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swallowing

swallowing In preparation for swallowing, a softened or liquid food bolus is moved through the mouth by the action of the tongue. The bolus lies in a longitudinal midline furrow on the tongue, and the floor of this furrow is progressively raised from before backwards, squeezing the bolus back against the hard palate. The kinetic energy imparted to the bolus then moves it into and through the pharynx, the cavity of which continues on from the mouth. In the pharynx, contractions of circularly-arranged muscles complete the movement of the bolus down into the oesophagus and thence to the stomach.

The whole process is complicated by the fact that, in the adult human, the pharynx also forms part of the airway leading from the nose to the larynx. The opening into the larynx (the glottis) is sited about halfway down the front of the pharynx. As a consequence, swallowing and breathing cannot safely occur at the same time. In contrast, in the human new-born and generally in other mammals (both infant and adult), the larynx occupies a higher position relative to the pharynx so that its opening is usually above the soft palate, which extends around it. In this situation there is a degree of anatomical separation of the respiratory tract and the alimentary tract (and in many animals the high larynx divides the pharynx into two passages, which pass laterally either side of the larynx and then rejoin lower down in the pharynx). The timed separation of swallowing and breathing is consequently less critical in this situation than it is in adult man.

The anatomical differences also produce differences in the way that the swallow is executed. The important point with the high larynx is that if the larynx, with the epiglottis that protects its opening, contacts the posterior edge of the soft palate, a space is formed, which is bounded above by the soft palate, behind by the anterior surface of the larynx, and in front and below by the top of the tongue. This space temporarily accumulates food, prior to its onward passage via pharynx and oesophagus. This storage area includes the valleculae (pockets formed between the larynx and the surface of the back of the tongue) and will be referred to as the vallecular space.

Growth in length of the human pharynx (starting a few months after birth) is associated with a descent of the larynx so that its contact with the soft palate is lost. There is consequently no longer an enclosed space in which food can be stored or accumulated, and the airway is no longer anatomically separated from the food passage. A variety of measures operate to protect the airway during swallowing in this situation. They include interruption of breathing, closure of the glottis, tipping the larynx forward so that the back of the tongue bulges over it during swallowing, plus bending of the epiglottis back and down over the laryngeal opening. Because of the low position of the glottis, the pattern of swallowing in the mature human is the exception to the general pattern in mammals. All the early studies of swallowing were carried out on human adults so that the traditional ideas and terminology of swallowing all reflect that origin. Thus swallowing of food is described as being divided into three phases (usually oral, pharyngeal, and oesophageal). In man, approximately 600 swallows occur every 24 hours, but only about 150 of these are concerned with food and drink; the rest simply clear saliva from the mouth.

When cineradiographs of mammalian (non-human) feeding are examined, it becomes clear that there are two separate processes that first fill, and then periodically empty the vallecular space so that the contents pass directly down the oesophagus. Adequate filling of the space appears to be the trigger for emptying. Unless one includes all of the tongue and jaw movements involved in suckling, lapping, or chewing, the true swallow consists only of emptying the vallecular space and the subsequent movement of the bolus down the oesophagus. In contrast, in the human adult, only one transport cycle occurs as the two processes of vallecular filling and of vallecular emptying coalesce within a single cycle of jaw and tongue movement. This occurs because emptying is usually initiated immediately the first trace of food material enters the vallecular region. The question then becomes one of how vallecular emptying is triggered so readily in the adult human, when (unlike other mammals) only a trace of food or liquid may have reached the region. In adult man, unlike other mammals, the movement of a bolus backwards within the mouth (intra-oral transport) is consequently described as the first phase of a swallow, because of its continuity with vallecular emptying.

The neural mechanisms involved in swallowing involve a number of nerves supplying the mucous membrane that lines the structures forming the vallecular space. The most important are the ninth and tenth pairs of cranial nerves (glossopharyngeal and vagus). A branch of the vagus nerve carries important sensory input from the larynx, the epiglottis, and particularly from the vallecular storage area that is present in infants and in all other non-human mammals, i.e. in all those with a high glottis. In these cases, swallowing can be elicited reflexly by fluid in the vallecular space even when there are no connections from higher parts of the brain above the brainstem (e.g. in decerebrate animals and in infants with anencephaly, where the cerebral hemispheres are congenitally absent). It can therefore be assumed that all the necessary neural components for swallowing are present below the level of the midbrain and that sensory input from the surface of the palate, epiglottis, and tongue (the walls of the vallecular space) is alone sufficient to provide the activation necessary to elicit a swallow.

The same argument applies to swallowing in the fetus and in the new-born human with an immature central nervous system. However, in the adult human there is no longer an enclosed vallecular space. Consequently, the level of sensory input must be less than that which would arise when all the mucosal surfaces surrounding that space were stimulated by its filling.

