Hospital-acquired pneumonia is an infection of the lungs contracted during a hospital stay.

Pneumonia is a very common illness. It is caused by many different germs and can range in seriousness from mild to life-threatening.

Hospital-acquired pneumonia tends to be more serious, because a patient's defense mechanisms against infection are often impaired during a hospital stay. In addition, the types of germs present in a hospital are often more dangerous than those encountered in the community.

Hospital-acquired pneumonia occurs more often in patients who require a respirator (also called a breathing machine or ventilator) to help them breathe. When pneumonia occurs in a patient who is on a ventilator, it is known as ventilator-associated pneumonia.

Risk factors for hospital-acquired pneumonia include:

• Alcoholism
• Being on a breathing machine
• Breathing material into the lungs (aspiration)
• Chest surgery
• Immunosuppression from medications or disease
• Long-term (chronic) lung disease
• Medications that affect alertness
• Older age
• Recent illness

• Cough that may produce mucus-like, greenish, or pus-like phlegm (sputum)
• Chills
• Easy fatigue
• Excessive sweating (rare)
• Fever
• General discomfort, uneasiness, or ill feeling (malaise)
• Headache
• Joint stiffness and pain (rare)
• Loss of appetite
• Muscle stiffness (rare)
• Nausea and vomiting
• Sharp or stabbing chest pain that gets worse with deep breathing or coughing
• Shortness of breath

A physical examination shows:

• Respiratory distress
• Crackles or decreased breath sounds when listening to the chest with a stethoscope

Tests performed may include:

• Arterial blood gases
• Blood cultures
• Chest x-ray or CT scan
• Complete blood count (CBC)
• Sputum culture
• Sputum gram stain

Treatment aims to cure the infection with antibiotics. An antibiotic is chosen based on the specific germ found by sputum culture.

However, the bacteria cannot always be identified with tests. Antibiotic therapy is given to fight the most common bacteria that infect hospitalized patients -- Staphylococcus aureus and gram-negative bacteria.

Supportive treatment includes:

• Oxygen
• Lung treatments to loosen and remove thick mucus from the lungs

Most patients respond to treatment and improve within 2 weeks. However, hospital-acquired pneumonia can be very severe and sometimes life-threatening.

Elderly or very weak patients who do not respond to treatment may die from acute respiratory failure caused by the pneumonia.

Ongoing prevention programs to limit hospital-acquired infections are in place at most institutions.

American Thoracic Society. Guidelines for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia. Am J Respir Crit Care Med. 2005 Feb 15;171(4):388-416.

Limper AH. Overview of pneumonia. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 97.