Patients with asthma and chronic obstructive airways disease (COPD) undergo routine testing of their lung function in the diagnosis, progression, management and, response to treatment of their disease. Standard lung function obtains measurements based on the forced flow of air moving within the airways. Such measurements give a reasonable assessment of disease affecting the large airways, but not an accurate estimate of small airways disease. Small airways are less than 2mm in diameter. However, both asthma and COPD have disease that involves not only the large but also the small airways that has important clinical consequences. Indeed, COPD predominantly affects the small airways.~Tiotropium (Spiriva, Boehringer Ingelheim), a long-acting inhaled anticholinergic bronchodilator, improves lung function, quality of life, and exercise endurance and reduces exacerbations in patients with chronic obstructive pulmonary disease (COPD).~Respimat Soft MistTM Inhaler (SMI) is a novel inhaler delivering a unique slow-moving Soft MistTM that allows gentle inhalation - making it easy to inhale. Importantly it has drug particles that are ~ 2microns that allow an increase in the total lung deposition of drug (~52%) and also the potential for penetration to treat the small and large airways in patients with COPD; that is targeting the whole airway tree.~RESEARCH AIM & HYPOTHESIS The aim is to investigate the effect of tiotropium from different devices on a panel of small (IOS, MBNW, DLCO, FVC) and large airway (FEV1, PEF) responses in patients with mild-moderate COPD. The investigators will compare Tiotropium Handihaler 18 micrograms once daily with Tiotropium Respimat 5 micrograms once daily.~The investigators will identify a COPD cohort with ongoing symptoms or exercise limitation on HandiHaler, as proposed. The science behind this is why are people still limited (even if partially as determined using the CAT score) and is more distal airway targeting necessary? This doesn't necessarily mean targeting the acinar/alveolar beyond the terminal bronchioles, but just a little bit deeper into the distal conducting airway. This can be achieved with Respimat.
The aim of the study is to investigate the effect of tiotropium from different devices on a panel of small (IOS, MBNW, DLCO, FVC) and large airway (FEV1, PEF) responses in patients with mild-moderate COPD. Comparisons will be made between Tiotropium Handihaler 18 micrograms once daily and Tiotropium Respimat 5 micrograms once daily