Wet Vocal Quality? Or is your ear playing tricks on you?
Picture this: You are at the bedside of a charming 85-year-old who just survived a minor stroke. You’re performing a clinical swallow evaluation, and everything seems to be going well until he takes a sip of water. He doesn't cough, his eyes don't water, and his breathing is normal. But then, with a seemingly wet vocal quality, he says, "That tasted great!" and your heart sinks.
It’s that gurgly phonation that pops up as one of the signs of aspiration in so much literature. Sirens start going off inside your head along with your own voice screaming, "He’s aspirating!" You immediately recommend a strict diet modification and NPO for thin liquids, feeling like a hero who just saved a patient from pneumonia. Job well done and onto the next one, right?
What if I told you that your clinical ear was as reliable as a weather forecast in a hurricane?
But don’t take it from me. Let’s see what the research says…
Putting Our Ears to the Test
A fascinating study by Groves-Wright and colleagues investigated whether we can trust the wet vocal quality we hear at the bedside. They wanted to determine how good SLPs are at detecting the presence of material in the larynx (AKA the waiting room for the lungs).
What did they do?
They enrolled 78 subjects and performed videofluoroscopic swallow studies (VFSS). While videofluoroscopy was in progress, they recorded the patients' voices immediately after swallowing.
Then, they played these audio clips for experienced dysphagia clinicians (without showing them the radiographic images). These SLPs had to listen and decide: "Does this voice sound wet or clear?" Finally, the researchers compared those ear-witness accounts (sorry, couldn’t help myself) to the actual footage to see if the SLPs were right. So, were they?
Before I give you the answer, I want you to think of your larynx as a musical instrument. Think of a delicate flute, for example. To get a clear note, the air has to flow perfectly through the tube, right? There’s an important difference, though: Flutes are usually built in a factory in bulk, where identical pieces are put together in identical ways. The larynx wasn’t made in a factory. God made them. And God tends to be… less predictable than industrialists, who have less imagination and creativity. In other words, the larynx produces lots of different sounds in lots of different ways, and the human ear is not great at identifying each sound and pinpointing what’s happening behind the scenes.
The Findings
So what happened in our study? Three main takeaways here:
Clinicians were not reliable: Even experienced SLPs couldn't consistently agree on what "wet" actually sounded like. One SLP’s confirmed "gurgle" was another’s "perfectly clear".
Material ≠ Wet Voice: Just because there was liquid sitting in the larynx on the x-ray didn't mean the voice sounded wet. Sometimes there was laryngeal penetration, and the voice sounded great. Other times it didn’t.
Wet Voice ≠ Material: And the opposite was true. Sometimes there was nothing in the larynx, and the voice sounded wet. Other times it didn’t. A mixed bag to say the least.
Essentially, material in the larynx can result in multiple different voice qualities, and our ears aren't sharp enough to tell the difference.
Don’t Buy It?
I didn’t buy these results at first either. But the results are “sound.” The audio samples were completely randomized, and the authors used a rigorous method by time-linking the audio directly to the x-ray, which is the best way to prove what’s actually happening in the throat while someone speaks.
However, keep in mind that this was done in a controlled environment– the SLPs only had access to the audio. No other contextual cues. While this is valuable for research, it doesn’t tell us what other clues the experienced clinician might use to fill in the gaps. If we keep in mind the patient’s medical history, complaints, or other signs of aspiration, we may be more accurate. But the core message remains: A "wet voice" alone is a flimsy foundation for a clinical recommendation.
Conclusion: Back to Mr. Miller
So, what happened to Mr. Miller?
If you had relied solely on your ears, you would have restricted his diet based on a sound that—statistically speaking—might not have meant anything at all on its own.
You, being the great SLP you are, remembered this study. You realized that wet vocal quality is an unreliable measure, and there were no other signs or symptoms of dysphagia. So, you didn't panic. You recommended an instrumental study to see what was actually happening.
The result? The VFSS showed that Mr. Miller had some mild residue concentrated in the valleculae, but his airway remained completely clear. The wet vocal quality was just a false alarm.
When in doubt, check it out and refer for an instrumental swallow study. By fighting fear with facts, you can save your patients from unnecessary restrictions and send them on a path to safe discharge home.
Reference: Groves-Wright KJ, Boyce S, Kelchner L. Perception of wet vocal quality in identifying penetration/aspiration during swallowing. J Speech Lang Hear Res. 2010 Jun;53(3):620-32. doi: 10.1044/1092-4388(2009/08-0246). Epub 2009 Dec 22. PMID: 20029051.
