Title: Interventions for oropharyngeal dysphagia in acute and critical care: a systematic review and meta-analysis
Authors: Duncan, McAuley, Walshe, McGaughey, Anand, Fallis, & Blackwood
Journal: Intensive Care Medicine
Year of Publication: 2020
Design Type: Systematic Review & Meta-analysis
Purpose: “The objective of this review was to determine the effectiveness of dysphagia interventions compared to standard care in improving oral intake and reducing aspiration for adults in acute and critical care settings.”
Population: critical care and acute care adult patients with diagnosed dysphagia
Inclusion criteria: randomised-control trials, quasi-RCTs testing dysphagia interventions; adult patients >18 of any sex, age, ethnicity and stage of illness
Exclusion criteria: Cluster-RCTs; studies conducted in rehabilitation, long-term care, or outpatient settings

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• Only got a sec?
  • Because current studies use a variety of different outcome measures and a severe lack of high quality studies in our field, we can’t say for certain the effectiveness of interventions in setting/population
• Only got a minute?
  • “Both reviews highlight wide variability in reported outcomes and their timepoints across studies; various subjective and objective assessment tools were used to measure swallow-related outcomes and moderate to very low study quality. The variability in outcome reporting in this review emphasizes the need for a core outcome set for dysphagia intervention studies in intensive care“
  • “The pooled results showed a beneficial effect for swallowing therapy [for incidence of pneumonia]. Subgroup analysis of acute versus critical care showed a significant effect for acute care and no evidence of a difference for critical care“
  • “Effect sizes were not statistically significant for aspiration incidence post-treatment, quality of life, length of hospital stay, or nutritional status. One review outcome, change in oral and pharyngeal secretion severity were not reported in any study“
  • “With such limited data, we have low certainty in subgroup findings and cannot confidently recommend specific interventions for acute and critical care populations at this time“
  • “Intensive care patients, however, present with dysphagia for a myriad of different reasons..Their central swallowing network is disrupted due to the brain lesion, but the presence of a tracheostomy will also affect laryngeal sensory receptors necessary for safe swallowing, in the context of likely continuing skeletal muscle atrophy during their intensive care stay“
  • “they suggested tongue-palate resistance training, chin tuck against resistance (CTAR) and respiratory muscle strength training (RMST) are all biologically plausible interventions that could target skeletal muscle atrophy of the swallowing mechanism commonly reported across both post-extubation and tracheostomised intensive care populations“
• Got more time? Keep Reading!!

As therapists (and really, human beings) we yearn to make a difference. Whether one person or millions, whether small or monumental, it’s our professional purpose. Foremost, we try to rehabilitate patients. We help them return to their previous abilities, to their previous lives. But, if change can happen at the flash of light in the setting of the acutely ill, how can we be sure what is actually a result of our therapeutic hands?

Acute medical floors and critical care ICU settings can feel like a faraway world from outpatient, inpatient rehabilitation, and skilled nursing facilities. The terms “critical” “acute” and “intensive” can stand alone to summarize the severity of just why patients are there. As SLPs, we are often expected to discover, decide, diagnose, differentiate, designate, delineate, delegate, demonstrate, and dedicate every minute while on these floors (document would also obviously make the list😉). Because medical status can change in the blink of an eye for multiple reasons, our evaluations, treatment plans, and recommendations often metamorphosize simultaneously as well.

A lot of the time in acute/critical care, we may not be able to implement many strategies, exercises, techniques, or recommendations due to complex reasons (i.e. alertness, physical deficits, cognition, tubes, timing, etc.). So, what do we do with critical patients?

I can’t be the only SLP to ever think, “Is what I’m doing making a difference?“

⚠️⚠️WARNING:⚠️⚠️

This article is not for the faint of heart

I know I definitely had a hard time grappling with some of what I read, but peeling these layers back on what we don’t know keeps pushing us forward as professionals in our field.

Please read at your own risk of uncovering reflective questioning, biases, and challenges to any previous notions that “because we are medical professionals,” our presence is the end-all-be-all . . .🤔

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“Dysphagia in patients who are acutely and critically ill is often multi-factorial.” p.1

The authors were nice enough to ease us into this madness with the most obivous😊. . .

Why focus on the acutely ill population?

Well, we do have individual studies that look into these populations and settings already, but their designs and quality are as scattered as all my pup’s toys across the floor. So the authors had the brave and truly cumbersome idea of gathering all these studies, picking which ones would be rated ‘high enough quality’, and compared their data to try to find out…

What, if anything, is working in these settings? 

