An Overview of Aspiration Pneumonia

The Accidental Infiltration of Food or Bacteria Into the Lungs

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Aspiration pneumonia is a type of pneumonia caused by the accidental infiltration of food or other substances from the mouth or stomach into the lungs. The condition can be caused by bacteria that normally reside in the mouth or nasal passages, or triggered by non-infectious toxins that damage lung tissue.

Chest X-rays and other tests can help differentiate aspiration pneumonia from other types of pneumonia. Bacterial infections are treated with antibiotics, while chemical pneumonia may require steroids and nonsteroidal drugs to bring down the inflammation.

Symptoms of aspiration pneumonia
Verywell / Emily Roberts

Symptoms

The symptoms of aspiration pneumonia are essentially the same as those of any other type of pneumonia, making it clinically difficult to differentiate. The same applies to the differences between aspiration pneumonia and chemical pneumonia, with a few notable differences.

The most common symptoms of aspiration pneumonia include:

  • chest pain
  • shortness of breath (dyspnea)
  • wheezing
  • fever
  • cough, sometimes with yellow or greenish sputum (mixture of saliva and mucus)
  • fatigue
  • difficulty swallowing (dysphagia)
  • profuse sweating
  • bad breath
  • a bluish skin color (cyanosis) caused by low blood oxygen levels

If the exposure was caused by a toxic substance, there may also be oral or nasal burns, a swollen tongue or throat, voice hoarseness, rapid heartbeat (tachycardia), an altered mental state, and other signs of poisoning.

Complications

Aspiration pneumonia can sometimes lead to severe and potentially life-threatening complications if left untreated, including:

  • parapneumonic effusion, which is the buildup of fluid in the lower lobe of the lung
  • empyema, the gathering of pus in the lung
  • lung abscess, a pus-filled cavity in the lungs
  • suprainfection, the rise of a secondary infection even after the first has been treated
  • bronchopleural fistula, an abnormal opening between the airways of a lung and the space around the lungs (pleural cavity)

If not treated aggressively and in a timely manner, complications of aspiration pneumonia can lead to respiratory failure and death.

Conditions like bronchopleural fistula alone carry anywhere from an 18 percent to 67 percent risk of death, according to research from the North Shore University Hospital in Long Island. It's important to seek medical help when necessary.

Causes

Aspiration pneumonia is characterized by a failure of the physiological mechanisms that prevent food and other substances from entering the trachea (windpipe) and lungs. The aspiration (drawing in) of these substances can cause inflammation, infection, or airway obstruction. Most episodes cause transient symptoms of pneumonitis (inflammation of the air sacs of the lung) without infection or obstruction.

A subtype of aspiration pneumonia, known as chemical pneumonia, involves the introduction of gastric acid or other non-infectious toxins into the lungs that directly damage airway tissues.

Healthy people will commonly aspirate small amounts of food and other substances into the lungs, but the body’s natural reflexes (gagging, coughing) will usually clear them without difficulty. Problems only occur if larger amounts are inhaled or the impairment of the lungs or nervous system weakens these pharyngeal reflexes.

Many cases of aspiration pneumonia are linked to either a neurological condition or an episode of impaired consciousness that disables this reflex.

Examples of conditions that would impair this reflex and potentially lead to aspiration pneumonia include:

  • neurological conditions like stroke, Parkinson’s disease, Alzheimer's disease, multiple sclerosis, cerebral palsy, amyotrophic lateral sclerosis (ALS), myasthenia gravis, and brain trauma injury for which dysphagia (difficulty swallowing) is characteristic
  • vomiting, during which the severe spasms can allow food to slip from the esophagus (feeding tube) into the trachea
  • alcohol, sedatives, or illegal drugs, which can alter your level of consciousness and disable the normal gag reflex
  • seizures, in which involuntary spasms can promote aspiration
  • general anesthesia, which also disables the swallowing reflex
  • dental procedures in which anesthesia and oral manipulation can enable aspiration
  • gastric tubes and endotracheal tubes, which provide a ready route of access from the stomach to the lungs
  • gastroesophageal reflux disease (GERD), characterized by acid reflux and the increased risk of chemical pneumonia
  • achalasia, an esophageal motility disorder
  • throat cancer
  • non-fatal drowning

With chemical pneumonia, gastric acid is the most common cause, although toxic gases (such as chlorine gas), fumes (like incinerator smoke and pesticides), airborne particles (like chemical fertilizer), and liquids can also infiltrate the trachea and cause lung inflammation.

