Anesthesia: Difficult Airway Management Predictors
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Questions and Answers

What is a difficult airway management scenario characterized by?

  • Easy facemask ventilation, but difficulty with laryngoscopy
  • Successful SGA ventilation, but difficulty with extubation
  • Successful facemask ventilation, laryngoscopy, and intubation
  • Difficulty with facemask ventilation, laryngoscopy, intubation, or all of these (correct)

    • What is a characteristic of difficult facemask ventilation?

  • Inadequate mask seal with excess gas leak (correct)
  • Successful SGA placement on the first attempt
  • Visualization of the entire vocal cord during laryngoscopy
  • Easy mask seal with minimal gas leak

    • What is a predictor of difficult laryngoscopy?

  • Ability to visualize the entire vocal cord on the first attempt
  • Successful facemask ventilation with minimal gas leak
  • Easy SGA placement on the first attempt
  • Inability to visualize any portion of the vocal cords after multiple attempts (correct)

    • Which of the following is an aspiration risk factor?

    <p>All of the above</p> Signup and view all the answers

    What is a desaturation risk factor?

    <p>All of the above</p> Signup and view all the answers

    What is the acronym for difficult FONA airway?

    <p>SHORT</p> Signup and view all the answers

    What is the primary reason for desaturation in pediatric and septic patients?

    <p>Lower FRC and increased oxygen consumption</p> Signup and view all the answers

    What is the definition of Cannot Intubate/Cannot Oxygenate (CICO) scenario?

    <p>Failure to maintain adequate alveolar oxygenation by face mask, SGA, or ETT despite optimal attempts</p> Signup and view all the answers

    What is the purpose of apneic oxygenation?

    <p>To provide oxygenation during short-term apneic episodes, such as induction and emergence</p> Signup and view all the answers

    What is the typical flow rate and device used for apneic oxygenation?

    <p>15 LPM via NC</p> Signup and view all the answers

    What is the maximum flow rate that can be delivered via nasal cannula for an extended period?

    <p>Cannot deliver &gt;6 LPM for extended periods</p> Signup and view all the answers

    What is the typical FiO2 delivered by a simple mask at 5-6 LPM?

    <p>30-45%</p> Signup and view all the answers

    What is the primary function of bronchial arteries?

    <p>To provide perfusion to the lungs, similar to the coronary arteries in the heart</p> Signup and view all the answers

    What is the normal ventilation-to-perfusion ratio (V/Q) in the lungs?

    <p>4:5</p> Signup and view all the answers

    What happens to blood flow in hypoxic or atelectic alveoli due to hypoxic pulmonary vasoconstriction?

    <p>It is redistributed to areas of better ventilation</p> Signup and view all the answers

    What is the main characteristic of restrictive lung disease in terms of ventilator settings?

    <p>Higher PIP and higher Pplat</p> Signup and view all the answers

    What is the effect of hypoxic pulmonary vasoconstriction on pulmonary vessels?

    <p>Hypercarbia and acidosis cause vasoconstriction to divert blood flow to better ventilated alveoli</p> Signup and view all the answers

    What is the effect of high O2 tension and hypocapnea unique to pulmonary vessels?

    <p>Vasodilation to help vessels pick up more oxygen</p> Signup and view all the answers

    What is the main characteristic of obstructive lung disease in terms of ventilator settings?

    <p>Higher PIP and normal/elevated Pplat</p> Signup and view all the answers

    What is the correlation between Pplat and lung compliance?

    <p>Higher Pplat indicates lower compliance</p> Signup and view all the answers

    What is required for preoxygenation?

    <p>A tight seal against the face and 100% FiO2 at a high flow (10-12 LPM) for 3-5 mins</p> Signup and view all the answers

    What factors does oxygen delivery via nasal cannula (NC) depend on?

    <p>All of the above</p> Signup and view all the answers

    What is the increase in FiO2 for every liter of oxygen supplied over 1LPM, according to the conventional prediction model?

    <p>4%</p> Signup and view all the answers

    What is the FIO2 for a patient on 5 LPM nasal cannula (NC)?

    <p>0.40</p> Signup and view all the answers

    Why would a patient receiving apneic ventilation have an elevated ETCO2 and respiratory acidosis?

