Nasal delivery device

1. A device for delivering a substance to the nasal airway of a subject, comprising:

a flow resistor; and

a delivery unit for delivering a substance in a gas flow to a nostril of the subject, wherein the delivery unit comprises a nosepiece shaped and sized for insertion into a nostril of the subject, a delivery channel fluidly connected to the nosepiece and configured to receive the substance to be delivered to the nostril, the nosepiece comprising an outlet through which a substance may be delivered into the nasal airway of the subject and a sealing member configured to seal the one nostril of the subject to the outlet, the sealing member including a frusto-conical portion and having a first, distal end and a second, proximal end and being enlarged towards the proximal end to cause an anterior region of the nasal cavity into which the nosepiece is inserted to be enlarged, and a dispensing unit driven by an exhalation air flow of the subject so as to supply a metered dose of substance from the dispensing unit into the delivery channel;

wherein the device is configured to create a positive pressure differential between the oral cavity of the subject and the nasal airway of the subject when the subject exhales against the flow resistor, thereby indirectly achieving closure of the oropharyngeal velum of the subject, and the device is configured to deliver a substance entrained in a gas flow having a flow rate in the nasal airway of at least 20 liters per minute.

2. The device of claim 1 , wherein the flow resistor is operably connected to a tubular section configured to be held between the lips of the subject.

3. The device of claim 1 , wherein the flow resistor is operably connected to a mouthpiece.

4. The device of claim 1 , further comprising:

a pressure-triggered valve fluidly connected to the flow resistor, wherein the valve is configured to open when a predetermined positive pressure is developed upon exhalation by the subject.

5. The device of claim 1 , wherein the nosepiece is formed of a resilient material.

6. The device of claim 1 , wherein the nosepiece is configured to extend into a nasal cavity of the subject so as to expand the valve region of the nasal cavity of the subject.

7. The device of claim 1 , further comprising:

a positive pressure indicator or a flow rate indicator.

8. The device of claim 1 , wherein the device is configured such that the gas flow entraining a substance is delivered at a driving pressure sufficient to cause the gas to flow around the posterior margin of the nasal septum of the subject and out of the other nostril of the subject.

9. The device of claim 1 , wherein a portion of the nosepiece is shaped like a nasal olive, or comprises a nasal olive-like member, which is shaped and sized to create the fluid tight seal.

10. The device of claim 1 , wherein the flow resistor is configured to deliver a substance entrained in a gas flow having a flow rate in the nasal airway of at least 20 liters per minute.

11. The device of claim 1 , further comprising at least one of a delivery unit, control unit, pressure sensitive valve, mouthpiece, oral exhalation unit, flow resistor and valve, and movable element configured to deliver a substance entrained in a gas flow having a flow rate in the nasal airway of at least 20 liters per minute.