We wish to measure the inspiratory flow and volumes generated by the subjects inhaling from a spirometer with a high resistance dry powder inhaler in series in subjects with cystic fibrosis.

Inclusion Criteria:

• CF
• FEV1 ≥ 30% and < 90% predicted

Exclusion Criteria:

• Be considered "terminally ill" or listed for lung transplantation
• Have had a lung transplant
• Have had a significant episode of haemoptysis (>60 ml) in the three months prior to enrolment
• Have had a myocardial infarction in the three months prior to enrolment
• Have had a cerebral vascular accident in the three months prior to enrolment
• Have had major ocular surgery in the three months prior to enrolment
• Have had major abdominal, chest or brain surgery in the three months prior to enrolment
• Have a known cerebral, aortic or abdominal aneurysm
• Be breast feeding or pregnant
• Be using beta blockers
• Have unstable asthma

CF 6yrs and above