The generally accepted view is that the sensory input from the back of the mouth activates a set of neural circuits within the brain stem that collectively produce the pattern of motor activity constituting a swallow. These circuits constitute a pattern generator for the activity involving the thirty or so muscles that take part in a swallow. The relevant network of brain stem neurons receives sensory input from nerves innervating the mouth, and it also receives excitatory fibres descending from the cerebral cortex.

To explain the situation in adult man, it is proposed that the activity in the nerve fibres descending from the cortex is sufficient to lower the threshold for reflex emptying of the valleculae so that only a trace of material has to reach this region to elicit emptying. A conscious swallow therefore seems to differ from other voluntary movements. One can test this oneself by repeatedly swallowing to eliminate saliva from the mouth; swallowing becomes progressively more difficult to perform and it eventually becomes impossible even to initiate the movement; i.e. there is nothing left to elicit the reflex. The corollary is that, in the presence of excitation from the cortex (a conscious desire to swallow), sensory inputs can elicit vallecular emptying very easily, even though only a trace of material has entered the vallecular region. Vallecular emptying and pharyngeal transit are then followed immediately by oesophageal peristalsis (a moving wave of contraction), so that these events follow seamlessly upon the first phase of intra-oral transport, giving rise to the classical appearance of the three-stage human swallow. It is also necessary to relax the sphincters (rings of muscle fibres) at the top and the bottom of the oesophagus so as to allow the passage of the bolus into the oesophagus and then into the stomach respectively.

‘Dysphagia’ is a word used to describe difficulty or discomfort in swallowing. Clearly a cyst or tumour restricting the width of the pharynx or oesophagus could give rise to such a state. A number of other types of disorder affect swallowing. These include muscle weakness, inability to relax a sphincter, peripheral nerve lesions, and central nervous system damage: a lesion in the medulla can directly damage the neurons making up the swallowing centre. More commonly, swallowing becomes disordered when the motor nerve fibres descending from the cerebral cortex are interrupted, as in a stroke. The malfunction occurs presumably because an important source of excitation to the relevant cells in the medulla is removed, so raising the threshold for reflex emptying of the valleculae. Failure to maintain a competent sphincter at the lower end of the oesophagus (which can occur in diaphragmatic hernia, when part of the stomach protrudes upwards through the diaphragm into the chest) permits regurgitation of the acid contents of the stomach; this can cause discomfort when swallowing and is sometimes loosely classified as dysphagia.

Allan Thexton

Bibliography

Thexton, A. J. and and Crompton, A. W. (1999). ‘Control of Swallowing’ in Scientific Basis of Eating (Frontiers of Oral Biology. Vol 9) Ed. R. W. A. Linden, Karger, Basel, p. 168–222.


See alimentary system.See also epiglottis; larynx; pharynx; tongue.

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Swallowing

SWALLOWING

Swallowing allows people to eat and drink, thus providing nutrients for growth and maintenance of body tissue. Saliva is regularly swallowed while awake and during sleep. Though swallowing usually occurs automatically, it involves a complex sequence of nerve and muscle coordination managed by the brain.

Normally, food and drink are formed into a mass by the mouth and channeled by the tongue to the back of the mouth, where the swallow is triggered. The pharynx and larynx, which are situated at the top of the esophagus (foodpipe) and trachea (windpipe), contract and elevate to protect the trachea. This is essential to prevent choking and inhalation of foreign substances. The mass is rapidly pushed through the pharynx into the esophagus, and then by coordinated muscular contractions to the stomach. Any disruption to this sequence can result in swallowing difficulties (technically known as dysphagia).

In the healthy adult noticeable swallowing difficulties are rare. However, changes associated with aging can affect the efficiency of the muscles that facilitate swallowing. As a result of these normal variations, some elderly people may be predisposed to dysphagia when they are ill. The likelihood of some illnesses increases with age, and a number of medical conditions are associated with dysphagia.

A common example is stroke. In the early stages of stroke, approximately half of those affected may develop dysphagia. Prevention of choking and consequent chest infection is a high priority. Fortunately, only a few stroke patients have persistent problems and recovery is common, even at advanced age. Other diseases develop more gradually (e.g., Parkinsons disease and the various types of dementia). Eating and drinking can be slow and effortful procedures that deteriorate progressively. The consistencies of food and drink that can be swallowed easily and safely become more limited over time. Sometimes the first signs of a disease are difficulties with speech and swallowing (e.g., in amyotrophic lateral sclerosis or myasthenia gravis). Chronic illness affecting the breathing muscles can interrupt the fine coordination between breathing and swallowing, contributing to recurrent chest infections. Any severe illness can lead to generalized muscle weakness and consequent dysphagia, though this is usually a temporary effect.

