Participant were asked to complete the ease of use questionnaire for the DPI once error assessment of each inhaler was completed. This was a series of 6 questions (Ease of use rating, Telling how many doses were left in inhaler, Learning how to use inhaler, Handling the inhaler, Preparing inhaler and Holding inhaler while using it). Each question had one response to choose from 5 options of ease of use (Very easy, easy, neutral, difficult and very difficult). Participants were asked to rate based on their ease of use experience with device using a scale ranging from 1 (very easy) to 5 (very difficult). A higher rating indicated that the inhaler was difficult to use and a lower rating indicated that inhaler was easier to use. This questionnaire was completed for the first device before moving to the critical errors assessment of the second device. Data has been categorized and reported as 'Very easy', 'Easy', 'Neutral', 'Difficult' and 'Very Difficult' with respect to each question.