Patent Publication Number: US-2020282158-A1

Title: Spacer

Description:
FIELD OF INVENTION 
     The present invention relates to an inhalation spacer. The present invention relates to an inhalation spacer which is of particular, but not exclusive, use with pressurised metered dose inhaler (pMDI) devices. 
     BACKGROUND 
     It is known to provide inhalation spacers for use with medical inhaler devices, in particular pressurised metered dose inhaler (pMDI) devices. Spacers provide a large-volume air flow-path between the outlet of an inhaler device and the mouth of a patient. 
     By providing such an air flow-path between an inhaler device and the mouth of the patient, delivery of aerosolized medication into the lungs of a user is improved. 
     Spacers slow the speed at which the aerosolized medication enters the mouth of a patient, preventing the medication from striking the back of the mouth. A low-velocity plume of aerosolized medication is therefore allowed to develop in the air flow-path. Low velocity plumes of aerosolized medication are known to be most effective for delivery deep into the lungs, maximising the delivered dose of medication. 
     Without wishing to be bound by theory, it is considered that large particles of aerosolized medication (typically &gt;5 μm in diameter) are non-respirable. Particles of this size either evaporate into smaller particles when the low-velocity plume forms in the air flow-path, or coalesce and precipitate. 
     The aerosolized plume of medication can remain in the large-volume air flow path of the spacer for a number of seconds before being inhaled, thereby eliminating the need for the user to accurately coordinate the ejection of aerosolized medication from a drug reservoir with inhalation. This coordination can be particularly challenging for children and the elderly. Advantageously, a user can also inhale more slowly when using a spacer. 
     Inhalation spacers are conventionally made from plastic. However, plastic spacers can carry static charge. Build-up of static charge in such spacers is problematic, because aerosolized medications are attracted to the static charge, causing them to adhere to the inner walls of the spacer by electrostatic attraction. The dose of medication delivered to the lungs is therefore reduced. In order to ameliorate the problem of static attraction, plastic spacers are often primed with several dosages of an aerosolised medication. This process is wasteful. 
     Traditional plastic spacers are generally large, and as such are only used in the home or in medical practices. They are rarely used ‘on the move’, and so compliance is poor. 
     In more recent years, various collapsible paper spacers have been developed. The LiteAire® spacer from Thayer, and the Livingstone™ spacer, are two such examples of collapsible paper spacers. 
     These paper spacers are collapsible for storage, and have a small-volume flow-path (typically up to 200 mL). They are therefore more portable than conventional plastic spacers. However, the small volume of these known paper spacers does not support formation of an effective low-velocity plume. 
     A significant drawback with known collapsible paper spacers is that they have low durability. In particular, they are made of paperboard materials which have a low folding endurance (i.e. are susceptible to cracking from repeated folding). They are therefore sold as disposable spacers, for use over short periods of time (typically up to a week). The known paper spacers are perforated in order to provide fold-lines. These perforations create weak points in the product, thereby reducing durability. 
     The present invention aims to provide a spacer which reduces, ameliorates, or even eliminates one or more of the problems of low medical efficacy, low portability, and low durability. 
     SUMMARY OF INVENTION 
     In a first aspect, the present invention provides an inhalation spacer movable between a collapsed configuration (e.g. for storage) and an expanded configuration (e.g. for use with an inhaler device), wherein the spacer is made from paperboard having a bending stiffness of at least 2.5 mNm. 
     The inventor has found that paperboard having a bending stiffness of 2.5 mNm) can be used to form a spacer which can be moved between its collapsed and expanded configurations repeatedly (e.g. hundreds, or even thousands, of times) without becoming damaged, e.g. without forming cracks along lines along which it is folded. 
     Bending stiffness is a measure of the stiffness of paperboard when bent. It may be measured using standardised test ISO 5628:2012. Bending stiffness is commonly measured using a Messmer-Buehler stiffness tester by measuring the force required to bend a single layer of paperboard by 5°. 
     In some embodiments, the bending stiffness of the paperboard may be at least 3 mNm or at least 3.5 mNm, e.g. at least 3.7 mNm. 
     The bending stiffness of the paperboard may be at most 85 mNm. For example, the bending stiffness of the paperboard may be at most 80 mNm, e.g. at most 77.9 mNm. 
     The paperboard may have a bending stiffness of between 5 and 40 mNm. 
     The fibres of the paperboard may have a generally laminar orientation. The direction parallel to the laminar orientation of the fibres may be referred to as the ‘machine direction’. The direction perpendicular to the laminar orientation of the fibres may be referred to as the ‘cross direction’. 
     The paperboard may have a first bending stiffness in the machine direction and a second bending stiffness in the cross direction. 
     The first bending stiffness may be higher than the second bending stiffness. 
     The first bending stiffness may be at least 5 mNm. In some embodiments, the first bending stiffness is at least 8 mNm, e.g. at least 8.2 mNm. 
     The first bending stiffness may be at most 80 mNm, e.g. at most 77.9 mNm. In some embodiments, the bending stiffness in the machine direction may be between 35 mNm and 40 mNm, e.g. around 38.5 mNm. 
     The second bending stiffness may be at least 2.5 mNm, e.g. at least 3 mNm, or even at least 3.7 mNm. The second bending stiffness may be at most 40 mNm, e.g. at most 34 mNm. In some embodiments, the bending stiffness in the cross direction may be between 15 mNm and 20 mNm, e.g. around 16 mNm. 
