Risk factors for aspiration include Impaired cognition or level of consciousness Impaired swallowing (such as occurs after some strokes or other neurologic diseases) Vomiting Gastrointestinal devices and procedures (eg, nasogastric tube placement) Dental procedures Respiratory devices and procedures (eg, endotracheal tube placement—see Ventilator-Associated Pneumonia) Gastroesophageal reflux disease Pathophysiology Chemical pneumonitis Multiple substances are directly toxic to the lungs or stimulate an inflammatory response when aspirated; gastric acid is the most common such aspirated substance, but others include petroleum products (particularly of low viscosity, such as petroleum jelly) and laxative oils (such as mineral, castor, and paraffin oil).