1. School of Rehabilitation Sciences, University of Ulster at Jordanstown, Northern Ireland BT37 OQB, UK
2. School of Rehabilitation Sciences, University of Ulster at Jordanstown, Northern Ireland BT37 OQB, UK; Regional Adult CF Centre, Belfast City Hospital, Belfast, Northern Ireland BT9 7AB, UK
3. Regional Adult CF Centre, Belfast City Hospital, Belfast, Northern Ireland BT9 7AB, UK; Department of Respiratory Medicine, Queen's University Belfast, University Street, Belfast, Northern Ireland BT7 1 SU, UK