Bronchitis is caused by inflammation of the large and medium airways of the lungs also known as bronchi. Bronchitis can be acute or chronic. Acute bronchitis usually develops from respiratory infections such as a cold. Normally, acute bronchitis resolves within several days without any lasting complications, however the cough may continue for weeks. If you have untreated acute bronchitis, it may develop into chronic bronchitis. Chronic bronchitis, a condition included in chronic obstructive pulmonary disorders (COPD) requires urgent medical attention to prevent more complications.