Oh no! Should I just go with the High Flow?

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Title: Initiation of Oral Intake in Patients Using High-Flow Nasal Cannula: A Retrospective Analysis
Authors: Flores, Eng, Gerrity, & Sinha
Journal: Perspectives of the ASHA Special Interest Groups Vol. 4 No. 3
Year of Publication: 2019
Design Type: Retrospective study
Purpose: “This retrospective analysis puts forth clinically relevant observations from a patient population on HFNC and considerations in clinical decision making about initiation of safe oral alimentation.”
Population: inpatients admitted requiring HFNC and MBSS
Inclusion criteria: single hospital admit between 2015-2018; MBSS completed while wearing HFNC
Exclusion criteria: none explicitly stated

  • Only got a sec?
    • HFNC shouldn’t be an automatic disqualifier for PO initiation or instrumentation. Additional factors can be highly critical as well
  • Only got a minute?
    • “This retrospective analysis supports previous research that the sole need for HFNC should not be a barrier to a patient’s oral intake.”
    • “When making decisions regarding oral intake for these patients, additional focus should be placed on the patient’s overall clinical condition, including, but not limited to, their cognitive status, physical abilities, and swallowing impairments objectively defined by an MBSS.”
    • “This high number of patients started on oral intake underscores the importance of instrumental evaluation for objective assessment of swallow physiology, especially in compromised patients whose clinical characteristics (active pulmonary infection, presence of HFNC) suggest impaired airway protection.”
    • “The clinical bedside evaluation, although clinically informative, is insufficient alone to discern a patient’s readiness for oral alimentation while on HFNC therapy. Once a patient is medically stable for an MBSS, the instrumental assessment should be completed promptly to avoid malnutrition and muscle wasting.”
    • “While SLPs should continue to be cautious of the impact of HFNC due to concerns for silent aspiration and should continue to monitor patients closely, it is just one of many factors that should be considered in decision making for oral diet initiation.”
  • Got more time? Keep reading!!

As we move into 2020, we may have a lot of expectations. From flying cars (as promised in The Fifth Element!), smart houses you can control with just a touch of a button, to opening our cars with only using our faces/eyes. One might even fantasize about finally receiving their X-ray vision goggles for clinical bedside examinations🧐. Can we look forward to lots of new knowledge, technology, and insights in the coming year? ABSOLUTELY!! That’s the mind-blowing part of our ever-evolving field! Will we ever rely on something to easily tell us what to do (like all those Buzzfeed quizzes I might brainlessly do)? To that, you’ll no doubt appropriately hear, “Don’t hold your breath.

While doctors are learning more and more about the body-brain-gut connections, us SLPs continue to learn more about the breathing-swallowing connection (among many other things).

One of these relationships that will likely continue to be in the ‘hot seat’ is using high-flow oxygen to improve acute respiratory compromise, while also simultaneously impacting the biomechanics of the swallowing system.

The article’s abstract pretty much lays it all out there for you:

“Because the effects of HFNC on swallowing are unclear, speech-language pathologists lack the research to support evidence-based clinical decision making.” p.522

surprise fries.PNG



Just like the feeling of finding “surprise fries” at the bottom of a to-go bag, this article really can give more insight than you might have assumed!

Whether you’re either trying to remember the few slides in anatomy or swallowing course (if you had one!) or just wanting to know what roles these 2 teams play, a spectaular list of references is immediately made available to you in the very first paragraph. This list will basically layout the whole “stuck-together-like-glue” respiratory-deglutitive relationship (why not treat it like a Hallmark marathon by inhaling your beverage/snack of choice to truly “veg” out on this topic🤓).

