Lecture discusses how many stages of the swallow? What are they?
4 stages
1) Oral preparatory stage
2) Oral stage
3) Pharyngeal stage
4) Oesophageal stage
Oral Preparatory phase:
Preparing the bolus, getting bolus ready
Oral (transit) phase:
Transit of the bolus from mouth into pharyngeal cavity.
Pharyngeal stage
swallowing elicited, bolus moves through pharynx
Esophageal phase
Bolus is cleared into the esophagus
Stage 1: Oral Preparatory phase:
- Food masticated and formed into bolus.
- Salivary glands stimulated (CN VII and IX)
- Anterior and posterior tongue elevated, soft palate containing bolus in oral cavity (CN V, IX, X, XII)
- lips sealed (CN VII)
- Tongue manipulating bolus (CN XII)
- Cheeks helping contain bolus (CN VII)
- Jaw chewing (CN V)
- Taste detected (CN VII)
- Bolus texture detected (CN V - indicates readiness for swallowing)
Stage 2: Oral phase:
- Bolus pushed backwards with tongue until swallow is triggered.
- approx: 1-1.5 seconds
- Begins when tongue begins posterior movement of bolus.
- Tongue tip and sides anchor against alveolar ridge.
- Tongue uses an anterior to posterior action to move bolus back along a central chute/groove (sensory and motor CN V, IX, XII).
- Lips still sealed (CN VII)
- Soft palate still containing bolus in oral cavity, not letting it fall over the base of the tongue (CN V, IX, X, XII)
Stage 3: Pharyngeal phase:
*Pharyngeal swallow triggered and bolus moves through the pharynx
*TRIGGER: Sensory receptors in oropharynx and tongue are stimulated
info sent to cortex and brainstem via nucleus tractus solitarus -> decoded, sent to nulcleus ambiguous, which initiates pharyngeal swallow motor pattern
*Swallow initiated between when bolus head passes anterior faucial arches and point where tongue base crosses mandible.
*Velum elevates and retracts to close off nasal cavity.
*Hyoid elevates and moves anteriorly, pulling larynx up by about 2-3cm, and forwards.
*Up and forwards movement of larynx allows larynx to close, and reduces supraglottic space.
*Laryngeal vestibule and airway protected by: -Retraction of tongue base to anterior bulge of pharyngeal wall and deflection of epiglottis, closure of false vocal folds, closure of true vocal folds, subsequent apnoea
*Progressive contraction of pharyngeal constrictors.
Cricopharyngeal sphincter opens.
*Approx. 1 second duration for phase.
Pharyngeal swallow initiation point:
around point where tongue base crosses mandible in healthy young people, can be as low as at valleculae in older people.
Mechanism of cricopharyngeal sphincter opening:
- Base of tongue (BOT) retracts to posterior pharyngeal wall (PPW).
- This pulls hyoid bone forward and up.
- Hyoid bone elevates the thyroid and cricoid cartilages
- This mechanical traction (combined with bolus force and disinhibition of CN IX and X) pulls open the pharyngeoesophageal segment.
- Bolus then enters the esophagus.
Stage 4: Esophageal phase:
- Bolus is propelled by peristalsis through the esophagus to the stomach.
- Lasts approx. 8 seconds.
- Gastroenterologist role - but being aware of this phase during videofluoroscopy important as impairment of esophageal phase may impact pharyngeal phase.
Insufficient afferent information to swallow centre results in…
Poor communication with respiratory centre in medulla. (imp. because swallowing and respiration can’t co-occur).
people with respiratory issues may have problems swallowing because..
The body will override swallowing function in favour of respiration.
Swallow-respiratory cycle:
- Spoon approaches lips > small exhalation
- Then small inhalation
- Apnoea as swallow happens
- Immediate exhalation post swallow.
If the final exhalation post-swallow doesn’t occur (swallow-respiratory cycle), what might happen?
Can inhale bolus remnants left in pharynx.
Is epiglottic deflection a perfect seal?
No!
Swallow apnoea:
Occurs before bolus enters pharynx and until material cleared from pharynx.
Airway protected during swallow by:
- Epiglottic deflection and closure/narrowing of vestibule.
- False vocal fold closure
- True vocal fold closure
Decreased swallow-respiratory co-ordination can result in aspiration from interaction between:
- Time bolus dwells in pharynx (may not be able to close the respiratory system for long enough, due to need for air)
- Time spent in inspiration
- Abnormality of respiratory rhythm.
How do dysphagic swallow-respiratory cycles differ in patients of differing aetiologies?
- Stroke patterns variable. many take a breath straight after the swallow. Inconsistent individual patterns.
- MND patterns same as health, but multiple rapid swallows for a singe bolus (can’t hold breath long enough).
- Chronic Obstructive Pulmonary Disease: commence in inspiratory phase and inspire after swallow.
Variations in straw drinking:
- Usually multiple sips while airway is open (doesn’t stay open when drinking from cup)
- lip strength to create intraoral pressure.
- examine patient with/without straw. When leaving recommendations, specify straw/no straw.
changes in tongue pressure required for swallowing:
- when food is salty/sweet/acidic.
- Increased for thicker consistencies.
- consider when giving recommendations.
Some variations in swallowing with aging (some people):
- Challenge to determine whether underlying pathological process or just aging.
- Increased age = increased complexity > more likelihood of other problems or medications influencing the swallow.
- Tooth loss
- Tissue and muscular changes in jaw, tongue, salivary glands and throat.
- Decreased salivary glands, reduced taste > decreased appetite, more difficulty chewing, more time taken to eat, change in food choices -> nutritional impact.
- decreased saliva also impacts articulation and oral hygiene.
- decrease reflex speed > increased swallow duration and delays in initiation.
Respiration changes in aging, impacts on speech, swallowing and voice…how?
- Chest wall compliance and elasticity.
- Increased functional residual capacity resulting from decreased elastic recoil of lungs.
- changes in lung and airway structure and ability to function (due to ongoing environmental exposures) -> impact on breathing, therefore communication and swallowing.
- -> interactions between respiration and swallow.
