fig2 illustrates a delivery device in accordance with a first embodiment of the present invention . the delivery device comprises an oral exhalation unit 20 and a substance delivery unit 22 . in this embodiment the oral exhalation unit 20 and the delivery unit 22 are provided as separate components , but alternatively could be detachably coupled , for example by means of velcro ™ fasteners , connected , for example by means of screws and / or rivets , or even integrally formed . the oral exhalation unit 20 comprises a tubular section 24 and a mouthpiece 26 attached to one end of the tubular section 24 . the mouthpiece 26 , which in use is gripped in the lips of a user , is formed separately of the tubular section 24 to allow for replacement , but could alternatively be integrally formed . in this embodiment the mouthpiece 26 is a snap fit on the tubular section 24 , but could equally be a screw fit . the tubular section 24 includes a flow resistor 28 , in this embodiment a fixed baffle plate , configured to provide a sufficient resistance to exhalation therethrough by a subject as to cause the generation of a positive pressure in the oral cavity of the subject and the closure of the velum on exhalation by the subject . in alternative embodiments the flow resistor 28 could be a movable member , such as a biased flap , a resilient membrane or a damped wheel . the delivery unit 22 comprises a nosepiece 30 , in this embodiment formed of a resilient material such as a polymeric material , for providing a tight sealing fit in one of the nostrils of the subject , a medicament supply unit 32 for supplying a gas flow entraining medicament at a predetermined pressure sufficient to open a flow path beyond the posterior margin of the nasal septum when delivered into one of the nasal cavities of the subject , and a tubular section 34 coupling the nosepiece 30 and the medicament supply unit 32 . in a preferred embodiment the nosepiece 30 can include an external olive or be shaped to cause the anterior region of the nasal cavity into which the nosepiece 30 is inserted to be enlarged . in a particularly preferred embodiment the nosepiece 30 can be shaped , for example by including swirl - inducing projections , to provide the exiting gas flow with an optimal flow pattern and particle size distribution . the nosepiece 30 is formed separately of the tubular section 34 to allow for replacement , but could alternatively be integrally formed . in this embodiment the nosepiece 30 is a snap fit on the tubular section 34 , but could equally be a screw fit . the medicament supply unit 32 can comprise an aerosol spray generator for generating an aerosol spray of liquid droplets containing medicament , such as provided by a pressurized metered dose inhaler , or a pressurized gas source for entraining a metered dose of a dry powder containing medicament loaded thereinto , which powder could alternatively be loaded into a compartment in the tubular section 34 . in use , a subject grips the mouthpiece 26 in his or her lips and fits the nosepiece 30 into one of his or her nostrils . the subject then exhales through the mouthpiece 26 , the flow of which exhaled air is resisted by the flow resistor 28 in the tubular section 24 such as to develop a positive pressure in the oral cavity of the subject , with the positive pressure being such as to develop a pressure differential across the velum sufficient to cause closure of the velum of the subject . the applicant has established that a positive pressure differential between the oral cavity and the nasal airway of about 5 cmh2o is required to maintain the velum in the closed position . the applicant has further established that a subject should be able to maintain a flow rate of about 3 to 30 liters per minute for about 1 to 20 seconds , with flow rates of about 10 to 20 liters per minute and delivery times of about 2 to 5 seconds being considered as optimal . after closure of the velum , the medicament supply unit 32 is then actuated to deliver a gas flow entraining medicament through the nosepiece 30 and into the nasal airway of the subject . as mentioned above , this gas flow is at such a pressure as to open a communication path beyond the posterior margin of the nasal septum such that the gas flow flows through the one nasal cavity , around the posterior margin of the nasal septum , in effect being redirected through an angle of 180 degrees , and out of the other nasal cavity . again , as already described , this bidirectional flow provides for a much enhanced deposition of the medicament in the posterior region of the nasal airway . in one modification , the medicament supply unit 32 can be omitted from the delivery unit 22 , and instead a metered dose of dry powder loaded into a compartment in the tubular section 34 , with the delivery air flow being provided by another person , such as the parent of a paediatric subject , blowing into the distal end of the tubular section 34 . fig3 illustrates a delivery device in accordance with a second embodiment of the present invention . the delivery device comprises the oral exhalation unit 20 and the delivery unit 22 of the above - described first embodiment , and an outlet unit 36 for fitting to the other nostril of a subject to