Swallowing is a basic function that most take for granted.
However, what seems so simple and automatic is actually a “complex mechanism of amazing efficiency” (Wijting &
Freed, p.10) Muscles and joints work in a concerted effort to safely move food and liquid from the mouth to the stomach.
With amazing coordination, food and liquid – or “bolus” – is transported through 3 basic phases of
the swallow: the oral phase; the pharyngeal phase; and the esophageal phase. Any one of these phases may be affected by diseases
and/or other conditions such as strokes, brain injuries and neuromuscular disorders. The result is dysphagia – a disorder
of swallowing that may occur anywhere from the mouth to the stomach (Brindle, 2006, p.1). In order to understand swallowing
disorders and develop an appropriate therapy plan for an individual with impaired swallowing, we must first understand the
phases of the normal swallow (Dr. Aviv, 2006, P. 1).
The purpose of this article is to provide an overview of
the 3 phases.
1. The Oral phase: This phase is also
referred to as the Preparatory phase as this is when the bolus (food or liquid) is prepared for the swallow. This phase is
volitional and begins when food is placed in the mouth. As simple as this sounds, it involves the ability to recognize
food; bring it to the mouth; and to attain adequate lip closure around the utensil, straw, or cup. During this phase, the
airway remains open and nasal breathing continues. Once the bolus is in the mouth, the bolus is then chewed (if needed), mixed
with saliva, and manipulated in preparation to propel it to the pharynx. This is achieved as the musculature of the
lips and cheeks contract followed by the contraction of the tongue against the hard palate in an anterior to posterior motion,
sometimes referred to as the tongues “plunger” or “propulsive” action (Wijting & Freed, p.12).
Once the tongue forces the bolus into the pharynx (past the faucial arches), the swallowing reflex is initiated and the pharyngeal
phase begins. The duration of the oral phase is variable, but in healthy individuals it is typically completed in 1 second
(Aviv, website).
2. The Pharyngeal phase: This is an involuntary
phase of the swallow and begins when the bolus passes the faucial arches, entering the pharynx
and triggering the swallow reflex. It is the critical stage of the swallow as airway closure must occur to prevent the
bolus from entering the respiratory system (Witjing & Freed, p.19). A series of events occur in a coordinated
effort to accomplish this. The velum raises achieving velopharyngeal closure. This prevents the bolus from entering
the nasopharynx. The larynx and the hyoid bone are pulled upward and forward, thus, enlarging the pharynx
and creating a vacuum effect in the hypopharynx which pulls the bolus downward (Witjing & Freed, p.19). This
elevation also contributes to the relaxation (opening) of the upper esophageal sphincter (UES). The true and false vocal
folds adduct (close) which serve as the primary protective mechanism, and the epiglottis inverts to cover the
top of the larynx, directing the bolus into the pyriform sinuses. Due to the airway closure, a short period of apnea
occurs during the pharyngeal phase. Finally, the pharyngeal muscles constrict in a superior to inferior
direction to push the bolus to the entrance of the esophagus. The duration of this phase is approximately 1 second
or less, slightly increasing as the bolus size increases (Logemann, p. 35). The pharyngeal phase ends with the
opening of the cricoesophageal sphincter.
3. The Esophageal Phase: Like the pharyngeal phase,
this phase is involuntary. It begins with the lowering of the larynx, the constriction (closing) of the upper
esophageal sphincter (UES) to prevent reflux of food particles, and the continuation of respiration. The peristaltic
wave begins at the top of the esophagus, pushing the bolus ahead of it. This continues down the esophagus
until the lower esophageal sphincter opens, allowing the bolus to enter the stomach. The esophageal phase is the
longest of the three with the duration varying from 8 to 20 seconds.
Dr. Aviv. “Normal swallowing physiology”. Voice & Swallowing Center, Retrieved March 24, 2006.
http://www.voiceandswallowing.com/swall_norm.htm
Brindle, Barbara, PhD, CCC-SLP. Western Kentucky University, CD514,
“Dysphagia” PowerPoint presentation. 2006.
Logemann, J.A.. Evaluation and Treatment of Swallowing Disorders,2nd
ed. Austin: ProEd. 1998.
Witjing, Y, & Freed, M., MA, CCC-SLP. VitalStim
Certification Program: Training Manual for Patient Assessment and
Treatment Using VitalStim Electrical Stimulation. Chattanooga Group. 2003.
Abnormal Swallowing
When there is an interruption or dysfunction in any one of the 3 swallowing phases, the result is an abnormal
swallow – or dysphagia. Swallowing disorders can affect people of all ages and for various reasons. The disorder may
be the result of various conditions ranging from “congenital abnormalities, structural damage, and/or medical conditions”
(Logemann, p.1) such as, strokes, tumors, brain injuries, gastroesophageal reflux disease (GERD), cerebral palsy, and neurological
problems or disorders. Dysphagia is the result – or expression – of a swallowing disorder. See Dysphagia
for a list of possible signs and symptoms. The purpose of this article is to provide an overview of disorders that may occur
in each swallowing phase.
