CA2303275C

CA2303275C - Breath actuated nebulizer with valve assembly having a relief piston

Info

Publication number: CA2303275C
Application number: CA002303275A
Authority: CA
Inventors: Rick Blacker; Alex M. Verdun
Original assignee: Trudell Medical International
Current assignee: Trudell Medical International
Priority date: 1997-08-29
Filing date: 1998-08-25
Publication date: 2004-11-16
Anticipated expiration: 2018-08-25
Also published as: AR016643A1; ZA987440B; DE69810119D1; EP1009459A1; AU8743698A; DE69810119T2; AU739756B2; US6450163B1; JP3564391B2; US6044841A; WO1999011310A1; JP2001514054A; CA2303275A1; EP1009459B1

Abstract

A breath actuated nebulizer for efficiently and reliably delivering aerosolized liquid to an inhaling patient is disclosed. The nebulizer includ es a valve assembly having an actuator piston for quickly responding to an inhalation and beginning the nebulization process, and a relief piston to lower the inhalation effort required of the inhaling patient. Also provided is a method of providing breath actuated nebulization including the steps of moving an actuator piston connected to a diverter so that the diverter reaches a nebulizing position during an initial period of inhalation, and moving a relief valve to allow a greater flow of air, and thereby reduce inhalation effort, after the initial period of inhalation.

Description

BREATH ACTUATED NEBULIZER WITH VALVE ASSEMBLY HAVING
A RELIEF PISTON

2 The present invention relates to a method and apparatus for delivering 3 an aerosol, nebulized liquid, solid medicine or a vapor to a patient's 4 respiratory tract. More particularly, the present invention relates to a breath actuated nebulizer with reduced resistance to a patient's inhalation.

7 Medical nebulizers that generate a fine spray or nebula of a liquid g medicine for inhalation by a patient are well-known devices commonly used g for the treatment of certain conditions and diseases. Nebulizers have applications for conscious, spontaneously-breathing patients and for 11 controlled, ventilated patients.
12 In some nebulizers, a gas and a liquid are mixed~together and directed 13 against a baffle. As a result, the liquid is aerosolized, that is, the liquid is 14 caused to form 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 16 mix the gas and liquid together in a nebulizer is to pass a quickly moving gas 17 over a liquid orifice tip of a tube. A negative pressure created by the flow of 18 pressurized gas is a factor that contributes to drawing liquid out of the liquid 1 g orifice into the stream of gas and nebulizing it.
Important considerations in the design of a nebulizer are the timing 21 and dosage regulation of the aerosolized medication. In some nebulizer 22 designs, a continuous stream of pressurized gas entrains the liquid against 23 the baffle to constantly generate aerosol particles until the liquid in a 24 reservoir is depleted. Continuous nebulization may result in a waste of aerosol during a patient's exhalation or during a delay between inhalation 1 and exhalation. The amount of wasted aerosol may be difficult to quantify 2 and some medication may be lost to condensation on the nebulizer or 3 mouthpiece during periods of non-inhalation. Nebulizers implementing a 4 timed or non-continuous nebulization may adversely affect particle size and density as the nebulization is turned on and off.
6 Effective and economical nebulizer therapy includes the ability to 7 quickly generate a large amount of aerosol within a predetermined particle 8 size range. An effective nebulizer preferably provides these features 9 synchronously with the inhalation of the patient. Additionally, it is desirable that a nebulizer have adequate sensitivity to quickly respond to an inhalation 11 while not adversely restricting the patient's inhalation. Further, an indication 12 that the nebulizer is responding to the patient's inhalation would be useful.
13 Accordingly, there is a need for an improved nebulizer having these 14 characteristics.