     The paperboard may have a bending moment of at least 1 mNm, e.g. at least 1.4 mNm. Preferably, bending moment is determined by measuring the bending moment required to bend paperboard by an angle of e.g. 15°. Measurement of bending moment is done using a Taber stiffness tester (ISO 2493). The bending moment of the paperboard may be at least 2 mNm, e.g. at least 2.2 mNm. The bending moment may be at most 45 mNm, e.g. less than 40 mNm. In some embodiments, the bending moment of the paperboard may be between 1 and 20 mNm. 
     The paperboard may have a first bending moment in the machine direction and a second bending moment in the cross direction. 
     The first bending moment may be higher than the second bending moment. 
     The first bending moment may be at least 3 mNm. The first bending moment may be at least 4.4 mNm, e.g. at least around 4.6 mNm. 
     The first bending moment may be at most 45 mNm. The first bending moment may be at most 40 mNm. In some embodiments, the first bending moment may be between 17 and 22 mNm, e.g. around 20 mNm such as around 19.6 mNm. 
     The second bending moment may be at least 1 mNm. The second bending moment may be at least 1.4 mNm, e.g. at least 2 mNm, or even at least 2.2 mNm. The second bending moment may be at most 20 mNm, e.g. at most 19 mNm. In some embodiments, the second bending moment may be between 5 mNm and 10 mNm, e.g. around 9 mNm such as around 8.7 mNm. 
     The paperboard may have a tensile strength of at least 9 kN/m, e.g. at least 9.5 kN/m. The paperboard may have a tensile strength of at most 35 kN/m, e.g. at most 31.5 kN/m. Tensile strength may be determined according to the standardised test ISO 1924-2:2008, which provides a measure of the elastic elongation of the paperboard under tensile force. 
     The paperboard may have a first tensile strength in the machine direction and a second tensile strength in the cross direction. 
     The first tensile strength may be higher than the second tensile strength. 
     The paperboard may have a first tensile strength of at least 15 kN/m. The paperboard may have a first tensile strength of at least 17 kN/m, e.g. at least 18.5 kN/m. The paperboard may have a first tensile strength of at most 35 kN/m, e.g. at most 32 kN/m. In some embodiments, the paperboard may have a first tensile strength of between 20 kN/m and 30 kN/m, e.g. around 25 or 25.5 kN/m. 
     The paperboard may have a second tensile strength of at least 7 kN/m. The paperboard may have a second tensile strength of at least 9 kN/m, e.g. around 10 kN/m. The paperboard may have a second tensile strength of at most 15 kN/m, e.g. at most 14.5 kN/m. In some embodiments, the paperboard may have a second tensile strength of between 10 kN/m and 15 kN/m, e.g. around 12.5 kN/m. 
     The paperboard may have a first tearing resistance in the machine direction and a second tearing resistance in the cross direction. 
     The first and/or second tearing resistance may be at least 1800 mN, e.g. at least 2000 mN, or at least 2300 mN. The first and/or second tearing resistance may be at most 6500 mN, e.g. at most 6400 mN. In some embodiments, the paperboard may have a first tearing resistance of around 4300 mN. In some embodiments, the paperboard may have a second tearing resistance of around 4600 mN. Tearing resistance may be measured according to the standardised test ISO1974:2012, by measuring the tensile force required to tear a single layer of the paperboard. 
     References herein to paperboard mean a fibrous, paper-based material with an area density of at least 150 g/m 2 . The unit of g/m 2  may alternatively be referred to as ‘grammage’. 
     The paperboard may have an area density of at least 180 g/m 2 , e.g. at least 200 g/m 2 . The paperboard may have an area density of at most 995 g/m 2 , e.g. at most 680 g/m 2 , e.g. at most 500 g/m 2 , such as at most 400 g/m 2 . In some embodiments, the paperboard may have an area density of around 300 g/m 2 . 
     The paperboard may comprise a single layer or may comprise multiple layers affixed (e.g. glued) together such that the paperboard has a laminated structure. The individual layers in the laminate structure may have the same or different properties e.g. the same or different area density. In the case of the multi-layer laminate paperboard, the defined bending stiffness, bending moment, tensile strength, tearing resistance and area density is for the laminated structure rather than for each individual layer within the laminated structure. 
     The paperboard may have a thickness of at least 200 μm, such as at least 230 μm. The paperboard may have a thickness of at most 600 μm, e.g. at most 510 μm. In some embodiments, the paperboard may have a thickness of around 395 μm. The fibres of the paperboard may have a fibre length of between 0.8 and 4.5 mm. In some embodiments, the fibres of the paperboard have fibre length between 0.9 and 3.5 mm. 
     In some embodiments, the paperboard comprises fibres having a length between 0.9 and 1.2 mm and/or fibres having a length between 2 and 3 mm and/or fibres having a length between 3.1 and 3.5 mm. 
     The paperboard may comprise fibres derived from a plurality of different wood sources. The fibres derived from each wood source may have a different length from one another. 
     For example, the paperboard may comprise fibres having a length between 0.9 and 1.2 mm derived from a first wood source and/or fibres having a length between 2.0 and 3.0 mm derived from a second wood source and/or fibres having a length between 3.1 and 3.5 mm derived from a third wood source. 
     The paperboard may comprise fibres derived from Spruce and/or Pine and/or Birch. In some embodiments, the paperboard comprises Spruce and Pine fibres. 
     For example, the paperboard may comprise fibres having a length between 0.9 and 1.2 mm derived from Birch and/or fibres having a length between 2 and 3 mm derived from Pine and/or fibres having a length between 3.1 and 3.5 mm derived from Spruce. 
     The fibres may have a width of greater than 15 microns e.g. equal to or greater than 19, 20 or 22 microns. The fibres may have a maximum width of 50 microns e.g. a maximum width of 35 microns. 