The Oral Phase:
In order to achieve a normal oral phase, an individual must have sufficient strength, range of motion (ROM),
and coordination in labial, buccal, lingual, and jaw musculature. Without labial strength, food and/or liquid may leak
out of the oral cavity. There would also be difficulty approximating the lips around the spoon, straw, or cup. Buccal
musculature helps to prevent the bolus from falling into the lateral sulci (pocketing in cheeks), and assists in forming a
cohesive bolus. A lack of lingual strength, ROM and/or coordination would affect manipulating the food for chewing, forming
a cohesive bolus against the hard palate, and propelling that bolus posteriorly for the pharyngeal phase of the swallow. If
there is poor tongue base elevation and it cannot make sufficient contact with the soft palate, premature spillage into the
pyriform sinuses and valleculae may occur, putting the individual at great risk for aspiration (entry of food/liquid into
the lungs). Structural abnormalities may also affect the manipulation of the bolus and the ability to propel it back
to the pharyngeal cavity.
*Common swallowing problems occurring during the Oral phase:
- Leakage from lips
- Slow
to move bolus to back of tongue
- Pocketing
- Residue on lips/tongue/palate
- Piecemeal swallows
-
Premature spillage
- Aspiration
The Pharyngeal Phase:
As was discussed in “Normal Swallowing”, there are various physiologic activities taking place
almost simultaneously during the pharyngeal phase to transport the bolus to the esophagus, while also protecting the airway
from aspiration. This is an involuntary phase of swallowing, so these series of events happen as a result of the swallowing
reflex. When there is a delay in the reflex, the airway may not be protected in time to prevent material from entering.
If the reflex is not present at all, food may become lodged in the throat, and aspiration or airway obstruction may occur.
Just as in the oral phase, poor lingual ROM, strength and/or coordination can affect the pharyngeal phase as well. Tongue
base retraction is necessary to make contact with pharyngeal walls, thus creating pressure behind the bolus head and transporting
it towards the esophagus. This retraction also prevents food from re-entering the oral cavity. Although functional swallowing
is possible without velopharyngeal closure (all other functions being normal), this aids in the building up of pressure as
well as preventing reflux into the nasal cavity. The pharyngeal wall moves forward as well to make contact with the retracting
tongue base. Obviously, a dysfunction of the pharyngeal walls would affect the pressure needed to move the bolus.
A dysfunction in any of these areas may result in the sensation of food being “stuck” in the throat, or residue
remaining in the pharyngeal cavity after a swallow – again, putting the individual at risk for aspiration. It is important
to realize, however, that many individuals are not aware that food or residue may remain in the pharynx. This puts them at
a greater risk for aspiration (or silent aspiration). The purpose of the epiglottis seems to be to protect the airway by directing
the bolus around the larynx (Logemann, p.35). It also serves to slow the movement of liquids, allowing time for the vocal
folds to close and the larynx to elevate (Wijting & Freed, p.19). Adequate function of the epiglottis and the true and
false vocal folds are all necessary to protect against penetration and aspiration. Elevation of the hyoid bone and the larynx
are needed to open the UES, which allows the bolus to enter the esophagus. A dysfunction in this area may also result in piecemeal
swallows.
*Common swallowing problems occurring during the pharyngeal phase:
- Delayed swallow reflex
-
Slow transit
- Residue
- Aspiration
The Esophageal Phase:
The upper esophageal sphincter (cricopharyngeal sphincter) is in a normal state of contraction. Laryngeal
elevation relaxes the sphincter, allowing food into the esophagus. A cricopharyngeal dysfunction (CPD) may affect the
timing of the opening, resulting in residuals, pooling, penetration or aspiration. If the UES does not return to some
level of contraction, the reflux of food back into the pharynx may occur, again, putting the individual at risk for penetration
and aspiration. This is also seen in individuals with gastroesophageal reflux disease (GERD). Although Speech Therapists do
not treat esophageal disorders per se, they should be aware of them and “be able to differentiate them from problems
that are within their scope of practice” (Witjing & Freed, p.28).
*Common problems occurring as a result of problems in the esophageal phase:
- Slow transit
-
Backflow/reflux
- Aspiration
*Compiled from: Brindle, Barbara, PhD, CCC-SLP. “Dysphagia” PowerPoint presentation; CD514;
Western Kentucky University. 2006.
Depending on the degree of dysfunction, individuals with Cerebral Palsy may exhibit poor oral reflexive
behaviors, the inability to maintain a cohesive bolus, and uncoordinated lingual movements which make it difficult to move
the bolus in a smooth, peristaltic motion posteriorly towards the pharyngeal cavity (Logemann, p.324). Often, there is also
a delay in the swallowing reflex. Therefore, swallowing problems associated with CP are most likely to occur during the oral
phase due to “reduced tongue control for chewing or because of delayed pharyngeal swallow”, or after the swallow
(pharyngeal phase), due to “poor tongue base action or poor laryngeal elevation” (Logemann, p.325) leaving residue
in the pharynx following the swallow. Although rarely do individuals with CP experience cricopharyngeal dysfunction,
when they do, it is usually seen when they are young and normalizes as they grow and the laryngeal position lowers (Logemann,
p.325).
