Co-author:Kristin King, PhD, CCC-SLP

Why swallowing?

Annually about 100,000 patients have medical events that require a tracheostomy with 24% necessitating mechanical ventilation (Mehta, Syeda, Wiener, and Walkey, 2015). It is estimated that 45% to 86% of patients with tracheostomy aspirate, and 83% of those who aspirate do so silently (Bergl, Kumar, Zane, Shah, Zellner, Taneja, … Nanchal, 2018). Speech-Language Pathology (SLP) is the primary discipline in most medical settings to evaluate swallow function for diet advancement or to provide dysphagia rehabilitation to work towards resumption or advancement of an oral diet. Having a solid understanding of the multitude of factors that can affect swallow function in this patient population with tracheostomies is critical to appropriate assessment and interventions. It also is essential to understand the role of the multidisciplinary team because the complexity of this patient population requires collaboration between disciplines (Alabdah and McGrath, 2018). 

The role of a tracheostomy team is increasingly recognized as vital to improve the quality of life and safety of care for the patient with a tracheostomy.  Additionally, tracheostomy teams can result in more timely referrals to speech language pathology.  This allows the SLP to provide early intervention which may include working toward restoration of airflow to the upper airway with cuff deflation, use of the PMV® [Passy Muir Valve] during mechanical ventilation, conduction of timely swallowing assessments, development of individualized treatment plans, and provision of early treatment for patients with tracheostomies.  This early involvement by SLP leads to faster return to oral intake and improved tolerance of oral diets, thus improving patient outcomes and quality of life (Bartow, 2020).

When patients are tracheostomy-dependent, assessment of their swallowing, establishment of a least restrictive diet, and identification of the appropriate interventions to improve swallowing function pose a more difficult challenge than with patients who have an intact system. Airway protection in these patients becomes highly dependent on reintegration of the upper aerodigestive tract, use of compensatory abilities, the medical status, and the integrity of the physiologic aspects of swallowing.  An understanding of these systems is an essential precursor to appreciating how they interplay and relate to swallowing safety in patients with tracheostomies. The complexity of this issue increases dependent on how the respiratory system and a tracheostomy with or without mechanical ventilation affects swallowing physiology. Understanding the normal swallow and then addressing the effects of a tracheostomy on swallow physiology enhances the ability to provide appropriate intervention. 

Review of normal swallowing

In an intact system, swallowing is a pressure-driven event requiring coordination of sensorimotor actions to transition the bolus from the oral cavity to the esophagus and prevent material from entering the airway. The act of swallowing is typically divided into the three phases: oral phase, which includes the oral preparatory phase and the oral transit phase, pharyngeal phase, and esophageal phase. Some clinicians also consider a fourth phase of swallowing known as the pre-oral or anticipatory stage of swallowing.  

The pre-oral phase initiates the process of swallowing and includes cognitive, auditory, visual, and olfactory input. Next, in the oral phase of swallowing, food is manipulated into a cohesive unit and the tongue begins anterior to posterior bolus propulsion. Sensory receptors in the oropharynx trigger the pharyngeal swallow which is a rapid sequential activity occurring within one second. The basic components of the pharyngeal swallow include:

  • Closure of velopharyngeal port
  • Elevation and anterior movement of the hyoid and larynx
  • Closure of the larynx and laryngeal vestibule 
    • True vocal fold adduction and cessation of respiration
    • False vocal fold contraction
    • Arytenoids tilt forward to contact the epiglottic base
    • Epiglottic inversion
  • Opening of the cricopharyngeal sphincter 
  • Base of tongue (BOT) retraction / pharyngeal wall contraction
  • Progressive top to bottom contraction in the pharyngeal constrictors

Lastly, the entry of the bolus through the upper esophageal sphincter initiates the esophageal phase of swallowing. A combination of esophageal peristalsis and gravity transitions the bolus through the esophagus and lower esophageal sphincter and into the stomach.

A pre-requisite for normal swallowing to occur is accurate coordination of breathing and swallowing. Breathing ceases for a brief apneic period during swallowing as physical closure of the airway occurs. This closure is mediated by both afferent (sensory) and efferent (motor) brainstem signals. This respiratory pause functions to protect the lungs from aspiration. An additional protective feature of deglutition is mid-expiratory swallowing. The mid-expiratory swallow requires a closed respiratory system and tight synchronization of breathing and swallowing. The post-swallow expiration serves as a protective mechanism to expel laryngeal vestibule penetration which may have occurred during swallowing and may prevent inhalation of residue in the pharynx after the swallow. 