     For example, in some embodiments, the paperboard comprises fibres having a length between 0.9 and 1.2 mm and a width between 20 and 35 microns and/or fibres having a length between 2 and 3 mm and a width between 22 and 50 microns and/or fibres having a length between 3.1 and 3.5 mm and a width between 19 and 50 microns. 
     The fibres may be primary fibres (otherwise known as virgin fibres). Accordingly, the paperboard may be virgin paperboard. In some embodiments, the paperboard does not contain any recycled fibres. 
     The fibres may be chemically pulped fibres. In particular, the paperboard may be formed from a chemical pulping process, e.g. from the chemical pulping of wood chips. In some embodiments, the chemical pulping process used is sulphate chemical pulping. 
     The fibres of the paperboard may be bleached. In particular, the pulp obtained by the chemical pulping process may be bleached. Accordingly, the paperboard may be solid bleached board (SBB) paperboard. 
     Pulping and bleaching processes may collectively remove 80-90% of lignin from the raw material. 
     Accordingly, the paperboard may comprise up to 10% by mass, e.g. up to 5% by mass, of lignin. The paperboard may comprise at least 70% by mass of cellulosic fibres, and a balance of other plant-originating and/or non-plant-originating materials. 
     The cellulosic fibres may comprise cellulose fibres, and hemicellulose fibres. In this case, the paperboard may comprise at least 45% by mass of cellulose, e.g. at least 50% by mass of cellulose. The paperboard may comprise at least 25% by mass of hemicellulose, e.g. at least 30% by mass of hemicellulose. 
     At least one (and optionally both) surfaces of the paperboard may comprise at least one coating layer. 
     The coating layer may be a water-resistant (e.g. waterproof) layer. 
     The coating may be a pigmented (e.g. white) coating to provide a surface suitable for printing. 
     For example, the coating layer (e.g. the water-resistant coating layer) may comprise a clay or mineral material such as china clay and/or calcium carbonate. It may further comprise a binder material e.g. starch, soy protein or an acrylate binder. 
     The coating may be an anti-static coating. 
     The balance of non-plant-originating materials mentioned above may include the material of the coating layer. 
     The spacer has a collapsed and expanded configuration, meaning that the spacer is significantly more portable than known plastic spacers. Furthermore, by providing a spacer made of paperboard (which does not readily carry electrostatic charge), the present invention significantly reduces the problem of aerosolized medication adhering to the spacer (e.g. to the inner surfaces of the spacer). 
     The spacer may have a substantially flat profile in the collapsed configuration. The total external volume of the spacer in the collapsed configuration may be less than 10% of the total external volume of the spacer in the expanded configuration. The total external volume of the spacer in the collapsed configuration may be less than 5% of the total external volume of the spacer in the expanded configuration. 
     In the expanded configuration, the spacer may have an internal cavity, the internal cavity providing an air flow-path between an inlet aperture and an outlet aperture. The internal cavity may have a volume of 500 mL or more in the expanded configuration. The internal cavity may have a volume of 1000 mL or less e.g. 750 mL or less in the expanded configuration. 
     The inventor has found that an internal cavity volume of between 500 mL and 1000 mL provides a good balance between medical efficacy and portability. 
     The volume of the internal cavity in the collapsed configuration may be less than 10% of its volume in the expanded configuration. The volume of the internal cavity in the collapsed configuration may be less than 5% of its volume in the expanded configuration. 
     The volume of the internal cavity in the collapsed configuration may be less than 50 mL. The volume of the internal cavity is substantially zero in the collapsed configuration. In other words, there may be effectively no internal cavity in the collapsed configuration. 
     The spacer may have a length, measured from the inlet aperture to the outlet aperture, of at least 5 cm. The length may be at least 7.5 cm e.g. at least 10 cm. 
     The inlet aperture may be configured for engagement with a mouthpiece of a medical inhaler device. In particular, the inlet aperture may comprise a recess portion for intimate, e.g. substantially air-tight, engagement with the mouthpiece of an inhaler device. 
     The outlet aperture may be configured for engagement with the mouth of a patient/user. In particular, the size of the outlet aperture may be selected so that a user can place his/her mouth over the outlet aperture to inhale. 
     In some embodiments, the inlet and outlet apertures are located at opposing axial ends of the spacer from each other. 
     The internal surface of the spacer, e.g. the internal surface of the internal cavity, may comprise the coating layer. In some embodiments, the entire internal surface of the internal cavity comprises the coating layer (as described above). 
     The outer surface of the spacer may comprise the coating layer. In some embodiments, the entire outer surface of the spacer comprises the coating layer (as described above). 
     The spacer may comprise upper and lower portions defining the air flow-path, and first and second axial end portions located at respective axial ends of the air flow-path (e.g. defining the axial ends of the internal cavity). The inlet aperture may be formed in the first axial end portion, and the outlet aperture may be formed in the second axial end portion. 
     All of the upper and lower and two axial end portions may be formed from a single piece (blank) of folded paperboard. 
     The upper and lower portions may have a substantially rectangular or square profile and are joined to one another along their opposing lateral edges. One join between the lateral edges of the upper and lower portions may be a fold and one may be an adhesively-connected join. 
     In the expanded configuration each of the upper and lower portions is convex, the convexity of the upper and lower portions defining the internal cavity. 
