Pneumonia Health Article

Definition

Pneumonia is a serious infection of the lung that impairs breathing. Small air sacs in the lung (alveoli) become filled with pus, mucus or other fluid, and cannot supply oxygen to circulating blood. Lobar pneumonia affects one section, or lobe, of the lung; bronchial pneumonia, or bronchopneumonia, affects scattered areas of either lung.

Description

Pneumonia is not just one disease. Although it is commonly caused by Streptococcus pneumoniae, several different microorganisms—as well as toxic chemicals—or choking on food or vomit, can cause the disease.

An estimated four million Americans become ill with pneumonia each year, accounting for one million hospital admissions and over ten million hospital bed days. In the United States, pneumonia is the sixth most common disease leading to death. It is also the most common fatal infection acquired by already hospitalized patients. In developing countries, pneumonia ties with diarrhea as the most common cause of death.

Pneumonia is one of the most ancient known diseases. Although the incidence of pneumonia has declined because of the use of antibiotics, it has become a more serious health risk among elderly people. From 1980 to 1992, the overall death rate due to pneumonia increased by 20%. Nine out of every ten deaths due to pneumonia occurred among people aged 65 years and over.

Causes and symptoms

Pneumonia can have more than 30 different causes, but the five main causes are:

• bacteria
• viruses
• mycoplasmas
• other infectious pathogens, like fungi (including Pneumocystis)
• some chemicals

Common symptoms of pneumonia vary according to its cause, but may include:

• Cough. In bacterial pneumonia, the cough produces a rust-colored or greenish mucus. Pneumonia due to mycoplasmas produces only sparse whitish mucus, while viral pneumonia is generally characterized by a dry cough that worsens over time and ultimately produces a small amount of mucus that is purulent, or obviously infected.
• Fever (as high as 105°F, or 40.5°C) and chills.
• Localized pain in the area of the chest at the location of the lung infection; pain may be severe.
• Shortness of breath (SOB). (Severe pneumonia may cause cyanosis, or a bluish tinge to the skin, especially around the lips and nailbeds, due to lack of oxygen in the blood.)
• Chattering teeth.
• Profuse sweating.
• Rapid breathing and pulse.
• Confused mental state.
• Muscle pain and weakness.

Anatomy of the lung

To better understand pneumonia, it is important to be familiar with the basic anatomic features of the respiratory system. The human respiratory system begins at the nose and mouth, where air is breathed in (inspired) and out (expired). The air tube extending from the nose is the nasopharynx. The tube carrying air breathed in through the mouth is the oropharynx. The nasopharynx and the oropharynx merge into the larynx. The oropharynx also carries swallowed substances, including food, water, and salivary secretion, which must pass into the esophagus and then the stomach. The larynx is protected by a trap door called the epiglottis, which prevents substances that have been swallowed, as well as substances that have been regurgitated (thrown up), from heading down into the larynx and toward the lungs.

The larynx flows into the trachea, which is the broadest part of the respiratory tree. The trachea divides into two tree limbs, the right and left bronchi. Each one of these branches off into multiple smaller bronchi, which penetrate the lung tissue. Each bronchus divides into tubes of smaller and smaller diameter, finally ending in the terminal bronchioles. The air sacs of the lung, in which oxygen-carbon dioxide exchange actually takes place, are clustered at the ends of the bronchioles like the leaves of a tree. They are called alveoli.

The tissue of the lung, which serves only in a supportive role for the bronchi, bronchioles, and alveoli, is known as lung parenchyma.

Function of the respiratory system

The main function of the respiratory system is to provide oxygen, the most important energy source for the body's cells. Inspired air (the air that is breathed in) contains oxygen and travels down the respiratory tree to the alveoli. The oxygen moves out of the alveoli and is sent into circulation throughout the body as part of the red blood cells. The oxygen in the inspired air is exchanged within the alveoli for carbon dioxide, the waste product of the human metabolic process. The air that is breathed out contains the gas carbon dioxide. During expiration, carbon dioxide leaves the alveoli. As one breathes in oxygen, one breathes out carbon dioxide.