I remember learning about all the signs way back when in class and then carrying this with me early on as a young, black&white-thinking #newbie SLP years ago:
Tearing eyes= silent aspiration🤦♀️
Cough = thicken liquids until no cough🤦♀️🤦♀️
Wet voice = aspiration😳 (I’m pretty sure my jam-packed brain full of all the info from school probably pushed aside even thinking about penetration..)
Even after all these years, I still find myself having to push these naive thoughts aside from time to time in order to make way for more critical and higher-level thinking and reasoning, versus just relying on a sole factor😉. While there’s been a lot learned along the way from those first few “first-days”, when it comes to that wet-gurgly, “underwater” sound that we might often find ourselves unconsciously listening to from across the dining room or even a restaurant, I gotta know more!
I’ll be 100% honest in that when initially starting to find out more to write about this topic, before stumbling on the second article, I began only with a great article from Waito et al (2011). This article builds off previous research and learned mistakes (aka limitations) and not only uses auditory-perceptual measures (aka what we think we’re hearing) via GRBAS, but also compares these to voice-acoustic measures (your jitter🕺, your shimmer💃, signal-to-noise-ratio🗣, etc.) from recorded “ha-ha-ha” vocal phrases pre- and post-swallow!
In case you’re like me and still slowly working on building up your voice repertoire (knowledge-wise, not singing😅🎤), they also give you a brief rundown for some of these too:
“When an abnormality in the G (grade) score of the GRBAS scale was identified, this was further qualified by rating the most salient feature(s) of the perceived dysphonia on the RBAS subscales (Roughness, Breathiness, Asthenia, and Strain). Asthenia is a term used to capture the perceptual quality of voice weakness.” p.4 (Waito et al. (2011)
They then compare all of these vocal measures to actual standardized videofluoroscopic findings immediately following each single cup sip of thin liquid and a sequential sip task, and of course analyze any relationship between all these when it comes to some normal/abnormal dysphagia impairments as well as penetration/aspiration (and we wouldn’t expect anything less than 30 fps with Steele on board🤪). There’s also some blinding, some heavy-duty training that made me fantasize about this in my SLP dreams (an 8-hour VFSS rating lab by Dr. Steele + more training cases!🤩), along with some fancy vocal splicing clips and consensus-building that helped improve the overall accuracy of their maddening methods for using some ordinal ratings with Pen-Asp and MBSImP-related impairments🙃. Phew! That was a mouthful (and not to mention helpful for any future replication studies😉)!
The authors also give you a good review for those of us (me included🙋♀️) in how important sensitivity and specificity are when it comes to determining the predictive utility of a medical test (referencing Sackett’s teaching), basically how we can know if a wet vocal quality is predictive of anything (this’ll be important as you read on😉):
“Sensitivity is defined as the proportion of people with the underlying target disorder who display the abnormal clinical sign (and fail the test). When a test has high sensitivity, a pass result on the test rules out the underlying disorder.”
“Specificity is defined as the proportion of people without the target disorder who do not display the abnormal clinical sign (and pass the test). When specificity is high, a fail result on the test rules in the underlying disorder.”
“In order for a test to have high clinical utility, it should have high sensitivity, specificity, and negative predictive value, and a relative risk of greater than 1.” p.2 (Waito et al., 2011)
All this to say that unfortunately, the authors didn’t find anything significant enough to dramatically change our clinical SLPs worlds😩:
“Our data suggest that voice-quality measures, either perceived or derived from acoustic analysis, are not sufficiently sensitive or specific to the presence of penetration-aspiration or dysphagia.” p.8 (Waito et al. (2011)
If you’re about to bang your head against the wall because you’ve been waiting for something so significant it’ll change your life forever, keep in mind that their sample size in this study was a pretty huge mix of participants (no specific etiology requirement, and just an SLP from bedside or physician referral needed) and the authors admit that their protocol was pretty restricted (only 3 single cup sips+1 consecutive sipping) compared to a typical longer clinical bedside evaluation with more swallow opportunities or larger amounts (e.g. Yale Swallow Protocol). But here’s hoping there will be a replication study for this so we can find more answers for all of our questions!!🤞🤞
Luckily, there’s also the most recent systematic review by Santos et al. (2021) (we’re talking like, 3 months ago!!) that couldn’t be left out! This article also gives us some general knowledge about what’s already been looked at, what’s been found, and what we still need more answers to when it comes to any connection between dysphagia and post-swallow vocal changes:
“The term wet voice has been the main term used within the field of dysphagia to characterize change and is described as a sound with a bubbling aspect during post-swallow voicing. Nevertheless, vocal assessment methods for detecting dysphagia are poorly studied and have insufficient evidence for indication as a reliable method.”
