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?

All of the above Signup and view all the answers

What is a desaturation risk factor?

All of the above Signup and view all the answers

What is the acronym for difficult FONA airway?

SHORT Signup and view all the answers

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

Lower FRC and increased oxygen consumption Signup and view all the answers

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

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

What is the purpose of apneic oxygenation?

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

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

15 LPM via NC Signup and view all the answers

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

Cannot deliver >6 LPM for extended periods Signup and view all the answers

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

30-45% Signup and view all the answers

What is the primary function of bronchial arteries?

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

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

4:5 Signup and view all the answers

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

It is redistributed to areas of better ventilation Signup and view all the answers

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

Higher PIP and higher Pplat Signup and view all the answers

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

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

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

Vasodilation to help vessels pick up more oxygen Signup and view all the answers

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

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

What is the correlation between Pplat and lung compliance?

Higher Pplat indicates lower compliance Signup and view all the answers

What is required for preoxygenation?

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

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

All of the above 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?

4% Signup and view all the answers

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

0.40 Signup and view all the answers

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

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

What is the principle behind apneic ventilation?

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

Apneic oxygenation does not require a patent airway

False Signup and view all the answers

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

All of the above Signup and view all the answers

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

Increased FiO2 delivery Signup and view all the answers

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

By utilizing the nasopharynx as an oxygen reservoir Signup and view all the answers

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

60 LPM Signup and view all the answers

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

Because it is more comfortable Signup and view all the answers

Where should the top of an adult face mask sit?

On the bridge of the nose Signup and view all the answers

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

The pupils Signup and view all the answers

Where should the bottom of an adult face mask sit?

Between the lower lip and chin Signup and view all the answers

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

To compress the mask to the face while lifting the chin Signup and view all the answers

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

5th finger Signup and view all the answers

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

The shape of the letter C Signup and view all the answers

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

To prevent gastric distention Signup and view all the answers

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

less than 20-25 cm H2O Signup and view all the answers

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

Reposition airway and ventilate Signup and view all the answers

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

Insert an airway adjunct Signup and view all the answers

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

Use a 2-handed mask technique Signup and view all the answers

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

Proceed to intubation, SGA, or reverse sedation Signup and view all the answers

Signs of inadequate ventilation are the opposite of confirmation of intubation

True Signup and view all the answers

Decreased SPO2 is a late sign of inadequate ventilation

True Signup and view all the answers

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

Tongue Signup and view all the answers

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

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

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

To exaggerate the jaw thrust and open the airway further Signup and view all the answers

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

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

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

It can be used in awake patients Signup and view all the answers

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

Basilar skull fracture Signup and view all the answers

What is the correct way to insert a nasal airway?

With the bevel facing the nasal septum Signup and view all the answers

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

To push the tongue out of the way Signup and view all the answers

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

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

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

They do not enter the larynx. Signup and view all the answers

Which type of OPA is this?

Guedel Signup and view all the answers

What type of OPA is this?

Williams Signup and view all the answers

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

Rescue ventilation for difficult mask ventilation and failed intubation Signup and view all the answers

What are two concerns when using supraglottic airway devices?

Concern of aspiration because airway is not protected Signup and view all the answers

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

To decrease the risk of occlusion Signup and view all the answers

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

<20-25 cmH2O Signup and view all the answers

Ett Cuffs should be inflated to what pressure?

Minimum occlusive pressure Signup and view all the answers

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

Because cuffs are permeable to oxygen and nitrous oxide Signup and view all the answers

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

Greater risk of ischemic damage Signup and view all the answers

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

All of the above Signup and view all the answers

What acronym is used to predict difficult SGA placement?

RODS Signup and view all the answers

What is the optimal ETT depth for adults?

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

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

7-7.5 mm for females, 7.5-9.0 mm for males Signup and view all the answers

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

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

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

3x ETT size Signup and view all the answers

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

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

What is part of the mandatory setup?

ASS (Ambu, suction, stethoscope) Signup and view all the answers

What is the sniffing position ?

Neck flexion and atlanto-occipital extension Signup and view all the answers

What is the preferred method of preoxygenation?

Tidal volume method Signup and view all the answers

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

100% FiO2 at 10-12 L/min for 3 minutes 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?

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

What are the alternate preoxygenation methods?

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

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

To prevent regurgitation by applying pressure to the cricoid cartilage Signup and view all the answers

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

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

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

True 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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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.