Symptoms such as cough, wheeze, and breathlessness are among the most common reasons for general practitioner or emergency department visits in the UK. Such symptoms have a profound impact on patients' ability to live a fulfilled life, often rendering people unable to work and socialise.

Azithromycin (a type of antibiotic) improves symptoms and reduces flare-ups of diseases such as asthma and chronic obstructive pulmonary disease (COPD). The reason why it works is unclear. Many people believe that it either decreases the number of bacteria in the lungs or reduces inflammation in the lungs and the upper airways. Neither theory is proven. Another possible mechanism that has been much less studied is that Azithromycin encourages the body to move food and fluid through the gut more quickly, thus preventing reflux and aspiration of small food particles and stomach acid. It has been shown that lung damage can occur when gut contents enter the airways, which may contribute chronic lung disease patients' symptoms

In this study the investigators will test the effect of azithromycin on the gut in patients with chronic lung diseases. The investigators will measure the strength of a patients swallow by measuring the pressures in their gullet, using high-resolution oesophageal manometry (HROM), before and after treatment, in people being started on azithromycin as part of their routine care. The investigators will also measure the effect that azithromycin has on their symptoms and observe whether there is a relationship between the strength of their swallow and their symptoms.

At the end of this study, the investigators hope to better understand the way in which azithromycin helps to improve the symptoms of patients with chronic lung diseases. The investigators also hope to open the door to investigate the effect of other drugs that improve gut function in patients with chronic lung diseases.

Inclusion Criteria:

• Males and females aged ≥18 years.
• Have a diagnosis of chronic respiratory disease (COPD, asthma, interstitial lung disease, chronic cough, cystic fibrosis, and/or bronchiectasis) confirmed by a respiratory consultant.
• Exhibit symptoms consistent with airway reflux, demonstrated by a score ≥14 on the Hull Airways Reflux Questionnaire
• Are being initiated on azithromycin as part of routine clinical care, as judged by their usual respiratory clinician. This will include all common treatment regimes, 250mg once daily, 250mg three times per week, and 500mg three time per week.
• Are willing and able to consent to all study procedures.

Exclusion Criteria:

• Previous treatment with long-term macrolides in the past 3 months.
• Unable to be investigated with HROM due to contraindications such as anatomical abnormalities or diseases of the oesophagus or unwilling/ unable to be investigated with HROM based on the clinical judgement of the investigators due to severity of lung disease.
• Have another cardiorespiratory cause for their symptoms (such as heart failure or lung cancer).
• Women of child bearing potential not using effective means of contraception.
• Are unable or unwilling to consent to or complete the study procedures.

All patients with chronic respiratory disease whose normal respiratory physician is considering initiating azithromycin therapy for.