A brief refresher of just what high-flow nasal cannula (HFNC) is/isn’t and does/doesn’t do can help avoiding feeling like overwhelmingly overwhelmed.

info overload.PNG

“High-flow nasal cannula (HFNC) is a form of respiratory support used in the acute care setting to treat patients in acute respiratory distress. It has proved to have physiological benefit in critically ill populations by delivering compressed air and humidification at high flow rates and is increasingly common in the intensive care unit settings” p.522

For a more in depth explanation of HFNC with swallowing, I’d definitely recommend checking out the [FREE ACCESS] article by Coghlan & Skoretz (2017)  where scouts honor I know you’ll learn something.🤓

So far, past research findings with healthy and impaired populations have shown:

  • reduced swallow latency with HFNC and high flow rates
  • HFNC≠NPO, but is a factor to consider
  • 40 and 50 lpm (liters per minute) resulted in overt swallowing changes in timing

Fast forward to this article…

The authors’ hypothesis aligns closely with other studies that have tried to look at this high-flow phenomenon, where a+b may not always = c (see Reference list in article).

triple dog dare

Since HFNC is frequently used in acute/ICU related settings, I double-dog-dare you to NOT find a patient in their demographics Table 1 that does not mirror a patient you may have seen in this setting. From 44 years old, COPD exacerbations and cardiopulmonary complications to 92 years young or acute asthma aggravation, this population is similar in their level of (in)stability and critical medical necessity, yet can be as different as a pizza from a kumquat when it comes to not only why they’re being admitted, but also additional past medical issues, lifestyle, age, and genetics. Needless to say, the patients they acually rounded up makes it super easy for me to picture working with any of the participants on any given work day.

In the spirit of the season’s holiday cheer, the bright side of some metrics used in the study were comforting in that they were well-established and evidence-based such as MBSImP protocol (Modified Barium Swallow Impairment Profile) with scoring guidelines, PAS (Penetration-Aspiration Scale) scores, and FOIS scores (Functional Oral Intake Scale). Because these metrics had evidence behind them more strength was added to what and how they were measuring variables versus going at it on a whim. Even though it’s a bit more informal and clinically subjective, they also chose to consider cognitive status as well as ambulation abilities, much like we do in the #REALWORLD.

Let’s ponder on that last thought for just another minute and utilize those visual imagery tools we so often coach our patients in to visualize our typical workday:

  • Do we use at least some form of diagnostic, standardized, evidence-based criteria to evaluate swallow physiology and aspiration/penetration? — Yes!👍 (Hopefully! whether it be a screening tool or full-on comprehensive scoring😉)
  • Do we clinicaly consider a patient’s alertness and ability to follow simple directions with us or remember simple information?  — Yes!👍👍
  • Do we consider how physically active a patient is and/or how much assistance they might need to walk safely by talking with our colleagues in PT/OT? — YES!!👍👍👍

So far, this article is making me feel I’m having the revelation in Parent Trap with all these similarities!

parent trap

Since the authors were looking at earlier documented data and charts, there’s no way to know exactly how things happened, but–the patients involved completed MBSS using the MBSImP protocol following consensus from daily rounding with the medical team  (physicians, nurses, respiratory therapists, dieticians, therapy). There may be a critic or 2 in the back saying “Not so fast, they changed the MBSImP administration protocol during MBSS!!”  Yes, that is correct— due to what the authors claimed, “patient fragility” and/or  “high concern for aspiration risk,” because hopefully none of us are letting someone chug radiographic material straight into their lungs…

Do we do all this on the daily to make sure we are staying on top of our patients’ statuses, progress, and provide safe, quality care as a medical professional? 

oprah YASS

While life doesn’t yet mirror a Jetsons-like future with flying cars and we haven’t yet discovered a more objective way for SLPs to measure “diet tolerance” other than communicating with nursing, re-assessing, and watching every chest X-ray with our scanning eyes for any sign of trouble👀, the authors’ methods for judging ‘safe’ oral intake after starting any type of diet felt similar and appropriate enough for me.🤷‍♀️

Since there was no control group for any type of comparison, the type of data they provide are simply describing what they saw, with no definitive “if this, then that” or “x because of y” conclusions. They didn’t have a fancy formula, algorithm, or flow chart to tell them when a patient would get an MBSS, just like we don’t have one in #reallife. Based off what happened, what they were looking at, they could only come up with what they assumed may be some supporting actors for their results.

