Fig. 1From: Use of low-dose oral theophylline as an adjunct to inhaled corticosteroids in preventing exacerbations of chronic obstructive pulmonary disease: study protocol for a randomised controlled trialFlow diagram of study design and schedule. bd, Twice a day (Bis in die); CATest, COPD (Chronic Obstructive Pulmonary Disease) Assessment Test; EQ-5D, EuroQOL five-dimension questionnaire; MRC, Medical Research Council; od, Once a day (Omne in die)Back to article page