Acute bronchitis

Acute bronchitis is the most common inflammatory lung disease.

 Acute bronchitis may result when infections of the upper airways spread via infected mucus to the airways of the lungs.

   Severity ranges from slight symptoms to severe respiratory impairment, which can be fatal.

   During influenza epidemics, acute bronchitis remains a major cause of death, particularly among the elderly and people with respiratory impairment.

Preventative measures and early treatment are extremely effective for preventing serious consequences of the disease.

What is acute bronchitis and what causes it?

Initial infection of the airways

The lungs and bronchial tree (the two bronchi and smaller bronchioles) form a continuous tract with the upper airways (the nasal passages, sinuses and throat). Infections of the upper airways may therefore spread via infected mucus to the large and small airways of the lungs. This is particularly true during viral infections, which are common during winter when colds or attacks of influenza may infect the upper and lower airways.

A viral infection tends to damage the outer layer of the lining of the airways, the epithelium. This may subsequently be shed, which in turn exposes small nerve fibres in the bronchial wall. Because of this process it is common to experience coughing and wheezing during the acute infection, but also for weeks to months after the infection has cleared up.

Secondary bacterial infection of the airways

The viral infection may temporarily paralyse the immune defence mechanism of the airways, making them vulnerable to secondary infection by bacteria. The bacterial infection may be more severe than the viral infection. Infiltration of defence cells known as neutrophils and macrophages into the wall of the airway is a mechanism whereby the body contains viruses and bacteria in the airway wall and prevents these from spreading to cause pneumonia.

Why you feel ill

An initial inflammatory response may contribute to a fever, a raw feeling over the major airways during coughing and production of yellow sputum (substance produced by coughing or clearing the throat). The sputum effectively represents dead neutrophils and macrophages, which are shed in mucus from the airways.

You feel ill during attacks of acute bronchitis because of the liberation of toxic substances from bacteria as well as liberation of enzymes and chemicals known as oxidant radicals. The latter are aimed at destruction of the infecting organism, but an "over-zealous" inflammatory reaction can cause local damage in the airway and also travel in the bloodstream and affect cells in other parts of the body.

The mucus production may block small airways. Swelling of the internal lining of the small airways may contribute to defective oxygenation of blood passing through the lungs, which will aggravate shortness of breath.

Other causes of inflammatory reaction

Other causes of inflammatory reaction of the upper and lower airways need to be considered. For example, allergic bronchitis may masquerade as recurrent attacks of viral bronchitis and have the same symptoms of cough with production of yellow sputum. The treatment of this condition is entirely different from that of acute viral or bacterial bronchitis.

Inhaled chemical substances can cause severe irritation of the bronchial tree and lead to a similar inflammatory response and symptoms.

Symptoms and signs of acute bronchitis

Symptoms usually commence during epidemics of colds or influenza. They are frequently first noticed in the upper airways and are characterised by mucus drainage from sinuses, a burning throat and a general feeling of ill health. There may also be a raised temperature. A dry cough may herald the onset of bronchitis and this may be followed within hours to days by the production of small amounts of white and eventually yellow sputum. You may experience discomfort over the main airways (trachea or large bronchi), which will be accentuated by coughing or wheezing.

People with bronchitis are frequently concerned when they notice blood streaks in the sputum. In the context of acute bronchitis, small amounts of blood are the result of inflamed bronchial walls on which pressure is exerted during coughing, with the subsequent rupture of minute vessels in the bronchial wall and leakage of small amounts of blood. This is by no means a life-threatening process.

Symptoms of bacterial infection

In the main, attacks of acute bronchitis in otherwise healthy individuals will resolve without requiring antibiotic treatment (i.e. to fight bacterial infection). It is extremely difficult to determine when viral bronchitis is followed by a secondary bacterial infection. The following symptoms indicate that further investigation and antibiotic treatment are needed:

       A prolonged cough (exceeding five to seven days)

       Larger volumes of bright yellow or green sputum

       Symptoms of systemic disease (i.e. the whole body is affected) such as a temperature above 38°C and a general feeling of illness.

Individuals who are prone to such secondary infections include smokers, whose airways are in a state of perpetual inflammation due to the chemical effect of cigarette smoke, and in whom mucus over-production is compounded by the infectious process. People who suffer from immunosuppression such as those with AIDS or on immunosuppressant drugs (e.g. chemotherapy or corticosteroids), malnourished people or individuals who abuse alcohol are prone to secondary bacterial infection and severe consequences of acute bronchitis, which may even terminate in death.

Elderly people over 70 may develop bronchitis and remain largely asymptomatic because they do not tend to mount an inflammatory response. They may not have an elevated temperature and very little cough, and may eventually "fade away" without a final diagnosis having been made.

Severity of acute bronchitis can vary from a virtually asymptomatic state to severe infection, respiratory failure, pneumonia and even death.

Recurrent attacks of acute bronchitis

This situation warrants specific attention, particularly when there are more than four attacks of acute bronchitis per year. Conditions such as allergic bronchitis, vocal cord damage with subsequent chronic aspiration, epileptic attacks or recurrent episodes of alcoholic stupor, immunosuppression and reflux of stomach contents are all specific conditions that need to be recognised and addressed to prevent ongoing recurrent attacks of acute bronchitis. Ongoing recurrent attcks can cause permanent lung damage and eventually death due to respiratory failure.

The doctor also needs to find out whether chronic infecting organisms such as tuberculosis are present; as well as chronic upper airway inflammation, such as sinusitis with a post nasal drip. These conditions can compromise the lung on a chronic basis. Once they have been identified and eliminated, patients do not have to take antibiotics on a regular basis.

People with the condition chronic obstructive pulmonary disease (COPD) are prone to recurrent bronchitis. COPD results in impaired expiratory airflow, increased mucus production, an audible wheeze and respiratory impairment (shortness of breath). These individuals are usually chronic or ex-smokers who tend to accept yellow sputum “as normal”. Attacks of acute bronchitis in people with COPD can be life-threatening if treatment is not received early.

Special investigations

Usually no special investigations are indicated during an attack of acute bronchitis, because of its self-limiting nature.

In the event of recurrent acute attacks, a sputum culture should be conducted, tests for allergy performed and an x-ray taken of the sinuses and chest.

If there are symptoms of recurrent heartburn and reflux of stomach contents, gastroscopy (using an optical tube to view inside the stomach) may be required. Treating heartburn may prevent further inflammation and irritation of the airways.

How is acute bronchitis treated?

Avoiding infected individuals; following a healthy diet with adequate vitamin A, C and E; and avoiding exertion during acute attacks are commonsense measures.

Bedrest is advised if you are experiencing symptoms of general fever and lassitude.

Indications for antibiotics have been mentioned previously. A general rule of “when in doubt” should be followed: antibiotic treatment is recommended for individuals who have respiratory impairment or immune deficiencies, and particularly the elderly.

When to call the doctor

It is wise to seek attention of a doctor if symptoms of bronchitis persist for longer than a day or two, particularly if you feel ill or short of breath. Individuals with impaired respiratory or immune function should consult a doctor without delay. As general rule, prevention and early treatment improve the chances of quick recovery and avoidance of permanent structural lung damage.

Any evidence of heart failure or respiratory failure, which causes blueness of the tongue and lips, necessitates admission to hospital.