Patients undergo the formation of a tracheostomy for four main reasons:1
- To relieve upper-airway obstruction due to tumour, surgery, trauma, foreign body, or infection
- To prevent laryngeal and upper airway damage due to prolonged trans-laryngeal intubation
- To allow easy or frequent access to the lower airway for suctioning and secretion removal
- To provide a stable airway in a patient who requires prolonged mechanical ventilation or oxygenation support
Tracheostomies are usually formed between the 2nd and 3rd tracheal rings. In the ICU, the majority are formed by the percutaneous dilatational technique, whereas on the ENT wards, you are more likely to encounter a patient who has had a surgical tracheostomy. Apart from the obvious time and cost savings associated with the percutaneous technique, there may be other advantages, such as a lower incidence of wound infection.2
You will encounter many different tracheostomy tubes in hospitalised patients, but also in patients in the community and presenting to the Emergency Department. It is important to know the types of tracheostomy tube that are in common use. They are available with and without a cuff, with or without a fenestration to facilitate speech, and with or without an inner cannula to help with the clearance of secretions. Cuffed tubes are required when positive pressure ventilation is being used, and provide a barrier against the aspiration of secretions, although even a correctly inflated cuff cannot provide absolute protection. Fenestrated tubes allow for gas to pass upwards through the vocal cords to facilitate speech. However, this fenestration will also allow the downward passage of secretions.
It is important to know that some tracheostomy tubes (for example, Shiley™ tubes) need the inner cannula to be in-situ for a breathing circuit to be attached, whereas others (for example, Portex™ tubes) can be attached can be attached to the circuit with or without the inner cannula in place.
The tracheostomy tube must be the right size for the patient. Tubes that are too long can cause trauma, discomfort, cough and unilateral ventilation. Short tubes can result in ineffective ventilation, ulceration to the posterior tracheal wall, and displacement or dislodgement, causing surgical emphysema, (especially with fenestrated tubes, when gas leaks through the fenestration into soft tissues), loss or airway and death. Tracheal tubes that are too wide can also cause ulceration and erosion, with the possibility of tracheo-oesophageal fistula, discomfort, difficulty swallowing, the inability to achieve voice and difficult tube changes. Narrow tubes can case inadequate ventilation and increased respiratory effort, leaks, and problems with clearing secretions.3
Ideally, the outer diameter (OD) of a tracheostomy tube should be about 2/3 to 3/4 of the diameter of the trachea, to minimise trauma to the tracheal wall and allow the passage of gas around the tube to facilitate speech. A 10mm OD tube is appropriate for most adult females and 11mm for most males,4 meaning that in general, a size 6.0-7.0mm inner diameter (ID) tube will be appropriate for most women, and a size 7.0-8.0mm ID for most men (see table below). Choosing the correct diameter tube allows a good seal to be achieved with cuff pressures of 20-25mmHg or 25-35cmH2O, decreasing the likelihood of pressure injury to the tracheal mucosa.4
By convention, the inner diameter (ID) of tracheostomy tubes is given as the ID of the outer tube if the breathing circuit can be attached to the outer tube (e.g. Portex™ tubes). If an inner cannula is required for connection to the breathing circuit, the ID is given as that of the inner cannula (e.g. Shiley™ tubes).
Measurements of some commonly used tracheostomy tubes are given in the table below. It can be seen that the nomenclature differs between different brands, for example, Portex™ tubes have ‘sizes’ equal to the ID of the tube without its inner cannula, while the given ‘size’ of Shiley™ tubes does not equate to any measurement, but closely approximates to the ID of the inner cannula (which must be in place for a breathing circuit to be attached). It can also be seen that different brands have different ratios of ID to OD, with the Portex™ Uniperc™ having the most favourable ratio, due to its thinner-walled, metal-reinforced tubing.
The Uniperc™ is an example of an adjustable flange tracheostomy tube. These devices consist of a tube which passes through a flange with a locking device, allowing the length of the tube inside the trachea to be adjusted. As can be seen from the table, the potential length of these tubes is significantly greater than the fixed length tubes. They are therefore useful in patients with a large amount of tissue overlying the trachea, such as obese patients.
