Week 1 Lesson 6 Airway devices

What are the four devices used to deliver gases and inhalant anesthetics to a patient?

Endotracheal tubes (ETTs), supraglottic airway devices, oxygen face masks, and anesthesia induction chambers

What is the basic definition of an endotracheal tube (ETT)?

A flexible tube inserted into the trachea

What are the four primary aims of an endotracheal tube?

Maintain the airway open, allow the passage of inhalant anesthetics and gases (like oxygen) to the lungs, protect the airway from gastric aspiration, and allow ventilation

What are three common materials used to make endotracheal tubes?

Silicone, polyvinyl chloride (PVC), and red rubber

What is a major characteristic of silicone endotracheal tubes?

They are very flexible and may require a stylet for insertion

What type of cuff is typically found on a silicone endotracheal tube?

A low-volume, high-pressure cuff

What is the most common material used for manufacturing endotracheal tubes?

Polyvinyl chloride (PVC)

What is a major physical characteristic of a PVC endotracheal tube?

It is curved and semi-rigid, and it softens with body temperature

What clinical advantage does the transparency of a PVC ETT offer?

It allows direct visualization of condensation, secretions, or blockage within the tube

What type of cuff is typically found on a PVC endotracheal tube?

A high-volume, low-pressure cuff

Why are red rubber endotracheal tubes not recommended for use?

They have a low-volume high-pressure cuff, are not transparent, and are highly prone to kinking

What is the inflatable balloon at the tip of an endotracheal tube called?

The cuff

What are the two primary aims of an ETT cuff?

To create a seal in the trachea to prevent gas leakage and to prevent aspiration of gastric content into the lungs

What is the recommended range of cuff pressure required to seal the tracheal lumen and prevent air leaks?

20 to 30 cmH2O

What is the consequence of over-inflating an endotracheal tube cuff?

Tracheal mucosa damage, including ischemia, stenosis, or rupture

What are the consequences of under-inflating an endotracheal tube cuff?

Leakage of inhalant agents (causing workspace pollution) and increased risk of gastric content aspiration (causing aspiration pneumonia)

What substance can be applied to an ETT cuff to improve its seal within the trachea?

Lubricant gel

What precaution must be taken when applying lubricant gel to an endotracheal tube?

Care must be taken not to obstruct the Murphy's eye

What tools are required to measure and control ETT cuff pressure?

A syringe and pressure measurement devices (manometers)

What is the defining characteristic of a low-volume, high-pressure cuff?

It has a small contact area with the trachea and exerts high pressure on that specific area

What is the defining characteristic of a high-volume, low-pressure cuff?

It has a larger contact area with the trachea, distributing the pressure evenly across that area

How do you premeasure the correct length of an endotracheal tube before inserting it?

Premeasure the tube against the patient from the incisors to the thoracic inlet

What does the 'size' of an endotracheal tube refer to?

Its internal diameter (ID)

What is the accuracy rate of using digital palpation of the trachea to select ETT size?

Only 46% accuracy

What is the accuracy rate of using nasal septal width compared to outer diameter to select ETT size?

Only 21% accuracy

How many endotracheal tubes of different sizes should be prepared before starting an intubation?

Prepare at least 3 tubes of different sizes but of the same length

What can be done if a selected endotracheal tube is found to be too long?

It can be cut down to the correct length

What is the guiding rule when selecting the final ETT size for a patient?

Choose the biggest size possible without damaging the trachea

According to the lecture slide, what is the procedure if the inserted ETT is too large?

Remove it and insert the next size up

According to the lecture slide, what is the procedure if the inserted ETT is too small (too snug)?

Remove it and insert the next size down

What are two potential complications of an endotracheal tube that is too long?

Endobronchial intubation and increased mechanical dead space

What is the anatomical definition of mechanical dead space in a rebreathing anesthetic circuit?

The volume from the Y-piece of the breathing circuit to the patient's incisors

What is the primary complication associated with an endotracheal tube that is too short?

Inadvertent (accidental) extubation

What are two complications of an overinflated ETT cuff?

Tracheal damage or rupture, and collapse of the ETT lumen

What are three general ETT complications related to physical obstruction?

Occlusion, obstruction, and kinking

What is a common intubation error where the tube enters the digestive system?

