Patent Description:
The present invention relates to an apparatus for delivering an aerosol, nebulized liquid, solid medicine, or a vapor to a patient's respiratory tract, and more particularly, to a nebulizer with improved performance.

Medical nebulizers for aerosolizing a liquid medicine that can be inhaled by a patient are well known devices commonly used for the treatment of certain conditions and diseases. Nebulizers have applications in treatments for conscious, spontaneously-breathing patients and for controlled ventilated patients.

In some nebulizers, a gas and a liquid are mixed together and directed against a baffle. As a result, the liquid is aerosolized, that is, the liquid is caused to form into small particles that are suspended in the air. This aerosol of the liquid can then be inhaled into a patient's respiratory tract. One way to mix the gas and liquid together in a nebulizer is to pass a quickly moving gas over a liquid orifice tip of a tube. The negative pressure created by the flow of pressurized gas is a factor that contributes to drawing the liquid out of the liquid orifice tip into the stream of gas and nebulize it.

Some of the considerations in the design and operation of nebulizers include regulation of dosages and maintenance of consistent aerosol particle size. In conventional nebulizer design, pressurized gas may entrain a liquid against a baffle on a continuous basis until the liquid in a reservoir is depleted. Continuous nebulization may result in a waste of aerosol during a patient's exhalation or during a delay between a patient's inhalation and exhalation. This effect may also complicate regulation of dosages because the amount of wasted aerosol may be difficult to quantify. Also, continuous nebulization may affect particle size and/or density. In addition, there may be excess medication lost to condensation on the nebulizer or mouthpiece during periods of non-inhalation. On the other hand, interrupted nebulization may also affect particle size and density as the nebulization is turned on and off.

There are several other considerations that relate to the effectiveness of nebulizer therapies. For example, it has been suggested that nebulization therapy is more effective when the generation of aerosol particles is relatively uniform, for example, producing particles of a particular size, particles within a range of sizes, and/or particles a substantial percentage of which are within a range of sizes. In addition, it may be advantageous for a nebulizer to be able to generate a large amount of aerosol quickly and uniformly so that a proper dosage can be administered.

A further consideration is the environment in which the nebulizer therapy may be administered. For example, a wall outlet at a hospital may supply pressurized gas for use with a nebulizer at a flow rate of <NUM> to <NUM> liters per minute in a range from <NUM> psi to <NUM> psi, whereas a home care compressor may supply pressurized gas for use with a nebulizer at a flow rate of <NUM>-<NUM> liters per minute and at pressures of <NUM> to <NUM> psi. Regardless of the environment in which the nebulizer therapy is administered, it is desirable to maintain and/or improve performance of nebulizers.

Additional considerations in the design and operation of nebulizers relate to the size and shape of the baffle, and the volume of liquid available for nebulization contained between the reservoir and the liquid orifice.

Accordingly, with these considerations taken into account, there is a need for an improved nebulizer.

The present disclosure provides an apparatus for delivering nebulized liquid or solid medication or vapor to a patient. According to one aspect, a nebulizer includes a housing having a chamber for holding an aerosol, an air outlet communicating with the chamber for permitting the aerosol to be withdrawn from the chamber, and a reservoir for holding a liquid to be aerosolized. The nebulizer also includes a liquid orifice located in the chamber, one or more liquid channels defined between the reservoir and the liquid orifice, the one or more liquid channels having a liquid volume, and a pressurized gas outlet located in the chamber adjacent to the liquid orifice. A baffle is located in the chamber and positioned relative to the pressurized gas outlet and the liquid outlet so as to divert pressurized gas from the pressurized gas outlet and over the liquid orifice. The baffle has a diverter surface area.

In another aspect, the liquid volume is at least <NUM><NUM>.

In another aspect, the diverter surface area is less than <NUM><NUM>.

In another aspect, the liquid volume is less than <NUM><NUM>.

In another aspect, the diverter surface area is greater than <NUM><NUM>.

In yet another aspect the liquid volume is between <NUM><NUM> and <NUM><NUM>.

In yet another aspect the diverter surface area is between <NUM><NUM> and <NUM><NUM>.

In a further aspect, the baffle has a disc-shaped diverter surface area. The disc-shaped diverter surface area may have a diameter between <NUM> and <NUM>.

In a further aspect, the baffle is shaped as a rib.

In another aspect, the baffle has a diverter surface area at least <NUM>% of a cross-sectional area of the liquid orifice.

In a different aspect, the liquid orifice is positioned at a distal end of a first nozzle extending in to the chamber, and the pressurized gas outlet is positioned at a distal end of a second nozzle extending in to the chamber through the first nozzle. The one or more liquid channels may be formed between the first nozzle and the second nozzle.

A nebulizer <NUM> is illustrated in <FIG>. The nebulizer <NUM> is a small volume nebulizer and includes a housing or container <NUM> defining an internal chamber <NUM>. The housing <NUM> is formed of a cylindrically-shaped side wall portion <NUM>, a top portion <NUM>, and a bottom portion <NUM>. The component parts of the housing <NUM> may be formed of separate, multiple pieces of material that are connected together by welding, adhesives, etc., or more preferably, some of the component parts may be formed together of a single piece of material formed by an injection molding process. For example, the bottom, and side portions <NUM> and <NUM> may be formed of separate pieces that are connected together, or preferably, these parts may be formed of one piece of molded plastic. Any of a number of plastics may be suitable, including polycarbonate, or polycarbonate blends. A cover <NUM> is removably mounted on the upper portion of the housing <NUM>, such as by means of a snap-on cover arrangement, twist-lock threads, screws or other types of fasteners. The housing <NUM> is approximately <NUM> in height and has a diameter of approximately <NUM>.

A lower portion <NUM> of the chamber <NUM> serves as a reservoir for holding a fluid <NUM> for nebulizing, such as a solution containing a medication. Located in the lower portion <NUM> of the housing <NUM> is a nozzle assembly <NUM>. Referring to <FIG>, the nozzle assembly <NUM> extends downward from the chamber <NUM> of the housing <NUM> to a fitting <NUM> located external of the chamber <NUM> on a bottom side <NUM> of the housing <NUM>. The fitting <NUM> is sized to connect to a supply <NUM> of pressurized gas provided through conventional tubing <NUM>. The pressurized gas may be supplied by any suitable source, such as a conventional gas supply used in hospitals, a pump, compressor, cartridge, canister, etc..