Mechanical problems may also be a source of swallowing difficulty. Elderly people are more prone to osteophytes. These are bony growths from the spine and may push into the throat muscles causing coughing or discomfort when food or drink pass over the misshapen area. Another example is the development of a pouch (like a small pocket) in the pharynx or upper esophagus, impeding the smooth progression of the food or fluid mass to the stomach. Infections (such as thrush) can cause painful swallowing. Surgical procedures to any area related to the swallowing anatomy can also result in swallowing difficulties. A sensation of something sticking in the throat is often reported. This may be due to organic disease of the esophagus or stomach. If no physical cause is found, the reason may be psychological.

In many conditions the swallowing either improves spontaneously or strategies are used to make swallowing easier. If effective swallowing is impossible to achieve, then it may be necessary to consider feeding via a tube. This can be used temporarily or for a long period.

Catherine Exley

See also Stroke; Tube Feeding.

BIBLIOGRAPHY

Groher, M. E. Dysphagia: Diagnosis and Management, 3d ed. Boston: Butterworth-Heinemann, 1997.

Jones, B., and Donner, M. W. Normal and Abnormal Swallowing, Imaging in Diagnosis and Therapy. New York: Springer-Verlag, 1991.

Logemann, J. Evaluation and Treatment of Swallowing Disorders. Austin, Tex: Pro-ed., 1983.

Love, R. J., and Webb, W. G. Neurology for the Speech-Language Pathologist, 2d ed. Newton, Mass.: Butterworth-Heinemann, 1992.

SYNCOPE

See Fainting

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deglutition

deglutition (swallowing) A reflex action initiated by the presence of food in the pharynx. During deglutition, the soft palate is raised, which prevents food from entering the nasal cavity; the epiglottis closes, which blocks the entrance to the windpipe; and the oesophagus starts to contract (see peristalsis), which ensures that food is conveyed to the stomach.

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swallowing

swallowing (deglutition) (swol-oh-ing) n. the process by which food is transferred from the mouth to the oesophagus. Voluntary raising of the tongue forces food backwards towards the pharynx. This stimulates reflex actions in which the larynx and the nasal passages are closed so that food does not enter the trachea.

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dysphagia

dysphagia (dis-fay-jiă) n. a condition in which the action of swallowing is either difficult to perform, painful (see odynophagia), or in which swallowed material seems to be held up in its passage to the stomach.

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dysphagia

dysphagia Difficulty in swallowing, commonly associated with disorders of the oesophagus. Inability to swallow is aphagia.

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deglutition

deglutition (dee-gloo-tish-ŏn) n. see swallowing.

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deglutition

deglutition The act of swallowing.

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swallowing

swallowing See deglutition.

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Dysphagia

Dysphagia

Definition

Dysphagia is a disorder of swallowing.

Description

Dysphagia is a disruption in the ability to move food or liquid from the mouth through the pharynx and esophagus into the stomach safely and efficiently. Swallowing disorders can occur at any point in the life span from infancy through old age. It is estimated that approximately 6,228,000 Americans over age 60 have dysphagia, and that it occurs in 32% of all patients in intensive care units. If untreated, dysphagia can result in dehydration, weight loss, malnutrition, pneumonia, and, in rare cases, death.

In order to understand dysphagia, it helps to understand the normal swallow. A normal swallow rapidly carries a bolus of food or liquid through the mouth, pharynx, and esophagus, leaving these structures substantially clear of residue at its completion. It involves a complex interaction of sensory stimuli and motor responses that encompass both voluntary and involuntary behaviors.

A normal swallow consists of four phases: the oral preparatory phase, the oral phase, the pharyngeal phase, and the esophageal phase.

The oral preparatory phase readies the food or liquid for swallowing. The lips close and seal to contain the material in the mouth. Solid food is chewed and mixed with saliva. The tongue gathers the liquid or solid material into a bolus and holds it. During this phase, the entry into the airway is open and nasal breathing continues.

The oral phase begins when the tongue starts to move the bolus backward toward the pharynx. It ends when the head of the bolus passes into the pharynx.

The pharyngeal phase begins when the bolus enters the pharynx and ends when it passes into the esophagus. In this phase, sensory stimuli interact with reflex and volitional movements to trigger the swallow response, which includes:

  • elevation and retraction of the soft palate to prevent material from entering the nose
  • elevation and forward movement of the hyoid and larynx, which moves them out of the path of the bolus as it travels downward, thus helping to prevent it from entering the airway below
  • closure of the larynx, which stops respiration momentarily and prevents the bolus from entering the airway below
  • retraction of the tongue base and contraction of the posterior pharyngeal wall, which build pressure to propel the bolus downward
  • progressive top to bottom contraction of the pharyngeal constrictor muscles, placing additional downward pressure on the bolus
  • opening of the pharyngoesophageal segment to allow the bolus to pass into the esophagus

The esophageal phase of the swallow begins when the bolus enters the esophagus and ends when it passes into the stomach. Muscular contractions push the bolus downward through the lower esophageal sphincter into the stomach.