which the delivery unit 22 is fitted . the outlet unit 36 comprises a tubular section 38 and a nosepiece 40 , in this embodiment formed of a resilient material such as a polymeric material , attached to one end of the tubular section 38 for providing a tight sealing fit in the other nostril of the subject . the nosepiece 40 is formed separately of the tubular section 38 to allow for replacement , but could alternatively be integrally formed . in this embodiment the nosepiece 40 is a snap fit on the tubular section 38 , but could equally be a screw fit . as with the nosepiece 30 of the delivery unit 22 , in a preferred embodiment the nosepiece 40 can include an external olive or be shaped to cause the anterior region of the other nasal cavity into which the nosepiece 40 is inserted to be enlarged . the tubular section 38 includes a flow resistor 41 , in this embodiment a baffle plate , configured to provide a sufficient flow resistance to an exhalation flow therethrough as to cause the generation of a dynamic positive pressure in the nasal airway . in a preferred embodiment the flow resistor 41 is adjustable to allow for adjustment of the level of the resistance and hence provide control of the dynamic pressure in the nasal airway . in alternative embodiments the flow resistor 41 could be a movable member , such as a biased flap , a resilient membrane or a damped wheel . in a preferred embodiment the outlet unit 36 includes an indicator for providing at least one of a visual or audible signal on achieving a predetermined positive pressure upstream thereof , that is , in the nasal airway . preferably , the indicator comprises a whistle . in this way , the subject is provided with positive feedback of proper use of the device . use of the delivery device of this embodiment is the same as for the above - described first embodiment . however , as mentioned above , by the provision of the flow resistor 41 in the outlet unit 36 downstream of the outlet nostril of the subject , a positive dynamic pressure is maintained in the nasal airway . this positive pressure advantageously acts to dilate the various ostia in the nasal airway , such as the sinus ostia and the tubal ostia , and the associated tubes , namely the sinus tubes and the auditory tubes , so as to promote the delivery of medicament thereto . further , this positive pressure acts to improve deposition on the adenoid which can often obstruct the tubal ostia , the middle meatus which is a common location of nasal polyps , and the cleft to the olfactory cells . fig4 illustrates a delivery device in accordance with a third embodiment of the present invention . the delivery device is very similar to that of the delivery device of the above - described second embodiment , and thus , in order to avoid unnecessary duplication of description , only the differences will be described in detail , with like parts being designated by like reference signs . this delivery device differs only in further comprising a pressure sensor 43 , in this embodiment a pressure - sensitive spring or membrane , located in the tubular section 34 of the delivery unit 22 downstream of the medicament supply unit 32 , and a control unit 44 coupled to the sensor 43 and the medicament supply unit 32 . the control unit 44 is configured to control the flow rate of the delivery gas supplied by the medicament supply unit 32 in order to optimize the particle deposition efficiency in the nasal airway regardless of the degree of nasal congestion . as mentioned hereinabove , by maintaining an optimum flow rate in the nasal airway , the deposition efficiency of the medicament - containing particles is increased , referred to as the particle deposition efficiency . if , ordinarily , a flow rate of about 15 liters per minute is required to maximize the particle deposition efficiency , then in a congested nasal airway a lower flow rate , possibly 10 liters per minute , would be required and in an open nasal airway a higher flow rate , possibly 20 liters per minute , would be required . operation of this delivery device is otherwise the same as that of the above - described second embodiment . fig5 illustrates a modified oral exhalation unit 20 for the delivery devices of the above - described embodiments . this modified oral exhalation unit 20 differs in that the tubular section 24 includes a lateral opening 45 upstream of the flow resistor 28 and in further comprising , as an indicator , an inflatable fig4 connected to the lateral opening 45 , which fig4 when inflated assumes a prominent position in the field of vision of the subject . in fig4 , the fig4 is shown inflated . by providing such a display feature , subject compliance , particularly in paediatric subjects , should be improved . the oral exhalation unit 20 further comprises an inflation line 48 connected to the fig4 which allows the fig4 to be further inflated by another person , typically the parent of a paediatric subject , or a pump . in an alternative embodiment , instead of being inflatable , the fig4 could be of any kind which is brought into a prominent position on exhalation by the subject , typically a mechanically or electrically - operated figure . in a preferred embodiment the fig4 can be configured so as to be inflated