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APEX Study Guide > Unit 1: Airway Anatomy > Flashcards

Unit 1: Airway Anatomy Flashcards

1
Q

What are the two classifications of laryngeal muscles? What is the function of each?

A

Intrinsic Laryngeal Muscles: control the tension and position of the vocal cords

Extrinsic Laryngeal Muscles: support the larynx inside the neck and assist with swallowing
*all extrinsic muscles (except the digastric) end in “-hyoid”

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2
Q

What nerves innervate the intrinsic laryngeal muscles?

A

Recurrent Laryngeal Nerve – innervates all intrinsic laryngeal muscles except for the cricothyroid muscle

External Branch of Superior Laryngeal Nerve – innervates cricothyroid muscle

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3
Q

What is the function of the cricothyroid muscle?

A

Elongates (tenses) the vocal cords

CricoThyroid : Cords Tense

*innervated by external branch of superior laryngeal nerve

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4
Q

What is the function of the vocalis muscle?

A

Shortens (relaxes) the vocal cords

*innervated by recurrent laryngeal nerve

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5
Q

What is the function of the thyroarytenoid muscle?

A

Shortens (relaxes) the vocal cords
ADDucts vocal cords – closes glottis

ThyroaRytenoid : They Relax

*innervated by recurrent laryngeal nerve

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6
Q

What is the function of the lateral cricoarytenoid muscle?

A

ADDucts vocal cords – closes glottis

Lateral CricoArytenoid : Let’s Close Airway

*innervated by recurrent laryngeal nerve

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7
Q

What is the function of the posterior cricoarytenoid muscle?

A

ABducts vocal cords – opens glottis

Posterior CricoArytenoid : Pull Cords Apart

*innervated by recurrent laryngeal nerve

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8
Q

What is the function of the aryepiglottic muscle?

A

Closes laryngeal vestibule

*innervated by recurrent laryngeal nerve

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9
Q

What is the function of the interarytenoid muscle (transverse and oblique)?

A

Closes posterior commissure of glottis

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10
Q

What is the laryngeal muscular innervation mnemonic SCAR?

A
  • *S**uperior Laryngeal Nerve = Cricoarytenoid Muscles
  • *A**ll Other Muscles = Recurrent Laryngeal Nerve
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11
Q

Where does the trigeminal nerve (CN V) provide sensory innervation? What are the three branches?

A

Trigeminal Nerve (CN V): sensory innervation to face and head

  • V1 (Ophthalmic): nares and anterior ⅓ of nasal septum
  • V2 (Maxillary): turbinates and nasal septum
  • V3 (Mandibular): anterior ⅔ of tongue (somatic); innervates muscles of mastication
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12
Q

Where does the glossopharyngeal (CN IX) provide sensation?

A

From the oropharynx down to the anterior side of the epiglottis

*afferent limb of gag reflex

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13
Q

What nerves does the vagus (CN X) give rise to?

A

Superior Laryngeal Nerve (this divides into the internal and external branches)

Recurrent Laryngeal Nerve

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14
Q

What is the sensory and motor function of the internal and external branches of the superior laryngeal nerve?

A
  • SLN Internal Branch
    • Sensory function = Posterior side of epiglottis (level of the vocal cords)
    • Motor function = None
  • SLN External Branch
    • Sensory function = none
    • Motor function = Cricothyroid Muscle
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15
Q

What is the function of the recurrent laryngeal nerve?

A

Provides sensation below the level of the vocal cords (trachea)

Innervates all intrinsic laryngeal muscles except for the cricothyroid muscle

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16
Q

What occurs if the recurrent laryngeal nerve is paralyzed?

A

It innervates the posterior cricoarytenoid muscle (which pulls the cords apart) and when paralyzed the cord tensing action of the cricothyroid muscle acts unopposed

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17
Q

What is the patient clinical presentation for injury to the recurrent laryngeal nerve?

A

Unilateral RLN Injury → No respiratory distress; Hoarseness

Bilateral RLN Injury (Acute) → Respiratory distress (stridor) due to unopposed action of cricothyroid muscles

Bilateral RLN Injury (Chronic) → No respiratory distress (typically well tolerated)

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18
Q

What are the risk factors for a recurrent laryngeal nerve injury on either side?

