<unk>  is an inflammation of the bronchi (medium and large size airways). Acute<unk>  is a self-limiting disease caused by viruses or bacteria. Chronic<unk>  is a disease by definition and is part of chronic obstructive pulmonary disease (COPD) which is defined as productive cough for at least three months in two consecutive years. Inflammatory response of the bronchial epithelium to infections or irritants that involve the medium and large size airways results in thickening of the bronchial and tracheal mucosa. Hallmark features of chronic<unk>  pathophysiology include: hyperplasia and hypertrophy of the goblet cells of the airway, resulting in an increase in secretion of mucus which contributes to the airway obstruction.  
Microscopically there is infiltration of the airway walls with inflammatory cells, particularly neutrophils. Inflammation is followed by scarring and remodeling that thickens the walls resulting in narrowing of the small airway. Further progression leads to metaplasia and fibrosis of the lower airway. The consequence of these changes is a limitation of airflow. 
Acute<unk>  affects young children and old people. Its overall incidence is approximately 5% in the U.S. There is no racial or gender predilection for this disease.Although, Chronic<unk>  is common among geriatric patients. It occurs more commonly among Caucasian individuals compared to other races, but equally between males and females.
Age, season of the year and the immunization status are the main determining risk factors for acquiring acute<unk> . The most potent risk factor in the development of chronic<unk>  is cigarette smoking. Other risk factors are occupational pollutants, such as cadmium, silica, and air pollutants, and genetic factors, such as alpha 1 antitrypsin deficiency
Acute<unk>  is a self limiting lower respiratory tract infection that usually presents with cough that lasts for up to 3 weeks. Chronic<unk>  usually gradually worsens over time and can result in death. The rate of deterioration varies between individuals and depends on the level of airflow obstruction. Prognosis is dependent on early recognition and smoking cessation, which improves the outcome significantly. Cigarette cessation, hand hygiene, vaccination and reduction in occupational exposure are the mainstays to decrease the severity and the risk of<unk> .
Bronchitis
Tracheitis
Mediastinitis
Hydrothorax
Croup
Lung abscess
Bronchiolitis
Pleurisy