Airway Anatomy Flashcards
List the nine cartilages of the airway
Thyroid Cricoid Epiglottis Pairs: Corniculate Arytenoid Cuneiform
The vestibular folds are known as
False vocal cords
What is the narrowest portion of an adult airway?
Glottis opening (average of 6-9 mm)
What is the narrowest portion of the airway in children?
Just below the cords of the cricoid ring
What is the complete ring of cartilage?
Cricoid cartilage
The cricothyroid membrane is
Relatively AVASCULAR
Emergency airway site- “can’t ventilate, can’t intubate”
The nerve involved with laryngospasm is
Superior laryngeal nerve
What axis are we aligning to perform intubation?
OPL
Oral pharyngeal laryngeal axis
Describe the different mallampati classifications.
Class 0- epiglottis, pillars, uuvula, soft and hard palate
Class 1- pillars, uuvula, soft & hard palate
Class 2- portion of uvula, soft and hard palate
Class 3- soft palate, base of uvula
Class 4- hard palate only
What are the structures of the upper airway?
Nose- leads to nasopharynx; nasal breathing is 2x more resistant than mouth breathing
Mouth- leads to oropharynx
The nose and mouth are separated anteriorly and join posteriorly to form the pharynx
What are the three compartments of the pharynx?
Nasopharynx
oropharynx
hypopharynx
Where is the pharynx located?
extends from posterior aspect of nose to the level of the cricoid cartilage
What is a major source of obstruction in the upper airway?
the tongue
What is the Waldeyer’s Tonsillar ring?
lymphoid tissue ring in the pharynx that is at high risk for bleeding especially with nasal intubation
highly vascular area
The Waldeyer’s tonsillar ring is made up of
Pharyngeal tonsils (aka adenoids)-located in nasopharynx
Palatine tonsils-located in oropharynx
Lingual tonsils- located at base of tongue
The upper esophageal sphincter lies
at the lower edge of the hypopharynx and acts as a barrier to regurgitation in the conscious patient
Where is the hypopharynx?
lies posterior to the larynx and leads to the esophagus
The larynx is located at ____ and is responsible for_____
C3-C6 in adults; organ of phonation and a valve to protect the lower airways
What could distort our view of the cords?
smoke inhalation, mass, swelling
The epiglottis (location)
sits at base of tongue and separates hypopharynx from the larynx and hangs over the laryngeal opening
The epiglottis (role
protects against aspiration by covering the glottis during swallowing
Fast facts about the epiglottis:
broad/leaf shaped
VASCULAR AREA
can be traumatized and swell incredibly
The arytenoids
are a paired cartilage pyramidal in shape posterior cords are attach to them most commonly seen on laryngoscopy
The vestibular folds are known as
the false vocal cords & they are narrow bands of fibrous tissue on each side of the larynx that are found first inside the laryngeal cavity opening
The glottic opening is
a triangular fissure between the vocal cords
The thyroid cartilage is located
in the anterior neck/thyroid notch
largest cartilage of the larynx
vocal cords are attached anteriorly
Where is the cricoid cartilage located?
at the level of C6
Fast facts about the cricothyroid membrane:
relatively AVASCULAR
translaryngeal injection
emergency airway site
thyroid cartilage is attached to the cricoid cartilage anteriorly by the cricothyroid membrane
The thyrohyoid (role)
connects the thyroid cartilage with the hyoid bone
How long is the trachea?
approximately 10-15 cm in length
Where are the tracheal rings located?
composed of 16-20 cartilagenous rings located anteriorly
Where does the trachea bifurcate?
at the level of T5
Right bronchus bifurcates at 25-30 degree angle
Left bronchus bifurcates at 45 degree angle
What is the transition between upper and lower airway
the vocal cords and glottic opening
Where does the trachea begin?