A
  • Overinflation of ETT/LMA cuff
  • Tumor
  • Excessive Neck Stretching
  • Neck Surgery (i.e. Thyroidectomy) **Most Common**
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19
Q

What increase the risk for a left sided recurrent laryngeal nerve injury?

A
  • PDA ligation
  • Left atrial enlargement (mitral stenosis)
  • Aortic arch aneurysm
  • Thoracic tumor
20
Q

What is the clinical presentation for a superior laryngeal nerve injury?

A

Bilateral injury can cause hoarseness

*Rarely injured, but if it is, it does NOT cause respiratory distress

21
Q

What must you anesthetize for an awake intubation? What local anesthetic is typically used?

A

Base of the tongue, oropharynx, hypopharynx, and larynx
*anesthetizing the mouth is not required

Benzocaine spray is common
Cocaine can be used (avoid in pt w/ PChE deficiency, on MAOI durgs, or if increase in SNS tone is a problem)

22
Q

What is a key risk of benzocaine spray? How do you treat it?

A

Risk = Methemoglobinemia

Treatment = Methylene Blue

23
Q

What airway nerve blocks can be used to anesthetize the airway for awake intubation?

A

Glossopharyngeal Block

Superior Laryngeal Nerve Block

Transtracheal Block (Recurrent Laryngeal Nerve)

**Must block all 3 nerves

24
Q

How do you perform a glossopharyngeal block?

A
  • Insert needle at base of the palatoglossal arch (anterior tonsillar pillar) to a depth of ¼ - ½ cm
    • aspiration of air → needle is too deep
    • aspiration of blood → withdraw needle and redirect medially (carotid is close)
  • Inject 1-2 mL of local and repeat on other side

*5% incidence of intracarotid injection → seizure risk

25
Q

How do you perform a superior laryngeal nerve block?

A
  • Inject local at the inferior border of the greater cornu of the hyoid bone
    • 1mL outside the thyrohyoid membrane
    • 2mL 2-3cm deep to the thyrohyoid membrane
  • Repeat on other side

*aspiration of air → needle is too deep

26
Q

How do you perform a transtracheal block?

A
  • Insert needle through the cricothyroid membrane (in a caudal direction to reduce risk of VC injury)
  • After aspiration, but before injection, tell pt to take a deep breath
  • Inject 3-5mL of local into tracheal lumen during inspiration
  • Pt will cough, spraying local upward toward the cords
27
Q

What spinal cord level does the adult larynx lie? What are the 3 primary functions?

A

Anterior to C3-C6

Primary Functions: airway protection, respiration, phonation

28
Q

What are the names of the bumps you see on the aryepiglottic folds during laryngoscopy?

A

Corniculates and Cuneiforms

**NOT the arytenoids

29
Q

What is the narrowest region of the adult and pediatric larynx?

A

Adult Larynx: Glottic Opening

Pediatric Larynx:

  • Cricoid Ring (“fixed” region)
  • Vocal Cords (“dynamic” region)
30
Q

What are the components of the larynx?

A
  • Hyoid Bone
  • Thyrohyoid Ligament (Membrane)
  • Cricothyroid Ligament (Membrane)
  • Unpaired Cartilages
    • Epiglottis
    • Thyroid
    • Cricoid (only complete cartilaginous ring in the airway)
  • Paired Cartilages
    • Corniculate
    • Cuneiform
    • Arytenoid
31
Q

What are the complication of laryngospasm?

A
  • Airway Obstruction
  • Negative Pressure Pulmonary Edema
  • Pulmonary Aspiration of Gastric Contents
  • Cardiac Dysrhythmias
  • Cardiac Arrest
  • Death
32
Q

What are the signs of laryngospasm?

A
  • Inspiratory stridor
  • Lower rib flailing
  • Increased diaphragmatic excursion
  • Absent or altered EtCO2 waveform
  • Suprasternal/Supraclavicular retraction during inspiration
  • “Rocking Horse” appearance of chest wall (paradoxical movement)
33
Q

What are the common causes of laryngospasm?

A
  • Airway manipulation (practically during light anesthesia)
  • Airway secretions (saliva or blood)
  • Surgery in the airway
  • Active or recent respiratory tract infection (<2 weeks)
  • Age <1 year
  • GERD
  • Reactive airway disease
  • 2nd hand smoke exposure
  • Hyperventilation/Hypocapnia
34
Q

How do you decrease the risk of laryngospasm?