Even certain laxative oils used to treat constipation (such as mineral oil or castor oil) are also known to cause chemical pneumonia if accidentally inhaled.

Risk Factors

Aspiration pneumonia is more common in elderly people due to conditions that alter consciousness (like sedatives) alongside with an increased risk of Alzheimer’s and other aging-related neurological disorders.

Aside from age, other risk factors include:

  • poor oral hygiene, promoting bacterial colonization in the mouth
  • a compromised immune system
  • prolonged hospitalization and/or mechanical respiration
  • damaged lung tissue due to smoking, COPD (chronic obstructive pulmonary disease), or other causes
  • prolonged or inappropriate use of antipsychotic drugs
  • prolonged use of proton pump inhibitors and ACE inhibitors
  • gastrointestinal motility disorders
  • radiation therapy to the head and neck
  • alcoholism or substance abuse
  • malnutrition
  • a hiatal hernia
  • diabetes

Diagnosis

Aspiration pneumonia is often suspected if symptoms develop soon after a precipitating event, such as severe vomiting, exposure to general anesthesia or industrial fumes, or a tonic-clonic seizure. Sometimes, the cause may be unknown which makes differentiating a diagnosis quite difficult.

Typical causes of pneumonia are influenza A, B, avian flu viruses, or the Streptococcus pneumoniae bacteria (found in most community-based pneumonia infections). If none of these can be found, aspiration pneumonia may be explored as a cause using a physical exam and a variety of imaging studies and lab tests.

Physical Exam

One of the first clues doctors look for when investigating aspiration pneumonia is the sudden appearance of fever and breathing problems after an aspiration event. They will also look for characteristic breath sounds on the stethoscope, such as crackling sounds (crepitus) on certain zones of the lungs. Foul-smelling breath is also common (and otherwise uncharacteristic of "regular" pneumonia).

Chronic aspiration, often caused by GERD (gastroesophageal reflux disease) or achalasia, may be evidenced by the appearance of a wet-sounding cough immediately after eating.

Imaging Studies

A chest X-ray can usually provide telling evidence of aspiration pneumonia. For example, if aspiration is suspected when a person was unconscious or in the throes of a seizure, there may be a consolidation of fluid to the back part of the upper lung.

If the aspiration occurred while standing or sitting, the consolidation would usually occur in both sides of the lower lobe.

When examing a chest X-ray, the doctor will look for white spots in the lungs (called infiltrates) that identify an infection.

With aspiration pneumonia, there will often be an area of density on the X-ray where the infiltrates are clustered around the area of obstruction. With "regular" pneumonia, the consolidation will be defined but appear more patchy in appearance.

A computed tomography (CT) scan with a contrast dye is more sensitive and typically ordered if a lung abscess, empyema, or bronchopleural fistula is suspected.

Lab Tests

While a physical exam and X-ray may provide all of the evidence needed to definitively diagnose aspiration pneumonia, lab tests may be ordered to support the diagnosis. This is especially true when trying to differentiate aspiration pneumonia and chemical pneumonia from other possible causes.

Generally speaking, blood tests will render similar results whether the condition is infectious or inflammatory. In both instances, the white blood cell count (WBC) will invariably be elevated, leading to leukocytosis.

A sputum culture may be ordered but is also problematic as contamination from other pathogens in the mouth (bacteria, viruses, and fungi) is common. While blood cultures are sometimes ordered, aspiration pneumonia is usually diagnosed and treated well before the results are returned.