Okay. I can’t keep my inner research nerd hidden for any longer….


Table 1 was pretty neat in my little eyes🤓. Easy to read, easy to scan, easy to understand. I’d bet it could definitely be a great conversation starter for any Speech Department Journal Club since it felt like one of those old “I Spy” books where you constantly find something new given all their data on a single page.

The chart can also help reveal which subjects, with what admitting and additional medical factors did best on which diet recommendations with what percentage of FiO2 and flow rate, while comparing what pre/post FOIS levels, cognitive status, and how much they could ambulate with assistance. Basically, how all these separate factors impacted each other one by one or when thrown all together. Oh, and also comparing pre-MBSS diet recommendations to post-MBSS diet recommendations. All in all, this is typically what we’re looking for in our patients’ progress and all the factors we consider, right? We’re asking things like, ‘Why were they admitted?’ ‘How alert are they?’ ‘Are they able to get up at all?’ ‘Who may benefit versus who may not?’

That was a mouth full to get out and digest, so here’s the gist of some clinical observations they witnessed:

Based on bedside presentation, nine of nine patients were kept nil per os with an FOIS score of 1. The remaining one patient received an MBSS in lieu of a bedside evaluation and was started on an oral diet.” (my emphasis added)

After the MBSS, nine of 10 patients (90%) were resumed on a complete oral diet (i.e., a solid and liquid component) per SLP recommendations, with a score of 4–6 on the FOIS. (my emphasis added)

“One of the 10 was cleared for a pureed diet only; no liquids were recommended, and intravenous hydration was continued.”

“While all 10 patients resumed oral intake, eight of 10 were placed on dysphagia diets, and seven of those eight required liquid modifications (i.e., nectar-thickened liquids, honey-thickened liquids, or no liquids with intravenous hydration)” p.525

^👆THIS👆 ^ .

THIS is what “direct visualization through instrumentation” means.

THIS is what people mean when they say ‘I can’t be sure if they’re safe or not for an oral diet just from watching at bedside.

THIS is also the difference between recommending thickened liquids/modified diets in an ACUTE context compared to a less-critical or more long-term context.

Even if it is only 10 people, I believe it’s still enough to easily recognize how similar those 10 patients are to those patients we see every single day, in the nearly identical environments and situations. Not only did initial recommendations after a bedside swallow evaluation (without x-ray vision) change after an actual MBSS (go figure?), but some of the recommendations for modified diets were actually appropriate in this ACUTE setting, and by far better than an NPO guess/death-sentence!

THIS is where other environments such as inpatient rehabilitation, skilled nursing facilities and/or home/outpatient therapy may take the baton and continue to work on what is necessary after the acute needs have decreased. Do any of us want to recommend modified diets? I surely hope not. But I do believe it is important to remember that sometimes having an all-encompassing “Oh, I NEVER do this/that” mindset without having the evidence to back it up, forgetting about when these modified recommendations may actually be necessary and appropriate for this short-term route, and/or take patient desires into account, could be the difference between a HFNC patient taking a sip of thickened apple juice or getting a desert mouth with shrinking weaker muscles.😬

“Given the limited sample size of the study, conclusions could not be drawn between age, FiO2, flow rate, supplemental oxygen needs, PAS scores, MBSImP component scores, and diet recommendations.” p.525


I know, I know. Sorry, the article’s not going to be your ‘shining shield’ to whip out and make everything sugar plums and gumdrops. BUT, by looking at the chart, you can slowly put together some similarities and start to understand what the authors were seeing:

“It is notable that the four patients who were prescribed the most liberal diets (i.e., diets that involved a thin liquid component) were also cognitively appropriate, and three of those four patients were ambulating independently or at the supervised level.”

“In contrast, four patients (Patients 1, 4, 6, and 7) were deemed cognitively impaired and were also limited in their mobility status. These four patients were placed on more restrictive diets (i.e., modified diets), and all these patients also met the parameters for diet tolerance.”

