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Swallowing

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First posted Feb 2009 by Charles Gomersall

Click here to view a narrated lecture on swallowing

Physiology & anatomy

Stages

  1. Mastication
  2. Oral transfer
  3. Pharyngeal
  4. Oesophageal

Mastication

  • Produces a bolus of food in a shape, size and consistency that can be swallowed
  • Bolus then postioned on tongue for swallowing

Oral transfer

  • Tongue pressed progressively against hard palate

  • Concurrently: soft palate elevates, while the cheeks, floor of mouth, and jaw are braced.

  • End of phase: posterior dorsum of the tongue sealed against the soft palate

Muscles involved in oral transfer
Innervation
Muscles of mastication
V2
Orbicularis oris
VII
Intrinsic and extrinsic muscles of tongue
XII
Palatal muscles
V3, X, XI

 Pharyngeal

  • 4 exits from pharynx:

    • Oesophagus

    • Mouth

    • Nose

    • Larynx

  • Bolus needs to be rapidly propelled into oesophagus while other exits are closed

  • Mouth: tongue remains sealed against palate

  • Nose: soft palate elevates and proximal pharyngeal walls move medially

  • Larynx

    • vocal cords and arytenoids adduct

    • epiglottis swings down to cover the laryngeal vestibule

    • hyoid and larynx move superiorly and anteriorly, bringing the larynx to a position under the base of the tongue, and out of the path of the bolus

    • larger boluses:

      • bolus head reaches the level of the laryngeal vestibule before the epiglottis has completed its downward descent

      • channeled around the larynx into the piriform recesses

    • laryngeal opening not completely closed during swallowing: small food particles may enter larynx for a short distance - opposed by subglottic pressure

  • Propulsion of bolus into oesophagus

    • peristaltic wave starting in oropharynx

    • upper oesophageal sphincter relaxes and then re-contracts after passage of bolus

    • pharynx widens and shortens as hyoid and larynx are elevated. This creates negative pressure which sucks bolus into pharynx.

  • Duration ~1 sec, during which time subject must remain apnoeic

Muscle groups involved in pharyngeal phase
Innvervation
Suprahyoid
V3, VII, XII
Infrahyoid
Ansa cervicalis (C1-2)
Pharyngeal
IX, X, XI
Laryngeal
X

Click here to view animation of oral transfer and pharyngeal phases 

Oesophageal phase

  • Peristaltic wave continues down oesophagus

  • Coordinated relaxation of lower oesophageal sphincter

Effect of tracheostomy on swallowing

  • Trachea tethered to the anterior neck skin: prevents proper laryngeal elevation

  • Direct pressure from the tracheostomy tube ­ extrinsic oesophageal pressure regurgitation and even aspiration

  • ¯ pharyngeal sensation ¯ sensitivity of the glottic closure reflex
  • loss of subglottic pressure
  • Impaired cough (cuffed tracheostomy)

  • Also consider effect of underlying disease that led to insertion of tracheostomy

    • Vocal cord palsy

    • Laryngeal/pharyngeal lesions

    • Neuromuscular disease

Assessment of swallowing

General

  • Consciousness and cognition

  • Weakness

  • Dyspnoea

  • ETT/tracheostomy

  • Drugs (eg sedatives)

Tracheostomy

  • Size: ­­ risk of dysphagia
  • Cuff: risk of dysphagia greater with cuffed tracheostomies

  • Expiratory valve/cap restores subglottic pressure and facilitates swallowing

Cranial nerves

  • V, VII, IX-XII

Investigations

Dye

  • Deflate cuff. Otherwise dye may pool above cuff resulting in a false negative test

  • Suction mouth and trachea

  • Oral administration thick liquid containing dye

  • Suction trachea looking for dye

  • High specificity

  • Lower sensitivity

  • Does not give an indication of cause of swallowing difficulty

Fibreoptic endoscopic evaluation of swallowing

  • Transnasal insertion of endoscope

  • Positioned just above larnyx

  • Observe during swallowing

  • Gives information on cause for difficulty

  • High level of training required

  • Cannot detect aspiration during swallowing as view of larynx is obscured by food bolus

Barium videofluoroscopy

  • Requires patient cooperation

  • Allows effect of therapeutic manoeuvres to be assessed

Reducing risk of aspiration

Feeding pattern

  • "Dry" swallows may help clear pharyngeal residue

  • Series of single swallows may be better than consecutive swallows when eating

Consistency of feed

  • Thick liquids better than thin - less risk of bolus fragmenting

Ventilator mode & tracheostomy management

  • Assisted ventilation - allows coordination of swallowing and breathing

  • Partial/complete cuff deflation - beware dysynchrony

  • Expiratory valve on tracheostomy

© Charles Gomersall, Feb 2009


©Charles Gomersall, April, 2014 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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