220. Endotracheal Tube Selection

Question 1

What has been the primary determinant for the size of endotracheal tubes (ETT) in pediatric patients?

Answer 1

The age of the infant or child

Other important factors also need to be considered during pediatric airway management.

Question 2

What anatomical features are important in pediatric airway management?

Answer 2

• Large occiput
• Position of the larynx C3-4
• Shape of the epiglottis: long, omega shaped, stiff, 45° angle
• Vocal cords angled more anteriorly
• The cricoid ring considered the narrowest part

These features influenced ETT selection for decades.

Question 3

What are postintubation complications of concern for pediatric anesthesiologists?

Answer 3

• Stridor
• Development of subglottic stenosis

These complications arise due to the small subglottic diameter of the trachea.

Question 4

What physiological law explains the increased resistance to airflow in the pediatric airway?

Answer 4

Poiseuille’s law

The formula is R = 8ηL/πr^4, where r is the radius of the tracheal lumen.

Question 5

What is the standard practice for ETT selection in children younger than 8 years?

Answer 5

Uncuffed ETTs were selected

The practice was based on the belief regarding the trachea’s anatomical structure.

Question 6

What is the traditional belief regarding the narrowest part of the trachea?

Answer 6

Cricoid ring

This was later contradicted by contemporary imaging studies.

Question 7

What is the actual narrowest part of the pediatric trachea according to contemporary studies?

Answer 7

Subglottic area

This new understanding influences ETT selection.

Question 8

How does the shape of the trachea differ from the classical assumption?

Answer 8

The horizontal cross section of the trachea is elliptical shaped

Not circular, with the anteroposterior diameter longer than the transverse diameter.

Question 9

What pressure can a circular, uncuffed ETT exert on the lateral mucosa?

Answer 9

High pressure (>30 cm H2O)

This occurs while allowing leakage during positive airway pressure tests.

Question 10

What is the benefit of using a high-volume/low-pressure cuffed ETT?

Answer 10

It can seal the airway with safe pressure (20–30 cm H2O) at all levels

This improves safety during intubation.

Question 11

What is the recommended ETT size formula for uncuffed tubes?

Answer 11

1 × ETT = (Age/4) + 4

This formula is used for size selection based on age.

Question 12

What adjustment is recommended for cuffed ETT size selection?

Answer 12

Select a cuffed tube that has a 0.5-mm smaller inner diameter (ID) than an uncuffed tube

This is based on traditional calculations.

Question 13

What materials are modern cuffed ETTs made from?

Answer 13

Ultrathin (10-µm) polyurethane

This allows a safe and effective tracheal seal.

Question 14

What is a potential complication when using a cuffed ETT?

Answer 14

Obstruction due to external compression or disintegration of the wall of the ETT

This can occur during certain surgical procedures.

Question 15

What ETT type is recommended for ear, nose, and throat surgeries?

Answer 15

Oral RAE tube

It directs the ETT and anesthesia circuit away from the surgical field.

Question 16

True or False: The cricoid ring is the only fully enclosed cartilage of the trachea.

Answer 16

True

This makes it a vulnerable site.

Question 17

What must be considered for ETT selection in patients with modified anatomy?

Answer 17

Familiarity with age-appropriate size of uncuffed ETTs is essential

This is important for patients with lesions or other anatomical challenges.

Question 18

What is the purpose of measuring cuff pressure?

Answer 18

To ensure the cuff maintains safe inflation pressure

This is especially important during long surgical procedures.

Question 19

What is the formula for cuffed ETTs size selection?

Answer 19

1 × ETT = (Age/4) + 3–3.5

This formula helps in determining the appropriate size.