The purpose of this research project is to study small airways physiological function in patients with chronic obstructive lung disease or COVID-19 and explore the relationship with in-vivo microanatomical small airway structure as measured by OCT. Correlating endobronchial assessment with multiple breath nitrogen washout and impulse oscillometry will allow the characterisation of the relationship between small airway structural findings and these validated investigations. A small volume lung wash, endobronchial brushings and the collection of a limited number of endobronchial cryobiopsy samples will be performed to better understand the endobronchial environment of the small airways through inflammatory studies. Following the completion of any such work, residual samples will be stored in a "bio-bank" to enable the completion of future work. Understanding the relationship with symptom-based quality of life scoring questionnaires and a functional assessment of exercise capacity will help elucidate the clinical impact of in-vivo small airways findings.

Inclusion Criteria:

1. Age 16 or over

2. Scheduled for bronchoscopy as part of clinical care or research protocol

3. No bleeding diathesis or therapeutic anticoagulation

4. COPD:

   • FEV1/FVC ratio <70% or

Asthma:

• Diagnosed by standard clinical methods
• Post-bronchodilator FEV1 ≥60% predicted or COVID-19 infection or previous COVID-19 infection (confirmed as per local guidelines)

Exclusion Criteria:

1. Unable to provide informed consent

2. Exacerbation of obstructive airways disease or respiratory infection requiring systemic antibiotics or corticosteroids in the 6 weeks prior to enrolment unless suffering from COVID-19 infection and bronchoscopy is required for clinical reasons

3. Contra-indications to performing lung function testing

   • Aortic aneurysm >6cm
   • Unstable cardiovascular disease (unstable angina, myocardial infarction or pulmonary embolism <4 weeks prior)
   • Severe aortic stenosis
   • Pneumothorax
   • Cerebral aneurysm
   • Thoracic or abdominal surgery <4 weeks prior

4. Contra-indications to passing oesophageal balloons

   • Oesophageal ulceration or varices
   • Sinusitis, recent nasal surgery or epistaxis

Subjects over the age of 16 with either chronic airflow obstruction or COVID-19