    <p>Apneic ventilation helps maintain PaO2, but does not prevent hypercarbia and acidosis</p> Signup and view all the answers

    What is the principle behind apneic ventilation?

    <p>Even without lung expansion/ diaphragmatic movement, alveoli will continue to receive oxygen if a higher gradient exists</p> Signup and view all the answers

    Apneic oxygenation does not require a patent airway

    <p>False</p> Signup and view all the answers

    Which of the following devices cannot be used for preoxygenation due to their inability to create a seal?

    <p>All of the above</p> Signup and view all the answers

    What is the primary advantage of high flow nasal cannula over a simple mask?

    <p>Increased FiO2 delivery</p> Signup and view all the answers

    What is the mechanism by which high flow nasal cannula allows for a higher FiO2 delivery?

    <p>By utilizing the nasopharynx as an oxygen reservoir</p> Signup and view all the answers

    What is the maximum flow rate that can be delivered via high flow nasal cannula?

    <p>60 LPM</p> Signup and view all the answers

    Why is high flow nasal cannula better tolerated by patients compared to face mask and noninvasive PPV?

    <p>Because it is more comfortable</p> Signup and view all the answers

    Where should the top of an adult face mask sit?

    <p>On the bridge of the nose</p> Signup and view all the answers

    What is the reference point for aligning the upper border of an adult face mask?

    <p>The pupils</p> Signup and view all the answers

    Where should the bottom of an adult face mask sit?

    <p>Between the lower lip and chin</p> Signup and view all the answers

    What is the primary function of the middle and ring fingers in proper mask positioning (E)?

    <p>To compress the mask to the face while lifting the chin</p> Signup and view all the answers

    Which finger is used to provide an anterior jaw thrust in proper mask positioning (E)?

    <p>5th finger</p> Signup and view all the answers

    What is the shape formed by the left thumb and index finger in proper mask positioning?

    <p>The shape of the letter C</p> Signup and view all the answers

    What is the importance of avoiding squeezing too hard/fast during bag mask ventilation?

    <p>To prevent gastric distention</p> Signup and view all the answers

    What is the optimal pressure you want to generate during bag mask ventilation?

    <p>less than 20-25 cm H2O</p> Signup and view all the answers

    You are ventilating a patient and the ventilation is inadequate. What should you immediately do?

    <p>Reposition airway and ventilate</p> Signup and view all the answers

    After repositioning the airway, ventilation is inadequate. What should you do next?

    <p>Insert an airway adjunct</p> Signup and view all the answers

    After insertion of an airway adjunct, ventilation is inadequate. What should you do next?

    <p>Use a 2-handed mask technique</p> Signup and view all the answers

    While using the 2-handed technique to BVM, ventilation is inadequate. What should you do next?

    <p>Proceed to intubation, SGA, or reverse sedation</p> Signup and view all the answers

    Signs of inadequate ventilation are the opposite of confirmation of intubation

    <p>True</p> Signup and view all the answers

    Decreased SPO2 is a late sign of inadequate ventilation

    <p>True</p> Signup and view all the answers

    What is the most common cause of airway obstruction in anesthesia?

    <p>Tongue</p> Signup and view all the answers

    Which of the following is a characteristic of the chin lift maneuver compared to the jaw thrust?

    <p>Increases movement at C1/C2 more than the jaw thrust</p> Signup and view all the answers

    What is the purpose of performing Larson's maneuver during airway management?

    <p>To exaggerate the jaw thrust and open the airway further</p> Signup and view all the answers

    What is the main difference between the jaw thrust and chin lift maneuvers?

    <p>The jaw thrust lifts the mandible, while the chin lift lifts the hyoid bone/rotates the neck</p> Signup and view all the answers

    What is the primary benefit of using a nasal airway over an oral airway?

    <p>It can be used in awake patients</p> Signup and view all the answers

    What is a contraindication for using a nasal airway? (select 2)

    <p>Basilar skull fracture</p> Signup and view all the answers

    What is the correct way to insert a nasal airway?

    <p>With the bevel facing the nasal septum</p> Signup and view all the answers

    What is the purpose of using a tongue blade to assist in placing an oral airway?

