the active substance to be moved from a release position in a dosing unit into the airflow in which it is dispersed. A break down of aggregated particles must also be achieved during inhalation, because aggregates always occur in powders having fine particles, especially finely divided powders of the type generally used for inhalation. A particularly advantageous inhaler of the above mentioned type is the dry-powder, breath-actuated, multi dose inhaler TURBUHALER®, generally described in the above mentioned EP-patents.
Some patients such as small children and elderly people with diseases in the bronchial area are not able to use breath-actuated inhalers as it can be hard or even impossible for these patients to achieve the necessary inhalation flow. Airflow needed is about 30-60 l/min and many patients such as small children and elderly people are not capable of producing the necessary inhalation flow. These patients have to use inhalers with pressurised gas, i.e. freon CFC). Such inhalers suffer from many known disadvantages, such as unwanted side effects both for the environment and the patients.
In order to facilitate the inhalation of pharmaceutically active substances which are administered by the use of pressurised metered dose inhalers, so called pMDI:s, it is known to provide dispersion chambers having a considerable volume, e.g. up to 2000 ml, into which the substance, with the pressurised gas, is dispersed. These devices are generally called “spacers” and a typical spacer is known from GB 1 565 029.
Inhalation devices including dispersion chambers have also been developed for breath-actuated, dry-powder inhalers of the above mentioned type. Such an inhalation device is described in EP-A-0 548 152. This device comprises a reservoir for the active substance (this can be part of a dry powder inhaler arranged inside the inhalation device) and a dispersion chamber. The dispersion chamber has a movable wall part which varies the volume of the dispersion chamber between minimum and maximum volumes so as to draw active substance into the dispersion chamber from the dry powder inhaler. The movement of the movable part is achieved by the movement of a piston which when lowered creates a negative pressure within the dispersion chamber. The active substance is thereby drawn out into the chamber. A patient may then inhale the dispersed substance in the dispersion chamber through a face mask or mouth piece. This device is complicated and difficult to use. Furthermore, contact with powder and the design of several mechanical parts make the function of the device less reliable.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an inhalation device including a dispersion chamber which can be used by patients having reduced ability and which can create the air flow necessary to lift a dose from a release position into an inhalation channel, disperse it in the air flow and achieve the required break up of aggregated particles when using a breath-actuated inhaler. Preferably, the device should be simple and reliable to activate for inhalation and to use. The device should preferably be light, robust and attractive to take with you, since patients, for example asthma sufferers, always have to have their devices available.
According to the present invention, there is provided an inhalation device for use with an inhaler, the inhaler being for providing a dose of a substance for inhalation, the device having:
a section for receiving the inhaler;
a dispersion chamber in fluid connection with said section; and
a suction chamber of variable internal volume and in fluid connection with said dispersion chamber; wherein
by increasing the internal volume of said suction chamber, a negative pressure is produced in said dispersion chamber, thereby drawing substance from the inhaler into the dispersion chamber for subsequent inhalation.
According to the present invention, there is also provided an inhalation device having:
an inhaler for providing a dose of a substance for inhalation;
a dispersion chamber in fluid connection with said inhaler; and
a suction chamber of variable internal volume and in fluid connection with said dispersion chamber; wherein
by increasing the internal volume of said suction chamber, a negative pressure is produced in said dispersion chamber, thereby drawing substance from the inhaler into the dispersion chamber for subsequent inhalation.
The significance of this is that the substance for inhalation does not come into contact with any parts of the suction chamber creating the negative pressure. Furthermore, the dispersion chamber may have fixed simple internal surfaces which minimize retention of substance. Preferably, the suction chamber displaces a smaller volume than the volume of the dispersion chamber and is connected to the dispersion chamber substantially at an opposite end to the connection with the inhaler. In this way, dispersed substance drawn into the dispersion chamber does not reach the connection to the suction chamber.
Further preferred features are described in the appended claims.
Thus, there may be provided an inhalation device which facilitates the use of especially a TURBUHALER® for patients presently having to use pressurised metered-dose inhalers.
The device according to the invention may be especially designed for patients who are not capable of using a breath actuated inhaler of the above mentioned type for the reason that they are not capable of creating the inhalation flow necessary to release and lift the dose of the substance into the inhalation channel and to the lungs.
It is also an object of the present invention to provide a method of preparing a substance in a dispersed state.
According to the present invention, there is also provided a method of preparing a substance in a dispersed state in a dispersion chamber by drawing the substance into the dispersion chamber from a dispenser, wherein a suction chamber of variable internal volume is provided in fluid connection with the dispersion chamber and the method includes the steps of:
increasing the internal volume of the suction chamber so as to produce a negative pressure in said dispersion chamber to thereby draw said substance from the dispenser into the dispersion chamber.
As mentioned above, inhalation devices, including those with expandable dispersion chambers, can include moveable parts which allow a substance to be sucked into a dispersion chamber. Of course, these parts may be operated manually with the force for filling the dispersion chamber being provided directly by the user. However, this force is preferably provided by a sprung device such that the user merely has to release the tension in the device. Unfortunately, however, due to the very nature of elasticity, the force provided by a spring decreases as the spring expands. Thus the gas flow into the dispersion chamber is much higher for the first part of the filling of the chamber.
Berg Elna
Jeppsson Magnus
Macandrew John
Revell William
Robertson Paul
Astra Aktiebolag
Fish & Richardson P.C.
Lewis Aaron J.
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