Chemical pneumonitis is defined as...

• A. Infectious pneumonia caused by bacteria
• B. An inflammatory reaction in the lower airways caused by aspiration of gastric fluid
• C. A viral lung infection
• D. Allergic reaction causing wheeze

Answer: (B)

Chemical pneumonitis is an inflammatory injury to the lungs caused by aspiration of gastric contents. When acidic gastric fluid enters the lower airways, it burns the lung tissue and triggers an inflammatory response, which leads to swelling, increased vascular permeability, and impaired gas exchange.

This condition typically follows events where airway protection is compromised, such as vomiting or during anesthesia, and it presents with coughing and shortness of breath soon after aspiration. Fever can occur, but the underlying issue is chemical injury rather than infection. On imaging, you may see patchy infiltrates that can be bilateral, often basilar, rather than the focal consolidation more typical of bacterial pneumonia.

It’s distinct from infectious pneumonia caused by bacteria or viruses, which involve pathogens and different diagnostic and treatment implications. It’s also not an allergic reaction causing wheeze; that describes an airway constriction from allergens or irritants, such as in asthma or anaphylaxis, rather than chemical injury to the lung tissue from aspirated gastric contents.

Management is mainly supportive—oxygen as needed, bronchodilators if there is bronchospasm, careful airway management, and monitoring for complications. Antibiotics are not routinely used unless there is a superimposed infection suspected.