Bubbly ideas for the Parkinson’s Disease (Plus) population

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Title: Effects of carbonated liquid on swallowing dysfunction in dementia with Lewy bodies and Parkinson’s disease dementia
Authors: Larsson, Torisson, Bulow, Londos
Journal: Clinical Interventions In Aging
Year of Publication: 2017
Design Type: Clinical Interventions of Aging
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)

  • Only got a sec?
    • Carbonated liquids *might* help reduce pharyngeal residue and/or reduce airway invasion, but it is likely very patient specific even in the PDD/LBD populations (we need more data!)
  • Only got a minute?
    • 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
    • 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
    • we also intended to compare the severity of retention and depth of penetration
      between thin, thickened and carbonated liquids using quantitative measures. However, by only looking at one swallow for each of the consistencies, it was apparent that we did not fully capture penetration and retention to the same extent as the overall descriptive assessment of the full examination
    • each patient still needs an individual assessment to ensure a positive and safe swallow response to carbonated liquid prior to clinical recommendation
  • Got more time? Keep Reading!!

We work with lots of people and 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 being much more concerned with myself and just how am I gonna get better versus the thousand others.

Dementia itself is complicated and we’re constantly learning new things about it daily. Parkinson’s disease is something we are also aware of, yet are still finding out 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 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. And 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😩!!!!!


Luckily, the authors do dive more into detail for the parameters and variables they looked at. But after reading the simplified hypothesis I still couldn’t help get instant flashbacks to how our field and expertise can easily be oversimplified with statements like, “His swallowing has gotten better” or my all-revered favorite, “Did they pass?

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 (no, no one’s swallow is “evil”). It may be not as fun or fast, and yes, getting even a general answer sometimes is half the battle–but if your mechanic told you “Well, your car doesn’t work,” unless you were completely satisfied with that conclusion and happy to toss it anyway, would you not be curious as to what happened and why??

Who did they look at?

Since it’s a retrospective study, they basically already had most if not all the data they needed to analyze. While 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 outside of 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?

Nope. 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 point of ~21 months post diagnosis at the 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. Which is something that as clinicians who bring the expertise, now armed with the external research, need to consider when linking all sides. Δ∇

How did they do this?

good stuff

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:
  1. smooth fruit pudding
  2. smooth puree (fish or meat)
  3. thick paté
  4. chopped normal food
  5. thickened liquids
  6. carbonated thin liquids
  7. thin liquids
am i wrong
(this is your chance to chime in guys😉)

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???🤔😅). The last thing I have to say about the PO options is the order of solids before liquids, as the frequent rationale can easily be explained for the reverse as to avoid possible remaining residue from increased viscosities. But hey, maybe that’s just me?🤷‍♀️

⚠️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

(next next hopefully we can use more standardized measures like Normalized Residue Ratio Scale [NRRS] or Yale Pharyngeal Residue Severity Rating Scale🤓)

How’d they “score” penetration/aspiration?

By a shortened but informal-replica of the Penetration-Aspiration Scale . Where 1= no penetration, and 4=tracheal penetration” (below true vocal cords)

what does it mean

From there, their statistical analyses looked at:

1) how each liquid differed within each subject

  • (in 1 person, was thin different than thick?  thick different from carbonated? etc.)

2) 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)

3) how PTT changed between each group (PDD and LBD; men and women)

4) 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’d certainly feel like we’re…..

Image result for living on a prayer gif

For now, an easier way to think about itwould be 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 there’s no double dipping or over-analyzing so much that it makes it looks like something is actually significant versus something fake. Put another way:

“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 your answer, which is(why larger sample sizes make this less worrisome, and also 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), while helping ensure you don’t just get “lucky” with all the tests you run.

More importantly: What (if anything) changed?

Here’s some jam and jelly before we get to the toast (sorry guys, 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. 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 in order 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

“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 1-point change in their scale even mean anything without these factors, especially with only 9 people? And what’s more likely on everyone’s minds: Will that even matter if there are no meaningful changes in penetration/aspiration?

“The descriptive assessment showed that 27% of patients had evidence of tracheal penetration at some stage of the examination. This is similar to rates seen in another videofluoroscopic study of PD patients.”

“The depth of penetration was improved with carbonated liquid in the three patients with observed penetration on thin or thick liquid.” p.1219

After doing a bit more digging, it was incredibly hard for me to find any chart, graph, or image proving those who reportedly had the deeper degree of airway invasion based on their own grading system, as their own Supplementary table didn’t show any “4’s” indicating the “tracheal penetration” category?? All I could find were “1’s and 2’s” down the table for all consistencies (granted thin and thick liquids did improve from “supraglottic penetration” to “no penetration” according to this table, equivalent from a PAS 2 to PAS 1). Guess I’ll just be up all night wondering how much of a difference carbonation might have improved airway invasion?🤷‍♀️

Which to choose: Carbonated, Thin, or Thick??  

odd in your facor
(the irony of the term hunger games in our field is not lost on me)

After taking an even closer look (Table S1), only 6/10 subjects actually had reduced residue for carbonated vs. thick compared to 4/10 subjects for thick vs. thin. Which would mean 20% of the time, it could possibly be 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 obviously as clinicians we’re going to want to try anything to help our patients. Unfortunately, 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.🧐

“we also intended to compare the severity of retention and depth of penetration
between thin, thickened and carbonated liquids using quantitative measures. However, by only looking at one swallow for each of the consistencies, it was apparent that we did not fully capture penetration and retention to the same extent as the overall descriptive assessment of the full examination.”

“Nevertheless, carbonated liquid did improve the severity of retention and depth of penetration in certain individuals (Table S1), suggesting that it could be useful for contributing to a safer swallow.” p. 1219

so much

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. And 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😕.

“each patient still needs an individual assessment to ensure a positive and safe swallow response to carbonated liquid prior to clinical recommendation” p.1220

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?

This is where the whole clinically-critical thinking, understanding the evidence, and connecting with our patients to understand their wishes and values come into play. And just like anything else, using a holistic, individualized treatment plan that includes a needed direct visualization of the swallow from an instrumental swallow study in order to even consider such as a strategy, is absolutely where we as clinicians can start while we start keeping these in our dysphagia box.😊

mini sodas

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?!?

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&rsquo;s disease dementia. Clinical Interventions In AgingVolume 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 Radiologica44(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. Dysphagia27(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. Dysphagia29(2), 213-222. doi:
  • Sdravou, K., Walshe, M., & Dagdilelis, L. (2011). Effects of Carbonated Liquids on Oropharyngeal Swallowing Measures in People with Neurogenic Dysphagia. Dysphagia27(2), 240-250. doi:
  • Steele, C., & Miller, A. (2010). Sensory Input Pathways and Mechanisms in Swallowing: A Review. Dysphagia25(4), 323-333. doi: 10.1007/s00455-010-9301-5