Airway Management - Key Terms (Vocabulary Flashcards)

AIRWAY MANAGEMENT NOTES

• Scope: Comprehensive overview of airway anatomy, assessment, ventilation concepts, devices, techniques, and emergencies as presented in the transcript.

• Use these notes to study anatomy, landmarks, algorithms, and practical steps for management of the airway in adults (with pediatric notes where applicable).

UPPER VS LOWER AIRWAY ANATOMY

• The airway is divided into upper and lower sections; the cricoid cartilage separates the two.

• UPPER AIRWAY includes: Nose, Mouth, Pharynx, Larynx, Cricoid cartilage.

• LOWER AIRWAY includes: Trachea, Bronchi, Bronchioles, Alveoli.

• Trachea origin: inferior border of the cricoid cartilage; extends to the carina; length ≈ 10-20\,\text{cm}.

• Cricoid cartilage: the only complete ring in the trachea; most other rings are C-shaped.

• Carina: cartilaginous ring that separates the right and left main bronchi; highly sensitive to stimulation (internal laryngeal nerve, a branch of the SLN).

• Right main bronchus: angle of bifurcation ≈ 25-30^{\circ}, length ≈ 2.5\,\text{cm} from the carina.

• Left main bronchus: angle of bifurcation ≈ 45^{\circ}, length ≈ 5\,\text{cm} from the carina.

NERVES AND SENSORY/MOTOR INNERVATION OF THE AIRWAY

• Glossopharyngeal (CN IX): sensory innervation to oropharynx, soft palate, tonsils, posterior 1/3 of tongue, vallecula, anterior epiglottis; afferent limb of gag reflex. Motor: swallowing/phonation.

• Vagus (CN X): innervates larynx; divides into:

  • Superior Laryngeal Nerve (SLN): Internal (sensory above vocal cords including base of tongue, epiglottis, aryepiglottic folds, arytenoids) and External (motor to cricothyroid).

  • Recurrent Laryngeal Nerve (RLN): motor to all intrinsic laryngeal muscles except cricothyroid; sensory below vocal cords & trachea.

• Trigeminal (CN V): nasal cavity innervation via V1 (ophthalmic) and V2 (maxillary); V3 (mandibular) provides mastication; importantly contributes to oropharyngeal sensation.

• Summary memory aid: SRN ( Superior Laryngeal Nerve) primarily CT muscle motor; all other intrinsic laryngeal muscles are RLN; sensory above cords is SLN internal branch; below cords sensory via RLN.

LARYNGEAL ANATOMY AND MUSCLES

• Larynx extends from epiglottis to cricoid cartilage; three unpaired cartilages: thyroid, cricoid, epiglottis; three paired cartilages: arytenoid, corniculate, cuneiform.

• Hyoid bone: anchor for larynx; only bone that does not articulate with another bone.

• Ligaments:

  • Thyroid Ligament (membrane): attaches larynx to hyoid bone.

  • Cricothyroid Ligament (membrane): attaches cricoid to thyroid cartilages; cricothyroidotomy access (emergency airway) and transtracheal block for RLN anesthesia.

• Unpaired cartilage details:

  • Epiglottis: mechanical barrier; vallecula is space between base of tongue and anterior epiglottis (MAC blade sits here).

  • Thyroid cartilage: largest cartilage; forms Adam’s apple.

  • Cricoid cartilage: complete ring;唯一完全环状软骨。

• Paired cartilages: arytenoids (pivotal for glottic opening), corniculate, cuneiform (structural support of aryepiglottic folds; not typically tested; arytenoids not visible on direct laryngoscopy).

• Intrinsic vs extrinsic muscles:

  • Intrinsic: adjust vocal cord length/tlexion and adduction/abduction; innervation: SLN external (cricothyroid) and RLN (all other intrinsic muscles).

  • Extrinsic: depress/elevate larynx (e.g., omohyoid, sternohyoid, sternothyroid, digastric, mylohyoid, stylohyoid, thyrohyoid).

• Clinical note: Many laryngeal structures contribute to protection from aspiration (gag/ cough), maintain patency, and enable phonation.

INNERVATION-BASED FUNCTIONAL INSIGHT

• SLN vs RLN functions summarized:

  • SLN external branch: motor to cricothyroid (tense vocal cords).

  • RLN: motor to all intrinsic laryngeal muscles except cricothyroid (abduction and adduction of vocal cords).

  • Intrinsic muscles controlling vocal cords: ab/adduction, tension.

• Practical takeaway: Remember SCAR mnemonic – Superior laryngeal nerve supplies cricothyroid; all other intrinsic muscles innervated by RLN.

