Abstract:
An inhalation apparatus for medicinal use which will deliver aerosolized medication to the patient that comprises up to about 80% of the medication aerosolized in essentially the same particle size distribution of the aerosol mist that originates from the nebulizer which produces the mist. The apparatus also provides delivered dose consistency over a wide range of patient breathing parameters.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to inhalation devices. More particularly, the invention concerns an improved aerosol inhalation apparatus for medicinal use that delivers a mist of properly sized aerosol particles of medicament to the patient with a very high-level of efficiency. 
   2. Discussion of the Prior Art 
   Therapeutic aerosols are commonly administered to patients suffering from numerous types of pulmonary diseases. Specific medications include beta.sub.2 agonizes, anticholinergies, cromolyn sodium, and steroids. More recently the aerosol method of delivery has been used to administer Pentamidine to patients afflicted with AIDS, Tobramycin for cystic fibrosis, Morphine for pain, and is presently under consideration as a delivery means for use in drug delivery using gene therapy. Experience has shown that the use of aerosols to treat lung disease is highly advantageous in that it produces optimal therapy with minimum side effects. 
   Both physical and clinical factors affect aerosol deposition in the lungs. Physical factors include inertial impaction, sedimentation, and diffusion. Clinical factors include particle size, ventilatory pattern and lung function. Aerosols larger than 5 micron mass median aerodynamic diameter (MMAD) poorly penetrate the upper respiratory tract. Those in the 1 to 2 micron range tend to have their maximum deposition in the lung parenchyma. 
   In general the devices used for producing medical aerosols fall into two categories; the small volume nebulizer (SVN), and the metered dose inhaler (MDI). The small volume nebulizer (SVN) has traditionally been the apparatus of choice for delivery of therapeutic aerosols. The delivery apparatus typically consists of a disposable or reusable nebulizer, a mouthpiece or facemask, and a pressurized gas source usually oxygen or air. The metered dose inhaler (MDI), on the other hand, typically contains the active drug, a metering valve, and chlorofluorcarbon (CFC) or hydrofluoroalkanes (HFA) propellants. The drug-containing canister of the device is generally fitted to a mouthpiece actuator and activation by compression of the canister into the mouthpiece results in the release of a unit dose of medication. 
   As stated in current literature ( Respiratory Care , Vol. 38, No. 38, August 93, and  Advance for Respiratory Care Practitioners , Aug. 9, 1993, pages 8-10) the most limiting factor in the use of aerosolized medication is the inefficient mist production by current commercial nebulizer systems, whether they are of the small volume nebulizer (SVN) or metered dose inhaler (MDI) variety. Research has shown that most state-of-the-art commercial units deliver less than 10% of the original dose of medication to the patient&#39;s respiratory tract. ( Respiratory Care , Vol. 38, #8, August 1993, Page 877, and  AARC Times , June 1993, Page 48.) The apparatus of the present invention provides a very substantial improvement over all existing prior art aerosol devices by increasing the efficiency of delivery of medication to the patient by a factor of 2 to 3 times that exhibited by currently available prior art nebulizer devices. As a further substantial benefit, the apparatus of the present invention functions in a manner to assure that the medicament particles delivered to the patient will be of optimum size for drug delivery to any or all areas of the lung where it can most effectively be utilized. 
