Pneumonia

Pneumonia is infection of the small air sacs of the lungs (alveoli) and surrounding tissues.

The infection causes inflammation and deterioration of lung function. The lungs become unable to easily transfer oxygen to the blood, increasing the work of breathing.

Pneumonia occurs in people of all ages. However, it occurs far more commonly in older people, in whom it tends to be far more serious. Younger people with pneumonia can often be treated at home, whereas most older people with pneumonia must be hospitalized because the infection tends to worsen quickly.

Pneumonia often affects only a portion of a single lung but can affect an entire lung or even both lungs. In many older people, the lung infection spreads beyond the lungs. The infection can enter the blood (sepsis).

When pneumonia occurs among people living in houses or apartments within a community, it is called community-acquired pneumonia. However, pneumonia is even more likely among older people who are hospitalized (hospital-acquired pneumonia) or living in institutional settings, such as nursing homes (nursing home-acquired pneumonia). Older people in hospitals or institutions often have weakened defenses against infection. Further, infections spread more efficiently in a closed environment.

Causes

Bacteria are the most common microorganisms that cause pneumonia. However, viruses and fungi cause pneumonia as well. These microorganisms are everywhere and are inhaled into the lungs all the time.

Certain characteristics and conditions make older people more likely to develop pneumonia. First, the system of cleansing the airways is not as effective as in younger people. Weakness may make coughing less vigorous. And, with aging, the immune system is weakened.

Among all older people, those at greater risk of developing pneumonia include the following:

• Those whose lungs have been damaged by smoking or chronic obstructive pulmonary disease (smoking irritates the lining of the lungs and paralyzes the cells that normally sweep and cleanse the airways)
• Those whose lungs have recently been irritated by a mild infection, such as a cold or, especially, influenza
• Those who have poor cough reflex or who are too weak (or who are in pain from recent surgery or an accident) to cough vigorously
• Those who are less able to fight off infections, such as those who are undernourished
• Those who are taking certain drugs, such as corticosteroids
• Those who have certain diseases, such as heart failure or diabetes
• Those who have cancer in or near the airways of the lungs (the cancer may block the airways and trap any microorganisms that have reached the air sacs)
• Those who are paralyzed (for example, by a spinal injury or stroke)
• Those who are unconscious (in part because they are unable to cough)

Microorganisms that produce pneumonia can end up in air sacs in several ways. In some cases, people inhale microorganisms (which are present in tiny droplets) when they are near someone already infected. Spread in hospitals and nursing homes often occurs this way.

Streptococcus pneumoniae (pneumococcus) is the most common bacterial cause of community-acquired pneumonia. Other common bacterial causes include anaerobic bacteria (which grow in the absence of oxygen), Haemophilus influenzae, and Legionella pneumophila (which causes a type of infection called Legionnaires' disease). Influenza virus and respiratory syncytial virus can also cause community-acquired pneumonia in older people, as can Mycobacterium tuberculosis, the microorganism causing tuberculosis. Although fungi can cause community-acquired pneumonia, they more commonly cause pneumonia in hospitalized patients who may be sick or debilitated (for example, cancer patients receiving chemotherapy).

Staphylococcus aureus, Klebsiella, Proteus, Escherichia coli, and Pseudomonas aeruginosa are bacteria that often cause pneumonia that develops in hospitalized or institutionalized people, such as those in nursing homes. Outbreaks of influenza and respiratory syncytial virus infection are also common in nursing homes. Tuberculosis occurs in this setting as well.

Prevention is the key!!!