(A pretty critical thing, don’tchya think?)

Hopefully by now, you’ve got a handle on the idea of systematic reviews and meta-analyses— if NOT, checkout But…Why? A systematic look if patients actually adhere to your recommendations, or take 5 seconds to Subscribe to SLP R&R to download your own 💥freebie💥 Research Cheat Sheet so you won’t be scared away when you see these terms😁!!

The authors use a TON of various published, certified, and registered methods for a TON of their protocols for searching, identifying, selecting, discarding, reviewing, comparing, and analyzing all the 4,893…no wait, 4,610….no, 99 full-text….oh, only 22 studies they officially included in their final analysis. What that means is they did all the dirty work for you so you don’t even have to guess which articles are best/worst quality! (Oh, and not to mention they included articles up to MARCH 2020, can you say current?!?!?!)

If you thought only having 22 studies to look at and compare is easy, think again because for every study there’s also a handful of outcomes and variables that come with it!!

But first….

What does “acute” even mean? (besides an angle or to describe my puppy who is a cute one😍😊)

“Acute care was defined as any acute hospital ward or unit (i.e. medical, respiratory, surgical, neurological or stroke units). Critical care was defined as intensive care units, with no limitation regarding intubation/ventilation times or the presence of tracheostomy in study participants.” p.2

Nowadays, we have a few handfuls of dysphagia interventions. Did the authors look at every single maneuver, strategy, exercise, and modality we clinicians have at our fingertips?

But they did look at studies that used “dysphagia intervention delivered alone or in combination with traditional swallowing rehabilitation versus traditional swallowing rehabilitation, usual care or placebo (i.e. studies using a sham intervention or no intervention at all).” I’m not the most traditional person, so since there’s no definition or criteria for what “traditional therapy” is🤷‍♀️, I had to assume going forward this merely meant direct/indirect dysphagia rehabilitation like exercises such as Effortful swallows, Masako, Maneuvers like Mendelsohn, etc. (I also assumed that compensatory strategies like head turns or diet modifications, etc. were not included in this ?🤷‍♀️🤷‍♀️). Additionally, the studies they looked at focused on pretty typical populations we see as well: stroke in acute (19), tracheostomy in ICU (2), and general ICU (1), with an average age across all participants being 70 years old.

“Nine interventions, including electrical and magnetic neurostimulation approaches and muscle strengthening treatments were identified.”

Here’s the shortlist of what interventions in those 22 studies made the cut for their analysis and were basically good enough quality😉:

• transcranial magnetic/direct current stimulation
• tongue-palate resistance training
• respiratory muscle strength training
• pharyngeal electrical stimulation
• neuromuscular electrical stimulation
• chin tuck against resistance
• acupuncture
• swallowing exercises (including effortful swallow training)
• behavioral intervention

I know what you’re thinking… ‘But not all interventions target the same things!‘😤

Not to fret! When reviewing the 22 studies that used dysphagia interventions, the authors had specific outcomes they were looking for (heads up–all of these actually turned out to be RCTs!)

Primary outcomes:

• time taken to return to oral intake and aspiration incidence post-treatment
  • >5 Pen-Asp score

Secondary outcomes:

• incidence of pneumonia
• quality of life (SWAL-QOL)
• length of hospital stay
• change in secretion severity
• change in pharyngeal residue severity
• nutrition status
• intervention-related adverse events

And don’t forget: They also planned on analyzing and comparing the following groups as well:

• acute vs critical care
• younger vs older
• types of interventions

To summarize: yes, they looked at aspiration/penetration as well as pneumonia incidents, but also many many more meaningful areas that would likely be related to the patient’s recovery. But alas…..not every single one of these original studies included all of these outcomes they were trying to find out (more of a this or that situation😕)

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Before going on to the results for what the authors found, I felt it’s a perfect opportunity to have a quick ‘research lesson of the day‘ on something the authors brought up🤓 (and isn’t usually mentioned as much).

First, the authors describe measures to look at “treatment effect,” which basically means “does it solve the problem” as explained by Carnaby-Mann’s amazing and short article (seriously, easy read and honestly sooo helpful👏👏!!)