A
  • Avoid airway manipulation during light anesthesia
  • CPAP 5-10 during inhalation induction/immediately after extubation
  • Remove pharyngeal secretions/blood before extubation
  • Tracheal extubation when deep or fully awake
  • Laryngeal lidocaine
  • IV lidocaine before extubation
35
Q

How do you treat a laryngospams?

A
  1. FiO2 100%
  2. Remove noxious stimulation
  3. Deepen anesthesia
  4. Larson’s maneuver, Chin lift, CPAPA 15-20
  5. Consider SUX
    -Adult/Child: 0.1-1 mg/kg IV or 4 mg/kg IM
    -Neonate/Infant: 2 mg/kg IV or 5 mg/kg IM
    *give atropine 0.2 mg/kg in children <5 yo
36
Q

What is a Valsalva’s maneuver?

A

Exhalation against a closed glottis or obstruction

Example: coughing, bucking, bearing down

Risk: increased pressure in thorax, abdomen, and brain

37
Q

What is a Muller’s maneuver? What’s a risk of this?

A

Inhalation against a closed glottis or obstruction

Example: patient bites down on ETT and take a deep breath

Risk: subatmospheric pressure in the thorax → negative pressure pulmonary edema

38
Q

What are the primary functions of the upper airway?

A

Warming and humidifying inspired air

Filtering particulate matter

Preventing aspiration

39
Q

Relaxation of what muscles cause airway obstruction at:

  • level of the tongue
  • level of soft palate
A

Genioglossus Muscle Relaxation = obstruction at level of the tongue **Most common

Tensor Palatine Muscle Relaxation = obstruction at level of the soft palate

40
Q

What conditions impact airway patency?

A

Conditions that decrease Pharynx Diameter

  • reduced pharyngeal dilator muscle tone
  • negative pressure during inspiration

Conditions that decrease size of Head/Neck

  • increased soft tissue inside the “box” → obesity, large tongue, tonsil/adenoid hypertrophy
  • decreased size of the “box” → small craniofacial structures, craniofacial deformity
41
Q

What are the 3 sets of dilator muscles that hold open the upper airway during the awake state?

A

Tensor Palatine (opens nasopharynx)

Genioglossus (opens oropharynx)

Hyoid Muscles (opens hypopharynx)

42
Q

Describe the anatomy of the trachea
What nerve provides sensory innervation?
Where does the blood supply come from?

A
  • Begins at C6 and Ends at T4-5 at carina
  • 2.5cm wide and 10-13cm long
  • Semi-circular rings open posteriorly
  • Ciliated columnar epithelium
  • Sensory Innervation = Vagus nerve
  • Blood Supply = inferior thyroid artery, superior thyroid artery, bronchial artery, internal thoracic artery
43
Q

Describe the anatomy and characteristics of the carina

A

T4-5

Corresponds w/ Angle of Louis

Ciliated Columnar Epithelium

44
Q

Describe the anatomy and characteristics of the mainstem bronchi

A

Right:

  • 2.5cm long
  • 25* take off
  • explains greater likelihood of right mainstem intubation

Left:

  • 5 cm long
  • 45* take off
  • Cuboidal epithelium

**children up to 3yo → both bronchi take off 55* from long axis of trachea

45
Q

Describe the anatomy and characteristics of the alveoli

A
  • Humans have 300 million by age 9
  • Squamous epithelium
  • Pores of Kohn allow air movement between alveoli
46
Q

What are the functions of the different types of Pneumocytes?

A

Type I: provide surface for gas exchange

  • flat squamous cells
  • cover ~80% of alveolar surface
  • form tight junctions

Type II: produce surfactant

  • resistant to oxygen toxicity
  • capable of cell division
  • can produce type I cells

Type III: are macrophages

  • fight lung infection
  • produce inflammatory response

**Neutrophils are present in the alveoli in smokers and patients w/ acute lung injury

47
Q

What increases as the airway bifurcates? What decreases?

A

Increases: number of airways, cross-sectional area, and muscular layer

Decreases: airflow velocity, amount of cartilage, goblet cells (produce mucus), and ciliated cells (clears mucus)

APEX Study Guide (13 decks)

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