Abstract:
An apparatus for use in respiratory therapy procedures in the field of medicine. The apparatus of the invention converts liquid medication into an aerosol mist comprising sub-micron size particles 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 will be delivered to the patient&#39;s lungs.

Description:
This is a continuation-in-part application of co-pending application Ser. No. 08/167,157 filed Dec. 16, 1993. 
    
    
     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 type of pulmonary diseases. Specific medications include beta 2  agonists, anticholinergies, cromolyn sodium, and steroids. More recently the aerosol method of delivery has been used to administer Pentamidine to patients afflicted with AIDS, and is presently under consideration as a delivery means for use in the treatment of cystic fibrosis 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 0.2 to 1 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) propellents. 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, Aug. 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, Aug. 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 3 to 5 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 optimum distribution throughout all of the lung area. 
     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 40% of the original dose of medication, this representing a three to five fold increase over presently available prior art aerosol systems. 
     Another object of the invention is to provide an apparatus of the aforementioned character which provides a mechanism whereby larger particles of medication will be entrapped and only properly sized particles will go forward so that all extremities of the lung area will effectively receive access to adequate medication. 
     Another object of the invention is to provide a novel inhalation device wherein particulate escape routes to atmosphere are minimized in instances where medication is used that should preferably be closely controlled or contained. 
     Another object of the invention is to provide an aerosol inhalation apparatus in which the liquid medication to be aerosolized can be easily and safely injected into the aerosol unit using a cannula and syringe. 
     Still another object of the invention is to provide an aerosol unit which includes a removable breathing tube which extends outward from the unit and terminates in a patient mouthpiece. 
     Yet another object of the invention is to provide means for safely filtering air exhaled from the patient before its release to room atmosphere. 
    
    
     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, cross-sectional view taken along lines 2--2 of FIG. 1. 
     FIG. 3 is a generally perspective, exploded view of the main housing of the apparatus. 
     FIG. 4 is a cross-sectional view taken along lines 4--4 of FIG. 2. 
     FIG. 5 is a cross-sectional view taken along lines 5--5 of FIG. 2. 
     FIG. 6 is a cross-sectional view taken along lines 6--6 of FIG. 2. 
     FIG. 7 is an enlarged, cross-sectional view taken along lines 7--7 of FIG. 6. 
     FIG. 8 is a cross-sectional view of an alternate form of filter for use in connection with the apparatus of the invention. 
     FIG. 9 is a side elevational view partly in cross section of an alternate form of the apparatus of the invention. 
     FIG. 10 is a generally perspective view of the one way valve embodied in the apparatus shown in FIG. 9. 
     FIG. 11 is a front view of the one way valve of FIG. 10, partly broken away to show the valve seat. 
     FIG. 12 is a side-elevational view partly in cross section of still another form of the apparatus of the invention. 
     FIG. 13 is a generally perspective view of the one way valve embodied in the apparatus shown in FIG. 12. 
     FIG. 14 is a front view of the one way valve of FIG. 13 partly broken away to show the valve seat. 
    
    
     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 can be seen to comprise a sectionalized main housing 12 to which is attached an inflatable bag 14, a bacteria filter 16, and nebulizer means, shown here as a small volume nebulizer (SVN) 18. As best seen in FIGS. 2 and 3, the upper half 18a of nebulizer 18 is enclosed within a first chamber 20 of the main housing 12 and the lower half 18b is disposed externally for ease of accessibility. A first end 12a of the main housing is provided with a standard size breathing port 22 for ready patient interfacing with the aerosol system via a conduit, or breathing tube 23. In a manner presently to be described, the various sections of chambers of the main housing are interconnected by appropriately baffled fluid flow passageways which are constructed and arranged in a manner to maximize the amount of aerosolized medication that is accessed by the patient. 
     Turning particularly to FIG. 2, the nebulizing means, or nebulizer 18 of the apparatus is mounted partially within first chamber 20 and functions to nebulize a selected fluid medication to produce a fine particle-laden spray having a precise range of sizes of medicament particles contained therewithin. Nebulizer 18 is of a standard construction well known to those skilled in the art, and as indicated in FIGS. 6 and 7, nebulizer 18 includes an upper cylindrical collar 24 and a lower liquid reservoir portion 26. 
