Abstract:
A delivery system includes a holding chamber with first, second and third openings, and independently moveable first, second and third flow control members. A delivery system includes a holding chamber and a flow control member including a flap pivotable from an at rest position in a direction toward an outlet of a user interface and away from an output end of the holding chamber in response to a pressure being applied thereto.

Description:
This application is a continuation of U.S. patent application Ser. No. 13/313,876, filed Dec. 7, 2011, now U.S. Pat. No. 8,550,067, which is a continuation of U.S. patent application Ser. No. 11/712,547, filed Feb. 28, 2007, now U.S. Pat. No. 8,074,642, which is a continuation of U.S. patent application Ser. No. 11/130,808, filed May 17, 2005, now U.S. Pat. No. 7,201,165, which is a continuation of U.S. patent application Ser. No. 10/431,325, filed May 7, 2003, now U.S. Pat. No. 6,904,908, which claims the benefit of U.S. Provisional Patent Application 60/382,227, filed May 21, 2002, the entire disclosures of which are hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a visual indicator for an aerosol medication delivery apparatus and system used for administering a dosage of a substance in aerosol form to a patient. 
     Discussion of Related Art 
     The use of an aerosol medication delivery apparatus and system to administer medication in aerosol form to a patient&#39;s lungs by inhalation (hereinafter “aerosol delivery system(s)”) is well known in the art. As used herein: the term “substance” includes, but is not limited to, any substance that has a therapeutic benefit, including, without limitation, any medication; the term “patient” includes humans and animals; and the term “aerosol delivery system(s)” includes pressurized metered-dose inhalers (pMDIs), pMDI add-on devices, such as holding chambers, devices including a chamber housing and integrated actuator suited for a pMDI canister, nebulizers and dry powder inhalers. Examples of such aerosol delivery systems are disclosed in U.S. Pat. Nos. 4,627,432, 5,582,162, 5,740,793, 5,816,240, 6,026,807, 6,039,042, 6,116,239, 6,293,279, 6,345,617, and 6,435,177, the entire contents of each of which are incorporated herein by reference. Conventional pMDIs typically have two components: 1) a canister component in which the medication particles and a propellant are stored under pressure in a suspension or solution form and 2) a receptacle component used to hold and actuate the canister and having a mouthpiece portion. The canister component typically includes a valved outlet from which the contents of the canister can be discharged. A substance is dispensed from the pMDI by applying a force on the canister component to push it into the receptacle component thereby opening the valved outlet and causing the medication particles to be conveyed from the valved outlet through the receptacle component and discharged from an outlet of the receptacle component. Upon discharge from the canister, the substance particles are “atomized” to form an aerosol. 
     In the case of pMDI holding chambers, the holding chambers typically include a chamber housing with a front end and a rear end. The mouthpiece portion of the pMDI receptacle is received in an elastomeric backpiece located at the rear end of the chamber housing. An example of such a backpiece is disclosed in U.S. Pat. No. 5,848,588, the entire contents of which are incorporated herein by reference. The front end of the chamber housing includes an inhalation valve or a containment baffle or both and an interface, such as an adapter, a mouthpiece and/or a mask. The interface can be coupled to the front end of the chamber housing or integrally molded to the front end of the chamber housing. Some holding chambers include an integrated receptacle for a pMDI canister thereby eliminating the need for a backpiece or other equivalent structure used to receive and hold the mouthpiece portion of a pMDI. 
     One problem that currently exists with many aerosol delivery systems is that there is a lack of a visual indication to alert a caregiver when a patient is inhaling. In the case of a pMDI used in conjunction with a holding chamber, for example, it is important for a caregiver to know if the patient is inhaling at a rate sufficient to open the inhalation valve to allow the aerosolized medication to exit the holding chamber. It is also important to know when the patient is inhaling in order to coordinate the actuation of the pMDI with inhalation. 
     The present invention proposes to overcome the above-described problem, and other problems as described further below, by using a visual indicator in an aerosol delivery system. Such a visual indicator is particularly helpful with patients who do not have established breathing patterns. These patients, such as infants and small children, generally have very low tidal volumes. 
     Some known holding chambers on the market maintain that it is possible to determine breathing patterns by looking through the chamber for the movement of the inhalation valve. This is difficult to do in the case of low tidal volumes when the valve will only move a minor amount. If the chamber has an accumulation of drug deposited on the walls then this further impedes the viewing. Several examples of such devices are discussed below. First, U.S. Pat. No. 5,385,140 discloses a holding chamber that has a crosscut valve with four petals that lift during inhalation. At lower tidal volumes the petals will lift a small amount, but this can be difficult to see since there are numerous supporting ribs directly in the line of sight. A second device is disclosed in U.S. Pat. No. 6,039,042 where a clear adapter is used to view breathing patterns by way of the valve. However, the inhalation portion of the valve that moves is directly in the drug pathway and has only slight movement at lower flow rates (approximately 20°). Note that the entire contents of U.S. Pat. Nos. 5,385,140 and 6,039,042 are incorporated herein by reference. 
