ICU-Acquired Swallowing Disorders

Every month a group of #SLPeeps blogs about research. You can find out more about it here.

My last post for Research Tuesday was about cognitive dysfunction in ICU patients. That post emphasized some long-term effects of severe illness. This post will shift gears and focus on something more short-term: swallowing dysfunction resulting from ICU-level illness. Though the article I chose isn't itself a research article, it is a nice overview of swallowing and the role of SLPs in intensive care units. Also, the article was published in a medical journal, which is an exciting place for SLPs to get exposure and to hopefully increase awareness of how we can be assets to patient care.

What I enjoyed most about the article was how well the authors broke down different reasons why patients might have swallowing difficulty. There was also a nice overview of swallowing physiology, despite the authors' use of the cringe-worthy term swallow reflex.

The Numbers

The article shared some interesting numbers regarding ICU patients.

• There are over 700,000 patients who develop acute respiratory failure requiring mechanical ventilation in the US.
• Of those, over 400,000 patients survive to be extubated. (There's a 35% mortality rate.)
• A "significant portion" of those 400,000 patients have post-extubation swallowing dysfunction. Why no proper estimate? The article cites the wide variety of diagnoses that accompany swallowing dysfunction, in addition to the likelihood that many cases are overlooked. The "guesstimate" they offer, taking into account biases and heterogenous patient populations? Something between 3% and 62% of patients recovering from critical illness have swallowing dysfunction.

Mechanisms of Swallowing Dysfunction

I like that the article uses the term "ICU-acquired" as a general term; I find it helpful because it frees one up to the idea that swallowing dysfunction is complex, and can occur for a variety of reasons. The authors go further to describe "postextubation dysphagia (PED)", which is exactly what it sounds like. From a critical care standpoint, the others describe six different mechanisms in which ICU patients can develop swallowing dysfunction.

1. Endotracheal tubes and tracheostomy tubes. These can can cause trauma to normal anatomic structures. Ulceration can develop from the constant contact of a tube with various structures, including the vocal folds, the arytenoids, the epiglottis, and the base of the tongue. Chronic inflammation can lead to granulation tissue and potentially to scarring. There are implications for swallowing function as well as respiratory function. Commonly, there is concern for vocal fold paresis or paralysis following intubation. The authors note that "the recurrent laryngeal nerve can be copressed (usually by the endotracheal tube cuff)" (2398).
2. Neuromyopathy resulting in muscle weakness. Classic "use it or lose it". This can result from both prolonged intubation as well as the use of paralytics. Longer intubation time means not only weaker lungs, but weaker muscles along the entire aerodigestive tract.
3. Dysfunctional oropharyngeal and laryngeal sensation. This can result from polyneuropathy (reduced nerve function) or local edema. In either case, afferent input is reduced.
4. Impaired sensorium. Call it what you like: altered mental status, confusion, or delirium. The cause can range from the illness itself, infections peripheral to the illness, or even heavy sedatives. As SLPs from every setting can attest, the ability to participate is one of our #1 needs for effective intervention. Interestingly, I've found in my own experience that this concept is possibly the hardest; many times, I've assessed patients who I'm told "swallow fine" who present with significant amounts of food pocketed in their cheeks or caked on the palate. Sometimes we have to advocate not only from the "aspiration risk" perspective, but also from the perspective of adequate nutrition. What helps here? An interdisciplinary team approach. Dietitians can be an SLP's best friend, especially in an ICU.
5. Gastroesphageal reflux. ICU patients are commonly on prophylactic medication for reflux. Why is that? The authors note that reflux is a concern during intubation in addition to after extubation. They cite three reasons for this: (a) supine positioning, (b), higher levels of sedation, and (c) the use of paralytics. Gastric motility is commonly impacted. Some ICUs prefer to have feeding tubes placed post-pyloric in order to reduce the potential for reflux (the thought being that there are two valves, the pyloris and the lower esophageal sphincter, and two valves can protect better than one). However, the presence of a feeding tube alone puts one at increased risk for reflux.
6. Dyssyncronous breathing and swallowing. We don't think of it this way enough, especially when it comes to patient and family education, but swallowing is an act of fine-tuned coordination. I love the recent trend for describing the aerodigestive tract, because it's the most apt for describing how closely linked breathing and swallowing really are. Though the authors describe the imporantance of the coordination of the "apneic" period and its role for aspiration prevention, I wish they had gone further. I've noticed that tachypnea (rapid breathing) impacts the oral preparatory phase as well (specifically, bolus preparation and cohesion); patients who are struggling to breathe have a tendency to try to take in more air, and in doing so may be opening their mouth more than usual when breathing. We're taught from a young age to chew with our mouths closed, but it does serve a purpose: to better control a bolus, for one, and to act as the first pressure point in a series of pressure-driven events that is the swallow. If we think of reserve lung volume, it makes sense that we can manage to breathe gently through our noses while chewing; a patient who is critically ill likely does not have this same reserve volume, so this process requires considerably more effort, which leads to something else: fatigue.

