Page 581 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 46: Tracheostomy 401

to both manage the airway and surgically control the innominate The other dimensions of a tracheostomy tube that are important to
artery via sternotomy. In patients with active ongoing hemorrhage the consider are its proximal and distal lengths. Patients with thick necks
priorities must be to protect the airway and prevent pulmonary soiling may require extra proximal length to ensure good fit. Use of a standard
and hypoxemia, and to control the bleeding source by direct pressure. length tracheostomy tube in these patients may result in a higher risk of
Overinflating the tracheostomy tube cuff may help to tamponade the tube dislodgement or obstruction at the tube tip, due to impingement
bleeding and is a useful first manoeuvre. In patients with ongoing hem- of the tube on the tracheal wall. Conversely, extra distal length may be
orrhage despite overinflation, the tracheostomy tube may need to be useful for bypassing areas of obstruction or distorted anatomy within the
removed to allow endotracheal intubation with a small diameter tube, trachea. Some tracheostomy tubes are constructed of wire-reinforced
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with the cuff positioned distal to the site of hemorrhage. With the airway flexible plastic and have an adjustable flange, allowing for the proximal
now protected, the innominate artery may be compressed with direct and distal lengths to be varied in individual patients.
digital pressure either from inside the trachea or by blunt dissection in Fenestrated tracheostomy tubes are typically reserved for patients that
the pretracheal plane. Surgical intervention most commonly consists of have been liberated from mechanical ventilation. These tubes have extra
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ligation of the proximate innominate artery. Repair or reconstruction in openings allowing for airflow not only around the tracheostomy but
a contaminated field risks the recurrence of bleeding due to suture line through it as well, resulting in decreased resistance to airflow through
erosion. Neurologic sequellae of innominate artery ligation are report- the native airway and larynx, thereby promoting speech. Fenestrated
edly rare, due to preserved intracranial collateral flow. Repair of TIF tubes are mostly used to evaluate whether a patient has sufficient
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with endovascular stent grafting is reported, although the long-term respiratory muscle function to breathe through the native airway while
patency of this technique remains unproven. 58 preparing for possible decannulation. Eventually, the fenestrated tubes
■ SELECTION OF TRACHEOSTOMY TUBE can be capped or “corked,” allowing patients to breathe entirely through
their native airway. Most fenestrated tubes come with two inner can-
A wide variety of tracheal tubes are available. The most fundamental nulas: one fenestrated and the other nonfenestrated which may need to
distinction between different types of tracheostomy tubes is cuffed and be placed if a return to positive pressure ventilation applied through the
uncuffed tubes. A cuffed tube is required for positive pressure ventila- tracheostomy proves necessary.
tion in the majority of ICU patients, although some chronic tracheo-
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stomy patients may be ventilated with cuffless tubes. The majority of
modern tracheostomy tube cuffs are high-volume low pressure cuffs WEANING FROM TRACHEOSTOMY
similar to those on endotracheal tubes. There are also some high-volume AND DECANNULATION
foam cuffs that may allow better conformation to an unusually shaped Clearly, the original condition that led to the decision to place the tra-
tracheal wall in some patients. When a deflatable cuff is inflated, the cheostomy should have resolved before decannulation, or removal of the
intracuff pressure should be checked regularly and maintained between tracheostomy tube, is considered. In cases of upper airway obstruction,
20 and 25 mm Hg. Pressures lower than 18 mm Hg risk creating folds in this may require documentation of resolution and airway patency by
the cuff and increasing the risk of aspiration, whereas pressures greater fiberoptic laryngoscopy. Most patients who have received a tracheo-
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than 25 mm Hg may exceed tracheal capillary perfusion pressure and stomy for prolonged mechanical ventilation may be decannulated
result in tracheal necrosis and stenosis. Once a patient is liberated from once they demonstrate sufficient respiratory reserve to breathe around
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the mechanical ventilator and breathing spontaneously, the cuff may be a capped fenestrated tracheostomy tube. Patients must also have an
deflated. A deflated cuff provides less protection against aspiration, but effective cough and the ability to achieve adequate pulmonary toilet,
cuff deflation whenever possible is an important safety measure prior although in some cases both the effectiveness of the cough mechanism
to a patient being transferred to a ward with less monitoring and lower and the amount of secretions will be improved by the removal of the
nurse to patient ratios. A patient with an inflated cuff will be at risk tracheostomy tube. Heffner proposed a checklist of conditions to be
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of complete airway obstruction should the tracheostomy tube become assessed in patients being considered for decannulation:
obstructed with secretions, whereas this risk is reduced with cuff defla-
tion. Patients who have been tolerating cuff deflation for some time • Has the upper airway obstruction resolved?
often have their tube exchanged for a cuffless tracheostomy tube. The • Is mechanical ventilation no longer required?
absence of a cuff further reduces the resistance to airflow around
the tracheostomy tube and allows for greater ease in weaning from the • Are airway secretions controlled?
tracheostomy, and can also allow for normal speech (air can pass • Is aspiration nonexistent or minimal and well tolerated?
through the larynx) and can improve swallowing function by decreasing • Does the patient have an effective cough?
pressure on the esophagus.
Tracheostomy tubes also come in a variety of sizes. The inner and Generally, once a patient is liberated from mechanical ventilation
outer diameters of the tracheostomy tube are frequently used to describe the cuff may be deflated. This is soon followed by a change to a cuffless
tracheostomy tube size. Initially, the largest suitable tracheostomy tube tube once it is clear that the patient is succeeding without mechanical
size should be inserted, to lower airway resistance and facilitate wean- ventilation and aspiration is not an ongoing issue. Often the tracheo-
ing from the mechanical ventilator as well as to reduce the chance stomy will be downsized to a smaller tube at this tube change, with the
of obstruction from secretions. The tracheostomy tube may then be possible insertion of a fenestrated tube as well. The smaller, uncuffed,
gradually downsized to allow greater airflow around the tracheostomy fenestrated tube provides the lowest degree of airflow resistance. As
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and through the native airway. Tracheostomies performed for secretion long as the patient tolerates the slightly increased work of breathing, the
clearance only are more often smaller tubes to allow continued breathing tracheostomy tube may be occluded (capped) and decannulated once it
around the tube. is clear that they have sufficient reserve to breathe around the tracheos-
Most tracheostomy tubes will have a removable inner cannula. The tomy tube. Patients must also have a manageable amount of secretions
inner cannula can be removed and either cleaned or replaced should and a strong enough cough to be able to clear their secretions into the
obstruction with blood, mucus, or a foreign object occur. This allows for oropharynx. Some patients will require the prolonged presence of a
the maintenance of a widely patent tracheostomy without the risk of a small, uncuffed tracheostomy tube to assist in clearance of secretions,
complete tube change. The downside of having an inner cannula is that which may be capped the majority of the time.
the inner diameter of the cannulated tracheostomy tube is smaller for A patient who demonstrates the inability to breathe around an
any given outer diameter, potentially resulting in more airway resistance, occluded tracheostomy tube can still be considered for a smaller tube or
but this is largely outweighed by the safety considerations. insertion of a fenestrated tube if this has not already been accomplished.

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