     Carried by a wall 28 of housing 12, which is disposed directly above nebulizer 18, is access means for accessing nebulizer 18 to supply medication fluid to reservoir portion 26 thereof. In the embodiment of the invention shown in the drawings, the accessing means comprises a self-sealing, penetrable septum 30 which, as shown in FIGS. 3 and 6, is sealably mounted within an aperture 32 provided in top wall 28 of housing 12. For certain applications, septum 32 can also comprise a split septum adapted to receive a blunt cannula. Septum 30 is preferably constructed of soft rubber or other suitable elastomer material which is readily penetrable by a blunt cannula or by the needle &#34;N&#34; of a hypodermic syringe (FIG. 6). 
     Nebulizer 18 also includes a gas inlet means here comprising a gas inlet port 36, which is interconnected with a source of gas under pressure such as a tank &#34;T&#34; (FIG. 6). The nebulizer gas inlet means functions to permit the controlled introduction into the nebulizer of a selected gas under pressure in a manner to cause nebulizing of the fluid disposed within reservoir 26 of the nebulizer. This particulate containing fluid is generally designated in FIG. 6 by the letter &#34;F&#34; and may comprise any of a large number of medications, or mixtures thereof, depending upon the end use to be made of the apparatus. 
     In operating the nebulizer, the source of gas &#34;T&#34;, such as oxygen or compressed air, is interconnected, with inlet 36 by a suitable conduit &#34;C&#34; (see FIG. 6). The gas is preferably supplied to the nebulizer at a flow rate of about ten liters per minute. As best seen in FIGS. 6 and 7, the gas flowing through the inlet port in the direction of the arrow 37 passes through a very small nebulizer orifice 40 provided in a specially configured member 41. This causes the fluid &#34;F&#34; to be drawn from reservoir 26 through orifice 40 in the direction of the arrow 43. Due to the basic design of the nebulizer and in accordance with the Bernoulli effect, the liquid drawn from the reservoir will be predictably converted into a fine mist containing a mixture of particles of varying sizes. After flowing through orifice 40, the fine particulate-laden mist will be forced around a flow control member 44 and then upwardly through the nebulizer unit and into collar 24 in the direction of the arrows 45. Flow control member 44, which surrounds the outlet side of orifice 40 in the manner shown in FIG. 6, functions to increase turbulence within the nebulizer and to properly direct fluid flow toward collar 24. This novel construction reduces the size of the particles reaching the outlet port of the device and, along with settling means, the character of which will presently be described, limits the size of the particles that ultimately reach the patient. 
     As best seen in FIGS. 1 and 2, a reservoir means, shown here in the form of an inflatable bag 14 having a capacity of about two liters, is, secured by a ring clamp 48 to a cylindrically shaped port 50 which is integrally formed with bottom assembly 12b of housing 12. Port 50 communicates with a second chamber 54 which is formed in housing 12 adjacent first chamber 20. Housing 12 is also provided with a third chamber 56 which is in communication with an outlet port 56a to which there is connected a filtering means for impeding fluid flow through the outlet port and for filtering particles from the spray flowing into chamber 56 as a result of exhalation by the patient through the breathing tube or conduit 23. In the embodiment of the invention here shown, the filtering means comprises a filtering assembly 60 of the character best seen in FIG. 2. Assembly 60 includes a filtering element 62, which is retained within a housing 64, having neck portion 64a, and functions to filter particulates from the fluid flowing from chamber 56 through outlet port 56a, through filtering element 62 and outwardly of port 66 to atmosphere. Neck 64a is closely receivable over a cylindrical skirt 67 which forms a part of housing 12. Filtering element 62 is of a character well known to those skilled in the art and is commercially available from sources such as Intertech of Lincolnshire, Ill. 
     For so long as compressed air or oxygen is supplied to the nebulizer through inlet 36 and for so long as liquid remains within the nebulizer reservoir, a constant supply of medication containing mist will be supplied to first chamber 20. On average, a patient breathes approximately 10 to 12 times per minute and the adult tidal volume is in the order of 600 to 700 cc. Under normal patient dynamics, an inhalation breath will average approximately one second, and there is a retention time of on the order of one second, followed by an exhalation time of about three seconds. Using conventional small volume nebulizer (SVN) configurations, the patient is accessing aerosolized medication only during the inhalation period of perhaps one second. If the nebulizer is operating at 10 liters/min., during the one second inhalation period the patient will have received only 10,000 cc/60 sec.=167 cc of aerosolized medication with the remainder of the patient&#39;s tidal volume breath being composed essentially of room air. During patient retention and exhalation, the nebulizer output is being vented either through a filter or directly to the atmosphere. Accordingly, normal patient breathing dynamics severely limits the efficiency of conventional nebulizer circuits. 