A closed aerodigestive system also allows for normalized deglutitive pressures.  Normal swallowing pressures include contact pressure from pharyngeal structures, pressure changes as the bolus moves through the oral and pharyngeal cavity from regions of positive pressure to negative pressure, and subglottic airway pressure. The subglottic pressure theory asserts that lung volume and respiratory recoil combine to generate positive sub-glottic pressure. This pressure peaks during swallowing when the vocal folds are closed and stimulates mechanoreceptors in the larynx. The mechanoreceptors provide afferent input to the brainstem which modifies the efferent signal for swallowing, key to swallowing-breathing coordination during swallowing.

How a tracheostomy tube may impact normal swallowing

The presence of a tracheostomy tube may alter many of the sensorimotor actions described above. Research has indicated that there may be changes in smell and taste, reduced hyolaryngeal excursion, lack of subglottic air pressure, impaired breathing and swallowing coordination, reduced secretion management, increased penetration and aspiration, and cough function changes in patients with tracheostomy tubes. The physiologic and mechanical complications are even more pronounced with tracheostomy tubes that are open and have inflated cuffs.

Olfaction

Normal olfaction requires active airflow through the nose upon inhalation. Following a tracheostomy, most of the inhaled air goes in and out through the tracheostomy tube, bypassing the nasal cavity, resulting in a reduced sense of smell.  Since the sense of taste is causally related to the sense of smell, patients with impaired olfaction often experience dysgeusia. Tsikoudas, Barnes, and White (2011) investigated the impact of a tracheostomy on smell in head and neck cancer patients and reported that the group with tracheostomies identified a loss of smell and taste as their most significant symptom as compared and insignificant number in the control group (patients without tracheostomies).

Laryngeal elevation

Decreased laryngeal elevation due to the presence of a tracheostomy tube, especially with the cuff inflated, has been reported in several studies.  Amatheiu et al. (2012) studied the influence of tracheostomy tube cuff pressure on the swallowing reflex in tracheotomized patients.  They studied swallowing function at increasing cuff pressures and found that the swallowing reflex was progressively more difficult to elicit with increasing cuff pressure, and when activated, the resulting motor swallowing activity and efficiency of laryngeal elevation also were depressed with increasing cuff pressure.  Ding and Logemann (2005) studied swallow physiology in patients with a tracheostomy cuff inflated and deflated.  They found that reduced laryngeal elevation was significantly higher in the cuff-inflated condition as compared to the cuff-deflated condition. Jung et al. (2012) studied the effect of decannulation on laryngeal movement in patients with tracheostomy.  They reported that maximal hyoid bone movement and maximal laryngeal prominence just after decannulation were improved significantly compared when compared to just before decannulation. The authors suggested that the findings from their study may support the hypothesis that a tracheostomy tube may disturb hyoid bone and laryngeal movement during swallowing. Conversely, Terk, Leder, and Burrell (2007) reported that the tracheostomy tube did not significantly change hyoid bone and laryngeal movement.  However, a limitation of this study was that the participants had normal swallowing and were not assessed with the cuff fully inflated.  It may be that a tracheostomy tube impacts the biomechanics of swallowing in individuals with dysphagia or perhaps hyolaryngeal excursion may be diminished if swallowing is evaluated with full cuff inflation. 

Subglottic air pressure

Changes in subglottic air pressure in patients with open tracheostomy tubes has been reported.  Gross, Mahlmann, and Grayhack (2003) investigated the impact of subglottic pressure on swallowing physiology in patients with a tracheostomy tube. They compared the depth of laryngeal penetration, bolus speed, and duration of pharyngeal muscle contraction during the swallow in individuals with tracheostomy tubes while their tubes were open and closed. They found that when the Passy Muir® Valve was on, patients demonstrated lower penetration-aspiration scores, faster bolus transit time, and shorter pharyngeal muscle duration time. The authors concluded that their findings indicated that within the same patient with a tracheostomy, pharyngeal swallowing physiology was measurably different in the absence of airflow and subglottic air pressure, as seen with an open tracheostomy tube, as compared to the closed tube condition. The closed tracheostomy tube condition redirected airflow through the glottis and subglottic pressure increased.