Causes and symptoms

Causes

Dysphagia occurs when any element of the normal swallow is disrupted. Oral structural abnormalities, muscular weakness, or incoordination may interfere with holding material in the mouth, forming it into a cohesive bolus, and propelling it backward into the pharynx. Lack of control over the material in the mouth might cause it to fall over the back of the tongue prematurely, while the airway is unprotected, or it might result in material remaining in the mouth after the swallow, when it could fall into the pharynx. If the bolus enters the pharynx before or after the swallow, while the airway is open and unprotected, there is a danger that aspiration will occur. Similarly, structural abnormalities, weakness, or incoordination in the pharynx or larynx may interfere with protection of the airway during the swallow or with the downward propulsion and emptying of the bolus into the esophagus. Finally, structural abnormalities, weakness, or incoordination in the esophagus may interfere with the progress of the bolus through the esophagus into the stomach.

Common etiologies of dysphagia include:

  • strokes
  • head injuries
  • cervical spinal cord injuries
  • progressive neurologic diseases
  • head and neck cancer and the surgery or radiation used to treat it
  • congenital syndromes and abnormalities
  • esophageal stenosis
  • esophageal tumors
  • esophageal motility disorders
  • achalasia
  • gastroesophageal reflux disease

Medications may also cause or exacerbate dysphagia. Antipsychotic drugs that cause extrapyramidal symptoms like tardive dyskinesia may cause dysphagia, and some anticholinergic drugs may impair swallowing ability.

Symptoms

Common symptoms of dysphagia include:

  • inability to control food or saliva in the mouth
  • residue in the mouth after the swallow
  • coughing during or after the swallow
  • gurgly or wet vocal quality associated with swallowing
  • unexplained weight loss
  • increased time to consume a meal
  • complaints of globus
  • recurring pneumonia
  • heartburn

Diagnosis

Diagnosis of dysphagia generally involves a clinical screening evaluation (sometimes called a bedside evaluation) and an instrumental evaluation. The clinical screening evaluation includes review of the medical history; current medical status; examination of oral anatomy and oral motor functioning; perceptual evaluation of laryngeal functioning; and observation of eating and drinking unless the risk of aspiration is very high and the individual is deemed too medically fragile to tolerate it. If the clinical screening evaluation suggests the presence of a dysphagia, it is usually followed by an instrumental evaluation.

The instrumental evaluation that is most widely used for diagnosing oropharyngeal dysphagia is the videofluoroscopic modified barium swallow (MBS) study. The MBS study allows the observation of structures and movements as the individual swallows controlled amounts of various consistencies (usually thin and thick liquid, a paste or pudding consistency, and solid food) while seated in an upright position. It provides information about transit times through the mouth and pharynx, motility problems, and the presence and etiology of aspiration. The MBS is done in the radiology department and requires the patient's cooperation. Thus, it may be contraindicated for patients who are unable to cooperate with instructions, or who are too medically fragile to be transported.

Videoendoscopy, or flexible fiberoptic examination of swallowing (FEES), is another procedure used to examine for oropharyngeal dysphagia. A flexible scope is inserted through the nose into the pharynx, allowing observation of the pharynx before and after the pharyngeal swallow is triggered. It does not allow observation of the oral or esophageal phases of the swallow, and, because the image is blocked by the constriction of the pharynx around the scope during the pharyngeal swallow, the presence and etiology of aspiration may be inferred but cannot be observed. This procedure can be done at the bedside and requires minimal cooperation from the patient, making it useful for patients who cannot tolerate an MBS study.

The instrumental evaluation most frequently used for esophageal dysphagia is the standard barium swallow or upper gastrointestinal series. This differs from the MBS study in that the patient is required to swallow a much larger amount of barium, typically while lying in the prone position. It allows observation of structures and of the movement of the material through the esophagus and into the stomach. When gastroesophageal reflux disease is suspected, continuous pH monitoring that measures the pH level of the contents of the lower esophagus is considered the best single test for its diagnosis.

Other instrumental evaluations that are sometimes used, either alone or in combination with the more standard techniques, include: ultrasound of the oral cavity, scintigraphy, electromyography, cervical auscultation, and manometry.

