Patent Publication Number: US-2022233797-A1

Title: Metered dose inhaler

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 63/142,660, filed Jan. 28, 2021, which application is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates to metered dose inhalers used to deliver rescue medication, a pulmonary medicament, to those with chronic or acute respiratory disease. More specifically, the claimed device has a smaller form factor than the rescue inhalers currently on the market, efficiently releases the rescue medication in a longitudinal direction throughout the inhaler device, and includes a mechanical linkage to translate an applied or input transverse force to an output longitudinal force that actuates a metered dose valve on the medicament canister to release the rescue medication. 
     In the United States, the incidence of asthma has increased by 40% between 2000 and 2019, and COPD is currently the 3rd leading medical cause of death. Approximately 40 million people are currently diagnosed with asthma or COPD, and an estimated 12 million people have yet to be diagnosed according to the National Institutes of Health. To treat these chronic respiratory diseases, doctors typically prescribe an albuterol rescue inhaler. The rescue inhaler, also known as a metered dose inhaler, is used to deliver metered doses of aerosolized pulmonary medicament to the respiratory tract on an as-needed basis. For example, the standard treatment for bronchopulmonary inflammation and airway narrowing (commonly known as an asthma attack) is to administer three metered doses puffs of albuterol. 
     More recently, albuterol metered dose inhalers have also been used to treat patients who have acute cases of lower respiratory tract infections, such as the common cold, the flu, and COVID-19. The COVID-19 pandemic has increased the need for albuterol exponentially. The standard inhaler contains 200 metered doses of albuterol and is intended to last a patient for as long as a full year. Patients who are prescribed a metered dose for COVID-19 or other acute illnesses may only need the inhaler for one to two weeks, and it is very unlikely that the patient will use all 200 metered doses. It is unnecessary to prescribe 200 metered doses of albuterol for an acute illness when the patient will throw away the majority of the medication after they have recovered. The practice of prescribing the standard 200 dose inhalers for acute illness has led to unnecessary medical waste and contributed to the FDA&#39;s issuance of an active shortage warning for albuterol. 
     Furthermore, due to the nature of chronic respiratory diseases, patients need access to their inhaler at all times, even though many only use their inhaler a few times per year or less. However, the currently available metered dose inhalers are too large to comfortably carry on your person at all times. They are also too expensive for the patient to purchase multiple inhalers to have one in the car, in their purse, in their office desk, and anywhere else they commonly spend time. 
     Finally, the L-shaped design of the most common metered dose inhalers creates a complex fluid flow of medicament, air, propellant, and surfactant with asymmetric velocities about the centerline of the mouthpiece. Research has shown that this complex fluid flow causes the direction of the pulmonary medicament leaving the device to dip downward towards the tongue. See, Crosland, B. M., M. R. Johnson, and E. A. Matida, Characterization of the spray velocities from a pressurized metered-dose inhaler. Journal of aerosol medicine and pulmonary drug delivery, 2009. 22(2): p. 85-98. Dunbar, C. A., atomization mechanisms of the pressurized metered dose inhaler. Particulate Science and Technology, 1997. 15(3-4): p. 253-271. Alatrash, A. and E. Matida, Characterization of medication velocity and size distribution from pressurized metered-dose inhalers by phase Doppler anemometry. Journal of Aerosol Medicine and Pulmonary Drug Delivery, 2016. 29(6): p. 501-513. It is hypothesized that this complex fluid flow causes a noticeable amount of the aerosolized medication to land on the tongue of the patient, rather than proceeding straight to the lungs. This known issue results in a less efficient administration of the medication and a weakened treatment of the symptoms. 
     The metered dose inhaler disclosed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one example technology area where some implementations described herein may be practiced. 
     SUMMARY 
     The present disclosure relates to a metered dose inhaler. In particular, the present disclosure relates to a metered dose inhaler having a small size compared to conventional L-shaped inhalers. The disclosed inhaler uses a smaller medicament canister with fewer metered doses which helps reduce unnecessary medical waste. It also reduces the cost so that multiple inhalers may be economically obtained and makes it more feasible to have multiple inhalers for regularly used locations. The small size increases the practicality of carrying a metered dose inhaler on your person at all times due to the smaller form factor. Finally, the inhaler provides a more efficient and effective administration of the aerosolized medication. 