The nozzle assembly <NUM> is comprised of an outer tubular member <NUM>, and an inner tubular member <NUM>. The outer tubular member <NUM> has an inner passageway <NUM> that defines a liquid cylinder. The inner passageway <NUM> has a cross-sectional shape that is generally circular along the length of the inner passageway <NUM>. The inner tubular member <NUM>, or gas nozzle, has a passageway <NUM> that extends from an opening <NUM> in the bottom end of the fitting <NUM> to a gas outlet orifice <NUM> located at a top end <NUM> of the nozzle assembly <NUM>. The inner tubular member <NUM> is located in the inner passageway <NUM> of the outer tubular member <NUM>. The inner tubular member <NUM> is sized to slide into the inner passageway <NUM> of the outer tubular member <NUM> so that it is aligned therein. One or more liquid channels <NUM> are formed between the outer tubular member <NUM> and the inner tubular member <NUM>. The one or more liquid channels <NUM> may comprise an annular gap between the outer tubular member <NUM> and the inner tubular member <NUM>, and/or any cut-outs, passageways, slots, etc. formed between the inner tubular member <NUM> and the outer tubular member <NUM>, whether on the outer surface of the inner tubular member <NUM> (e.g., as one or more slots), on the inner surface of the outer tubular member <NUM> (e.g., as one or more slots), or any combination thereof (e.g., as an annular gap and slots). The one or more liquid channels <NUM> extend from a liquid reservoir opening <NUM> located at the reservoir <NUM> of the lower portion of the chamber <NUM> to a liquid outlet orifice <NUM> located at the top end <NUM> of the nozzle assembly <NUM>. The one or more liquid channels <NUM> serve to convey liquid medicine from the reservoir <NUM> at the bottom of the chamber <NUM> to the liquid outlet orifice <NUM> at the top of the nozzle assembly <NUM>. The one or more liquid channels <NUM> has a liquid volume or an equivalent liquid volume defined by the aggregate volume between the outer tubular member <NUM> and the inner tubular member <NUM> (including any gaps, passageways, or slots) extending from the reservoir opening <NUM> to the liquid outlet orifice <NUM>. As explained below, dimensions of the components defining the liquid volume may be selected to alter the performance of the nebulizer. In alternative embodiments, such as those shown and described herein, the outer tubular member <NUM> and the inner tubular member <NUM>, or portions thereof, may have other than a cylindrical shape, such as for example, a conical shape.

As shown in <FIG>, the liquid outlet orifice <NUM> is located at a top end of the liquid cylinder, or inner passageway <NUM> of the outer tubular member <NUM>. The liquid outlet orifice <NUM> has an annular shape defined by the top ends of the outer tubular member <NUM> and the inner tubular member <NUM> of the nozzle assembly <NUM>. The gas outlet orifice <NUM> has a circular shape and is located concentrically of the annular liquid orifice. In the present embodiment, the gas outlet orifice <NUM> is approximately <NUM> diameter and the liquid outlet orifice <NUM> has an outer diameter of approximately <NUM> to <NUM> and an inner diameter of approximately <NUM>. These dimensions are provided only by way of example and the nebulizer may be made in other sizes with different dimensions, as explained herein, in order to alter the performance of the nebulizer.

The top end <NUM> of the nozzle assembly <NUM> is formed by the top ends of the outer and inner tubular members <NUM> and <NUM>. In the present embodiment, the top end <NUM> is a generally flat surface having a diameter of approximately <NUM>. In alternative embodiments, the top end <NUM> may have an other-than-flat shape, for example, the inner tubular member <NUM> may be spaced above the outer tubular member <NUM> so that the liquid orifice <NUM> is located below the gas orifice <NUM>. Likewise, the diameter may be larger or smaller.

The nozzle assembly <NUM>, or a portion thereof, may be formed as part of the housing <NUM> as a single piece of material in an injection molding process. For example, the inner tubular member <NUM> may be formed of the same piece of injected molded plastic as the bottom of the housing <NUM>.

Referring again to <FIG>, the nebulizer <NUM> also includes a chimney assembly <NUM>. The chimney assembly <NUM> is located in an upper portion of the chamber <NUM> above the liquid reservoir <NUM>. The chimney assembly <NUM> includes a tubular body <NUM> that defines an internal passageway <NUM> that extends from an inlet opening <NUM> in the housing cover <NUM> to a chimney outlet opening at a bottom end of the tubular body <NUM>. Thus, the chimney assembly <NUM> serves as an inlet channel for ambient air to enter into the chamber <NUM>. The inlet opening <NUM> communicates with ambient air (through ports of an actuator button, as described below) and the chimney outlet opening communicates with the chamber <NUM>.

Located on the lower end of the chimney assembly <NUM> is a baffle <NUM>. The baffle <NUM> may be formed of the same piece of molded plastic material as the chimney <NUM> or alternatively, the baffle <NUM> may be formed of a separate piece of material that is attached by suitable means to the rest of the chimney assembly <NUM>. The baffle <NUM> is located directly opposite from the gas outlet orifice <NUM> and the liquid outlet orifice <NUM> located at the top end <NUM> of the nozzle assembly <NUM>. The baffle <NUM> is movable so that the distance between the baffle <NUM> and the top surface <NUM> of the nozzle assembly <NUM> can be varied. In the present embodiment, the baffle <NUM> has of a flat circular or disc shape with a diameter of approximately <NUM> so that it extends over both the gas and liquid orifices <NUM> and <NUM> out to approximately the edge of the top surface <NUM> of the nozzle assembly <NUM>. The baffle <NUM> therefore has a disc-shaped diverter surface area of approximately <NUM><NUM>. As used herein, diverter surface area refers to the surface area (whether flat, angled, or curved) of the baffle located opposite from the gas outlet orifice <NUM> and the liquid outlet orifice <NUM> that is provided for obstructing the flow of air and gas exiting the liquid outlet orifice and the gas outlet orifice. As explained below, the dimensions of the baffle disc may be selected to alter the performance of the nebulizer. In alternative embodiments, the baffle <NUM> may have an other-than circular shape such as, for example, a rib, or a cone, or a hemispherical shape. It is preferable that the baffle <NUM> have a size and shape such that the baffle <NUM> has a diverter surface area at least <NUM>% of the liquid outlet orifice <NUM>. In another embodiment the baffle and nozzle assembly remain fixed and are not movable such that the distance between the diverter surface of the baffle <NUM> and the top surface <NUM> of the nozzle assembly <NUM> cannot be varied. In yet another embodiment the baffle remains fixed and is not movable, but the nozzle assembly, or a portion thereof, is movable such that the distance between at least a portion of the nozzle assembly and the diverter surface of the baffle <NUM> can be varied.