on the subject achieving an optimum exhalation flow rate . in this way , the fig4 acts as an indicator . use of the delivery device of this embodiment is the same as that of the abovedescribed first embodiment . however , on exhaling through the mouthpiece 26 , the developed pressure causes the fig4 to be inflated and assume a prominent position in the field of vision of the subject . this appearance of the fig4 is particularly appealing for paediatric subjects as the fun element of inflating the fig4 can alleviate any unnecessary anxiety . fig6 illustrates a delivery device in accordance with a fourth embodiment of the present invention . the delivery device comprises a chamber 50 which includes an inlet 52 and an outlet 54 , a mouthpiece 56 connected to the inlet 52 and a nosepiece 58 connected to the outlet 54 . the nosepiece 58 is configured to provide a tight sealing fit in one of the nostrils of a subject . the chamber 50 includes a flow resistor 60 , in this embodiment a plurality of baffle plates , and a medicament - receiving compartment 62 downstream of the flow resistor 60 for containing a metered dose of a dry powder containing medicament to be delivered to the nasal airway of a subject . in this embodiment the nosepiece 58 is formed of a resilient material such as a polymeric material . in a preferred embodiment the chamber 50 may include a desiccant . in a preferred embodiment the flow resistor 60 can be provided by a moisture - absorbing filter . in use , a subject grips the mouthpiece 56 in his or her lips and fits the nosepiece 58 into one of his or her nostrils . the subject then exhales through the mouthpiece 56 , the flow of which exhaled air is resisted by the flow resistor 60 in the chamber 50 and the resistance of the nasal airway such as to develop a positive pressure in the oral cavity of the subject sufficient to cause closure of the velum . the exhaled air , after passing the flow resistor 60 , then entrains the powdered medicament in the medicament receiving compartment 62 , and this air flow entraining medicament then passes through the nosepiece 58 into the nasal airway of the subject . the exhaled air entering the nasal airway is at a pressure sufficient to open a communication path beyond the posterior margin of the nasal septum such that the air flow flows through the one nasal cavity , around the posterior margin of the nasal septum , in effect being redirected through an angle of 180 degrees , and out of the other nasal cavity . again , as already described , this bidirectional flow provides for a much enhanced deposition of the medicament in the posterior margin of the nasal airway . in a preferred embodiment the delivery device includes a pressure - triggered valve , preferably located in the mouthpiece 56 , which is configured to open only when a predetermined positive pressure has been developed by the exhalation of the subject , typically at a positive pressure of about 10 cm h 2 o . this configuration advantageously avoids the possibility of medicament being delivered to the nasal airway with the velum in the open position and thereby reduces the risk of undesirably depositing medicament outside the nasal airway . in another preferred embodiment , similarly to third - described embodiment , the delivery device can include an outlet unit for providing a flow resistor downstream of the other nostril of the subject such as to maintain a positive dynamic pressure in the nasal airway . fig7 illustrates a delivery device in accordance with a fifth embodiment of the present invention . the delivery device comprises an oral exhalation unit 70 through which a subject exhales to close his or her velum and a medicament delivery unit 72 for supplying an air flow entraining medicament to the nasal airway of the subject . the oral exhalation unit 70 comprises a tubular section 74 and a mouthpiece 76 attached to one end of the tubular section 74 . the mouthpiece 76 , which is gripped in the lips of the subject , is formed separately of the tubular section 74 to allow for replacement , but could alternatively be integrally formed therewith . in this embodiment the mouthpiece 76 is a snap fit on the tubular section 74 , but could equally be a screw fit . the tubular section 74 includes a flow resistor 78 , in this embodiment a gearwheel , configured to rotate on 1 s exhalation by the subject and yet provide sufficient resistance to the exhalation flow as to cause the generation of a positive pressure in the oral cavity of the subject sufficient to maintain the required positive pressure differential between the oral cavity and the nasal airway and thereby maintain the velum in the closed position . the delivery unit 72 comprises a tubular section 80 and a nosepiece 82 , in this embodiment formed of a resilient material such as a polymeric material , for providing a tight sealing fit in one of the nostrils of the subject , attached to one end of the tubular section 80 . the nosepiece 82 is formed separately of the tubular section 80 to allow for replacement , but could alternatively be integrally formed therewith . in this embodiment the nosepiece 82 is a snap fit on the tubular section 80 , but could equally be a screw fit . in a preferred embodiment the nosepiece 82 