   A highly successful general purpose aerosol inhalation apparatus for use in respiratory therapy procedures in the field of medicine is disclosed in U.S. Pat. No. 5,727,542 issued to the present inventor. The apparatus described in this patent converts liquid medication into an aerosol mist and provides for delivery of this mist with such high efficiency that up to 40% of the original dose of medication placed in the nebulizer can be delivered to the patient&#39;s lungs. The present invention comprises an improvement to the apparatus disclosed in U.S. Pat. No. 5,727,542 and provides for delivery of the aerosol mist to the patient at substantially equal efficiency. The present invention can also deliver drugs at these high efficiencies to patients on ventilators, where the device disclosed in U.S. Pat. No. 5,727,542 cannot. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide an inhalation apparatus which will deliver an aerosolized medication to the patient, which comprises up to about 80% of the medication aerosolized. 
   Another object of the invention is to provide an apparatus of the aforementioned character, which will deliver to the patient essentially the same particle size distribution of the aerosol mist that originates from the nebulizer itself. 
   Another object of the invention is to provide delivered dose consistency even over a wide range of patient breathing parameters. 
   Another object of the invention is to provide a novel inhalation device, which will deliver known amounts of aerosolized medication to patients while on respirators. 
   Another object of the invention is to provide an apparatus, which releases only minimal amounts of drug to atmosphere. 
   Yet another object of the invention is to provide means for safely filtering air exhaled from the patient before its release to room atmosphere. 
   Still another object of the invention is to provide an inhalation apparatus of the general character described in the preceding paragraphs which can be used with a conventional ventilator. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a generally perspective view of one form of the inhalation apparatus of the invention. 
       FIG. 2  is an enlarged, longitudinal cross-sectional view of the inhalation apparatus shown in  FIG. 1 . 
       FIG. 3  is a front view out of one of the flow control valves of the apparatus of the invention. 
       FIG. 4  is an enlarged cross-sectional view of the area designated as  4  in  FIG. 2 . 
       FIG. 5  is an enlarged cross-sectional view taken along lines  5 - 5  of  FIG. 2 . 
       FIG. 6  is an enlarged cross-sectional view taken along lines  6 - 6  of  FIG. 2 . 
       FIG. 7  is a generally perspective, exploded view of the housing of the apparatus shown in  FIG. 1  illustrating internal construction. 
       FIG. 8  is a generally perspective view of a chamber defining insert receivable within the housing portion of the apparatus of the invention. 
       FIG. 9  is a generally perspective view illustrating of the manner of positioning the chamber defining insert shown in  FIG. 8  within the main housing portion of the apparatus. 
       FIG. 10  is a generally diagrammatic, top plan view of the apparatus illustrating the fluid flow path through the various cooperating chambers of the apparatus. 
       FIG. 11  is a generally diagrammatic, cross-sectional view of the apparatus further illustrating the fluid flow path through the various cooperating chambers of the apparatus. 
       FIG. 11A  is a generally diagrammatic, cross-sectional view of an alternate form of the invention that can be used with a conventional ventilator apparatus. 
       FIG. 12  is a generally perspective view of an alternate form of the inhalation apparatus of the invention. 
       FIG. 13  is a cross-sectional view taken along lines  13 - 13  of  FIG. 12 . 
       FIG. 14  is a cross-sectional view taken along lines  14 - 14  of FIG.  13 . 
       FIG. 15  is a cross-sectional view taken along lines  15 - 15  of  FIG. 13 . 
       FIG. 16  is an enlarged cross-sectional view taken along lines  16 - 16  of  FIG. 13 . 
       FIG. 17  is a cross-sectional view taken along lines  17 - 17  of  FIG. 13 . 
       FIG. 18  is an enlarged cross-sectional view taken along lines  18 - 18  of  FIG. 13 . 
       FIG. 19  is a cross-sectional view taken along lines  19 - 19  of  FIG. 18 . 
       FIG. 20  is a generally perspective, exploded view of the apparatus of this latest form of the invention. 
       FIG. 21  is an exploded, longitudinal cross-sectional view of the apparatus shown in  FIG. 20 . 
   