The chimney assembly <NUM> is connected to the housing <NUM>. Specifically, the chimney assembly <NUM> is attached to the top portion <NUM> of the housing <NUM> by means of a membrane or diaphragm <NUM>. The membrane <NUM> is a ring-shaped piece of a flexible, resilient material, such as silicone rubber. An outer rim or bead of the membrane <NUM> is secured in a groove in the top portion <NUM> of the housing <NUM> and/or the cover <NUM>. An inner rim of the membrane <NUM> is secured in a slot formed by two parts of the chimney assembly <NUM>. The membrane <NUM> has a rolled cross-sectional profile as shown in <FIG>. This permits the membrane <NUM> to act as a rolling diaphragm. The membrane <NUM> permits limited movement of the chimney assembly <NUM>. The chimney assembly <NUM> is connected to the membrane <NUM> so that the membrane <NUM> biases the chimney assembly <NUM> away from the nozzle assembly <NUM> as shown in <FIG>. When installed in the manner shown in <FIG>, in the present embodiment, the bottom of the chimney assembly <NUM> is approximately <NUM> away from the top surface of the nozzle assembly <NUM>. In alternative embodiments, the bottom of the chimney assembly <NUM> may be closer or farther away from the top surface of the nozzle assembly <NUM>.

Located at the top end of the chimney assembly <NUM> is an actuator <NUM>. The actuator <NUM> connects to the tubular body <NUM> of the chimney assembly <NUM> and extends through the opening <NUM> at the top of the housing <NUM> in the cover <NUM>. The actuator <NUM> includes a closed top side <NUM> with one or more side opening ports <NUM>.

Located in the chamber <NUM> at the bottom end of the chimney assembly <NUM> is a bell-shaped cover <NUM>. The cover <NUM> extends from the opening at the bottom of the chimney passageway <NUM> outward toward the inside wall of the cylindrical portion <NUM> of the housing <NUM>. The cover <NUM> includes a horizontal portion <NUM> and a vertical portion <NUM> that extends downward from the horizontal portion <NUM> toward the top of the nozzle assembly <NUM>. The cover <NUM> has an open bottom side providing an air passageway around the bottom side of the cylindrical vertical wall <NUM>.

As mentioned above, the baffle <NUM> is movable relative to the nozzle assembly <NUM>. The present embodiment provides a means to limit the travel of the baffle relative to the nozzle assembly <NUM>. This may be accomplished in any of several suitable ways. In a present embodiment, the movement of the baffle <NUM> toward the nozzle assembly <NUM> is limited by one or more stop pins <NUM>. The stop pins <NUM> extend up from the bottom portion <NUM> of the housing. In a present embodiment, there are three stop pins. The top ends of the stop pins <NUM> are spaced away from the bottom end of the vertical wall <NUM> of the cover <NUM>. Because the chimney assembly <NUM> is movable vertically due to its connection to the housing <NUM> by means of the flexible membrane <NUM>, the stop pins <NUM> provide a lower limit to the movement of the chimney assembly <NUM>. In a present embodiment, the stop pins <NUM> are spaced so that when the lower edge of the vertical wall <NUM> of the cover <NUM> is brought into contact with the stop pins <NUM>, a space 'h' is provided between the baffle <NUM> and the upper surface <NUM> of the nozzle assembly <NUM>. In the present embodiment, the space 'h' is approximately between <NUM> and <NUM>, or more preferably approximately between <NUM> and <NUM>, and most preferably approximately <NUM>. In alternative embodiments, the space'h' may be larger or smaller.

In alternative embodiments, movement of the baffle <NUM> toward the nozzle assembly <NUM> may be limited by means other than stop pins. For example, if the housing were formed by an injection molding process, steps, shoulders, fins, or other structures, may be provided along the walls of the housing in order to limit the downward travel of the chimney and/or baffle.

Also located in the chamber <NUM> is a diverting ring <NUM>. The diverting ring <NUM> is located on the inner wall of the cylindrical portion <NUM> of the housing <NUM>. Specifically, the diverting ring <NUM> is positioned adjacent to the cover <NUM>. The diverting ring <NUM> is sized to define a gap <NUM> around the cover <NUM>. The diverting ring <NUM> serves to impede large droplets of liquid that might form on the inner wall of the housing <NUM> and divert large droplets back down into the reservoir <NUM> at the bottom of the housing <NUM>. In addition, the diverting ring <NUM> serves to provide a relatively tortuous path for the flow of aerosol particles from the lower portion of the chamber <NUM> to the upper portion. This tortuous path also serves to reduce the presence of larger particles and helps to make the particle size distribution more uniform.

As mentioned above, the bottom of the chamber <NUM> serves as a reservoir <NUM> for a liquid to be nebulized. In a present embodiment, the reservoir has a funnel-like shape to direct the liquid to be nebulized in a downward direction toward the inlet <NUM>. The reservoir portion of the chamber <NUM> is formed of at least two portions or stages. In a present embodiment, an upper portion <NUM> of the reservoir is relatively wide having a diameter approximately the same as that of the cylindrical portion <NUM> of the housing <NUM> (e.g. <NUM>). The upper portion <NUM> is relatively shallow (e.g. <NUM>-<NUM>). The upper portion <NUM> of the reservoir tapers in a funnel-like manner toward a lower portion <NUM> (or secondary well) of the reservoir. The lower portion <NUM> is relatively narrow, but relatively deep (e.g. <NUM>). The lower portion <NUM> of the reservoir is slightly wider (e.g. <NUM>) than the outer diameter of the nozzle assembly <NUM>. The opening <NUM> from which the liquid is drawn is located at the bottom of the lower portion <NUM> of the reservoir. In a present embodiment, the reservoir <NUM> also includes an intermediate portion <NUM> located between the upper portion <NUM> and the lower portion <NUM>. The intermediate portion <NUM> of the reservoir <NUM> has a height and a width between that of the upper and lower portions.

In the embodiment of the nebulizer shown in <FIG>, the relative sizes and dimensions of the upper, lower and intermediate portions of the reservoir <NUM> contribute to the generation of an aerosol wherein the aerosol particle size and output is relatively uniform overall. As described more below, the liquid in the reservoir <NUM> is drawn through the opening <NUM> and up the liquid channel <NUM> in part by the negative pressure caused by the flow of gas across the liquid orifice <NUM>. The suction force provided by the gas flow both draws the liquid up out of the reservoir to the top of the nozzle and entrains the liquid with a certain velocity in the air flow. As the liquid is nebulized, the surface level of the liquid in the reservoir goes down, thereby directly increasing the distance that the liquid has to be drawn up out of the reservoir to the orifice at the top of the nozzle. As the distance of the top of the nozzle over the liquid surface increases, more energy is required to draw the liquid up to the liquid orifice at the top of the nozzle assembly <NUM>. Assuming a relatively constant gas pressure, this increasing distance may have the effect of decreasing liquid flow through the liquid orifice which in turn may affect the uniformity of the aerosol particle size and rate.

