Surgery – Respiratory method or device – Means for mixing treating agent with respiratory gas
Reexamination Certificate
2000-05-25
2002-05-28
Weiss, John G. (Department: 3761)
Surgery
Respiratory method or device
Means for mixing treating agent with respiratory gas
C128S203120
Reexamination Certificate
active
06394085
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spacer for use with an inhaler for dispensing powdered medicament. Such a spacer may be used to ensure that an effective dose of a discrete amount of medicament is dispensed by the inhaler by reducing drug particles above a predetermined size from the administered dose.
2. Description of the Related Art
Conventionally dry powder inhalers comprise three parts: a reservoir for solid medicament either in a dry powder form or in a form suitable for the generation of dry powder for delivery on demand; a metering device for delivery of consistent doses of medicament from the reservoir; and an outlet.
A patient inhaling through the outlet receives a metered dose of the medicament. Metered dose inhalers allow the patient to administer an accurate does of medicament when required. This is particularly useful during a sudden occurrence of respiratory difficulty, such as an asthma attack.
One problem with dry powder inhalers is to ensure that an effective dose of the medicament is delivered to the patient's lungs. Dispensed medicament particles tend to separate according to size under the influence of gravity and air currents. Smaller particles, for example less than 5-6 &mgr;m in diameter, pass through the patient's oro-pharynx and enter the trachea, bronchi and lower airways where they are able to exert a therapeutic effect. Larger diameter particles are more likely to be deposited in the patient's oro-pharynx. Such oro-pharyngeal deposition is undesirable for a number of reasons. The patient may experience an unpleasant taste when particles alight on the mucosa. Furthermore the proportion of the dispensed dose inhaled which actually constitutes an effective dose is reduced. Moreover unwanted deposits of certain classes of compounds may cause undesirable side effects, eg a high incidence of Candida infections (“thrush”) has been reported in association with the administration of corticosteroids.
In pressurised metered dose inhalers the larger droplets formed in the aerosol cloud have been separated out by providing a “large volume spacer” to allow these larger droplets to impinge on the spacer wall, evaporate or fall to the floor of the spacer. Such a “large volume spacer” is unsuitable for use with a powder inhaler where the patient's inspirational air flow withdraws the dose from the inhaler.
Alternatively impact surfaces have been used in order to break up the larger particles of medicament. However this requires a tortuous air path. This results in a bulky spacer and increases the inhalation force required for effective drug delivery. It is undesirable to impose a further burden on a patient who is already experiencing respiratory problems.
SUMMARY OF THE INVENTION
The present invention seeks to provide a compact device which reduces the large particle dose without adversely affecting the fine particle dose and hence reduces the amount of oro-pharyngeal deposition of large medicament particles, while allowing self-administration of an effective dose without increasing the respiratory burden on the user.
According to a first aspect of the invention there is provided a powdered medicament inhaler spacer, comprising:
a body defining a chamber;
an inlet communicating with the chamber; and
an outlet communicating with the chamber, in which the chamber, inlet and outlet are adapted to provide a rotational flow path in use for an airstream passing from the inlet through the chamber to the outlet.
In preferred embodiments of the invention the body has a slender curved configuration.
The body may include an internal surface having the configuration of a closed curve. The body is preferably slender, that is of small width relative to its length or height. The body is preferably curved, that is the body may have the shape of a circle, ellipse, ovoid or other closed curve. Alternatively the body may be partially curved, that is with only a section of the body having a curved shape.
The chamber is preferably cylindrical, more preferably a circular cylinder having a horizontal radial axis in use and a continuous curved internal wall with two generally flat sides. Alternatively the cylinder may have the shape of an ellipse, ovoid or other closed curve.
The inlet and outlet communicate with the chamber such that an airstream with powdered medicament entrained in it may pass through the spacer, entering the chamber through the inlet and exiting the chamber through the outlet. The positions of the inlet and outlet are arranged within the chamber such that the airstream has to undergo at least some degree of rotational motion within the chamber in order to pass through the spacer. In preferred embodiments of the invention rotation through 360° occurs within the chamber. The curved form of the body together with the slender form of the body cooperate to constrain the possible flow paths of the airstream so that the only flow path possible is substantially rotational, ie the geometry of the spacer body reduces motion in a direction transverse to the body and induces rotational motion in direction parallel to the curvature of the body. The rotational motion in general of the medicament particles causes larger particles to be removed from the airstream.
One particular effect of the rotational motion of the powdered medicament particles in the airstream, is that it causes a centripetal force to act on the particles. The reaction of the centripetal force causes particles to move towards the surface of the chamber. The force acting on the particles is proportional to their mass and consequently the more massive particles, ie those with a greater dimension, experience a greater force and are urged towards the curved surface. As the particles impinge on the internal surface of the walls of the body they tend to adhere to it. In this manner particles above a certain size may be selectively removed from the airstream as it passes through the spacer. Hence, a dose of medicament with particles of the desired smaller sizes may be administered.
The curved body is arranged to induce rotational motion in the airstream without increasing the respiratory effort of the user. The curved body relies on its geometric form to induce a rotational flow path without imparting a sudden change in direction of the airstream flow path. Hence, larger particles are caused to adhere to the inner surface of the chamber. Fragmentation of larger particles may occur releasing further medicament of an inhalable size.
The curved body and chamber may have a transverse or radial axis and a lateral axis. Preferably the dimension of the transverse axis is less than the dimension of the lateral axis, more preferably half the dimension of the lateral axis. The transverse, ie radial dimension of the body is less than the lateral dimension of the body so that the flow path of the airstream is constrained to be substantially rotational. The sides of the body are disposed sufficiently close together so as to prevent substantial transverse flow, but are sufficiently spaced apart as to provide the chamber with a shape that does not significantly impede the passage of an airstream through the spacer so that the spacer does not impose a respiratory burden on the user.
The flow within the spacer may be observed in conventional manner using smoke or other opaque gaseous medicine within a spacer constructed of transparent material
Preferably, the inlet engages the curved body in a first direction and the outlet engages the body in a second direction and the first direction and the second direction lie in a common plane of the curved body which is perpendicular to the transverse axis. In this way, the inlet and outlet are arranged so that they are coplanar and their common plane is substantially perpendicular to the transverse axis of the body. Hence, only those particles undergoing rotational motion rather than transverse motion will be able to pass from the inlet to the outlet. The first direction and the second direction may be parallel.
In certa
Barney Brian David
Hardy John Graham
Mao Lei
Patel Vijay
Smalley Nick
Darby & Darby
Mitchell Teena
Norton healthcare Ltd.
Weiss John G.
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