     The novel apparatus of the present invention uniquely overcomes the drawbacks of prior art inhalation devices by substantially minimizing the loss of aerosolized medication during the exhalation phase of patient breathing. 
     As indicated in FIG. 2, during optimum system operations, nebulizer 18 is continually supplying a fine mist of aerosolized medication to first chamber 20 at a rate of approximately 167 cc per second. At the start of the treatment cycle, this mist is inhaled into the patient&#39;s lungs through a passageway 70a formed in a wall 70, which separates chambers 20 and 56, and via chamber 56 and conduit 23. During the following three second exhalation period, the expired air pushes a portion of the medication laden mist being generated from chamber 20 into chamber 54 and then into inflatable bag 14, with any excess expired air flowing to atmosphere through filter assembly 60. Uniquely, during the patient&#39;s next breath, medication laden mist is inhaled by the patient both from chamber 20 and from inflatable bag 14 in a volume sufficient to fully satisfy the patient&#39;s tidal volume requirements. This medication laden mist from chambers 20 and 54, goes into and is distributed through out the patient&#39;s lung area. During each subsequent breath, the process is repeated. Absent chambers 54 and inflatable bag 14, which is connected thereto, exhalation by the patient would cause a substantial portion of the medication laden mist being generated to be lost via filter 62 to atmosphere. 
     In addition to making more medication available to the patient and minimizing medication loss to atmosphere, chambers 20 and 56 also uniquely comprise settling means which function to remove large particles of medicaments from the particulate laden mist by means of sedimentation. In this connection, novel baffling means, of a character presently to be described, promote the effective entrapment of large particles with the result being that the particles actually being accessed by the patient are very small, as for example on the order of 0.3 microns MMAD. These particles are sufficiently small so that they desirably reach the extremities of the lung area through which medication is transported to The blood. 
     The previously mentioned baffling means of the invention comprise a first baffle means, or wall 72, which separates first and second chambers 20 and 54 as well as a wall 70, which separates first and third chambers 20 and 56. The settling means also comprises a settling chamber 20a which comprises a portion of first chamber 20 (FIG. 2). In operation, wall 72 functions to impede the flow of large particles toward second chamber 54 causing them to fall by force of gravity into settling chamber 20a. Similarly, wall 70 functions to impede the flow of large particles toward third chamber 56, once again causing the large particles traveling toward chamber 56 to fall by force of gravity into chamber 20a. 
     To vividly demonstrate the high levels of efficiency of the apparatus of the present invention, measurements have been made through use in the nebulizer chamber of radioactive labeled Tc 99m  DTPA. By sensing emissions from the radioactive particles that are actually deposited in the patients lungs, it has been shown that, if run to dryness, up to 40% of the fluid medication placed in the nebulizer reservoir will be delivered to the patient&#39;s lungs. 
     Turning now to FIG. 8, a filter assembly 80 of alternate construction to filter assembly 60 is there shown. Assembly 80 is receivable over skirt 67d of housing 12 and includes a filtering element 82 of different construction from that in element 62. More particularly, element 82 comprises a generally disk-shaped, relatively dense, porous mass adapted to capture particulate matter contained in the fluid flowing through outlet port 56a. Once again element 82 is of a character well known in the art and is readily commercially available. 
     Referring now to FIGS. 9, 10 and 11 an alternate form of inhalation apparatus of the present invention is there illustrated. This alternate form is similar in many respects to that shown in FIG. 2 and like numerals have been used to identify like components. A major difference between this latest form of the invention and that of FIG. 2 is the addition of novel valve means here provided in the form of a one way valve assembly 86 of novel construction which is disposed proximate passageway 71a. Another difference is the replacement of filter assembly 60 with a sealing cap 88 the function of which will presently be described. 