17 According to a first aspect of the invention, a nebulizer is provided 18 having a housing with a chamber for holding an aerosol. An air outlet is 19 connected to the chamber permitting the aerosol to be withdrawn from the chamber. A liquid orifice communicates with the chamber. A pressurized gas 21 inlet is positioned adjacent the liquid orifice and is also in communication with 22 the chamber. A diverter movably positioned in the chamber and relative to 23 the air inlet and liquid orifice is designed to divert pressurized gas from the 24 inlet and over the liquid orifice when the diverter is in a nebulizing position. A
valve assembly comprising an actuator piston and a relief piston are 26 positioned in the chamber. The actuator piston is connected to the diverter 27 and responsive to inhalation through the air outlet so that the diverter quickly 28 moves into the nebulizing position during the beginning of an inhalation.
The 29 relief piston is responsive to additional negative pressure in the chamber after the initial period of inhalation and is movable to allow increased air flow 31 into the chamber so that the effort necessary for a patient inhaling through SUBSTITUTE SHE~'t' (RULE 28) 1 the air outlet is maintained in a desired range. In one preferred embodiment, 2 a nebulization indicator attached to the actuator piston provides a visual cue 3 that nebulization has begun.
4 According to another aspect of the invention, a method of providing a patient with an aerosol flow of medicine includes the steps of providing a 6 nebulizer having an outlet for delivering of the aerosol to the patient, a 7 chamber, an actuator piston having a diverter mounted in the chamber, and a 8 relief piston connected to the actuator piston and inhaling air from the 9 chamber through the outlet. The actuator piston and diverter move from an initial position to a predetermined distance from a pressurized gas inlet in the 11 chamber. The diverter diverts pressurized gas injected into the chamber and 12 creates a negative pressure over a liquid outlet. The negative pressure 13 draws medication through the liquid outlet and begins nebulization. The relief 14 valve is then opened to permit greater air flow through the chamber after the diverter has moved to the predetermined distance from the pressurized gas 16 inlet and nebulization has begun.

19 FIG. 1 is a perspective view of a preferred embodiment of the nebulizer according to the present invention.
21 FIG. 2 is a cross-sectional view of the nebulizer of FIG. 1.
22 FIG. 3 is an exploded view of the nebulizer of FIG. 1.
23 FIG. 4 is a bottom view of a preferred nozzle cover for use in the 24 nebulizer of FIG. 1.
FIG. 5 is a top plan view of a preferred actuator piston used in the 26 nebulizer of FIG. 1.
27 FIG. 6 is a side elevational view of the actuator piston of F1G. 5.
28 FIG. 7 is a side elevational view a preferred relief piston for use in the 29 nebulizer of FIG. 1. .
FIG. 8 is a top plan view of the preferred relief valve of FIG. 7.

SUBSTITUTE SHEET (RULE 26) 1 FIG. 9 is a cross-sectional view of the nebulizer of FIG. 1 showing the 2 position of the pistons and diverter during an initial period of an inhalation.
3 FIG. 10 is a cross-sectional view of the nebulizer of FIG. 1 showing the 4 relief valve in an open position after the initial period of an inhalation.
6 DETAILEp DESCRIPTION OF THE

