One discussion this week involved the risk factors for aspiration in community-acquired pneumonia (CAP).

References: Komiya K, et al. Prognostic implications of aspiration pneumonia in patients with community acquired pneumonia: A systematic review with meta analysis. Scientific Reports. 2016 Dec7;6:38097. doi: 10.1038/srep38097

Taylor JK et al. Risk factors for aspiration in community-acquired pneumonia: analysis of a hospitalized UK cohort. American Journal of Medicine. 2013 Nov;126(11):995-1001. doi:10.1016/j.amjmed.2013.07.012.

Summary: Aspiration pneumonia can be defined as pneumonia in patients who have aspiration risk. Komiya et al (2016) list the following as risk factors for aspiration:

• impaired consciousness
• chronic neurological disease
• weakness
• swallowing difficulties
• esophageal dysfunction or mechanical obstruction
• aspiration witnessed during eating or vomiting
• sedation

Overt aspiration is generally not witnessed, and aspiration alone cannot fully explain the development of pneumonia. Most healthy subjects passively aspirate oropharyngeal secretions during night, but their cough reflex, mucociliary clearance, and immune system usually prevents the development of pneumonia (Komiya et al, 2016).

In their observational study of 1348 patients with CAP, Taylor et al (2013), while also listing the factors above, noted these additional risk factors:

• older (above 60-84, median of 74 years)
• comorbidities of chronic liver disease, congestive heart failure, and stroke

Komiya et al’s (2016) systematic review findings suggest that aspiration risk is associated with greater in-hospital and 30-day mortality in subjects with CAP except, perhaps, in the ICU setting. Although there are insufficient data to perform a meta-analysis on long-term mortality, recurrent pneumonia, and hospital readmission, the few reported studies suggest that aspiration pneumonia is also associated with these outcomes.