Diagnosis of Aspiration Pneumonia: What Is the Definition of Aspiration Pneumonia in Clinical Practices?

Aspiration is defined as the entry of oropharyngeal or gastric contents into the larynx and the lower respiratory tract. Aspiration is often the result of impaired swallowing, which allows oropharyngeal or gastric contents to enter the lungs, especially in patients who also have an ineffective cough reflex. Aspiration may involve the airways or lung parenchyma and 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. In these, aspiration pneumonia is an infectious disease caused by the inhalation of oropharyngeal secretions colonized by pathogenic bacteria, whereas aspiration pneumonitis is a chemical injury caused by inhalation of sterile gastric contents. Although there is some overlap between these syndromes, they are distinct clinical entities. In patients with aspiration pneumonia, unlike those with aspiration pneumonitis, the episode of aspiration is generally not witnessed. Thus, the diagnosis of aspiration pneumonia depends on clinical history, risk factors, and compatible findings on chest radiography. These radiographic findings include infiltrates in gravity-dependent pulmonary segments. Elderly persons frequently receive poor oral care, resulting in oropharyngeal colonization by potential respiratory tract pathogens, including Enterobacteriaceae, Pseudomonas aeruginosa, and Staphylococcus aureus. These pathogens are aspirated and may cause pneumonia.