     In the expanded configuration, the convexity of the upper and lower portions may be maintained by concave axial end portions, the concave axial end portions having a profile which is substantially a mandorla-shape. For each of the axial end portions, one of the opposing mandorla edges will be connected/joined to the axial edge of the upper portion and the other to the axial edge of the lower portion. 
     The joins between the axial end portions and the upper/lower portions may be folded joins or may be adhesively-connected joins. 
     In the collapsed configuration, the upper and lower portions may be planar and may overlay one another. In the collapsed configuration, the axial end portions may be laterally folded i.e. with a fold (either inwards or outwards) along an edge/join between the axial end portions and the upper/lower portions, and/or a fold between the apices of the mandorla shape. 
     In this way, the spacer has a substantially flat profile in the collapsed configuration. 
     In some embodiments, the air flow path has a constant internal cross-section from the inlet aperture to the outlet aperture. Similarly, the external cross-sectional profile of the spacer, from the first axial end portion to the second axial end portion, may be constant. The cross-sectional profile of the air flow path/spacer may match the profile of the axial end portions e.g. it may be mandorla-shaped. 
     The air flow-path between the inlet aperture and the outlet aperture may be uninterrupted. In particular, the spacer may comprise a single, continuous internal cavity extending from the inlet aperture to the outlet aperture. In these embodiments, there is no valve or obstruction provided in the air flow-path. 
     The spacer may be expandable by forcing the first and second axial end portions towards each other (e.g. into their concave profile), thereby forcing the upper and lower portions away from each other (e.g. into their convex profile) to form the internal cavity. 
     The spacer may be collapsible by forcing the upper and lower portions towards each other (e.g. into a planar, overlaying arrangement), thereby folding the axial end portions to eliminate the internal cavity. 
     In some embodiments, the spacer is packaged (e.g. for sale) and distributed in the collapsed configuration, and transported by a user in the collapsed configuration. 
     Creases may be provided in the paperboard, to provide folding points (e.g. fold lines, or hinges) about which the spacer is movable between the collapsed and expanded configurations. In particular, the creases may provide fold-lines, e.g. along the joins between the upper, lower and axial end portions. 
     In some embodiments, the creases are provided at the joins between the upper portion, lower portion, first axial end portion, and second axial end portion of the spacer. In particular, the creases may be located at the edges of the spacer in the expanded configuration. 
     Each crease may have the appearance of a corrugation, or furrow, in the surface of the paperboard. In some embodiments, the creases do not include perforations. 
     The creases may each have width of between 0.8-1.5 mm, such as between 0.9-1.4 mm. The creases may each have a depth of between 0.4-0.8 mm, such as between 0.5-0.7 mm. 
     In some embodiments, the creases may each have a width of around 1 mm (e.g. around 1.2 mm), and a depth of around 0.5 mm (e.g. around 0.6 mm). 
     Alternatively, fold-lines may be provided by score-lines in a surface of the paperboard. 
     In some embodiments, the paper spacer is formed from a single paperboard blank. In other words, the paper spacer may be formed from a single piece of paperboard, joined to itself at opposing edges to form the spacer of the first aspect. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       Embodiments of the invention are set out below in detail, with reference to the accompanying drawings, in which: 
         FIG. 1 a    shows a microscope image of Spruce fibres. 
         FIG. 1 b    shows a microscope image of Birch fibres 
         FIG. 1 c    shows a microscope image of Pine fibres. 
         FIG. 1 d    shows a microscope image of a blend of Spruce, Pine and Birch fibres. 
         FIG. 2  is a schematic illustration of the composition of SBB paperboard. 
         FIG. 3  shows an outline of a paperboard spacer blank used to manufacture a spacer of the present invention. 
         FIG. 4  shows a method of forming creases in a paperboard spacer blank. 
         FIG. 5  shows a spacer of the present invention, in a collapsed configuration. 
         FIG. 6 a    shows a perspective view of the spacer of  FIG. 5 , in the expanded configuration. 
         FIG. 6 b    shows an end-view of the spacer of  FIGS. 5 and 6   a , in the expanded configuration. 
         FIG. 7  shows an end-view of a spacer according to an embodiment of the present invention. 
         FIG. 8  shows an end-view of a spacer according to an embodiment of the present invention. 
         FIG. 9  shows a perspective view of the  FIG. 8  spacer. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description of embodiments of the present invention is made by way of example. On reading this disclosure, modifications of the embodiments that fall within the scope of the invention will be apparent. 
     Manufacture of the paperboard used to form the inhalation spacer according to an embodiment of the present invention will first be described. 
     The paperboard comprises a mixture of Spruce, Pine and Birch fibres. These species of tree grow well in cold climates, and have a far longer average fibre length than trees that grow in warmer climates.  FIGS. 1 a , 1 b  and 1 c    show microscope images of Spruce, Birch and Pine fibres (respectively). The length of the fibres can be clearly seen. The fibres are extracted from Pine, Birch and Spruce sourced from Scandinavia and northern Europe, where average year-round temperatures are low. Low temperatures further contribute to the fibres being long.  FIG. 1 d    shows a microscope image of a blend of Pine, Spruce and Birch fibres. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Fibre length, width and shape 
               
