Review of Aspiration Pneumonia
In veterinary medicine, aspiration pneumonia is often suspected in animals diagnosed with
pneumonia following periods of vomiting or regurgitation or in elderly/immunocompromised patients. This excellent article reviews aspiration pneumonia in man as a model for the disease in our pateints.
Aspiration pneumonia is best considered not as a distinct entity but as part of a continuum that also includes community- and hospital acquired pneumonias. It is estimated that aspiration
pneumonia accounts for 5 to 15% of cases of community-acquired pneumonia, but figures for hospital acquired pneumonia are unavailable. Robust diagnostic criteria for aspiration pneumonia are lacking, and as a result, studies of this disorder include heterogeneous patient populations.
Aspiration of small amounts of oropharyngeal secretions is normal in healthy persons during sleep, yet microaspiration is also the major pathogenetic mechanism of most pneumonias. Large-volume aspiration (macroaspiration) of colonized oropharyngeal or upper gastrointestinal contents is the sine qua non of
aspiration pneumonia. Variables affecting patient presentation and disease management include bacterial virulence, the risk of repeated events, and the site of acquisition (nursing home, hospital, or community). According to this spectrum, patients labeled as having aspiration pneumonia usually represent a clinical phenotype with risk factors for macroaspiration and involvement of characteristic anatomical pulmonary locations. Aspiration syndromes may involve the airways or pulmonary parenchyma, resulting in a variety of clinical presentations.
This review focuses on aspiration involving the lung parenchyma, primarily aspiration pneumonia and chemical pneumonitis. Aspiration of noninfectious material such as blood or a foreign body is also important. Aspiration pneumonia is an infection caused by specific microorganisms, whereas chemical pneumonitis is an inflammatory reaction to irritative gastric contents. Our understanding of the interaction between bacteria and the lung has improved. They examine this improvement, along with changing concepts of the microbiology and pathogenesis of aspiration pneumonia. They also examine the clinical features, diagnosis, treatment, and prevention of both aspiration pneumonia and chemical pneumonitis, as well as the risk factors.