     With some of the other devices on the market it is possible to view the exhalation portion of the breath, but this is not considered to be as important as seeing the inhalation portion. One such device is disclosed in U.S. Pat. No. 6,293,279, the entire contents of which are incorporated herein by reference. The device has a mask with an exhalation valve that moves during exhalation, but at the lower tidal volumes this movement is not obvious. 
     Another problem that occasionally occurs, when the interface includes a mask, is a poor seal between the patient&#39;s face and the mask. Such a poor seal may adversely affect the delivery of aerosolized medication to the patient. The use of the above-mentioned visual indicator would be helpful in alerting the caregiver to verify whether there is a poor seal between the patient&#39;s face and the mask and, if so, to readjust the mask on the patient&#39;s face to improve the seal. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention regards a delivery system that includes a chamber that contains a substance in an interior volume of space formed within said chamber and an opening that receives the substance located in said volume of space and introduces the substance to a downstream path upon which the substance primarily flows along. An interface that receives the substance from the opening, the interface has a viewing port that prevents substantially non-ambient atmosphere gases and substances from escaping therefrom and that allows visualization of an internal portion of the interface. A flow indicator is positioned within the interface so as to be viewed via the viewing port and is positioned so as to not substantially interfere with a flow of the substance along the path. 
     A second aspect of the present invention regards a method of determining whether a patient is inhaling or exhaling when using a delivery system, the method including dispensing a substance located within an interior volume of a delivery system so that the substance will primarily flow along a path within the delivery system after being dispensed. Observing a position of a flow indicator located within the delivery system and located so as not to substantially interfere with the substance flowing along the path. Determining whether a user of the delivery system is inhaling from the delivery system based on the observed position of the flow indicator. 
     A third aspect of the present invention regards a flow indicating system that includes a conduit that contains a substance, wherein the conduit defines a path along which the substance primarily flows and a viewing port attached to the conduit and the viewing port that prevents substantially non-ambient atmosphere gases and substances from escaping therefrom and allows visualization of an internal space defined by the viewing port. A flow indicator that is positioned within the conduit so as to be viewed via the viewing port and is positioned so as to not to substantially interfere with a flow of the substance along the path. 
     Each aspect of the present invention provides the advantage of assisting either the patient or a third party caregiver to determine when the patient is inhaling when using an aerosol delivery system so that the patient or third party caregiver can be alerted to possible causes affecting inhalation, such as an improper seal between the patient&#39;s face and the aerosol delivery system&#39;s interface, such as a mask. 
     Each aspect of the present invention provides the advantage of allowing a user or caregiver to observe when inhalation has begun so that the drug can be properly administered. 
     The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of an aerosol delivery system in accordance with the present invention; 
         FIG. 2  is a perspective and partially transparent view of the aerosol delivery system of  FIG. 1 ; 
         FIG. 3  is a side cross-sectional view of the aerosol delivery system of  FIG. 1 ; 
         FIG. 4  is a perspective exploded view of the aerosol delivery system of  FIG. 1 ; 
         FIG. 5  is a front perspective view of an embodiment of an adapter according to the present invention to be used with the aerosol delivery system of  FIG. 1 ; 
         FIG. 6  is a rear perspective view of the adapter of  FIG. 5 ; 
         FIG. 7  is a front view of the adapter of  FIG. 5 ; 
         FIG. 8  is a rear view of the adapter of  FIG. 5 ; 
         FIG. 9  is a cross-sectional view of the adapter of  FIG. 5  taken along line  9 - 9  of  FIG. 7 ; 
         FIG. 10  is a cross-sectional view of the adapter of  FIG. 5  taken along line  10 - 10  of  FIG. 7 ; 
         FIG. 11  is a cross-sectional view of the adapter of  FIG. 5  taken along line  11 - 11  of  FIG. 8 ; 
         FIG. 12  is a front perspective view of a second embodiment of an adapter according to the present invention to be used with the aerosol delivery system of  FIG. 1 ; 
         FIG. 13  is a rear perspective view of the adapter of  FIG. 12 ; 
         FIG. 14  is a front view of the adapter of  FIG. 12 ; 
         FIG. 15  is a side view of the adapter of  FIG. 12 ; 
