What is pneumonia?
Lungs are two spongy organs in the chest enveloped in a thin membrane called the pleura. About 90% of the lung is filled with air, only 10% is solid tissue. When a person breathes in, the air travels down the trachea or windpipe into its branches called bronchi. These again branch into a million small air passages called bronchioles that connect to over three million miniature sacs filled with air called alveoli. It is in the alveoli that oxygen and carbon dioxide are exchanged between the inhaled air and the blood leading to oxygenation of the blood and removal of carbon dioxide from the body.
Pneumonia is an inflammation of the lungs caused by infection with bacteria, viruses or other organisms. Usually these organisms enter the lungs through the air that is breathed. Pneumonia may also be caused from infections that spread to the lungs through the blood stream from other parts of the body.
The body's defence mechanisms normally protect the lungs from infection. If these mechanisms are weakened as in patients with chronic illnesses such as malignancy, diabetes, HIV infection, alcoholism, liver cirrhosis and asthma, then bacteria or other organisms produce pneumonia.
What are the causes of pneumonia?
Bacteria are the commonest cause, but pneumonia may also be due to viruses and other organisms. Streptococcus pneumoniae or pneumococcus is the most common bacteria, accounting for nearly half the cases. Other bacteria may cause pneumonia in hospitalised or very sick patients, in children with cystic fibrosis, and in people with chronic lung conditions. Tuberculosis is also one of the important causes of pneumonia.
What are the symptoms?
The symptoms of bacterial pneumonia include fever, chest pain, cough, chills, shortness of breath and rapid breathing. Older people may be very sick yet may have few symptoms. Coughing up sputum or phlegm containing pus or blood is an indication of serious infection. In very sick cases, the skin may appear bluish (cyanosis), breathing is laboured and heavy and the patient is confused due to insufficient oxygen in the blood.
What are the complications?
- Bacteraemia - Bacteria may enter the blood stream, making the patient very sick. This is the most common complication.
- Pleural effusion and empyema - The pleura has two thin layers enveloping the lung. Between the layers there is normally a small amount of fluid that helps lubricate the lungs. In some patients with pneumonia, this fluid increases (pleural effusion) and may even get infected and become pus, a condition called empyema.
- Pneumothorax and collapsed lung - Air may leak into the space between the pleural membranes causing pneumothorax. This exerts pressure on the lungs resulting in their collapse.
- Other complications - In rare cases the infection may spread from the lungs to other parts of the body causing abscesses or pus collections in the brain and elsewhere. Acute respiratory distress syndrome or ARDS is a specific condition in which the lungs are unable to function and oxygen is so severely reduced that the patient's life is at risk. For support the patient needs to be put on a ventilator, a machine that artificially helps the patient to breathe.
How is it diagnosed?
In many cases the physician is able to make a diagnosis on the clinical history and physical examination. Sometimes, the physician may advise blood tests and sampling of the sputum or phlegm that is coughed up. A chest X-ray is done to confirm the diagnosis and identify if there is pleural effusion. CT scan may be necessary in some instances.
Sometimes, obtaining fluid from the pleural space (with syringe and needle) or inserting a flexible bronchoscope into the trachea under local anaesthesia may be necessary for diagnosis and treatment.
How is it treated?
For severe pneumonia, antibiotics are administered into the vein (intravenous). These may be given for 5 to 10 days or even longer. All antibiotics carry some risk for allergic reactions, which can be serious in some cases. Some commonly used antibiotics include penicillins, ampicillin, amoxycillin, cephalosporins and aminoglycosides.
Fever may need to be controlled by acetaminophen or ibuprofen. Steam inhalation helps soothe the air passages and relieve cough. Patients with lung abscess, empyema or other complications may require an operation.
Chest physiotherapy including coughing, deep breathing exercises and chest tapping are important to help remove the mucous and pus from within the lungs.
Can pneumonia be prevented?
A healthy diet, regular physical exercises and deep breathing exercises, all help maintain the body's defence mechanisms. One must avoid close contact with people who have flu or cold, or are coughing.