     As best seen in FIGS. 10 and 11, valve assembly 86 comprises a base wall 90 having central opening 92 therethrough. Affixed to wall 90 at a single pivot point 93 is a generally circular substantially flexible flapper valve member 94. Valve member 94 can be constructed of a number of materials including plastic and various yieldably deformable elastomeric materials. Pivot point 93 is defined by a fastener such as rivet 96 which passes through member 94 at a location proximate its outer periphery and then through base wall 90 in the manner shown in FIG. 9. With this unique construction, fluid passing through passageway 70 in the direction of the arrow 97 will flow through aperture 92 and will cause valve member 94 to open in a novel pivoting motion about pivot point 93. Conversely, fluid flowing in an opposite direction will cause valve member 94 to securely close and move into sealing engagement with a portion 90a of wall 90 that circumscribes opening 92 thereby blocking fluid flow through passageway 70a. 
     When the apparatus is in use, patient inhalation will cause the valve to open to permit the aerosolized medication to flow from chamber 20 into chamber 56 and then into the patient&#39;s lungs. During the time of patient breath hold and exhalation, the one-way valve will close causing mist produced during this period of time to be retained within chambers 20 and 54, and within the inflatable bag 14. This accumulation will fully satisfy the patient&#39;s next breath tidal volume requirements. Once again, this novel construction permits maximum effective use to be made of the particulate-laden mist being generated by the nebulizer. 
     In those situations where no harm results from exhalation of the particulate laden mist directly into the atmosphere, the filter means can be removed and replaced with the less expensive cap 88 which fits securely over cylindrical portion 67. Cap 88 is provided with a small, centrally disposed aperture 88a which permits flow to atmosphere and at the same time provides sufficient impedance to such flow as to insure proper closing of valve member 94 upon patient exhalation. 
     Turning next to FIGS. 12, 13, and 14, still another form of inhalation apparatus of the present invention is there illustrated. The alternate embodiment is similar in many respects to that shown in FIGS. 9, 10, and 11 and like numerals have been used to identify like components. A major difference between this latest form of the invention and that of FIGS. 9, 10, and 11 is the provision of a flow control means in the form of a volume balance diaphragm assembly 102 of novel construction which is disposed proximate passageway 71a. 
     As best seen in FIGS. 13 and 14, diaphragm assembly 102 comprises a base wall 104 having central opening 106 therethrough. Affixed to wall 104 at a single pivot point 107 is a generally circular, substantially flexible diaphragm member 110. Diaphragm member 110 can be constructed of several materials including plastic and various yieldably deformable elastomeric materials. Pivot point 107 is defined by a fastener, such as rivet 112, which passes through member 110 at a location proximate its outer periphery and then through base wall 104 in the manner shown in FIG. 12. In this latest embodiment of the invention, member 110 is provided with an aperture 114. Aperture 114 is in communication with passageway 71a and permits limited fluid flow between reservoir bag 14 and breathing port 22 even when member 110 is in a closed position. This novel construction enhances movement of generated mist to reservoir bag 14 and, in a manner presently to be described, insures uniformity of available medication for the ensuing patient breathing cycle. Further, the provision of aperture 114 in member 110 assists in balancing the available medication. 
     Although incorporation within the structure of the volume balancing diaphragm, or apertured member 110, does not materially affect particle size reaching the patient, it helps provide a balance of air volume when comparing inhaled mist to that which is generated by the nebulizer. For example, if the nebulizer is operated with an oxygen flow rate of 8 liters per minute, a total volume of 8 liters of medication-laden mist would, of course, be produced in a one minute time frame. If the patient breathing rate multiplied by his normal tidal volume approximates 8 liters/minute, he will utilize essentially all of the available medication. However, in most clinical situations, if a patient breathes relatively deeply he will take fewer breaths per minute. Conversely, a shallow breather must take more breaths. Nevertheless, on average, the volume remains relatively constant. Additionally, expired air from the patient contains a substantial amount of original medication, the concentration of which is inversely related to depth of patient breathing. By using a portion of the expired air (rather than room air) as a diluent with the newly generated aerosol mist, drug concentration for the next breathing cycle is selectively enhanced. Thusly, through control of the air/mist with the volume balancing diaphram 110, the amount of aerosol delivered to the patient over a period of time is essentially independent of differences in patient breathing parameters and can therefore be reasonably quantified. 
     In practice, the size of aperture 114 can be varied, but experience has shown that an aperture size of on the order of two to three millimeters is satisfactory in dispensing most medicaments. In any event, the benefit of the volume balancing, flow control means, as described in the preceding paragraphs, enables a more uniform availability of aerosol covering a group of patients having widely differing breathing parameters. 
     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.