         FIG. 16  is a front perspective view of an embodiment of a valve according to the present invention to be used with the aerosol delivery apparatus of  FIG. 1 ; 
         FIG. 17  is a rear perspective view of the valve of  FIG. 16 ; 
         FIG. 18  is a front view of the valve of  FIG. 16 ; 
         FIG. 19  is a rear view of the valve of  FIG. 16 ; 
         FIG. 20  is a cross-sectional view of the valve of  FIG. 16  taken along line  20 - 20  of  FIG. 18 ; 
         FIG. 21  is a cross-sectional view of the valve of  FIG. 16  taken along line  21 - 21  of  FIG. 20 ; 
         FIG. 22  is a front perspective view of a second embodiment of a valve according to the present invention to be used with the aerosol delivery apparatus of  FIG. 1 ; 
         FIG. 23  is a rear perspective view of the valve of  FIG. 22 ; 
         FIG. 24  is a front view of the valve of  FIG. 22 ; 
         FIG. 25  is a perspective view of an embodiment of a retaining disc according to the present invention to be used with the aerosol delivery system of  FIG. 1 ; 
         FIG. 26  is a side-view of the retaining disc of  FIG. 25 ; 
         FIG. 27  is a side cross-sectional view of an embodiment of an aerosol delivery system according to the present invention taken along line  27 - 27  of  FIG. 28  that can be used with the aerosol delivery system of  FIG. 1 ; 
         FIG. 28  is a front view of the aerosol delivery system of  FIG. 27 ; 
         FIG. 29  is an enlarged portion of the circled area of the aerosol delivery system of  FIG. 27 ; 
         FIG. 30  is a side and partially transparent view of the aerosol delivery system of  FIG. 1  showing exhalation and inhalation paths; 
         FIG. 31  is a side and partially transparent view of a portion of the aerosol delivery system of  FIG. 1  showing a flow indicator at a rest position; 
         FIG. 32  is a side-cross sectional view of the aerosol medication delivery system of  FIG. 1  showing a flow indicator at a rest position; 
         FIG. 33  is a side and partially transparent view of a portion of the aerosol medication delivery system of  FIG. 1  showing a flow indicator at an inhalation position; 
         FIG. 34  is a side-cross sectional view of the aerosol delivery system of  FIG. 1  showing a flow indicator at an inhalation position; 
         FIG. 35  shows a perspective and exploded view of a second embodiment of an aerosol delivery system according to the present invention; 
         FIG. 36  shows a perspective and exploded view of a third embodiment of an aerosol delivery system according to the present invention; 
         FIG. 37  shows a perspective view of a fourth embodiment of an aerosol delivery system according to the present invention; 
         FIG. 38  shows a perspective, exploded view of an embodiment of a dry powder inhaler delivery system according to the present invention; 
         FIG. 39  shows a perspective view of the dry powder inhaler delivery system of  FIG. 38 ; 
         FIG. 40  shows a perspective view of an embodiment of a nebulizer delivery system according to the present invention; 
         FIG. 41  shows a perspective, exploded view of an embodiment of a holding chamber and adapter according to the present invention to be used with the nebulizer delivery system of  FIG. 40 ; and 
         FIG. 42  shows a perspective view of the holding chamber and adapter of  FIG. 41 ; 
         FIG. 43  shows a rear view of an alternative embodiment of an adapter; and 
         FIG. 44  shows a retainer releasably connected to the adapter shown in  FIG. 43 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1-11, 16-21 and 25-29  show an embodiment of an aerosol delivery system  100 . The system  100  includes a holding chamber or conduit  102 , an interface  104 , a retaining disc  116 , an inhalation valve  132  and a source of a substance, such as a pMDI canister  106 , attached to the rear end of the holding chamber  102 . 
     As shown in  FIGS. 1-4 and 27-34 , the holding chamber  102  includes a chamber housing  108  that has a generally cylindrical cross-sectional shape that defines an interior volume of space for receipt therein of aerosolized medication from the pMDI  106 . A front end of the chamber housing  108  includes a dome-shaped head piece  110  that includes a central circular opening  112  that is in fluid communication with the interior volume of space of the chamber housing  108 . The opening  112  defines the periphery of a flow path as it exits the opening. The head piece  110  further includes a plurality of engagement tabs  113 , whose function will be described below. A rear end of the chamber housing  108  is attached to a detachable and flexible backpiece  114  that includes an opening (not shown) suited to receive the mouthpiece portion of the pMDI receptacle that houses the pMDI canister. The backpiece  114  preferably is substantially the same as the backpiece disclosed in U.S. Pat. No. 5,848,588. Examples of possible pMDI adapters and canisters to be used in conjunction with the holding chamber  102  are also described in U.S. Pat. Nos. 5,012,803, 5,012,804, 5,848,588 and 6,293,279, the entire contents of each of which is incorporated herein by reference. 