    <p>To push the tongue out of the way</p> Signup and view all the answers

    What is the primary function of an OPA (Oropharyngeal Airway) in difficult airway management?

    <p>To provide a channel for air passage by pulling the tongue and epiglottis away from the posterior pharyngeal wall</p> Signup and view all the answers

    Which of the following statements is true about OPA (oral pharyngeal airway) and NPA (nasopharyngeal airway)?

    <p>They do not enter the larynx.</p> Signup and view all the answers

    Which type of OPA is this?

    <p>Guedel</p> Signup and view all the answers

    What type of OPA is this?

    <p>Williams</p> Signup and view all the answers

    What are the indications for using upraglottic airway devices (SGA)?

    <p>Rescue ventilation for difficult mask ventilation and failed intubation</p> Signup and view all the answers

    What are two concerns when using supraglottic airway devices?

    <p>Concern of aspiration because airway is not protected</p> Signup and view all the answers

    What is the purpose of the Murphy eye in an endotracheal tube?

    <p>To decrease the risk of occlusion</p> Signup and view all the answers

    What is the goal pressure for positive pressure ventilation (PPV) in adults?

    <p>&lt;20-25 cmH2O</p> Signup and view all the answers

    Ett Cuffs should be inflated to what pressure?

    <p>Minimum occlusive pressure</p> Signup and view all the answers

    Why is it important to assess the cuff for expansion during a long case with nitrous oxide?

    <p>Because cuffs are permeable to oxygen and nitrous oxide</p> Signup and view all the answers

    Which of the following is a disadvantage of using high pressure/low volume cuffs in airway management?

    <p>Greater risk of ischemic damage</p> Signup and view all the answers

    What is a common complication associated with the use of low pressure/high volume cuffs?

    <p>All of the above</p> Signup and view all the answers

    What acronym is used to predict difficult SGA placement?

    <p>RODS</p> Signup and view all the answers

    What is the optimal ETT depth for adults?

    <p>22-23 cm or 1-2 cm past the glottic opening</p> Signup and view all the answers

    What are the approximate ETT sizes that should be used in adult females and males?

    <p>7-7.5 mm for females, 7.5-9.0 mm for males</p> Signup and view all the answers

    What is the formula for pediatric ETT sizes (cuffed and uncuffed)?

    <p>Age/4 + 3.5 cuffed</p> Signup and view all the answers

    What is the recommended depth for a pediatric endotracheal tube (ETT)?

    <p>3x ETT size</p> Signup and view all the answers

    What is the main difference between MAC and Miller blades in terms of lifting the epiglottis?

    <p>MAC blades indirectly lift the epiglottis, whereas Miller blades directly lift it.</p> Signup and view all the answers

    What is part of the mandatory setup?

    <p>ASS (Ambu, suction, stethoscope)</p> Signup and view all the answers

    What is the sniffing position ?

    <p>Neck flexion and atlanto-occipital extension</p> Signup and view all the answers

    What is the preferred method of preoxygenation?

    <p>Tidal volume method</p> Signup and view all the answers

    What is the Tidal Volume method used for pre-oxygenation?

    <p>100% FiO2 at 10-12 L/min for 3 minutes</p> Signup and view all the answers

    What is the time to oxyhemoglobin desaturation below 80% in a healthy, nonobese adult compared to children or obese adults?

    <p>9 minutes in healthy adults, 3 minutes or less in children or obese adults</p> Signup and view all the answers

    What are the alternate preoxygenation methods?

    <p>Both 4 Vital Capacity breaths over 30 seconds and 8 Vital Capacity breaths over 60 seconds</p> Signup and view all the answers

    What is the purpose of the Sellick maneuver and a negative consequence?

    <p>To prevent regurgitation by applying pressure to the cricoid cartilage</p> Signup and view all the answers

    What is the primary purpose of the burp maneuver and why is it performed in airway management?