     The metered dose inhaler includes a casing having a longitudinal axis and a transverse axis, where the casing may include a mouthpiece opening at one end along the longitudinal axis, where the casing is configured to house a medicament canister along the longitudinal axis, where the medicament canister may include a plurality of doses of a pulmonary medicament and a metered dose valve configured to release a metered dose of the pulmonary medicament through the mouthpiece opening along the longitudinal axis. As described herein, the longitudinal axis passes through a centerline of the mouthpiece when viewing the device from the side. The inhaler also includes a mechanical linkage configured to translate an applied or input force to the mechanical linkage into an output force along the longitudinal axis configured to actuate the metered dose valve and release the metered dose of the pulmonary medicament in a longitudinal direction along the longitudinal axis. 
     Implementations may include one or more of the following features. The metered dose inhaler comprises a medicament canister. The medicament canister is sized to contain between 20 and 50 doses of the pulmonary medicament. The medicament canister is sized to contain between 30 and 40 doses of the pulmonary medicament. The medicament canister has an outer diameter in the range of 12 mm to 18 mm. The medicament canister has an outer diameter in the range of 14 mm to 16 mm. The metered dose valve has an outer diameter in the range of 12 mm to 18 mm. The metered dose valve has an outer diameter in the range of 14 mm to 16 mm. The medicament canister has a length in the range of 20 mm to 30 mm. The medicament canister has a length in the range of 21 mm to 25 mm. The medicament canister may include an internal dip tube to syphon the pulmonary medicament when the medicament canister is oriented in a horizontal direction. A chamber receives pulmonary medicament released from the metered dose valve in the longitudinal direction and the pulmonary medicament exits the chamber in the longitudinal direction. The casing may include a key ring attachment structure. The metered dose valve may include a stem which is compressed during actuation to release the pulmonary medicament, where the mechanical linkage moves the medicament canister relative to the stem to compress the stem. The mechanical linkage may include a compliant mechanism. The metered dose valve may include a stem which is compressed during actuation to release the pulmonary medicament, where the mechanical linkage moves the stem relative to the medicament canister to compress the stem. The mechanical linkage may include two arms configured to pivot, and where the applied input force to the mechanical linkage causes the two arms to pivot and flex to apply the force along the longitudinal axis to compress the stem. The casing may include one or more air inlet holes configured to allow air to enter the casing. The fluid flow of the pulmonary medicament exiting the casing is symmetric about the centerline of the mouthpiece in a vertical plane along the longitudinal axis. The pulmonary medicament is released from the metered dose valve in the longitudinal direction and exits the casing through the mouthpiece opening in the longitudinal direction. The applied or input force to the mechanical linkage is along the transverse axis. 
     This summary of the present invention is not intended to describe each illustrated embodiment or every possible implementation of the present invention. The figures and the detailed description that follow, however, do particularly exemplify these embodiments. The metered dose inhaler disclosed herein solves the issues and inconveniencies of currently available metered dose inhalers. Specifically, the disclosed inhaler: helps reduce unnecessary medical waste by using a canister with fewer metered doses; increases the practicality of carrying a metered dose inhaler on your person at all times due to the smaller form factor; makes it more feasible to have multiple inhalers for regularly used locations because of its lower cost; and provides a more efficient and effective administration of the aerosolized medication. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. It should be understood that the various embodiments are not limited to the arrangements and instrumentality shown in the drawings. It should also be understood that the embodiments may be combined, or that other embodiments may be utilized and that structural changes, unless so claimed, may be made without departing from the scope of the various embodiments of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Example embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  is a perspective view of an example embodiment of a metered dose inhaler. 
         FIG. 2  is a perspective view of an embodiment of a mechanical linkage in the metered dose inhaler of  FIG. 1 . 
         FIG. 3  is a cross-sectional representation of a medicament canister. 
         FIG. 4  is an exploded view of the mechanical linkage shown in  FIG. 2 . 
