Characterisation of Large Airway Collapse During Exercise (LACE)

Plain-language summary

The large central airways (i.e. trachea and bronchi) act as a conduit to enable lower airway ventilation but also facilitate airway clearance during dynamic manoeuvres, such as coughing. It is becoming increasingly well recognised however, that in a significant proportion of individuals with chronic airway disease (e.g. chronic obstructive pulmonary disease-COPD or chronic asthma) and in those with an elevated body mass index (BMI), that the large airways may exhibit a tendency to excessive closure or narrowing. This large airway collapse (LAC) can be associated with exertional breathlessness and difficulty clearing airway secretions. A variety of terms have been used to describe LAC including excessive dynamic airway collapse (EDAC) or if the cartilaginous structures are involved then tracheobronchomalacia (TBM). One clear limitation of the current approach to diagnosis is the fact that many of the 'diagnostic' tests employed, utilise static, supine measures +/- forced manoeuvres. These are somewhat physiologically flawed and differ markedly from the reality of the heightened state of airflow that develops during exertion. i.e. forced manoeuvres likely induce very different turbulent and thoracic pressure changes, in contrast to the hyperpnoea of real-life physical activity (i.e. walking or cycling). A current unanswered question is therefore, what happens to the large airway dynamic movement of healthy individuals (and ultimately patients) during real-life exercise and how does this compare with the measures taken during a forced manoeuvre, either during a bronchoscopy or during an imaging study such as CT or MRI scan. The key aim of this study is therefore to evaluate and characterise large airway movement in a cohort of healthy adults during a real-life exercise challenge and to compare this with findings from a dynamic expiratory MRI. In order to achieve this, the investigators proposes to develop and test the feasibility of an exercise-bronchoscopy protocol.

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