Airway anatomy

Question 1

pharynx

Answer 1

Oral and nasal cavity come together in the pharynx which is comprised of three sections, nasopharynx, oropharynx, and hypopharynx (laryngeal pharynx)

Question 2

larynx

Answer 2

extends from C3-C6 in the adult and contains 3 paired cartilages (thyroid, epiglottis, and cricoid) and 3 unpaired cartilages (corniculate, arytenoid, and cuneiform).

Question 3

Cricoid cartilage

Answer 3

forms a complete signet ring

Question 4

superior to inferior - epiglottis to cricoid cartilage

Answer 4

epiglottis,
hyoid bone,
thyrohyoid ligament,
thyroid cartilage,
cricothyroid ligament,
cricoid cartilage.

Question 5

cricothyroidotomy

Answer 5

performed at the cricothyroid ligament

Question 6

nasal nerves (sensory)

Answer 6

Anterior 1/3 of the nasal cavity sensory comes from the trigeminal nerve- specifically the
ethmoidal branch of the ophthalmic nerve.

Branches of the maxillary division of the trigeminal nerve from the sphenopalatine
ganglion supply sensory to the nasal septum.

Question 7

oral nerves (Sensory)

Answer 7

The greater and lesser palatine nerves also branch off the sphenopalatine ganglion to supply sensory to the hard and soft palate respectfully.

The trigeminal nerve also splits into the mandibular branch which contains the lingual nerve that supplies sensory to the anterior 2/3 of the tongue.

The rest of the oral cavity and oropharynx up until the anterior side of the epiglottis (vallecula) is supplied by the glossopharyngeal nerve.

Question 8

hypopharynx/larynx (Sensory)

Answer 8

The vagus nerve branches into the superior laryngeal and recurrent laryngeal nerves.

The superior laryngeal nerve further splits into external and internal branches.

The External branch contains no sensory innervation, but the internal branch senses the
posterior side of the epiglottis up until the vocal cords.

The recurrent laryngeal nerves provide innervation to the rest of the larynx and trachea
below the vocal cords.

Recurrent laryngeal nerve comes off from the trachea and goes under the subclavian
artery before coming back up to innervate the larynx. The left and right recurrent laryngeal nerves are asymmetric due to the aortic arch.

Question 9

Motor nerves - Superior laryngeal nerve external division

Answer 9

innervates the cricothyroid muscle which elongates the vocal cords.

Internal branch has NO motor innervation.

Question 10

Motor nerves - recurrent laryngeal nerve

Answer 10

All other muscles in the larynx are motor innervated by the recurrent laryngeal nerve.

Vocalis muscles shorten the vocal cords.

Posterior cricoarytenoids ABDucts the vocal cords whereas lateral cricoarytenoids
ADDucts the vocal cords.

Thyroarytenoid muscle both ADDucts and shortens the vocal cords.

Question 11

Injury to the superior laryngeal nerve

Answer 11

causes hoarseness due to the external branch innervates the cricothyroid muscles which tense the vocal cords.

Question 12

Injury to the recurrent laryngeal nerve

Answer 12

can be further classified as unilateral or bilateral

Left side can be caused by issues to the heart such as left atrial enlargement, ligation, aortic arch aneurysm, and thoracic tumor

Either side can be injured from ETT, LMA, neck surgery, or tumor.

If bilateral injury occurs, all the intrinsic muscles except the cricothyroid muscles will be
paralyzed and can result in stridor due to unopposed tensing of the vocal cords.

Question 13

In order to intubate we need
to align three axes:

Answer 13

oral, pharyngeal, and laryngeal.

Question 14

Assessment of the patient’s airway prior to airway management includes:

Answer 14

history gathering and a physical examination.

Aspects of the history may include a history of the patient’s airway experiences, review of previous anesthetic and medical records, and the gathering of information that may be pertinent such as congenital defects, disease states, and gastrointestinal disorders.

The physical examination should evaluate for features to predict the potential for difficult airway management.

Question 15

Mallampati score

Answer 15

one assessment to describe the relative size of the base of the tongue compared to the oropharyngeal opening in hopes of predicting the difficult airway

Have the patient upright, extend neck, open mouth and stick out tongue. DO NOT phonate.
Examine at eye level.