         FIGS. 5A-5C  are side views of the mechanical linkage shown in  FIG. 2  illustrating the operation of the mechanical linkage as the button is depressed to actuate the metered dose valve and release the pulmonary medicament. 
         FIGS. 6A-61  show alternative embodiments of mechanical linkages and compliant mechanisms. 
         FIG. 7  is a perspective view of another example embodiment of a metered dose inhaler. 
         FIG. 8  is an exploded perspective view of the metered dose inhaler shown in  FIG. 7 . 
         FIG. 9  is a cross-section view of the metered dose inhaler shown in  FIG. 7 . 
         FIG. 10  is a front view of the metered dose inhaler shown in  FIG. 7 . 
         FIG. 11  is a rear view of the metered dose inhaler shown in  FIG. 7 . 
         FIGS. 12A-12C  are side cross-sectional views of the metered dose inhaler shown in  FIG. 7  illustrating the operation of the mechanical linkage as the button is depressed to actuate the metered dose valve and release the pulmonary medicament. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The metered dose inhalers, also known as rescue inhalers, that are typically prescribed to patients who have asthma, COPD, or other respiratory diseases or infections, are too large to conveniently carry at all times. Although many patients only use their inhaler a few times per year, it is crucial that the inhaler is readily available when needed, for instance, in the event of an asthma attack. The disclosed invention is a metered dose inhaler that has a smaller form factor than the currently available inhalers, making it more convenient to carry at all times. The smaller form factor also solves other issues in the current art, such as reducing medical waste by using a canister with fewer metered doses; making it more feasible to have multiple inhalers for regularly used locations because of the lower cost of a canister with fewer doses; and providing a more efficient and effective administration of the aerosolized medication. 
       FIG. 1  shows one embodiment of a metered dose inhaler. Metered dose inhaler  1  (“the inhaler”) has a casing  10  and a cap  12 . The casing may be manufactured from any suitable material which is durable and light weight. In a disclosed embodiment, casing  10  and cap  12  are constructed of a molded polymeric material or plastic. A plastic construction is advantageous because of the ease and low cost of manufacture, along with the light weight and durability of the material. However, alternative embodiments may utilize other materials, such as aluminum or any other appropriate material. 
     Non-limiting examples of polymeric materials from which the casing is manufactured include polypropylene, polyethylene, polyvinylchloride, polyurethane, polysulfone, polyphenylsulfone, acrylonitrile butadiene styrene, polyethylene terephthalate, polyamide, polyarcrylates, polyvinyl acetates, polyimide, polyamideimide, polymethylmethacrylate, polyetherimide, polyetheretherketone, polyethersulfone, polycarbonate, and polyester. 
     Casing  10  has a generally obround cross section when viewed down its length or longitudinal axis L. The casing  10  is hollow. End  13  of casing  10  is a closed end and end  16  is open. A transverse axis T is also shown. 
     Mouthpiece  14  is situated at end  16 . The mouthpiece  14  may have a similar cross section to casing  10 . The mouthpiece  14  may have a different cross section compared to the casing  10 . In the embodiment shown in  FIG. 1 , the cross-sectional area of mouthpiece  14  is smaller than the cross-sectional area of casing  10 . The smaller cross-sectional area of mouthpiece  14  allows cap  12  to fit over and slide over both end  16  and mouthpiece  14 . When using the inhaler, a user will place their mouth over mouthpiece  14  and inhale through their mouth. 
     Cap  12  is configured to slide over end  16  and mouthpiece  14  and remain there when the inhaler is not in use. Cap  12  is further configured to be slid off mouthpiece  14  and end  16  prior to using the inhaler. In the disclosed embodiment, cap  12  remains slid over end  16  and mouthpiece  14  when the inhaler is not in use by virtue of a friction fit between the mouthpiece and cap. Alternate embodiments of the disclosed invention may employ the use of detents or other suitable retention means to keep cap  12  in place when the inhaler is not in use. The purpose of cap  12  is to prevent foreign objects from entering casing  10  through end  16 , as well as to keep mouthpiece  14  clean and free of foreign objects. Alternative embodiments may use a pivoting or hinged cap configuration rather than a sliding cap configuration to cover end  16  and mouthpiece  14 . 
