Discussion
The main finding of the current revision is that in the scientific
literature there are no studies with high levels of evidence, such as
randomized clinical trials, on decannulation protocols in pediatrics.
Nor analytic observational studies on cohorts of patients, where
decannulation protocols are evaluated in a prospective way. Most studies
were retrospective studies and case series, with limited numbers of
patients.
The study of Wirtz et al(14) evaluated a
decannulation protocol whose key point was to restrict the used
resources. This approach makes it unique amongst the rest of the
studies. The patients who were included had stable lung function with no
breathing obstruction and with no less than 2 months without ventilatory
support. The specific protocol consisted in laryngoscopy and
bronchoscopy, prior to decannulation, with the aim of testing the
respiratory tract. The airways are evaluated through a transnasal
approached flexible bronchoscopy and the tracheostomy cannula is taken
away in the operating room if the airways are considered to be eligible
for decannulation. Unless any complications occur, the patient is
discharged the next day. No occlusion or cannula reduction, nor
polysomnography are performed. According to this study, the spontaneous
ventilation during endoscopy is an important factor, since it allows the
testing for obstruction or dynamic collapse. The authors believe this to
be a higher ranked test, over daily routine capping, for decannulation
processes suggested in other protocols.
The implementation of the reduction of the tracheostomy tube diameter
and its occlusion are common in most protocols. However, its use is not
universal nor standardized.
One of the arguments supporting this procedure is that it may not lead
only to a successful decannulation, but also to a better adjustment to
the child to the changing physiology of their breathing tract. The
claims against the use of this protocol on a daily basis is that the
reduction in the size of the lumen may result in cannula obstruction,
due to its small diameter. During the plugging, the airway
cross-sectional area is reduced to such a level that those patients who
would not tolerate it, would tolerate decannulation.
Regarding polysomnography, in 1996, Tunkel et al,(17)published a study on the utility of polysomnography (PSG) during the
assessment when planning decannulation. PSG provides objective data on
the dynamic factors influencing the upper airways permeability when the
pharyngeal muscle tone is lowered to its top. The authors reached the
conclusion that the sleep studies close to the normal ranges of PSG are
correlated to a successful decannulation.
The existing literature is composed of retrospective revisions and case
series, and there are many discrepancies when it comes to define what a
“favorable” PSG is, for determining the tracheostomy tube extraction.(18-19)
Currently, the PSG role has expanded amongst pediatric patients with
obstructive apneas and central apneas, neuromuscular disorders as well
as respiratory support dependent patients. Gurbani et
al,(18) in the Cincinnati Children’s Hospital Medical
Center (CCHMC) studied the breathing and sleeping parameters associated
with a successful decannulation, and the agreement between
microlaryngoscopy, bronchoscopy(MLB) and polysomnography(PSG).
Microlaryngoscopy is the gold standard for the anatomy evaluation of the
airways prior to decannulation. According to this study, certain PSG
parameters which include the obstructive index (OI), apnea/hypopnea
index (AHI) and hypoventilation, with a favorable MLB, seem to be good
predictors for successful decannulation in patients with complex
airways. They concluded that the combined use of MLB and PSG rises the
predictability of successful decannulation in these children, above any
other factor on its own. So, PSG must be considered a crucial part
during the evaluation process for decannulation, especially amongst
children with important breathing airways problems. Robinson et
al,(19) also concluded that PSG may be a complementary
trial for decannulation preparation. In the study of Lee et
al,(10) the authors studied the utility of
polysomnography with occluded tracheostomy tube, as a complement for
endoscopy, for predicting the decannulation outcome.
In a retrospective review of the patients who had been tested with a PSG
before the test, 30 children were included. 26 out of those 30 had a
successful decannulation and 4 of them failed to finish the procedure.
The predictive factors of the decannulation outcome were the index of
apnea/hypopnea and desaturation events. They concluded that it is a
useful and objective tool to be used as a complement of endoscopy and
the evaluation of the functional airways.
Moreover, the anxiety generated by the decannulation process is
something that should be also taken into account. The perspective of
decannulation may cause significant anxiety on the patient and his
family.
Previously, in other studies such as Black et
al,(22)and Waddell et al,(23) panic
was mentioned as a cause of failed decannulation. The pediatric
decannulation protocol suggested in Great Ormond Street Hospital in
United Kingdom (UK) includes the prior evaluation and mandatory
psychological preparation.
Finally, given the evidence so far it is not possible to set as the
ultimate truth any of the measures or variables which were part of these
protocols, although it would be possible to give certain
recommendations.
Mitchell(16), who was previously mentioned in this
article, claimed that no consensus was reached regarding many topics,
such as the tube change frequency in a mature tracheostomy, or the size
of the cannula for children during nocturnal ventilation.
Considering the limitations of the existing studies it is possible to
mention as key points the study design, mostly retrospective, case
series and with a limited number of recruited patients.
When this review was finished, a multicentric study was published by
Schweiger and col (41)evaluating the factors
associated to a successful decannulation amongst the pediatric
population. The study was placed in 4 high complexity hospital centers
in Brazil, in the otorhinolaryngology department. Medical registers of
under-18 tracheotomized patients were analyzed in a retrospective
approach. The most common cause was post intubation laryngitis.
The outcomes showed that age and post intubation laryngitis were
associated with a higher probability of successful decannulation. On
the other hand, chronic neurological and breathing comorbidities were
linked to lower decannulation chances.
The outcomes of the decannulation predictors are also important since
they may help in the planning of the decannulation process. And, more
importantly, they may be useful for advising health workers, the
patient’s family or tutor to have realistic expectations about the
outcome.