Bronchitis is an acute inflammation of the air passages within the lungs. It causes a cough, shortness of breath and chest tightness. There are two main types of bronchitis: acute and chronic. Acute bronchitis is caused by the viruses that cause cold. Chronic bronchitis is a type of COPD. The inflamed bronchi produce a lot of mucus. This leads to cough and difficulty getting air in and out of the lungs.