The "A-Word": Using the PAS scale to tell a story

This article was written with Dr. James Coyle PhD, CCC-SLP, BCS-S, ASHA Fellow.

Let's talk about the "A-Word" that often sends shivers down the spines of clinicians and patients alike: aspiration. For too long, the presence of aspiration on a swallow study has been treated as a scarlet letter, immediately labeling a patient as an "aspirator" and often leading to drastic, life-altering decisions like being made NPO and even requiring a feeding tube. The worst part? It’s often draconian and unnecessary, like recommending surgery for a papercut.

I've encountered this knee-jerk reaction countless times, and because of it, SLPs have developed somewhat of a reputation. You’ve probably heard the term “diet police” used before. To put this concept into context, think about this: I once worked with a doctor who refused to consult speech pathology because, and I quote, “I don’t want my patients to be NPO”. His understanding was that when we see a patient, we automatically recommend NPO, no matter what. This idea didn’t arise from an abyss. He had to have had enough experience with SLPs who “erred on the side of caution” and made his patients NPO when they probably didn’t need to be. This kind of fear-based practice isn't helpful, and it certainly isn't patient-centered.

So, let's clear the air and challenge some common misconceptions about aspiration and the tools we use to assess it.

Beyond the Label: Why "Aspirator" Doesn't Tell the Whole Story

First and foremost, we need to stop labeling patients simply as "aspirators". Our in-depth and comprehensive swallow studies should never be broken down to a pass or fail outcome or require a yes or no answer to the question, “So, did he aspirate?”. It's an oversimplification that fails to capture the complexity of an individual's swallowing function and their response to that aspiration. The risk of aspiration is one of many variables that should be assessed during an instrumental swallowing evaluation.

And we’ll come back to that, but for now I want to address how we are currently assessing aspiration risk and whether or not we are in fact doing it correctly. Yes, aspiration is only one variable, but it’s an important one. Let’s make sure we are assessing it properly before we get into making sense of it.

Rosenbek and colleagues developed a tool called The Penetration-Aspiration Scale (PAS). You’re probably familiar with it. The goal of the tool was to bring a method to the madness of examining aspiration risk and standardizing our judgments during the modified barium swallow study (MBSS). It’s become an SLP fan favorite and is one of the most common standardized measures used during instrumental studies today. And for good reason: It’s relatively simple to use, the criteria are clear, and it's easy to communicate from one professional to another. But… and you knew a ‘but’ was coming, didn’t you?. It might be commonly used, but it’s also commonly misused.

The Penetration-Aspiration Scale (PAS)

1. Material does not enter the airway.

2. Material enters the airway, remains above the vocal folds, and is ejected from the airway.

3. Material enters the airway, remains above the vocal folds, and is not ejected from the airway.

4. Material enters the airway, contacts the vocal folds, and is ejected from the airway.

5. Material enters the airway, contacts the vocal folds, and is not ejected from the airway.

6. Material enters the airway, passes below the vocal folds, and is ejected into the larynx or out of the airway.

7. Material enters the airway, passes below the vocal folds, and is not ejected from the trachea despite effort.

8. Material enters the airway, passes below the vocal folds, and no effort is made to eject.

What does the PAS do? In essence, it helps us identify the depth of material entering the airway, the presence of airway residue, and the patient's response to material in the airway. It's designed to describe patterns of airway protection. Okay, and just as importantly, what is it not designed to do? Characterize and label a patient. The PAS can be a powerful way to standardize an important measurement. But powerful tools can go in both directions. When misused, it can have unintended consequences.

Here are some concepts to think about when we are using the PAS that often get missed:

PAS scores are for describing, not for quantifying: The PAS scores are categories, representing descriptions of different patterns of airway protection that occur during a single swallow event, arranged from least (1) to most (8) severe. You can't average them like regular numbers because the distance between each score isn't the same, and because each score describes only what was observed during a single event. You can’t average oranges and tangerines. This point is important. The scores are a way to describe and communicate, and while they do include numbers, they’re not meant for quantifying.