The embodiment of the nebulizer in <FIG> reduces this possible adverse effect. With the embodiment of <FIG>, a relatively large portion of the liquid is stored in the upper portion <NUM> of the reservoir and a relatively smaller portion of the liquid is stored in the lower portion <NUM> of the reservoir. Since the large portion <NUM> of the reservoir is wide and relatively shallow, the surface level of the liquid in the reservoir changes relatively slightly as the liquid in this portion of the reservoir is drawn down. Therefore, there is little change in the energy needed to draw this amount of liquid up from the reservoir to the liquid orifice <NUM> as this portion of the liquid is depleted. When all the liquid in the upper portion <NUM> of the reservoir is nebulized, the remaining liquid in the lower portion <NUM> of the reservoir is drawn into the liquid channel <NUM> and the height of the top surface of the liquid falls rapidly. However, since the lower portion <NUM> of the reservoir is relatively narrow, it contains only a small portion of the liquid being nebulized so there is relatively little overall effect on aerosol particle size and output from this portion of the liquid.

The embodiment of the nebulizer shown in <FIG> is adapted for use by a spontaneously breathing patient, so the aerosol from the nebulizer is output to a mouthpiece or mask that can be used by the spontaneously breathing patient. Accordingly, located in an upper portion of the chamber <NUM> is an adapter <NUM> having a chamber outlet <NUM> that connects to a mouthpiece <NUM>. In alternative embodiments, the nebulizer may be used with ventilator systems and instead of the mouthpiece <NUM>, the adapter <NUM> would connect the outlet <NUM> to the ventilator circuit.

To operate the nebulizer <NUM>, a suitable amount of a liquid such as a medicine or water is placed in the reservoir of the chamber <NUM>. The liquid may be placed in the reservoir by first removing the cover <NUM>, membrane <NUM>, and chimney <NUM>, filling an appropriate amount of liquid into the reservoir, and replacing the cover <NUM>, membrane <NUM>, and chimney <NUM> onto the housing <NUM>. In a preferred embodiment, the cover, membrane and chimney are assembled together and would be removable together as a unit. Alternatively, the liquid may be placed into the reservoir through the mouthpiece <NUM>, or further, the nebulizer may be provided pre-filled with the appropriate amount of medicine from the manufacturer, or in yet another alternative, the nebulizer may be provided with a resealable fill port. The source of pressurized gas <NUM> is connected to the fitting <NUM>. The source of pressurized gas <NUM> may be an external source, for example, a hospital wall outlet that provides pressurized gas at a flow rate of <NUM> to <NUM> liters per minute in a range from <NUM> to <NUM> psi, or a home care compressor that provides gas a flow rate of <NUM> to <NUM> liters per minute and in a range of <NUM> to <NUM> psi. Gas is delivered through the passageway <NUM> and is expelled from the gas outlet orifice <NUM> into the chamber <NUM>. However, at this stage, prior to inhalation by the patient, the gas travels upward from the gas outlet orifice <NUM> and nebulization does not occur since the baffle <NUM> is in the non-nebulizing position. The membrane <NUM> holds the chimney assembly <NUM>, including the baffle <NUM>, away from the nozzle <NUM>. In one embodiment, when in the non-nebulizing position, the distance between the baffle <NUM> and the top of the nozzle is approximately <NUM>. At this distance, the gap between the baffle <NUM> and the nozzle <NUM> is such that the flow of gas does not create sufficient negative pressure over the liquid orifice <NUM> to draw out the liquid.

To generate an aerosol with the nebulizer, the patient places the mouthpiece <NUM> to his/her mouth. When the patient inhales, air is withdrawn from the chamber <NUM> reducing the pressure inside the housing <NUM>. The lower pressure in the chamber <NUM> causes the membrane <NUM> to flex drawing the chimney <NUM> down. The lower position of the chimney <NUM> is shown in <FIG>. Downward movement of the chimney <NUM> is limited by the stop pins <NUM>. When the stop pins <NUM> limit the downward movement of the chimney <NUM>, the baffle <NUM> its diverter surface area are spaced a predetermined distance 'h' from the top surface <NUM> of the nozzle assembly <NUM>. In one embodiment, the gap 'h' is approximately <NUM>. In alternative embodiments, the distance 'h' may be larger or smaller, as described herein, in order to alter the performance of the nebulizer.

The pressurized gas, which may be continuously injected into the nebulizer through the fitting <NUM>, is diverted sideways approximately <NUM> degrees by the baffle <NUM>. Since the gas outlet orifice <NUM>, baffle <NUM> and nozzle top <NUM> are generally circular, gas exiting the orifice <NUM> is dispersed evenly in an approximately <NUM> degrees or radial pattern. The liquid medicine in the reservoir is then drawn up the channel <NUM> and out of the liquid outlet orifice <NUM> in part by the negative pressure caused by the moving gas passing over the liquid outlet orifice. The liquid drawn into the diverted gas stream is aerosolized at least by the time it reaches the larger volume space of the chamber. In one embodiment, the liquid medicine drawn out of the liquid orifice <NUM> has little or no impaction against the baffle <NUM>. However, in alternative embodiments, the liquid drawn into the gas stream may be directed against the baffle <NUM>.

As the liquid is nebulized it travels into the chamber <NUM> along a path around the lower edge of the cover <NUM>. As the patient inhales, the nebulized liquid travels upward through the gap <NUM> between the cover <NUM> and the diverting ring <NUM>, and out through the mouthpiece <NUM> to the patient's respiratory tract.

When the patient ceases to inhale, the pressure in the chamber <NUM> rises. The biasing of the membrane <NUM> is again sufficient to move the chimney <NUM> upward, increasing the distance between the baffle <NUM> and the top surface <NUM> of the nozzle assembly <NUM>, and causing nebulization of the liquid to cease. In alternative embodiments, a spring, pneumatic valve, or other biasing device may be utilized, alone or in combination with each other and the membrane, to move the baffle <NUM> into a non-nebulizing position. Thus, the nebulizer automatically cycles aerosol generation in time with the breathing cycle of the patient.

If the patient exhales into the nebulizer, no nebulization occurs since the baffle <NUM> is in the non-nebulizing position due to the biasing of the membrane <NUM>. Upward travel of the chimney <NUM> is limited by the cover <NUM>.

