Unit 1 - Airway Anatomy Flashcards
function of intrinsic laryngeal muscles
participate in phonation and control vocal cords (tension and position)
function of extrinsic laryngeal muscles
support larynx inside neck, assist with swallowing
function & innervation of cricothyroid muscle
function: elongates (tenses) vocal cords
- CricoThyroid “Cords Tense”
innervation: SLN extenal branch
function & innervation of vocalis muscle
function: shortens (relaxes) vocal cords
innervation: RLN
function & innervation of thyroarytenoid muscle
function: shortens (relaxes) vocal cords, ADDucts vocal folds (closes glottis)
- ThyroaRytenoid “They Relax”
innervation: RLN
function & innervation of lateral cricoarytenoid muscle
function: ADDucts vocal folds (closes glottis)
- Lateral CricoArytenoid “Lets Close Airway”
innervation: RLN
function & innervation of posterior cricoarytenoid muscle
function: ABducts vocal folds (opens glottis)
- Posterior CricoArytenoid “Please Come Apart”
innervation: RLN
function & innervation of aryepiglottic muscle
function: closes laryngeal vestibule
innervation: RLN
function & innervation of interarytenoid muscles (transverse & oblique)
function: closes posterior commissure of glottis
innervation: RLN
laryngeal muscles that adjust length (tension) of vocal ligaments
- cricothyroid (elongates/tenses)
- vocalis (shortens/relaxes)
- thyroarytenoid (shortens/relaxes)
laryngeal muscles that ABduct or ADDuct vocal folds (glottic diameter)
- thyroarytenoid (ADDucts/narrows glottis)
- lateral cricoarytenoid (ADDucts/narrows glottis)
- posterior cricoarytenoid (ABducts/widens glottis)
laryngeal muscles that control sphincter muscle
- aryepiglottic: closes laryngeal vestibule
- interarytenoid: closes posterior commissure of glottis
extrinsic function of cricothyroid muscles
contraction during swallowing pulls anterior region of cricoid cartilage towards lower border of thyroid cartilage
extrinsic laryngeal muscles
all end in -hyoid except digastric
risk factors for RLN injury
- external pressure from ETT or LMA
- thyroid or parathyroid surgery
- neck stretching
- neoplasm
provides sensory innervation to face
CN 5 (trigeminal n.)
branches of trigeminal nerve
V1 - opthalmic nerve
V2 - maxillary nerve
V3 - mandibular nerve
nerve that innervates the nares and anterior 1/3rd of nasal septum
anterior ethmoidal nerve (branch of V1 opthalmic nerve)
innervates turbinates and posterior 2/3 of nasal septum
sphenopalatine nerve (branch of V2 maxillary nerve)
provides sensory innervation to anterior 2/3 of tongue
V2 maxillary n
provides sensory innervation to posterior 1/3 of tongue, oropharynx, vallecula, and anterior epiglottis
CN IX - glossopharyngeal
afferent limb of gag reflex
CN IX - glossopharyngeal n.
efferent limb of gag reflex
CN X - Vagus n.
what nerve gives rise to SLN and RLN
CN X - vagus
function of internal branch of SLN
sensory innervation to posterior side of epiglottis to the level of vocal folds
function of external branch of SLN
motor innervation to cricothyroid muscle (tenses vocal cords)
symptom of acute injury to SLN trunk or external branch
hoarseness
function of RLN
- sensory innervation below level of vocal folds to the trachea
- motor innervation to all intrinsic laryngeal muscles except cricothyroid
where does the RLN branch off of CN X
- inside thorax
- right RLN: loops under subclavian artery
- left RLN: loops under aortic arch
what part of the RLN is most susceptible to injury and why
left RLN - due to location in thorax
risk factors for left RLN injury
- PDA ligation
- left atrial enlargement (from mitral stenosis)
- aortic arch aneurysm
- thoracic tumor
s/s acute unilateral RLN injury
- paralysis of ipsilateral vocal cord ABductors (unopposed ADDuctor action)
- hoarseness
s/s acute bilateral RLN injury
- bilateral paralysis of vocal cord ABductors
- unopposed tension of cricothyroid
- stridor, respiratory distress (presents similary to laryngospasm)
provides motor innervation to muscles of mastication
V3 - mandibular n. (branch of trigeminal n)
what nerve must be anesthetized to prevent pt from gagging during awake intubation
glossopharyngeal (CN IX)
where does the SLN branch off of the vagus n.
just beyond jugular foramen at skull base
where does the SLN divide into internal and external branches
at level of hyoid
where does the internal SLN branch penetrate thyrohyoid membrane
between greater cornu of hyoid bone and superior horn of thyroid cartilage
most common nerve injury folowing subtotal thyroidectomy
unilateral RLN injury
topical techniques to anesthetize nares
- 4% lidocaine + vasoconstrictor
- cocaine
- topical LA in eacn nare
risk of using viscous lidocaine to anesthetize airway
N/V
risk of 20% benzocaine to anesthetize airway and the treatment
methemoglobinemia
treat with methylene blue
which typically works better to anesthetize airway - nebulization or atomization
atomization
3 techniques to anesthetize vocal cords
- inject LA through nasal airway or ETT just above cords
- “spray as you go” with fiberoptic scope
- inject LA through catheter in suction port of flexible fiberoptic catheter
3 nerves that must be blocked to provide complete anesthesia to airway
- glossopharyngeal n.
- superior laryngea n.
- recurrent laryngeal n.
glossopharyngeal nerve block technique
- insert needle at base of palatoglossal arch (anterior tonsillar pillar) to 0.25-0.5cm
- inject 1-2 mL LA and repeat on contralateral side
glossopharyngeal n. block - what does aspiration of air vs. blood mean
air: needle is too deep
blood: needle should be withdrawn and redirected medially (carotid is close)
risk of glossopharyngeal n block
5% incidence of intracarotid injection - risk of seizure
SLN nerve block
- LA injected at inferior border of greater cornu of hyoid bone
- 1 mL injected outside thyrohyoid membrane, 2 mL injected 2-3 mm deep to membrane
- repeat bilaterally
what does air aspiration during SLN block mean
needle is too deep
RLN block
transtracheal approach:
- puncture cricothyroid membrane, advance needle caudally to reduce risk of vocal cord injury
- have pt take deep breath before aspiration
- during inspiration, inject 3-5 mL LA in tracheal lumen
- pt will cough and spray LA upwards through cords
location of adult larynx (in relation to C spine)
anterior to C3-C6
(infant = C2-C4)
3 primary functions of larynx
- airway protection
- respiration
- phonation
3 unpaired cartilages of the larynx
- epiglottis
- thyroid
- cricoid
serves as the major structural component of the larynx
thyroid
how is the thyroid attached to the hyoid bone
thyrohyoid ligament
forms inferior border of larynx
cricoid
entry point for surgical airway
cricothyroid membrane
only complete cartilaginous ring in the airway
cricoid
3 paired cartilages of the larynx
- arytenoids
- corniculates
- cuneiforms