Endotracheal Tube

Beveled end

So the distal end of the endotracheal tube (ETT) is cut at a slant. This is known as a beveled end. This is so that it the end of the tube meets the wall of the trachea. Then it less likely to become completely occluded.

Murphy eye

Most ETT have a small opening on the side just above the beveled end which is known as the Murphy eye. This is another way of ensuring that tube can still function if the end becomes occluded. It is the escape route for the air if you like.


On adult tubes there will be a cuff. The cuff is a balloon which inflates to help seal the airway. The cuff has two main functions. Firstly it ensures that the air that is put into the lungs, which is under pressure, will not then come back out of the patients mouth or nose. It also ensures that the chances of aspiration of secretions by the patient is much less likely. It does not cause complete occlusion beyond it, so some secretions will still travel past as there will be some fine folds around it. However it will prevent aspiration of larger objects/secretions.

This cuff is the main part of the tube which will help protect the airway in for example the patient who has taken a drug overdose.

Intubation marker line

Some tubes have a black marker line just above the cuff. This is a visual indicator to help when intubating. When this marker goes through the cords you need to stop advancing the tube, otherwise you run the risk of putting the tube down the right main bronchus.

Centimetre markings

The tube will have the centimeter markings running up it going up in value from the distal end in 2cm increments, ending at about 30cm at the proximal end of the tube. On a normal adult, if orally intubated, the tube will be at 21-23cm at the lips. This can vary with body habitus. The bigger patient may need the tube to go further down to reach the glottis for example. This should be charted to allow consistency and to ensure that the tube has not moved.

Pilot tube and balloon (B on diagram above)

At the distal end the pilot tube has a one way valve that will be opened when a syringe is inserted into it. This then allows the user to inject air into the cuff of the ETT, which will inflate the cuff allowing a seal to be created. As the cuff inflates, so does the pilot balloon giving the user a visual reference. The cuff should always be completely deflated when intubating and extubating the patient as this will ensure minimal trauma to the airway as the tube passes through it.

Internal Diameter

This can range from 2.5mm to 10mm. Normal range for females is 7-7.5 and for male is 7.5-8.

Size of the tube is often marked at the proximal end so that when the patient is intubated the user will know what size tube they have in.

15mm Adapter

Plastic connector at the end which will ensure that bags used for ventilation, and ventilation tubing will connect to the ETT.

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6 Ways To Be Better With a BVM
Mechanical Ventilation- Physiologic Effects
Anatomy of Adult ETT
Mechanical Ventilation- Terminology
Mechanical Ventilation- Modes of Ventilation I
Mechanical Ventilation- Modes of Ventilation II
Mechanical Ventilation- Pressure/Volume/Flow Loops
Mechanical Ventilation- Peak Pressure and Plateau Pressure
PEEP (Positive End Expiratory Pressure)
Increase the rate or the tidal volume
Ventilation Screen- What do some of those numbers mean?
Phase Variables
I:E ratios and total cycle time.
Why do we ventilate?.
Volume controlled ventilation and compliance.
Lung compliance.
How do I describe how my patient is being ventilated?
Pressure/Volume loop
AC versus SIMV
A-a gradient
Pressure Support
Pressure Support Ventilation Curves
Pressure/Volume/Flow Curves
Ventilator Induced Lung Injury
Trigger, Limit and Cycle
Ventilator Associated Pnuemonia

Originally posted 2015-03-23 11:40:27. Republished by Blog Post Promoter

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2 Responses to Mechanical Ventilation- Anatomy of the Adult Endotracheal Tube

  1. Debbie Cook says:

    Love the word habitus JD

    • Jonathan Downham says:

      It’s one of my favourite words too! Do ITU nurses want more of this kind of teaching resource? Hope to build it up over time….Let me know?

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