     The casing  10  may have a key ring attachment structure to facilitate attachment of a key ring. The attachment structure may be a hole or opening. It may be one or more resilient structures to which a key ring may be attached. As shown in  FIG. 1 , key ring  20  is situated near end  13  and is used to securely attach the inhaler to a keychain, lanyard, or other tether. A key ring attachment structure or key ring  20  may alternatively be positioned near end  16  or on cap  12 . 
     Air inlets  18  are situated on the top side of casing  10 . The purpose of air inlets  18  is to promote an efficient flow of air through casing  10  when a user places their mouth over mouthpiece  14  and inhales so that the fluid flow is symmetric in a vertical plane as it exits the mouthpiece. The vertical plane may comprise the longitudinal axis. The vertical plane may comprise the longitudinal and transverse axes. The disclosed inhaler is configured to cause the pulmonary medicament to exit the casing in fluid flow which is symmetric about the centerline of the mouthpiece in a vertical plane along the longitudinal axis. 
     It is to be understood that the direction of the pulmonary medicament fluid flow as it exits the mouthpiece is a general direction. Because of turbulence, individual particulates of pulmonary medicament may be expected to spread, disperse, and otherwise deviate from the longitudinal axis. Thus, as used herein, the fluid flow direction is a general direction of the spray as opposed to each individual streamline or particle of the spray. Thus, the flow of the pulmonary medicament as it exits the metered dose valve of the medicament canister is in a generally linear direction. See, Crosland, B. M., M. R. Johnson, and E. A. Matida, Characterization of the spray velocities from a pressurized metered-dose inhaler. Journal of aerosol medicine and pulmonary drug delivery, 2009. 22(2): p. 85-98. Dunbar, C. A., atomization mechanisms of the pressurized metered dose inhaler. Particulate Science and Technology, 1997. 15(3-4): p. 253-271. Alatrash, A. and E. Matida, Characterization of medication velocity and size distribution from pressurized metered-dose inhalers by phase Doppler anemometry. Journal of Aerosol Medicine and Pulmonary Drug Delivery, 2016. 29(6): p. 501-513. The fluid flow direction of the pulmonary medicament is also mirrored about the centerline of the mouthpiece in a vertical plane along the same longitudinal axis. As a result, the exit velocity and pressure fields are the same on the top and bottom of the mouthpiece. The fluid flow direction of the pulmonary medicament is steady with time. Without being bound by theory, it is believed the linear fluid flow direction of the pulmonary medicament along the longitudinal axis results in a more direct and effective dose of medication to the user&#39;s lungs, rather than the medication landing on the user&#39;s tongue. 
     Air inlets  18  may alternatively be situated on end  13 , on the bottom side of casing  10 , or on the sides of casing  10  and may include fewer or more air inlets. Additionally, the air inlets may be a different shape than what is shown in  FIG. 1 . Sufficient air inlets are provided to enable the symmetric, planar air velocity at the mouthpiece or exit of the inhaler as described herein. The air inlets are preferably located sufficiently far from the mouthpiece so that the air has enough distance and time to mix and normalize in the casing to enforce the described flow characteristics before leaving the inhaler. 
       FIG. 2  is a drawing of one possible mechanical linkage that may be situated inside the hollow cavity of casing  10 . Mechanical linkage  23  is friction fit into casing  10  and is comprised of six separate parts, all of which are constructed of plastic. Plastic is advantageous because it is both flexible and durable. The six separate parts comprising mechanical linkage  23  are best seen in  FIG. 4  and include a canister housing  24 , left lever arm  30 , right lever arm  31 , button  22 , slider block  40 , and slider housing  45 . Mechanical linkage  23  is oriented within casing  10  such that slider housing  45  is near end  16 . 
     Canister housing  24  is configured to hold a medicament canister with a metered dose valve.  FIG. 3  illustrates a medicament canister  51  having a metered dose valve  53  and stem  53 . The medicament canister  53  contains a pulmonary medicament  56 , such as albuterol sulfate, and an inhalation aerosol, such as hydrofluoroalkanes (HFAs). The medicament canister  51  may comprise an internal dip tube  57  to syphon the pulmonary medicament  56  when the medicament canister is oriented in a horizontal direction. 
