Pneumonia - Introduction

Introduction

Pneumonia is inflammation of the lung that is most often caused by infection with bacteria, viruses, or other organisms. Occasionally, inhaled chemicals that irritate the lungs can cause pneumonia. Healthy people can usually fight off pneumonia infections. However, people who are sick, including those who are recovering from the flu (influenza) or an upper respiratory illness, have a weakened immune system. This makes it easier for bacteria to grow in their lungs. It is one of the top 10 causes of death in the U.S. and the 6th leading cause of death in the elderly (65 and older).

Defining Pneumonia by Location in the Lung

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Pneumonia may be defined according to its location in the lung:

• Lobar pneumonia occurs in one part, or lobe, of the lung.
• Bronchopneumonia tends to be scattered throughout the lung.

Defining Pneumonia by Origin of Infection

Doctors often classify pneumonia based on where the disease is contracted. This helps predict which organisms are most likely responsible for the illness and, therefore, which treatment is most likely to be effective.

Community-Acquired Pneumonia (CAP). People with this type of pneumonia contracted the infection outside a hospital setting. It is one of the most common infectious diseases. It often follows a viral respiratory infection, such as the flu.

One of the most common causes of bacterial CAP is Streptococcus pneumoniae. Other causes include Haemophilus influenzae, mycoplasma, and Chlamydia.

Pneumonia Arising in an Institutional Setting

• Hospital-Acquired Pneumonia. Hospital-acquired pneumonia is an infection of the lungs contracted during a hospital stay. This type of pneumonia tends to be more serious, because patients in the hospital already have weakened defense mechanisms, and the infecting organisms are usually more dangerous than those encountered in the community. Hospital patients are particularly vulnerable to Gram-negative bacteria and staphylococci. Hospital-acquired pneumonia is also called nosocomial pneumonia.
• Ventilator-associated pneumonia (VAPP). A subgroup of hospital-acquired pneumonia is ventilator-associated pneumonia (VAP), a highly lethal form contracted by patients on ventilators in hospitals and long-term nursing facilities. Research finds that using endotracheal (breathing) tubes coated with silver might help to cut down on ventilator-associated pneumonia infections in the intensive care unit, because silver can kill bacteria and other microbes.
• Nursing-home acquired pneumonia. Pneumonia acquired in a nursing home or other long-term care facility is the second most common type of infection in these facilities, usually bacterial. It is sometimes difficult to diagnose as older populations are less likely to report fever, chills, and chest pain. Chest radiography and physical exam are necessary. Sputum sample and antigen tests may be helpful.

Click the icon to see an image of hospital-acquired pneumonia.