     When a force is applied to the stem of the pMDI canister a portion of the substance is discharged from the discharge end of the pMDI receptacle in aerosol form into the chamber housing  108 . The aerosol medication particles within the chamber housing  108  are withdrawn therefrom by having the patient inhale through the interface  104  in the manner described below. 
     The pMDI canister contains a substance, preferably a medication suspension or solution under pressure. In the present embodiment, the substance dispensed is an HFA propelled medication suspension or solution formulation. Other propellants, such as CFC may also be used. It should be pointed out that while the described embodiments regard an aerosol delivery system for the delivery of an aerosolized medication from a pMDI, other aerosol delivery systems are contemplated that can be used within the spirit of the present invention. For example, it is contemplated that a visual indicator can be incorporated with an aerosol delivery system such as existing ventilator systems, dry powder inhalers and nebulizers, in a manner similar to that described below. Examples of nebulizers that can be adapted to include a visual indicator are disclosed in U.S. Pat. Nos. 5,823,179 and 6,044,841, the entire contents of which are incorporated herein by reference. 
     The present invention is not limited to the treatment of human patients. For example, it is contemplated that a visual indicator can be incorporated in a mask for administering medication to animals, including for example and without limitation equines, cats, dogs, etc. An example of an equine mask is disclosed in U.S. Pat. No. 5,954,049, the entire contents of which are incorporated herein by reference. With such aerosol delivery systems in mind, the variety of medications that can be dispensed by aerosol delivery systems that employ a visual indicator in accordance with the present invention is increased. 
     As shown in  FIG. 4 , a retaining disc  116  is positioned before the opening  112  at the front end of the chamber housing  108 . The retaining disc  116  may be integrally attached to the chamber housing  108  or releasably attached as shown in  FIG. 4 . As shown in  FIGS. 4 and 25-26 , the retaining disc  116  includes an annular ring  118  that surrounds an opening  120 . Four linear appendages  122  extend inwardly from the annular ring  118  and are attached to a circular dome portion  124 . The annular ring  118 , the appendages  122  and the dome portion  124  define an inhalation opening area  126  that includes four openings  126 A- 126 D. The openings  126 A-D are arcuate in shape. The openings have an inner radius of approximately 10 mm and an outer radius of approximately 18 mm. Each opening has an arcuate length of 4 mm. The size, shape and number of openings may vary depending on the medication and/or propellant used. The retaining disc  116  is preferably made of a rigid material, such as a metal or plastic, preferably propylene or polycarbonate. As shown in  FIGS. 4, 25 and 26 , the retaining disc  116  includes a semi-circular stop  117  whose operation will be explained below. Other examples of possible retaining discs are disclosed in U.S. Pat. No. 6,293,279, the entire contents of which are incorporated herein by reference. The annular ring  118  is attached to the front end of the chamber housing  108  so that the openings  112  and  120  are concentric and overlap one another. 
     The center portion of the retaining disc  116  includes a containment baffle positioned so as to partially block the opening  112 . The retaining disc  116  reduces the velocity or flow rate or both of the aerosol medication particles flowing along the axis  128  of the chamber housing  108 . The circular dome portion  124  of the retaining disc  116  is aligned with the central axis  128  of the chamber housing  108  and is directly in line with the opening  112 . Aerosol medication particles that have a flow path away from the central axis  128  tend to have a velocity that is lower than that of particles near to the axis  128 . The dome portion  124  of the retaining disc  116  reduces the forward, on-axis velocity and simultaneously acts as an impaction surface for on-axis projectile aerosol medication particles and so protects the duckbill valve  132 . At the same time, the dome portion  124  allows slower moving aerosol medication particles to migrate towards the sides  130  of the chamber housing  108 . The forward velocity of the aerosol medication particles away from the axis  128  along the chamber length is also reduced by the annular ring  118  of the retaining disc  116 . It should be understood that the dome portion can alternatively be formed with a flat surface facing the rear end, or a curved surface, for example a convex or concave surface. 
     As shown in  FIG. 4 , a duckbill valve  132  is seated on the front surface of the annular ring  118 . The duckbill valve  132  is generally well known in structure having a top surface  134  and a bottom surface  136 . The surfaces  134  and  136  open and close with respect to each other in a well-known manner so as to allow or prevent gas to flow through the valve  132 . The duckbill valve  132  preferably is a 19 mm valve made of a soft plastic, such as silicone or a thermoplastic elastomer. It should be understood that other valves, including for example and without limitation, center post valves, slit petal valves and valves having a central opening with a peripheral sealing edge. 
