Title: Effects of carbonated liquid on swallowing dysfunction in dementia with Lewy bodies and Parkinson’s disease dementia
Author: Larsson, Torisson, Bulow, Londos
Journal Publication: Clinical Interventions of Aging
Study design: Retrospective study
Purpose: “The aim of this study was to evaluate swallowing dysfunction and carbonated liquid using videofluoroscopy in DLB and PDD patients.”
Population: patients with dementia with Lewy bodies (aka Lewy Body Dementia, LDB) or Parkinson’s disease dementia (PDD)
Inclusion criteria: diagnosis of LBD or PDD as defined by the consensus criteria from 2005 and after review of EMR; first examination if multiple were performed; 2006-2016 videofluoroscopic swallow study data
Exclusion criteria: any diagnoses other than LBD/PDD (no cognitive level, comorbidities, treatment exclusions)
We work with lots of people. We work with a bunch of different diagnoses. Let me edit that to emphasize WE WORK WITH THOUSANDS OF PEOPLE AND MILLIONS OF DIAGNOSES. Now, this is obvious to all of us. But when you might be on the other side of the table or hospital bed as ONE of those thousands to millions, I would imagine not caring as much about all the others and more concerned with myself and just how I am gonna get better.
Dementia itself is complicated and we’re constantly learning new things about it daily. Parkinson’s disease is something we are also aware of, and are still finding more and more information we had no clue about even up to now. We do know there can be certain pharmacological interventions to reduce, slow, or alleviate some symptoms of the disease processes, since completely resolving or eliminating it is not yet established. We know a holistic perspective that includes social, physical, spiritual, cognitional, and nutritional components can have far-reaching impacts. When it comes to speech/swallowing therapy, much of our research and treatments align with these approaches while also taking into consideration other modifications and different modalities. But, what if there’s more? What if that’s not enough?🤔
While I chugged along reading this article, I found myself with an even greater awareness of the impact our field can have. As clinicians, we’re naturally always looking for “the next best thing,” and guess what? So are our patients. Sometimes we get that A+ prize-winning intervention or result, and other times we come home with a dud and disappointed mindset. But we owe it to ourselves and our patients to continue to be open to new approaches while continuing to have discussions with our patients, colleagues, and medical co-workers.
The authors begin by recognizing that a handful of evidence has looked at the effects of carbonation during swallowing. How you might ask?? In short and the authors’ own words/references:
“Novel therapies are exploring stimulation of chemesthetic receptors, which can prevent aspiration by the activation of preventative reflexes. A way of achieving chemesthetic stimulation is to carbonate thin liquids, activating receptors by a carbonic anhydrase mechanism.” p.1216
They then quickly move on to state that at the time of the publication date, they had been the first ones to include this goal for the very special population of subjects with LBD and PDD. I know not everyone always agrees that the devil is in the details, personally I always like seeing more specifics in a hypothesis versus simply “carbonated liquid would improve swallowing when compared to thin and thickened liquid..” I wanna know WHAT will improve? Less aspiration? Less residue?? Better efficiency??? Quicker timing???? Tell meeee😩!!!!! ( I’m lookin at you 1-way hypothesis 😉 )
Luckily, the authors do dive more into detail for the parameters and variables they looked at. But after reading that simplified hypothesis I still couldn’t help get instant flashbacks overhearing clinicians and others saying similar, simplified phrases like “His swallowing has gotten better” “Ms. H’s swallow isn’t working right, we’re going to work on it to make it better” or my all-revered favorite: “They didn’t pass the swallow test”
If we want more questions answered, then all those details can be pretty important (especially to us clinicians!) versus simply GOOD<—>BAD, PASS<—>FAIL, GOOD<—>EVIL (ok, no one’s swallow is “evil”). It may be not as fun or fast, and yes, getting even a general answer sometimes if half the battle (anyone wanna take a tally count to how many things we know for certain in this field?👨🏫), but if your mechanic told you “Overall, your car died,” unless you were happy to get rid of it anyway (#beenthere), would you NOT be curious as to WHAT happened and WHY??
So, how did they look at all this?
Since it’s a retrospective study, they basically already had most if not all the data they needed to analyze. Now, even though there were only 66 referrals for videofluoroscopic swallow study (aka TVSS=therapeutic videographic swallowing study as it’s referred to in the study), 15 had to be thrown out for diagnoses other than the inclusion criteria, and 3 others for being a repeat versus initial examination.
That’s how they ended up with 38 patients with LBD and 10 with PDD.
Is that sample size perfect?