8 A preferred embodiment of a nebulizer 10 is shown in FIGS. 1 and 2.
9 The nebulizer 10 includes housing 12 having a cylindrical body 14, a top portion 16, and a bottom portion 18. An air outlet 20 extends from the 11 cylindrical body 14 of the housing 12. The air outlet communicates with air in 12 the chamber 22 defined by the inside of the housing 12. The component 13 parts of the housing 12 may be fomled of separate, multiple pieces of 14 material that are connected together by welding, adhesives, etc., or more preferably, some of the component parts may be formed together with a 16 single piece of material formed by an injection molding process. The housing 17 12 may be constructed from a plastic material such as polycarbonate or a 18 polycarbonate blend. As will be recognized by those of ordinary skill in the 19 art, any of a number of types of plastic may be used to construct these parts of the nebulizer.
21 As shown in FIG. 2, a pressurized gas inlet 24 extends into the 22 chamber 22 through the bottom portion 18 of the housing 12. The opening 23 25 of the pressurized gas inlet 24 is designed to connect with a standard vinyl 24 gas hose (not shown). Inside the chamber 22, the pressurized gas inlet 24 forms a nozzle 26 that tapers down to a pressurized gas orifice 28 having a 26 predetermined diameter. Preferably, the gas inlet 24 is coaxial with the 27 cylindrical body and extends through the bottom wall 30 of the chamber 22.
28 FIGS. 2 and 3 best show that a nozzle cover 32 removably fits over the 29 nozzle 26. The nozzle cover 32 is preferably a tapered tubular member having openings at either end. The nozzle cover 32 slides over the nozzle 26 31 of the pressurized gas inlet 24 to form at feast one passageway 34 between SUBSTITUTE SHEET (RULE 26) 1 an opening 36 located near the bottom wall 30 and an annular orifice 40.
2 The annular orifice 40 is defined by the gap between the inner diameter of 3 the tip 42 of the nozzle cover 32 and the outer diameter of the tip 44 of the 4 nozzle 26. To maintain the proper size of the opening 36 and position of the nozzle cover 32 over the nozzle 26, a retaining tab 46 on the inside of the 6 nozzle cover 32 is designed to cooperate with a ledge 48 formed near the tip 7 44 of the nozzle 26.
8 The lower portion of the chamber 22 is preferably used as a reservoir 9 38. The reservoir 38 at the bottom of the chamber 22 holds a fluid for nebulizing, such as a solution containing a medication. In the embodiment 11 shown in FIG. 2, the bottom wall 30 slopes down to the nozzle 26 so that 12 gravity urges the fluid in the reservoir 38 toward the opening 36. In one 13 embodiment, the cylindrical body 14 and bottom portion 18 of the housing are 14 constructed from a transparent plastic to allow medical personnel to monitor medication levels in the nebulizer 10. The passageway 34 guides fluid from 16 the reservoir 38 through the opening 36 to the annular or~ce 40.
17 Preferably, a plurality of passageways connect the annular orifice with 18 the fluid in the reservoir. Each passageway is formed by a slot on the inside 19 of the nozzle cover 32. The characteristics of the aerosol generated in the nebulizer, in addition to the mass output of the nebulizer, may be varied by 21 varying the size and number of passageways. As illustrated in F1G. 4, in one 22 preferred embodiment there are three passageways 34 each having a 23 circumferential width of approximately 20° and spaced evenly around the 24 nozzle cover 32. The radial width of each passageway 34 is defined by the depth of the slot in the nozzle cover 32. In the embodiment shown in FIG. 4, 26 the radial width of the passageways is a constant 0.02 inches from the 27 opening 36 by the bottom wall 30 to the annular orifice 40. Other 28 passageway dimensions and arrangements may be implemented to achieve 29 the desired aerosol size and density during nebulization.
The pressurized gas orifice 28 is preferably circular in shape and 31 concentrically aligned with the annular or~ce 40 connected to. the liquid SUBSTITUTE SHEET (RULE 2B) 1 passageways 34. in one preferred embodiment, the diameter of the 2 pressurized gas or~ce 28 is approximately 0.018 inches and the annular 3 orifice has an inner diameter of 0.080 inches and an outer diameter of 0.096 4 inches. The tip 42 of the nozzle cover and tip 44 of the nozzle are preferably flat surfaces. Preferably, the pressurized gas orifice is positioned flush with 6 the plane Qf the annular liquid orifice or extends up to 0.010 inches above the 7 plane of the annular liquid orifice 40. In other preferred embodiments, the 8 tips of the nozzle cover and nozzle 42, 44 may have non-planer shapes.

9 Additionally, although the tip of the nozzle 44 may extend more than 0.010 inches above the plane of the tip of the nozzle cover 42, it is most preferred 11 that the pressurized gas orifice not go below the liquid annular or~ce. The 12 relative heights of the tips 42, 44 may be adjusted to achieve the desired 13 nebulization characteristics.
14 The nozzle cover 32 also preferably includes a diverter guide 50 and spring support members 52. The diverter guide 50 has a hollow passageway 16 coaxialfy aligned with the pressurized gas orifice 28 and annular orifice 40.
17 The diverter guide 50 is formed by the opening in the center of the spring 18 support members 52 attached to the top portion of the nozzle cover 32 by 19 integrally formed arms 54.
On the opposite end of the nebulizer housing 12, the top portion 16 is 21 removably attachable to the cylindrical body 14. The top portion 16 includes 22 a retainer lid 56 detachably connected to a chimney section 58. An annular 23 rib 55 on the outside of the retainer lid 56 forms a removable snap-fit 24 connection with a receiving groove 57 on the inside of the chimney section 58. The chimney section 58 removably attaches to the inside of cylindrical 26 body 14, preferably with threads 59 designed to cooperate with a female 27 threaded area 61 in the housing 12. A seal, which may be in the form of an 28 integrally formed annular rib 63, protrudes from the chimney section 58 and 29 prevents air or nebulized medication from entering or exiting the chamber between the chimney section 58 and cylindrical body 14. A conical extension 31 65 of the chimney section 58 extends into the chamber 22 and down below SUBSTITUTE SHEET (RULE 26) 10 PC"T/IB98/013I6 1 the tip of the nozzle cover 32. The conical extension 65 and a secondary 2 diverter 67, or baffle, on the exterior of the conical extension preferably act to 3 remove undesirable larger particles from nebulized liquid in the chamber.
4 The retainer lid 56 and chimney 58 contain a valve assembly 60 for permitting controlled amounts of ambient air to enter into the chamber 22 6 during a patient's inhalation. As best shown in FIGS. 2-8, the valve assembly 7 60 includes an actuator piston 62 and a relief piston 64. The actuator piston 8 62 has a circumferential flange 66 attached to a coaxial body 68 extending 9 down info the chimney 58. The circumferential flange 66 of the actuator piston 62 covers the ambient air inlet and defines at least one, and preferably 11 a plurality of, vents or openings 70 for permitting ambient air to pass through.