begins at C6 at the inferior border of the cricoid cartilage and extends to the carina
The pediatric airway differs from the adult airway in the following ways:
larynx positioned higher in the neck
tongue larger relative to mouth size
epiglottis larger, stiffer, angled more posteriorly
head & occiput larger relative to body size
short neck
narrow nares
cricoid ring is narrowest region
The intrinsic muscles of the airway
open, close, and control tension of the vocal cords
The extrinsic muscles of the airway
connect the larynx with the hyoid bone and other structures & serve to move the larynx as a whole (elevating and depressing) during phonation, swallowing, and breathing
What is the action of the posterior cricoarytenoid muscle?
abducts (opens) the vocal cords and opens the glottis)
What is the action of the lateral cricoarytenoid muscle?
adducts (closes) the vocal cords
What is the action of the arytenoid muscle?
adducts the vocal cords
What is the action of the cricothyroid muscle?
produces cord tension, closure, and elongates the vocal cords; can result in total and profound glottic closure called laryngospasm
What is the action of the thyroarytenoid muscle?
shortens and relaxes the vocal cords
The extrinsic muscles of the larynx include:
Sternohyoid, sternothyroid, thyrohyoid, omohyoid, stylohyoid, mylohyoid
The intrinsic muscles of the larynx include:
posterior cricoarytenoid, lateral cricoarytenoid, arytenoids, cricothyroid, thyroarytenoid
What is the action of the sternohyoid muscle?
draws hyoid bone inferiorly
What is the action of the sternothryoid muscle?
draws thyroid cartilage caudad
What is the action of the thyrohyoid muscle?
draws hyoid bone inferiorly
What is the action of the omohyoid muscle?
draws hyoid bone caudad
What is the action of the stylohyoid muscle?
elevates the larynx
What is the action of the mylohyoid
elevates the larynx
A concern with the nasal area is that
PSNS stimulation (seen with anesthesia) results in engorgement of blood vessels & increases likelihood of bleeding with airway manipulation
What cranial nerves innervate the tongue?
anterior 2/3rds: lingual nerve of trigeminal nerve
Posterior 1/3rd: glossopharyngeal nerve
What cranial nerve innervates the tonsils, roof of pharynx, and underside of soft palate?
glossopharyngeal nerve
The facial nerve is responsible for
supplying muscles of facial expression
taste to anterior 2/3rds of tongue
motor control of stylohyoid laryngeal muscle
salivary gland production
small amount of afferent conduction to oropharynx
The hypoglossal nerve is responsible for
providing motor innervation to most muscles of the tongue
damage to the hypoglossal nerve can relax the tongue causing it to fall back and cause airway obstruction
The vagus nerve innervates airway
below the epiglottis
The vagus nerve has two pertinent branches:
superior laryngeal nerve & recurrent laryngeal nerve
The recurrent laryngeal nerve provides
sensation to larynx below vocal cords and to upper esophagus
The superior laryngeal nerve provides
internal branch-sensation to larynx from epiglottis to vocal cords (sensation ABOVE vocal cords)
(SIS- superior internal sensory)
external branch is a motor nerve
(SEM- superior external motor)
Which nerve is responsible for laryngospasm?
Superior laryngeal nerve
The recurrent laryngeal nerve provides motor to
muscles of the larynx except for the cricothyroid muscle
The external branch of the superior laryngeal nerve provides motor innervation to
the cricothyroid muscle
Superior laryngeal nerve damage
unilateral: minimal effects
bilateral: hoarseness, vocal tiring
Recurrent laryngeal nerve damage
unilateral: hoarseness
Bilateral: acute- stridor, respiratory distress from unopposed tension of the cricothyroid muscle
chronic: aphonia
Vagus nerve injury can cause
flaccid, midpositioned cords resulting in aphonia
The laryngeal blood supply is made up of the
superior laryngeal artery & inferior laryngeal artery
The superior laryngeal artery supplies blood to
supraglottic laryngeal structures
carotid to the superior thyroid artery to SLA
The inferior laryngeal artery supplies blood to
infraglottic laryngeal structures
subclavian to inferior thyroid artery to ILA
If considering nasal intubation,
should assess for nostril size and patency
Risk factors for difficult airways include
large beards, morbid obesity, OSA, cervical collars, traction devices, external trauma, hoarseness, stridor, shortness of breath, trach scar
What is normal neck extension & what degree makes for difficult intubation?