BUT, it’s a start.👍
That total actually changes when you think more about the demographics they chose to include, with an average age of ~76 years old, mostly male, a middle ground of ~21 months with diagnosis at time of VFSS (ranging 4-40 months), and the majority of both groups living at home. Something pretty interesting to point out from Table 3 is how subjective swallowing issues were pretty important in this (small) sample for this population (especially PDD). So if your patient is complaining of anything swallowing related, LISTEN!!
Even more important to keep in mind is that these demographics could easily represent the “client perspective/background” we often see when it comes to the famous EBP triangle, and something that as clinicians who bring the expertise, now armed with the external research, need to consider when linking all sides. Δ∇
So now that we know who they looked at and why, just how did they do this (and arguably more important), what (if anything) changed??
For a quick refresher, TVSS=VFSS=MBSS= “swallow x-ray” = “cookie test” = “that thing where they give you that gross stuff to swallow.” dɪsfˈe͡ɪd͡ʒə, dɪsfɑːd͡ʒə .🤷♀️
We know everybody does NOT do their instrumental the same (it’s okay, this is a safe place, you can admit it 😉 ), but this article’s institution protocol looked something like this:
- SLP+Radiologist 👩⚕️👨⚕️
- seated upright (wheelchair if needed)
- lateral view first (oral+pharyngeal swallowing functions)
- anterior-posterior view (if possible) to analyze asymmetry and follow at least 1 swallow through esophagus freely
- instructed to swallow freely and completely whenever ready
- General order of bolus materials in 3 and 5 mL doses:
- smooth fruit pudding
- smooth puree (fish or meat)
- thick paté
- chopped normal food
- thickened liquids
- carbonated thin liquids
- thin liquids
Yes, you read that right, that was a fish or meat puree in case you’ve been contemplating adding a protein-based option to your fluoro-suite menu (sidenote: anyone curious about doing a study if people are more eager and cooperative with a modified diet if classily labeled as paté???🤔😅).
Even though the article does add that the order of materials sometimes varies depending on the condition of the patient, take a moment to notice a stark difference in not only the materials, but the order of them. Confusion and curiosity hit me instantly🤨🤔. At least what I’ve frequently experienced as a routined foundation thin->thicker, liquids->solids (obviously depending on each patient’s needs and safety), with a common rationale for this being to reduce any remaining residue that in theory would be noted for thicker vs thinner consistencies,
(this is your chance to chime in guys 😉 )
⚠️ATTENTION⚠️: While VFSS video-recording for playback and frame-by-frame analysis was getting utilized, only 16 frames per second (f/s) were produced. As we all may know (if not, see the resource below for further great info!), this is 🚫NOT🚫 the recommended standard according to the CASLPO Practice Standards and Guidelines (PSG) for Dysphagia:
“The video or digital recording of the dynamic swallowing study should be captured and archived at a minimum temporal resolution of 30 frames per second without compression so that adequate information regarding the swallow is available for later review.”
“Penetration-aspiration events are more frequently missed in recordings with only 15 images per second. This suggests that penetration-aspiration events can sometimes be extremely brief (i.e., shorter than 1/15 of a second)”
(seriously, check out this amazing resource for even more amazing info❤️❤️!!)
Since the authors wanted to compare the effects of carbonated liquids with thin and thickened liquids, they chose to use 2 different analysis methods: describing what events were happening or changed from observations(literally meaning “hey look, this happened!“), and quantifying this as a way to demonstrate it (versus just “saying” what changed). The first is easier to understand, the second means using not only your possibly subjective/biased observations+descriptions but instead swapping this out for some other quantitative measure to prove change/lack of.
Here’s what they specifically looked at to accomplish these quantitative measures:
- Pharyngeal Transit Time (PTT)
- Pharyngeal Retention and penetration
“PTT was defined as the time (in milliseconds) from when the apex of the bolus crossed the level of the faucial isthmus to when the peristaltic wave left the cricopharyngeal muscle. Pharyngeal residue was defined as retention of material in the valleculae and/or pyriform sinuses.” p.1217
How’d they “score” residue?
Their very own informal protocol grading residue severity scale (“in relation to the perceived height of the contrast material considering the surrounding space“)…..
AKA a simple scale saying 1=No residue up to 4=Severe amount of residue
How’d they “score” penetration/aspiration?
By a shortened but informal-replica of the Penetration-Aspiration Scale .
From there, their statistical analyses looked at:
-how each liquid differed within each subject
- (in 1 person, was thin different than thick? thick different from carbonated? etc.)