     On the top portion of the duckbill valve  132 , a visual flow indicator  138  is integrally attached to a top portion of the outer circumference of the duckbill valve  132 . The visual flow indicator  138  is rectangular in shape, although other shapes, such as a square or an ellipse, may also be suitable. For example, the visual flow indicator  138 ′ may have a rounded top edge as shown in  FIGS. 22-24 . The rectangular and rounded visual flow indicators  138 ,  138 ′ each may have a length of 5 mm to 20 mm, preferably a length between 7 mm and 11 mm, and most preferably a length of 8.5 mm, a width of 5 mm-20 mm, preferably 8 mm to 12 mm, and most preferably 10 mm, and a thickness of 0.1 to 2 mm, preferably 0.15-1 mm, and most preferably 0.25 mm. The length of the visual flow indicators  138 ,  138 ′ are measured from a hinge area (not shown). With this in mind, the sensitivity of the visual flow indicators  138 ,  138 ′ is a function of the length of the indicator, wherein as the indicator becomes longer it becomes more sensitive to detecting flow. The operation of the visual flow indicators  138 ,  138 ′ will be described in more detail below. 
     The flow indicator can be integrally formed with the valve or it can be made as a separate member. The indicator  138 ,  138 ′ is hingedly connected to the valve with a living hinge formed at the junction thereof, or it can be hingedly connected with a pin. The resiliency of the indictor  138 ,  138 ′ biases the indicator to an at rest position. However, it should be understood that auxiliary springs can be configured to act on the indicator to bias it to the at rest position. 
     As described above, the chamber housing  108 , retaining disc  116  and duckbill valve  132  define a holding chamber  102 . The holding chamber  102  is attached to a patient interface  104 , although a patient interface integrally molded with the front end of the chamber housing  108  would also be suitable. In one embodiment, the patient interface  104  includes an adapter  140  and a mask  144  with exhalation valve  142 . Other patient interfaces may include for example and without limitation, various mouthpieces, masks, endotracheal tubes, etc. As shown in  FIGS. 4-11 , the adapter  140  includes an annular attachment collar  146  with slots  148 , a transition piece  150  and a cylindrical exit port  152 . The adapter  140  is attached to the chamber  108  by snap inserting the tabs  113  of the chamber housing  108  into the slots  148  and then twisting the chamber housing  108  or adapter  140  so that the tabs  113  are locked into place within the slots  148 . Once the chamber housing  108  is attached to the adapter  140 , the duckbill valve  132  and the flow indicator  138 ,  138 ′ are positioned within the transition piece  150 . In particular, the flow indicator  138 ,  138 ′ is positioned within a raised viewing port area  154  of the transition piece  150 . Since the adapter  140  with its transition piece  150  and raised viewing port area  154  are each made of a clear rigid plastic, such as polycarbonate or a co-polyester, the movement of the flow indicator  138 ,  138 ′ is visible to a user at all times. In another variation, the viewing port area  154  is formed in the collar  146  and the indicator  138 ,  138 ′ is positioned therein. 
     As explained above, the retaining disc  116  is positioned at the front end of the chamber housing, and can be integrally attached thereto or releasably detached, for example by disposing it between the chamber housing and the adapter  140 . In one embodiment, shown in  FIGS. 43 and 44 , the retaining disc  116  is releasably connected to the adapter  140 , or other patient interface component. In one embodiment, a plurality of tabs  123  are formed on the interior of the adapter and engage the outer peripheral edge of the annular ring  118  in a snap-fit engagement. In other embodiments, the retaining disc is integrally molded with the adapter or other patient interface component, or is secured thereto by bonding, fasteners and other similar devices. In this way, the retaining disc  116 , and the valve  132  that is seated thereon between the adapter and the retaining disc, remain coupled to the adapter  140 , or other similar component secured to the end of the chamber housing, upon its removal, for example when cleaning the device. Accordingly, the risk of losing the retaining disc  116  and/or valve  132  is reduced. 
     Note that an alternate embodiment of an adapter is shown in  FIGS. 12-15 . The adapter  140 ′ has similar dimensions and elements as the adapter of  FIGS. 5-11 . Operation and attachment are similar as well. One difference is the shape of the viewing port area  154 ′ in which the indicator  138 ,  138 ′ is positioned. 
     An exhalation valve  142  is inserted into an exit port formed in the nasal reception area  160  of the mask  144  and attached thereto. Examples of such a mask and exhalation valve are disclosed in U.S. Pat. Nos. 5,988,160 and 5,645,049, the entire contents of each of which are incorporated herein by reference. A cylindrical input port  156  of the mask  144  is placed over the exit port  152  of the adapter  140 ,  140 ′ and attached thereto by a friction fit. 