Treatment

Treatment of oropharyngeal dysphagia depends on the etiology and the severity of the problem. An essential component of treatment is education of the patient, family, and other caregivers regarding the nature of the swallowing problem, its potential complications, and the importance of following recommendations to prevent such complications. Treatment may also involve one or more of the following:

  • An exercise program to improve the strength, range of motion, speed, and/or coordination of movements.
  • Diet modifications that eliminate food or liquids of consistencies that are at high risk of being aspirated.
  • Teaching of specific postures or strategies designed to reduce or eliminate the risk of aspiration when swallowing.
  • Use of an alternate means of feeding, such as a gastric tube, either temporarily while other treatment strategies are attempted, or permanently if other treatment is unsuccessful.
  • Esophageal dysphagia is usually medically, rather than behaviorally, managed. Dilatation is the typical treatment for esophageal stenosis. Surgery is most often used for esophageal tumors. Medications are used to treat motility disorders. Achalasia may be treated with smooth muscle relaxant drugs, dilatation, or surgery. Gastroesophageal reflux disease may be managed through dietary and lifestyle modifications, specifically: decreasing or eliminating certain foods from the diet, elevating the head of the bed for sleeping, avoiding lying down within two hours of eating, and eliminating smoking. Drugs and surgery are also used to treat this disorder.

Prognosis

The prognosis for recovery from dysphagia varies from excellent to poor depending on its severity, etiology, and the ability of the individual to comply with treatment recommendations.

Health care team roles

Identification, diagnosis, and management of dysphagia is a multidisciplinary effort. In most settings, speech-language pathologists perform screening evaluations, collaborate with a physician (usually a radiologist or otolaryngologist) in instrumental evaluations, design and implement a treatment program for oropharyngeal dysphagia, and provide education to the patient, family, and other staff members. The dietitian monitors the patient's nutritional status. The nursing staff, often the first to recognize dysphagic symptoms, encourages daily compliance with the recommended treatment program. Occupational and physical therapists work on feeding, adaptive devices, and sitting balance. (In some settings an occupational therapist is the primary swallowing therapist.) Physicians monitor and treat the patient's overall medical status. They are typically the primary treatment providers for esophageal dysphagia.

Prevention

Prevention of dysphagia requires prevention of the conditions that cause dyphagia, such as stroke, head trauma, or head and neck cancer. Preventionof complications from dysphagia involves adherence to the individualized treatment program, which usually specifies the precautions that should be taken. Although these will vary for each individual, they generally include eating and drinking only those foods and liquids of the recommended consistencies, sitting upright for oral intake, taking small amounts at a slow rate, ensuring that the mouth is clear after a swallow and at the end of a meal, using recommended strategies on every swallow, maintaining good oral hygiene, and remaining upright for 30 minutes after eating or longer if there is an esophageal dysphagia.

KEY TERMS

Achalasia— Failure of the pharyngoesophageal segment to relax sufficiently to allow swallowed material to pass from the esophagus into the stomach.

Anterior faucial arches— Also called the glossopalatine arches, these pillar-like structures run from the palate down to the tongue laterally in the back of the mouth.

Anticholinergic drugs— Drugs that affect the parasympathetic system.

Aspiration— Entry of food or liquid into the airway below the level of the true vocal folds. Aspiration of large amounts or of small amounts over a period of time may result in pneumonia.

Cervical auscultation— Listening to the sounds of swallowing, usually via a stethoscope.

Dilatation— The stretching of a structure by swallowing increasingly larger sized rubber catheters filled with mercury.

Electromyography— Measures the timing and amplitude of selected muscle contractions.

Esophageal stenosis— Narrowing of the esophagus.

Esophagus— The tube that carries food or liquid from the pharynx to the stomach.

Globus— The feeling that there is a lump in the throat.

Hyoid— A small bone at the root of the tongue to which many lingual muscles are attached. It provides a stable base for tongue movement.

Larynx— Commonly called the voice box, this structure of muscle and cartilage sits at the top of the trachea.

Manometry— Measures of pressure changes that occur in the pharynx and/or esophagus during the swallow.

Motility— Movement.

Pharyngoesophageal segment— Also called the cricopharyngeal muscle or the upper esophageal sphincter (UES), this segment is normally in tonic contraction in awake individuals to prevent air from entering the esophagus during respiration and to reduce the risk of reflux from the pharynx into the esophagus.

Pharynx— The hollow muscular tube, commonly called the throat, that runs from the base of the skull to the opening of the esophagus.

Reflux— Backward flow of food and stomach acid from the stomach into the esophagus.

Scintigraphy— A nuclear medicine test requiring the patient to swallow measured amounts of radioactive substance. It can reveal the amount of aspiration and residue, but does not allow visualization of structures or movements.

Tardive dyskinesia— A disorder characterized by abnormal involuntary movements.

Resources

BOOKS

Johnson, Alex F. and Jacobson, Barbara H. Medical SpeechLanguage Pathology: A Practitioner's Guide. New York: Thieme, 1998.