Second, let’s talk about risk ratio. I for one, am only sometimes a risk-taker (casinos-no❌, skydiving-yes✅), so I am probably someone who naturally would like to know what the risks are for this versus that. Luckily, that’s just what this stat does:

“The relative risk (also known as risk ratio [RR]) is the ratio of risk of an event in one group (e.g., exposed group) versus the risk of the event in the other group (e.g., nonexposed group).” Common pitfalls in statistical analysis: Odds versus risk (2015)

In their review, the authors are essentially wanting to find out if those that were treated with the dysphagia interventions had better outcomes compared to those who had ‘traditional’ intervention (or no therapy at all). This stat uses a reference of “1,” meaning if RR is great than 1, the outcomes (longer hospital stay or pneumonia, for example) is more likely to occur with an intervention, but if it is less than 1, it’s less likely to occur with the intervention. Just something to keep in mind later on as you mull over all the results..

<—————————————-1—————————————->

Also be sure to remember that each of the outcomes is different in their wording😉!! So if you’re super tired from arguing with a manager about getting an instrumental for Mrs. J for the 100th time, or if you’ve had a few glasses of wine to unwind after running up-and-down all the floors of the hospital, you may wanna do a re-read once your brain has had time to rest so you can fully process everything with a great critical eye😉.

One more reminder is that the authors also point out that they only used the number of participants actually analyzed in each study versus the number of people they had recruited.

Why does this matter?

Because people drop out, can’t make it, or can’t be reached for follow-up in studies, which ultimately skews any data and results (just like if you’re planning a party where 88 people RSVP, but only 25 show up😑). For future research reading, that means results and what authors might try to say may look waaay more effective and powerful versus the actual number of people they collected data from (if you have 88 plate settings prepared, it looks a lot more important than 15😄).

The authors keep going with a bunch of other cool-nerdy-research things, but I’ll just let you peruse those for your own pleasure😉🤓.

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Back to what they found from systematically reviewing and analyzing the (ONLY) 22 studies!

Get ready, because there is are a LOT of results to take in. Some good, some bad, some ugly that you may not want to look at. But keep in mind, we as clinicians need to know not only what to do for our patients, but also if what we’re doing is actually significantly & clinically making a difference in their recovery. Sometimes that may mean we stop certain practices based on what we learn (I mean, hands up for all those who were taught way back that rubbing the back of throats was helpful and chin tuck=aspiration cure🙋‍♀️🤦‍♀️🙇‍♀️?!?).

The Good:

Luckily, all the 22 studies gave a rationale for their treatment, materials, and protocols as well as the number, frequency, timing, and intensity of any treatment session, which really helps others be able to replicate it at their own facilities and patients. Here are the main positive outcomes from what they found:

Incidence of pneumonia: “The pooled results showed a beneficial effect for swallowing therapy. Subgroup analysis of acute versus critical care showed a significant effect for acute care and no evidence of a difference for critical care.”p.6

Here we can say in regards to reducing pneumonia, swallowing intervention does make a significant enough of an impact, and more so in acute versus critical care. On a much larger issue at hand, is why only 8 trials out of 22 looked at this outcome!?!?

Change in pharyngeal residue severity: “Meta-analysis of three studies reporting continuous outcomes found a beneficial effect from swallowing therapy. Subgroup analysis of interventions showed an individual effect for both RMST and chin tuck against resistance but no statistically significant difference for effortful swallowing training.” p.8

So if the goal is to try to reduce pharyngeal residue (in a way more specific than min-mod-max residue), swallowing therapy CAN make a significant enough of an impact, and specifically RMST and CTAR could be more advantageous versus effortful swallowing training…interesting😮!!!! (Anyone wanna find out if there was any biofeedback utilized for the one Effortful swallow training study?!???🤔🤔). While some might be asking, “What does it matter if there’s less residue if they still can’t eat or stay longer in the hospital?!” we gotta keep reading to know more.

Sidenote** only 4 out of 22 studies reported this outcome (and they all used different measures😕)

Quality of life post-intervention: “Subgroup analysis of intervention types found effect sizes were statistically significant for acupuncture but not for tongue-palate resistance training…A third study testing NMES reporting…swallowing therapy showed evidence of a difference.” p.7

Ok, this one ya gotta read the fine print because the one study for NMES used the same scale as the others, but differently🧐. Either way, seems like when lumped altogether, therapy doesn’t make enough of a significant impact for quality of life, BUT when picked out, acupuncture and NMES may make some type of difference.

