Practical guide: tracheostomy cannula measurements

When discussing tracheostomy tubes , it's not enough to know the type of cannula (cuff, fenestrated, metal, or plastic). A fundamental aspect is correctly interpreting its measurements , as these determine the patient's safety, comfort, and ventilation effectiveness.

These measurements are usually indicated on the "wings" of the cannula, and understanding what they mean allows for better decisions when choosing the right device.

Main measurements of a tracheostomy cannula

✅ Internal Diameter (ID)

It is the free space through which the air passes.

• Clinical significance: determines the cannula number.
• Example: a cannula No. 4 corresponds to an internal diameter of 4 mm.
• The larger the ID, the more airflow can pass through, but it must be chosen in balance with the patient's anatomy.

✅ External Diameter (OD)

It is the measurement of the total diameter of the tube.

• Function: It must match the size of the stoma to prevent air leaks or injury.
• An OD that is too large can cause pain or even tracheal injury; one that is too small can cause instability or air leakage.

✅ Length (L)

It is measured from the base of the cannula to the distal end.

• Importance: An adequate length prevents complications such as:
  - Partial airway obstruction.
  - Damage to the tracheal wall.
• The choice of length depends on age, anatomy, and medical indication.

What happens if the cannula is not the right one?

• Too large: risk of tracheal injury, discomfort, and increased difficulty in phonation.
• Too small: insufficient ventilation, air leaks, and increased breathing effort.

Therefore, the selection should always be individualized and carried out under medical criteria, considering the age, anatomy and needs of each patient.