     Known medicament canisters contain a given number of doses per unit. The standard number of doses ranges from 60 to 200 doses. An important feature of the disclosed invention is the use of a much smaller size medicament canister containing fewer doses than typical. The smaller size enables the inhaler to be manufactured with a smaller form factor. A medicament canister with fewer doses eliminates unnecessary medical waste common with standard 200-dose medicament canisters. 
     The medicament canister outer diameter may range from about 12 mm to about 18 mm, e.g., about 12, 13, 14, 15, 16, 17, or 18 mm, where any of the stated values can form an upper or lower endpoint of a range. 
     The medicament canister length may range from about 15 mm to about 30 mm, e.g., about 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 mm, where any of the stated values can form an upper or lower endpoint of a range. 
     The metered dose valve outer diameter may range from about 12 mm to about 18 mm, e.g., about 12, 13, 14, 15, 16, 17, or 18 mm, where any of the stated values can form an upper or lower endpoint of a range. 
     The medicament canister may contain from about 20 to about 50 doses of the pulmonary medicament, e.g., about 20, 25, 30, 35, 40, 45, or 50 doses, where any of the stated values can form an upper or lower endpoint of a range. 
     The canister rests horizontally in curved trough  25  and is held in place by both main clamping arms  26  and secondary clamping arms  27 . The main clamping arms and the secondary clamping arms are configured to prevent the canister from moving either vertically or horizontally. The canister housing is configured to hold the canister so that the valve end of the canister faces towards slider block  40 . 
     Canister housing  24  has two mounting holes, left arm mounting hole  28  and right arm mounting hole  29 . The two mounting holes and are configured to receive left pin  32  on left lever arm  30  and right pin  33  on right lever arm  31 , respectively. When the respective pin is inserted into the respective mounting hole, the respective lever arm is attached to cannister housing  24 . It should be understood that various separate parts disclosed herein may be combined into one injection molded part. Similarly, instead of having the rotational hinges shown in  32  and  33 , it is within the scope of the disclosed invention to replace these structures with compliant hinges. 
     Button  22  is attached to trunnion  52 , which rests on left trunnion mount  34  of left lever arm  30  and right trunnion mount  35  of right lever arm  31 . When a downward force is applied to button  22 , left lever arm  30  and right lever arm  31  pivot about left pin  32  and right pin  33 , respectively. 
     Left lever arm  30  and right lever arm  31  each include a flexible member, left flexible member  36  and right flexible member  37 , respectively. Left flexible member  36  has left bulb  38  disposed on its end and right flexible member  37  has right bulb  39  on its end. The two bulbs interface with left and right slots  41  and  42  on slider block  40 . Slider block  40  and left and right slots  41  and  42  are configured to interface with the flexible members, such that the flexible members are prevented from moving vertically, as well as prevented from moving in a horizontal plane independently from slider block  40 . 
     As shown in  FIGS. 5A-5C , when a downward force F is applied to button  22 , the lever arms  30 ,  31  pivot about their respective pins,  32 ,  33 . The ends of flexible members  36  and  37  are unable to move in a vertical direction and pivot with the rest of the lever arm because of the interaction with slider block  40 . As a result, the flexible members flex upwards, thereby applying a horizontal force on slider block  40 . This force causes slider block  40  to slide towards the canister housing. 
     Slider block  40  includes spray nozzle hole  43 , which is configured to receive a spray nozzle on a medicament canister  51  with a metered dose valve  53 . The metered dose valve has a stem  54  which is actuated by compressing the stem of the spray nozzle in towards the canister, thereby releasing the metered dose of aerosolized medicament  55 . When slider block  40  slides towards the canister housing, it actuates the canister&#39;s metered dose valve, which results in the aerosolized medication passing through spray nozzle hole  43 . Because the spray nozzle hole is near end  16 , the aerosolized medicament passes through mouthpiece  14  when the user places their mouth on the mouthpiece and inhales. 