normal is 35 degrees
>2/3rds decrease (~11 degrees) is associated with a grade III to IV laryngoscopic view
The distance between incisors in adults with mouth fully open should be
30-40 mm (2 large fingerbreaths)
Mandibular movement (upper lip bite test) is important to indicate
the available space for the tongue to be displaced anteriorly during laryngoscopy
The sternomental distance measures
the distance between sternal notch and mentum
distance less than 13.5 cm is suggestive of intubation difficulty
The laryngoscopic view grade 1:
full view of glottic opening
The laryngoscopic grade 2 view:
posterior portion of glottic opening and arytenoid cartilage is visible
The laryngoscopic grade 3 view:
only tip of epiglottis is vissible
The laryngoscopic grade 4 view:
soft palate visible; no recognizable laryngeal structures
What are the components that protect the lower airway from aspiration of foreign bodies and secretions?
pharynx, epiglottis, vocal cords
epiglottis covers laryngeal inlet during swallowing
A laryngospasm is a
prolonged, intense glottic closure and an exaggeration of glottic closure reflex
Laryngospasm results from
direct glottic or supraglottic stimulation, secretions, foreign bodies, inhalational agents, and other noxious stimuli
Treatment for laryngospasm
depends on severity of laryngospasm: remove the stimulus, CPAP for mild, incomplete glottic closure, deepen anesthetic, muscle relaxants and intubation necessary for more severe cases
An additional important protective mechanism of the airway is
coughing because it expels secretions and foreign bodies from upper or lower respiratory tract
What does lemon stand for
look externally, evaluate the mandibular space, mallampati classification, neck mobility
Predictors for difficult mask ventilation include
MOANS: mask seal, obesity (>26 kg/m2), aged >55, no teeth, and snores
facial edema, prominent nares, receding jaw, drainage tubes, tumors/infections
Treatment for upper airway obstruction includes
placement of oropharyngeal or nasopharyngeal airway, treatment depends on cause of obstruction (soft tissue, foreign body, tumor, laryngospasm); soft tissue obstruction treated by head-tilt, chin-lift maneuver or by jaw thrust
A partial upper airway obstruction is characterized by
diminished tidal exchange, retractions of upper chest, snoring sound heard with pharyngeal obstruction, inspiratory stridor heard with laryngeal obstruction
A complete upper airway obstruction is characterized by
lack of any air movement or breath sounds; may observe diaphragmatic tugging or paradoxical movements of abdomen and rib cage
Basic airway equipment includes:
suction, oral & nasal airways, face mask, laryngoscope handles and blades, multiple sizes of ET tubes with stylets, pilot balloon checked; O2 supply & ambu bag
Oral airway placement
follows curvature of the tongue and lifts tongue and epiglottis away from posterior pharyngeal wall, preventing obstruction
wrong size can worsen obstruction
The phalange of the oral airway
sits outside of the lips
Common sizes of oral airways include
80 mm-100 mm
Oral airway considerations:
not well tolerated in lightly anesthetized patient as it may provoke gag reflex, cough, vomiting, laryngospasm, or bronchospasm
It is NOT associated with increased incidence of sore throat or bacteremia
Nasal airways are beneficial in patients
who are awake or lightly anesthetized as it provokes less airway stimulation than hard oral airways
Clinical uses of nasal airways include:
relieve upper airway obstruction, facilitation of pharyngeal suctioning, nasal dilation for nasal intubation, fiberoptic guide
Nasal airways are
artificial airways that pass through the nose, go behind the tongue and rest just above the epiglottis
Relative contraindications to nasal airways include
coagulopathy or hemorrhagic disorders, anticoagulant therapy, pregnancy, basilar skull fractures, nasal infections, deformities of nose, history of nosebleeds requiring treatment
Complications of oral and nasal airways include:
airway obstruction, tongue/soft tissue damage, CNS trauma, uvula edema, dental damage, laryngospasm, coughing, ulceration/necrosis, latex allergy
Face masks components include
body, seal, and connector (fitting with a 22 mm internal diameter)
When sizing face masks,
the smallest mask that works is the correct size because it has the least dead space, is easier to hold, and has less risk for eye injury
When utilizing a mask-ventilation hand positioning should
avoid fingers on soft tissue
C & E shape
downward displacement of the mask with the thumb and first finger
Upward displacement of the mandible with the other three fingers, with little finger at angle of mandible
What are reasons why mask ventilation may be ineffective?