Graded in 4 classes.
* Class I: Ideally you want to see pillars, uvula, soft and hard palate.
* Class II: cant see pillars
* Class III: can’t see pillars or uvula
* Class IV: cant see pillars, uvula, or soft palate.

Question 16

Submandibular space

Answer 16

Important because it is the space we displace soft tissue to visualize cords. Want a bigger space.

Thyromental distance- estimates size of the submandibular space. From the mentum (chin) to thyroid cartilage. Have the neck extended. Want at least 6 cm (3 fingers) to have good visualization.

Things that limit this space- Ludwig angina, tumors or masses, radiation scarring, burns, and
previous neck surgery are conditions that can decrease submandibular compliance.

Question 17

Upper Lip bite test

Answer 17

Assesses ability to move the mandible forward which allows for better visualization.

The classes of the ULBT are as follows:
* Class I: Lower incisors can bite above the vermilion border of the upper lip.
* Class II: Lower incisors cannot reach the vermilion border.
* Class III: Lower incisors cannot bite upper lip.

Question 18

Incisor Gap

Answer 18

The larger the patient can open their mouth, the more likely you can align the three axes.

Want 2-3 finger breaths between incisors.

Question 19

Atlanto-Occipital Joint Mobility

Answer 19

Ability to extend neck back into sniffing position.

Impaired in patients with rheumatoid arthritis, down syndrome, diabetes, trauma, or surgical
fixation.

Question 20

Summary for difficult intubation

Answer 20

Difficult ventilation if small mouth, short thick neck, Mallampati III or IV, overbite, long incisors, decreased cervical mobility, or high arched palate.

Question 21

Difficult Mask Ventilation

Answer 21

Independent variables associated with difficult face mask ventilation include but are not limited to…
* Age older than 55 years
* Increased body mass index (BMI)
* Facial Hair
* Lack of teeth (Dentures)
* A history of snoring or obstructive sleep apnea,
* Mallampati class III to IV
* Male gender
* Limited ability to protrude the mandible.

Question 22

Blades (Intubation equipment)

Answer 22

The Macintosh blade is curved.
* The advantages of the curved (Macintosh) blade include less trauma to teeth, more room for
passage of the endotracheal tube, larger flange size improves the ability to sweep the tongue,
and less trauma to the soft tissue.
* With a Macintosh blade, the tip of the blade is advanced into the space in the anterior part of the
epiglottis called the vallecula.

Miller blade is straight.
* The advantages of the straight (Miller) blade are better exposure of the glottic opening and a
smaller profile, which can be beneficial in patients with smaller mouth opening.
* With a Miller blade, the tip of the blade is put past the epiglottis. The epiglottis is then elevated
by the blade to expose the glottic opening.

Question 23

ETT

Answer 23

Endotracheal tubes are sized according to their internal diameter (ID), which is marked on each tube. They are available in 0.5 mm ID increments.

Endotracheal tubes are radiopaque so we can view the position on an x-ray.

They are transparent so we can see “fog” from CO2 during exhalation or secretions in the tube.

Microlaryngeal tube- pediatric sized tubed with an adult length- small enough to move side to
side for airway surgeries

Question 24

ETT parts

Answer 24

Cuff
* Allows for pressure ventilation and prevents gastric aspiration into lungs.
* Keep under 25 cm H2O to prevent tracheal ischemia.
* Most tubes use a high-volume, low-pressure cuff b/c it protects from ischemia the best.
* Be careful if using nitrous that the cuff does not overinflate. For this reason, fill the cuff
with the same nitrous mixture that will be used during the case.

Murphy eye- second opening at end of the tube
* Watch that the stylet doesn’t poke through this and damage tissue during intubation

EVAC- subglottic suctioning connection

RAE tube- massive curvature at distal end where it attaches to the ventilator

Question 25

Oral/Nasal Airways

Answer 25

Relieve upper airway obstruction. Displace tongue and epiglottis from posterior wall of pharynx.

Ovassapian or Williams oral airways have the ability to pass fiberoptic intubation through them.

Measure from corner of mouth to the earlobe for sizing of oral airway. Earlobe to the nare for
nasal airway.

