190617_Airway Flashcards
Upper Airway
Nasal Passages
Oral Cavity
The Pharynx
Nasal Passages (parts)
Septum
Turbinates
Adenoids
Nasal Passages (function)
Accounts for 2/3 of total upper airway resistance
Humidify
Filter
Warm
Nasal Passages (innervation)
Branches of the trigeminal nerve (CN V)
Oral Cavity (parts)
Teeth Tongue *Predominate cause of airway resistance in oral cavity Hard palate Soft palate
Oral Cavity (innervation)
Trigeminal Nerve (CN V) • Hard and Soft palate • Anterior 2/3 tongue Glossopharyngeal (CN IX) • Posterior 1/3 tongue • Soft palate • Oropharynx
The Pharynx (parts)
Nasopharynx • Border is the soft palate Oropharynx • Border is the epiglottis (supraglottic) • Tonsils, Uvula Hypopharynx/ Laryngopharynx • Subglottic
The Pharynx (innervation)
Glossopharyngeal (CN IX)
Vagus (CN X)
Larynx (cartilage)
9 Cartilages = 3 Paired (6 total) • Arytenoid (2) • Corniculate (2) • Cuneiform (2) 3 Unpaired • Thyroid • Cricoid • Epiglottis
*Located at C4-C6 in the adult
Larynx (function)
Airway protection
Respiration
Phonation
Unpaired Cartilages
Thyroid Cartilage
• Large and most prominent
• Anterior attachment for vocal cords
Epiglottis
• Covers opening to the larynx during swallowing
Cricoid Cartilage
• Only complete cartilaginous, signet-shaped, ring
• Narrowest portion of the pediatric airway
Paired Cartilages
Arytenoid
• Posterior attachment for Vocal Cords
• Falsely identified in an anterior airway
Corniculate
• Posterior portion of the aryepiglottic fold
Cuneiform
• In the aryepiglottic fold, not always present
• Lateral to corniculates
Larynx (other parts)
Vocal Cords
• Appear pearly white
• Formed by the thyroarytenoid ligaments
• Attached anteriorly to the thyroid cartilage and posteriorly to the arytenoid cartilages
Glottic Opening
• Triangular fissure between the cords
• Narrowest portion of the adult airway
Glottic Opening (Intrinsic Laryngeal Muscles)
Lateral Cricoarytenoid • Adducts the vocal cords Arytenoid Muscles • Oblique arytenoids and transverse arytenoids • Adduct the vocal cords Posterior Cricoarytenoid • The only vocal cord abductors
Vocal Cord Length (Intrinsic Laryngeal Muscles)
Cricothyroid • Tenses/Elongates vocal cords Thyroarytenoid • Relaxes/shortens vocal cords Vocalis • Relaxes/shortens vocal cords
Intrinsic Laryngeal Muscles
Control the movements of the laryngeal cartilages
• Control the length and tension of the vocal cords and the size of the glottic opening
Cricothyroid muscle
*innervated by the external branch of the superior laryngeal nerve (a branch of the Vagus nerve (CN X))
All others innervated by the recurrent laryngeal nerve (a branch of the Vagus nerve (CN X))
Extrinsic Laryngeal Muscles
Move larynx as a whole
Suprahyoid Group
• Stylohyoid, mylohyoid, geniohyoid, digastric
• Raises larynx cephalad
Infrahyoid Group
• Sternothyroid, sternohyoid, thyrohyoid, omohyoid
• Moves larynx caudad
***innervated by what nerve?
Lower Airway
- Trachea
- Carina
- Bronchi
- Bronchioles
- Terminal bronchioles
- Respiratory bronchioles
- Alveoli
Trachea
• Fibromuscular tube
• 10-20 cm length & 22 mm diameter (Adult)
• 16-20 U shaped cartilages
• Posterior side lacks cartilage
• Bifurcates lower border T4- carina
• Carina
- Trachea divides into Right & Left mainstem bronchi
- Right bronchi is 2.5 cm long with angle of 25 deg
- Left bronchi is 5 cm with an angle of 45 deg
Airway assessment (critical)
Critical:
•“No single test has been devised to predict a difficult airway accurately 100% of the time”
•Previous difficult intubation should always raise suspicion
•Review prior anesthetic records when possible for guidance on prior AW management
an unpredicted difficult airway is worst case
Airway Assessment (theory)
- Thorough and systematic airway assessment and physical exam should be performed in the preoperative period.