LARYNGEAL MUSCLE ACTION (INTRINSIC) – TENSION, AB/ADDUCTORS

• Tension/shortening/relaxation:

  • Cricothyroid: tense cords (decreases distance between cricoid and thyroid to lengthen cords) – SLN external.

  • Thyroarytenoid: relaxes cords and shortens the glottic length.

  • The remaining intrinsic muscles (thyroarytenoid, lateral cricoarytenoid, posterior cricoarytenoid) contribute to abduction/adduction:

  • Posterior cricoarytenoid: abducts vocal cords (opens glottis).

  • Lateral cricoarytenoid: adducts vocal cords (narrows glottis).

• Sphincter functions: aryepiglottic and interarytenoid muscles contribute to closing the laryngeal vestibule and posterior glottic region.

• Note: True vocal cords are ligaments and not directly innervated; nerve supply is to muscles that control them.

• Visual shorthand: BURP maneuver (Backwards, Upwards, Rightward Pressure) can improve glottic view by manipulating thyroid cartilage.

LARYNGEAL ASSESSMENT AND VIEWS (DL vs DL-Alternative)

• Direct laryngoscopy (DL) vs video-assisted laryngoscopy (VAL): DL uses traditional blades (Mac or Miller) to expose glottis; VAL uses video camera to visualize structures not seen with DL.

• Blade types:

  • Macintosh blade: indirect glottic exposure via anterior force on the hyoepiglottic ligament in the vallecula.

  • Miller blade: direct epiglottis elevation.

• BURP maneuver can improve glottic view during DL.

• Video laryngoscopy advantages: better view in anterior airways, less cervical motion, useful for C-spine precautions.

• Common complications of VAL include pharyngeal injury, larger blade size, potential difficulty advancing ETT due to hand-eye coordination, fogging, or secretions.

AIRWAY ASSESSMENT AND PREDICTORS OF DIFFICULTY

• Mallampati classification assesses oropharyngeal space; larger tongue relative to mouth reduces DL space.

  • Class 1: pillars, uvula, soft palate, hard palate visible.

  • Class 2: uvula, soft palate, hard palate visible.

  • Class 3: soft palate, hard palate visible.

  • Class 4: only hard palate visible.

• Mallampati 3–4 predicts more difficult intubation, but is not a standalone predictor for difficult airway.

• Inter-incisor gap (mouth opening): normal ≈ 4-6\,\text{cm} (2-3 fingerbreadths).

  • Small gap makes aligning oral, pharyngeal, laryngeal axes harder; dental injury risk with buck teeth.

  • Limitations due to arthritis, scar tissue, TMJ disease.

• Inter-incisor considerations: large incisors can complicate DL; short incisor length may predict difficult DL.

• Thyromental distance (estimate submandibular space): less than 6\,\text{cm} (≈ 3 fingerbreadths) suggests possible difficult airway; thyroid notch to hyoid bone distance ≈ 2\,\text{fingerbreadths}.

• 3-3-2 assessment:

  • A) Mouth opening: 3\text{ fingerbreadths}.

  • B) Thyromental distance: 3\text{ fingerbreadths}.

  • C) Thyroid notch to hyoid distance: 2\text{ fingerbreadths}.

• Mandibular protrusion test (Bulldog): assesses TMJ function; sublux jaw and compare incisor relation:

  • Class 1: lower incisor past upper incisor and can touch vermilion border.

  • Class 2: lower incisor in line with upper incisor.

  • Class 3: cannot move lower incisor past upper incisor; increased risk of difficult intubation.

• Atlanto-occipital (AO) joint mobility and sniffing position: mobility affects ability to align axes; normal AO flexion/extension ≈ 90-165^{\circ}.

• Factors reducing AO mobility: degenerative disease, rheumatoid arthritis, ankylosing spondylitis, trauma, cervical surgery, Down syndrome, etc.

PREOPERATIVE PREPARATION AND VENTILATION

• Preoxygenation (denitrogenation): aim for FiO2 ≥ 0.90 and a tight mask seal; produce a well-defined EtCO2 waveform.

• A functional FRC can provide up to ≈ 8\ \text{minutes} of oxygenation during apnea.

• Technique: 8 large breaths in one minute; or 3 minutes of 100% O2 with normal breaths if mask seal is poor.

• The goal is to maximize pulmonary O2 content and reduce nitrogen in FRC to delay desaturation.

AIRWAY DEVICES AND MANAGEMENT OPTIONS

• Endotracheal tube (ETT): cuff inflation occludes trachea; enables positive pressure ventilation and protects from aspiration.