Think about it this way: A patient who has a PAS of 1 for ten trials and then has one instance of gross, silent aspiration doesn’t have a mean PAS of 1.6. Instead, they produced nine "ones" and one "eight". That is their pattern of airway protection in a ten-swallow sample. Using means here would be inaccurate because, again, PAS might be a numerical scale, but it’s not an interval scale. That 1.6 does nothing to describe the patient’s swallow and aspiration risk. Means and modes are not the goal. Describing and communicating the story of the patient’s swallow is.

Provide more than the worst score: Arguably, all humans aspirate. You have, I have. We are all aspirators. Many clinicians provide the worst PAS score observed as a label to represent the patient’s aspiration risk. It’s not about the worst score or any one score for that matter, it’s about risk exposure and the big picture we are trying to paint. The individual events aren’t nearly as important as their patterns that provide a narrative of what is truly going on with the patient.

The Nuance of "Normal": Let’s continue with what’s “normal” for a minute. Healthy people penetrate quite frequently, especially as they age. Specifically, a PAS score of 2 (material enters the larynx, remains above the vocal folds, and is ejected) occurs in about 15-20% of liquid swallows, and aspiration may occur as well, albeit less frequently. This means that some level of airway invasion, when effectively cleared, can be a normal physiological event. One thing we know for sure, though, is that aspiration of any solid consistency is definitely an abnormal event and should not be overlooked.

Aspiration: A Risk Factor? Yes. The Deciding Factor? No.

But even in those patients who are aspirating with abnormal frequency, it should not be a one-way ticket to NPO Nation. This is crucial. We should not be making patients NPO solely based on the presence of aspiration. Aspiration may or may not cause harm to an individual, as it depends on a multitude of other factors, often referred to by Dr. James Coyle as "Host-risk and iatrogenic factors".

These risk factors include all other factors that form the individual’s predisposition to pneumonia, including comorbidities, their medical histories, functional limitations, pulmonary clearance status, immunological integrity, and the risk introduced by the treatment received (i.e., oral intubation). It's the combination of aspiration with these other factors that creates the recipe for adverse events like aspiration pneumonia. For instance, factors identified by Langmore and colleagues in 1998, such as dependence for feeding and oral care, poor oral health, as well as poor pulmonary clearance, chronic lung disease, and being immunocompromised, may significantly increase the risk when combined with aspiration.

What it really comes down to is choosing the right thing over the easy thing. It’s easy to identify aspiration, it’s easy to be scared of it, and it’s easy to recommend NPO. But that’s not what we do. We do what’s right. We assess and mitigate health risks. We don’t make knee-jerk decisions based on aspiration alone. Instead, we identify the occurrence and the risk and provide training and therapeutic approaches to minimize that risk.

When someone falls off their bike, we don’t take away the bike. We pick them up, teach them, guide them, support them, and help them to get back on that bike so they can ride again.

What’s the Swallowing Version of “Getting back on that bike?”

To understand the problem, we have to see it first. And sometimes that means creating an environment where the issue is likely to occur. What does this look like? Essentially, pushing the patient by encouraging them to drink and eat as they normally would during an instrumental swallowing evaluation. Taking bird bites and sipping water like it’s a glass of fine wine is not going to get us the information we need. We aren’t trying to harm the patient, of course; instead, we’re trying to do the opposite. Pushing the patient during a swallow study is meant to shine a light on something that’s already happening (whether it’s under fluoro or not). We do this to truly understand the how and the why of the aspiration, and how to prevent it. This is about strategically identifying the anatomical and physiological limitations that might be contributing to the issue. It’s why Dr. Bonnie Martin Harris asks her patients to “Drink like you're thirsty.”