     With the above description of the structure of the aerosol delivery system  100 , the operation of the system  100  can be readily understood. In particular, a patient places his or her face within the interior  158  of the mask  144  so that his or her nose is positioned within the nasal reception area  160 . In other embodiments, the patient or caretaker arranges the patient interface, such as a mouthpiece or endotracheal tube in appropriate registration with the user. The patient or caretaker then presses the pMDI canister within the pMDI adapter of the pMDI  106  attached to the backpiece  114  located at the rear end of the chamber housing  108 , which causes the medication to be delivered in aerosol form to the opening  112  in the manner described previously. 
     At or just after the time of depressing the pMDI canister, the patient inhales. During proper inhalation, the visual flow indicator  138  will pivot forward in response to the inhalation pressure by an angle θ of between 25° to 45°, and preferably 45°, and seal against a surface  162  on the adapter  140 ,  140 ′ as shown in  FIGS. 3 and 33-34 . The angle θ can be varied to take into account the attributes of the patient, i.e., child v. infant. Note that the visual flow indicator  138  has minimal resistance, due to its size and shape, and will respond to low tidal volumes, which is ideal for infants (tidal volume of approximately 50 cc, flow rate approximately 5 lpm) and small children (tidal volume ranging from approximately 150 to 250 cc, flow rate approximately 12 lpm). The movement of the visual flow indicator  138 ,  138 ′ against surface  162  creates a seal that will prevent entrainment of ambient air. A caregiver who directs his or her attention to the viewing port area  154 ,  154 ′ will be able to see the movement of the flow indicator  138 ,  138 ′ as it forms the seal and so will become aware that inhalation is occurring or has occurred. Also during inhalation, the duckbill valve  132  will open thereby allowing the aerosolized medication to exit the chamber housing  108  and be introduced by the opening  112  to a downstream path upon which the medication flows along so as to eventually be inhaled by the patient. As shown in  FIGS. 2 and 31-34 , the flow indicator  138 ,  138 ′ is positioned above the duckbill valve  132  and outside the periphery of opening  112 , and so is outside of the medication dispensing pathway, and thus does not compromise medication delivery. Note that the introduction of the medication to the pathway through the opening  112  can be caused by either external or internal forces. 
     Once the patient exhales or ceases to inhale, the flow indicator  138 ,  138 ′ will pivot back to its original vertical position until it engages the stop  117  as shown in  FIGS. 31-32 . The resiliency of the indicator  138 ,  138 ′ pivots or biases the indicator to the at-rest position. Again, a caregiver who directs his or her attention to the viewing port area  154 ,  154 ′ will be able to see the return movement of the flow indicator  138 ,  138 ′ and so will become aware that exhalation has occurred. Besides alerting the caregiver that inhalation or exhalation is occurring or has occurred, the movement of the flow indicator gives the caregiver confidence that, where the patient interface includes a mask, a proper seal is formed between the patient&#39;s face and the mask  144 . 
     Note that the flow indicator  138 ,  138 ′ does provide a pathway which is in fluid contact with ambient air located within the viewing port area  154 ,  154 ′ rearward of the flow indicator  138 ,  138 ′. The pathway includes a rearward opening or an opening formed in the rearward top portion of the viewing port area  154 ,  154 ′, such that the flow indicator  138 ,  138 ′ is drawn off of the stop. However, the flow indicator  138 ,  138 ′ seals against surface  162  to prevent the entrainment of ambient air as described above. 
     The primary pathway for exhaled gases is through the exhalation valve  142  located in the mask  144  as shown in  FIG. 30 . In particular, the stop  117  and flow indicator  138 ,  138 ′ extend so as to substantially block all exhaled gases from escaping via the viewing port while allowing ambient air to flow therein. Similarly, the stop  117  and flow indicator  138 ,  138 ′, which is registered against surface  162  upon inhalation, substantially blocks the dispensed substance from exiting the delivery system via the viewing port area. Accordingly, the stop  117  and flow indicator  138 ,  138 ′ substantially prevents non-ambient gases and substances from escaping from the delivery system via the viewing port area. Note that the stop  117  may be removed so as to allow the viewing port area to act as a two-way valve that allows ambient atmosphere to enter and exhalation gases to exit therefrom. 
     An alternative embodiment of an aerosol delivery system is shown in  FIG. 35 . The aerosol delivery system  200  is the same as the aerosol delivery system  100  of  FIGS. 1-11, 16-21 and 25-29  except that the holding chamber and the patient interface have been altered as shown in the drawings and as described herein. Accordingly, like elements will retain like numerals. With this in mind, the holding chamber or conduit  202  has a backpiece  114  attached to a rear end of the chamber housing  108 . An opening of the backpiece  114  receives a discharge end of an adapter (not shown) that houses the pMDI canister. The holding chamber  202  further includes a retaining disc  216  that is integrally attached to a front end of the cylindrical chamber housing  108 . The retaining disc  216  includes an annular ring  218  that surrounds an opening  220 . Eight linear appendages  222  extend inwardly from the annular ring  218  and meet at a center hub  223 . The annular ring  218 , the appendages  222  and the center hub  223  define an inhalation opening area  226  that includes eight openings. The size, shape and number of the openings may vary depending on the medication and/or propellant used. 
