Sputum induction is considered a relatively non-invasive, reliable procedure, which can be utilised to characterise the inflammatory profile of the airways.

However, the procedure can be slightly uncomfortable for patients. This study aims to assess the differences in participants' tolerability of sputum induction, by comparing two different nebulisers when performing the procedure.

This is a single centre, crossover study to compare the use of two nebulisers in the sputum induction procedure. 54 participants with stable asthma or COPD will be recruited and will attend 2 visits, at least 48 hours apart. Differences in the quality and quantity of samples and the time taken to produce a sample will be described. The main purpose is to explore the optimum device to perform the procedure, whilst protecting the safety of participants and maximising their comfort.

If participants are unable to produce a sputum sample after completion of the induction procedure, physiotherapy techniques may be performed. This is an exploratory objective to establish whether these techniques may help in the event of unsuccessful procedures.

Inclusion Criteria:

• Have an ability to provide fully informed consent.
• Have a diagnosis of asthma or COPD.
• Male or female.
• Age between 18 to 75 years.

Exclusion Criteria:

• Have a post bronchodilator Forced Expiratory Volume in the first second of less than 1 litre or less than 50 percent of the predicted value.
• Have an exacerbation of asthma or COPD within the 30 days prior to the first visit.
• Have a history or current evidence of an upper or lower respiratory infection, within the 30 days prior to the first visit.
• Have any other clinically significant medical disease or uncontrolled concomitant disease, that is likely, in the opinion of the investigators to impact on the ability to participate in the study.