We might intentionally try certain consistencies or volumes to increase the risk of aspiration, not with the intention of restricting those consistencies, but to observe the pattern, the depth, the residue, and the patient's response. This allows us to tailor behavioral interventions that target the how and why of aspiration. For example, say the patient aspirates secondary to delayed airway closure, but it only happens with a sufficient amount of volume. We see this on consecutive sips of thin, which is how the patient typically drinks. We can then talk to the patient about doing single sips instead of rapid drinking or assessing the efficacy of a chin tuck to allow the bolus to pool in the valleculae and improve adequate airway protection before the swallow. We work with the patient to determine what strategies or restrictions they are able and willing to follow and then test which ones actually work during the study.

Vocal Folds Run Deeper Than Meets the Eye

Understanding the anatomy is fundamental to accurate interpretation during the swallow study. Do you fully understand the anatomy you’re looking at? Don’t answer too quickly now. For example, we often think of the vocal folds as thin bands of tissue, which is what they look like on FEES. But that’s because we are only looking at their top surface. They’re actually taller than we realize with significant depth that we can’t appreciate during a swallow study. Dr. Coyle encourages us to picture them less as thin bands of tissue and more like a triangular tent with the whitish superior portion of the vocal folds as its top and the lower border of the cricoid cartilage as its floor. This anatomic framework separates the larynx (penetration) from the trachea (aspiration). When barium passes the visible line forming the floor of the larynx (cricoid), it has been aspirated, whether it is ejected or not afterwards. We must be clear that the trachea is the destination of aspirated material. This mental image can help you visualize how material interacts with them during a swallow.

For example, think of laryngeal penetration that makes its way down, deep to the level of the vocal folds. Even if it looks like it passes the surface, it may still be in an area where the larynx can easily push the material out of the laryngeal vestibule, without it falling into aspiration territory. So, don’t call it aspiration too soon. Give the patient a chance to clear their throat or cough. And if they don’t? Cue them to do so, but do not score as if the clearance was spontaneous or volitional – score it as if the patient did not respond (i.e., scores of 3, 5, 8).

Don’t Walk in Anyone’s Shadow

Is that dark shadow really part of the bolus, or could it be something else? Little black dots are often pixel phantoms or anatomic variants and not barium. Age-related skeletal changes alter what cartilages look like in x-rays. When we see a little black dot during a swallow study, are we certain it wasn’t part of the patient’s anatomy? Look at the baseline image before PO trials of contrast are introduced to be sure. This is because we fall victim to confirmation bias, assuming that every shadow in or around the airway is barium. But not all shadows are related to the bolus. It could be related to the density of the patient's cartilage, or it could be nothing more than an artifact. Maybe it’s even jewelry. The point is, you don’t know unless you check beforehand.

Beyond the Numbers

If you can take away one thing from this article, it should be that our goal is to tell the patient’s story, not just label them with a number on the PAS. While PAS scores are valuable shorthand for clinicians to quickly and objectively make a judgment, they don't belong in the patient's record as standalone figures. Why? Well, because other than dedicated SLPs with a focus on dysphagia management, nobody knows what the heck a 5 is. Don’t focus too much on the numbers, and instead describe what you see: The frequency and percentage of events, the depth of airway invasion, and the presence of airway residue.

For example: "Trace aspiration occurred with an ineffective, delayed spontaneous cough on three of five unmeasured cup sips of thin liquid, and one of three unmeasured straw sips, due to delayed pharyngeal trigger and delayed laryngeal vestibule closure, with contrast entering the airway before completion of the swallow". This narrative provides far more meaningful information and treatment targets than “PAS = 7”.

The PAS is a powerful tool in dysphagia diagnosis, providing good baselines and follow-up data, and improving communication among clinicians. It enhances the specificity of our judgments of airway protection. But remember, it's a tool to be combined with a full, comprehensive assessment, and it should never be used to categorize a patient. It's about empowering us to understand the why and how so that we can create more targeted interventions that ultimately enhance our patients' quality of life.

A big thanks to Dr. James Coyle PhD, CCC-SLP, BCS-S, ASHA Fellow for his help and support in writing this article. I was inspired to write this with him after taking his course on the topic, which you can find here. I hope you enjoy it as much as I did. Thanks for reading and if you liked this, please subscribe below to receive more articles just like it.