At what inner diameter does a tracheostomy (tracheal ostomy) tube begin to create significant airway resistance?

From the Guidelines

A tracheostomy tube begins to create significant airway resistance when its inner diameter is not at least two-thirds of the tracheal lumen, as recommended by the American Thoracic Society 1. For patients with a tracheostomy, selecting a tube with an appropriate inner diameter is crucial to minimize airway resistance and ensure adequate airflow.

• The American Thoracic Society recommends that the tracheostomy tube size should not exceed two-thirds of the tracheal lumen, unless a fenestrated tube is used 1.
• This guideline is essential to prevent complications such as suprastomal collapse, distal tracheal wall granuloma, and dysphagia from esophageal compression 1.
• When selecting a tracheostomy tube, clinicians should balance the need for adequate airflow against patient comfort and anatomical constraints.
• In patients with high oxygen requirements or those being weaned from mechanical ventilation, maintaining an appropriate tube diameter is especially critical to prevent respiratory fatigue and ensure successful ventilation.
• It is also important to note that the availability of a tracheostomy tube one size smaller than usual is appropriate for emergency use if one is unable to insert a same-size tracheostomy tube after accidental decannulation 1.

From the Research

Tracheostomy Tube Inner Diameter and Airway Resistance

• The relationship between tracheostomy tube inner diameter and airway resistance is complex, with various factors influencing the resistance encountered by patients 2, 3, 4, 5, 6.
• A study published in 1996 found that with an average-sized trachea and no fenestration, the pressure required to generate flows of 40 L/min or greater exceeded 5 cm H2O and with No. 8 or No. 10 tubes exceeded 20 cm H2O 3.
• The same study noted that a fenestration routinely reduced the required pressure to less than 5 cm H2O, suggesting that the presence of a fenestration can significantly impact airway resistance 3.
• Another study published in 2013 found that the inner tube increased the resistive work of breathing by an average factor of 2.2, with the extra work of breathing imposed easily exceeding the normal total work of breathing 6.
• The results of this study suggest that selecting a larger tracheostomy tube is likely to aid weaning from mechanical ventilation 6.
• However, it is essential to consider the individual patient's needs and anatomy when choosing a tracheostomy tube, as a smaller tube may be more suitable for certain patients 2, 5.

Factors Influencing Airway Resistance

• The size of the tracheostomy tube is a critical factor in determining airway resistance, with smaller tubes resulting in higher resistance 3, 6.
• The presence of a fenestration can also impact airway resistance, with fenestrated tubes generally resulting in lower resistance than non-fenestrated tubes 3.
• The patient's anatomy, including the size of their trachea and the depth of their skin to trachea, can also influence airway resistance 2.
• The use of an inner tube can increase airway resistance, and the magnitude of this increase can vary depending on the size of the tracheostomy tube and the patient's respiratory rate and tidal volume 6.