Logemann, Jeri A. Evaluation and Treatment of Swallowing Disorders, 2nd ed. Austin: Pro-ed, 1998.

PERIODICALS

Zorowitz, Richard D. and K. Robinson. "Pathophysiology of Dysphagia and Aspiration." Topics in Stroke Rehabilitation 6, no. 3 (Fall 1999): 1-16.

ORGANIZATIONS

American Speech Language Hearing Association. 10801 Rockville Pk., Rockville, MD 20852. (888) 321-ASHA. 〈http://www.als.uiuc.edu/drs/〉.

Center for Swallowing Research. Massachusetts Institute of Technology, Cambridge, MA. 〈http://swallow.mit.edu/swallow.html〉.

OTHER

Agency for Health Care Policy and Research. Diagnosis and Treatment of Swallowing Disorders (Dysphagia) in Acute-Care Stroke Patients: Evidence Report/Technology Assessment Number 8. Rockville, MD: U.S. Department of Health and Human Services, July 1999.

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Dysphagia

Dysphagia

Definition

Dysphagia is a disorder of swallowing.

Description

Dysphagia is a disruption in the ability to move food or liquid from the mouth through the pharynx and esophagus into the stomach safely and efficiently. Swallowing disorders can occur at any point in the life span from infancy through old age. It is estimated that approximately 6,228,000 Americans over age 60 have dysphagia, and that it occurs in 32% of all patients in intensive care units. If untreated, dysphagia can result in dehydration , weight loss, malnutrition, pneumonia , and, in rare cases, death.

In order to understand dysphagia, it helps to understand the normal swallow. A normal swallow rapidly carries a bolus of food or liquid through the mouth, pharynx, and esophagus, leaving these structures substantially clear of residue at its completion. It involves a complex interaction of sensory stimuli and motor responses that encompass both voluntary and involuntary behaviors.

A normal swallow consists of four phases: the oral preparatory phase, the oral phase, the pharyngeal phase, and the esophageal phase.

The oral preparatory phase readies the food or liquid for swallowing. The lips close and seal to contain the material in the mouth. Solid food is chewed and mixed with saliva. The tongue gathers the liquid or solid material into a bolus and holds it. During this phase, the entry into the airway is open and nasal breathing continues.

The oral phase begins when the tongue starts to move the bolus backward toward the pharynx. It ends when the head of the bolus passes into the pharynx.

The pharyngeal phase begins when the bolus enters the pharynx and ends when it passes into the esophagus. In this phase, sensory stimuli interact with reflex and volitional movements to trigger the swallow response, which includes:

  • elevation and retraction of the soft palate to prevent material from entering the nose
  • elevation and forward movement of the hyoid and larynx, which moves them out of the path of the bolus as it travels downward, thus helping to prevent it from entering the airway below
  • closure of the larynx, which stops respiration momentarily and prevents the bolus from entering the airway below
  • retraction of the tongue base and contraction of the posterior pharyngeal wall, which build pressure to propel the bolus downward
  • progressive top to bottom contraction of the pharyngeal constrictor muscles, placing additional downward pressure on the bolus
  • opening of the pharyngoesophageal segment to allow the bolus to pass into the esophagus

The esophageal phase of the swallow begins when the bolus enters the esophagus and ends when it passes into the stomach. Muscular contractions push the bolus downward through the lower esophageal sphincter into the stomach.

Causes and symptoms

Causes

Dysphagia occurs when any element of the normal swallow is disrupted. Oral structural abnormalities, muscular weakness, or incoordination may interfere with holding material in the mouth, forming it into a cohesive bolus, and propelling it backward into the pharynx. Lack of control over the material in the mouth might cause it to fall over the back of the tongue prematurely, while the airway is unprotected, or it might result in material remaining in the mouth after the swallow, when it could fall into the pharynx. If the bolus enters the pharynx before or after the swallow, while the airway is open and unprotected, there is a danger that aspiration will occur. Similarly, structural abnormalities, weakness, or incoordination in the pharynx or larynx may interfere with protection of the airway during the swallow or with the downward propulsion and emptying of the bolus into the esophagus. Finally, structural abnormalities, weakness, or incoordination in the esophagus may interfere with the progress of the bolus through the esophagus into the stomach.

Common etiologies of dysphagia include:

  • strokes
  • head injuries
  • cervical spinal cord injuries
  • progressive neurologic diseases
  • head and neck cancer and the surgery or radiation used to treat it
  • congenital syndromes and abnormalities
  • esophageal stenosis
  • esophageal tumors
  • esophageal motility disorders
  • achalasia
  • gastroesophageal reflux disease

Medications may also cause or exacerbate dysphagia. Antipsychotic drugs that cause extrapyramidal symptoms like tardive dyskinesia may cause dysphagia, and some anticholinergic drugs may impair swallowing ability.