     Slider housing  45  receives slider block  40  in opening  50  and is configured to allow and ensure slider block  40  slides normal to the canister. Additionally, the slider housing  45  prevents slider block  40  from moving vertically. Slider housing  45  further includes tabs  46  and  47  that interface with slots  48  and  49  on canister housing  24 , respectively, to prevent the components of mechanical linkage  23  from separating or moving independently. It should be understood that some of these separate parts may be combined into one injection molded part. 
     The various components of the metered dose inhaler may be constructed generally out of any materials known to be suitable in the art. 
     It will be appreciated that the mechanical linkage shown in  FIGS. 2 and 4  is only one possible way of converting an applied input force in one direction, such as a transverse or vertical direction, into an output force in another direction, such as a longitudinal or horizontal direction. 
       FIGS. 6A-61  illustrate a variety of possible mechanical linkages and compliant mechanisms which one might utilize in the metered dose inhaler disclosed herein. A compliant mechanism is a flexible mechanism that achieve force and motion transmission through elastic body deformation. It will be appreciated that numerous possible mechanical linkages and compliant mechanisms may be implemented, and the invention is not limited to any specific mechanical linkage or compliant mechanism disclosed herein. As used herein, the term “mechanical linkage” includes compliant mechanisms which transmits an applied input force in one direct into an output force in a different direction. For example, the mechanical linkage may transmit an applied input force in a transverse direction into an output force in the longitudinal direction. 
       FIGS. 7-12C  illustrate an embodiment of another metered dose inhaler  60 . Metered dose inhaler  60  (“the inhaler”) has a casing  62 . Like casing  10 , the casing  62  may be manufactured from any suitable material which is durable and light weight. In a disclosed embodiment, the casing  62  may be constructed of a molded polymeric material or plastic. A plastic construction is advantageous because of the ease and low cost of manufacture, along with the light weight and durability of the material. However, alternative embodiments may utilize other materials, such as aluminum or any other appropriate material. 
     Non-limiting examples of polymeric materials from which the casing  62  is manufactured include polypropylene, polyethylene, polyvinylchloride, polyurethane, polysulfone, polyphenylsulfone, acrylonitrile butadiene styrene, polyethylene terephthalate, polyamide, polyarcrylates, polyvinyl acetates, polyimide, polyamideimide, polymethylmethacrylate, polyetherimide, polyetheretherketone, polyethersulfone, polycarbonate, and polyester. 
     Casing  62  has a generally obround cross section when viewed down its length or longitudinal axis L. The casing  62  is hollow. A transverse axis T is also shown. 
     A mouthpiece  64  is situated at end  66 . When using the inhaler  60 , a user will place their mouth over mouthpiece  64  and inhale through their mouth. 
     A locking cap  68  is disposed at end  70  of casing  62 . The locking cap includes a depressible button  72 . 
     As shown in  FIGS. 8 and 9 , the locking cap  68  is configured to retain a mechanical linkage  74 . The locking cap may include a fastener, such as a pair of elastic hooks  76  which are received in openings  78  formed in casing  62 . Other known and novel fastening structures may be used to secure the locking cap to the casing. 
     The casing  62  includes an interior space  80  sized and configured to house a medicament canister along the longitudinal axis L. As disclosed above, the medicament canister may include a plurality of doses of a pulmonary medicament and a metered dose valve configured to release a metered dose of the pulmonary medicament through the mouthpiece  64  along the longitudinal axis L. The metered dose valve has a stem which is actuated by compressing the stem of the spray nozzle in towards the canister, thereby releasing the metered dose of aerosolized medicament. As shown in  FIG. 9 , the casing  62  includes a wall  82  adjacent the mouthpiece  64 . The wall  82  includes a stem receiver  84  which is sized and configured to receive the stem of a metered dose valve of a pulmonary medicament canister. The wall  82  includes a chamber  85  to receive pulmonary medicament released from the metered dose valve through the stem in the longitudinal direction. The wall  82  further includes a spray nozzle hole  86 . Pulmonary medicament exits the chamber  85  in the longitudinal direction through the spray nozzle hole  86 , which allows aerosolized pulmonary medicament to pass into the mouthpiece. 
