 During the interviews a semi-structured topic guide will address practical barriers to optimal oxygen usage, practical, social and psychological difficulties encountered, concerned about dependency, and views on the information required prior to ambulatory oxygen prescription. The interviews will also explore patients and carers experience of participating in the trial. Notes will be written after each interview to aid reflective analytical processes. Individual feed back on how the system and the service could be improved will assess how the needs of patients and their future involvement can be incorporated into the design of more patients and their future involvement can be incorporated into the design of more patients centred devices. 