SEARCH Articles Figures Tables Chronic Obstructive Pulmonary Chronic Obstructive Pulmonary Disease Chronic disease Chronic diseases obstructive pulmonary disease Chronic obstruction Chronic obstructive disease Chronic pulmonary Chronic pulmonary disease Disease control Disease control diseases Obstruction Obstructive Obstructive disease Pulmonary disease Pulmonary obstruction Randomization (randomized trials Randomized control trials Randomized trials