During inhalation, some air flow may be provided through the nebulizer in a path through the chimney <NUM>. This air flow into the chamber <NUM> may be provided from ambient in a path provided through the ports <NUM>, the chimney inlet <NUM>, the chimney passageway <NUM>, and the chimney outlet. This air flow may continue during both inhalation when the chimney <NUM> is in the lower position and exhalation when the chimney is in the higher position. Alternatively, the air flow through the chimney <NUM> may be stopped or reduced during inhalation when the chimney <NUM> is in the lower position. Control of the airflow through the nebulizer during inhalation or exhalation may be effected by suitable selections of the dimensions of the chimney inlet <NUM>, the chimney outlet, the actuator ports <NUM>, the baffle ring <NUM>, and other components that affect airflow through the chamber, such as any filters.

In the embodiment described above, the membrane <NUM> provides an elastic triggering threshold that permits cyclical nebulization to occur that coincides with the breathing of the patient. This threshold is set to fall within normal human breathing parameters so that the baffle moves into and out of proximity with the nozzle top as a result of the patient's normal breathing. In one embodiment, this level may be approximately less than or equal to <NUM> of water.

It can be appreciated that the threshold may be established at different levels to account for different classes of patients. For example, if the nebulizer is designed to be used with infants or neonatals, the elastic threshold of the membrane may be lower than the threshold used for adults. Similarly, a different threshold may be used for geriatric patients. The nebulizer may be used also for veterinary applications, such as equine or canine. In veterinary applications, there may be a relatively wide range of thresholds related to the various sizes of animals. Nebulizers having suitably chosen operating thresholds can be designed for veterinary uses.

It is also recognized that the openings into the chamber, such as the opening <NUM>, may affect the operating threshold for nebulization. Thus, the operating threshold of the nebulizer may be made readily adjustable by making the actuator <NUM> adjustable. Alternatively, the operating threshold may be adjusted by selection of the size of the openings <NUM> and <NUM> into the chamber which would also control air entrainment. This would permit the user to adjust the thresholds, if desired. By appropriate adjustment of the operating thresholds, flow control through the nebulizer can be provided. For example, it may be desirable that the patient not inhale or exhale too quickly or too deeply. For adults, a suitable flow rate may be approximately <NUM>-<NUM> liters/minute. The openings into and out of the chamber may be suitably adjusted to provide for these rates.

The nebulizer may be operated manually instead of relying on the breath-actuated feature. To operate the nebulizer manually, the actuator <NUM> is pressed down toward the cover <NUM>. As mentioned above, the actuator <NUM> is connected to the chimney <NUM>. Pressing the actuator <NUM> brings the baffle <NUM> down into the nebulizing position close to the nozzle <NUM>. Release of the actuator <NUM> causes the chimney <NUM> to rise due to the biasing of the membrane <NUM> thereby causing nebulization to cease.

The breath actuation of the nebulizer is convenient and efficient. By cycling the nebulization of the liquid, the nebulizer can be more efficient thereby reducing the cost of the therapy.

An important advantage follows from the feature of this nebulizer that nebulization can be cycled so as to occur in coordination with a physiological cycle of the patient. Specifically, by nebulizing only during an inhalation, for example, the dosage of medication delivered to the patient can be more accurately delivered and monitored. This enables this embodiment of the nebulizer to provide for dosimetric medication delivery to an extent that has been otherwise unavailable. By limiting the medication delivery to the inhalation cycle of the patient, a dosimetric portion of the medication can be provided.

In addition, the nebulizer <NUM> provides for high output and uniform nebulization due to the arrangement of the gas and liquid orifices <NUM> and <NUM> relative to the baffle <NUM>. The annular configuration of the liquid orifice <NUM> relative to the gas orifice provides for aerosol generation in an approximately <NUM> degree direction. This enables a relatively high and uniform rate of nebulization.

In a present embodiment, the membrane <NUM> is biased to keep the chimney in an upper, non-nebulizing position except during inhalation. Thus, in the periods of time between inhalations and exhalations, or if the patient pauses and removes the mouthpiece, nebulizing does not take place. In alternative embodiments, the membrane <NUM> may bias the chimney downward so that the nebulizer generates an aerosol or nebula except during exhalation. This alternative may not be as efficient as the prior alternative, but may still provide significant advantages over nebulizers that generate aerosol continuously.

in further alternative embodiments of the nebulizer, the gas orifice <NUM>, the gas passageway <NUM>, or a portion thereof, may have a shape that modifies the force of the pressurized gas against the baffle <NUM>. For example, the gas orifice <NUM> may have a shape that facilitates the change of direction of the gas when it is directed against the baffle, so that the force of the gas would not move the baffle away during inhalation thereby helping to direct the gas out into the chamber. In other embodiments, the geometry may be varied to tailor gas force and flow.

As mentioned above, the membrane <NUM> serves as a biasing member that moves the baffle. Preferably, the membrane is constructed of a silicone rubber material. Other materials capable of repetitive flexing, compression or expansion in response to the force of inhaled or exhaled air, such as a spring, or elastic bellows, may also be used. The biasing member is constructed so that it will move the baffle a predetermined distance away from or toward the nozzle during the course of a patient's spontaneous or ventilated breathing.

In a present embodiment, the baffle moves up and down in response to the patient's breathing. Alternative embodiments contemplate various means of bringing or diverting the gas and liquid streams into proximity in a cyclical basis.

In alternative embodiments, for instance, instead of moving a baffle into proximity with a gas outlet, the liquid jet or orifice can be moved toward the gas jet or orifice, or is otherwise directed toward the gas jet or orifice, or vice versa. For example, as shown and described in <CIT>, particularly with reference to <FIG> and <FIG> in <CIT>, a nozzle cover consists of two portions. A first portion is fixed at the top of a gas nozzle, so that the pressurized gas outlet, baffle, and annular orifice of a fluid outlet are all fixedly positioned with respect to one another at a spacing suitable for nebulization. The second portion is attached to an actuator piston and is moveable a predetermined distance up and down the axis of the gas nozzle so that the annular orifice of the fluid inlet moves with the actuator piston. As with the previously described embodiments, one or more fluid pathways are defined by spacing between the gas nozzle and nozzle cover, grooves in the nozzle cover, grooves in the gas nozzle, or a combination of these options. In the non-actuating position, the second portion is separate from the first portion such that a gap of a predetermined distance exists between the two portions. As a result of the gap, the first portion of the nozzle cover does not contact the fluid reservoir and there is no continuous fluid pathway between the fluid orifices, in other words no pathway exists from the reservoir and fluid inlet to the fluid outlet, so that no fluid may reach the fluid outlet. In the actuating position, the second portion is moved up until it mates or abuts with the first portion. The two portions cooperate to form at least one continuous fluid pathway between the fluid outlet and the reservoir. The continuous fluid pathway permits the negative pressure over the fluid outlet to draw fluid from the reservoir and initiate nebulization.