can include an external olive or be shaped to cause the anterior region of the nasal cavity , into which the nosepiece 82 is inserted , to be enlarged . in a particularly preferred embodiment the nosepiece 82 can be shaped , for example by including swirl - inducing projections , to provide the exiting air flow with an optimal flow pattern and particle size distribution . the tubular section 80 includes an impeller 84 coupled to the gearwheel 78 in the tubular section 74 of the oral exhalation unit 70 , such as to be rotated on rotation of the gearwheel 78 to draw air into the tubular section 80 and provide an air flow therethrough at a pressure sufficient to open the flow path beyond the posterior margin of the nasal septum when delivered into one of the nasal cavities of the subject . the delivery unit 72 further comprises a dispensing unit 86 for dispensing a metered dose of a dry powder containing medicament to the tubular section 80 upstream of the impeller 84 . in this embodiment the dispensing unit 86 is manually actuated to supply a metered dose of dry powder containing medicament into the tubular section 80 , but could alternatively be configured to the driven by the gearwheel 78 so as to avoid the need for any manual intervention on the part of the subject . in use , a subject grips the mouthpiece 76 in his or her lips and fits the nosepiece 82 into one of his or her nostrils . the subject then exhales through the mouthpiece 76 , the flow of which exhaled air is resisted by the gearwheel 78 such as to develop a positive pressure in the oral cavity of the subject sufficient to cause the velum of the subject to close . the exhaled air causes rotation of the gearwheel 78 which in turn causes rotation of the impeller 84 , and the rotation of the impeller 84 develops an air flow through the tubular section 80 which entrains the metered dose of dry powder containing medicament and delivers the same through the nosepiece 82 to the nasal airway of the subject . as mentioned above , this air flow is at a pressure sufficient to open a communication path beyond the posterior margin of the nasal septum such that the air flow flows through the one nasal cavity , around the posterior margin of the nasal septum , in effect being redirected through an angle of 180 degrees , and out of the other nasal cavity . again , as already described , this bidirectional flow provides for a much enhanced deposition of the medicament in the posterior region of the nasal cavity . in a preferred embodiment the gearwheel 78 is configured such that rotation thereof is prevented until a predetermined flow rate has been developed which is sufficient to ensure that the entraining gas flow developed by the impeller 84 is optimal . this configuration advantageously ensures an optimal particle deposition efficiency and avoids the possibility of medicament being delivered to the nasal airway with the velum in the open position so as to reduce the risk of undesirably depositing medicament outside the nasal airway . fig8 illustrates a delivery device in accordance with a sixth embodiment of the present invention . the delivery device comprises a housing 90 for housing a blister pack element 92 which includes a plurality of blisters 94 therein , each containing powder containing medicament , and a tubular section 96 in communication with one of the blisters 94 when open , one end of which tubular section 96 provides a mouthpiece 98 which in use is gripped in the lips of a subject . the tubular section 96 includes an element 100 movably disposed therein between a first , normally closed position and a second , open position . in this embodiment the element 100 comprises a propeller or the like rotatably mounted on a threaded shaft and normally biased to the closed position by a compression spring . the element 100 is configured both to function as a flow resistor and a valve . in this embodiment the element 100 is configured to move to the medicament - releasing open position by rotation along the threaded shaft against the bias of the compression spring , with the powder being entrainable by an air flow only when the exhalation flow exceeds a predetermined flow rate . the flow rate , preferably in the range of about 5 to 20 liters per minute , at which the powder containing medicament is entrained by the air flow is a function , in inverse relation , to the driving pressure which is itself a function of the nasal resistance as described hereinabove . as will be understood , this configuration advantageously provides for an optimal particle deposition efficiency in releasing the powder containing medicament at the optimal flow rate , and avoids the possibility of medicament being delivered to the nasal airway with the velum in the open position . the delivery device further comprises a nosepiece 102 , in this embodiment formed of a resilient material such as a polymeric material , for providing a tight sealing fit in one of the nostrils of the subject attached to the other end of the tubular section 96 downstream of the element 100 . the nosepiece 102 is formed separately of the tubular section 96 to allow for replacement , but could alternatively be integrally formed therewith . in this embodiment the nosepiece 102 is a snap fit