- Followed by a patient specific plan for anesthesia.
- Goal is to identify potential airway problems and identify a difficult airway
Note: It is not one factor but a combination of factors that create the difficult airway
Airway Assessment (basic questions to consider)
▪Radiation or burn to head/neck? ▪C-spine pain of LROM? ▪TMJ pain? ▪Rheumatoid arthritis? ▪Ankylosing spondylitis? ▪Abscess or tumor? ▪Prior intubation or tracheotomy? ▪Snoring or sleep apnea? ▪Dysphagia or stridor?
Airway Assessment
• General appearance -Head, neck size and fullness • Range of motion • Dentition • Mouth -Tongue, lips, tissues, gums • Mouth opening - 30-40 mm or 2-3 fingers • Body habitus • Mallampati classification* • Thyromental distance* • Mandibular Protrusion Test* • History of previous difficult airway • Diagnosis • Planned surgery
Mallampati classification*
direct laryngoscopy ~ PUSH! Pillars (I) Uvula (II) Soft Palate (III) Hard Palate (IV)
Cormack and Lehane Score
laryngoscopic view of the glottis
•Grade I: most of the glottis visible
•Grade II: Only the posterior portion of glottis visible •Grade III: Only epiglottis visible
•Grade IV: No airway structures visualized
Thyromental distance*
▪Distance from lower border of mandible to thyroid notch with neck fully extended
▪Normal 6-6.5 cm or 4 Fingerbreadths
▪Difficult intubation < 3 fingers, receding mandible; “anterior airway” ~min space to move tongue forward
Mandibular Protrusion Test*
Class A: Lower incisors can be brought forward past the upper insicors (bite upper lip)
Class B: Lower incisors can be brought forward to upper incisors
Class C: Lower incisors can NOT be brought forward to upper incisors
Preparing for Induction
- Monitors on and settings appropriate
- Suction on and at head of bed
- Machine checked, means of positive pressure ventilation
- Airway
- IV
- Drugs (emergency and case/pt specific)
- Special equipment
Pre-oxygenation
Goal = Increase O2 concentration in functional residual capacity (FRC) by “washing out” nitrogen (79% in RA) in the FRC with oxygen
(FRC= volume of air left in the lung at end of passive expiration)
•3-5 minutes of “tight” mask fit during normal tidal breathing with100% FiO2 at> 6L/min flow = 10 minutes of safe apnea time
•4 vital capacity breaths within 30 seconds with 100% FiO2 at >6L/min= 5 minutes of safe apnea time (8 breaths over 60 seconds will > effectiveness over 4br/ 30sec)
•An end-tidal concentration of oxygen greater than 90% is considered to maximize apnea time.
Aspiration
- Loss of AW reflexes has major risk of aspiration
- Premise of NPO guidelines
- High risk: full stomach, symptomatic gastroesophageal reflux disease (GERD), hiatal hernia, presence of a nasogastric tube, morbid obesity, diabetic gastroparesis, or pregnancy
- Aspiration prophylaxis: decrease gastric volume and to increase gastric fluid pH (nonparticulate antacids (e.g., Bicitra), promotility drugs (e.g., metoclopramide), and H2-receptor antagonists. These drugs may be used alone or in combination)
Airway Set up
- Appropriate sized face mask*
- Means of Positive Pressure Ventilation (PPV)-> ambu-bag, machine circuit; O2 source
- Suction on and easily accessible
- Tongue depressor
- Appropriate sized oral and nasal airways*
- Laryngoscope handle*
- 2 different blades*
- Endotracheal Tube (ETT)- 2 sizes*
- Stylet
- Syringe
- Appropriate sized Laryngeal Mask Airway (LMA) (difficult airway)*
- Tape
Difficult mask ventilation ~ predictors
OSA / snoring > 55 y/o Male BMI >/= 30 kg/m^2 Mallampati classification III or IV Beard Edentulousness (missing teeth or dentures)
Mask Ventilation
•Effectiveness assessed by: chest rise, exhaled tidal volumes, pulse oximetry, and capnography
•Adequate tidal volumes should be achieved with peak inspiratory pressures less than 20 cm H2O
•higher pressures should be avoided to prevent gastric insufflation
?•NOT ADEQUATE @ <20 cm H2O?