     The mechanical linkage  74  is fabricated of an elastic material. The mechanical linkage  74  transmits an applied force A to the button  72  into an output force B in a different direction, such as the longitudinal axis. 
     As shown in  FIG. 10 , air inlets  88  are formed in wall  82  and allow air to pass through when a user places their mouth over mouthpiece  64  and inhales. As shown in  FIG. 11 , air inlets  90  are formed in locking cap  68  and allow air to pass through when a user places their mouth over mouthpiece  64  and inhales. 
     The air inlets  88 ,  90  promote an efficient flow of air through casing  62  when a user places their mouth over mouthpiece  64  and inhales so that the fluid flow is symmetric about the centerline of the mouthpiece in a vertical plane along the longitudinal axis as it exits the mouthpiece  64 . The vertical plane may comprise the longitudinal axis. The vertical plane may comprise the longitudinal and transverse axes. 
     It is to be understood that the direction of the pulmonary medicament fluid flow as it exits the mouthpiece is a general direction. Because of turbulence, individual particulates of pulmonary medicament may be expected to spread, disperse, and otherwise deviate from the longitudinal axis. Thus, as used herein, the fluid flow direction is a general direction of the spray as opposed to each individual streamline or particle of the spray. Thus, the flow of the pulmonary medicament as it exits the metered dose valve of the medicament canister is in a generally linear direction. The fluid flow direction of the pulmonary medicament is also mirrored about the centerline of the mouthpiece in a vertical plane along the same longitudinal axis. As a result, the exit velocity and pressure are the same on the top and bottom of the mouthpiece. The fluid flow direction of the pulmonary medicament is steady with time. Without being bound by theory, it is believed the linear fluid flow direction of the pulmonary medicament along the longitudinal axis results in a more direct and effective dose of medication to the user&#39;s lungs, rather than the medication landing on the user&#39;s tongue. 
     Air inlets  88 ,  90  may alternatively be situated one or more sides of casing  62  and may include fewer or more air inlets. Additionally, the air inlets may be a different shape than what is shown in  FIGS. 10 and 11 . Sufficient air inlets are provided to enable a symmetric, planar air velocity at the mouthpiece  64  or exit of the inhaler as described herein. The air inlets are preferably located sufficiently far from the mouthpiece so that the air has enough distance and time to mix and normalize in the casing to provide the described flow characteristics before leaving the inhaler. 
       FIGS. 12A-12C  illustrate the action of the inhaler when a downward force A is applied to button  72 . As the button  72  is pressed with downward force A, the mechanical linkage  74  is compressed in a manner than creates the force B, shown in  FIG. 9 . This horizontal force B moves medicament canister  92  in a longitudinal direction towards wall  82 . The medicament canister  92  includes a metered dose valve  94 . The metered dose valve has a stem  96 . The stem is positioned in the stem receiver  84 . The stem  96  is actuated by compressing the stem of the spray nozzle in towards the medicament canister, thereby releasing the metered dose of aerosolized medicament  98 . 
     Because the spray nozzle hole  86  is near end  66 , the aerosolized medicament  98  passes through mouthpiece  64  when the user places their mouth on the mouthpiece and inhales. The aerosolized medicament  98  exits the casing  62  in a fluid flow which is symmetric in a vertical plane. In some embodiments, the aerosolized medicament  98  exits the casing  62  in a fluid flow which is symmetric in a vertical plane along the longitudinal axis L. 
     Embodiments 
     Various embodiments are listed below. It will be understood that the embodiments listed below may be combined with all aspects and other embodiments in accordance with the scope of the invention. 
     Embodiment 1. A metered dose inhaler comprising: a casing having a longitudinal axis and a transverse axis, wherein the casing comprises a mouthpiece opening at one end along the longitudinal axis, wherein the casing is configured to house a medicament canister along the longitudinal axis, wherein the medicament canister comprises a plurality of doses of a pulmonary medicament and a metered dose valve configured to release a metered dose of the pulmonary medicament through the mouthpiece opening along the longitudinal axis; and a mechanical linkage configured to translate an applied force to the mechanical linkage into a force along the longitudinal axis configured to actuate the metered dose valve and release the metered dose of the pulmonary medicament in a longitudinal direction along the longitudinal axis. 