Maybe it makes sense seeing how a) acupuncture is more known for a holistic side of medicine and addressing things differently, and b) maybe NMES might be used more often in head&neck cancer patients, so it might be that any improvement (even *technically*/significantly small) might be perceived as positive for this unique population?🤷‍♀️

So we now know our efforts through various interventions can reduce the possibility of pneumonia and also change the amount of pharyngeal residue, while some might have an impact on quality of life.✌️

Some other important pieces to hold on to:

Intervention‑related adverse events: Ten studies testing pharyngeal electrical stimulation, neuromuscular direct current stimulation, neuromuscular electrical stimulation, and acupuncture descriptively reported no adverse outcomes.” p.9

So these specific therapies at least (which #TBH, are definitely not “traditional”) don’t have harmful consequences.🤨🤷‍♀️ (Unfortunately, I would bet my last pizza slice that most acute-care SLPs are not using most of these a lot, so make sure to keep reading on about the more common therapies!!🤓)

“tracheostomised, acute stroke patients were treated using pharyngeal electrical stimulation (PES) in two studies. Significant group differences were found in primary outcome: time to tracheostomy decannulation but no significant differences in length of stay, tube-feeding cessation or return to oral intake.” p.10

This obviously has to be taken with a few grains of salt depending on who it is. On the one hand, I’d say getting decannulated is definitely a positive outcome!👍 On the other hand though, it may not mean that much if you’re still not eating and have to stay just as long at the hospital. (See the last point from above where I’ll bet my last LAST pizza slice again since the generalizability to common-folk clinicians for this is slim to none.😕🙁😔)

“The third completed study with a general ICU population involved swallowing exercises/oral stimulation delivered during intubation and found significant improvements in swallowing efficiency but no group differences in aspiration/pneumonia incidence or length of stay.” p.10

Again, it depends if you see the glass as half empty (no differences in aspiration/pneumonia or reduced stay at a hospital) or half-full (more efficient at swallowing) here.⌛️⏳🤷‍♀️

Some research nerds (🙋‍♀️)  might point out how cool it was that the authors contacted an “expert advisory panel” consisting of pretty well-renowned authors and researchers involved in acute/ICU care in order to provide scientific rationales for non-traditional interventions (FYI: acupuncture and non-invasive brain stimulation were met with skepticism and unrealistic rationales):

“they suggested tongue-palate resistance training, chin tuck against resistance (CTAR) and respiratory muscle strength training (RMST) are all biologically plausible interventions that could target skeletal muscle atrophy of the swallowing mechanism commonly reported across both post-extubation and tracheostomised intensive care populations.” p.10 

“In the interim, outcomes proposed in completed and ongoing ICU studies and recommended by an expert advisory group may be considered” and include:

• physiological outcomes

°

functional outcomes

°

psychological outcomes

°

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The Bad:

While all studies told you what they did, how, when, and why, only 13 explained if treatments were specifically tailored, and none of the studies reported if there were any modifications to interventions or if patients adhered to the intervention or not, so we really won’t know the specifics of the procedures and if patients even followed them😕. (For more on patient adherence for dysphagia interventions, see But…Why? A systematic look if patients actually adhere to your recommendations)

More bad news: to date, NO systematic review has evaluated dysphagia interventions conducted in intensive care.😮😯😲🤯😫

Nutritional status: “One trial comparing pharyngeal electrical stimulation to standard care reported on nutritional status (measuring blood albumin g/L), but the effect size was not statistically significant.” p.8

Needless to say, that one needle-in-a-haystack turned out to be broken anyway🤷‍♀️.

Change in oral‑pharyngeal secretion severity: “This outcome was not reported in any included studies in this review.” p.8

Intervention‑related adverse events: “Meta-analysis of data from two studies showed no significant difference between number of adverse events reported during swallowing therapy or standard care.“ p.9

Whelp, I guess we’re not making anything worse (at the same time, apparently doing nothing has the same effect though)???😓

Quality of life post‑intervention: “Meta-analysis of data from two studies showed no evidence of a difference from swallowing therapy versus standard care.” p.9

Outside of the fact that only two good-quality studies looked at quality of life as an area of concern, apparently we clinicians might sometimes be guilty of having the “white knight complex,” where we feel like we have to help and make things better, when it reality, doing nothing may have the same impact?😩

It’s hard to face reality, and it’s much harder for us to know for sure if implementing specific dysphagia interventions or modalities in these populations will actually prevent anything negative occurring, improve overall quality of life or nutrition, or reduce secretions. . . .