In alternative embodiments, the entire nozzle <NUM> can move instead of the baffle, or alternatively, both the nozzle and the baffle can move. Also, in a present embodiment, the baffle movement is up and down, but in alternative embodiments, the movement can be side to side, rotating, or pivoting. Finally, in other embodiments, the baffle, orifices, nozzle, and other elements may all be fixed so that he nebulizer is a continuous nebulizer rather than a breath-actuated nebulizer.

In alternative embodiments of the nebulizer, the liquid orifice may have shapes other than annular. For example, the liquid orifice may be located aside the gas orifice. Alternatively, the liquid orifice may be formed of a series of orifices positioned aside or annularly around the gas orifice.

Further descriptions of some of the previously described nebulizers may be found in <CIT>; <CIT>; and, <CIT>. The concepts described herein may be applied to the foregoing U. Patents and to other nebulizers as described in <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>, as well as to commercially available nebulizers, including for example, the AEROECLIPSE® II breath-actuated nebulizer ("AEII" or "AEII BAN") available from Trudell Medical International of London, Canada.

Baffle disc diameter (i.e., diverter surface area) and liquid volume (i.e., the aggregate volume between the outer tubular member and the inner tubular member including channels, gaps, passageways, or slots) are key components to nebulizer performance. Varying the size of the baffle disc diameter and liquid volume can directly affect aerosol output rate, without negatively impacting particle size (e.g., Mass Median Aerodynamic Diameter, or "MMAD") and the range of particles respirable deep into the respiratory system (e.g., the percentage of aerosol particle population less than <NUM>, or "%<<NUM>"). With a smaller baffle disc diameter and a larger liquid volume, the aerosol output rate is shown to be greatly improved, especially when the nebulizer is utilized at lower air supply pressures, such as those seen on a home care compressor.

Testing has shown that a smaller baffle disc diameter provides a greater aerosol output rate than a larger baffle diameter. These results are unexpected and counterintuitive because normal expectations are that a larger vacuum would be provided by a larger baffle disc, and that the larger the baffle disc, the greater the pull on the liquid, thus resulting in a higher output rate. Normal expectations are also that a larger baffle disc would provide better aerosolization since the larger baffle offers more diverter surface area for break-up of liquid. Additionally, normal expectations are that a larger baffle provides more opportunity for particle impaction and aerosolization.

Testing has also shown that an increase in liquid volume, for example, by increasing liquid cylinder cross sectional area (i.e., by increasing the annular gap between the liquid cylinder and gas nozzle), or by adding additional channels or passageways or slots, will increase aerosol output rate. These results are also unexpected and counterintuitive because normal expectations are that a larger liquid cylinder cross-sectional area would require stronger negative pressure to draw up the liquid for aerosolization, and hence a larger baffle would be thought to be required for a larger liquid cylinder cross-sectional area. Normal expectations are also that a larger liquid cylinder cross-sectional area would result in larger residual volume.

Turning to <FIG>, a cross-sectional view of a nebulizer <NUM> is shown with components and dimensions representative of those found in the AEROECLIPSE® II breath-actuated nebulizer. The nebulizer <NUM> of <FIG> may be described as a nebulizer having a fixed baffle <NUM> and a liquid orifice <NUM> or portion thereof that is moveable, such as those described in <CIT>. In this embodiment, the nebulizer <NUM> has a baffle disc diameter of <NUM> (or a diverter surface area of <NUM><NUM>), a liquid outlet orifice <NUM> diameter of <NUM>, a liquid cylinder diameter of <NUM> at the top end 240a of the liquid cylinder <NUM>, a liquid cylinder diameter of <NUM> at the bottom end 240b of the liquid cylinder <NUM>, three additional liquid channels or slots <NUM> of <NUM> formed in the wall <NUM> of the liquid cylinder <NUM>, and a liquid gap <NUM> of <NUM> formed between the outer tubular member, or the liquid cylinder <NUM>, and the inner tubular member, or the gas nozzle <NUM>. This nebulizer <NUM> has an equivalent liquid volume of <NUM><NUM>.

<FIG> is a cross-sectional view of the nebulizer <NUM> of <FIG> with particular dimensions modified to improve performance of the nebulizer <NUM>. The dimensions shown in the embodiment of <FIG> are considered preferred dimensions in that they are believed to provide optimal performance of the nebulizer. In this embodiment, a nebulizer <NUM>' has a baffle <NUM>' with a baffle disc diameter of <NUM> (or a diverter surface area of <NUM><NUM>), a liquid outlet orifice <NUM>' diameter of <NUM>, a liquid cylinder diameter of Ø7. <NUM> at the top end 240a' of the liquid cylinder <NUM>, a liquid cylinder diameter of <NUM> at the bottom end 240b' of the liquid cylinder, no additional liquid channels or slots, and a liquid gap <NUM>' of <NUM> formed between the outer tubular member, or the liquid cylinder <NUM>, and the inner tubular member, or the gas nozzle <NUM>. This nebulizer has an equivalent liquid volume of <NUM><NUM>.

<FIG> is a cross-sectional side view of the <NUM> nebulizer of <FIG> showing ranges of particular dimensions intended to enhance performance of the nebulizer <NUM>. The ranges of dimensions shown in <FIG> are alternative dimensions that are intended to result in improved performance of the nebulizer. For example, a nebulizer <NUM>" may have a baffle <NUM>" with a baffle disc diameter of Ø1. <NUM> to <NUM> (or a diverter surface area of <NUM><NUM> to <NUM><NUM>), a liquid outlet orifice <NUM>" diameter of Ø2. <NUM> to <NUM>, a liquid cylinder diameter of Ø5. <NUM> to <NUM> at the top end 240a" of the liquid cylinder <NUM>, a liquid cylinder diameter of Ø6. <NUM> to Ø10. <NUM> at the bottom end 240b" of the liquid cylinder, no additional liquid channels or slots, and a liquid gap <NUM>" of <NUM> to <NUM> formed between the outer tubular member, or the liquid cylinder <NUM>, and the inner tubular member, or the gas nozzle <NUM>. This nebulizer may have a range of equivalent liquid volume of <NUM><NUM> to <NUM><NUM>.

<FIG> is cross-sectional side view of another embodiment of a nebulizer <NUM> shown with ranges of particular dimensions intended to enhance performance of the nebulizer <NUM>. The nebulizer <NUM> of <FIG> is like the nebulizer <NUM> of <FIG> in that it may be described as a nebulizer having a fixed baffle <NUM> and a liquid orifice <NUM> or portion thereof that is moveable, similar to those described in <CIT>. However, the nebulizer <NUM> of <FIG> has a baffle <NUM> in the shape of a rib having a diverter surface area that covers at least <NUM>% of the liquid outlet orifice <NUM>. This embodiment also has a liquid outlet orifice diameter of <NUM> to <NUM>, a liquid cylinder diameter of <NUM> to <NUM> at the top end 340a of the liquid cylinder <NUM>, a liquid cylinder diameter of <NUM> to <NUM> at the bottom end 340b of the liquid cylinder <NUM>, no additional liquid channels or slots, and a liquid gap of <NUM> to <NUM> formed between the outer tubular member, or the liquid cylinder <NUM>, and the inner tubular member, or the gas nozzle <NUM>. This nebulizer <NUM> may have a range of equivalent liquid volume of <NUM><NUM> to <NUM><NUM>.