Esophageal intubation

What throat-related complications can result from rough intubation?

Laryngospasm and laryngeal trauma

Which sensitive species are highly prone to laryngospasm during intubation?

Cats, rabbits, pigs, and camelids

Why is gentle intubation emphasized in veterinary patients?

To avoid laryngeal/tracheal trauma and prevent life-threatening laryngospasms or vagal responses

What are three key strategies to reduce complications during endotracheal intubation?

Use a laryngoscope, ensure appropriate anesthetic depth, and desensitize the larynx with lidocaine

What form of lidocaine is used to desensitize the larynx before intubation?

Lidocaine drops or spray

What are five key advantages of using endotracheal tubes?

Better control of inhaled gas concentration, facilitates intermittent positive pressure ventilation (IPPV), prevents environmental pollution, minimizes mechanical dead space, and seals the trachea to prevent gastric aspiration

What are six disadvantages associated with endotracheal intubation?

Requires clinical skills, requires equipment (laryngoscope), requires a deeper plane of anesthesia, potential trauma to larynx/vocal folds/trachea, potential vagal response, and risk of laryngospasms in certain species

What are three other specific types of endotracheal tubes mentioned in the lecture?

Uncuffed ETTs, Cole ETTs, and armored/reinforced ETTs

What is the primary defining feature of an uncuffed ETT?

It has no inflatable cuff balloon

In which veterinary patients are uncuffed ETTs typically useful?

Pediatric patients, small dogs, or small cats

What is the main advantage of an uncuffed ETT?

There is less risk of tracheal damage from cuff overinflation

What are two disadvantages of using an uncuffed ETT?

No proper tracheal seal (increased risk of aspiration pneumonia) and increased risk of room contamination with waste inhalant gases

What is the main physical characteristic of a Cole endotracheal tube?

It is narrower at the tip of the tube (the part that goes below the larynx)

For which animal groups are Cole ETTs specifically indicated?

Avian patients, reptiles, and very small pediatric patients

How does a Cole ETT seal the airway if it does not have a cuff?

Its wider shoulder fits snugly against and seals the airway at the laryngotracheal opening

What structural component is built into the wall of an armored or reinforced ETT?

A helical wire

What is the major advantage of an armored or reinforced ETT?

It prevents tube occlusion and kinking during extreme patient neck positioning

What surgical procedures are ideal indications for an armored or reinforced ETT?

Head, neck, and ocular procedures

What is a major disadvantage of an armored or reinforced ETT?

It has a bigger outer diameter (OD) relative to its internal diameter (ID)

Where are supraglottic airway devices (SADs) anatomically positioned?

They are placed on top of the larynx but do not enter into the trachea

What is the brand name of the most common supraglottic airway device used in veterinary anesthesia?

v-gel®

For which three domestic animal species is the v-gel® device available?

Rabbits, cats, and dogs

How many times can a v-gel® device be reused and re-sterilized?

Up to 40 times

How is a supraglottic airway device introduced into a patient?

Introduced blindly (no laryngoscope required) with the animal in sternal position

How do you verify the correct positioning of a supraglottic airway device?

Check the placement using capnography

For what duration of procedures are supraglottic airway devices recommended?

Short procedures only (as an alternative to tracheal intubation)

How many sizes are available for the feline v-gel® device?

6 sizes

When placing a feline v-gel®, when should you inflate the cuff to maintain its position?

Once resistance is felt during placement

How many sizes are available for the rabbit v-gel® device?

6 sizes

What are six advantages of using supraglottic airway devices (SADs)?

Ease of placement, minimal airway injury, no laryngoscope needed, requires a lighter plane of anesthesia, no risk of tracheal damage, and less risk of laryngospasm

What are five disadvantages of using supraglottic airway devices (SADs)?

Ease of dislodgement, less control over inhaled gas concentration, does not allow intermittent positive pressure ventilation (IPPV), does not prevent aspiration of gastric content, and suitable for short procedures only

What are three clinical uses of an oxygen face mask?

Preoxygenation, oxygen supplementation during sedation, and administration of oxygen in the ICU

Why are oxygen face masks not recommended for anesthesia induction, maintenance, or recovery?