-comparing all the liquids to see which one(s) were significantly different when equally compared
- (imagine one of those probability charts with all the possible different outcomes)
-how PTT changed between each group (PDD and LBD; men and women)
–any associations that could be compared
Now, if I spurt out Wilcoxon signed-rank test, ANOVA, Friedman test, Mann-Whitney U test, Spearman’s rank-order correlation, or Bonferroni—-you and I would possibly have a slight panic attack or feel our head spinning all the way back to our first Bon Jovi concert because we certainly feel like we’re
For now, I think limiting it to understanding that because there are soo many of those wonky-named tests being used for all the above analyses, it can be very important to make sure that doing “more” leaves you with something actually significant versus something fake. So here’s the tidbit for the day:
“Bonferroni correction is one of several methods used to counteract the problem of multiple comparisons.” (literally from Wikipedia, https://en.wikipedia.org/wiki/Bonferroni_correction)
Imagine a perfectionist baker constructing an exquisite 4-tiered unicorn cake, continuing to whittle away at the masterpiece of molded mixture, only to be left with a much smaller end product that definitely wouldn’t be perceived as ‘significantly‘ perfect to the customer………….basically, sometimes less (analyses) can be better for you answer (why larger sample sizes make this less worrisome😉).
Mr. Bonferroni can actually be a good thing since it aggressively helps control for false positives (aka saying you sing like Beyonce when you definitely don’t), and can help ensure you don’t just get “lucky” with all the tests you run.
Here’s some jam and jelly before we get to the toast (clearly I’ve been watching too many cooking shows these days👩🍳) :
“Thickened liquid worsened the degree of residue in four patients compared to thin liquid…This is similar to previous observations that higher viscosity liquid has a heightened risk of post-swallow pharyngeal residue, although probably still reducing penetration overall.” p.1219
To state the obvious after a long workday: thickened liquids had worse residue than thin liquids (it’s starting to seem this has also been drilled in many more heads lately). Since the residue scale they used was basically: higher number=more residue=worse, we’d want to see a negative (-) number in their Table S1. to say anything was at all effective.
“PTT was significantly improved with carbonated liquid compared to both thin and thickened liquids with a medium and large effect size, respectively” p.1219
I don’t know about you, but this got me asking, ‘Will that even matter if there are no meaningful changes in penetration/aspiration?’
“Carbonated liquid improved the severity of pharyngeal retention in six out of nine patients compared to thin or thickened liquid. One patient had worse retention with carbonated liquid compared to thin liquid.” p.1219
Picking this apart: Did carbonated liquids actually reduce residue? How could we know for sure with NO blinding and reliability? Does a small point change in their scale even mean anything without these factors, especially with only 9 people? Even if I’m interested in knowing more, I’m going to choose my grain of salt wisely here.
So, would carbonated be better than thin? Better than thick?
When in doubt: thin it out?🤷♀️
After taking a closer look (Table S1), only 6/10 subjects actually had reduced residue for carbonated vs. thick (this is what we are wanting to know more about) compared to 4/10 subjects for thick vs. thin. Which would mean 20% of the time, it could be possibly beneficial. In other words, out of every 5 patients you recommend carbonated liquids for, it might be beneficial for only 1 of them.
“When comparing carbonated liquid to other consistencies, it should possibly be the last liquid to be administered in the study protocol, since carbonated liquid has been shown to have a positive effect on corticobulbar excitability, which could potentially influence the performance of subsequent swallows.”
This last point caught my eye and got my brain-a-buzzing🧠, because I’m going to want to do/try anything to help my patients. I’d definitely be interested if carbonated liquids are presented last, if it would be able to clear any residue that remained, specifically in terms of the sensory/chemesthesis relationship, while also reducing risk for penetration/aspiration. . . .🤔🤔🤔
BUT–we’ll need a MUCH more detailed study setup first. Future studies will definitely need to consider control groups, follow-up for long(er)-term impacts for quality of life (since this one is primarily only focused on immediate effects), general well being, and presence of prandial aspiration pneumonia/death or general negative consequences in order to have a shot at being convincing enough evidence.🧐
Before we start having all our patients guzzle Mountain Dews and Club Soda, some more things to get straight:
While it’s great the study’s population is largely a bunch of different people who happen to have 1 thing in common to help its generalizability to the “real world,” they can’t go back in time to ensure every single thing was performed exactly how they wanted given the retrospective design. This, along with lack of randomization, blinding, and larger sample size are all HUGE cornerstone study recommendations to strengthen a study’s power. Additionally, remember why there was such a big deal to be made about the low frames-per-second in the study?