     As shown in  FIG. 35 , a petal valve  232  is attached to the front surface of the annular ring  218 . In particular, pegs  233  integrally formed on the annular ring  218  are snugly inserted into corresponding openings  235  formed in the petal valve  232 . The operation of the petal valve  232  is well known in the art. The petal valve is preferably made of a material similar to that of the duckbill valve  132 . On the top portion of the petal valve  232 , a visual flow indicator  138 ,  138 ′ is integrally attached to a top portion of the outer circumference of the petal valve  232 . 
     The holding chamber or conduit  202  is attached to an interface similar to the interface  104  shown in  FIGS. 1-11, 16-21 and 25-29 . The interface of the embodiment of  FIG. 35  differs from the interface  104  in that a shorter adapter  240  is used, which includes a cylindrical exit port  252  that can function as a mouthpiece. Alternatively, the adapter  240  can be attached to an exhalation valve and a mask (not shown) in the manner described with respect to  FIGS. 1-11, 16-21 and 25-29 . As shown in  FIG. 35 , the adapter  240  includes an annular attachment collar  246  with slots  248 , a transition piece  250  and a cylindrical exit port  252 . The adapter  240  is attached to the chamber housing  108  by snap inserting tabs  212  of the chamber housing  108  into the slots  248  and then twisting the chamber housing  108  or adapter  240  so that the tabs  212  are locked into place within the slots  248 . Once the chamber housing  108  is attached to the adapter  240 , the petal valve  232  and the flow indicator  138 ,  138 ′ are positioned within the transition piece  250 . In particular, the flow indicator  138 ,  138 ′ is positioned within a raised viewing port area  254  of the transition piece  250 . The adapter  240  with its transition piece  250  and raised viewing port area  254  are each made of a clear rigid plastic, such as polycarbonate or a co-polyester. The chamber housing  108  can also be made of a clear material, such as a rigid plastic. Thus, a caregiver is able to visualize the movement of the visual flow indicator  138 ,  138 ′ within the adaptor  240  and is able to detect whether inhalation is being performed or a proper seal is present in the same manner as with the aerosol delivery system of  FIGS. 1-11, 16-21 and 25-29 . The adapter can also include a stop member that interfaces with the flow indicator. 
     In each of the embodiments shown in  FIGS. 1-35 , the visual flow indicator  138 ,  138 ′ is integrally attached to its corresponding valve. It should be pointed out that such integral attachment is not necessary. For example, it is possible to take a separate piece of material in the shape and composition of indicator  138 ,  138 ′ and attach one end to a portion of the adapter so that a free end of the material lies within the viewing port. Attachment can be accomplished by inserting the one end between two ridges formed in the adapter and gluing the end therebetween. 
     Another example of where the visual flow indicator is not attached to a valve is shown in  FIG. 36 . In this embodiment, a visual flow indicator  338  is attached to an aerosol delivery system  300  similar to the one disclosed in U.S. Pat. No. 6,293,279. One difference is that the chamber housing  308 , attached to the canister holding portion  309 , includes a transparent viewing port  354 . In an alternative embodiment, the view port can be formed on the downstream portion  311  of the delivery system. The visual flow indicator  338  is attached to either the chamber housing  308  or the downstream portion  311  that includes the mouthpiece  313  via a snap fit. The visual flow indicator  338  preferably has a shape and a structure similar to that of the visual flow indicators  138 ,  138 ′ described previously so as to have a similar range of motion. In operation, the chamber housing  308  acts as a conduit of the substance as it travels to the mouthpiece  313 . 
     Other variations for the visual flow indicator are also possible. For example, the viewing port area can be positioned elsewhere on the adapters  140 ,  240 , the chamber housing  308  and the downstream portion  311  and the corresponding visual flow indicator is positioned so as to be viewed from the viewing port area. In the case of the aerosol delivery system of  FIGS. 1-11, 16-21 and 25-29 , the viewing port area can be moved to the side of the adapter  140  in the manner shown in  FIG. 37 . In such a case, the corresponding visual flow indicator  138 ,  138 ′ is moved to a side of the duckbill valve  132  that faces the viewing port area  154 ,  154 ′. 