   DESCRIPTION OF THE INVENTION 
   Referring to the drawings and particularly to  FIGS. 1 and 2 , the aerosol inhalation apparatus of one form of the invention is there shown and can be seen to comprise a housing  22  which includes interconnected front, back, side and bottom walls  24 ,  26 ,  28  and  30  respectively. Attached to housing  22  is a nebulizer means, shown here as a conventional, small volume nebulizer (SVN)  32  ( FIG. 1 ). A first end  22   a  of the main housing is provided with a standard size breathing port  34  for ready patient interfacing with the aerosol system. A second end  22   b  of the main housing is provided with an outlet port  36  to which filter means, shown here as a filter assembly  38  can be interconnected ( FIG. 2 ) if so desired. 
   As best seen by referring to  FIGS. 2 ,  8  and  9 , housing  22  includes a main portion  22   c  and a chamber defining, insert portion  22   d  which is received within main portion  22   c  in the manner shown by the solid lines in  FIG. 9 . Housing  22  also includes a first chamber  40  having an inlet  42   a  defined by an inlet port  42 , an outlet  44  and baffle means for providing a circuitous fluid flow path through the first chamber. In the present form of the invention this important baffle means comprises a plurality of longitudinally spaced-apart, strategically configured baffles or walls  46 ,  48  and  50 . Housing  22  also includes a second chamber  52  having an inlet  54  in communication with a first chamber  40  and an outlet  56  in communication breathing port  34 . Insert portion  22   d  in cooperation with a housing top wall  56  defines a third chamber  58  chamber having an inlet  60  in communication with said second chamber  52  and an outlet  62 , which communicates with outlet port  36  via a first flow control means, here provided as a flapper valve mechanism  64 . 
   As shown in  FIG. 1 , nebulizer  32  is interconnected with inlet port  42  for communication with first chamber  40  for nebulizing a fluid medication containing the medicament to produce a particulate laden spray and for introducing said particulate laden spray into first chamber  40 . 
   A second flow control means, shown here as valve member  68  is pivotally movable relative to inlet  54  of said second chamber  52  for controlling fluid flow through the inlet and into second chamber  52 . 
   Before discussing the operation of the apparatus of the invention as described in the preceding paragraphs, a brief discussion of the theory of patient inhalation and dose quantification is believed appropriate. In this regard, the breathing cycle for a patient involves an inhalation and exhalation component, usually in a time ratio of one part inhalation and two parts exhalation (i.e. 1:2). As an example, if a patient is breathing at a rate of 12 breaths per minute (BPM) the complete breathing cycle would involve 5 seconds (60 sec./12 BPM=5 sec.), and at a 1:2 inhalation/exhalation ratio, the exhalation time would be in the order of 3.3 seconds. When a normal nebulizer configuration is used, the drug as aerosolized by the nebulizer is blown into the atmosphere for ⅔s of each breathing cycle. If this aerosol could be retained and added to that received during the next patient inhalation, system efficiency would be greatly enhanced and the delivered patient dose should be quantifiable. The reservoir component of the present invention, when used with an air/oxygen flow rate of 7-8 liters per minute (LPM) to the nebulizer, is the correct volume to allow for this needed medication retention. Determination of the minimum volume needed is as follows: 
                 60   ⁢           ⁢     sec   .         12   ⁢           ⁢   BPM       ⁢     (     5   ⁢           ⁢   seconds     )     ⁢     (     2   /   3     )       =     3.3   ⁢           ⁢   second   ⁢           ⁢   exhalation                       (     3.3   ⁢           ⁢   seconds     )     ⁢     (     7   ⁢     ,     ⁢   000   ⁢           ⁢   ml   ⁢     /     ⁢     min   .       )       60     =     385   ⁢           ⁢     ml   .           ⁢   volume             
Knowing that medication lost is very small, and in general a relatively fixed percentage of that aerosolized, quantification of the patient dose received is very possible using the following equation:
 Inhaled Dose=(drug concentration)(drug mass aerosol rate [DMAR])(system efficiency)(time). 
Where drug concentration is known at the start of the procedure; DMAR is an easily determined fixed number for a given nebulizer at a defined oxygen flow rate; system efficiency is a relatively fixed number for given system; and time is the system run time determined prior to start, or just prior to nebulizer sputter.
 