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The Ugly:

“Both reviews highlight wide variability in reported outcomes and their timepoints across studies; various subjective and objective assessment tools were used to measure swallow-related outcomes and moderate to very low study quality. The variability in outcome reporting in this review emphasizes the need for a core outcome set for dysphagia intervention studies in intensive care.” p.10

This point can be really crucial to break apart and process, because while so many things may turn out to seem statistically not helpful, not all of these studies are equal in their results, outcomes, and quality. So while the overall finding may be “a bad apple,” really, we’re comparing a sour green apple to a sweet red apple🍎🍏.

Time taken in days to return to oral intake: “One trial reported this outcome and compared a behavioural intervention (i.e. swallowing exercises and oral stimulation) to standard care (no swallowing related exercises) in an intensive care setting. Swallowing therapy showed no evidence of a difference in the time to return to oral intake.” p.5

I know, I know. Take your time to wipe your jaw up from the floor and take a sip of something strong, because this was hard to swallow my friends. Something that I found equally as troubling and super surprising, was the fact that only one study even reported this outcome!!

Nonetheless, let’s keep going. . . 😬

Aspiration incidence post‑intervention: “Swallowing therapy showed no evidence of a difference in reducing aspiration post-intervention (for swallowing therapy versus standard care).” p.5

Not only did dysphagia intervention collectively not make a significant difference than not doing anything, but specific interventions like NMES or RMST didn’t either. Take a breath here, because only some authors of the (FOUR!) studies provided some unpublished data, while other authors stated data was unavailable, and some declined to provide information regarding the total number of patients with PAS>5 indicating aspiration. I can only hope we can all sleep soundly knowing there is so much unknown data floating out there.😅

Length of hospital stay: “Meta-analysis of data from four studies showed no evidence of a difference from swallowing therapy versus standard care.” p.7

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Ok, let’s take a step back here and breathe before we all Lose.Our.Minds🤯🤯🤯🤯

I won’t leave you high and dry here, but there is just sooo much to process while avoiding taking all of that at surface value like I did the first time reading through (the headaches were real guys😓😩).

Since we’re talking in terms of “criticalness,” the critical things to remember throughout all this is that:

1. There are only 22 studies reviewed

Why does this matter? We all know how many dang research studies and articles there are out there. So using the very detailed, comprehensive, and thorough rating system this review used, they really only looked at the best of the best. Unfortunately, those “Bests” told us not the best news. Meanwhile, there are still many studies out there that individually may show very different (and more positive) results, but just may not be the top=notchquality.

2. Not all studies reported on all the outcomes (so really, less than 22 for some outcomes)

Why might we care about this? Well, like the “fish in the sea” saying goes, when you have less fish in the sea, you’re kinda stuck with whatchya got. But maybe we just need to start adding more fish here?🐟🐠🐡

3. Statistical significance may NOT equal clinical significance

And, in my opinion, the MOST important thing to remember while not only reading the article but also while working in acute/ICU floors is:

There are SO MANY THINGS GOING ON MEDICALLY HERE!!!!

I can’t imagine trying to piece apart all the medically-related factors and variables to know how much those outweigh our therapy effects, and (despite no publication bias found) I think the authors are also able to acknowledge this as well with some more limitations:

• “The majority of trials which were included were conducted in a single-centre setting (n =19) with three multi-centre trials“
• “No studies included frailty assessments.” (Something we now know can be a factor for dysphagia rehabilitation and adverse respiratory risks as well as malnutrition/dehydration)
• “Eight clinical assessments evaluated function based on bedside clinical signs and symptoms and clinicians recommended altering oral diet/fluid consistencies and feeding supervision. Six validated rating scales were used during videofluoroscopy/endoscopy assessments to grade swallow physiology at oral, pharyngeal, and upper oesophageal stages. Average baseline scores for experimental and control groups across all studies indicated moderate to severe dysphagia.”
• “No studies clearly reported that personnel delivering the intervention were blinded and only 43% (10/23) of studies clearly reported that participants were blinded to the intervention.“

So even though yes, we might’ve just gotten a huuuge reality check in the gut (and also a wake-up call), don’t forget that WE DO NOT HAVE ENOUGH DATA!! At least to adequately compare different groups for different outcomes, with different interventions, in different settings, at different points in time.