• ETT cuffs: high-volume, low-pressure; cuff pressure should be < 25\ \text{cm H2O} to minimize tracheal ischemia.

• Murphy’s eye: additional opening to prevent occlusion if the tip is blocked.

• NIMs (neuro-muscular blockade monitoring) tubes are specialized tubes used in thyroid cases.

• Oral and oral/nasal RAE tubes are options depending on surgical field.

• Supraglottic devices (SGD): most common is the laryngeal mask airway (LMA).

  • Uses: primary airway, rescue airway, or conduit for tracheal intubation.

  • Design: curved airway connected to a mask; two aperture bars prevent epiglottis obstruction; cuff inflation creates a seal.

  • Ventilation: can ventilate through SGD; max airway pressure ≈ 20\ \text{cm H2O}.

  • Indications/contraindications: full stomach risks (RSI), hiatal hernia, GERD, small bowel obstruction, poor lung compliance, etc. Inadequate seal or leak may be corrected by repositioning; if not, consider ETT.

• LMAs types and features:

  • Fastrach: intubating LMA; can facilitate intubation; uses a tube pusher; built-in bite block and gastric suction option (requires passing an orogastric tube).

  • I-GEL: cuffless, used in situations like EBUS bronchoscopy; allows high O2 flow; no inflatable cuff.

• Video-assisted laryngoscopy (VAL): GlideScope and other videolaryngoscopes; 60° anterior bend supports anterior airways; reduced cervical motion; potential issues include fogging, blood/secretions on blade, hand-eye coordination challenges.

• If airway visualization is difficult with conventional DL, consider DL alternatives (MAC/Miller, BURP) and adjuncts (stylets, bougies, lighted stylets, retrograde techniques).

• Intubating stylet (Eschmann bougie): facilitates DL or DL-adjunct intubation when glottic view is limited (Class 2b or 3); feel tracheal rings; then advance ETT over bougie.

• Lighted stylet: blind intubation technique; ETT advances over a bright light that indicates tracheal location; if in esophagus, light is less bright.

• Facial/head positioning after intubation: tip of ETT moves with head/neck position; nasal-to-chest moves tip toward carina ~2\ \text{cm}; nose-away-chest moves away ~-2\ \text{cm}; lateral head rotation moves tip slightly away (<1\ \text{cm}).

DIFFICULT AIRWAY ALGORITHM (ASA)

• Step 1: Assess likelihood and impact of basic problems: Difficult Ventilation, Difficult Intubation, Cooperation/Consent issues, Difficult Tracheostomy.

• Step 2: Ensure supplemental oxygen remains available throughout airway management.

• Step 3: Compare options for basic management: Awake intubation vs non-invasive intubation vs invasive airway access; preserve spontaneous ventilation when feasible.

• Step 4: Develop primary and alternative strategies, including:

  • Awake intubation path if indicated.

  • Paths if face mask ventilation is adequate or inadequate; LMA/SGD as intermediary.

  • If ventilation becomes inadequate after multiple attempts, escalate to invasive airway access.

  • Non-invasive approaches include different blades, LMA as an intubation conduit, fiberoptic-guided techniques, intubating stylets, light wands, retrograde or blind techniques.

  • Invasive options include cricothyrotomy or tracheostomy.

• When to awaken patient or switch pathways is outlined, including emergency pathways if ventilation becomes inadequate.

• Key: Confirm tracheal intubation, LMA placement, or ventilation with exhaled CO2 whenever a new airway device is placed.

• Emergency non-invasive strategies may include rigid bronchoscope, esophageal-tracheal combitube ventilation, transtracheal jet ventilation.

• ASA DSASA guidelines emphasize limiting attempts to 3 per airway class, with a potential one additional attempt by a more experienced provider. See page 53.

ADULT VERSUS PEDIATRIC AIRWAY

• ADULTS: airway shaped like a cylinder; glottic opening is the narrowest region.

• PEDIATRICS (<5 years): airway shaped like a funnel; the narrowest fixed region is the cricoid ring (does not stretch); the narrowest dynamic region is the vocal cords (will stretch).

• Implication: pediatric airways may require different DL strategies, special devices, and more careful management to avoid subglottic edema and obstruction.

LARYNGOSPASM: RISK, SIGNS, AND TREATMENT

• Laryngospasm: sustained, involuntary contraction of laryngeal muscles causing ventilation inability.

• Complications: airway obstruction, negative pressure pulmonary edema, aspiration, arrhythmias, cardiac arrest, death.

