Outcomes of Oropharyngeal Dysphagia
The consequence of having oropharyngeal dysphagia may range from minor health consequences to death. This text will focus on issues associated with malnutrition and aspiration pneumonia.
Malnutrition
Malnutrition refers to the inability of an individual to receive adequate nutrients for needed body functions. The causes of malnutrition are varied. Common causes include a poor diet, perhaps due to an inadequate food supply or financial resources to purchase food, mental health issues that prevent a person from choosing or obtaining adequate nutrition, or dysphagia. Malnutrition may lead to weight loss, fatigue, and cognitive and physical impairment. Chronic malnutrition may result in greater than normal muscle loss as the body seeks to recover lost protein by breaking down muscle. Over time, malnutrition may lead to wasting syndrome (a.k.a. cachexia), failure to thrive, and frailty.
The presence of dysphagia increases the risk of malnutrition (Foley, Martin, Salter, & Teasell, 2009), particularly in the independent elderly population (Serra-Prat et al., 2011; Carrión et al., 2015). Treatment of dysphagia in individuals that are malnourished improves their nutritional status (Elmståhl, Bülow, Ekberg, Petersson, & Tegner, 1999).
Frailty
In adults, frailty can be a clinical sign of dysphagia or can result from long-standing dysphagia (van der Maarel-Wierink et al., 2011). Although definitions of frailty vary across sources, in general, it refers to increased vulnerability or a decline in functional reserve across multiple physical systems (Xue, 2011; Lee et al., 2014; Morley et al., 2013). Frail individuals are more vulnerable to environmental or physiologic stress. Therefore, frail individuals are more likely to have trouble with swallowing when new foods or textures are introduced. Further, when swallow deficits result in aspiration, frail individuals are more likely to have a negative response to even small amounts of aspiration.
Frailty is not always a direct result of reduced nutrition. It may result from changes in activity level. A sedentary lifestyle will reduce overall muscle function. Overtime, with continued decline in muscle function and aerobic activities, an individual may become frail.
Failure to thrive, a term that lacks a clear criteria in the aging population, may be used to define a frail individual or an individual with cachexia or muscle wasting syndrome. The terminology used in your facilty may vary by physician or cause of malnutriton. Although generally considered to be different, long term failure to thrive (malnutrition) and/or cachexia will result in frailty.
Clinical Note
As the term FAILURE to thrive may be misinterpreted by a parent or caregiver as an implication that they have not done their task, this term should be used with careful consideration.
Aspiration and Risk of Pneumonia
During swallowing, airway protection is the key aspect of a safe swallow. This happens in several ways: (1) the internal diameter of the larynx goes down to zero (closing the inside of the larynx), (2) the larynx, and therefore entrance to the airway, moves up and out of the way of the bolus flow, and (3) the size of the airway entrance is reduced (arytenoid approximation and tightening of aryepiglottic folds) and covered by the down-folding of the epiglottis. Deficits in any of these actions increases the risk of penetration or aspiration. If, during swallowing, airway protection mechanisms are either poorly timed or poorly functioning, there is a risk of penetration or aspiration of material into the larynx. Penetration is said to have occurred when material bypasses the laryngeal rim and enters the laryngeal vestibule. Penetration stays above the level of the true vocal folds and may be ejected or eliminated from the larynx, so that it cannot continue to travel below the vocal folds. It should be noted that penetration of material is not limited to food or liquid; oral secretions or extra-esophageal reflux can penetrate the laryngeal entrance.
Aspiration occurs when the penetrated material traverses the larynx and goes below the vocal folds. Like penetration, aspiration can occur on food or liquid being ingested, or on oral secretions and their bacterial content, refluxed or vomitus material complete with its high acid content, or foreign material such as a penny or a pencil eraser. The body’s reaction to aspiration can vary from inconsequential to severe. The specific response is a function of multiple variables, including the amount and chemical composition of the aspirated material, the depth of the aspirated material, the current health of the lungs, or the frailty of the individual. In the extreme, aspiration can result in pulmonary consequences leading to death. In fact, 44% of aspiration-related deaths are associated with dysphagia (Hu, Yi, & Ryu, 2015).
Clinical Note
Penetration and aspiration can be quantified through the use of the Penetration-Aspiration Scale (Rosenbek, Robbins, Roecker, Coyle & Woods, 1996) which is discussed in the evaluation section of this text.
When material from the pharynx enters into the larynx, the dysphagia clinician should take note of the depth of the invading material, the reaction of the system to the material, and the timing of the penetration with respect to the swallow. In a healthy individual, laryngeal penetration may occur, but will be redirected by the protective cough reflex, quickly and efficiently expelling the material from the airway entrance. Although a cough can be produced voluntarily, the reflexive cough is likely the most efficient at clearing penetration in a timely fashion. In individuals with swallow disorders, this cough may be weak or absent. A weak cough may render the individual unable to expel the foreign material.