<FIG> is a cross-sectional side view of another embodiment of a nebulizer <NUM> with ranges of particular dimensions intended to enhance performance of the nebulizer <NUM>. Specifically, the nebulizer of <FIG> may have a baffle <NUM> with a baffle disc diameter of Ø1. <NUM> to <NUM> (or a diverter surface area of <NUM><NUM> to <NUM><NUM>), a liquid outlet orifice <NUM> diameter of Ø2. <NUM> to Ø4. <NUM>, and one or more liquid channels <NUM> formed in the wall <NUM> of the liquid cylinder <NUM> of a quantity and size that results in an equivalent liquid volume of <NUM><NUM> to <NUM><NUM>. The nebulizer <NUM> of <FIG> omits the liquid gap formed between the outer tubular member, or the liquid cylinder <NUM>, and the inner tubular member, or the gas nozzle <NUM>.

<FIG> is a cross-sectional side view of another commercial nebulizer <NUM> modified with ranges of particular dimensions intended to enhance performance of the nebulizer <NUM>. The nebulizer <NUM> of <FIG> may be characterized as having a moveable baffle <NUM> and a fixed nozzle assembly <NUM>, such as those described in <CIT> and <CIT>. In this embodiment, the nebulizer <NUM> may have a moveable baffle disc diameter of Ø1. <NUM> to <NUM> (or a diverter surface area of <NUM><NUM> to <NUM><NUM>), a liquid outlet orifice <NUM> diameter of <NUM> to <NUM>, a liquid cylinder diameter of <NUM> to <NUM> at the top end 540a of the liquid cylinder <NUM>, a liquid cylinder diameter of <NUM> to <NUM> at the bottom end 540b of the liquid cylinder <NUM>, no additional liquid channels or slots, and a liquid gap <NUM> formed between the outer tubular member, or the liquid cylinder <NUM>, and the inner tubular member, or the gas nozzle <NUM>, such that the device has an equivalent liquid volume of <NUM><NUM> to <NUM><NUM>.

The combined effect of baffle size and liquid volume/liquid cylinder cross sectional area on aerosol output rate is shown in <FIG> at various air supply pressures. In <FIG>, an AEII BAN device modified with a baffle disc diameter of <NUM>, and with existing liquid volume/liquid channel dimensions, was filled with nebulizer solution (albuterol) and aerosolized for <NUM> minutes continuously (dial set to continuous mode) while an inhalation flow of <NUM> Ipm was applied. The drug was collected onto a filter and assayed. The total amount of drug collected in <NUM> minutes was then determined and divided in half to obtain the output per minute. This was done for air supply pressures of <NUM> psi, <NUM> psi, and <NUM> psi. Next, the baffle disc diameter of the AEII BAN was reduced to <NUM> and the cross-sectional area of the AEII BAN liquid cylinder increased by <NUM>%, which resulted in an increased liquid volume. This device combination was then tested using the <NUM>-minute continuous drug output test method described above. Results show that the reduced baffle disc diameter and the increased liquid volume/liquid cylinder cross-sectional area have greater aerosol performance = in this particular test, improving aerosol output rate at the lower air supply pressures of <NUM> psi and <NUM> psi by as much as <NUM>%, and by approximately <NUM>% at the higher air supply pressure of <NUM> psi.

In <FIG>, similar two-minute continuous drug output testing was conducted, but in this testing, the effect of baffle size alone on aerosol output rate was determined for given liquid cylinder cross-sectional areas. First, an AEII BAN device was modified with a small baffle diameter (<NUM>) and then a large baffle diameter (Ø3. <NUM>) and tested using the <NUM>-minute continuous drug output testing previously described. For the same liquid volume/liquid cylinder cross-sectional area, aerosol output rate was shown to decrease with an increase in baffle diameter. Next, the AEII BAN liquid cylinder cross sectional area was increased by <NUM>%. This larger liquid cylinder cross sectional area was then combined with the same two baffle diameter sizes of <NUM> and <NUM>. Again, <NUM>-minute continuous drug output test results showed a decrease in aerosol output rate with an increase in baffle diameter.

Further investigation into the effect of baffle size and liquid volume/liquid cylinder cross sectional area on aerosol output rate was conducted by testing various baffle sizes in combination with various liquid cylinder cross sectional areas under simulated breathing conditions. An ASL5000 Test Lung was set up for this testing with the following test parameters: Tidal Volume: <NUM>, I:E ratio <NUM>:<NUM>, BPM <NUM>. A <NUM> Ipm air supply was applied to the nebulizer as the driving gas. The following nebulizer combinations were tested:.

Each device was first particle size tested using a Malvern Spraytech Unit to obtain MMAD particle size data and %<<NUM>. Each nebulizer combination listed above was then filled with <NUM> of nebulizer solution and placed on the breathing simulator apparatus. The devices were tested with the dial set to continuous mode. A bacterial filter was placed at the nebulizer outlet to capture the aerosol. Each device was run until "sputter" and bacterial filters were changed every minute. Filters were assayed for total amount collected on each filter. Respirable amount was calculated by multiplying the total amount collected on the filter by the %<<NUM>. This equates to the respirable output per minute.

<FIG> shows the effect of baffle size on aerosol output rate for a preferred liquid volume/liquid cylinder cross sectional area of a <NUM>% increase in AEII liquid cylinder cross sectional area. Results show that for a nebulizer device with the same liquid cylinder cross sectional area, aerosol output rate improves with the smaller baffle diameter. In this particular test, aerosol output rate increased by approximately <NUM>% going from the larger <NUM> baffle to the smaller <NUM> baffle.

The effect of liquid volume/liquid cylinder cross sectional area on aerosol output rate can be seen in <FIG> and <FIG>. For a given baffle diameter, the cumulative respirable aerosol output is plotted over time (output rate) for the various liquid cylinder cross sectional areas tested. In <FIG>, the baseline device for comparison purposes was the current AEII BAN device. Results show that for a baffle size of <NUM>, aerosol output rate increases with an increase in liquid cylinder cross sectional area. In this particular test, aerosol output rate increased from the baseline device by <NUM>% to <NUM>% for increases in liquid cylinder cross sectional area of <NUM>% and <NUM>% respectively. An increase in aerosol output rate of approximately <NUM>% was seen with the increase in liquid cylinder cross sectional area of <NUM>%. Another important aspect seen from the test results is the decrease in delivery time. That is to say, delivery time decreases as the size of the liquid cylinder cross sectional area increases.

