Bronchitis. Illustration of the lungs showing the effects of bronchitis. The air passages (bronchi) cutaway at right are inflamed and filled with sputum (phlegm, yellow). At upper left is the cartilageringed trachea, which splits to form the main bronchi of each lung. One symptom of bronchitis is the coughing up of sputum produced within the bronchi in response to the infection or irritation causing the inflammation. The disease also causes shortness of breath because the airways become narrowed. Bronchitis is associated with both smoking and air pollution. With chronic bronchitis there is no cure and the functioning of the lungs steadily becomes reduced.