A typical case is aspiration of stomach contents. When stomach contents get into the lungs, the patient can actually drown due to the volume of gastic material, or, with less material, suffer damage to the lung tissue due to the acid content of the stomach. The latter can lead to life-threatening aspiration pneumonia.
The lungs are normally protected against aspiration by so-called protective reflexes such as coughing and swallowing. Significant aspiration can only occur if the protective reflexes are absent (in neurological disease, coma, or general anesthesia). Measures to prevent aspiration depend on the situation and the individual patient, with endotracheal intubation often being necessary.