•airway patency and pulmonary compliance should be assessed
Potential Hazards to Advanced Airway Management
❑ Dental damage ❑ Soft tissue/mechanical injury ❑ Laryngospasm ❑ Bronchospasm ❑ Vomiting/Aspiration ❑ Hypoxemia/Hypercarbia ❑ SNS stimulation ❑ Esophageal/Endobronchial intubation
Difficult mask ventilation ~ predictors
- long upper incisors
- prominent overbite
- inability to protrude mandible
- small mouth opening
- Mallampati classification III or IV
- high / arched palate
- short thyromental distance
- shorth / thick neck (>17in)
- limited cervical mobility
Endotracheal Tube indications
Gold standard for AW management
Absolute indications:
• full stomach
• high risk for aspiration of gastric secretions or blood
• critically ill
• significant lung abnormalities (e.g., low lung compliance, high airway resistance, impaired oxygenation)
• surgery requiring lung isolation
• otorhinolaryngologic surgery where an SGA would interfere with surgical access (AW management discussed w/ surgeon)
• anticipated need for postoperative ventilatory support
• failed SGA placement
Others
• surgical requirement for NMBDs
• positioning that does not allow quick access to the AW (e.g., prone, etc)
• predicted difficult airway
• prolonged procedures
Endotracheal Tube (features)
A variety of types based on pt needs and surgical requirements
Common features:
• Standard 15-mm adapter
• high-volume, low-pressure cuff
- Purpose: create a seal to protect against gastric aspiration
- Ensures tidal volume delivered reached the lungs
• beveled tip: facilitates passage through the vocal cords
• “Murphy eye” additional distal opening in the side wall - Back-up portal for ventilation should the distal end of the lumen become obstructed by either soft tissue or secretions
• Pilot balloon with one-way valve
- Cuff inflation & assessment of cuff pressure
- Minimal inflation volume to attain air leak ~20- 25cm H2O
Endotracheal Tube (placement)
ETT size based on internal diameter (ID)
Adult ETT want 2 sizes available •
- Female: 6.5-7.0 mm id
- Male: 7.5-8.0 mm id
Ideal position: distal end in mid-trachea
- 4 cm above the carina and 2 cm below the vocal cords *Males approximately 23 cm
*Females approximately 21 cm
*IDx3= approximate depth
Nasal vs. Oral
Securement to maxilla (fixed)
***ALWAYS listen for bilateral breath sounds, look for bilateral chest rise and presence of endtidal CO2!
ETT Options
Cuffed Un-cuffed Oral RAE NASAL RAE Reinforced tubes Double lumen ETT
Stylet
- shaping the ETT with a malleable stylet into a hockey stick shape
- 60-degree angle formed 4 to 5 cm from the distal end
- removed when the tip of the ETT is right at the level of the vocal cords
- limits trauma to the tracheal mucosa
Laryngeal Mask Airway (LMA)
A supraglottic airway device •“perilaryngeal sealer” Multipurpose: • primary airway management device • a rescue airway device • conduit for endotracheal intubation. Appropriate Size is based on patient weight • Adult sizes • 30-50 Kg→ LMA 3 • 50-70 Kg→ LMA 4 • 70-100 Kg→ LMA 5 • >100 Kg→ LMA 6
Classic vs. Supreme LMA
***MUST HAVE BITE BLOCK!!!
LMA Insertion
Equipment
• 20 or 50 cc syringe,
• lubricant, suction, stethoscope, tape, soft bite block Adequate depth of anesthesia is critical for successful insertion
Deflate cuff (+/-), lubricate posterior aspect
After insertion, inflate with minimum effective volume of air
• target cuff pressure of 40 to 60 cm H2O
Confirmation: gentle PPV, capnography, and auscultation • leak audible at inspiratory pressure ~18 to 20 cm H2O
Advantages of LMA over ETT
- increased speed and ease of placement by inexperienced personnel
- improved hemodynamic stability at induction and during emergence
- reduced anesthetic requirements for airway tolerance •lower frequency of coughing during emergence
- lower incidence of sore throats in adults (10% vs 30%)
- avoids “foreign body” in the trachea
Disadvantages of LMA over ETT
- NOT a definitive AW
- lower seal pressure (inability to use mechanical ventilation* (at higher peak pressures))
- higher frequency of gastric insufflation
- does not maximally protect against aspiration
- no protection against laryngospasm