“We hypothesize that lower acuity patients can compensate more effectively by using strategies while swallowing to reduce aspiration risk and also by ambulating to improve pulmonary health; higher acuity patients, then, who have more pronounced cognitive and physical impairments require a more conservative approach to diet recommendation.” p. 526

Is it just me, or has anyone else been sensing a theme over the past decade(s) of research? There are just NO clear-cut decisions for the complexity of swallowing! Strangely, being someone who math has never came natural to, my brain can’t help but compare these “new-age” concepts to simple equations, where 1+1=2. Bada-bing Bada-boom.

But in real life, the equations may often look much more like….. algebra.

Where it’s going to take us a lot more steps and have to figure out more things in order to ‘get to the right answer’ (and even then it may not be perfectly pretty!).

The authors also note that 5 out of the 10 patients presented with silent penetration/aspiration during MBSS, and 4 out of those 5 had no real reason to explain for it (e.g. neurological, laryngeal injuries). They took a huge leap and further hypothesized something that may leave others lying awake at night wondering🤔:

“We query whether continuous positive airway pressure from HFNC has a desensitization effect on peripheral afferent function or an inhibitory effect at the level of the central nervous system… Another contributing factor to silent aspiration is reduced integrity of the cough reflex. It is possible that the patients in this study had pulmonary compromise such that their motoric ability to generate a protective cough against the positive pressure of the HFNC was dampened.” p.526


Stepping away from the authors’ clinical findings, there’s more then plenty of obvious reasons why you can’t just rely on this article (YET!) given all the study’s limitations:

  • retrospective (no control over what happens/how things go)
  • all subjects only at 1 facility (can’t generalize)
  • small sample size (can’t generalize to whole populations from just a few people)
  • heterogenous population (hard to pinpoint)
  • modified standardized protocols (decreased validity)
  • subjective judgment even for objective procedures (x-rays, O2)
  • no control group (can’t compare to know if anything is actually important/statistically significant/worthy)
  • confirmation bias towards impairment

I’d be interested if any studies can overcome at least some of these limitations, since we’re so desperately craving more answers to our never-ending questions (another commonality between clinicians+researchers😉). Maybe a new year’s resolution can be to find similarly-matched subjects to compare swallowing impairments with HFNC while ensuring there’s better reliability for swallowing measures. This may take us into the distant future, but maybe we’ll have our flying cars and personalized x-ray swallow-goggles by then.🤩

Until then, we’ll all have to settle on the holistic, patient-centered care even Leder himself prescribes (another great read!), and remember not to run away when the flow gets too high.

“These findings indicate that the mere presence ofHFNC should not preclude oral intake. Rather, the presence of HFNC necessitates further objective evaluation to inform diet recommendations and guide the patient’s treatment plan. These conclusions are consistent with the findings of Leder et al. (2016): “it is not the use of HFO2-NC per se but rather patient-specific determinants of feeding readiness and underlying medical conditions that impact decisions for oral alimentation” (p. 159).”  p.525

How can you use this article?!?

  • Does your hospital have a specific protocol for evaluating swallowing with HFNC?
  • What other evidence have you used to guide your clinical practice?
  • What are some other clinical indications/contraindications for evaluating swallowing with HFNC that you’ve noticed yourself?

Article Referenced: [ASHA FREE ACCESS]

Flores, M. J., Eng, K., Gerrity, E., & Sinha, N. (2019). Initiation of Oral Intake in Patients Using High-Flow Nasal Cannula: A Retrospective Analysis. Perspectives of the ASHA Special Interest Groups4(3), 522–531. doi: 10.1044/2019_pers-sig13-2018-0019

****UPDATE ALERT: The authors have more recent publication for HFNC+Normal Swallowing! (SPOILER: looks like Cognition is KEY for compensation😯!!)

********2nd UPDATE ALERT!!!!:

Check this our for the most recent article on HFNC and LVC for Healthy Normal Adults!!😮🤯

Allen, K., & Galek, K. (2020). The Influence of Airflow Via High-Flow Nasal Cannula on Duration of Laryngeal Vestibule Closure. Dysphagia. doi: 10.1007/s00455-020-10193-0

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