A test called O2 saturation (SaO) will be performed to measure the amount of oxygen in your blood, primarily to assess how severe your pneumonia is. Less commonly, bronchoscopy (the insertion of a flexible scope into the trachea and airway passages) may be ordered if a particle is especially large or to obtain a lung tissue sample for analysis in the lab.

Differential Diagnoses

Pneumonia types can be difficult to distinguish because they are all so similar. Aspiration pneumonia is unique in that it can involve aerobic bacteria (including those associated with other pneumonia types), as well as anaerobic bacteria that naturally reside in the mouth, nose, and throat (but not the lungs).

Chemical pneumonia, by contrast, is characterized by the absence of infection (although the damage to the lungs can sometimes lead to secondary infection).

To differentiate the possible causes, doctors will look for defining features that characterize the different pneumonia types and explore other lung disorders with similar symptoms. These include:

  • community-acquired pneumonia, typically associated with Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus.
  • hospital-acquired pneumonia, typically associated with Staphylococcus aureus
  • pneumocystis pneumonia, differentiated by a diffuse "ground glass" appearance on X-ray, usually in people with severe immune suppression (such as advanced HIV)
  • pulmonary edema (excess fluid in the lungs), differentiated by symmetrical opacity on a chest X-ray and the absence of leukocytosis
  • atelectasis (a collapsed lung), differentiated by the absence of leukocytosis and other infection markers as well as the loss of lung volume on an X-ray

Treatment

Antibiotics are commonly used to treat aspiration pneumonia. Even if the cause is neurologic or chemical, a course of antibiotics will still be prescribed. This is because it is often difficult to exclude bacterial infection as a primary or contributing cause.

Broad-spectrum antibiotics that treat multiple bacterial strains are standardly used and may include clindamycin, moxifloxacin, unasyn (ampicillin/sulbactam), merrem (meropenem), and invanz (ertapenem).

The typical course can last anywhere from a week to two weeks.

If prescribed presumptively, the antibiotic may be stopped after three to four days if there are no signs of infiltrates on a chest X-ray. Regardless of the severity of your condition, you need to take your antibiotics as prescribed without missing a dose even if the symptoms disappear.

Missing doses or stopping treatment prematurely allows for the emergence of antibiotic-resistant strains. If this occurs, it will far more difficult to treat a bacterial infection in the future.

Supportive care measures may involve mechanical ventilation with supplemental oxygen to aid in respiration. If there is fluid in the lungs, a procedure called thoracentesis may be performed. This involves the insertion of a needle through the chest wall to drain accumulated fluid from the pleural space.

Prevention

If you are at risk of aspiration pneumonia, there are things you can do to reduce your risk. Useful prevention tips include avoiding sedating drugs and alcohol if you have chronic dysphagia and/or reflux. This is especially true before bedtime as aspiration commonly occurs while asleep. If you have chronic dysphagia and/or reflux, elevate your head by 30 degrees while sleeping to prevent the backflow of the stomach contents into the windpipe.

For people with chronic dysphagia, a dysphagia diet may be recommended. Depending on the severity, you may be advised to eat pureed foods that don't require chewing (level 1), soft, moist foods that require a little chewing (level 2), or soft, non-crunchy foods that require chewing (level 3).

Further useful preventative tips include:

  • working with a speech pathologist to strengthen the muscles and systems needed to swallow.
  • following your doctor's instructions about fasting to prevent aspiration during surgery or any medical procedure involving general anesthesia.
  • maintaining good oral hygiene to prevent the infiltration of the mouth bacteria into the trachea and lungs.
  • not smoking. Smoking damages your lungs' natural defenses against infections.

A Word From Verywell

If treated in an appropriate manner, aspiration pneumonia will usually respond well to medications and supportive care. While the risk of death with uncomplicated aspiration pneumonia is around 5 percent, that risk can increase significantly if the treatment is delayed.

See a doctor immediately if you develop sudden wheezing, shortness of breath, chest pains, fever, coughing, or difficulty swallowing. The absence of nasal symptoms should tell you that is not the flu you are dealing with but a potentially serious respiratory infection.

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