            
           
           
               
               
               
               
            
               
                 Species 
                 Fibre length (mm) 
                 Fibre width (μm) 
                 Fibre shape 
               
               
                   
               
               
                 Spruce 
                 3.1-3.5 
                 19-50 
                 Ribbon-like, flat 
               
               
                 Pine 
                 2-3 
                 22-50 
                 Ribbon-like, flat 
               
               
                 Birch 
                 0.9-1.2 
                 20-35 
                 Cylindrical, 
               
               
                   
                   
                   
                 pointed ends 
               
               
                   
               
            
           
         
       
     
     The raw wood product is first de-barked, and formed into wood chips. 
     The fibres are extracted from the raw wood material by a combination of sulphate chemical pulping, and bleaching. These processes remove 80-90% of lignin (which would otherwise affect the foldability and folding endurance of the paperboard), leaving a white (colourless) pulp consisting mainly of cellulose and hemicellulose fibres. 
     Waste products, e.g. bark and lignin, can be used in energy generation, in order to avoid wasting the raw material. 
     Once extracted, the pulp is suspended in water, to a concentration of at least 1% (1 part pulp fibres, to 99 parts water). The pulp suspension is then allowed to settle onto a wire mesh, to form multiple layers of fibres. Once the desired thickness of fibres has formed on the mesh, they are dried, and vacuum-pressed. The paperboard material is then pressed and dried. This process encourages the fibres bind to each other in the paperboard, forming an interlocking fibrous network. The binding is helped by the presence of hemicellulose fibres. The fibres give the paperboard excellent folding endurance, withstanding up to 2,700 folds before becoming permanently damaged, e.g. before forming cracks along fold-lines. In other words, the fibres improve foldability and folding endurance. 
     The resulting product is solid bleached board (SBB) paperboard, which comprises multiple laminar layers of high-purity cellulose and hemicellulose fibres. 
     This SBB paperboard is pure, hygienic, safe for medical applications, and compliant with European Union and American food contact regulations. It conforms to the good manufacturing practices (GMP) for food, drug products and pharmaceuticals. It is also approved for use with foods by the food standards agency (FSA). 
     The SBB paperboard does not contain recycled or mechanically pulped fibres. The process used to recycle paper-based products causes a reduction in fibre length. By using virgin, or primary, fibres for the paperboard (rather than recycled fibres), maximum fibre length (and hence maximum folding endurance) is achieved. Also, by using chemical pulping rather than mechanical pulping, reduction in fibre length is avoided. 
     Finally, the outer surfaces of the SBB paperboard are coated with a ceramic coating layer, typically china clay and/or calcium carbonate. The coating layer enables high-quality graphics to be printed onto the SBB paperboard, by preventing ink bleed. Advantageously, the coating layer is water-resistant so that the spacer can be easily cleaned, e.g. wiped down, thereby improving hygiene of the product such that it is suitable for repeated use in medical applications. 
       FIG. 2  shows a schematic illustration of the SBB paperboard, with a central laminated bleached chemical pulp layer  300  sandwiched between coating layers  302 . The inventor has found that paperboard with an area density of between 180 g/m 2  to 400 g/m 2  e.g. around 300 g/m 2  gives a suitable foldability and folding endurance. 
     Properties of the paperboard (e.g. SBB paperboard) used in embodiments of the present invention will now be described. 
     The fibres in paperboard materials tend to have a generally laminar orientation, in the plane of the paperboard. Reference herein to the machine direction means in a direction parallel to the laminar orientation of the fibres. Reference herein to cross direction in means in a direction perpendicular to the laminar orientation of the fibres, i.e. perpendicular to the machine direction. 
     Specific mechanical properties for a particular SBB paperboard ranging from 180 g/m 2  to 380 g/m 2  are given in Table 2, below. The inventor has found that paperboard with an area density of 300 g/m 2  has a particularly desirable combination of foldability and folding endurance for use in the present invention. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Tensile strength and tearing resistance of SBB paperboard 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Grammage (g/m 2 ) 
                 180 
                 200 
                 220 
                 240 
                 260 
                 280 
                 300 
                 330 
                 350 
                 380 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Thickness (μm) 
                 205 
                 235 
                 260 
                 300 
                 330 
                 360 
                 395 
                 435 
                 465 
                 505 
               
               
                 Bending stiffness 
               
               
                 (mNm) 
               
               
                 Machine direction 
                 5.5 
                 8.2 
                 11.9 
                 16.2 
                 20.8 
                 29.9 
                 38.5 
                 50.8 
                 61.8 
                 77.9 
               
               
                 Cross direction 
                 2.5 
                 3.7 
                 5.4 
                 7.5 
                 9.7 
                 12.5 
                 16 
                 21 
                 25 
                 31 
               
               
                 Bending Resistance 
               
               
                 (mN) 
               
               
                 Machine direction 
                 65 
                 95 
                 140 
                 190 
                 245 
                 315 
                 4.5 
                 550 
                 650 
                 820 
               
               
                 Cross direction 
                 30 
                 45 
                 64 
                 83 
                 107 
                 137 
                 180 
                 230 
                 275 
                 345 
               
               
                 Bending moment 
               
               
                 Taber (mNm) 
               
               
                 Machine direction 
                 3.1 
                 4.6 
                 6.8 
                 9.2 
                 11.8 
                 15.2 
                 19.6 
                 26.5 
                 31.4 
                 39.6 
               
               
                 Cross direction 
                 1.4 
                 2.2 
                 3.1 
                 4 
                 5.2 
                 6.6 
                 8.7 
                 11.1 
                 13.3 
                 16.7 
               
               
                 Tensile strength 
               
               
                 (kN/m) 
               
               
                 Machine direction 
                 17 
                 18.5 
                 20 
                 21.5 
                 23 
                 24 
                 25.5 
                 28 
                 29.5 
                 31 
               
               
                 Cross direction 
                 9.5 
                 10 
                 10.5 
                 11 
                 11.5 
                 12 
                 12.5 
                 13.5 
                 14 
                 14.5 
               
               
                 Tearing resistance 
               
               
                 (mN) 
               
               
                 Machine direction 
                 2000 
                 2300 
                 2700 
                 3100 
                 3300 
                 3700 
                 4300 
                 4700 
                 5200 
                 6400 
               
               
                 Cross direction 
                 2000 
                 2350 
                 2800 
                 3300 
                 3600 
                 4000 
                 4600 
                 5100 
                 5600 
                 6400 
               
               
                   
               
            
           
         
       
     
     Bending stiffness values are given in the table above. The inventor considers that bending stiffness is a particularly important property for achieving high foldability, folding endurance, and creasibility, of the paper spacer of the present invention. 
     In particular, foldability is defined according to equation 1, below. As can be seen, foldability depends on mending moment, in addition to bending stiffness. As bending stiffness increases, so does foldability. Foldability is a dimensionless unit. 
       Foldability=bending stiffness/bending moment 
     Table 3 below shows foldability values of paperboard suitable for use in the spacer of the present invention. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Foldability of SBB paperboard between 180 g/m 2  and 380 g/m 2 . 
               