12 The upturned rim 72 of the circumferential flange 66 preferably forms a seal 13 with the inside of the retainer lid 56. The seal formed by the rim 72 of the 14 flange and the retainer lid 56, in cooperation with the relief valve 64, prevents air from escaping the chamber 22 when a patient exhales into the air outlet 16 20. In order to permit movement of the actuator piston within the inner wall of 17 the retainer lid 56, there is preferably a small clearance between the outer 18 circumference 73 of the flange 66 and the inner wall of the retainer lid 56.
19 Because the response time of the actuator piston 62 is lengthened by increasing the clearance, the clearance is preferably kept to a minimum so 21 that the breath actuation action of the nebulizer maintains a fast response 22 time. .
23 The coaxial body 68 of the actuator piston 62 extends into the chimney 24 65 along the longitudinal axis of the nebulizer 10. The closed end of the coaxial body 68 defines a diverter 74 for diverting the flow of pressurized gas 26 emerging from the pressurized gas orifice 28. Preferably, the portion of the 27 coaxial body adjacent to the diverter 74 is slideably positioned in the diverter 28 guide 50 attached to the nozzle cover 32. In a preferred embodiment, the 29 diverter 74 has a flat surface having a predetermined area. The surface is also preferably aligned parallel to the surface of the tip of the nozzle 44 and 31 perpendicular to the direction of flow of pressurized gas through the SUBSTITUTE SHEET (RULE 28) 1 pressurized gas orifice 28. One suitable diverter 74 has a circular area with a 2 diameter of approximately 0.180 inches.
3 The relief piston 64 is coaxially and slideably mounted on the coaxial 4 body 68 of the actuator piston 62. As best shown in FIGS. 7 and 8, the relief piston 64 has a hollow bore 76 sized to slideably fit along a portion of the 6 coaxial body 68 of the actuator piston 62. The relief piston 64 also includes a 7 circumferential flange 78 having a diameter sufficient to cover openings 70 in 8 the flange 66 of the actuator piston 62. As explained in greater detail below, 9 the openings 70 in the flange 66 allow ambient air to be drawn into the chamber 22 from outside the nebuiizer 10 and out through the air outlet 20 11 during inhalation. The circumferential flange of the relief valve is preferably 12 ~ bowl-shaped so that the outer edge 80 of the flange 78 contacts and seals 13 against the circumferential flange 66 of the actuator piston when the relief 14 piston 64 is closed. Preferably, the relief piston 64 has a circumferential flange 78 having a smaller diameter than the circumferential flange 66 of the 16 actuator piston 62. The relief piston 64 also includes a plurality of travel 17 limiters 82 extending from the bottom portion of the relief piston 64 at a 18 predetermined radial distance from the bore 76.
19 A biasing member, such as a spring 84, frictionally fits around the exterior of the relief piston 64 adjacent to the bore 76 and rests against the 21 spring support members 52 attached to the nozzle cover 32. The biasing 22 member is designed to have a resistance to motion that is sufficiently strong 23 enough to hold the valve assembly closed until inhalation begins, yet 24 responsive enough to quickly react to negative pressures generated by inhalation. Preferably, a precision spring having a constant spring rate is 26 used as the biasing member. A suitable spring for use in a presently 27 preferred embodiment has a spring rate of 0.6 gmlmm.
28 Referring now to FIGS. 2, 9, and 10, the operation of the presently 29 preferred embodiment of a nebulizer 10 will be explained. FIG. 2 illustrates the nebulizer with the actuator and relief pistons 62, 64 fully closed. The 31 nebulizer maintains this configuration during exhalation. Although the patient SUBSTITUTE SHEET (RULE 26) 1 is exhaling, pressurized gas is continuously entering the chamber 22 via the 2 pressurized gas orifice 28. In this configuration, the diverter 74 is at a great 3 enough distance from the tip of the nozzle 44 such that the pressurized gas 4 does not initiate nebulization. The force of the spring 84 against the spring support member 52 on one end and against the relief piston 64 on the other 6 end holds,the relief piston 64 and actuator piston 62 closed so that no air 7 escapes from the chamber 22 through the retainer lid openings 86. When a 8 patient begins inhaling through the air outlet 20, the force of the inhalation 9 lowers the pressure in the chamber 22 and pulls the actuator piston 62 down.
