pulmonary disorders
Aspiration Pneumonitis and Pneumonia
Pathophysiology
Multiple substances are directly toxic to the lungs or stimulate an inflammatory response when aspirated; gastric acid is the most common such aspirated substance, but others include petroleum products (particularly of low viscosity, such as petroleum jelly) and laxative oils (such as mineral, castor, and paraffin oil). Petroleum products and laxative oils can cause lipoid pneumonia. Aspirated gasoline and kerosene also cause a chemical pneumonitis (see Hydrocarbon Poisoning ). as in treatment of overdose) are injurious in quantity. Gastric acid causes a chemical burn of the airways and lungs, leading to rapid bronchoconstriction, Atelectasis , and edema. This syndrome may resolve spontaneously, usually within a few days, or may progress to Healthy people commonly aspirate small amounts of oral secretions, but normal defense mechanisms usually clear the inoculum without sequelae. Aspiration of larger amounts, or aspiration in a patient with impaired pulmonary defenses, often causes pneumonia and/or a Lung Abscess . Older patients tend to aspirate because of conditions associated with aging that alter consciousness (eg, sedative use) and other disorders (eg, neurologic disorders, swallowing disorders). Empyema (see Gram-negative enteric pathogens and oral anaerobes are the most frequent pathogens in aspiration pneumonia. 