   With the foregoing in mind, it can be seen that reservoir chamber  40  consists of a fixed, determinable volume. As indicated by the previous calculations, in practice, chamber  40  preferably has a minimum volume of about 400 ml., which approximately equals the volume of aerosol produced by the nebulizer  32  during the time of patient exhalation under typical conditions such as an oxygen flow rate of about 7 liters per minute, a breathing rate of approximately 12 breaths per minute and an “in-out” ratio of about 1:2. 
   Referring to  FIG. 11 , it can be seen that upon patient exhalation, the. expired air will pass through chamber  22  and first control means flapper valve number  64 , and exiting the device through port  75 . In so doing air pressure against second flow control means, here shown as a conventional, flapper-type valve member  68 , which is pivotally movable relative to inlet  54  of second chamber  52 , moves from the open position shown in  FIG. 2  into the closed position shown in  FIG. 11 . With a valve member  68  closed, the aerosol, which is being newly generated by the nebulizer  32 , flows into chamber  40  in the manner indicated by the arrows  69 . As indicated by the arrow  71  in  FIG. 10 , as the newly generated aerosol flows into chamber  40 , the residual air contained within the chamber will flow around and about the interior baffles  46 ,  48  and  50  in the manner indicated by the arrows  73  in  FIG. 9  and will be pushed outwardly through exhaust port  36  in the manner indicated by the arrow  75  of  FIG. 11 . 
   As previously discussed, duration of the expiration will be in the order of 3-4 seconds or less during which the newly generated aerosol will fill all pathways in chamber  40 . Next, upon patient inhalation, atmospheric air will be drawn in through port  36  causing valve member  64  to close and through displacement force all aerosol in reservoir  40  to pass through flow control means  54  and out to the patient. Additionally, during this time of patient inhalation, aerosol coming from continuously operating nebulizer member  32  ( FIG. 1 ) is also being received by the patient. It can be readily seen by those skilled in the art that drug is delivered very efficiently, and drug loss is not only minimal but essentially a constant percentage of that aerosolized. 
   In summary, due to the unique design of the apparatus of the invention, essentially all of the aerosolized medication (only loss—a relatively small percentage retained in the body of the device) is accessed by the patient and the effects of patient breathing parameters are minimized or eliminated. Knowing the initial drug concentration (mg./ml) and the patient breathing time on the system, the inhaled dose can be easily calculated, generally within ±12%. Conversely, if the desired inhaled dose is known, the same equation can be revised as follows to determine patient-breathing time required: 
   