Anyone else feeling this right about now?!??!?? Trust me when I say, you are NOT alone!❤️

Aside from trying to not have an SLP-existential crisis (one of many, actually), here are some ways I personally think we can move forward:

CLINICIANS:

We have GOT to make it a point to know what we’re doing and why we are doing it with these patients during these critical times in their medical care. Personally/professionally, I’ve been trying to be more open to using different interviewing skills to find out if these acute patients even want to do these interventions first of all (obviously when cognitively appropriate😉). Obviously asking someone heavily sedated with a tube down their throat these questions would not be the best use of time😏, but that’s why the next point is even more important.

Knowing what the purpose (whatever it is) of what we are doing at the bedside of a patient is more critical than having the best gadget there is. What’s the point of having a vacuum if I don’t have electricity? What’s the point of showing up early if it’s on the wrong day? So just like our clinical skills, what’s the point of coming into the room, if we are not contributing something beneficial? Maybe having someone swallow hard on ice chips is the best and only thing that we can do at the moment, or maybe coming back to follow up in a couple of days may be better for that patient to allow for more rest and recovery, or even be able to complete a much needed procedure that could have far more impact on their recovery than us shoving some applesauce down their throat in order to “see a swallow.” Just like how some interventions may be similar but more effective iwth different tools, our patients and their medical care are the same.

Okay, off that slippery soapbox…..🗣🧼😁

RESEARCHERS:

Can we please, PLEASE, P-L-E-A-S-E get some better quality studies😂. To be fair, I understand how hard studies are not only to put together and manage let alone fund🤑. But we really need something to hold on to that rationalizes what the epitome of our existence is (or at least feels like) in the acute realm. Clinicians want to help patients, we also gotta know what we’re doing actually matters and makes a significant enough of a difference🙂. Standardized protocols, a consistent list of measures, and strong, powerful studies can be beneficial to all.🙏

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How can you use this article?!?

Look, we’re not going to get banned from ICUs and hospitals because of these findings. But it can give us things to think about.

How might this change clinical practices, researcher responsibilities, and our field going forward????

Do you feel like you are able to contribute something more than what these findings portray?

What kinds of things do you consider before evaluating or intervening in a patient’s care??

Do you have different clinically relevant findings?!?

How do you feel about this review’s results????

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Takeaways:

• “With such limited data, we have low certainty in subgroup findings and cannot confidently recommend specific interventions for acute and critical care populations at this time.”
• “Days taken to return to oral intake were considered an important patient-relevant outcome in this review but were reported in only one trial, and effect sizes were not statistically significant.”
• “Effect sizes were not statistically significant for aspiration incidence post-treatment, quality of life, length of hospital stay, or nutritional status. One review outcome, change in oral and pharyngeal secretion severity were not reported in any study.”
• “As the populations included in this review were predominantly acute stroke with a very small number from intensive care; the resulting dysphagia in these populations will have different underlying mechanisms of impairment limiting generalisability of findings.”
• “Intensive care patients, however, present with dysphagia for a myriad of different reasons..Their central swallowing network is disrupted due to the brain lesion, but the presence of a tracheostomy will also affect laryngeal sensory receptors necessary for safe swallowing, in the context of likely continuing skeletal muscle atrophy during their intensive care stay.”
• “Their central swallowing network is disrupted due to the brain lesion, but the presence of a tracheostomy will also affect laryngeal sensory receptors necessary for safe swallowing, in the context of likely continuing skeletal muscle atrophy during their intensive care stay.”

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Article Referenced: [FREE ACCESS]

Duncan, S., McAuley, D., Walshe, M., McGaughey, J., Anand, R., Fallis, R., & Blackwood, B. (2020). Interventions for oropharyngeal dysphagia in acute and critical care: a systematic review and meta-analysis. Intensive Care Medicine, 46(7), 1326-1338. doi: 10.1007/s00134-020-06126-y

Additional articles mentioned:

• McHorney, C., Martin-Harris, B., Robbins, J., & Rosenbek, J. (2006). Clinical Validity of the SWAL-QOL and SWAL-CARE Outcome Tools with Respect to Bolus Flow Measures. Dysphagia, 21(3), 141-148. doi: 10.1007/s00455-005-0026-9
• How to Distinguish Between Outcomes, Effectiveness and Efficacy Studies in Dysphagia Research. (2018). Retrieved 30 June 2020, from https://pubs.asha.org/doi/10.1044/sasd11.2.5
• Ranganathan, P., Aggarwal, R., & Pramesh, C. (2015). Common pitfalls in statistical analysis: Odds versus risk. Perspectives In Clinical Research, 6(4), 222. doi: 10.4103/2229-3485.167092