obstruction, laryngospasm, foreign body, and poor technique
Advantages to face mask include
low incidence of sore throat, less anesthetic depth needed, no muscle relaxants necessary, cost efficient for short cases
Disadvantages to face mask include
hands are “tied up”, user fatigue, higher FGF, more difficulty in maintaining airway versus LMA, unprotected airway
Complications of face mask include
skin problems, nerve injury, aspiration, eye injury (blindness from occlusion of retinal artery), movement of cervical spine, latex allergy, environmental pollution, lack of correlation between PaCO2 and ETCO2 due to dilution from high FGF
A laryngeal mask airway
is a supraglottic airway device designed to secure the airway by providing a circumferential seal around the laryngeal inlet with an inflatable cuff
allows for spontaneous or assisted ventilation
The aperture bars of the LMA
prevent epiglottis from obstructing the mask
LMA size 3 stats
patient weight: 30-50 kg, cuff volume test: 30 cc, maximum cuff volume: 20 c, largest ETT 6.0
LMA size 4 stats
patient weight: 50-70 kg, cuff volume test: 45 cc, maximum cuff volume: 30 cc, largest ETT 6.0
LMA size 5 stats
patient weight: 70-99 kg, cuff volume test: 60 cc, maximum cuff volume: 40 cc, largest ETT 7.0
The LMA connector diameter is
15 mm
When placing a LMA
lubricate posterior surface of cuff
airway reflexes must be obtunded before inserted is attempted
When ventilating using a LMA, airway pressures should
not exceed 20 cmH20
Problems with LMA insertion include
mask tipping over on itself, airway obstruction if it pushes epiglottis to a down-folded position,
Contraindications for use of LMA:
aspiration risk, patients with delayed gastric emptying, hiatal hernia, morbidly obese, >14 weeks pregnant, glottic or subglottic obstruction, limited mouth opening, trauma, acute abdomen, thoracic injury, patients with fixed decreased pulmonary compliance, peak airway pressures > 20 cmH20, patients who cannot adequately answer questions regarding medical history
Adverse effects of LMA include
aspiration of gastric contents, sore throat, hypoglossal nerve injury, tongue cyanosis, vocal cord paralysis
Indications for endotracheal intubation include
risk of aspiration, head/neck procedures, intracranial or intrathoracic procedures, intraabdominal procedures, procedures requiring mechanical ventilation, airway anomalies, positioning where airway is unavailable to anesthesia
ET tubes are made up of ____ and come in ____ sizes
polyvinyl chloride (PVC) & are numbered according to internal diameter 2.5 mm to 9.0 mm (half sizes)
Size selection & depth of insertion for ET tubes for men
men: 8.0 or 9.0; 24-26 ATL
Size selection & depth of insertion for ETT for women
7.0-8.0; 20-22 cm ATL
Size selection & depth of insertion for ETT for children:
size: 4 + age/4
depth: 12 + age/2
What factors increase resistance in the ETT?
increased length and decreased radius
What is the cuff pressure in the ETT?