Don’t do nasal airway if skull/facial fracture, pregnancy, or coagulopathy. It has increased
bleeding.

Nasal is advantageous b/c it decreases sympathetic stimulation and gagging compared to oral.

Question 26

LMA (laryngeal mask airway)

Answer 26

Supraglottic airway device
* Advantages include quick placement and without the use of a laryngoscope, less coughing and bucking with removal, no muscle relaxants, and less laryngeal trauma.

Keep the cuff less than 60 cm H2O. This is to prevent injury to the airway nerves.

LMA positive pressure ventilation should be less than 20 cm H20 to limit risk of getting air into the stomach.

There are special kinds of LMA’s that have one or more of the following advantages- a second lumen that acts as an esophageal vent to keep gasses and fluid separate from the airway and facilitate placement of an orogastric tube, an airway channel that can be used as a conduit for intubation, and a bite block.

Question 27

LMA contraindications

Answer 27

Contraindications- patients at risk for regurgitation of gastric contents, prone position, obesity, pregnant patients, long surgical time, and intra-abdominal or airway procedures.

Difficult placement associated with small mouth opening, fixed cervical spine deformity, use of cricoid pressure, poor dentition or large incisors, male sex, and increased BMI.

Reported complications of laryngeal mask airway use in difficult airway patients include bronchospasm, postoperative swallowing difficulties, respiratory obstruction, laryngeal nerve injury, edema, and hypoglossal nerve paralysis.

Question 28

Video Laryngoscope

Answer 28

Video laryngoscopes can help obtain a view of the larynx by providing indirect visualization of the glottic opening in patients who have limited mouth opening, inability to flex the neck, or difficult airway anatomy.

There is also a slightly improved view of the larynx because the camera is located more distally on the blade.

Channeled video laryngoscope blades (Airtraq and King Vision) have a guide channel that directs an endotracheal tube toward the glottic opening via blades that are more angulated than
traditional Macintosh blades. The endotracheal tube is placed onto the device prior to insertion of the blade into the mouth, and the video laryngoscope is inserted midline in the mouth until the epiglottis is visualized. Then the ETT can be advanced.

Question 29

Fiber optic endotracheal intubation

Answer 29

In general, the nasal route is easier than the oral route for fiberoptic endotracheal intubation
because the angle of curvature of the nasal cavity better shapes the fiber optic device to view the
glottic opening. Also, the nasal fiberoptic decreases risk for the gag reflex.

A disadvantage of nasal fiberoptic endotracheal intubation is bleeding potential so don’t use this if a patient has coagulation abnormalities.

Question 30

anesthesia during intubation

Answer 30

Topical anesthesia of the tongue and oropharynx may be achieved by spraying or direct application or by bilateral blocks of the glossopharyngeal nerve.

Can use topical anesthesia with lidocaine. Start with spraying the front of the mouth and work back into the oropharynx. Patient inhaling during the spray will increase the numbing effect.

Question 31

glossopharyngeal nerve block

Answer 31

Glossopharyngeal block will block sensation to the posterior third of the tongue and vallecula. This gets rid of gag reflex. Inject 2-5 ml of 2% lidocaine submucosally in the caudal aspect of the posterior tonsillar pillar.

ie approximately 2 mL of 2% lidocaine is injected at a depth of 0.5 cm (after first confirming negative aspiration) at the base of each anterior tonsillar pillar.

Question 32

topical anesthesia

Answer 32

Can use topical anesthesia with lidocaine. Start with spraying the front of the mouth and work back into the oropharynx. Patient inhaling during the spray will increase the numbing effect.

Question 33

Superior laryngeal nerve block

Answer 33

Superior laryngeal nerve block will block sensation to laryngeal structure above the vocal cords. Can block by placing the patient in supine position and extending the neck. Inject 2ml 2% lidocaine to just inferior and lateral to hyoid bone.

Question 34

Recurrent Laryngeal block

Answer 34

Recurrent Laryngeal block will block sensation to vocal cords and trachea. Place supine with neck extended. Inject 5ml of 4% lidocaine through the cricothyroid membrane into the trachea and have the patient cough to numb the airway.