Different medications are often used in combination for the condition COPD (chronic obstructive pulmonary disease). Some medicines act by opening the airways (bronchodilators) and some act as anti-inflammatories (steroids). More recently an approach of using a combination inhaler (containing a steroid and a long-acting bronchodilator) at the same time as a long acting bronchodilator of a different group of medicines (anti-cholinergics inhalers) has been used. This approach is sometimes called 'triple therapy'. Studies which have looked at these combinations usually use only standard blowing tests (spirometry) to test these medicines and focus on the effects of the medicines at their highest (peak) levels. It is some ways more relevant to study these medicines towards to end of the dose period (trough)- just before the next dose. This is when there is less medicine in the system, and differences in drug effects are more obvious. There are also more detailed breathing tests than spirometry which get a more detailed picture of the way the lungs respond to bronchodilator medicines. The investigators have studied 'triple therapy' in COPD, by measuring the effects at the end of the dosing interval (trough) using a range of detailed respiratory tests.

Inclusion Criteria:

• Current or ex-smokers
• aged over 50years
• FEV1/FVC ratio less than 0.7
• FEV1 less than 60% predicted

Exclusion Criteria:

• Diagnosis of asthma, ABPA or bronchiectasis
• Recent RTI or steroid use
• Inability to perform study procedures or to give informed consent
• Known sensitivity to trial medications