Bronchitis is an inflammation of the main air passages to the lungs. Bronchitis may be short-lived (acute) or chronic, meaning that it lasts a long time and often recurs.

Acute bronchitis generally follows a viral respiratory infection. Initially, it affects your nose, sinuses, and throat and then spreads to the lungs. Sometimes, you may get another (secondary) bacterial infection in the airways.This means that bacteria infect the airways, in addition to the virus.

People at risk for acute bronchitis include:

• Elderly, infants, and young children
• Smokers
• People with heart or lung disease

Chronic bronchitis is a long-term condition. People have a cough that produces excessive mucus. To be diagnosed with chronic bronchitis, you must have a cough with mucus most days of the month for at least 3 months.

Chronic bronchitis is also known as chronic obstructive pulmonary disease, or COPD for short. (Emphysema is another type of COPD.) As the condition gets worse, you become increasingly short of breath, have difficulty walking or exerting yourself physically, and may need supplemental oxygen on a regular basis.

Cigarette smoke, including long-term exposure to second-hand smoke, is the main cause of chronic bronchitis. The severity of the disease often relates to how much you smoked or how long you were exposed to the smoke.

The following things can make bronchitis worse: Air pollution, certain occupations (like coal mining, textile manufacturing, or grain handling), infection, and allergies.

The symptoms of either type of bronchitis include:

• Cough that produces mucus; if yellow-green in color, you are more likely to have a bacterial infection
• Shortness of breath worsened by exertion or mild activity
• Wheezing
• Fatigue
• Fever -- usually low
• Chest discomfort

Even after acute bronchitis has cleared, you may have a dry, nagging cough that lingers for several weeks.

Additional symptoms of chronic bronchitis include:

• Frequent respiratory infections (such as colds or the flu)
• Ankle, feet, and leg swelling
• Blue-tinged lips from low levels of oxygen

• Rales (abnormal sounds in the lungs) or other abnormal breathing sounds may be heard by your doctor on lung examination with a stethoscope.
• Pulmonary (lung) function tests provide information useful for diagnosis and prognosis.
• Pulse oximetry is a device connected to your finger that displays the amount of oxygen in your blood.
• Arterial blood gas is a more exact (but more painful and invasive) measurement of oxygen and carbon dioxide levels.
• Chest x-ray 
• Sputum samples  may be taken, to check for evidence of inflammation or bacterial infection .