This study aims to evaluate a potential development of current practice: the use of non invasive ventilation during hospital admission only to enhance recovery from an acute exacerbation which has caused respiratory failure in those individuals where long term non invasive ventilation is not yet indicated. A mixed methods design will allow description of the experience of noninvasive ventilation during a semistructured interview to add to understanding of the results from an experiment designed to measure the differences between noninvasive ventilation and standard care.