What is Pneumonia?

Pneumonia is an inflammation of the parenchyma of the lungs. In the US, it is the leading cause of mortality from infection origin. Overally, it is number seven. Pneumonia is commonly caused by infections.

Classification

Pneumonia can be classified anatomically, aetiologically or according to the area of acquisition.

The anatomic classification of pneumonia includes lobar and broncho-pneumonia. Lobar pneumonia affects the lobes of the lungs whereas bronchopneumonia affects the bronchus or the bronchi of the lungs.

Etiology means cause. Therefore etiological classification is the classification according to the causative agent. It includes bacterial, fungal and aspiration pneumonia.

In classification according to the area of acquisition, there are hospital and community acquired pneumonia. This is the most widely used method of classification.

One is diagnosed of community acquired pneumonia if he or she has not been hospitalized for the last 14 days. On the other hand, one can contract hospital acquired pneumonia 48 hours after admission and up to 14 days after discharge.

The use of typical and atypical type of classification is no longer considered very much.

Common causative agents of hospital acquired pneumonia (HAP) include; Streptococcus pneumoniae, Haemophilus influenzae, Escherichia coli, Klebsiella, Serratia spp, Staphylococcus aureus, Acinetobacter and Pseudomonas aeruginosa.

For Community acquired pneumonia (CAP), the common causative agents are; Streptococcus Pneumoniae, Mycoplasma Pneumoniae, Haemophilus influenzae, Staphylococcus aureus, Legionella species, Chlamydophila pneumoniae, Chlamydophila Psittaci, Coxiella Burnetti and Mycobacterium tuberculosis.

Viral causes may include; Respiratory syncitial virus (RSV), Influenza A and B, Parainfluenza viruses, Adenoviruses and Measles and Metapneumovirus.

Predisposing factors for pneumonia

These are the factors that put you at an increased risk of contracting pneumonia. They include:

  1. Overcrowding. This facilitates droplet inhalation. The droplet may be containing the causative agent.
  2. Suppriession of the immune system commonly by HIV and some drugs like corticosteroids.
  3. Hospitalization. Hospitalized patients are mostly stationery and not moving around because they spend most of their time in bed.
  4. Intake of alcohol.
  5. Indoor pollution, for example in industries such as cement factories. If the workers lack proper PPEs, they become even at greater risks of contracting pneumonia.
  6. Extremes of ages such as those too old and those too young. Children especially those below five years of age have not yet developed a very strong immunity. Old people may be having diminished immunity. These two groups of people cannot therefore effectively fight infections.
  7. Chronic diseases of the lungs such as asthma.
  8. Other infections of the upper respiratory tract, for example the influenzae virus.

Mode of Spread

  1. Inhalation of droplets containing microbes. These microbes gain direct entry into the alveoli.
  2. Aspiration of GI contents and organisms from the pharyngeal region into the lungs.
  3. Local/direct spread from a near site within the body.
  4. Hematogenous spread from a distant site but within the body. This occurs through blood.

Clinical features

Symptoms

  1. Fever
  2. Malaise
  3. Weight loss
  4. Pleuritic chest pain
  5. Acute illness
  6. Cough with expectoration
  7. Confusion
  8. Breathing difficulty
  9. Headache
  10. Abdominal pain

Signs

  1. Tachypnoea meaning increased respiratory rate.
  2. Tachycardia meaning increased heart rate.
  3. Hypotension, i.e low blood pressure.
  4. Delirium
  5. Herpes labialis. Herpes Simplex Virus and Streptococcus pneumoniae normally have a correlation.

Investigations done for diagnosis of pneumonia

  1. Sputum specimens for microscopy, culture and sensitivity. This is done to observe the microorganisms present in the sputum.
  2. Blood cultures.
  3. Chest X-ray. This will often show opacities because the inflammation in the lung blocks passage of the X-rays. Pleural effusion can also be detected.
  4. Bronchoscopy.
  5. Eosinophil sedimentation rate
  6. Urine antigen test to detect Legionella and Pneumococcus. Legionella will often be present in patients who do normadic pastoralism.
  7. Complete blood count. With these, you will often find elevated white blood cells. This test can be used to distinguish between viral and bacterial pneumonia.
  8. Liver function tests
  9. Blood cultures.
  10. Arterial blood gas. Pneumonia may complicate and cause respiratory alkalosis. It may also complicate septicaemia leading to multiple organ failure.

However, not all these investigations are needed for pneumonia diagnosis.

There is a method of scoring known used as a guide for management. It assesss the severity of pneumonia. This method is known as CURB-65. Each letter stands for a specific word as shown below:

Each feature is assigned 1 score. A person having a score of 0-1 is treated as an outpatient. One with scores of 2 is treated as in-patient and admitted to the ward. With scores 3 and above, the patient is admitted to the ICU.

Differential diagnosis of pneumonia

These are the diseases that must be ruled out before ascertaining that one has pneumonia. They are:

  1. Pulmonary tuberculosis
  2. Pulmonary oedema
  3. Pulmonary infarction
  4. Carcinoma of the bronchoalveolar cells.

Treatment of Pneumonia

The most important factors to be considered for management of pneumonia are:

  1. Oxygen supplementation - Oxygen is given to maintain the PaO2 at or above 60mmHg.
  2. Fluid balance - intravenous fluids are given to hydrate patients especially those who are severely ill. Other patients are encouraged to maintain an adequate oral fluid intake.
  3. Antibiotic therapy - there is usually no time to await for culture results and so broad spectrum antibiotics are given for use in a 7-14day course depending upon the severity. Non-severe pneumonia is treated with Empirical drugs like Amoxicilin and for the severe pneumonia, Clarithromycin and Co-amoxiclav is used.

Prevention

  1. Avoid overcrowding
  2. Proper hygienic measures
  3. Use of prophylactic broad spectrum antibiotics
  4. Pneumococcus and influenza vaccination
  5. Avoid indoor pollution of air, e.g by use of chimneys to direct smoke out of the house in the low economic countries where people use firewood to cook.
  6. Quit smoking.
  7. Proper nutrition to strengthen your immune system.

Complications of pneumonia

These are diseases or illnesses that result if pneumonia if not effectively managed. They include:

  1. Lung abscess
  2. Lung collapse
  3. Lung fibrosis
  4. Empyema
  5. Septicaemia
  6. Menengitis
  7. Pleural effusion
  8. Pneumothorax