       FIGS. 38-42  show the present invention used in aerosol delivery systems such as dry powder inhalers and nebulizer systems. In the case of dry powder inhalers, a dry powder inhaler  400  includes a chamber housing  402  that contains a dry powder as shown in  FIGS. 38 and 39 . The chamber housing  402  is similar to the chamber housing disclosed in U.S. Pat. No. 4,627,432, the entire content of which is incorporated herein by reference. Other dry powder inhalers that can incorporate a flow indicator are disclosed for example and without limitation in U.S. Pat. No. 6,116,239, which is hereby incorporated herein by reference. The chamber housing  402  includes a circular bottom opening  404  and a top opening  406  that is in fluid communication with ambient air. An interface which includes a conduit or mouthpiece  408 , is attached to the bottom opening  404  so that the mouthpiece  408  is in fluid communication with the interior of the chamber housing  402 . Attached to the mouthpiece  408  is a transparent viewing port area  410 . Within the viewing port area  410 , a visual flow indicator  412  is positioned. The visual flow indicator  412  has a rear, lower slot (not shown) that receives a ridge  414  formed below the top opening  406 . Once the ridge  414  is received in the rear slot, the visual flow indicator  412  is permanently attached to the ridge  414  by using an adhesive. 
     In operation, the patient activates the chamber housing  402  to provide access to the dry powder within by having the patient inhale through the mouthpiece  408 . Upon inhalation, the dry powder substance within the housing  402  is introduced by the opening  404  to a downstream path along which the substance travels through the interface and the mouthpiece  408  to reach the patient. During inhalation the upper part of the visual flow indicator  412  will pivot downward to a horizontal position. If the patient is not inhaling or fails to inhale above a specified rate of inhalation, the upper part of the visual flow indicator  412  will remain in a vertical position blocking top opening  406 . The range of motion of the visual flow indicator  412  is preferably the same as that of the visual flow indicators  138 ,  138 ′ and  338  mentioned previously. 
     A visual flow indicator can also be used in nebulizer systems. A nebulizer  500  includes a chamber housing  502  that contains a liquid substance as shown in  FIGS. 40-42 . The chamber housing  502  is similar to the chamber housing disclosed in U.S. Pat. No. 5,823,179. The chamber housing  502  includes a rectangular-like exit port  504  that includes an opening (not shown). An interface includes an adapter  506  that is attached to the exit port  504  so as to be in fluid communication with the interior of the chamber housing  502 . The interface also includes a mouthpiece  508  which is attached to the adapter  506  so that the mouthpiece  508  is in fluid communication with the interior of the chamber housing  502  via adapter  506 . Attached to the adapter  506  and mouthpiece  508  are transparent housings  510 ,  512 , respectively. When the mouthpiece  508  is attached to the adapter  506  a transparent viewing port area  514  is formed. Within the viewing port area  514 , a visual flow indicator  516  is positioned. The visual flow indicator  516  has a pair of lower slots  518  that receive a pair of ridges  520 ,  522  formed within the mouthpiece  508 . Once the ridges  520 ,  522  are received in the slots  518 , the visual flow indicator  516  is permanently attached to the ridges  520 ,  522  by using an adhesive. 
     In operation, the patient activates the storage unit  502  by inhaling through the mouthpiece  508 . Upon inhalation, the liquid within the housing  502  is introduced by the opening (not shown) of the exit port  504  to a downstream path along which the substance travels through the interface and the mouthpiece  508  to reach the patient. Thus, the interface  506  and mouthpiece  508  each operate as conduits for the inhaled substance. During inhalation the upper part of the visual flow indicator  516  will pivot downward to a horizontal position. If the patient is not inhaling or fails to inhale above a specified rate of inhalation, the upper part of the visual flow indicator  516  will remains in a vertical position blocking an opening of the housing  510 . The range of motion of the visual flow indicator  516  is preferably the same as that of the visual flow indicators  138 ,  138 ′,  338  and  412  mentioned previously. 
     As described previously, a visual flow indicator according to the present invention can be used in a variety of aerosol delivery systems. In each of the described systems, there is a common way to explain the present invention to encompass each of the previously described aerosol delivery systems. In particular, the aerosol delivery systems can each be thought of as containing a flow indicating system where the portion of the delivery system, such as an interface or a chamber housing, that is attached to the view port area is deemed a conduit. The conduit defines an interior space along which a substance, such as an aerosolized medication, primarily flows along a flow path defined within the interior space. The flow indicating mechanism includes a flow indicator, such as the flow indicators described in  FIGS. 1-42 , that is positioned within the conduit so as to be viewed via the viewing port, but is positioned substantially outside of the flow path so as to not to substantially interfere with the flow of the substance along the interior space. 
     The embodiments of the invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. As noted, the discussion above is descriptive, illustrative and exemplary and is not to be taken as limiting the scope defined by any appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.