            
           
           
               
               
               
            
               
                   
                 Foldability 
                   
               
            
           
           
               
               
               
            
               
                 Grammage (g/m 2 ) 
                 Machine direction 
                 Cross direction 
               
               
                   
               
               
                 180 
                 1.77 
                 1.79 
               
               
                 200 
                 1.78 
                 1.68 
               
               
                 220 
                 1.75 
                 1.74 
               
               
                 240 
                 1.76 
                 1.88 
               
               
                 260 
                 1.76 
                 1.87 
               
               
                 280 
                 1.97 
                 1.89 
               
               
                 300 
                 1.96 
                 1.84 
               
               
                 330 
                 1.92 
                 1.89 
               
               
                 350 
                 1.97 
                 1.88 
               
               
                 380 
                 1.97 
                 1.86 
               
               
                   
               
            
           
         
       
     
     A method by which the spacer of the present application may be produced (e.g. using the paperboard disclosed above) will now be described. 
     To form the spacer, the paperboard is first formed into a plurality of paperboard spacer blanks.  FIG. 3  shows a plan view of the outline of a single paperboard spacer blank. The outline of the blank is shown in solid lines. 
     The paperboard is stamped, or cut, along the solid lines to form the paperboard spacer blank. Preferably, where the spacer is to be mass-produced, multiple blanks may be stamped out from a single piece of paperboard, using one or more cutting die/stamp. 
     Once a paperboard spacer blank has been cut, creases are formed in it. Creases significantly increase the foldability of the paperboard by providing fold-lines, or hinges, about which the paperboard will preferentially fold when manipulated by a user. Creases  112 ,  118 ,  120  are illustrated with dotted lines in  FIG. 3 . The creases are formed in the paperboard of the spacer to form fold lines about which the spacer can be expanded and collapsed. When expanded, these creases form the edges of the spacer. 
     Without wishing to be bound by theory, it is thought that the bending moment of the paperboard is significantly reduced in the region of the crease, which encourages the paperboard to bend along the crease. In this way, the foldability is increased. A ‘folding factor’, which provides an indication of how easy a piece of paperboard is to fold after formation of a crease, is dependent on the bending moment. 
       Folding factor=(( M (uncreased)− M (creased))/ M (uncreased))×100%
 
     where M is the bending factor. 
     The folding factor is effectively a measure of the change in bending moment (M) of a piece of paperboard before and after formation of a crease. 
     It is also considered that delamination of the laminar layers of fibres in the SBB paperboard help to increase foldability. By delaminating, the layers are able to move over each other more readily, thereby allowing the paperboard to bend. 
     The creases are formed by applying pressure to an upper portion of the paperboard spacer blank, thereby forming ridges/corrugations in the paperboard spacer blank. The creases do not include perforations. 
     The basic method used to form the creases in the paperboard spacer blank is shown in  FIG. 4 . Elongate creasing rule  200  is brought into contact with the paperboard, and pressure is applied to force the paperboard into a recess  202 . A crease is thereby formed. For mass-producing the spacer product, the creasing rule  200  and recess  202  are provided in a die having a male part (carrying the creasing rule) and a female part (carrying the recess). When brought into contact, the creasing rule of the die engages the recess, to form the creases  112 ,  118 ,  120  as shown in  FIG. 3 . 
     By combining high foldability with an appropriate crease depth, excellent folding performance is achieved. Appropriate crease dimensions (width and depth) are given in Table 4. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Crease dimensions 
               
            
           
           
               
               
               
            
               
                 Paperboard thickness (μm) 
                 Crease width (mm) 
                 Crease depth (mm) 
               
               
                   
               
               
                 205 
                 0.9 
                 0.5 
               
               
                 235 
                 1.0 
                 0.5 
               
               
                 270 
                 1.0 
                 0.5 
               
               
                 300 
                 1.0 
                 0.5 
               
               
                 330 
                 1.1 
                 0.5 
               
               
                 360 
                 1.2 
                 0.6 
               
               
                 395 
                 1.2 
                 0.6 
               
               
                 435 
                 1.3 
                 0.6 
               
               
                 465 
                 1.3 
                 0.6 
               
               
                 505 
                 1.4 
                 0.7 
               
               
                   
               
            
           
         
       
     