Symptoms

Common symptoms of dysphagia include:

  • inability to control food or saliva in the mouth
  • residue in the mouth after the swallow
  • coughing during or after the swallow
  • gurgly or wet vocal quality associated with swallowing
  • unexplained weight loss
  • increased time to consume a meal
  • complaints of globus
  • recurring pneumonia
  • heartburn

Diagnosis

Diagnosis of dysphagia generally involves a clinical screening evaluation (sometimes called a bedside evaluation) and an instrumental evaluation. The clinical screening evaluation includes review of the medical history; current medical status; examination of oral anatomy and oral motor functioning; perceptual evaluation of laryngeal functioning; and observation of eating and drinking unless the risk of aspiration is very high and the individual is deemed too medically fragile to tolerate it. If the clinical screening evaluation suggests the presence of a dysphagia, it is usually followed by an instrumental evaluation.

The instrumental evaluation that is most widely used for diagnosing oropharyngeal dysphagia is the videofluoroscopic modified barium swallow (MBS) study. The MBS study allows the observation of structures and movements as the individual swallows controlled amounts of various consistencies (usually thin and thick liquid, a paste or pudding consistency, and solid food) while seated in an upright position. It provides information about transit times through the mouth and pharynx, motility problems, and the presence and etiology of aspiration. The MBS is done in the radiology department and requires the patient's cooperation. Thus, it may be contraindicated for patients who are unable to cooperate with instructions, or who are too medically fragile to be transported.

Videoendoscopy, or flexible fiberoptic examination of swallowing (FEES), is another procedure used to examine for oropharyngeal dysphagia. A flexible scope is inserted through the nose into the pharynx, allowing observation of the pharynx before and after the pharyngeal swallow is triggered. It does not allow observation of the oral or esophageal phases of the swallow, and, because the image is blocked by the constriction of the pharynx around the scope during the pharyngeal swallow, the presence and etiology of aspiration may be inferred but cannot be observed. This procedure can be done at the bedside and requires minimal cooperation from the patient, making it useful for patients who cannot tolerate an MBS study.


KEY TERMS


Achalasia —Failure of the pharyngoesophageal segment to relax sufficiently to allow swallowed material to pass from the esophagus into the stomach.

Anterior faucial arches —Also called the glossopalatine arches, these pillar-like structures run from the palate down to the tongue laterally in the back of the mouth.

Anticholinergic drugs —Drugs that affect the parasympathetic system.

Aspiration —Entry of food or liquid into the airway below the level of the true vocal folds. Aspiration of large amounts or of small amounts over a period of time may result in pneumonia.

Cervical auscultation —Listening to the sounds of swallowing, usually via a stethoscope.

Dilatation —The stretching of a structure by swallowing increasingly larger sized rubber catheters filled with mercury.

Electromyography —Measures the timing and amplitude of selected muscle contractions.

Esophageal stenosis —Narrowing of the esophagus.

Esophagus —The tube that carries food or liquid from the pharynx to the stomach.

Globus —The feeling that there is a lump in the throat.

Hyoid —A small bone at the root of the tongue to which many lingual muscles are attached. It provides a stable base for tongue movement.

Larynx —Commonly called the voice box, this structure of muscle and cartilage sits at the top of the trachea.

Manometry —Measures of pressure changes that occur in the pharynx and/or esophagus during the swallow.

Motility —Movement.

Pharyngoesophageal segment —Also called the cricopharyngeal muscle or the upper esophageal sphincter (UES), this segment is normally in tonic contraction in awake individuals to prevent air from entering the esophagus during respiration and to reduce the risk of reflux from the pharynx into the esophagus.

Pharynx —The hollow muscular tube, commonly called the throat, that runs from the base of the skull to the opening of the esophagus.

Reflux —Backward flow of food and stomach acid from the stomach into the esophagus.

Scintigraphy —A nuclear medicine test requiring the patient to swallow measured amounts of radioactive substance. It can reveal the amount of aspiration and residue, but does not allow visualization of structures or movements.

Tardive dyskinesia —A disorder characterized by abnormal involuntary movements.


The instrumental evaluation most frequently used for esophageal dysphagia is the standard barium swallow or upper gastrointestinal series. This differs from the MBS study in that the patient is required to swallow a much larger amount of barium, typically while lying in the prone position. It allows observation of structures and of the movement of the material through the esophagus and into the stomach. When gastroesophageal reflux disease is suspected, continuous pH monitoring that measures the pH level of the contents of the lower esophagus is considered the best single test for its diagnosis.

Other instrumental evaluations that are sometimes used, either alone or in combination with the more standard techniques, include: ultrasound of the oral cavity, scintigraphy, electromyography , cervical auscultation, and manometry.

