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 a 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.
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’s reflex response (coughing back up the secretions) and their 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 seizureare at higher risk for developing pneumonia than the general population. As we age, our swallowing mechanism can become impaired as does our immune system. These factors, along with some of the negative side effects of medications, increase the risk for pneumonia in the elderly.
Once organisms enter the lungs, they usually settle in the air sacs and passages of the lung where they rapidly grow in number. This area of the lung then becomes filled with fluid and pus (the body’s inflammatory cells) as the body attempts to fight off the infection.
Most people who develop pneumonia initially have symptoms of a cold (upper respiratory infection, for example, sneezing, sore throat, cough), which are then followed by a high fever (sometimes as high as 104 F), shaking chills, and a cough with sputum production. The sputum is usually discolored and sometimes bloody. Depending on the location of the infection, certain symptoms are more likely to develop. When the infection settles in the air passages, cough and sputum tend to predominate the symptoms. In some, the spongy tissue of the lungs that contain the air sacs is more involved. In this case, oxygenation can be impaired, along with stiffening of the lung, which results in shortness of breath. At times, the individual’s skin color may change and become dusky or purplish (a condition known as “cyanosis”) due to their blood being poorly oxygenated.
The only pain fibers in the lung are on the surface of the lung, in the area known as the pleura. Chest pain may develop if the outer aspects of the lung close to the pleura are involved. This pain is usually sharp and worsens when taking a deep breath and is known as pleuritic pain or pleurisy. In other cases of pneumonia, depending on the causative organism, there can be a slow onset of symptoms. A worsening cough, headaches, and muscle aches may be the only symptoms.
Children and babies who develop pneumonia often do not have any specific signs of a chest infection but develop a fever, appear quite ill, and can become lethargic. Elderly people may also have few symptoms with pneumonia
Pneumonia may be suspected when the doctor examines the 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 the 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 samples can be collected and examined under the microscope. If the 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. As we have used antibiotics in a broader uncontrolled fashion, more organisms are becoming resistant to the commonly used antibiotics. These types of cultures can help in directed more appropriate therapy.
A blood test that measures white blood cell count (WBC) may be performed. An individual’s white blood cell count can often give a hint as to the severity of the pneumonia and whether it is caused by bacteria or a virus. 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, fungal infections, and some bacterial infections (like tuberculosis).
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 the doctor, and specimens from the infected part of the lung can be obtained.
Sometimes, fluid collects in the pleural space around the lung as a result of the inflammation from pneumonia. This fluid is called a pleural effusion. If a significant amount of fluid develops, it can be removed. Usually this is done by inserting a needle into the chest cavity and withdrawing the fluid with a syringe in a procedure called a thoracentesis. Often ultrasound is used to prevent complications from this procedure. 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. Today, most often, this involves surgery through a tube or thoracoscope. This is referred to as video-assisted thoracoscopic surgery or VATS.