Cystic Fibrosis (CF) is a life limiting illness. Median predicted UK survival is 41.4 years (UK CF Registry 2011). The commonest cause of death is respiratory failure.

Non invasive ventilation (NIV) is a system which delivers a preset pressure to supplement the size and depth of each breath. It is introduced in CF to manage established respiratory failure. A nose or a mask which covers both the nose and mouth allows flexible ventilation, is used just at night, or for part of the day in addition or for 24 hours as clinical status indicates. It is introduced within a normal ward environment and then continued longterm at home.Once respiratory failure is established longterm noninvasive ventilation is introduced throughout 24 hours and multidisciplinary assessment concludes that the timing is appropriate for the individual.

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.

Aim: To compare the clinical efficacy with the patient experience of NIV on recovery from an acute respiratory exacerbation complicated by respiratory failure in adult Cystic Fibrosis.

Design: The study will use a mixed methodology and it will be in 2 phases. Phase I A group randomised controlled trial

The following measurements will be performed on days 1, 3, 7, 10, 14 and twice weekly until discharge:

The exact timing of measurements will be planned by the participant and the researcher.

All of the outcome measures form part of routine clinical practice except the symptom score; the Cystic Fibrosis Respiratory Symptoms Diary (CFRSD V2.0) (Goss et al., 2009)

1. Early morning and day time carbon dioxide (CO2) level.
2. Day time oxygen levels
3. Lung function Forced Expiratory Volume in 1 second (FEV1) and Forced Vital Capacity (FVC)
4. Day time resting Respiratory Rate (RR), Heart Rate (HR)
5. Symptom score CFRSD

Phase II A qualitative exploration of the experience of using NIV for adults with Cystic Fibrosis during an acute exacerbation

Methods: Prior to discharge a semistructured interview designed to explore the experience of using noninvasive ventilation will be undertaken by a clinical psychologist from the Cystic Fibrosis multidisciplinary team. The interviews will be undertaken purely for the research project, recorded and transcribed verbatim by the lead investigator. Thematic analysis will be undertaken to interpret and explore the individual's experience. Credibility checking of interpretation will be undertaken by the clinical psychologists and within academic supervision sessions.

Inclusion Criteria:

• Adult Cystic Fibrosis
• Hospital admission to Pearce Ward Manchester Adult Cystic Fibrosis Centre
• Acute respiratory exacerbation conforming with a standard definition of pulmonary exacerbation (Fuchs et al 1994).
• An admission day time CO2 > 6 kilopascal (kPa) on standard therapy
• Freely given informed consent.-
• 24.3.15 substantial amendment approval for an admission early morning CO2 > 6 kPa

Exclusion Criteria:

• A day time CO2 >8.0 kPa
• respiratory acidosis
• clinical exclusion by CF consultant physician or clinical psychologist