The entry of foreign material, such as saliva, ingested liquid or food, or gastric contents refluxed up to the level of the throat, into the airway below the vocal cords. If this foreign material only enters the laryngeal vestibule but does not descend below the vocal cords, this is not considered aspiration, but instead laryngeal penetration. Significant or recurring aspiration puts a person at risk of pneumonia; laryngeal penetration alone does not, though a person with laryngeal penetration is more likely to aspirate trace amounts than is the person with completely normal swallowing function.
Aspiration can occur before, during, or after the act of swallowing. Aspiration before the swallow means that liquid or food in the mouth dribbles or spills down into the larynx and beyond before the swallow is initiated. This is seen most commonly when there is a neurological disorder, such as after a cerebrovascular accident (stroke).
Aspiration during swallowing happens when, as the swallowed material travels from the base of the tongue toward the entrance to the esophagus (in the pharyngeal phase of swallowing), some of that material drops into the larynx and straight down through it to enter the airway. This kind of aspiration can happen because a person’s vocal cords don’t close properly, due to paralysis, paresis, or tissue loss such as after a partial laryngectomy.
Aspiration after swallowing happens when some of the ingested liquid or solid remains pooled in the lower throat after the swallow is complete, and when the patient takes the first post-swallow breath, it enters the airway. To try to prevent aspiration after swallowing, the supraglottic swallow technique can help.
Aspiration (1 of 7)
Panoramic laryngopharynx view. The patient is holding a sip of liquid in his mouth and preparing to swallow it.
Aspiration (2 of 7)
Before he initiates the swallow, a small drip of liquid "escapes" and drips downward into the pharynx. The patient does not yet suspect this. There are only a few drops of liquid, even though it looks like a larger amount due to the close-up view.
Aspiration (3 of 7)
A few milliseconds later yet, the tiny drip has fallen halfway down the length of the pharynx. One can see that the patient is not aware of this drip, as he has not fully closed the vocal cords.
Aspiration (4 of 7)
A few milliseconds later, the drop is arriving at the left (right of image) pyriform sinus. The patient is still not aware of this swallowing "mistake". The vocal cords remain open, so if this liquid had dripped instead into the laryngeal opening, it would have entered the airway and made him cough.
Aspiration (5 of 7)
With a second sip of faintly blue-stained water, a small trickle escapes "early" before the swallow. One can see the leading edge of water flowing onto the epiglottis (indicated by the dotted line).
Aspiration (6 of 7)
The leading edge of the water has advanced and continues to flow downwards. This is indicated by the dotted line and arrows.