They are stressful/unpleasant, some inhalants irritate the airway, they provide no airway protection, increase mechanical dead space, deliver anesthetics inefficiently, prolong induction, waste gases, make dose control difficult, and pollute the workspace

How does using an oxygen face mask affect the duration of anesthesia induction compared to injectable agents?

It increases the duration of anesthesia induction

Why does an oxygen face mask cause significant contamination of the workspace?

It has no complete seal, allowing inhalant anesthetic gases to leak into the room

What are the primary clinical uses of an anesthesia induction chamber?

Sedation and induction of anesthesia in small mammals, exotics, or very fractious cats

What are four disadvantages of using an anesthesia induction chamber?

Possible room contamination, high usage of inhalant anesthetic agent and oxygen, unpredictable anesthetic depth, and airway irritation from inhalant agents

What is a laryngoscope?

A device that allows direct visualization of the larynx and provides good illumination during intubation

What are the three main components of a laryngoscope?

A bulb, a handle, and a blade (available in different lengths)

Where should the tip of the laryngoscope blade be placed during intubation?

At the base of the tongue, avoiding contact with the epiglottis

What anatomical structure must you strictly avoid touching with the laryngoscope blade tip?

The epiglottis

How does an overinflated ETT cuff cause tracheal necrosis or ischemia?

It compresses the tracheal mucosal capillaries, blocking local blood flow

Why is continuous capnography essential after placing any airway device?

To immediately verify proper placement in the trachea and monitor active ventilation

Why is a stylet sometimes used inside a silicone endotracheal tube?

Because silicone is highly flexible, a stylet provides the rigidity needed for insertion

What is the function of the Murphy eye on an ETT?

It acts as a safety port, providing an alternate gas pathway if the main distal tip is blocked

Where is the Murphy eye located on the ETT?

Near the patient's end (distal end) of the tube, opposite the bevel

Why does cutting down an excessively long ETT benefit the patient?

It decreases mechanical dead space and prevents endobronchial intubation

What is the consequence of endobronchial intubation?

Only one lung is ventilated, leading to severe hypoxemia and ventilation-perfusion mismatch

What are the two common models of laryngoscope blades shown in the lecture?

Miller and Macintosh blades

What is the difference in shape between a Miller blade and a Macintosh blade?

Miller blades are straight, whereas Macintosh blades are curved

Why is a lighter plane of anesthesia tolerated with a supraglottic airway device than an ETT?

SADs do not pass through the sensitive glottis and larynx, which trigger strong airway reflexes

Why are cats, rabbits, pigs, and camelids more challenging to intubate than dogs?

They are highly prone to laryngospasm, where the vocal folds close tightly upon contact

What does a flat capnography line indicate immediately after intubation?

Esophageal intubation or complete lack of ventilation/circulation

What is the primary risk of an ETT being too short?

It can easily slip out of the trachea, leading to accidental extubation and loss of airway control

How does an induction chamber irritate the patient's airways?

High concentrations of vaporized inhalants (like Isoflurane or Sevoflurane) can be highly irritating to the respiratory mucosa

How is a v-gel® device sterilized between uses?

Autoclaving or re-sterilization as specified by the manufacturer (safe up to 40 times)

Why is blind insertion of a v-gel® advantageous in rabbits?

Rabbits have a narrow oral cavity making direct visualization of the larynx extremely difficult

What happens to PVC tube rigidity inside the patient?

It softens at body temperature, reducing the risk of rigid pressure points on the tracheal wall

What is the consequence of kinking in a red rubber tube?

Complete obstruction of the airway, stopping oxygen delivery and ventilation

What is the primary reason why a face mask is used before inducing anesthesia?

To preoxygenate the patient, filling the functional residual capacity with oxygen to prevent rapid hypoxemia during apnea

What happens if you accidentally apply lubricant gel directly inside the ETT tip?

It can block the Murphy's eye or the main lumen, causing airway obstruction

What is the risk of utilizing a metal stylet in an ETT?

If the tip of the stylet extends beyond the ETT's distal bevel, it can lacerate the trachea or larynx

How does ensuring an adequate anesthetic depth prevent laryngospasm during intubation?

It suppresses the active laryngeal reflexes, preventing vocal cord closure when the larynx is touched

What does the handle of the laryngoscope contain?

The batteries that power the light bulb