on the tubular section 96 , but could equally be a screw fit . in a preferred embodiment the nosepiece 102 can include an external olive or be shaped to cause the anterior region of the nasal cavity into which the nosepiece 102 is inserted to be enlarged . in a particularly preferred embodiment the nosepiece 102 can be shaped , for example by including swirl - inducing projections , to provide the exiting air flow with an optimal flow pattern and particle size distribution . the delivery device further comprises a blister opening mechanism 104 for opening the blister 94 in communication with the tubular section 96 . in this embodiment the blister opening mechanism 104 is manually operated by the subject prior to delivery . in use , a subject grips the mouthpiece 98 in his or her lips and fits the nosepiece 102 into one of his or her nostrils . the subject then exhales through the mouthpiece 98 , the flow of which exhaled air is resisted by the element 100 until a predetermined flow rate has been achieved . once this predetermined flow rate has been achieved , at which flow rate the velum is in the closed position , the element 100 is in the open position and the exhaled airflow entrains the powdered medicament in the blister 94 and delivers the same through the nosepiece 102 to the nasal airway . the driving pressure of this air flow is at a level sufficient to maintain a communication path beyond the posterior margin of the nasal septum such that the air flow flows through the one nasal cavity , around the posterior margin of the nasal septum , in effect being redirected through an angle of 180 degrees , and out of the other nasal cavity . again , as already described , this bidirectional flow provides for a much enhanced deposition of the medicament in the posterior margin of the nasal cavity . in a preferred embodiment the delivery device includes a blister pack advancement mechanism , operated by movement of the mouthpiece 98 , for rotating the blister pack element 92 such that another unused blister 94 is located at the delivery position . in a particularly preferred embodiment the blister pack advancement mechanism can be coupled to the blister opening mechanism 104 such as automatically to open the blister 94 , and thereby avoid the need for any further intervention by the subject . in one modification , similarly to the above - described modification of the first embodiment as illustrated in fig3 , the delivery device can include an outlet unit for providing a flow resistor downstream of the other nostril of the subject such as to maintain a positive dynamic pressure in the nasal airway . in another modification , the blister pack element 92 can be omitted and the housing 90 instead provided with a chamber which is in communication with the tubular section 96 and into which a metered dose of dry powder containing medicament can be loaded . with this configuration , the powder in the chamber is entrained on the element 100 being driven to the second position and the blister pack advancement mechanism is configured to meter a dose of powder containing medicament into the chamber on operation thereof . as will be understood , in essence , the present invention can be broadly based on any dry powder inhaler , such as the turbuhaler ™ as manufactured by astrazeneca plc , the accuhaler ™ as manufactured by glaxo plc or the twisthaler ™ as manufactured by schering ag , where the usual mouthpiece is replaced by a nosepiece and a mouthpiece is provided in communication with the air inlet of the inhaler such as to utilize the air exhaled by a subject as the entraining delivery air . fig9 illustrates a delivery device in accordance with a seventh embodiment of the present invention . the delivery device comprises a housing 110 and a tubular section 112 extending through the housing 110 , one end of which provides a mouthpiece 114 which in use is gripped in the lips of a subject . the tubular section 112 includes an element 116 movably disposed therein between a first , normally closed position and a second , trigger position . in this embodiment the element 116 comprises a propeller or the like rotatably mounted on a threaded shaft and normally biased to the closed position by a compression spring . the element 116 is configured to function as a flow resistor , a valve and a trigger for the delivery of an aerosol spray into the tubular section 112 as will be described in detail hereinbelow . in this embodiment the element 116 is configured to move to the medicament - releasing open position , by rotation along the threaded shaft against the bias of the compression spring , only when the exhalation flow exceeds a predetermined flow rate . the flow rate at which the medicament is released , preferably in the range of about 5 to 20 liters per minute , is a function , in inverse relation , to the driving pressure which is itself a function of the nasal resistance as described hereinabove . as will be understood , this configuration advantageously provides for an optimal particle deposition efficiency in releasing the medicament at the optimal flow rate , and avoids the possibility of medicament being delivered to the nasal airway with the velum in the open position . the tubular section 112 further