Increased aerosol output rate and decreased delivery time are significant from a therapeutic standpoint because it means more medication can be delivered quickly, for example, in the event of an asthmatic episode. It also means less treatment time for a patient - with more medication being delivered per minute, the patient can receive the required dosage in less time. This is important since a patient's time is valuable and many patients may forgo their treatment if the treatment time is too long. By improving the aerosol output rate and decreasing delivery time, patients may be more likely to complete their treatments, which may prevent asthmatic episodes, and as result, reduce trips to the hospital.

<FIG> shows the effect of liquid volume/liquid cylinder cross sectional area on aerosol output rate for a baffle disc diamter of Ø3. The results from <FIG> again show an increase in aerosol output rate with increase in liquid cylinder cross sectional area. The results also shows a decrease in aerosol output rate compared to <FIG>, where the only difference is the smaller baffle diameter size (<NUM>). Looking strictly at the effect of liqiud cylinder cross sectional area on the <NUM> baffle, output rate increased compared to the baseline device of this group (<NUM> Baffle/Current AEII BAN device) anywhere from <NUM>% to <NUM>% for the various sized liquid cylinder cross sectional areas. Comparing results to those in <FIG>, aerosol output rate for the larger baffle <NUM> decreased by <NUM>% to <NUM>% for increases in liquid cylinder cross sectional areas of <NUM>% and <NUM>% respectively, and <NUM>% for the increase in liquid cylinder cross sectional area of <NUM>%. Again, delivery time is shown to decrease with an increase in liquid channel cross sectional area relative to the baseline AEII device.

The effect of a small baffle size and liquid volume/liquid channel cross sectional area can also be seen on the aerosol output rate of another commercially available nebulizer. As shown in the cross-sectional views of <FIG>, another commercially available nebulizer <NUM> was tested along with several modified versions of that device. The nebulizer <NUM> of <FIG> may be described as having a fixed baffle <NUM> and a fixed nozzle cover <NUM> with a plurality of liquid channels <NUM> formed in the outer wall <NUM> of the air supply post or inner nozzle <NUM>. The nebulizer of <FIG> omits any liquid gap formed between the outer tubular member, or the liquid cylinder <NUM>, and the inner tubular member, or the gas nozzle <NUM>. The modified versions of that device <NUM>' involved an increase in the cross-sectional area of the liquid channels <NUM>' to obtain an overall <NUM>% increase in volume of the liquid channels <NUM>', as seen in <FIG>, and then decreasing the cross sectional area of the liquid channels <NUM>" to obtain an overall <NUM>% reduction in volume of the liquid channels <NUM>", as seen in the device <NUM>" of <FIG>. The liquid channels <NUM>, <NUM>', and <NUM>" of the nebulizers of <FIG> are compared in <FIG>.

Testing of these nebulizers was conducted on the ASL5000 breathing simulator, using the same parameters as previously described for the AEII nebulizer modifications discussed in <FIG> and <FIG>. Furthermore, a <NUM> Ipm air supply was provided to the nebulizer as the driving gas. Test results of the baseline nebulizer shown in <FIG> and modified versions shown in <FIG> and <FIG> are presented in <FIG>. These test results confirm that aerosol output rate can be affected by liquid channel cross sectional area (and hence liquid channel volume) - a small baffle diameter combined with a large liquid channel cross sectional area provides an increase in aerosol output rate. In the case of the commercially available nebulizer of <FIG>, increasing the liquid channel volume by <NUM>% resulted in an increase in aerosol output rate of approximately <NUM>%. Decreasing the liquid channel volume by <NUM>% resulted in a decrease in aerosol output rate of approximately <NUM>%. Also important to note, aerosol delivery time decreased with the increase in liquid channel volume and increased with the decrease in liquid channel volume. This is consistent with test results for the modified AEII nebulizer testing.

The results detailed herein are significant because they indicate that both baffle diameter and liquid volume/liquid cylinder cross sectional area impact aerosol output rate and aerosol delivery time, while not negatively affecting particle size. By combining a small baffle disc diameter with various sizes of liquid volume/liquid cylinder cross sectional area, the nebulizer aerosol output rate and delivery time can be optimized for maximum benefit to the end user. The nebulizer could be optimized for treatment by the patient at home or for treatment in a hospital, depending on the requirements. For example, the objective may be to provide a nebulizer treatment at home to an end user with a hectic daily life, and thus to provide a given amount of medication to the end user in as short a time as possible in order not to disrupt the end user's busy schedule. The nebulizer for this application could be a combination of a small baffle disc diameter (e.g., <NUM>) with a large liquid channel size (e.g., <NUM>% increase in AEII liquid cylinder cross sectional area). Alternatively, the nebulizer application may be treatment in a hospital for delivery of a medication requiring a longer delivery time (for instance due to drug potency). In this case, the nebulizer for this application may be a slightly larger baffle disc diameter (e.g., <NUM>) with a slightly smaller liquid channel size (e.g., <NUM>% increase in AEII liquid cylinder cross sectional area). In other words, depending on the patient requirements and the driving gas pressure to be utilized with the device (e.g., homecare compressor or hospital wall air supply), the appropriate combination of baffle disc diameter and liquid channel size could be selected in order to provide the most effective nebulizer treatment to the end user.

Claim 1:
A breath actuated nebulizer (<NUM>) automatically cycling generation of an aerosol in time with the breathing cycle of a patient comprising:
a housing (<NUM>) having a chamber (<NUM>) for holding the aerosol (see p. <NUM>, <NUM>st paragraph);
an air outlet communicating with the chamber for permitting the aerosol to be withdrawn from the chamber;
a reservoir (<NUM>) for holding a liquid to be aerosolized;
a liquid orifice (<NUM>) located in the chamber;
one or more liquid channels (<NUM>) defined between the reservoir and the liquid orifice, the one or more liquid channels having a liquid volume;
a pressurized gas outlet (<NUM>) located in the chamber adjacent to the liquid orifice and positioned to deliver a flow of pressurized gas into the chamber; and
a baffle (<NUM>) located in the chamber and positioned relative to the pressurized gas outlet and the liquid outlet so as to divert pressurized gas from the pressurized gas outlet and over the liquid orifice, the baffle having a diverter surface area
characterized in that the liquid volume is at least <NUM><NUM>, and
wherein the diverter surface area is less than <NUM><NUM>.