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

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