     
       
         
           
             Breathing 
             ⁢ 
             
                 
             
             ⁢ 
             Time 
           
           = 
           
             
               Desired 
               ⁢ 
               
                   
               
               ⁢ 
               Patient 
               ⁢ 
               
                   
               
               ⁢ 
               Dose 
             
             
               
                 ( 
                 
                   drug 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   concentration 
                 
                 ) 
               
               ⁢ 
               
                 ( 
                 DMAR 
                 ) 
               
               ⁢ 
               
                 ( 
                 
                   system 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   efficiency 
                 
                 ) 
               
             
           
         
       
     
   
   Referring now to  FIG. 11A , an alternate form of the apparatus of the invention, which can be used with a conventional ventilator, is there shown. This apparatus is similar in many respects to that shown in  FIGS. 1 through 11  and like numerals are used in  FIG. 11A  to identify like components. As will be presently described, with proper placement in the breathing circuit this device can deliver drugs with essentially the same efficiencies as that previously described when used in conjunction with patients when connected to ventilators. In this latest embodiment of the invention, insert portion  22   d  with flapper valve  64  is omitted, and replaced with a valve means for controlling fluid flow between the outlet port OP of the ventilator through an inlet chamber  52   a  and into a baffle chamber  40   a  of housing  22   a . Baffle chamber  40   a  is provided with spaced-apart baffles,  46   a ,  48   a  and  50   a . Valve means  68 R, which is the reverse of valve  68 , functions to open and close a port  54   a  as needed for injection of pressurized air from the ventilator. This actuation of air pressure forces medicated air/oxygen from chamber  60   a  and chamber  40   a  through exit port  36   a  to the patient. Automatic operation of the ventilator circuitry is such that at such time air pressure from port OP of the ventilator is applied at port  34  an internal valve VV in the ventilator tightly closes the air exit tube from the patient, creating a completely closed circuit. Upon completion of the “inhalation” procedure, valve  68 R moves into its closed position, the ventilator valve VV of the ventilator opens and the expired air from the patient flows in the direction of the arrows through conduit  67  which is in communication with the patient. Upon closure of valve  68 R, newly generated aerosol once again fills chamber  40   a  thereby completing the cycle. 
   Turning next to  FIGS. 12 through 21  an alternate form of the aerosol inhalation apparatus of the invention is there shown and generally designated by the numeral  80 . This alternate form of the apparatus of the invention is similar in some respects to that shown in  FIGS. 1 through 11  and like numerals are used in  FIGS. 12 through 21  to identify like, components. As best seen by referring to  FIGS. 12 and 13 , this latest form of the apparatus can be seen to comprise a housing  82  which includes a generally cylindrically-shaped main body portion  84  having interconnected side and bottom walls  86  and  88  respectively. Attached to housing  82  is a nebulizer means, shown here as the previously identified, small volume nebulizer (SVN)  32  ( FIG. 12 ). A first end  82   a  of the main housing is provided with a standard size breathing port  90  for ready patient interfacing with the aerosol system. A second end  82   b  of the main housing is provided with an outlet port  92  to which filter means, such as the previously identified filter assembly  38  can be interconnected ( FIG. 13 ). 
   As best seen by referring to  FIGS. 13 and 20 , housing  82  includes a main portion  82   c  and a chamber defining, insert portion  82   d  which is received within main portion  82   c  in the manner shown in the drawings. The generally cylindrically-shaped portion  84  of housing  82  includes a first chamber  94  having an inlet  94   a  defined by an inlet port  96 , an outlet  98  and baffle means for providing a circuitous fluid flow path through the first chamber. In this latest form of the invention this important baffle means comprises a generally spiral-shaped wall  100  ( FIG. 20 ). Housing  82  also includes a second chamber  102  having an inlet  104  in communication with a first chamber  94  and an outlet  106  in communication breathing port  90 . 
   Insert portion  82   d  in cooperation with a housing top wall  110  defines a third chamber  112  chamber having an inlet  114  in communication with said second chamber  102  and an outlet  116 , which communicates with outlet port  92  via a first flow control means, here provided as a flapper valve mechanism  118 . 
   As shown in  FIG. 12 , nebulizer  32  is interconnected with inlet port  96  for communication with first chamber  94  for nebulizing a fluid medication containing the medicament to produce a particulate laden spray and for introducing said particulate laden spray into first chamber  94 . 
   A second flow control means, shown here as valve member  120 , is pivotally movable relative to inlet  98  of chamber  102  for controlling fluid flow through the inlet and into chamber  102 . 
   With the previous discussion of the theory of patient inhalation and dose quantification in mind, it can be seen that reservoir chamber  94  consists of a fixed, determinable volume. In practice, chamber  94  preferably has a volume of about 400 ml., which approximately equals the volume of aerosol produced by the nebulizer  32  during the time of patient exhalation under typical conditions such as an oxygen flow rate of about 7 liters per minute, a breathing rate of approximately 12 breaths per minute and an “in-out” ratio of about 1:2. 
   In using this latest form of the apparatus of the invention, upon patient exhalation, the second flow control means, here shown as a conventional, flapper-type valve member  120 , which is pivotally movable relative to inlet  104  of second chamber  102 , moves from the open position shown by the solid lines in  FIG. 13  into the closed position shown by the dotted lines in  FIG. 13 . With a valve member  120  closed, the aerosol, which has been newly generated by the nebulizer  32  flows into chamber  94  in the manner indicated by the arrows  125 . As the newly generated aerosol flows into chamber  94 , the residual air contained within the chamber will flow through the use or this flow path defined by spiral wall  100  in the manner indicated by the arrows  127  in  FIG. 13  (see also the arrows in  FIGS. 14 and 15 ) and will be pushed outwardly through exhaust port  92  in the manner indicated by the arrow  129  of  FIG. 13 . 
   In response to patient exhalation, valve member  118  is opened in the manner shown by the dotted lines in  FIG. 13 . At the same time, exhalation by the patient closes valve  120 . Simultaneously the nebulizer  32  is producing medicated aerosol, which replenishes the reservoir chamber, or chamber  94 . 
   In summary, due to the unique design of this alternate form of the apparatus of the invention, essentially all of the aerosolized medication (only loss—a relatively small percentage retained in the body of the device) is accessed by the, patient and the effects of patient breathing parameters are minimized or eliminated. Knowing the initial drug concentration (mg./ml) and the patient breathing time on the system, the inhaled dose can be easily calculated, generally within ±12%. Conversely, as discussed in connection with a first embodiment of the invention, if the desired inhaled dose is known, the same equation can be revised to determine patient breathing time required. 
   Having now described the invention in detail in accordance with the requirements of the patent statutes, those skilled in this art will have no difficulty in making changes and modifications in the individual parts or their relative assembly in order to meet specific requirements or conditions. Such changes and modifications may be made without departing from the scope and spirit of the invention, as set forth in the following claims.