What you need to know about silent aspiration in children

Calling all feeding therapists: for those of you who are newer to feeding therapy, or maybe primarily work in the picky eating realm (or are a curious parent!) we wanted to take some time to explain what silent aspiration is, how we can diagnose it, and what we can do about it.

Actually, let’s just start with defining aspiration

Let‘s start with the basics: when food or liquid enters the lungs, this is called “tracheal aspiration.” This can occur in a few different ways. (1) The food or liquid can enter the airway and eventually lungs from “above” the airway which means the food or liquid sneaks into the airway as it travels down from the mouth to the pharynx and towards the esophagus, due to disordered swallowing. One or more of the body’s protective mechanisms that usually close the airway during a swallow didn’t work appropriately, and the airway was not protected during swallowing. (2) The food or liquid can enter the airway/lungs from “below” which means the food or liquid is moving from the stomach back towards the mouth and along the way spills into the airway, such as when someone has “acid reflux” or during vomiting—meaning the food/liquid was swallowed appropriately, but came back up and then entered the lungs. (3) The food or liquid enters the breathing tube (larynx/trachea) via an anatomical abnormality that connects the food tube (pharynx/esophagus) with the breathing tube. Similar to #2, the food or liquid is usually swallowed appropriately but then the anatomical issue allows the food or liquid to sneak into the airway.

The literature shows that we all aspirate sometimes (remember when you drank something too fast and coughed, choked, and had to catch your breathe?); even healthy adults aspirate saliva during deep sleep 💤! Our body and lungs are pretty strong and resilient, and kill any bacteria that might sneak into the respiratory tract, but frequent aspiration does a number on the lungs, and can lead to infections, lung damage/disease, and pneumonia.

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Silent aspiration- what does that mean

So what do we mean when we say “silent aspiration”? When a swallowing therapist evaluates a patient, they look for overt signs and symptoms of swallowing dysfunction. These red flags include coughing, watery eyes, congestion during feeding, sputtering, changes in breathing patterns, and color changes. But sometimes, swallow dysfunction occurs WITHOUT any of these overt signs, and the therapist has to make an inference that something is going wrong OR the aspiration is seen on a test, such as a Modified Barium Swallow Study (MBSS) but the patient didn’t show any overt or outward signs during the clinical feeding evaluation or during the MBSS.

If aspiration occurs without overt, observable symptoms, this is called “silent” aspiration.

There are many research articles that look at different elements of silent aspiration but there are actually relatively few that define it and clarify which signs are considered “overt” vs “subtle.“ There are a few that do describe and define silent aspiration as we define it above but based on those it isn’t clear if certain signs (such as a desaturation registered on a cardiopulmonary monitor) would qualify as overt signs of aspiration or if a patient who aspirated and didn’t cough or show any other outward signs but whose heart rate spiked or who had a light stridor would still be considered to have “silent aspiration” if aspiration was confirmed, despite the presence of those subtle but observable signs.

Prevalence & risk factors

When it comes to the prevalence of silent aspiration there are different numbers depending on what study you read but there was a 2018 study by Velayutham et al which found that out of almost 1,300 children under 18 referred for MBSS (due to feeding difficulties) 34% aspirated and out of those patients who aspirated, 89% aspirated silently. A 2011 study by Weir et al which reviewed data on 300 children who were seen for MBSS found that 34% (oddly same as the other study) aspirated and out of those who aspirated, 81% aspirated silently.

The 2011 study by Weir et al found that those most likely to aspirate silently we’re children with neurologic impairment, Cerebral Palsy, lung disease, or those who receive tube feeds.