    <p>To displace the larynx Back, Up, Right and using Pressure over the thyroid cartilage to improve visualization of the glottis</p> Signup and view all the answers

    Low pressure/ high volume cuffs are used more frequently in anesthesia

    <p>True</p> Signup and view all the answers

    Study Notes

    Difficult Airway Management Predictors

    • Difficult airway: a clinical situation where a trained anesthetist experiences difficulty with facemask ventilation, laryngoscopy, intubation, or all of these.
    • Difficult facemask ventilation: unable to provide due to inadequate mask seal, excess gas leak (BOOTS).
    • Difficult laryngoscopy: unable to visualize any portion of the vocal cords after multiple attempts (LEMON).
    • Difficult SGA ventilation: unable to provide adequate ventilation due to difficult SGA placement, SGA requiring multiple attempts, excessive resistance (RODS).
    • Difficult extubation.
    • Difficult FONA airway - SHORT acronym.
    • Preoperative airway assessment: additionally consider aspiration risk and desaturation risks.

    Aspiration Risk

    • Active GERD symptoms, acute trauma, GI problems, patients on a lot of narcotics, pregnancy 12+ weeks and even up to 10 weeks postpartum, GLP1 receptor antagonists.
    • Neuromuscular disease or any other disease that causes gastroparesis (diabetes).
    • Oral contrast.

    Desaturation Risks

    • Pediatrics, obese, COPD, OSA, anyone that hypoventilates or has decreased FRC, pulmonary dysfunction.
    • Kids and septic patients desat faster due to lower FRC and increased O2 consumption.

    Inadequate Ventilation

    • Gas leak out of mask and increasing use of oxygen flush valve, need for airway adjunct, need for 2-handed BVM technique, poor chest rise, absent/inadequate ETCO2, gastric air entry/dilation, decreasing O2 sat, cyanosis, hemodynamic changes associated with hypoxemia, hypercarbia.

    Cannot Intubate/Cannot Oxygenate (CICO)

    • Failure to maintain adequate alveolar oxygenation by face mask, SGA, or ETT despite optimal attempts.
    • Repeat attempts without changing technique are not likely to work.
    • Multiple attempts increase risk of trauma.
    • Multiple attempts decrease effectiveness of other attempts and other techniques.

    Basic Airway Management

    • Oxygen delivery, oral and nasal airways, mask ventilation, confirming ventilation.
    • Preoxygenation requires a tight seal against face - 100% FiO2 at a high flow (10-12 LPM) for 3-5 mins.

    Nasal Cannula

    • Oxygen delivery depends on oxygen flow, nasopharyngeal volume, patient's TV, and inspiratory time.
    • Inspired oxygen increases roughly 2% per liter with quiet breathing.
    • 5LPM delivers 40% FiO2.
    • Cannot deliver >6 LPM for extended periods.

    Apneic Oxygenation

    • Used for short-term apneic episodes (e.g. induction, emergence).
    • Requires a patent airway.
    • Even without lung expansion/diaphragmatic movement, alveoli will continue to receive oxygen if a higher gradient exists.
    • Helps maintain PaO2 but does NOT prevent hypercarbia and acidosis.
    • Provide apneic oxygenation via NC at 15 LPM.

    Simple Mask

    • Not as well tolerated as a NC.
    • Do not completely seal against the face - not used for preoxygenation.
    • 5-6 LPM = FiO2 30-45%.
    • 7-8 LPM = FiO2 40-60%.
    • Minimum flow of 5 LPM must be maintained to limit breathing.

    Partial Rebreathing and NRB

    • Contains one-way valves over exhalation ports and between reservoir bag and mask.
    • Masks with gas reservoirs do not seal against the face - NOT for preoxygenation.
    • Partial rebreather = % of patient's exhaled TV refills the bag.
    • NRB 7-15 LPM = 40-100% FiO2.

    High Flow Nasal Cannula

    • Can utilize flow rates up to 60 LPM.
    • Generates FiO2 near 100%.
    • Allows nasopharynx to act as O2 reservoir.
    • Better tolerated than face mask and noninvasive PPV.

    Adult Face Masks

    • Goal is an airtight seal.
    • BVM technique - EC technique.
    • Put mask on from eyes to chin to prevent mask from getting into pt's eyes.
    • Normally use size 5 for adults.

    Ventilation Basics

    • Use right hand to squeeze bag.
    • APL = adjustable pressure limiter valve.
    • Avoid squeezing too hard/fast to prevent gastric distention.
    • Pressure you want to generate 25 degrees bend in tube, high flows, corrugated tubing, ETT tube (smaller tubes are more turbulent).

