What is Bronchitis?
Bronchitis is defined as inflammation of the bronchi in the lungs. A healthy person normally inhales through the nose. The inhaled air passes from the nose into the trachea. Trachea, in simple terms means wind pipe. This wind pipe carries the air into the lungs, where the air is purified or the oxygen in the air is taken into the body and the carbon dioxide in the air is thrown out of the body through the exhaled air. The bronchi are air passages that connect the windpipe (trachea) to the lung tissue. The trachea connects to 2 main bronchi. These bronchi then branch many times to form a network of increasingly fine passages which are known as bronchi and bronchioles. This fine network of bronchi and bronchioles then ends at microscopic sacs called alveoli. Alveoli are air sacs where the exchange of oxygen and carbon dioxide takes place. Oxygen is taken up by the blood and the carbon dioxide from the blood is passed into the exhaled air.
Pathophysiology of Bronchitis
The bronchi are lined by mucous membrane. The mucus membrane secretes mucus. In bronchitis the mucus membrane of the bronchi becomes inflamed. As a result of this, there is excessive secretion of mucus by the bronchi. Hence the person suffering from bronchitis complains of cough and excess sputum.
Types of Bronchitis
Bronchitis can be classified into two major categories -acute bronchitis and chronic bronchitis. Another type of bronchitis is bacterial bronchitis.
- Acute Bronchitis
Acute bronchitis is an acute condition, in which the symptoms of bronchitis develop suddenly and the condition lasts for a relatively short period of time. The hallmark symptom of this condition is the development of a cough. The cough may or may not be present with the production of sputum. The major cause of acute bronchitis is a viral illness such as common cold, influenza or acute sinusitis. In these cases, the infection spreads into the respiratory tract and the bronchi are affected. This results in the development of acute bronchitis. Acute bronchitis may also occur when the immunity of the person is low, especially when he is recovering from a chronic illness, major surgery or a trauma.
- Chronic Bronchitis
Chronic bronchitis, as the name suggests is a chronic condition, which lasts for a longer period of time and the symptoms have a gradual onset. Chronic bronchitis is a type of COPD or chronic obstructive pulmonary disease. This is a chronic condition which is characterized by the presence of a productive cough. Productive cough means cough accompanied by sputum or expectorant. This cough must last for at least 3 months or more and for a period of 2 years in order for the health care professional to diagnose the person to be suffering from chronic obstructive pulmonary disease. The main causative factor in the development of chronic bronchitis is cigarette smoking. Cigarette smoke irritates the bronchi and the bronchioles. The mucus lining of the bronchi become inflamed as a response to the chronic irritation. They secrete more mucus resulting in productive chronic cough.
Image Source : Figure A shows the location of the lungs and bronchial tubes in the body. Figure B is an enlarged, detailed view of a normal bronchial tube. Figure C is an enlarged, detailed view of a bronchial tube with bronchitis. The tube is inflamed and contains more mucus than usual.