More specifically, when the rate of air flow through the air outlet 20 exceeds 11 the rate of flow of pressurized gas constantly supplied to the nebulizer 10, a 12 negative pressure is created in the chamber 22.
13 Referring to FIG. 9, when the rate of airflow out the air outlet exceeds 14 the pressurized gas flow and the negative pressure on the valve assembly exceeds the force of the spring, the actuator piston 62 moves downward, the 16 spring 84 compresses and the diverter 74 on the end of the coaxial body 68 17 moves to a predetermined distance 'h' from the orifice 28 in the nozzle 26 18 appropriate for nebulization. Preferably, a retaining ridge 88 around the 19 coaxial body 68 of the actuator piston 62 has a greater diameter than the diameter of the diverter guide 50 so that the diverter 74 stops at the desired 21 distance 'h' from the tip of the nozzle 44. During this initial stage of 22 inhalation, the force of the.spring 84 against the relief piston 64 holds the 23 relief piston closed against the actuator piston 62. Thus, no air flows through 24 the openings 70 in the circumferential flange 66 of the actuator piston 62 allowing the actuator piston to respond quickly to begin nebulization at the 26 start of an inhalation.
27 As noted above, nebulization of a fluid in the reservoir 38 begins as 28 soon as the diverter 74 reaches the appropriate distance 'h' from the tip 44 of 29 the nozzle where the pressurized gas orifice 28 is located. Preferably 'h' is 0.045 inches. The pressurized gas, which may be oxygen, continuously 31 flowing from the pressurized gas orifice is now deflected radially outward from SU8ST1TUTE SHEET (RULE 2B) WO 99/11310 PC'GIB98J01326 1 the gas orifice in a 360° pattern by the deflector 74. The gas fans out over 2 the annular or~ce at a high velocity creating a Jow pressure zone over the 3 annular orifice. The tow pressure zone, along with a capillary effect, draws 4 the liquid from the reservoir 38 through the passageways 34 and into the stream of pressurized gas.
6 Thq liquid is aerosolized and drawn out the air outlet 20 through a 7 mouthpiece 98 (FIG. 3) and into the patient's respiratory system. To improve 8 the performance of the nebulizer in eliminating non-optimally sized particles, 9 the conical extension 65 of the chimney extends around and below the plane of the tip 44 of the nozzle. The conical extension acts to intercept oversized 11 particles entrained in the gas flow directed by the diverter 74. These 12 particles condense on the inside of the conical extension 67 and fall back into 13 the reservoir. The secondary diverter 67 also helps to decrease oversized 14 particles in the air inhaled through the air outlet 20. The secondary diverter 67 collects additional oversized particles and directs the ambient air down 16 into the chamber to take a more circuitous route through the aerosol and 17 chamber before it leaves the nebulizer. The flowpath within the chamber 22 18 insures that a significant amount of ambient air is entrained to limit the 19 particle density and, accordingly, reduce the chances of particle growth through accidental particle collisions.
21 As best shown in FIG. 10, the relief piston 64 separates from the 22 actuator piston 62 after the initial period of the patient's inhalation.
The 23 decrease in pressure in the chamber 22 caused by the continuing inhalation 24 of the patient puts a force on the relief piston 64 that overcomes the force of the spring 84 in the opposite direction. Ambient air from outside of the 26 nebuiizer 10 may now flow through the opening in the retainer lid 56 and 27 through the previously covered openings in the flange 70 of the actuator 28 piston 62. The air flow, shown by arrows in FIG. 10, moves down through the 29 conical extension 65 of the chimney 58 into the chamber 22. The travel limiters 82 extending from the relief piston 64 rest against a ledge 89 formed 31 in the chimney so that the ambient air path through the actuator piston 62 and SUBSTITUTE SHEET (RULE 2B) 1 around the perimeter of the relief piston is not cut off. When the patient 2 finishes an inhalation, the relief piston 64 moves back up against the actuator 3 piston 62 and the actuator piston 62 seals against the inside of the retainer 4 lid 56 as shown in FIG. 2. During exhalation, relief valve 100 on the mouthpiece 98 operates to direct exhalation away from the nebulizer. Any of 6 a number of commonly available relief valves may be used with the presently 7 preferred embodiment.