“Although the evaluation of vocal change is used as one of the indicators of oropharyngeal dysphagia in clinical protocols, studies are controversial regarding the diagnostic accuracy relative to the findings of the VFSS, especially when time linked audio and video data are not available.” p.2 (Santos et al., 2021)
This review only included studies that looked at either method of phonation similar to Waito (i.e. perceptual/acoustic measures), AND must also have used VFSS to compare the results after analyses.
First off, does anyone wanna let any of these guys know that FEES is also an option for these studies seeing as how you can actually directly visualize all the structures and mechanisms for voice😅? Or, does anyone with a go-big-or-go-home mindset wanna replicate any of these studies with a combo for VFSS+FEES?!?!???
Anyhoo, the 17 articles they found out of a whopping 271 were concluded as the best of the best (some were excluded because of some found phonatory resection in patients!) and ranged in years 1999-2018, 6-250 participants across studies, and typically focused on neurological populations. Now, that’s a lot of data!
What did they find? To put it short and sweetly:
“It is not possible to obtain a consensus regarding the recommendation of the use of vocal evaluation as an accurate method for identifying swallowing alterations due to the heterogeneity of the vocal evaluation methods, the outcomes evaluated in the VFSS examination, heterogeneity in food and liquid consistencies, and the methodological quality of the studies.” p.12
Why you might ask? Well, to break it down across all the selected studies:
- Too much variability in the specific voice evaluation methods (acoustic, perceptual, both, etc) and parameters for these (what they actually included), most using GRBAS, fundamental frequency/noise-to-harmonics-ratio (NHR)
- Too much variability in actual vocal changes post-swallow, including wet voice (increased effort? pitch change?🤷♀️)
- Not all studies looked at voice changes immediately after a swallow and/or during VFSS (not all looked before at baseline for comparison either)
- Variable VFSS outcomes/procedures
- While most studies looked at aspiration/penetration changes/outcomes, they grouped these 2 separate aspects together so weren’t able to detect if these subtle differences in airway invasion mattered or not
- Variability for level of bias risks across different measures and methods
“Among the studies that conducted contingency analysis, low sensitivity (14–50%) was observed, yet with better specificity (78–94%).” p.6
There’s obviously more in the details (check out the article and you’ll be able to skim each article they included!), but overall, we still can’t rely on a single aspect of our clinical evaluation (wet voice) to know for certain this predicts penetration/aspiration.
Now, should we still pay attention to this to consider with other information, signs/symptoms, and use critical-decision making to determine our hypothesis at bedside for what we might think is happening and if further instrumental investigation is warranted???
Don’t turn your SLP-ears off for this scuba-diving sound just yet!
“Particularly regarding the wet voice parameter, there is no standardization for the classification, measurement there is no standardization for the classification, measurement, and analysis of the outcome, with evidence not being observed with association with the parameters that indicate swallowing alteration, with a low probability of detecting individuals with alterations (low sensitivity). However, wet voice was highly specific, detecting individuals without the condition.” p.12
So while it may not tell us a lot we can be certain of, and we don’t know how much of a “wet voice” means how serious an issue is (if it even is an issue), at least we may be able to sleep a little easier knowing if there is NO wet vocal change going on, the likelihood of significant swallow change may be less..🤷♀️ (although there is always that silent aspiration monster that haunts us at night too😳. . .)
Until more future research pops up to help us clinicians, keep listening with open ears, thinking with critical brains, and speaking with our up-to-date SLP mouths to order additional instrumental testing when needed.🤓
Articles Referenced: [FREE ACCESS for DRS members🙂]
Waito, A., Bailey, G., Molfenter, S., Zoratto, D., & Steele, C. (2010). Voice-quality Abnormalities as a Sign of Dysphagia: Validation against Acoustic and Videofluoroscopic Data. Dysphagia, 26(2), 125-134. doi: 10.1007/s00455-010-9282-4
dos Santos, K., da Cunha Rodrigues, E., Rech, R., da Ros Wendland, E., Neves, M., Hugo, F., & Hilgert, J. (2021). Using Voice Change as an Indicator of Dysphagia: A Systematic Review. Dysphagia. doi: 10.1007/s00455-021-10319-y