Face, Mouth, and Neck Diagnoses

Pneumonia is an inflammatory condition of the interstitial lung tissue in which fluid and blood cells escape into the alveoli. More than 3 million people in the United States are diagnosed each year with pneumonia. The disease process begins with an infection in the alveolar spaces. As the organism multiplies, the alveolar spaces fill with fluid, white blood cells, and cellular debris from phagocytosis of the infectious agent. The infection spreads from the alveolus and can involve the distal airways (bronchopneumonia), part of a lobe (lobular pneumonia), or an entire lung (lobar pneumonia).

The inflammatory process causes the lung tissue to stiffen, thus resulting in a decrease in lung compliance and an increase in the work of breathing. The fluid-filled alveoli cause a physiological shunt, and venous blood passes unventilated portions of lung tissue and returns to the left atrium unoxygenated. As the arterial oxygen tension falls, the patient begins to exhibit the signs and symptoms of hypoxemia. In addition to hypoxemia, pneumonia can lead to respiratory failure and septic shock. Infection may spread via the bloodstream and cause endocarditis, pericarditis, meningitis, or bacteremia.

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