Exploring the impact of chronic obstructive pulmonary disease (COPD) patient characteristics on inhaler device capability and inhaler device characteristics on treatment efficacy.

Part of the trial is observational and part interventional. Observational component: measurement of baseline characteristics at the start of a hospital admission for COPD exacerbation and assessing inhaler technique on admission and again at 6 weeks Interventional component: the trial is single blind (investigator), randomised cross-over trial. Stable, severe COPD patients are randomised to a sequence of inhaler devices (starting with Accuhaler or metered dose inhaler/spacer) delivering the same dose of medication (fluticasone propionate/salmeterol xinafoate SFC 500/50mcg, twice daily). The Accuhaler (also marketed as Diskus) is a round-shaped inhaler that the patient's often liken to a "spaceship" in appearance. The metered dose inhaler is the most commonly used "puffer" type recognised in the lay community. The Accuhaler is a type of dry powder inhaler (DPI) and is breath-actuated. For breath-actuated devices, the patient must generate sufficient inspiratory flow to overcome the intrinsic device resistance for effective actuation and drug deposition. Inherent resistance, and hence inspiratory flow requirement, varies by device. For the metered dose inhaler actuation is part of the device's own function and so this device is much less dependent on inspiratory flow rates. However, for this device, the coordination of actuation and inhalation is critical, and this problem can be largely overcome by using a volumatic spacer or "spacer". Hence, for both devices inhaler technique is important but for the Accuhaler, the patient must generate sufficient inspiratory flow to overcome the device's intrinsic resistance. After each of two consecutive six week exposure periods study outcomes are assessed. There is no washout between the two treatment exposures (the medication used in each treatment exposure is identical - the treatment exposure differ only in terms of the device used). The primary outcome is quality of life score via the Saint George Respiratory Questionnaire and secondary outcomes include exercise endurance (via the six minute walk test) and complex lung function testing. Treatment adherence is not formally assessed in this study, although inhaler technique, an aspect of treatment adherence, is assessed at baseline and prior to each six week exposure period.