Primary care.

SPIRATION is defined as the inhalation of oropharyngeal or gastric contents into the larynx and lower respiratory tract. 1,2 Several pulmonary syndromes may occur after aspiration, depending on the amount and nature of the aspirated material, the frequency of aspiration, and the host's response to the aspirated material. 2 Aspiration pneu-monitis (Mendelson's syndrome) is a chemical injury caused by the inhalation of sterile gastric contents, whereas aspiration pneumonia is an infectious process caused by the inhalation of oropharyngeal secretions that are colonized by pathogenic bacteria. Although there is some overlap between these syndromes, they are distinct clinical entities (Table 1). Other aspiration syndromes include airway obstruction, lung abscess, exogenous lipoid pneumonia, chronic interstitial fi-brosis, and Mycobacterium fortuitum pneumonia. 1,2 This article focuses on the pathophysiology, clinical features, and management of aspiration pneumonia and aspiration pneumonitis. Pulmonary aspiration is an important cause of serious illness and death among residents of nursing homes as well as hospitalized patients. 1-4 However, the major pulmonary-aspiration syndromes are frequently misdiagnosed and poorly treated. Four common problems are the failure to distinguish aspiration pneu-monitis from aspiration pneumonia, the tendency to consider all pulmonary complications of aspiration to be infectious, the failure to recognize the spectrum of pathogens in patients with infectious complications, and the misconception that aspiration must be witnessed for it to be diagnosed. EPIDEMIOLOGY The lack of specific and sensitive markers of aspiration complicates the epidemiologic study of aspiration syndromes. Furthermore, most studies do not distinguish between aspiration pneumonitis and aspiration pneumonia. Nevertheless, several studies indicate that 5 to 15 percent of cases of community-acquired pneumonia are aspiration pneumonia. 5-7 Aspiration pneumonia is the most common cause of death in patients with dysphagia due to neurologic disorders, a condition that affects approximately A 300,000 to 600,000 people each year in the United States. 8-10 Aspiration pneumonia is also common among residents of nursing homes. In one study of patients with nursing home–acquired pneumonia and controls with community-acquired pneumonia, the incidence of aspiration pneumonia was 18 percent and 5 percent, respectively. 4 Aspiration pneumonitis occurs in approximately 10 percent of patients who are hospitalized after a drug overdose. 11,12 It is also a recognized complication of general anesthesia, occurring in approximately 1 of 3000 operations in which anesthesia is administered and accounting for 10 to 30 percent of all deaths associated with anesthesia. 13,14 ASPIRATION PNEUMONITIS Aspiration pneumonitis is defined as acute lung injury after …