     Once the paperboard spacer blank has been stamped/cut out, and the creases have been formed, the spacer can be assembled. 
     First, the paperboard spacer blank is folded along central crease  112 . Tab  114  is then adhered to opposing edge  116  using glue, double-sided tape, or another suitable form of adhesion. This forms the collapsed configuration of the spacer. 
     The shape and properties of the spacer according to embodiments of the present invention will now be described. 
       FIG. 5  shows the spacer in the collapsed configuration. When not in use (i.e. when packaged for sale, and being stored/transported by a user), the spacer is preferably kept in the collapsed configuration. Although not clear from  FIG. 5 , in the collapsed configuration the spacer has a substantially flat profile, with the upper and lower portions  100 ,  101 , and first and second axial end portions  102 ,  104 , all being substantially aligned with each other. Moreover, the upper and lower portions overlay one another, so that the spacer has effectively no internal cavity in the collapsed configuration. Accordingly, the total external volume occupied by the spacer is small in the collapsed configuration, and the spacer can be easily stored away. 
     To expand the spacer from the collapsed configuration to the expanded configuration, a user pushes the first and second axial end portions  102 ,  104  towards each other. This forces the first and second axial end portions  102 ,  104  to fold inwards. The first and second axial end portions are forced into a concave profile, which in turn forces the upper and lower portions into a convex profile, so that they form an internal cavity with an internal volume of 500 mL. This internal cavity provides an air flow-path between air inlet  106 , and air outlet  108 . 
       FIGS. 6 a  and 6 b    show respectively a perspective view, and an end-view, of a spacer formed by folding the paperboard spacer blank as above. 
     To collapse the spacer back into the collapsed configuration (i.e. from the expanded configuration), the user pushes the upper and lower portions towards each other. This forces the first and second axial end portions to fold away from each other, out of their concave profile. The volume of the air flow-path is reduced. Once the first and second axial end portions have folded outwards, and the upper and lower portions are in a planar, overlying arrangement, i.e. so that there is effectively no internal cavity, the spacer is back in the collapsed configuration. 
     Further features of the spacer will now be described, with references to  FIGS. 6 a  and 6 b   . The same reference numerals are used for the common features of  FIGS. 3 to 6   b.    
     The spacer is shown in the expanded configuration, ready for use. Upper portion  100  and lower portion  101  are convex (in the expanded configuration shown), the convexity of the upper and lower portions defining a channel, or air flow-path with an internal volume of 500 mL. At a first end of the air flow-path is first axial end portion  102 . At an opposing second end of the air flow path is second axial end portion  104 . The first and second axial end portions are both concave (in the expanded configuration shown), and have a mandorla shape. The concavity of the first and second axial end portions maintains the convexity of the upper and lower portions in the expanded configuration. Inlet aperture  106  is formed in the first axial end portion  102 . Inlet aperture  106  is an air inlet aperture through which air can enter the air flow path. Outlet aperture  108  is formed in the second axial end portion  104 . Outlet aperture  108  is an air outlet aperture through which air can exit the air flow path. In the expanded configuration, the upper and lower portions have a generally perpendicular orientation relative to the first and second axial end portions. 
     As shown, axial end portions  102 ,  104  have the same shape and size. Moreover, axial end portions  102 ,  104  have a mandorla, e.g. bi-convex/lens shape. 
     Inlet aperture  106  has a shape and size selected to match that of the mouthpiece of an inhaler, e.g. pMDI inhaler. Inlet aperture  106  is configured to intimately engage the mouthpiece of an inhaler. There are less shape constraints on the outlet aperture  108 , provided that it is of a size suitable for a user to inhale through it. Outlet aperture  108  may be square, rectangular, circular, or any other suitable shape. 
       FIGS. 7 and 8  show end-views of spacers similar to the embodiment of  FIGS. 6 a  and 6 b   . The spacers in  FIGS. 7 and 8  have the same constituent parts as the spacer of  FIGS. 6 a  and 6 b   . The only difference between the three embodiments is that the shape of the axial end portions  102 ,  104  is different in the embodiments of  FIGS. 7 and 8 . For brevity, only the end-views of the spacers in  FIGS. 7 and 8  are shown. As shown, the axial end portions of the spacer in  FIG. 7  have an octagonal shape. The end-sections of the spacer in  FIG. 8  have a truncated lens shape. 
     The spacers of  FIGS. 6 a    to  8  all have an internal cavity with a volume of 500 mL in the expanded configuration. In particular, the total volume of the air flow-path between the inlet aperture and the outlet aperture is 500 mL. 
     To use the spacer in the expanded configuration, a user secures inlet aperture  106  around the mouthpiece of a medical inhaler device. Through appropriate selection of the size and shape of the inlet aperture  106 , the inhaler mouthpiece fits securely within the inlet aperture  106 , secured by an interference fit. After securing the mouthpiece of the inhaler device in the inlet aperture, the user places his/her mouth over the outlet aperture  108 . The user then activates the medical inhaler, e.g. by depressing a drug reservoir into the medical inhaler device in a manner that is well known in the art, in order to eject a dosage of aerosolized medication into the air flow path through the inlet aperture  106 . A plume of low-velocity aerosolized medication forms in the air flow-path. After a short time (preferably within a few seconds), the user then inhales the plume into his/her lungs through the outlet aperture  108 , preferably in a single deep breath. 
     The air flow path is 10 cm in length from the inlet aperture to the outlet aperture, and so provides a sufficient distance between the inlet aperture and outlet aperture for a low-velocity plume of aerosolized medication to form. 
     Examples 
     Testing of a spacer formed of Invercote G™ 300 g/m 2  paperboard and having the shape as shown in  FIGS. 8 and 9  was carried out by Intertek Laboratories (a certified oral inhaled product test laboratory) using a salbutamol MDI (Ventolin) inhaler. 
     In-vitro testing was conducted using the pharmacopoeia standard method, Next Generation Impactor (NGI). 
     The results are shown in the tables 5 and 6 below. 
     The results show oropharyngeal impaction decreases by 96%, from 48.2 μg (without a spacer) to 1.72 μg (with the paper spacer), and the dose delivered to the lungs increases by 53%, from 38.5% (without a spacer) to 91.3% (with the paper spacer). 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Ventolin (Salbutamol) MDI without spacer. 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 Rep 1 
                 Rep 2 
                 Rep 3 
                 Rep 4 
                 Rep 5 
                 Rep 6 
                 Mean 
                 % RSD 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Actuator 
                 13.86279 
                 15.41427 
                 
                   
                 
                 
                   
                 
                 16.81952 
                 18.31957 
                   
                   
               
               
                 T&amp;M 
                 61.91560 
                 60.50270 
                 
                   
                 
                 41.60536 
                 37.06972 
                 41.06140 
               
               
                     1 
                 
                   
                 
                 1.09677 
                 
                   
                 
                 1.64124 
                 1.84074 
                 1.91750 
               
               
                     2 
                 
                   
                 
