Tracheostomy Sizes and Comparison Tool
Compare different tracheostomy tube sizes for inner diameter, outer diameter, length and cuff
NOTE: All Portex, Bivona, Uniperc, Tracoe, and Shiley Flexible Tracheostomy Tubes are ISO sizes. All other Shiley tubes use the Jackson sizing for the initial tube size selection.
Sizing of the Tracheostomy Tube
Choosing the appropriate inner and outer diameter sizes of the tracheostomy tube are important when recommending the initial tracheosotmy tube size or tracheostomy tube changes. When determining the appropriate diameter of the tracheostomy tube, there are a few aspects to consider: lung mechanics, upper airway resistance and airway clearance, ventilation and communication/speech needs, and indications for the procedure (Mitchelle, 2013). These requirements may change over time.
Sizing is important when recommending tracheostomy tube changes. A tracheostomy tube from one manufacturer may not correspond to the same size from a different manufacturer as they may have different internal/external diameters or length. A clinician recommending downsizing needs to be aware that one size 6 tracheostomy tube is not necessarily the same inner/outer diameter or length as a different brand of size 6 tracheostomy tube. The clinician should assess the inner and outer diameter measurements and length to compare the tracheostomy tubes and ensure the appropriate selection. The above comparison tool can help to show the differences between tracheostomy tubes.
ISO versus Jackson Tracheostomy Tube Sizing
It is also important to understand that different manufacturers follow different sizing guidelines. Some tracheostomy tubes utilize the Jackson sizing system, while other tubes use the International Organization for Standardization (ISO) method. With the exception of Shiley Flexible Tracheostomy Tubes, the Shiley dual cannula tracheostomy tubes still use the Chevalier Jackson sizing system. The appropriate dimensions are listed on the flange of the tracheostomy tube.
ISO is a worldwide federation of national standardization bodies that is concerned with the basic requirements and method of size designation of tracheostomy tubes made of plastics or rubber. It requires that tracheostomy tubes are sized according to the most narrow part of the inner diameter which includes the inner cannula if it is required to connect to the ventilator circuit. The inner diameter of the outer cannula is used for tubes with a single cannula. The inner diameter of the inner cannula is used if that tube requires the inner cannula to connect to mechanical ventilation. The outer cannula is measured as the largest diameter of the outer cannula.
It is important when selecting an appropriate tube to understand the differences in sizing. There is an unavoidable compromise to be made between a desire to maximize the functional internal diameter (and thereby reduce airway resistance and the work of breathing during weaning) and a need to limit the OD to approximately three-quarters of the internal diameter of the trachea (in order to facilitate airflow through the upper airway when the cuff is deflated). When the cuff is inflated, a smaller inner diameter will increase the resistance through the tube and airway clearance may be more difficult. Furthermore, if the tube selected is too small, the cuff may need to be overinflated to maintain positive pressure ventilation. Complications from overinflating the cuff can result in tracheal damage such as necrosis and stenosis. However with a deflated cuff, the individual will also be breathing around the tracheostomy tube and therefore the size of the inner diameter is less important. With a speaking valve or cap in place, a smaller outer diameter will allow for easier exhalation around the tracheostomy tube and through the upper airway.
Tracheostomy Tube Length
The length of the tracheostomy tube may also vary between tubes of the same inner diameter for different manufacturers. These variations are not commonly appreciated, but may have important clinical implications. If the tracheostomy tube is too short, the end of the tube can hit against the posterior tracheal wall.
Tracheostomy tubes are available in standard lengths or extra lengths. Extra length tracheostomy tubes can be constructed with extra proximal length or distal length.
Extra proximal length tubes are for patients with thicker necks (obese patients). Standard tracheostomy tubes are too short and too curved for proper positioning due to the distance between the skin and the trachea. Therefore, standard tracheostomy tubes are more likely to be dislodged in patients with thick necks.
Extra distal length tubes are used to bypass tracheal anomalies such as stenosis or malacia. A study by Rumbek (1999) of 37 patients with substantial tracheal obstruction caused failure to wean. Insertion of a longer tracheotomy tube relieved the obstruction and allowed 35 out of 37 patients to be weaned from the ventilator within 1 week.
There are also adjustable tracheostomy tubes which have a movable flange so that the length of the tracheostomy tube from skin surface to trachea can be adjusted at the bedside. A locking mechanism on the flange maintains the chosen tube length. These tubes are used for patients with atypical anatomy. The locking mechanism often fails after a period of time and therefore these tubes are for short term use. Custom tubes are available with fixed flanges that can be made with specific sizes on an individual basis.
Tracheostomy Tube Curvature
Tracheostomy tubes can be curved or angled. These features can help to improve the fit of the tracheostomy tube into the airway. Patients with a fenestrated tracheostomy tube may need a particular angled tracheostomy tube so that the fenestration fits in an appropriate place in the trachea, and not against the anterior or posterior tracheal wall.
Not all tracheostomy tubes are created equally. A tracheostomy tube is not a one size fits all. Each patient should be assessed individually to best meet his or her needs.