“The frame rate used was limited to 16 f/s, which might have resulted in instances of missed penetration and contributed to the coarse measurement of the PTT. “
Finally, with so many patients on medical/dietary restrictions for diets, budget cuts, and of course, time, it’s very unlikely our SNFs will be ordering loads of Perrier anytime soon. While other studies have used ginger ale, sodium bicarbonate, and other forms, thinking back to that EBP triangle, these just may not be available or widely preferred, unfortunately.
Is this saying carbonation is a bona-fide fix to this population? NOPE😕.
Is it something that a clinician can keep in the back of their mind next time they meet Mr. Jones with LBD or Ms. H with PDD for an instrumental swallow study? Maybe🤔.
“Our main findings show that swallowing dysfunction is common and that carbonated liquid could improve swallowing function and therefore should be evaluated as a useful and simple non-pharmacological therapy in this patient group.”
Will it mean you should do this?
That is where that whole clinically-critical thinking, understanding the evidence, and connecting with our patients to understand their wishes and values come into play. And just like about anything else, using a holistic, individualized treatment plan that absolutely, 155% without-a-doubt absolutely neeeeds a direct visualization of the swallow from an instrumental swallow study in order to even consider if this strategy is where we as clinicians can start.😉😊
How can you use this article?!?
Some possible questions to ask:
Is your patient in the same population, with similar demographics?
Are they able to participate in an instrumental study?
Does your patient have a pharyngeal swallow? Do they have residue with thicker stuff? Maybe they’re NPO, declining any thickened liquid recommendations, and begging you for something, anything?
These are only some questions to ask before trialing carbonated thin liquid during an instrumental evaluation (NEVER recommending without one!).
Or, maybe the last question will be,
Will we be inclined to keep these in our dysphagia bag/box/toolkit?
What are some other questions YOU would ask or have asked for the rationale to trial carbonated liquids in instrumental evaluations?!? Have YOU used carbonated liquids with this population?!? What are some of YOUR stories?!?
- “A pharyngeal-type dysfunction or combined oropharyngeal dysfunction was seen in 71% of the patients, while only 8% had a purely oral dysfunction”
- “Notably, some patients with a confirmed pharyngeal retention or aspiration did not have any subjective swallowing complaints, which is in keeping with previous findings in patients with DLB and PD”
- “In those patients with a swallowing dysfunction on videofluoroscopy, 87% were found to have an improved overall swallowing function with carbonated liquids”
- “Although an improved PTT alone cannot indicate a safe swallow, it is a relevant measure as it has previously been shown that PTT is prolonged in PD patients with a history of aspiration pneumonia”
- “Silent aspiration is a risk factor for pneumonia and early death, and our research finding further highlights the importance of clinicians and other health care professionals to suspect swallowing dysfunction, even in cases where there are no subjective swallowing problems”
- “The frame rate used was limited to 16 f/s, which might have resulted in instances of missed penetration and contributed to coarse measurement of the PTT. “
Article Referenced: [FREE ACCESS]
Larsson, V., Torisson, G., Bülow, M., & Londos, E. (2017). Effects of carbonated liquid on swallowing dysfunction in dementia with Lewy bodies and Parkinson’s disease dementia. Clinical Interventions In Aging, Volume 12, 1215-1222. doi: 10.2147/cia.s140389
For more articles and info on carbonation+dysphagia:
Bulow, M., Olsson, R., & Ekberg, O. (2003). Videoradiographic Analysis of How Carbonated Thin Liquids and Thickened Liquids Affect the Physiology of Swallowing in Subjects with Aspiration on Thin Liquids. Acta Radiologica, 44(4), 366-372. doi: 10.1034/j.1600-0455.2003.00100.x
Krival, K., & Bates, C. (2011). Effects of Club Soda and Ginger Brew on Linguapalatal Pressures in Healthy Swallowing. Dysphagia, 27(2), 228-239. doi: 10.1007/s00455-011-9358-9
Morishita, M., Mori, S., Yamagami, S., & Mizutani, M. (2013). Effect of Carbonated Beverages on Pharyngeal Swallowing in Young Individuals and Elderly Inpatients. Dysphagia, 29(2), 213-222. doi:
Sdravou, K., Walshe, M., & Dagdilelis, L. (2011). Effects of Carbonated Liquids on Oropharyngeal Swallowing Measures in People with Neurogenic Dysphagia. Dysphagia, 27(2), 240-250. doi:
Steele, C., & Miller, A. (2010). Sensory Input Pathways and Mechanisms in Swallowing: A Review. Dysphagia, 25(4), 323-333. doi: 10.1007/s00455-010-9301-5