8 An advantage of the presently preferred device and method is that a 9 quick response time to a patient's inhalation is achieved while also providing for reduced resistance to the inhalation. In order to minimize the response 11 time, the nebufizer is designed to minimize the amount of air flow required to 12 move the actuator and begin nebulization. The air flow through the air outlet 13 needed to begin nebulization may be adjusted to the desired level by design 14 of the clearance between the outer circumference of the actuator piston flange and the inner circumference of the retainer lid, the spring force on the 16 relief piston, and the force of the pressurized gas against the diverter.
Using 17 a preferred embodiment of the nebulizer as set forth above, and assuming a 18 pressurized gas flow rate of 8 liters per minute (i.p.m.) at 40 to 50 pounds per 19 square inch (p.s.i.), the actuator piston will actuate and begin the nebulization process once the patient begins inhaling at a rate of approximately 16 to 17 21 Lp.m. (a negative pressure of approximately 0.5 cm to 1.0 cm water below 22 ambient). The response of the actuator piston may be modified by changing 23 the pressure of the pressurized gas introduced into the chamber.
24 Alternatively, the nebulizer may be constructed having a different flange to retainer lid clearance, a different actuator piston diameter and/or a different 26 spring strength.
27 Another feature of a preferred nebulizer is a nebulizing indicator, such 28 as a flag 90, that is visible to indicate when the diverter 74 is in position to 29 nebulize the liquid from the reservoir 38. As shown in FIGS. 2, 9, and 10, the flag 90 preferably frictionally fits into the open upper end of the actuator 31 piston 62 so that it moves synchronously with the diverter 74 and the actuator SUBSTITUTE SHEE1 (RULE 26) 1 piston 62. During exhalation (FIG. 2), the flag 90 rests against a housing 2 in the retainer lid 56. As soon as the diverter moves to a predetermined 3 distance from the pressurized gas orifice 28 on the nozzle 26, a visible 4 indicator 94 on the flag 90 is viewable through windows 96 in the housing 92.
The visible indicator 94 may be a colored section contrasting with the color of 6 the rest of the nebulizer 10. FIGS. 9 and 10 illustrate that the visible indicator 7 portion 94 of the flag 90 becomes visible as soon as inhalation begins and 8 remains visible as long as the diverter is in the predetermined position away 9 from the pressurized gas orifice 28. The entire flag 90 may be constructed of a colored material that contrasts with the color of the rest of the nebulizer 10.
11 As shown in the attached figures and described above, an improved 12 breath actuated nebulizer has been disclosed that is designed for fast-13 starting nebulization during an initial portion of an inhalation and that has a 14 relief piston to decrease the effort with which a patient needs to inhale through the nebulizing device. Additionally, a nebulization indicator has been 16 disclosed that permits simple visual verification of nebulization. Although the 17 embodiment shown illustrates a diverter that moves toward the pressurized 18 gas orifice, other components may be moved to create the required ratio of 19 distance between the gas orifice, liquid orifice and diverter. For example, the gas or liquid orifices may be movable in response to inhalation while the 21 diverter remains stationary. In another preferred embodiment, the biasing 22 member that flexes in response to the patient's breathing may be designed to 23 deactivate nebulization upon exhalation by moving the diverter and nozzle 24 apart during exhalation and continuously nebulizing during all other times.
It is intended that the foregoing detailed description be regarded as 26 illustrative rather than limiting, and that it be understood that the following 27 claims, including all equivalents, are intended to define the scope of this 28 invention.

