aspiration pneumonia

Normally, swallowing and a brisk cough keep food, drink and saliva out of the airway, sending them down the food pipe instead. Aspiration pneumonia happens when those defenses fail and material from the mouth or stomach goes down the wrong way into the lungs, carrying germs with it and seeding an infection in the lung tissue.

It is a lung infection caused by inhaling oral secretions or gastric contents into the lower airways. People most at risk are those with impaired swallowing or reduced consciousness — after a stroke, with dementia, during heavy sedation or intoxication, or with conditions affecting the throat muscles. The aspirated material often carries mouth bacteria, including anaerobes, and tends to affect the parts of the lung that are lowest when the person aspirated, commonly the lower lobes or the back of the lung.

Treatment is with antibiotics chosen to cover the likely mixed mouth flora, alongside measures to address the underlying swallowing problem — such as a speech-and-swallow assessment and adjusting how food and fluids are given. If the infection is severe or progresses, it can develop into a lung abscess or empyema.

A useful distinction: simply inhaling sterile stomach acid causes a chemical inflammation of the lung that may improve without antibiotics, whereas inhaling germ-laden material causes true infective pneumonia — telling them apart guides whether antibiotics are truly needed.