Silent aspiration is said to have occurred when material goes below the vocal folds without any awareness or physiologic response from the individual. Across a variety of medical disorders including pediatric feeding, head and neck cancer, brain injury, stroke, dementia, and others, among patients who aspirate, the incidence of silent aspiration ranges from 14-89% with the highest incidence in the infant and elderly populations (Dusick, 2003; Eibling & Carrau, 2001; Garon, Sierzant, & Ormiston, 2009; Halvorsen, Moelleken, & Kearney, 2003; Keeling et al., 2007; Kendall, Leonard, & McKenzie, 2004; Leder & Espinosa, 2002; Mann, Hankey, & Cameron, 2000; Marik & Kaplan, 2003; Ramsey et al., 2005; Rosenbek, McCullough, & Wertz, 2004; Rosenthal, Lewin, & Eisbruch, 2006; Sakai et al., 2016; Schindler & Kelly, 2002; Simental & Carrau, 2004; Uhm, Yi, Chang, Cheon, & Kwon, 2013; Westergren, 2006; Yoshikawa et al., 2005). Common clinical correlates of silent aspiration include a history of aspiration pneumonia, an absent cough, or changes in vocal quality associated with mealtimes. Chronic congestion, chronic low-grade fever, reduced oxygen saturation, and an elevated white blood count may also be associated with silent aspiration. The likely culprit in silent aspiration is reduced sensory function in the laryngeal region. Notably, at times the patient who exhibits silent aspiration on a small bolus, may exhibit a cough when a larger volume is used (Leder, Suiter, & Green, 2011). Regardless, repeated aspiration events associated with mealtimes is a sign of dysphagia.
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When reviewing results from chest x-ray consider the location of the infiltrates. Aspiration pneumonia is likely to have infiltrates in the right lower lobe. When infiltrates are noted in the left lower lobe, atelectasis is considered. Bilateral infiltrates are more often associated with a viral infection.
Timing of Aspiration Associated with Swallowing
In order to better understand the offending physiology associated with aspiration, timing of the aspiration events should be identified with respect to the pharyngeal swallow — before, during, or after the swallow trigger. If anatomy is intact, observation of the timing of the event, provides evidence of the physiologic swallow deficit. When the event occurs before the initiation (trigger) of the pharyngeal swallow, which is common in patients with neurologic causes or oral dysfunction, the culprit is either oral bolus control or a delayed swallow trigger. Poor bolus control or poor posterior containment of the oral bolus may result in premature spillage of material into the pharynx before the pharynx is prepared to trigger a swallow response. Thus, the material enters the pharynx prior to the initiation of airway protection and the bolus has easy access to the laryngeal entrance.
It is possible to have aspiration before the swallow with intact oral bolus control. In this scenario, upon bolus transport to the pharynx, the swallow is not trigger in a timely fashion. This delayed or absent trigger allows the bolus to wait in the pharynx prior to the initiation of any airway protection. If the bolus is small and the vallecula pocket can house the bolus, the airway may be temporarily protected. However, if the bolus is large or the vallecula cannot halt or house the bolus flow, the bolus may enter the larynx before the swallow is triggered.
If the bolus is propelled into the pharynx and there is a timely swallow trigger but aspiration occurs during the pharyngeal swallow, reduced glottal valving should be suspected. There are multiple levels of redundancy in airway closure during the swallow. When laryngeal penetration is observed, the adequacy of each level of redundancy should be evaluated with respect to either anatomy, physiology, or timing. However, as the true vocal folds are the last gate before the bolus enters the trachea, only deficits of this region (poorly-timed or poorly-valved glottis) can result in aspiration during the swallow. In other words, if the vocal folds close during the swallow, then inadequate function of other valves will result in penetration during the swallow, but not aspiration.
It is possible to have an intact glottal valve which dysfunctions in timing only. Recall that adequate airflow is essential for oxygenation, and therefore the vocal folds will remain open for the required time while the larynx elevates. If oxygenation is poor, then glottal closure may be altered during the swallow. Specifically, the onset of glottal closure may be delayed and the duration of swallow-related respiratory cessation may be shortened. The end result may be aspiration during the swallow due to the late onset or shortened duration of glottal closure.
Once the pharyngeal swallow is completed (i.e., the larynx has descended and the UES is closed) penetration or aspiration can occur on any material left in the oropharynx. This material can be pooled in various locations and when the larynx returns back to its role as airway, pooled material can easily be diverted into the larynx. If the pharynx is free of residue after the swallow, it is still possible to have penetration or aspiration after the swallow if extra-esophageal reflux occurs. That is, if the reflux penetrates the UES into the pharynx, it is possible that the acid-laden contents may spill over into the larynx.
Risks of Aspiration
Chronic aspiration, or even minimal aspiration in patients with lung disease, may lead to illness. In fact, respiratory infection rates are increased in individuals with oropharyngeal dysphagia (Serra-Prat et al., 2011). Aspiration of food and liquid can lead to aspiration pneumonia; aspiration of extra-esophageal reflux (i.e., gastric content) can result in aspiration pneumonitis. Pneumonia occurs when there is an infectious reaction to the aspiration of oral or nasal secretions, or food and liquid. Pneumonitis occurs when there is aspiration of gastric content (reflux). Variables on whether or not aspiration will lead to a bacterial pneumonia include: oral health, lung health, overall health and activity level of the individual, chemical composition of the aspirated material, the frequency and amount of aspirated material, and the depth of this aspiration. Other signs, such as general malaise or a low-grade fever, may accompany chronic aspiration. Pneumonia or pneumonitis may be suspected when an elevated white blood count is noted, and because a chest x-ray will likely show localized infiltrates, aspiration pneumonia can be verified by a physician. In the sedentary individual, the right lower lobe is more likely to contain dense infiltrates due to the slope of the right bronchi.
Risk of aspiration is not allayed with the use of alternate feeding approaches. NPO status (nil per os, meaning nothing through the mouth) with G tube and NG tube feedings have both been shown to increase the risk of extra-esophageal reflux (Opilla, 2003). A continuous drip may have less risk of aspiration than syringe bulb feeding (Metheny, 2002). As noted above, the risk of aspiration pneumonia is increased with poor oral care when chronic microaspiration occurs. Supine position is also associated with increased incidence of aspiration (Ibáñez et al., 2000; Torres et al., 1992).