Definition

Pneumonia is an infection of the lungs. It affects the lower respiratory tract. This includes small bronchi (airways) and air sacs in the lungs.

Development of Pneumonia in the Air Sacs of the Lungs

The normal exchange of gases is interrupted by the build up of fluids.

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Causes

There are three main causes:

• Bacterial pneumonia—caused by bacteria, most commonly Streptococcus pneumoniae
• Viral pneumonia—caused by a virus (responsible for half of all pneumonias)
• Atypical bacterial pneumonia]]> —often called "walking pneumonia but can cause a more serious or potentially fatal pneumonia; caused by:
  • Mycoplasmahis
  • Chlamydias
  • Other tiny infectious agents that have traits of both bacteria and viruses

Other causes of pneumonia include:

• Fungal infections, such as ]]>Pneumocystis carinii pneumonia]]> (PCP)—a fungal infection common in people with ]]>AIDS]]>

Pneumonias are sometimes described by where it was acquired and how you were exposed to it:

• Community-acquired pneumonia—acquired in the community (eg, at school, work, gym)
• Nosocomial pneumonia—acquired during a hospitalization
  • Can be very dangerous, especially for patients on a ventilator
• ]]>Aspiration pneumonia]]> —happens when a foreign matter (often stomach content) is inhaled

Aspiration

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Risk Factors

Factors that increase your chance of pneumonia include:

• Age: 65 or older
• Flu]]> or other respiratory illness
• Chronic illness, such as heart or lung disease
• ]]>Stroke]]> (aspiration pneumonia due to difficult swallowing)
• Weakened immune system caused by AIDS or ]]>chemotherapy]]> treatment
• ]]>Chronic bronchitis]]>
• Malnutrition
• Pregnancy
• Infants and very young children
• Alcohol or drug abuse
• Smoking
• Chronic exposure to certain chemicals (eg, work in construction or agriculture)

Symptoms

Symptoms of pneumonia may include some or all of the following:

Diagnosis

The doctor will ask about your symptoms and medical history. A physical exam will be done. Diagnosis is based on symptoms and listening to your chest. Tests may include:

• Chest x-ray]]> —a test that uses radiation to take pictures of structures inside the body, in this case the chest
• ]]>CT scan]]> —a type of x-ray that uses a computer to make pictures of structures inside the chest
• Blood tests
• ]]>Bronchoscopy]]> —direct examination of airways
• Sputum culture—testing mucus coughed up from deep in the lungs
• Pulse oximetry—measures the amount of oxygen in the blood
• Arterial blood gas—measures oxygen, carbon dioxide, and acid in the blood

Treatment

Treatment of pneumonia depends on:

• Type of pneumonia
• Severity of symptoms
• Other factors

Common methods of treatment include:

Prevention

Certain vaccines may prevent pneumonia:

• Flu shot]]> —for people at high risk, particularly the elderly, because pneumonia may be a complication of the flu
• ]]>Pneumococcal vaccine]]> —recommended for:
  • People over aged 65, or those who have a chronic illness, such as ]]>diabetes]]> or ]]>sickle-cell disease]]>
  • Children under two years old

Other preventive measures include:

• Avoid smoking. Smoke weakens the lungs' resistance to infection.
• Avoid close contact with people who have the cold or flu.
• Wash hands often. This is very important when coming in contact with infected people.
• Protect yourself on jobs that affect the lungs.
• Eat a healthy diet.
• Get adequate rest.
• Exercise regularly.