     Embodiment 2. The metered dose inhaler of embodiment 1, wherein the medicament canister is sized to contain between 20 and 50 doses of the pulmonary medicament 
     Embodiment 3. The metered dose inhaler of any preceding embodiment, wherein the medicament canister is sized to contain between 30 and 40 doses of the pulmonary medicament. 
     Embodiment 4. The metered dose inhaler of any preceding embodiment, wherein the medicament canister has an outer diameter in the range of 12 mm to 18 mm. 
     Embodiment 5. The metered dose inhaler of any preceding embodiment, wherein the medicament canister has an outer diameter in the range of 14 mm to 16 mm. 
     Embodiment 6. The metered dose inhaler of any preceding embodiment, wherein the metered dose valve has an outer diameter in the range of 12 mm to 18 mm. 
     Embodiment 7. The metered dose inhaler of any preceding embodiment, wherein the metered dose valve has an outer diameter in the range of 14 mm to 16 mm. 
     Embodiment 8. The metered dose inhaler of any preceding embodiment, wherein the medicament canister has a length in the range of 15 mm to 30 mm. 
     Embodiment 9. The metered dose inhaler of any preceding embodiment, wherein the medicament canister has a length in the range of 19 mm to 24 mm. 
     Embodiment 10. The metered dose inhaler of any preceding embodiment, wherein the medicament canister comprises an internal dip tube to syphon the pulmonary medicament when the medicament canister is oriented in a horizontal direction. 
     Embodiment 11. The metered dose inhaler of any preceding embodiment, further comprising a chamber connected to the metered dose valve to permit mixing and expansion of the pulmonary medicament as it is released from the metered dose valve, wherein the chamber receives pulmonary medicament released from the metered dose valve in the longitudinal direction and the pulmonary medicament exits the chamber in the longitudinal direction. 
     Embodiment 12. The metered dose inhaler of any preceding embodiment, wherein the casing comprises a key ring attachment structure. 
     Embodiment 13. The metered dose inhaler of any preceding embodiment, wherein the metered dose valve comprises a stem which is compressed during actuation to release the pulmonary medicament, wherein the mechanical linkage moves the medicament canister relative to the stem to compress the stem. 
     Embodiment 14. The metered dose inhaler of any embodiment 1 through 12, wherein the metered dose valve comprises a stem which is compressed during actuation to release the pulmonary medicament, wherein the mechanical linkage moves the stem relative to the medicament canister to compress the stem. 
     Embodiment 15. The metered dose inhaler of any preceding embodiment, wherein the mechanical linkage comprises a compliant mechanism. 
     Embodiment 16. The metered dose inhaler of any preceding embodiment, wherein the mechanical linkage comprises two arms configured to pivot, and wherein the applied force to the mechanical linkage causes the two arms to pivot and flex to apply the force along the longitudinal axis to compress the stem. 
     Embodiment 17. The metered dose inhaler of any preceding embodiment, wherein the casing comprises one or more air inlet holes configured to allow air to enter the casing. 
     Embodiment 18. The metered dose inhaler of any preceding embodiment, wherein the pulmonary medicament exits the casing in a fluid flow which is symmetric in a vertical plane along the longitudinal axis. 
     Embodiment 19. The metered dose inhaler of any preceding embodiment, wherein the pulmonary medicament exits the casing in a fluid flow which is symmetric in a vertical plane. 
     Embodiment 20. The metered dose inhaler of any preceding embodiment, wherein the main direction of the pulmonary medicament fluid flow exiting the casing is constant in time. 
     Embodiment 21. The metered dose inhaler of any preceding embodiment, wherein the pulmonary medicament is released from the metered dose valve in the longitudinal direction and exits the casing through the mouthpiece opening in the longitudinal direction. 
     Embodiment 22. The metered dose inhaler of any preceding embodiment, wherein the applied force to the mechanical linkage is along the transverse axis. 
     Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. Although specific terms are employed herein, they are used in a generic and descriptive sense only, and not for purposes of limitation. 
     While the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the method and apparatus of the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention include modifications and variations that are within the scope of the appended claims and their equivalents.