The purpose of this study is to establish whether addition of extra-fine particle steroid inhalers achieve additional suppression of small airways inflammation when added to 'standard' Fluticasone/Salmeterol combination therapy in refractory asthma.

Inclusion Criteria:

• Refractory, non-smoking asthmatics with FEV1 les than 80% predicted
• RV greater than 100% predicted and CANO greater than 3ppb when stepped up to 1000µg of fluticasone per day, with or without additional asthma medication.
• Informed consent and ability to perform exhaled nitric oxide assessment.
• Participants must be on greater than 500mcg of fluticasone per day to enter dose ramp run-in.

Exclusion Criteria:

• Recent respiratory infection or oral steroid use.
• Pregnancy or lactation.
• Known or suspected contra-indication to any of the IMP's.
• CANO less than 3ppb, FEV1 greater than 80% or RV less than 100% at post-optimisation visit.