Aspiration pneumonia is lung infection caused by inhaling mouth secretions, stomach contents, or both. Chemical pneumonitis is lung irritation caused by inhalation of substances toxic to the lungs.
Tiny particles from the mouth frequently dribble or are inhaled (aspirated) into the airways. Usually they are cleared out by normal defense mechanisms (such as coughing) before they can get into the lungs and cause inflammation or infection. When such particles are not cleared (because of impaired defense mechanisms or because the volume of aspirated material is so large), they can cause aspiration pneumonia. Older people and people who are debilitated, have trouble swallowing (as may happen from a stroke), are intoxicated by alcohol or drugs, or are unconscious from anesthesia or a medical condition are especially at risk for this type of pneumonia.
Symptoms of pneumonia do not begin for at least a day or two. The sputum may smell foul. Treatment requires antibiotics. Many antibiotics, including clindamycin, amoxicillin plus clavulanate, ampicillin, and imipenem, can be used. If a solid particle was inhaled, bronchoscopy may be needed to remove it (see Diagnosis of Lung Disorders: Bronchoscopy).
Chemical pneumonitis occurs when a person inhales (aspirates) material that is toxic to the lungs. The problem is more the result of irritation than infection. A commonly inhaled toxic material is stomach acid, so that chemical pneumonitis may result whenever a person inhales what has been vomited up. Inhalation of vomit can occur when a person who vomits is not completely awake, as can happen after a seizure, stroke, or drug or alcohol overdose. Chemical pneumonitis may also be caused by inhalation of laxative oils (such as mineral, castor, and paraffin oils) and hydrocarbons (such as gasoline, kerosene, and petroleum products). Sudden shortness of breath and a cough develop within minutes or hours. Other symptoms may include fever and pink frothy sputum. In less severe cases, the symptoms of aspiration pneumonia may occur a day or two after inhalation of the toxin.
The diagnosis of chemical pneumonitis is usually obvious from the sequence of events if this information is available. Chest x-rays and measurements of oxygen concentrations in arterial blood may help. When the diagnosis remains unclear, bronchoscopy is sometimes done.
Treatment consists of oxygen therapy (see Rehabilitation for Lung and Airway Disorders: Oxygen Therapy) and mechanical ventilation (see Respiratory Failure and Acute Respiratory Distress Syndrome: Acute Respiratory Distress Syndrome (ARDS)) if necessary. The windpipe (trachea) may be suctioned to clear secretions and aspirated food particles out of the airways. Bronchoscopy may also be used for this purpose.
Antibiotics are usually given because doctors cannot easily distinguish this form of aspiration pneumonia from a bacterial infection. Up to 30 to 50% of people with serious chemical pneumonitis due to inhaled stomach acid die.
Last full review/revision April 2008 by John G. Bartlett, MD