    Pulmonary Blood Flow

    • Pulmonary vessels are much shorter than systemic vessels and therefore have decreased resistance - Poiseuille's law.
    • Bronchial arteries:
      • Like coronary arteries in heart.
      • Feed the lungs.
      • 2% of CO.
      • Do not participate in gas exchange.
    • Pulmonary arteries:
      • Transport - bring unoxygenated blood to the lungs to receive oxygenation.
      • Low pressure system (PVR is low) and is very sensitive to small changes.
      • Changes in circulation are locally mediated by changes in O2 and CO2.

    V/Q Basics

    • Normal Ventilation/Perfusion is 4L/5L.
    • Things that cause dead space (i.e. block perfusion) = PE, cardiogenic shock.
    • Things that cause shunt (i.e. block ventilation) = shunt, pneumonia, atelectasis, airway obstruction.

    Dead Space

    • Ventilated but not perfused.
    • Volume of conducting airways = anatomic dead space = 2mL/kg.
    • Alveolar dead space + anatomic dead space = physiologic dead space.
    • Bohr equation describes the amount of physiologic dead space in a person's lungs by comparing the amount of CO2 in arterial blood to that in exhaled gas.
    • Non-perfused areas equilibrate with inspired air.
    • High V/Q - high O2 and low CO2.

    Shunt

    • Perfused but not ventilated.
    • Perfused areas equilibrate with arterial CO2 (mixed venous).
    • Low V/Q - low O2 and high CO2.

    Hypoxic Pulmonary Vasoconstriction

    • Hypoxic pulmonary vasoconstriction (HPV) = diversion of blood flow from hypoxic or atelectic alveoli to an area of better ventilation or diffusion.
    • Increase blood flow to lungs to improve gas exchange.
    • High O2 tension and hypocapnia vasodilate pulmonary vessels so they can pick up more O2.
    • Hypercarbia and acidosis cause vasoconstriction - increase PVR.

    All Ventilator Modes

    • Pplat is a reflection of the pressure inside the alveoli at the end of inspiration where there is no airflow and directly correlates with lung compliance.
    • Higher Pplat indicates lower compliance.

    Restrictive Lung Disease

    • Reduced compliance limits expansion of lungs, increased resistance in lung tissue.
    • PIP and Pplat elevated.
    • Require higher PIP and higher PEEP due to reduced lung compliance and risk of atelectasis.

    Obstructive Lung Disease

    • Increased compliance due to air trapping, loss of elasticity due to overexpansion of lungs, increased airway resistance.
    • PIP elevated, Pplat normal or elevated depending on degree of air trapping.
    • Require higher PIP to overcome airway resistance with potentially normal or elevated Pplat depending on degree of hyperinflation with lower PEEP.

    Pplat

    • Plateau pressure = pressure that remains in alveoli during plateau phase with no air flow.
    • Measure of static lung compliance.
    • Target.

    High Flow Nasal Cannula

    • Can utilize flow rates up to 60 LPM
    • Generates FiO2 near 100%
    • Allows nasopharynx to act as O2 reservoir
    • Better tolerated than face mask and noninvasive PPV

    Difficult Airway Management Predictors

    • Difficult airway: clinical situation in which a trained anesthetist experiences difficulty with facemask ventilation, laryngoscopy, intubation, or all of these
    • Difficult facemask ventilation: not able to provide due to inadequate mask seal, excess gas leak (BOOTS)
    • Difficult laryngoscopy: not able to visualize any portion of the vocal cords after multiple attempts (LEMON)
    • Difficult SGA ventilation: not able to provide adequate ventilation due to difficult SGA placement, SGA requiring multiple attempts, excessive resistance (RODS)
    • Difficult extubation
    • Difficult FONA airway – SHORT acronym
    • Preoperative airway assessment: additionally consider aspiration risk and desaturation risks
    • Aspiration risk: active GERD symptoms, acute trauma, GI problems, pt’s on a lot of narcotics, pregnancy 12+ weeks and even up to 10 weeks postpartum, GLP1 receptor antagonists
    • Desaturation risks: pediatrics, obese, COPD, OSA, anyone that hypoventilates or has decreased FRC, pulmonary dysfunction

