This study will investigate the role of a portable Continues Positive Airway Pressure device (pCPAP) in management of patients with symptomatic Excessive Central Airway Collapse (ECAC). ECAC is characterised by complete or partial collapse of central airways on exhalation. In some cases, this can cause persistent breathlessness and severely limited exercise capacity. Current treatment options for ECAC are very limited. Standard assistive breathing devices such as CPAP machines are sometimes used to relieve symptoms at night or at rest. This does not address breathlessness during activity which drives accumulation of disability over time.

The main aims of this project are to assess the effect of a portable CPAP (pCPAP) device on exercise capacity and symptoms and evaluate the feasibility of wearing pCPAP at home during routine activities. Lightweight battery-powered portable CPAP devices have been recently developed to facilitate travel to remote areas by people with Obstructive Sleep Apnoea (OSA). Patients with ECAC can wear them during physical activity to prevent airway collapse but their potential benefits have not been evaluated in clinical trials.

For this study, the investigators will recruit 20 patients with ECAC who will attend for two study visits 4-6 weeks apart in a single centre (The Royal Papworth Hospital). The primary outcome measure will be a shuttle walk test performed repeatedly with and without pCPAP in a randomised order. Secondary outcomes will include assessment of activity level, breathlessness, quality of life ,pCPAP usage and its acceptability. The study will evaluate a pragmatic way of CPAP titration and application. Previously acquired diagnostic baseline computed tomography (CT) scans will be analysed with a novel Functional Respiratory Imaging (FRI) tool. This software tool will enable retrospective reflections on the changes occurring within the lungs for patients with ECAC. This may help identify predictive features of potential pCPAP responders and inform future use.

Inclusion Criteria:

1. Diagnosis of ECAC based on >50% reduction of the antero-posterior diameter of large airways demonstrated on dynamic CT thorax or bronchoscopy. Only patients with tracheal and/or bilateral large bronchi (main to lobar) involvement will be included.
2. Symptoms of dyspnoea felt to be predominantly caused by ECAC (where ECAC is the only respiratory pathology or dyspnoea is clearly out of proportion to a co-morbid respiratory condition)
3. Medical Research Council (MRC) breathlessness scale of 3 (I stop for breath after walking about 100 yards or after a few minutes on level ground) or more.
4. Age over 18 years
5. Able to give informed consent -

Exclusion Criteria:

• Patients with dynamic collapse of only segmental airways
• Comorbidity which is likely to be an additional limiting factor in exercise tolerance
• Contraindication to CPAP
• Contraindication to incremental shuttle walk testing (ISWT), including; myocardial infarction within the last 3-5 days, unstable angina, uncontrolled arrhythmia, severe symptomatic cardiac or valvular disease, acute pulmonary embolus, uncontrolled asthma, syncope, mental impairment resulting in inability to perform test.
• Resting oxygen saturations <90% on air or need for ambulatory oxygen therapy
• Immobility that would make ISWT unfeasible
• Severe emphysema
• Acute infectious disease
• Acute respiratory illness