cuff pressure 20-25 mmHg recommended because tracheal mucosal perfusion pressure= 25-30 mmHg
Describe a MacIntosh blade
C shaped, tip is advanced to valleculae for an indirect lift of the epiglottis
Describe a Miller blade
straight or L shaped, lifts epiglottis, less force & head extension needed… requires more skill
Equipment needed for oral tracheal intubation:
laryngoscope handle x 2, blade x 2, oral airways, oral ETT x 2 w/ stylet, tape to secure, suction, stethoscope, backup airway plan
When preparing for laryngoscopy, it is necessary to
optimize patient positioning, raise OR table, adequately preoxygenate, obtund airway reflexes, assess for ability to mask ventilate when appropriate
Steps for performing laryngoscopy
open mouth with right hand (scissors technique), hold laryngoscope with left hand, insert blade into right side of patient’s mouth & sweep tongue to the left, sweep patient’s lips, lift upward and forward, remove stylet after ETT passes through cords, inflate cuff & verify placement
Where should the cuff sit in the airway?
midpoint between vocal cords and carina
How much depth needs to be added with nasal intubations?
3-4 cm.
Position changes that can result in depth of tube change
Advance or withdraw 1.9 cm with head flexion and extension respectively
can move 0.7 cm with rotation of head
Confirming ETT placement includes
absence of stomach gurgling sound made by air entering the stomach, equal bilateral breath sounds over the lungs, fogging of the ETT, refilling of the vent bag, presence of ETCO2 on three consecutive breaths, direct visualization of the ETT cuff passing the vocal cords
Diagnosis of esophageal intubation includes:
gastric contents in ETT, ETCO2 waveform, reservoir bag collapses due to no return of airway gases, auscultation, gastric distension, absence of chest wall motion
Physiologic responses to laryngoscopy and intubation include
htn, tachy or reflex bradycardia, arrhythmias, MI, increased IOP, increased ICP, bronchospasm
complications of laryngoscopy & intubation include
upper airway edema, vocal cord dysfunction, vocal cord granuloma, arytenoid dislocation, glottic & subglottic granulation tissue leading to tracheal stenosis, aspiration, laryngospasm, bronchospasm, coughing, eye injury, CV changes, hypoxemia and hypercarbia, bleeding, submucosal dissection, esophageal intubation, damage to ETT cuff, C-spine injury, dental injury, damage to soft tissue and nerves
Failures of direct laryngoscopy include
poor patient positioning, poor technique (inexperience, ego), inadequate preop assessment, poor preparation, backup techniques not available and ready, adjunct measures not utilized
Extubation deep versus awake
awake: pt is able to maintain & protect airway, purposeful movement, eye opening, reaction to suctioning
deep: muscle relaxants fully reversed, pt spontaneously breathing with adequate minute ventilate, no response to suctioning
When extubating, provide
100% O2, suction oropharynx and hypopharynx, close APL to 70, deflate cuff, remove ETT while applying positive pressure on bag, apply positive pressure and 100% FM immediately following extubation
Subjective criteria for “awake” extubation includes
follows commands, clear oropharynx, intact, gag reflex, sustained head lift for 5 seconds, sustained hand grasp, adequate pain control, minimal end expiratory concentration of inhaled anesthetics ,
Objective criteria for “awake” extubation includes
vital capacity >15 mL/kg, peak voluntary negative inspiratory pressure >25 cm H20, tidal volume >6 mL/kg, sustained tetanic contraction, SpO2 >90%, RR <35, PaCO2 <45
Causes of ventilatory compromise during tracheal extubation
residual anesthetic, poor central respiratory effort, decrease respiratory drive in response to CO2 or O2, reduced tone of upper airway musculature, reduced gag and swallow reflex, surgical airway edema/compromise, vocal cord paralysis, subglottic edema, laryngospasm, bronchospasm
Acute complications after extubation
laryngospasm, vomiting, aspiration, sore throat, hoarseness, laryngeal edema, subglottic edema
Chronic complications after extubation
mucosal ulceration, tracheitis, tracheal stenosis, vocal cord paralysis, arytenoid cartilage dislocation (leads to flaccid cords & airway edema)
Challenges of immediate reintubation