• Signs:

  • Inspiratory stridor

  • Suprasternal/supraclavicular retractions during inspiration

  • Rocking-horse or paradoxical chest movements

  • Increased diaphragmatic excursion

  • Lower rib flailing

  • Absent or altered EtCO2 waveform

• Risk factors (pre-anesthetic and intraoperative): active URI (<2 weeks), secondhand smoke, reactive airway disease, GERD, age < 1 year; intraop factors include light anesthesia during airway manipulation, saliva/blood, hyperventilation/hypocapnia, airway surgeries (tonsillectomy, adenoidectomy, nasal/sinus, laryngoscopy, bronchoscopy, palatal procedures).

• Treatment:

  • 100% FiO2

  • Stop noxious stimulation

  • Deepen anesthesia with propofol or inhaled agents (if not complete laryngospasm)

  • CPAP 15–20 cm H2O to open airway while maintaining opening

  • Larson’s maneuver: apply firm pressure to laryngospasm notch (earlobe region) to displace mandible forward, sometimes allowing a sigh to break spasm; perform for 3–5 seconds then release 5–10 seconds

  • If still refractory, administer succinylcholine: IV dosing for neonate/infant 2\,\text{mg/kg}; for adult/child 1\,\text{mg/kg}; IM dosing neonate/infant 5\,\text{mg/kg}; adult/child 4\,\text{mg/kg}; consider atropine 0.02 mg/kg in children <5 years to prevent bradycardia

RAPID SEQUENCE INTUBATION (RSI)

• RSI aims for rapid unconsciousness & paralysis to minimize aspiration risk.

• Key steps:

  • Preoxygenation: 3–5 minutes

  • Cricoid pressure (Sellick maneuver): apply approx 30\,\text{N} (≈ 3\ \text{kg} or 10 lbs) to occlude the esophagus

  • Induction agent: Propofol (if hemodynamically stable) or Etomidate

  • Rapid-acting paralytic: Succinylcholine or Rocuronium

  • Do not ventilate during apnea; perform apneic ventilation with high-flow O2 if feasible

  • After 30–60 seconds post-paralysis, proceed to intubation

  • Maintain cricoid pressure until the ETT cuff is inflated and a manual breath is delivered

INVASIVE AIRWAYS

• Percutaneous cricothyroidotomy with jet ventilation:

  • Large-bore needle through cricothyroid membrane; connect to a jet ventilator; high O2 pressure (~50\ \text{psi}) due to small lumen; expiration is passive via glottis and upper airway

  • Optional guidewire-assisted dilation to place a cricothyroid airway

• Surgical cricothyroidotomy: emergency procedure with vertical skin incision, small horizontal incision through the cricothyroid membrane; insert airway into trachea.

NASAL INTUBATION CONTRAINDICATIONS

• Avoid nasal intubation if cribriform plate injury, Le Fort II/III fractures, basilar skull fracture, CSF rhinorrhea, raccoon eyes, periorbital edema, coagulopathy (epistaxis risk), prior transsphenoidal hypophysectomy, prior Caldwell-Luc procedure, or nasal fracture.

INTUBATION TECHNIQUES AND VISUALIZATION

• Direct Laryngoscopy (DL): MAC or Miller blades; Macintosh blade lifts the epiglottis indirectly via the vallecula; Miller blade directly lifts the epiglottis.

• BURP maneuver (Backwards, Upwards, Rightward Pressure) improves glottic visualization when needed.

• VIEW GRADING (Cormack & Lehane): describes DL view

  • Grade 1: complete view of glottis

  • Grade 2A/2B: posterior glottic view or corniculate region

  • Grade 3: epiglottis only

  • Grade 4: only soft palate or no glottic structure

INTUBATION ADVANCED TECHNIQUES AND TOOLS

• Eschmann introducer (Gum elastic bougie): advances into trachea in difficult/very anterior glottic view (Class 2b or 3); ETT slides over bougie; rotate counterclockwise to facilitate passage

• Lighted stylet: blind intubation using transcutaneous illumination to identify tracheal location; if in esophagus, illumination is less bright

• Video-assisted laryngoscopy (VAL) equipment: GlideScope includes a camera; 60° anterior bend; reduces cervical motion; can visualize structures beyond the reach of DL; potential issues include fogging and secretions

LARYNGEAL VIEW DURING LARYNGOSCOPY – ND/DI

• Direct vs indirect views: both aim to identify glottic opening, but visualization differs with tool type

AIRWAY DEVICES – LMA, I-GEL, and Fastrach (detailed)

• LMA (Laryngeal Mask Airway): popular SGD; sealed airway device that sits over glottis; allows ventilation without tracheal intubation; not in trachea; cuff pressure management important to avoid nerve injury or pharyngeal necrosis; max cuff pressure ≈ 20\,\text{cm H2O}. If leak occurs: reposition rather than adding air; consider ETT if unsuccessful.