Breathing-swallowing coordination and airway protection

Breathing and swallowing coordination may be impaired for patients with a tracheostomy since the typical breathing-swallowing pattern is to swallow mid-expiration to serve es as a protective mechanism. Prigent et al. (2011) studied the breathing-swallowing interaction in patients with tracheostomy tubes and found that the expiratory flow towards the upper airway after swallowing was negligible with an open tracheostomy tube. 

Airway protection also has been studied in patients with tracheostomy. Some researchers have shown that patients have less penetration and aspiration when the tracheostomy tube is occluded than when it is open (Suiter, Mccullough, and Powell, 2003; Gross et al. 2003).  Cuff status has also been examined and researchers have found that silent aspiration is more frequent when the tracheostomy cuff is inflated as compared to deflated (Ding and Logeman, 2005).  Ding and Logemann (2005) reported that an inflated cuff with a tracheostomy tube has been shown to block the expiratory air flow through the larynx which may desensitize the larynx and pharynx. They report that with this desensitization the patient may be unaware of aspiration and the protective cough mechanism, which may ordinarily clear the airway of foreign material, may be blunted. Ding and Logemann (2005) appear to support this theory by reporting a higher incidence of aspiration in patients with a tracheostomy tube that has an inflated cuff. 

Another study which examined aspiration in patients with tracheostomy was conducted by Leder (2002).  He studied the incidence of aspiration and type of aspiration (overt or silent) in patients with tracheostomies requiring mechanical ventilation.  He found that in 33% of patients requiring short-term mechanical ventilation via a new tracheotomy (within the previous 2 months) aspirated. He also reported that 82% of those patients who aspirated did so silently. These findings were attributed to multiple factors, including tracheostomy, age, co-morbidities, and respiratory status.

Summary

Researchers have found that the presence of a tracheostomy tube negatively impacts swallowing physiology. Skoretz, Riopelle, Wellman, and Dawson (2020) report that understanding the coexistence of dysphagia and tracheostomy in critical illness plays an essential role in optimizing assessment and treatment interventions, especially in the acute care setting. Research shows that both mechanical and physiologic complications associated with a tracheostomy, especially when it is open, and the cuff is inflated, can lead to disruptions in the safety and efficiency of the swallowing mechanism. However, research also has indicated that using a Passy Muir Valve to close the system with a deflated cuff restores airflow through the upper airway which improves sensation, taste and smell, pressures, and overall swallow function.  More research is needed to develop the evidence base even further.

References

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Amathieu, R., Sauvat, S., Reynaud, P., Slavov, V., Luis, D., Dinca, A., … Dhonneur, G. (2012). Influence of the cuff pressure on the swallowing reflex in tracheostomized intensive care unit patients. British Journal of Anaesthesia, 109(4), 578-583. doi:10.1093/bja/aes210

Barrow, C. (2020). Can a multidisciplinary trach team improve swallowing in patients with a tracheostomy? Dysphagia Café, retrieved from  https://dysphagiacafe.com/2020/07/25/can-a-multidisciplinary-trach-team-improve-swallowing-in-patients-with-a-tracheostomy/ 

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Mehta, A. B., Syeda, S. N., Wiener, R. S., & Walkey, A. J. (2015). Epidemiological trends in invasive mechanical venitaltion in the United States: A population-based study. Journal of Critical Care, 10(6), 1217 – 21.

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Skoretz, S., Riopelle, S., Wellman, L., & Dawson, C. (2020). Investigating swallowing and tracheostomy following critical illness: A scoping review. Critical Care Medicine, 48(2), 141-151. doi:10.1097/CCM.0000000000004098

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Terk, A., Leder, S., & Burrell, M. (2007). Hyoid bone and laryngeal movement dependent upon presence of a tracheotomy tube. Dysphagia, 22(2):89-93. 

Tsikoudas, A., Barnes, M., & White, P. (2011). The impact of tracheostomy on the nose. European Archives of Oto-Rhino-Laryngology, 268(7):1005-1008. doi:10.1007/s00405-011-1522-1

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