known difficult airway, surgical distortion, limited access, edema, uncooperative, combative patient, emergent nature, blood and secretions, poor oxygenation and ventilation, occurrence during transport, unavailability of equipment
Indications for nasal intubation
maxillofacial or mandibular surgery
oral/dental surgery
Contraindications for nasal intubation
coagulopathy, basilar skull fracture, severe intranasal disorder, CSF leak, extensive facial fractures
Equipment needed for nasal tracheal intubation
laryngoscope handle x2, laryngoscope blades x2, magill forceps, oral airways, nasal airways, neosynephrine spray, nasal tubes x2, tape, suction, stethoscope, backup airway plan
Complications of nasal intubation include
epistaxis, tracheal or esophageal trauma, displaced adenoids or polyps, resulting in bleeding and airway obstruction, bacteremia, sinusitis (seen with long-term NT intubation)
Management of the difficult airway:
cannot ventilate- cannot cause a life-sustaining amount of gas exchange to occur with a jaw thrust and/or OPAW/NPAW
cannot intubate- cannot place ETT through the vocal cords within a life-sustaining period of time
Causes of inability to ventilate:
laryngospasm- nerve injury; light anesthesia
Supraglottic tissue relaxation- tongue, epiglottis, soft palate & pharyngeal walls
Chest wall rigidity- breath holding, narcotic induced
Pathologic glottic and subglottic- foreign body, edema, infection, vocal cord palsy, stenosis, compression
Equipment failure
A Fastrach LMA
is an intubating LMA
comes in sizes 3, 4 & 5 and can accommodate up to an 8.0 ETT
A glidescope is
a video laryngoscope with integrated high resolution camera
clinical uses: known difficulty airway, “rescue”, anterior larynx, limited neck mobility
Indications for a fiberoptic intubation include
assessment of double lumen ETT placement, airway evaluation, placement of ETT for difficult airway or patient with C-spine precautions
Disadvantages of fiberoptic intubation
fragile and expensive, difficult to use, requires more time and experience, blood or secretions impede view
Reasons for failed fiberoptic intubation
inadequate anesthesia, intraoperative laryngospasm or bronchospasm due to inadequate anesthesia, visualization obscured by blood, secretions, or edema, inexperienced provider (most common)
A bullard scope is a
rigid laryngoscope anatomically shaped scope with fiberoptic bundle and eyepiece extending at a 45 degree angle from handle
useful in difficult airways
expensive; slow learning curve
A Wu scope is a
rigid anatomically shaped blade with separate flexible fiberoptic scope, allows for O2 and suctioning during intubation, slow learning curve; parts must be assembled to use
A upsher scope is a
rigid blade shaped in form of oropharynx with attached eyepiece
considerations similar to that for Bullard and Wu scope
A lightwand
allows for trans-illumination of the neck to guide ETT
larynx not directly visualized
A bougie is
a 60 cm long, angled at 40 degrees tip
useful when laryngoscopic view is poor (grade 3 and IV)
A combitube is a
supraglottic airway device
used in the emergency airway
two lumens so can function whether it is placed in the esophagus or trachea
A transtracheal jet ventilation requires
high pressure O2 source (~50 psi)
tidal volume dependent on: inspiratory time, chest wall, and lung compliance
catheter size 14g catheter~1600 mL/s
16g catheter ~500mL/s
Complications with transtracheal jet ventilation include
tracheal mucosal damage and thickened secretions blocking the airway, resulting from inadequate humidification of inspired gases ** most common
tracheal & esophageal rupture, hematoma, failure to adequately ventilate, inadequate delivery of anesthetic gases, pneumothorax, pneumomediastinum, subcutaneous emphysema, barotrauma
Retrograde intubation is
when a puncture is created with an 18g needle in the cricothyroid membrane and is directed cephalad at 45 degree angle; thread J-wire thru needle and out through mouth
follow ETT over wire guide into trachea
Cricothyrotomy complications
pneumothorax, subcutaneous emphysema, bleeding, esophageal puncture, aspiration, respiratory acidosis
Cricothyrotomy pearls
12-14g needle, 3 ml syringe- no plunger, 15 mm ETT adaptor from 7.0 tube, breathing circuit, TTJV
