Pulmonary aspiration is the entry of solid or liquid material such as pharyngeal secretions, food, drink, or stomach contents from the oropharynx or gastrointestinal tract, into the trachea and lungs. When pulmonary aspiration occurs during eating and drinking, the aspirated material is often colloquially referred to as "going down the wrong pipe". Consequences of pulmonary aspiration include no injury at all, chemical pneumonitis, pneumonia, or even death from asphyxiation. These consequences depend on the volume, chemical composition, particle size, and presence of infectious agents in the aspirated material, and on the underlying health status of the person. In healthy people, aspiration of small quantities of material is common and rarely results in disease or injury. People with significant underlying disease or injury are at greater risk for developing respiratory complications following pulmonary aspiration, especially hospitalized patients, because of certain factors such as depressed level of consciousness and impaired airway defenses (gag reflex and respiratory tract antimicrobial defense system). About 3.6 million cases of pulmonary aspiration or foreign body in the airway occurred in 2013.
Causes
Neurologic impairment Any condition that results in depressed level of consciousness (such as traumatic brain injury, alcohol intoxication, drug overdose, medical sedation, stroke, and general anesthesia) can result in pulmonary aspiration of pharyngeal secretions. Neurologic conditions that affect muscle coordination and posture (such as cerebral palsy, Parkinson's disease, muscular dystrophies, etc.) can also increase risk of aspiration.
Respiratory disease Respiratory diseases often result in an impaired ability to clear the airways of secretions, and present an increased risk of pulmonary aspiration. This includes those with a respiratory disease resulting in a weak cough, or poor forced expiratory volume. Any condition requiring mechanical ventilation is also at risk for aspiration.
Oropharyngeal disorders Conditions which disrupt coordination of swallowing above the glottis put a patient at increased risk for aspiration. This is referred to as oropharyngeal dysphagia and can be a result of structural abnormalities (strictures, stenosis, mediastinal and neck masses, etc.), connective tissue diseases, neuropathy, or other central nervous system-related disorders (stroke, head injury, ALS, Guillain–Barré syndrome, etc.).
Medications Drugs can increase a person's risk of aspiration through multiple mechanisms. Medications including sedatives, hypnotics, and antipsychotics can result in decreased level of consciousness and loss of cough and swallow reflexes. Long-term use of proton pump inhibitors can lead to overgrowth of gastric bacteria and increase risk of aspiration. Antihistamines and antidepressants can cause xerostomia (decreased oral secretions) which can also lead to aspiration.
Foreign-body aspiration Particularly common in children, foreign-body aspiration occurs when an object is inhaled from the mouth into the airway. Objects commonly include food, coins, toys and balloons. Age and developmental delays are therefore also considered risk factors for aspiration. The lumen of the right main bronchus is more vertical and slightly wider than that of the left, so aspirated objects are more likely to end up in this bronchus or one of its subsequent bifurcations.
Presentation Uncomplicated aspiration events commonly present with symptoms including wheezing and coughing. Signs and symptoms that aspiration is complicated can include dyspnea (shortness of breath), hypoxemia (low oxygen in the blood), tachycardia (high heart rate), fever, and crackles or wheezes on lung exam.
Evaluation Evaluation and diagnosis of aspiration and aspiration-related complications may include imaging or laboratory studies.
Imaging Radiologic studies may be done to image the chest wall, lungs, and airway to evaluate and diagnose conditions that may be contributing to aspiration, and also to diagnose complications of previous aspiration. Chest X-rays can be useful in the diagnosis of aspiration pneumonia but may be negative early in the course. Chest CT Scan can identify the presence of a pneumonia as well, and can also assist in characterizing abscesses, foreign objects, or pleural disease.
A fluoroscopic swallow study can be done in cases where dysphagia or motility disorders are thought to be the source of aspiration. Food and drink are mixed with barium contrast and monitored using x-ray to evaluate swallowing. Aspiration can be diagnosed if contrast is seen coursing below the vocal cords into the trachea.
Laboratory studies Microbiologic studies may be obtained in the case of suspected aspiration-related pulmonary infection. Labs may include infectious cultures of patient blood, sputum, or pleural fluid depending on the patient case and clinical judgement of the treatment team.
Complications
Aspiration pneumonia Aspiration pneumonia is when bacteria is carried into the respiratory tract via aspiration and subsequently causes an infection of the lung. Any substance or object that is aspirated into the airway has the potential of carrying infectious agents with it into the respiratory tract. It primarily affects older adults and can be especially severe in patients with learning disabilities, or disorders of abnormal swallowing.
Aspiration pneumonitis Aspiration pneumonitis (Mendelson's syndrome) is chemical injury of lung tissue secondary to aspiration of regurgitated gastric acid. The syndrome was first described among pregnant patients after the administration of anesthesia, though it can occur in any scenario where gastric contents are aspirated.
Death
Aspiration can result in patient death through a variety of mechanisms. It is important to recognize and diagnose early in order to improve patient outcomes. Death from aspiration and aspiration-related syndromes is most common in elderly patients with known baseline risk factors, though it frequently goes unrecognized.
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