• Fastrach LMA: intubating LMA variant; tube pusher, built-in suction, and bite block; communicates to ETT through the device; provides a conduit for intubation.

• I-GEL: cuffless supraglottic device; used in ENT/bronchoscopy contexts (e.g., EBUS bronchoscopy); recommended ventilation with high O2 flow; for proceduralists with airway manipulation.

• RISKS of SGD overinflation: nerves (lingual, hypoglossal, RLN) injury; pharyngeal necrosis; if leak: reposition rather than increasing air; may require ETT when ventilation is inadequate.

VIDEO-ASSISTED LARYNGOSCOPY (VAL) – ADDITIONAL NOTES

• VAL allows visualization of structures beyond DL; GlideScope: 60-degree bend; advantages for anterior airways and reduced cervical movement; potential complications include pharyngeal injury; larger blade may impede ETT insertion; hand-eye coordination challenges; camera fogging or secretions may obscure view

PRECAUTIONARY AND SAFETY STRATEGIES DURING AIRWAY MANAGEMENT

• Aligning the axes: Sniffing position is optimal for tracheal intubation; achieved by a combination of cervical flexion and atlanto-occipital extension; helps align oral, pharyngeal, and laryngeal axes

• Obese patients: ramping strategy to align sternal level with external auditory canal; elevate head/torso to improve airway access and ventilation

• BURP can improve laryngoscopic view; use when necessary to improve glottic exposure

• In awake/intubation plans, preserve spontaneous ventilation as long as possible in anticipated difficult airways

RSI SUMMARY AND PRACTICAL STEPS

• Preoxygenate for 3–5 minutes; ensure a tight mask seal with good EtCO2 waveform and FiO2 ≥ 0.90.

• Apply cricoid pressure (Sellick) at ~30\,\text{N} (≈ 3\ \text{kg} or 10 lbs).

• Use induction agent (propofol or etomidate) and rapid-acting paralytic (succinylcholine or rocuronium).

• Do not ventilate during apnea; after paralysis, proceed with intubation within 30–60 seconds.

• Maintain cricoid pressure until the ETT cuff is inflated and a breath is delivered to confirm placement.

SUMMARY OF KEY POINTS FOR EXAM PREP

• Know airway segments, landmarks, and their clinical significance (e.g., carina sensitivity, cricoid concept, Mallampati predictions).

• Memorize quantitative values useful in the exam and practice: tracheal length, carina distances, bronchial bifurcation angles, cuff pressures, RSI press sums, preoxygenation times, and spinal/joint mobility ranges.

• Distinguish SLN vs RLN functions and their clinical implications (e.g., RLN injury risk during thoracic/neck surgery, hoarseness patterns).

• Understand when to choose DL vs VAL, when to use LMAs vs endotracheal tubes, and the indications/contradictions for nasal intubation.

• Be familiar with the ASA Difficult Airway Algorithm, including escalation pathways and the role of awake intubation and alternative techniques.

• Recognize signs and managing laryngospasm, including pharmacologic (succinylcholine) and non-pharmacologic maneuvers (Larson’s maneuver, CPAP).

• Prepare for pediatric differences and the dynamic nature of pediatric airway management.

• Practice layout of stepwise airway management in emergencies and the rationale behind preserving spontaneous ventilation until airway security.

KEY QUOTES AND NOMENCLATURE

• Cricoid pressure (Sellick maneuver): 30\ {\text{N}} (≈ 3\ \text{kg} or 10 lbs).

• ETT cuff pressure target: <25\ \text{cm H2O}.

• LMA maximum airway pressure for ventilation: 20\ \text{cm H2O}.

• Normal mouth opening: 4-6\ \text{cm} or 2-3\ \text{fingerbreadths}.

• Thyromental distance: < 6\ \text{cm} indicates potential difficult airway; thyroid notch to hyoid distance ≈ 2\ \text{fingerbreadths}.

• AO joint normal flexion/extension: 90-165^{\circ}.

• Tracheal length: 10-20\ \text{cm}.

• Right bronchus bifurcation distance: 2.5\ \text{cm} from carina; angle 25-30^{\circ}.

• Left bronchus bifurcation distance: 5\ \text{cm} from carina; angle 45^{\circ}.

• FRC denitrogenation can provide up to 8\ \text{minutes} of oxygenation during apnea.

• RSI: avoid ventilation during apnea; consider awake pathways when indicated; re-check with exhaled CO2 after airway placement.

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