The inspiratory flow rates achieved by the COPD patients, via the breath actuated devices, are one of the important factors that can influence the efficiency of the drug delivery by the inhalation route. The peak inspiratory flow (PIF) rates achieved by COPD patients through different breath actuated dry power inhalers may differ because of the differences in internal resistance of the different type of devices. The results of inspiratory airflow rate and pressure drop over time, from this study, will provide an assessment of the range and variability of inhalation profile characteristics generated by COPD patients within the population selected for this study (e.g. demographics, gender, disease control) through the Breezhaler and the other marketed comparator DPIs.