A Randomised Feasibility Study of CPAP in Large Airway Collapse

Large airway collapse (LAC) is an increasingly recognised condition characterised by either bowing of the posterior membrane/trachealis muscle into the trachea or main bronchi (also known as excessive dynamic airway collapse, EDAC) or weakening of the tracheal cartilage (also known as tracheobronchomalacia, TBM).(1-3) LAC often co-exists with other chronic airway conditions, such as asthma or chronic obstructive pulmonary disease (COPD) and is frequently misdiagnosed or overlooked as symptoms, such as shortness of breath, cough and wheeze overlap with other respiratory disease.(1) There is no standardised treatment pathway for patients diagnosed with LAC and current treatment options are limited to physiotherapy and/or hypertonic saline.(3) Exacerbations of LAC, defined as an acute worsening of respiratory symptoms, typically reduce health-related quality of life and increase healthcare utilisation.(4) Small studies and case series have suggested continuous positive airway pressure (CPAP) as a potential treatment for LAC to reduce exacerbations and improve quality of life.(5,6) It is hypothesised CPAP may work as a pneumatic splint helping to prevent dynamic collapse of the large airways. This may increase lung volumes due to increase in flow at functional residual capacity (FRC) and support higher elastic recoil and increased expiratory flow. Additionally, splinting of the large airways may cause stiffening of the large airways, resulting in less resistance and turbulence during expiration and may support sputum expectoration.(3) There is a need for high quality randomised controlled trial (RCT) evidence to inform clinical recommendations in the United Kingdom (UK), as well as globally. Prior to this there is a need for further work exploring the feasibility of performing a large RCT and understanding the acceptability of CPAP as a future treatment for LAC. Aim To conduct a randomised feasibility study that will provide data to confirm if a larger randomised trial of CPAP in patients diagnosed with LAC is viable