Endotracheal Tubes and Supraglottic Airways

Question 1

What is the major difference between supraglottic and subglottic airways?

Answer 1

1. Supraglottic does not go through the vocal cords

2. Subglottic: goes through the vocal cords

Question 2

Supraglottic Airway/LMA

Answer 2

1. Less invasive airway- non irritating to bronchial tree, less anesthetic required
2. relatively quick and easy to insert
3. requires no special equipment for insertion
4. less coughing on emergence
5. if removed inflated, secretions come out with LMA
6. Less chance of kinking, but may be more likely to dislodge
7. Can avoid mask ventilation

Question 3

ETT

Answer 3

1. Aspiration protection (GERD, full stomach, lap)
2. More “secure” airway, less like to dislodge
3. Ability to positive pressure ventilate at higher peak pressures
4. Used if post operative ventilation required (obese, lung disease)
5. Protects against laryngospasm with ETT in place

Question 4

Sizes of ETT

Answer 4

1. Based on internal diameter (ID)
   - 2.5 (mm) to 9.0 (mm)
2. Adults: 7.0-9 mm
3. Children: age divided by 4 + 4
   - compare diameter of ETT to pinky size
   - depth= ETT X3

Question 5

Premature infant size ETT vs adult size?

Answer 5

1. Premature infants= 2.5 mm ID
2. 2-years of age= 4.5 mm ID
3. Adults= 6.5-7.0 mm ID

Question 6

ETT Poiseuille’s Law

Answer 6

R= 8 X N X L/ pi r ^4

n= viscosity
l=length

Question 7

Microlaryngoscopy Tube (MLT)

Answer 7

• small diameter, longer ETT to facilitate the view of airway
• size 5.0-6.0 mm
• OTO cases normally use this

Question 8

Depth of ETT

Answer 8

• usually 22-26 depth

Question 9

Cuffed ETTs: low volume, high volume?

Answer 9

• low volume, high pressure

- high volume, low pressure

Question 10

Nasal RAE insertion tips

Answer 10

• place ETT in warm saline container
• mix Afrin with 2% lidocaine jelly
• dilate nasal passage with nasal trumpets lubricated with above solution
• use McGill forceps to guide tube, but often with external laryngeal manipulation, ETT will directly & naturally want to go through vocal cords

Question 11

Laryngectomy/Tracheal Stoma ETTs

Answer 11

• “J tube”
• placed through stoma
• can be done awake or asleep
• a regular tube can be used, but these are much more convenient

Question 12

Supraglottic Airway: Laryngeal Mask Airway (LMA)

Answer 12

• Dr. Archie Brain
• essentially a big oral airway that fills entire pharynx
• LMA is trade marked
• ASA difficult airway algorithm stresses early insertion of LMA in the event of difficult mask
• reusable, no bells and whistles.
• no latex
• some single use LMA
• cuff pressure should be less than 60 cm H2O
• if controlled ventilation used, peak inspiratory pressure should be kept below 20 cm H2O

Question 13

Insertion technique for LMA: cuff inflation volume

Answer 13

-cuff inflated to leak of less than 20 cm H2O

max cuff volume for size 4-5= 30-40 ml

Question 14

Proseal LMA (esophageal drain)

Answer 14

• Has 4 main parts: cuff, inflation line with pilot balloon, airway tube, and drain tube.
• size 4 for adult women and 5 for most adult men
• smaller and shorter than LMA-Class, wire reinforced which makes it more flexible
• accessory vent under drainage tube prevents secretions from pooling
• allows liquids and gases to escape from the stomach, which reduces risk of gastric insufflation and pulmonary aspiration
• when inserting patient’s head should be in sniffing position
• associated with higher leak pressures
• peak inspiratory pressure should be kept below 30 cmH20

Question 15

LMA supreme

Answer 15

• fixation tabs
• bite block
• do not need muscle relaxant with these
• single use, built in drain tube and works to protect airway from epiglottic obstruction
• gentle curve to allow for easier insertion and more stable placement

Question 16

What supraglottic can you intubate through?

Answer 16

• LMA Fastrach

- has metal handle attached to it

Question 17

LMA C Trach

Answer 17

• weights less than 8 ounces and is totally wireless
• 30 minutes of uninterrupted viewing
• has dedicated Et tube with atraumatic tip
• two fiberoptic bundles emerge at the distal end of the airway tube under the modified epiglottic elevating bar, which optimizes the light source and enables image transmission to the viewer while protecting the airway tube from obstruction.
• lifts epiglottis out of the way
• ET can pass through it

Question 18

i-gel

Answer 18

• accurate and natural positioning
• positions itself over the laryngeal framework, providing a reliable perilaryngeal seal without the need for inflatable cuff
• integrated bite block and belly suction
• theres a line on i-gel that tells you how deep to place it

Question 19

Complications of Supraglottic Airways

Answer 19

• sore throat, trauma from insertion
• nerve injury including hypoglossal nerve- vocal cord paralysis (reported as temporary), excessive high cuff pressures, use of nitrous oxide
• gastric distention and aspiration
• nitrous can work its way into cuff*

Question 20

Ring, Adair, Elwin (RAE) ETTs

Answer 20

• can bend to whatever way you need them to
• heat them up and they will stay that way
• when surgeons working on the face can adjust how tubing falls
• can use metal stylet in oral BUT NEVER nasal*

Question 21

Standard Insertion of LMA-Classic

Answer 21

1. midline or slightly diagonal approach with cuff fully deflated
2. Head should be extended and neck flexed (sniffing)
3. jaw can be pulled down by assistant. the tube portion is grasped and the index finger pressing on the point where the tube joins the mask
4. It is pressed upward against the hard palate
5. if mask feels like tip is flipping over on itself, remove and restart

Question 22

LMA- Unique

Answer 22

• single use
• same insertion as LMA-classic
• protection against infection

Question 23

LMA- Flexible

Answer 23

• wire reinforced tube that is longer and narrower than LMA-CLassic
• single use or reusable is also available
• can be bent in any angle without kinking
• allows for positioning away from surgical field
• less likely to become displaced
• designed for surgical procedures: head, neck, and upper torso
• NO bite block***
• NOT for MRI

Question 24

LMA Fastrach

Answer 24

• can intubate through this (large enough for 9.0 ET to be placed through it)
• tip is slightly curved to prevent traumatic insertion
• latex free
• size 3-5
• for insertion does not require placing fingers into the patient’s mouth
• muscle relaxants not needed for insertion
• NOT for MRI*