    Inadequate Ventilation

    • Inadequate ventilation: gas leak out of mask and increasing use of oxygen flush valve, need for airway adjunct, need for 2-handed BVM technique, poor chest rise, absent/inadequate ETCO2, gastric air entry/dilation, decreasing O2 sat, cyanosis, hemodynamic changes associated with hypoxemia, hypercarbia

    Cannot Intubate/Cannot Oxygenate (CICO)

    • Failure to maintain adequate alveolar oxygenation by face mask, SGA, or ETT despite optimal attempts
    • Repeat attempts without changing technique are not likely to work
    • Multiple attempts increase risk of trauma
    • Multiple attempts decrease effectiveness of other attempts and other techniques

    Basic Airway Management

    • Oxygen delivery: oxygen delivery depends on oxygen flow, nasopharyngeal volume, patient’s TV, and inspiratory time
    • Inspired oxygen increases roughly 2% per liter with quiet breathing
    • 5LPM delivers 40% FiO2
    • Cannot deliver >6 LPM for extended periods
    • Preoxygenation: requires a tight seal against face – 100% FiO2 at a high flow (10-12 LPM) for 3-5 mins
    • Nasal cannula: allows nasopharynx to act as O2 reservoir
    • Apneic oxygenation: used for short-term apneic episodes, e.g., induction, emergence; requires a patent airway
    • Simple mask: not as well tolerated as a NC; do not completely seal against the face – not used for preoxygenation
    • Partial rebreathing and NRB: contains one-way valves over exhalation ports and between reservoir bag and mask; masks with gas reservoirs do not seal against the face – NOT for preoxygenation

    Adult Face Masks

    • Goal is an airtight seal
    • BVM technique: EC technique
    • Put mask on from eyes to chin to prevent mask from getting into pt’s eyes
    • Normally use size 5 for adults

    Ventilation Basics

    • Use right hand to squeeze bag
    • APL: adjustable pressure limiter valve
    • Avoid squeezing too hard/fast to prevent gastric distention
    • Pressure you want to generate 25 degrees bend in tube, high flows, corrugated tubing, ETT tube (smaller tubes are more turbulent)

    Pulmonary Blood Flow

    • Pulmonary vessels are much shorter than systemic vessels and therefore have decreased resistance – Poiseuille’s law
    • Bronchial arteries: like coronary arteries in heart; feed the lungs; 2% of CO; do not participate in gas exchange
    • Pulmonary arteries: transport – bring unoxygenated blood to the lungs to receive oxygenation; low pressure system (PVR is low) and is very sensitive to small changes
    • Changes in circulation are locally mediated by changes in O2 and CO2

    V/Q Basics

    • Normal Ventilation/Perfusion is 4L/5L
    • Things that cause dead space (i.e., block perfusion) = PE, cardiogenic shock
    • Things that cause shunt (i.e., block ventilation) = shunt, pneumonia, atelectasis, airway obstruction
    • Dead Space: ventilated but not perfused
    • V/Q: normal Ventilation/Perfusion is 4L/5L
    • Bohr equation: describes the amount of physiologic dead space in a person’s lungs by comparing the amount of CO2 in arterial blood to that in exhaled gas

    Shunt

    • Perfused but not ventilated
    • Perfused areas equilibrate with arterial CO2 (mixed venous)
    • Low V/Q – low O2 and high CO2

    Hypoxic Pulmonary Vasoconstriction

    • Diversion of blood flow from hypoxic or atelectic alveoli to an area of better ventilation or diffusion
    • Increase blood flow to lungs to improve gas exchange
    • High O2 tension and hypocapnia vasodilate pulmonary vessels so they can pick up more O2
    • Hypercarbia and acidosis cause vasoconstriction → increase PVR

    High Flow Nasal Cannula

    • Can utilize flow rates up to 60 LPM
    • Generates FiO2 near 100%
    • Allows nasopharynx to act as O2 reservoir
    • Better tolerated than face mask and noninvasive PPV adult face mask
    • Proper mask placement: top should sit on the bridge of the nose, upper border aligned with the pupils, and bottom should sit between the lower lip and chin

