The evaluation of errors in use with different inhaler devices is challenging to quantify as there are a number of definitions of critical and non-critical errors with respect to inhaler use; in addition, performance characteristics of the device, such as airflow resistance, can also influence effective use in the real-world setting. Repeated observations and checking/correcting inhaler use are essential to optimise clinical effectiveness of inhaled therapy in patients. Breezhaler® is a single unit-dose dry powder inhaler used in chronic obstructive pulmonary disease and in asthma (budesonide) that has low airflow resistance, making it easier for patients of varying disease severities to achieve the inhalation flow rate required for lung deposition of treatment. Similar to Breezhaler®, the Aerolizer® is a single unit-dose dry powder inhaler used in asthma management with low airflow resistance. Studies have shown relatively low rates of critical errors with Breezhaler® and Aerolizer®, with similarities in the critical errors reported; these data on critical errors together with similarities in the usability of Breezhaler® and Aerolizer® further support the functional similarity between the two devices in both asthma and chronic obstructive pulmonary disease. Breezhaler® also has patient-feedback features, including use of a transparent drug capsule that can be checked after inhalation to see it is empty. The low resistance of the dose-confirming Breezhaler® results in less inspiratory effort being required by patients for its effective use, which allows the device to be used effectively across a wide age range of patients and disease severities.Read less <