Risk Factors and Screening

The usual suspects are mentioned, such as neurological injury and neuromuscular disease. The authors note the use of screening tools for dysphagia among stroke patients. Stroke protocols today require screening stroke patients for potential swallowing dysfunction. The authors note that there is no similar requirement for critically ill patients, but 41% of hospitals surveyed did, in fact, have routine screens established. Though I'm not sure if my own hospital was part of that survey, I am pleased to be part of an institution which has taken up more universal screening. Though the department I work in is nicely staffed, it would be impossible for us to see every patient admitted. I work a lot in the ICU, though, and have found that the added bonus to seeing more patients who present with some level of dysphagia is that I can also assess for cognition. I consider this a bonus because mild cognitive impairment is often so easily overlooked.

Clinical Dysphagia Evaluation (CDE) vs. Diagnostic

The authors describe clinical, videofluoroscopic, and endoscopic evaluations of swallowing. When it comes to ICU patients, the clinical dysphagia evaluation is typically my go-to. I like it because I can take my time to meet patients, get a sense for their cognitive status, and also see how they perform with real foods (not to mention it's much easier to push their limits and assess for fatigue). There are some patients with histories that clearly indicate the need for more objective assessments, but for most patients a clinical exam is sufficient to get started.

There's a fine balance, especially for ICU patients, given that the acute nature is such that they can make gains with just as much speed as they can decline. It's a balancing act, really, and requires persistent follow-up to see if any change, either progressive or regressive, is occurring. My initial and early subsequent follow-ups look closely at whether a patient may need an instrumental exam. Challenges for attaining such exams can include medical status (is the patient stable enough to leave the ICU, or to tolerate an endoscopic procerdure?), acuity of illness (do we expect them to make a quick or slow recovery?), and scheduling (always a challenge for videofluoroscopic studies). Sometimes, the passage of time is a key component both in terms of patient recovery and discerning need for further evaluation.

Treatment

The authors note that "treatments for all types of dysphagia have been relatively underexplored, especially for patients recovering from critical illnesses" (2401). Currently, we (a) modify diet textures, (b) modify posture (a la chin tuck or head turn), (c) use therapeutic exercises, and (d) use enteral feeding tubes. Varying success has been ascribed to each method, and the use of each varies among clinicians and institutions.

As I've reflected on my own practice with critically ill patients, I've found I use a combination of the above. Each has its own merits and drawbacks.

• Texture modification. I like to think of texture modification as a "band-aid" solution. It's a nice temporary tool but not always sustainable in the long-term. I find texture modification most useful for issues with dentition as well as attention; maybe a patient can't sustain enough attention to really masticate well, but have no problem with a liquids, pudding or puree textures. Maybe a patient has sustained a physical injury which cannot handle pressure on the mandible or palate. Maybe a patient left their dentures at home.
• Postural modifications. I feel similarly to postural modifications as I do to texture modifications. Maybe a chin tuck or head turn works great for my immediate safety, but I don't want to do that forever. There's a reason they're called compensatory strategies. The goal is to compensate well enough until more long-lasting change can be achieved.
• Therapeutic exercises. I tend to use these sparingly, but largely because critical illness generally doesn't lend itself well to such pursuits. Rather, I find them useful once patients are medically stable. In my case, medical stability usually means transfer to rehab. That said, my current caseload consists mostly of pulmonary patients, so I do end up coordinating with respiratory therapists to ensure breathing exercises are incorporated daily. I work with patients on these exercises and apply them to speech (increasing vocal intensity and duration of exhale for longer utterances, for example) as well as swallowing (improving reserve and breath control and practicing with PO trials).
• Enteral feeding tubes. I have been fortunate to work closely with many excellent dietitians. For critically ill patients, nutrition plays an integral role in recovery, and quite often patients are unable to consume adequate nutrition in the early stages of recovery. In patients who are extubated but remain severely altered, the risk might be that they're too agitated to really eat well. In patients who are extubated and retain high oxygen requirements, they may not be able to even coordinate their breath well enough to swallow; they also, quite often, run the risk of re-intubation.

Where to next?

Though this article did not describe any really new information, I found it to be very descriptive of the SLP's role with critical care patients, and a great introduction for providers of all backgrounds. I also loved how much it helped me think about not only what I do, but why I do it. I'm left wondering if my current approach is the best approach, or if there are other ways I may approach things to continually improve the services I provide. I like to think the answer to that is a resounding yes.

Article Citation

Macht, Madison, MD, Wimbish, Tim, MS, CCC-SLP, Bodine, Cathy, PhD, CCC-SLP, and Moss, Marc, MD. (October 2013.) ICU-Acquired Swallowing Disorders. Critical Care Medicine, vol. 41, #10, 2396-2405.