Pneumonia

Pneumonia is an infection within the lung that is usually confined to just one lobe of the lung (called lobar pneumonia). The infection causes the affected alveoli and small bronchioles to become inflamed. Furthermore, pus and other substances are produced and accumulate in the affected alveoli. Alveoli that are filled with pus have decreased space available for gas exchange.

Causes
Pneumonia is usually caused by bacteria, although less commonly it may be because of a virus, fungus, or other infectious organism. Usually, the infectious organism is inhaled into the lungs from the mouth or nose. 

Risk Factors
Smoking cigarettes is a risk factor for developing an infection in the lungs. People have a higher susceptibility to developing infection if they have impairment of the immune system, such as with advanced age, malnutrition, diabetes, chronic kidney disease, or human immunodeficiency virus (HIV) infection. Poor dental or oral hygiene is another predisposing factor.

Signs and Symptoms
Signs and symptoms will vary according to the severity of the disease. There will be variable degrees of shortness of breath and a decrease in oxygen saturation. There may be a persistent cough. The cough may be a productive cough, producing green or yellow sputum. There may be fever, malaise and chest discomfort.

Investigations
Oxygen saturation should be frequently monitored.

Auscultation of the lungs may give varied findings, such as crackles, rhonchi, wheeze and decreased breath sounds.

Chest x-ray helps to diagnose lobar pneumonia. The x-ray will show the pus and other substances in the affected lung lobe, which has a cloudy white appearance on the x- ray. Here are some examples of chest x-rays showing infection in different lobes:

   

Blood tests may include white blood cell (WBC) count, and inflammatory markers (such as CPR and ESR).

A sputum culture is useful to identify the organism that is causing the infection, and helps to determine which antibiotic is best.

Blood culture is used to determine whether the infection has spread from the lungs into the blood stream.

Treatment
Oxygen should be given to any patient that is short of breath.

Antibiotics are given to treat bacterial pneumonia. Rarely, other antimicrobials may be required depending on the organism suspected.

The patient should be encouraged to breathe deeply to ventilate all the areas in the lungs. Patients with chest discomfort have shallow breathing and do not cough effectively; therefore adequate analgesia should be given. Patients who are bedbound should be given regular positional changes to allow for ventilation of all lung lobes.

Good hydration helps to loosen secretions, enabling them to be coughed up easier. Depending on the patients other co-morbidities, it may be appropriate to increase in the patient’s oral intake of fluids, or to commence intravenous fluids.

Severe cases of pneumonia may require intubation and mechanical ventilation.

Complications
Pneumonia has the potential to spread and become a severe infection affecting the whole body. Sepsis should be treated aggressively with antibiotics and intravenous fluids. Inotropes (such as dopamine) may be required.