    Predictors of Difficult Airway Management

    • Difficult airway: clinical situation in which a trained anesthetist experiences difficulty with facemask ventilation, laryngoscopy, intubation, or all of these
    • Difficult facemask ventilation: not able to provide due to inadequate mask seal, excess gas leak
    • Difficult laryngoscopy: not able to visualize any portion of the vocal cords after multiple attempts
    • Difficult SGA ventilation: not able to provide adequate ventilation due to difficult SGA placement, SGA requiring multiple attempts, excessive resistance
    • Difficult extubation and FONA airway management

    Preoperative Airway Assessment

    • Consider aspiration risk and desaturation risks
    • Aspiration risk factors: • Active GERD symptoms, acute trauma, GI problems, patients on narcotics, pregnancy > 12 weeks and up to 10 weeks postpartum, GLP1 receptor antagonists • Neuromuscular disease or any other disease that causes gastroparesis (diabetes) • Oral contrast
    • Desaturation risk factors: • Pediatrics, obese, COPD, OSA, anyone that hypoventilates or has decreased FRC, pulmonary dysfunction • Kids and septic patients desaturate faster due to lower FRC and increased O2 consumption

    Inadequate Ventilation and CICO

    • Inadequate ventilation: gas leak out of mask and increasing use of oxygen flush valve, need for airway adjunct, need for 2-handed BVM technique, poor chest rise, absent/inadequate ETCO2, gastric air entry/dilation, decreasing O2 sat, cyanosis, hemodynamic changes associated with hypoxemia, hypercarbia
    • CICO (Cannot Intubate/Cannot Oxygenate): Failure to maintain adequate alveolar oxygenation by face mask, SGA, or ETT despite optimal attempts

    Basic Airway Management

    • Oxygen delivery, oral and nasal airways, mask ventilation, confirming ventilation
    • Preoxygenation requires a tight seal against the face – 100% FiO2 at a high flow (10-12 LPM) for 3-5 minutes

    Nasal Cannula and Apneic Oxygenation

    • Nasal cannula: oxygen delivery depends on oxygen flow, nasopharyngeal volume, patient’s TV, and inspiratory time
    • Inspired oxygen increases roughly 2% per liter with quiet breathing
    • 5LPM delivers 40% FiO2, cannot deliver >6 LPM for extended periods
    • Apneic oxygenation: • Used for short-term apneic episodes (e.g. induction, emergence) • Requires a patent airway • Even without lung expansion/diaphragmatic movement, alveoli will continue to receive oxygen if a higher gradient exists • Helps maintain PaO2 but does NOT prevent hypercarbia and acidosis • Provide apneic oxygenation via NC at 15 LPM

    Simple Mask and Partial Rebreathing

    • Simple mask: not as well tolerated as a NC, does not completely seal against the face – not used for preoxygenation
    • 5-6 LPM = FiO2 30-45%, 7-8 LPM = FiO2 40-60%
    • Minimum flow of 5 LPM must be maintained to limit breathing
    • Partial rebreathing and NRB: contains one-way valves over exhalation ports and between reservoir bag and mask
    • Masks with gas reservoirs do not seal against the face – NOT for preoxygenation
    • Partial rebreather = % of patient’s exhaled TV refills the bag
    • NRB 7-15 LPM = 40-100% FiO2

    Pulmonary Blood Flow and V/Q Basics

    • Pulmonary vessels are much shorter than systemic vessels and therefore have decreased resistance – Poiseuille’s law
    • Bronchial arteries: • Like coronary arteries in heart • Feed the lungs • 2% of CO • Do not participate in gas exchange
    • Pulmonary arteries: • Transport – bring unoxygenated blood to the lungs to receive oxygenation • Low pressure system (PVR is low) and is very sensitive to small changes • Changes in circulation are locally mediated by changes in O2 and CO2
    • V/Q basics: • Normal Ventilation/Perfusion is 4L/5L • Things that cause dead space (i.e. block perfusion) = PE, cardiogenic shock • Things that cause shunt (i.e. block ventilation) = shunt, pneumonia, atelectasis, airway obstruction
    • Dead Space = ventilated but not perfused • Volume of conducting airways = anatomic dead space = 2mL/kg • Alveolar dead space + anatomic dead space = physiologic dead space • Bohr equation describes the amount of physiologic dead space in a person’s lungs by comparing the amount of CO2 in arterial blood to that in exhaled gas
    • Shunt = perfused but not ventilated • Perfused areas equilibrate with arterial CO2 (mixed venous) • Low V/Q – low O2 and high CO2