Treatment

Treatment of oropharyngeal dysphagia depends on the etiology and the severity of the problem. An essential component of treatment is education of the patient, family, and other caregivers regarding the nature of the swallowing problem, its potential complications, and the importance of following recommendations to prevent such complications. Treatment may also involve one or more of the following:

  • An exercise program to improve the strength, range of motion, speed, and/or coordination of movements.
  • Diet modifications that eliminate food or liquids of consistencies that are at high risk of being aspirated.
  • Teaching of specific postures or strategies designed to reduce or eliminate the risk of aspiration when swallowing.
  • Use of an alternate means of feeding, such as a gastric tube, either temporarily while other treatment strategies are attempted, or permanently if other treatment is unsuccessful.
  • Esophageal dysphagia is usually medically, rather than behaviorally, managed. Dilatation is the typical treatment for esophageal stenosis. Surgery is most often used for esophageal tumors. Medications are used to treat motility disorders. Achalasia may be treated with smooth muscle relaxant drugs, dilatation, or surgery. Gastroesophageal reflux disease may be managed through dietary and lifestyle modifications, specifically: decreasing or eliminating certain foods from the diet, elevating the head of the bed for sleeping, avoiding lying down within two hours of eating, and eliminating smoking. Drugs and surgery are also used to treat this disorder.

Prognosis

The prognosis for recovery from dysphagia varies from excellent to poor depending on its severity, etiology, and the ability of the individual to comply with treatment recommendations.

Health care team roles

Identification, diagnosis, and management of dysphagia is a multidisciplinary effort. In most settings, speech-language pathologists perform screening evaluations, collaborate with a physician (usually a radiologist or otolaryngologist) in instrumental evaluations, design and implement a treatment program for oropharyngeal dysphagia, and provide education to the patient, family, and other staff members. The dietitian monitors the patient's nutritional status. The nursing staff, often the first to recognize dysphagic symptoms, encourages daily compliance with the recommended treatment program. Occupational and physical therapists work on feeding, adaptive devices, and sitting balance. (In some settings an occupational therapist is the primary swallowing therapist.) Physicians monitor and treat the patient's overall medical status. They are typically the primary treatment providers for esophageal dysphagia.

Prevention

Prevention of dysphagia requires prevention of the conditions that cause dyphagia, such as stroke, head trauma, or head and neck cancer . Prevention of complications from dysphagia involves adherence to the individualized treatment program, which usually specifies the precautions that should be taken. Although these will vary for each individual, they generally include eating and drinking only those foods and liquids of the recommended consistencies, sitting upright for oral intake, taking small amounts at a slow rate, ensuring that the mouth is clear after a swallow and at the end of a meal, using recommended strategies on every swallow, maintaining good oral hygiene , and remaining upright for 30 minutes after eating or longer if there is an esophageal dysphagia.

Resources

BOOKS

Johnson, Alex F. and Jacobson, Barbara H. Medical Speech-Language Pathology: A Practitioner's Guide. New York: Thieme, 1998.

Logemann, Jeri A. Evaluation and Treatment of Swallowing Disorders 2nd ed. Austin: Pro-ed, 1998.

PERIODICALS

Zorowitz, Richard D. and K. Robinson. "Pathophysiology of Dysphagia and Aspiration." Topics in Stroke Rehabilitation 6, no. 3 (Fall 1999): 1-16.

ORGANIZATIONS

American Speech Language Hearing Association. 10801 Rockville Pk., Rockville, MD 20852. (888) 321-ASHA. <http://www.als.uiuc.edu/drs/>.

Center for Swallowing Research. Massachusetts Institute of Technology, Cambridge, MA. <http://swallow.mit.edu/swallow.html>.

OTHER

Agency for Health Care Policy and Research. Diagnosis and Treatment of Swallowing Disorders (Dysphagia) in Acute-Care Stroke Patients: Evidence Report/Technology Assessment Number 8. Rockville, MD: U.S. Department of Health and Human Services, July 1999.

Mary Boyle, Ph.D., CCC-SLP, BC-NCD

Cite this article
Pick a style below, and copy the text for your bibliography.

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  • Chicago
  • APA

"Dysphagia." Gale Encyclopedia of Nursing and Allied Health. . Encyclopedia.com. 18 Aug. 2018 <http://www.encyclopedia.com>.

"Dysphagia." Gale Encyclopedia of Nursing and Allied Health. . Encyclopedia.com. (August 18, 2018). http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/dysphagia-0

"Dysphagia." Gale Encyclopedia of Nursing and Allied Health. . Retrieved August 18, 2018 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/dysphagia-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

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The Chicago Manual of Style

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American Psychological Association

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Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.