Aspiration pneumonia is diagnosed based on clinical signs or symptoms of pneumonia in a person with a history of, or risk factors for, aspiration.
Chest x-ray will show a new infiltrate; infection usually involves the dependent lung lobe. Sputum culture and Gram stain are usually inconclusive but may identify the infecting organism.
Complications of disease include lung abscess and empyema.
Aspiration pneumonia results from inhalation of oropharyngeal contents into the lower airways that leads to a chemical pneumonitis, lung injury, and resultant bacterial infection. It commonly occurs in patients with risk factors such as impaired conscious level, swallowing dysfunction, and gastrointestinal disease.
The bacteriology and presentation of aspiration pneumonia have changed over the past five decades. Older studies characterised an anaerobic pleuropulmonary syndrome, with necrotising pneumonia, putrid sputum, and abscess formation as a result of the presence of anaerobic bacteria. More recent literature suggests that aspiration pneumonia resulting from anaerobic bacteria is less common than previously thought, and often is not distinct from pneumonia caused by aerobic bacteria. There is debate on whether aspiration pneumonia represents a distinct entity from typical pneumonia, or whether it is one end of the spectrum of pneumonia syndromes. There is also debate on whether aspiration pneumonia is not associated with infection in some patients and instead may represent a chemical pneumonitis.
Typical pneumonia can also occur from microaspiration of oronasopharyngeal contents, and can present with similar microbiology and clinical course as aspiration pneumonia, as well as needing similar treatment.
History and exam
Key diagnostic factors
- presence of risk factors
Other diagnostic factors
- history of vomiting
- foul-smelling breath
- frothy or purulent sputum
- pleuritic chest pain
- reduced appetite
- reduced mobility
- general debilitation
- swallowing dysfunction
- impaired conscious level
- gastrointestinal disease
- general anaesthetic or oropharyngeal procedures
- older age
- poor cough
- presence of a feeding tube
- head and neck cancers
- recumbent position during enteral feeding
- poor oral hygiene
1st investigations to order
- chest x-ray
- full blood count
- sputum Gram stain
- sputum culture
Investigations to consider
- arterial blood gas
Jonathan Bennett, MD
Honorary Professor of Respiratory Sciences
University of Leicester
JB is Chair of the British Thoracic Society (BTS). He is also deputy medical director RCP Invited service Reviews, and speaker at National Society (eg., BTS), Primary Care respiratory Society, Society Cardiothoracic Surgeons meetings.
JB declares that he has no competing interests.
Claire Vella, MD, MRCP
Clinical Fellow Lung Cancer and Interventional Pulmonology
CV declares that she has no competing interests.
BMJ Best Practice would like to gratefully acknowledge the previous expert contributor, whose work has been retained in parts of the content:
Michael J. Lanspa, MD
Adjunct Associate Professor
Division of Pulmonary and Critical Care Medicine
Intermountain Medical Center
University of Utah
Salt Lake City
David G. Smithard, BSc, MB, MD, FRCP, FRCSLT (Hon)
University of Greenwich
Consultant in Elderly Medicine
Queen Elizabeth Hospital
Lewisham and Greenwich NHS Trust
DGS declares that he has no competing interests.
Section Editor, BMJ Best Practice
AS declares that she has no competing interests.
Lead Section Editor, BMJ Best Practice
RW declares that she has no competing interests.
Drug Editor, BMJ Best Practice
AM declares that he has no competing interests.
Comorbidities Editor, BMJ Best Practice
JC declares that she has no competing interests.
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