What is pneumonia? Pneumonia is an infection of one or both lungs which is usually caused by bacteria, viruses, or fungi. Prior to the discovery of antibiotics one-third of all people who developed pneumonia subsequently died from the infection. Currently, over 3 million people develop pneumonia each year in the United States. Over half a million of these people are admitted to a hospital for treatment. Although most of these people recover approximately 5% will die from pneumonia. Pneumonia is the sixth leading cause of death in the United States.

How do people "catch" pneumonia? Some cases of pneumonia are contracted by breathing in small droplets that contain the organisms that can cause pneumonia. These droplets get into the air when a person infected with these germs coughs or sneezes. In other cases pneumonia is caused when bacteria or viruses that are normally present in the mouth, throat, or nose inadvertently enter the lung. During sleep it is quite common for people to aspirate secretions from the mouth, throat, or nose. Normally, the body reflex response (coughing back up the secretions) and immune system will prevent the aspirated organisms from causing pneumonia. However, if a person is in a weakened condition from another illness a severe pneumonia can develop. People with recent viral infections, lung disease, heart disease, and swallowing problems, as well as alcoholics, drug users, and those who have suffered a stroke or seizure are at higher risk for developing pneumonia than the general population.

Once organisms enter the lungs they usually settle in the air sacs of the lung where they rapidly grow in number. This area of the lung then becomes filled with fluid and pus as the body attempts to fight off the infection.

What are pneumonia symptoms and signs? Most people who develop pneumonia initially have symptoms of a cold which are then followed by a high fever (sometimes as high as 104 degrees F), shaking chills, and cough with sputum production. The sputum is usually discolored and sometimes bloody. People with pneumonia have become short of breath. The only pain fibers in the lung are on the surface of the lung in the area known as pleura. Chest pain may develop if the outer pleural aspects of the lung are involved. This pain is usually sharp and worsens when taking a deep breath known as pleuritic pain.

In other cases of pneumonia there can be a slow onset of symptoms. A worsening cough, headaches, and muscle aches may be the only symptoms. In some people with pneumonia coughing is not a major symptom because the infection is located in areas of the lung away from the larger airways. At times, the individual's skin color may change and become dusky or purplish (a condition known as cyanosis) due to its blood being poorly oxygenated.

Children and babies who develop pneumonia often do not have any specific signs of chest infection but develop a fever, appear quite ill, and can become lethargic. Elderly people with pneumonia may also have few symptoms.

How is pneumonia diagnosed? Pneumonia may be suspected when a doctor examines a patient and hears coarse breathing or crackling sounds when listening to a portion of the chest with a stethoscope. There may be wheezing or the sounds of breathing may be faint in a particular area of the chest. A chest X-ray is usually ordered to confirm the diagnosis of pneumonia. The lungs have several segments referred to as lobes, usually two on the left and three on the right. When pneumonia affects one of these lobes it is often referred to as lobar pneumonia. Some pneumonias have a more patchy distribution that does not involve specific lobes. In the past, when both lungs were involved in the infection the term "double pneumonia" was used. This term is rarely used today.

Sputum samplescan be collected and examined under the microscope. If pneumonia is caused by bacteria or fungi the organisms can often be detected by this examination. A sample of the sputum can be grown in special incubators and the offending organism can be subsequently identified. It is important to understand that the sputum specimen must contain little saliva from the mouth and be delivered to the laboratory fairly quickly. Otherwise, overgrowth of noninfecting bacteria may predominate.

A blood test that measures white blood cell count (WBC) may be performed. An individual's WBC can often give a hint as to the severity of pneumonia and whether it is caused by bacteria or viruses. An increased number of neutrophils, one type of WBC, is seen in bacterial infections whereas an increase in lymphocytes, another type of WBC, is seen in viral infections.

Bronchoscopy is a procedure in which a thin, flexible, lighted viewing tube is inserted into the nose or mouth after a local anesthetic is administered. The breathing passages can then be directly examined by a doctor and specimens from the infected part of the lung can be obtained.

Pleural effusion. Sometimes fluid collects in the pleural space around the lung as a result of the inflammation from pneumonia. . This fluid is called pleural effusion. If the amount of this fluid that develops is large enough it can be removed by inserting a needle into the chest cavity and withdrawing the fluid with a syringe in a procedure called a thoracentesis. In some cases this fluid can become severely inflamed (parapneumonic effusion) or infected (empyema) and may need to be removed by more aggressive surgical procedures.

Conclusions. Pneumonia can be a serious life-threatening infection. This is true especially in the elderly, children, and those who have other serious medical problems such as chronic obstructive pulmonary disease (COPD), heart disease, diabetes, and certain cancers. Fortunately, with the discovery of many potent antibiotics most cases of pneumonia can be successfully treated. In fact, pneumonia can usually be treated with oral antibiotics without the need for hospitalization.




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