As obesity becomes more prevalent, it is important to ensure that a long enough tube is selected. An adjustable flange tracheostomy tube is one option, but an extended proximal length tube, such as the Shiley™ XLT™ Proximal, may also be appropriate. Data from one study suggest that standard tubes, such as Portex™ Blueline Ultra™ and standard length Shiley™ tubes, are too short in general.5 In this study, measurements were taken of the distance from the skin to the trachea (stomal length), the angle of stoma formed (stomal angle) and the distance from the tip of the tracheostomy tube to the carina. Data from 50 non-morbidly obese patients (body mass index of less than 35) showed an average stomal length of 26mm, stomal angle of 113 degrees and tube to carina distance of 43mm. A size 8.0 Portex™ Blueline Ultra™ tube has a stomal length of only 9mm, is set at an angle of 90 degrees and is 75mm in length. A standard Shiley™ tube has a continuous curve (so has no fixed stomal length), an overall angle of 135 degrees and is 81mm in length. The authors recommend that tracheostomy tubes of this nature (without an adjustable flange) should be redesigned, with 10mm added to both the stomal and intra-tracheal lengths (an increase in overall length of 20mm) and their stomal angle changed to 110-120 degrees.
Great care must therefore be taken with the choice of tracheostomy tube. If in doubt, an adjustable flange device offers the opportunity to alter intra-tracheal length after placement.
Patients with tracheostomies require close monitoring. The stoma must be checked regularly, for signs of infection, bleeding, ulceration, sinus formation and surgical emphysema. If sutures are used to secure the flange to the skin their integrity should be checked. ‘Stay’ sutures are sometimes placed at the time of surgery. These sutures run from the lateral edges of the incised trachea to the skin, where they are secured with tape. They are placed as a safety measure, so that the tracheal opening can be pulled up to the skin surface in the event of accidental decannulation. Their presence should be noted and their integrity checked regularly. These are removed when the stoma is well formed as they then become unnecessary. The stoma should be dressed regularly to prevent infection and to protect the skin from pressure damage.3
The tracheostomy tube should be checked regularly for signs of damage and displacement. In the case of standard tracheostomy tubes, movement of the flange away from the skin surface suggests displacement. With adjustable flange devices, it is important to remember that the tube can also slip through the flange, so a careful note must be made of the depth at which the tube should be locked. Tracheostomy tapes should be secure, and tight enough that one or two fingers can be placed beneath them. If an inner cannula is in place, it should be removed, inspected and cleaned regularly to ensure patency, and spare cannulae should always be at the bedside.3
CHANGING A TRACHEOSTOMY TUBE
Depending on where you work, you may be asked to help change a tracheostomy tube. There are a variety of reasons why this is done: to reduce the size of the tube during weaning or due to incorrect size; tube or flange fracture; cuff failure; routine changes and rarely, to increase the size of tube to allow for the passage of a bronchoscope.6 Routine changes are performed every 60-90 days, because tubes perish over time, increasing the risks of device failure and chronic infection.
You should not attempt to change a tracheostomy tube without supervision unless you have the correct experience and skills. Routine changes should not be performed if the patient has become sick or unstable – the risks of potential device failure and chronic infection must be weighed against the risks of changing the tube.6
At least two skilled clinicians should be present during a tracheostomy tube change and at least one should have advanced airway skills. Full resuscitation equipment must be readily available, including equipment and drugs to perform emergency oral intubation if required. A range of tracheostomy tubes of different sizes should be available, and the tube should be well lubricated prior to insertion.
It is advisable to use an introducer of some sort to guide the tube into position. This may be provided with the tube (in the form of a guide-wire or obturator) or improvised: a cut-off suction catheter or nasogastric tube will suffice. The intruducer should be inserted into the old tube and down into the trachea, the tube removed over the introducer, then the new tube inserted over the introducer. In the case of a very well established stoma, an introducer may not be necessary.
In all cases, a good hint is to insert tracheostomy tubes with their long axis perpendicular to the long axis of the trachea initially, then rotate into alignment as the tube is passed downwards.