SUBSTITUTE SHEET (RUL.E 26)

Claims

What is claimed is:

1. A nebulizer comprising:
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;
a liquid orifice in communication with the chamber;
a pressurized gas inlet adjacent the liquid orifice, the pressurized gas inlet in communication with the chamber;
a diverter movably positioned in the chamber and relative to the pressurized gas inlet and liquid orifice so as to divert pressurized gas from the pressurized gas inlet and over the liquid orifice when the diverter is in a nebulizing position; and a valve assembly comprising:
an actuator piston connected to the diverter and positioned in the chamber, the actuator piston responsive to an initial period of inhalation through the air outlet to move the diverter into the nebulizing position; and a relief piston located in the chamber, the relief piston responsive to additional negative pressure in the chamber after the initial period of inhalation and movable to allow increased air flow into the chamber, whereby the effort necessary for a patient inhaling through the air outlet is maintained in a desired range.

2. The nebulizer of claim 1, wherein the valve assembly moves the diverter to a non-nebulizing position during patient exhalation.

3. The nebulizer of claim 1 further comprising a nebulizing indicator visible outside of the chamber when the diverter is in the nebulizing position.

4. The nebulizer of claim 3, wherein the nebulizing indicator is attached to the actuator piston.

5. The nebulizer of claim 4, wherein the nebulizing indicator further comprises a colored indicator flag.

6. The nebulizer of claim 1 further comprising a biasing member in contact with the valve assembly.

7. The nebulizer of claim 6, wherein the biasing member comprises a spring.

8. The nebulizer of claim 1 wherein the actuator piston comprises an inlet cover for movably covering an ambient air inlet in the housing, the inlet cover having at least one vent and connected to a coaxial shaft.

9. The nebulizer of claim 8, wherein the relief piston is positioned relative to the actuator piston and is movably responsive to an increased negative pressure in the chamber after the initial inhalation.

10. The nebulizer of claim 8, wherein the relief piston is slidably mounted on the coaxial shaft of the actuator portion.

11. The nebulizer of claim 10, wherein a biasing member holds the relief piston against the actuator piston.

12. The nebulizer of claim 11, wherein the relief piston comprises a flange portion axially aligned with the inlet cover of the actuator piston, the flange portion sized to removably cover at least one vent on the inlet cover of the actuator piston.

13. A breath actuated nebulizer for providing an aerosol to an inhaling patient, the nebulizer comprising:
a housing having a chamber for holding the aerosol;
an air outlet communicating with the chamber for permitting the aerosol to be withdrawn from the chamber;

a liquid outlet located in the chamber;
a pressurized gas outlet located in the chamber adjacent to the liquid outlet;
means for generating the aerosol in the chamber from the liquid outlet during an inhalation through the air outlet, the means for generating the aerosol comprising a movable diverter; and means for maintaining or reducing an inhalation effort of the inhaling patient in a desired range after an initial period of inhalation, wherein the means for maintaining or reducing an inhalation effort is movable independently of the means for generating the aerosol and movable relative to the housing.

14. The nebulizer of claim 13, wherein the means for maintaining the inhalation effort comprise a relief piston responsive to a negative pressure threshold and wherein the relief piston is movable relative to the housing.

15. The nebulizer of claim 14, wherein a biasing member in contact with the relief piston determines the negative pressure threshold.

16. The nebulizer of claim 7 wherein the spring has a linear spring rate.

17. The nebulizer of claim 8 wherein the inlet cover of the actuator piston has a diameter and the diameter of the actuator piston is greater than the diameter of the relief piston.

18. The nebulizer of claim 6 wherein the relief piston is positioned between the actuator piston and the biasing member, whereby the biasing member biases the relief piston against the actuator piston.

19. The nebulizer of claim 1, further comprising a first nebulizing position wherein the diverter is a predetermined distance from the pressurized gas inlet and the relief piston forms a seal against the inlet cover of the actuator piston.

20. The nebulizer of claim 19 further comprising a second nebulizing position wherein the relief piston is spaced apart from the inlet cover of the actuator piston, whereby ambient air flows into the chamber.

21. A use of the nebulizer of any one of claims 1 to 20 for providing a user with an aerosol flow of a liquid.

22. The use of claim 21 wherein the user is a patient and the liquid comprises a medicine.