includes a nozzle block 117 for providing an aerosol spray through the tubular section 112 along the longitudinal axis thereof . as will be described in detail hereinbelow , the nozzle block 117 receives the valve stem 122 of an aerosol canister 120 . the delivery device further comprises a known aerosol canister 120 used to deliver metered volumes of a propellant , preferably a hydrofluoroalkane ( hfa ) propellant or the like , containing medicament , either as a suspension or as a solution . the aerosol canister 120 comprises a main body 121 which contains a volume of propellant under pressure containing medicament , a valve stem 122 through which the propellant containing medicament is in use delivered on relative movement of the main body 121 and the valve stem 122 , and a metering valve 124 for metering a predetermined volume of propellant containing medicament to the valve stem 122 on movement thereof . the delivery device further comprises a trigger mechanism 126 for relatively moving the main body 121 and the valve stem 122 of the aerosol canister 120 to effect the delivery of a metered volume of propellant containing medicament through the nozzle block 117 . in this embodiment the trigger mechanism 126 comprises a resilient element 128 for loading the main body 121 with an actuation force , and a lever assembly 130 coupled to the movable element 116 to cause the release of the actuation force provided by the resilient element 128 on movement of the movable element 116 from the closed position to the trigger position . the delivery device further comprises a nosepiece 132 , in this embodiment formed of a resilient material such as a polymeric material , for providing a tight sealing fit in one of the nostrils of the subject , attached to the other end of the tubular section 112 downstream of the movable element 116 . the nosepiece 132 is formed separately of the tubular section 112 to allow for replacement , but could alternatively be integrally formed therewith . in this embodiment the nosepiece 132 is a snap fit on the tubular section 112 , but could equally be a screw fit . in a preferred embodiment the nosepiece 132 can include an external olive or be shaped to cause the anterior region of the nasal cavity into which the nosepiece 132 is inserted to be enlarged . in a particularly preferred embodiment the nosepiece 132 can be shaped , for example by including swirl - inducing projections , to provide the exiting air flow with an optimal flow pattern and particle size distribution . in use , a subject primes the trigger mechanism 126 , grips the mouthpiece 114 in his or her lips and fits the nosepiece 132 into one of his or her nostrils . the subject then exhales through the mouthpiece 114 , the flow of which exhaled air is resisted by the movable element 116 until a predetermined flow rate has been achieved . once this predetermined flow rate has been achieved , at which flow rate the velum is in the closed position , the movable element 116 is in the open position , triggering the movement of the lever assembly 130 and hence the relative movement of the main body 121 and the valve stem 122 of the canister 120 to deliver a metered volume of propellant containing medicament to the nozzle block 117 to generate an aerosol spray of liquid droplets containing medicament through the nosepiece 132 to the nasal airway . this aerosol flow is at a pressure sufficient to maintain a communication path beyond the posterior margin of the nasal septum such that the flow flows through the one nasal cavity , around the posterior margin of the nasal septum , in effect being redirected through an angle of 180 degrees , and out of the other nasal cavity . again , as already described , this bidirectional flow provides for a much enhanced deposition of the medicament in the posterior margin of the nasal cavity . as will be understood , in essence , the present invention can be broadly based on any breath - actuated pressurized metered dose inhaler , where the usual mouthpiece is replaced by a nosepiece and a mouthpiece is provided in communication with the air inlet of the inhaler such as both to trigger the triggering mechanism and utilize the air exhaled by a subject as the entraining delivery air . finally , it will be understood that the present invention has been described in its preferred embodiments and can be modified in many different ways without departing from the scope of the invention as defined by the appended claims .
a delivery device for and a method of delivering a substance to the nasal airway of a subject , in particular the posterior region of the nasal airway , the delivery device comprising : a closure unit for causing the closure of the oropharyngeal velum of the subject ; and a delivery unit for delivering a gas flow entraining a substance to one of the nostrils of the subject at such a driving pressure as to flow around the posterior margin of the nasal septum and out of the other nostril of the subject , wherein the delivery unit comprises a nosepiece which includes an outlet through which the gas flow is in use delivered to the one nostril and a sealing member for sealing the one nostril to the outlet such as in use to prevent the escape of the gas flow through the one nostril .