Patients admitted to hospital with an exacerbation of COPD and prescribed regular nebulised bronchodilators (combined salbutamol 2.5mg and ipratropium 0.5mg) will be recruited to the study. On one occasion between day 3-7 of admission they will perform pulmonary function testing namely measurement of Forced Expiratory Volume in 1 second(FEV1), Forced Vital Capacity (FVC), Inspiratory Capacity (IC) and cough peak flow. They will also complete the Borg breathlessness score. Measurements will be recorded at baseline (pre-bronchodilator administration) and one hour post-nebulised bronchodilator.