    Hypoxic Pulmonary Vasoconstriction

    • Hypoxic pulmonary vasoconstriction (HPV) = diversion of blood flow from hypoxic or atelectic alveoli to an area of better ventilation or diffusion • Increase blood flow to lungs to improve gas exchange • High O2 tension and hypocapnia vasodilate pulmonary vessels so they can pick up more O2 • Hypercarbia and acidosis cause vasoconstriction → increase PVR

    Ventilator Modes

    • Pplat is a reflection of the pressure inside the alveoli at the end of inspiration where there is no airflow and directly correlates with lung compliance • Higher Pplat indicates lower compliance
    • Restrictive lung disease – reduced compliance limits expansion of lungs, increased resistance in lung tissue • PIP and Pplat elevated • Require higher PIP and higher PEEP due to reduced lung compliance and risk of atelectasis
    • Obstructive lung disease – increased compliance due to air trapping, loss of elasticity due to overexpansion of lungs, increased airway resistance • PIP elevated, Pplat normal or elevated depending on degree of air trapping • Require higher PIP to overcome airway resistance with potentially normal or elevated Pplat depending on degree of hyperinflation with lower PEEP

    Proper Mask Technique

    • The position of the mask on the face is crucial for effective use.
    • To hold the facemask in place, the left thumb and index finger should form a "C" shape around the collar.
    • The middle and ring fingers should be placed on the bony part of the mandible to compress the mask onto the face and lift the chin.
    • The 5th finger can be placed at the angle of the mandible to provide additional support and perform an anterior jaw thrust.

    Chin Lift

    • The chin lift technique pulls the hyoid bone anteriorly, which in turn pulls the epiglottis and posterior tongue superiorly and anteriorly.
    • This movement results in the epiglottis and posterior tongue moving away from the posterior pharyngeal wall.
    • The chin lift technique is more effective in increasing movement at the C1/C2 level compared to the jaw thrust maneuver.

    Jaw Thrust

    • The jaw thrust technique involves placing the tips of the fingers behind the angle of the mandible bilaterally and lifting toward the ceiling.
    • This action pulls the jaw anteriorly, which in turn lifts the base of the tongue away from the posterior pharynx.
    • Larson's maneuver is a variation of the jaw thrust, but it is essentially an exaggerated version of the technique.

    Oral Airways

    • Only used in unconscious patients
    • OPA (Oropharyngeal Airway) pulls the tongue and epiglottis away from the posterior pharyngeal wall, creating a channel for air passage
    • Does not enter the larynx
    • Different types of OPAs: Berman, Guedel, Williams, and Ovassapian (used for bronchoscopy)
    • Use a tongue blade to assist in placing the OPA
    • Determine the size of the OPA by measuring from the corner of the mouth to the angle of the jaw from the earlobe

    Nasal Airways

    • Less noxious than oral airways
    • Can be used in awake patients
    • Measure the size of the NPA (Nasopharyngeal Airway) by measuring the distance from the patient's nare to the meatus of the ear
    • The NPA should rest just above the epiglottis
    • Insert the NPA with the bevel facing the nasal septum
    • Use Afrin prior to insertion to decrease bleeding risk
    • Contraindicated in basilar skull fracture, facial trauma
    • Use with extreme caution in: anticoagulated patients, coagulopathy, pregnancy, and uncontrolled hypertension

    Cuff Types and Complications

    • High pressure/low volume cuffs are associated with a higher risk of ischemic damage
    • Low pressure/high volume cuffs are the most commonly used type, but they increase the risk of: • Sore throat • Aspiration • Unintended extubation • Difficult insertion

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    Description

    This quiz covers the clinical situations and predictors of difficult airway management, including facemask ventilation, laryngoscopy, and SGA ventilation. Learn about the definitions and indicators of difficult airway management.

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