                 0.82729 
                 
                   
                 
                 1.09899 
                 
                   
                 
                 1.25334 
               
               
                     3 
                 2.03046 
                 1.188765 
                 2.47290 
                 2.51813 
                 3.07889 
                 2.94964 
               
               
                     4 
                 
                   
                 
                 8.91633 
                 
                   
                 
                 12.66856 
                 15.14915 
                 13.73264 
               
               
                     5 
                 13.55361 
                 
                   
                 
                 13.11028 
                 14.58565 
                 14.14861 
                 
                   
                 
               
               
                     6 
                 3.82522 
                 3.25002 
                 3.38248 
                 3.89581 
                 
                   
                 
                 3.78143 
               
               
                     7 
                 
                   
                 
                 0.70937 
                 
                   
                 
                 0.60781 
                 1.02716 
                 
                   
                 
               
               
                     8 
                 0.51429 
                 0.48550 
                 0.42300 
                 0.36388 
                 
                   
                 
                 0.67119 
               
               
                 Total 
                 107.829 
                 104.519 
                 95.713 
                 95.893 
                 95.198 
                 99.725 
               
               
                 MMAD μm 
                 2.11226 
                 2.15829 
                 2.25585 
                 2.24711 
                 
                   
                 
                 2.27776 
                 2.23521 
                 
                   
                 
               
               
                 GSD 
                 1.72014 
                 1.73519 
                 
                   
                 
                 1.70266 
                 1.67122 
                 1.72325 
                 1.70713 
                 
                   
                 
               
               
                 FPD μg 
                 29.24229 
                 25.81148 
                 
                   
                 
                 33.47485 
                 36.62443 
                 35.80760 
                 31.92443 
                 12.98540 
               
               
                 (≤5.0 μm) 
               
               
                 FPF %* 
                 31.11989 
                 28.96768 
                 
                   
                 
                 42.38104 
                 46.72767 
                 
                   
                 
                 38.50887 
                 18.67504 
               
               
                   
               
               
                     indicates data missing or illegible when filed 
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Ventolin (Salbutamol) MDI with cardboard spacer 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 Rep 1 
                 Rep 2 
                 Rep 3 
                 Rep 4 
                 Rep 5 
                 Rep 6 
                 Mean 
                 % RSD 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Actuator 
                 15.77754 
                 
                   
                 
                 
                   
                 
                 15.38115 
                 15.25622 
                 
                   
                 
                   
                   
               
               
                 Spacer 
                 13.68127 
                 
                   
                 
                 8.37271 
                 8.79331 
                 
                   
                 
                 5.75052 
               
               
                 T&amp;M 
                 
                   
                 
                 
                   
                 
                 1.16707 
                 2.34275 
                 1.51533 
                 2.13277 
               
               
                     1 
                 0.44807 
                 0.56549 
                 0.4032 
                 0.44272 
                 0.52036 
                 0.34744 
               
               
                     2 
                 
                   
                 
                 0.67345 
                 
                   
                 
                 
                   
                 
                 
                   
                 
                 0.49322 
               
               
                     3 
                 
                   
                 
                 
                   
                 
                 2.52936 
                 
                   
                 
                 
                   
                 
                 
                   
                 
               
               
                     4 
                 
                   
                 
                 
                   
                 
                 15.90457 
                 16.01341 
                 
                   
                 
                 13.53822 
               
               
                     5 
                 
                   
                 
                 
                   
                 
                 13.21422 
                 
                   
                 
                 
                   
                 
                 
                   
                 
               
               
                     6 
                 
                   
                 
                 
                   
                 
                 4.04502 
                 3.58644 
                 
                   
                 
                 3.69073 
               
               
                     7 
                 
                   
                 
                 
                   
                 
                 
                   
                 
                 0.61023 
                 0.61441 
                 0.61453 
               
               
                     8 
                 
                   
                 
                 
                   
                 
                 0.453 
                 0.42536 
                 
                   
                 
                 0.42101 
               
               
                 Total 
                 
                   
                 
                 72.147 
                 
                   
                 
                 
                   
                 
                 72.491 
                 57.498 
               
               
                 MMAD μm 
                 
                   
                 
                 2.21576 
                 
                   
                 
                 2.26444 
                 2.30471 
                 
                   
                 
                 2.25413 
                 
                   
                 
               
               
                 GSD 
                 
                   
                 
                 
                   
                 
                 
                   
                 
                 1.52316 
                 1.52123 
                 1.54377 
                 1.52300 
                 
                   
                 
               
               
                 FPD μg 
                 
                   
                 
                 
                   
                 
                 36.78605 
                 
                   
                 
                 
                   
                 
                 35.14805 
                 40.21874 
                 11.35788 
               
               
                 (≤5.0 μm) 
               
               
                 FPF %* 
                 
                   
                 
                 
                   
                 
                 92.15493 
                 
                   
                 
                 
                   
                 
                 
                   
                 
                 91.34830 
                 
                   
                 
               
               
                   
               
               
                     indicates data missing or illegible when filed 
               
            
           
         
       
     
     NGI=Next Generation Impactor; T&amp;M=Throat &amp; Mouth Piece; MMAD=Mass Median Aerodynamic Diameter; GSD=Geometric Standard Deviation; FPD=Fine Particle Dose 
     The FPD (Fine Particle Dose) in Tables 5 and 6 represents the respirable particles. The FTD values in the table 5 without spacer have a mean value of 31.9 μg whilst the FTD values in table 6 with cardboard spacer have a mean value of 40.2 μg. This corresponds to a 26% increase in respirable drug when the cardboard spacer is used. 
     The above embodiments have been described by way of example. Modifications of the above embodiments will be apparent to skilled persons on reading this disclosure and as such are within the scope of the invention.