This study is a prospective, single-centre, open, randomised study to improve management of acute COPD exacerbation within the Emergency Department. Adults with severe COPD are randomised into 2 groups: vibrating mesh nebuliser or standard jet nebuliser treatment. Salbutamol (5mg) and Ipratropium (0.5mg) will be administered via Aerogen Ultra via valved mask or a standard jet nebuliser via open face mask/. Two further doses of salbutamol to be delivered.