DISCUSSION
In this retrospective cohort study, we found that CFE was not
sufficiently reliable in recommending the best feeding management in
this group of children with marked respiratory morbidity and suspected
aspiration. Our study is one of few that describes clinical outcomes
following VFSS guided feeding interventions.3, 4, 7-9Although there may be some spontaneous improvement over time in this
group of children, the significant decrease in hospitalizations and
requirement for antibiotics following feeding interventions in this
cohort is noteworthy.
A recent systematic review laments the lack of evidence on the accuracy
of CFE in detecting aspirations in children.15 Only
four studies comparing CFE with VFSS were found suitable for inclusion,
with heterogeneous patient characteristics and number of children
enrolled. Sensitivity estimates varied widely, between 0.17 (95%
confidence interval [CI] 0.05-0.37) and 0.93 (95% CI 0.76-0.99).
Specificity estimates ranged from 0.00 (95% CI, 0.00–0.52) to 1.00
(95% CI 0.16–1.00). This discrepancy is to a large extent related to
the differences in populations examined and varying rates of aspiration
identified. Our patient selection, too, ought to be borne in mind when
interpreting our results and applying conclusions to other populations:
In our study, the majority of children had clinical aspiration lung
disease, suggesting a sample with a high rate of sequelae.
Our findings of missed aspirations by CFE in this study as well as the
potentially far-reaching consequences of incorrect feeding decisions,
might support a change in practice so that VFSS is performed for all
cases of significant pulmonary morbidity and suspected aspiration. As
part of CFE, the OT identified silent aspirations based on
parent-reported dysphagia, not necessarily demonstrated during the
evaluation, as well as indirect clues, such as a wet voice, tearing,
lack of speech, etc.12, 16 This was clearly
insufficient as over 20% of children with abnormal VFSS were not
clinically detectable on CFE by even experienced OTs. Conversely, over
20% of those with normal VFSS were considered to have aspiration based
on CFE. In part, these discrepancies may be due to the fact that
aspiration may be an intermittent phenomenon. Therefore, although VFSS
should remain the gold standard, collaboration between the managing
pulmonologist and the OT who reviews the child one or more times,
remains essential.17
“No aspiration” was the most frequent finding on VFSS with all
consistencies trialed. Rather than dissuade from the importance of VFSS,
its role as giving the final green light to oral feeding must be
acknowledged. The fact that few children in this study had overt
aspiration alone by VFSS may reflect a prior decision to manage overt
aspirators by CFE alone, to avoid radiation and due to limited
resources, so that they did not enter this study of VFSS. This has been
recommended practice by some.18 In view of our
findings, it might be worth considering that VFSS could be beneficial
even for such children with obvious overt aspiration on CFE.
Silent aspiration is particularly common in children with neurological
and maturational disorders, such as e.g. Familial Dysautonomia or Down’s
syndrome. In the latter group, up to 90% of children assessed with VFSS
have been shown to display silent aspirations, not evident on clinical
swallow assessment alone.19 In our population, too,
these groups showed far more silent than overt aspirations.
Of infants under the age of one year, a critical time in terms of
oro-motor skill acquisition,20, 21 almost half showed
silent aspirations, whereas overt aspirations were rarely observed. The
silent infant aspirators were again likely to have neurological and
genetic abnormalities, as well as clinical aspiration pneumonias. In
contrast, structural defects of the airway did not give rise to silent
aspirations, as may be suspected, since these children are
neurologically intact and expected to cough upon exposure to foreign
material in the airway.6
The contribution of laryngeal penetration, occurring when liquid or food
enters the airway, but does not travel below the level of the vocal
cords,22 to aspiration lung disease is debated. In a
recent study, it did appear to be clinically significant in children
with dysphagia, and interventions, such as thickening of feeds were
associated with decreased symptoms and
hospitalization.23 Due to the inability of CFE to spot
this specific type of abnormality, we simplified our classification into
no/ overt/ silent aspirations for the purpose of comparison with VFSS
scores and did not consider penetration. It is conceivable that children
who were “caught” with penetrations on VFSS, did aspirate on other
occasions that were not captured during the brief testing event.
There are few reports in the literature on the outcome following VFSS
guided feeding intervention. We have shown that, as a group, children
improved clinically across a number of domains in the year following
such integrated feeding management. This is in keeping with a large
recent retrospective cohort study in young infants showing that
thickening feeds after observing silent aspirations on VFSS reduced the
risk of acute respiratory infection.23, 24
Decisions taken as a result of CFE and VFSS reflect not only the
anatomic and functional swallowing skills of the child. Broader
considerations include general health status, parent-child relationship,
as well as parental concerns and choices.25 Feeding
represents a key channel of communication between the child and their
caregiver, which families are often reluctant to forsake, even knowing
their child might be at risk of aspiration. Clinicians must be conscious
of and sensitive to this complex framework of interaction. Our study was
not designed to take these issues into consideration, but the first step
in this complex management decision is certainly an accurate diagnosis
of the extent and nature of aspirations occurring.
Bearing in mind our obligation to keep the radiation dose as low as
reasonably achievable, known as the “ALARA” principle, to minimize the
risk of late radiation effects in children,26 it is
our practice to perform VFSS by intermittent screening, which risks
missing penetration and aspiration events. Although VFSS radiation doses
already compare favorably with nuclear scintigraphy tests for aspiration
such as a salivagram or milk scan,27 it is expected
that through further technological progresses, diagnostic clarity will
be achieved with even less radiation, as has been described with
low-dose digital pulsed video-fluoroscopic swallow
exams.28
Our study has a number of limitations, mainly rooted in its
retrospective design and lack of control group. Firstly, in a population
with complex and multi-system medical diagnoses, such as ours, any
attempt at clear cut diagnostic labeling is bound to be inadequate. More
importantly, although it appeared that VFSS diagnosis of aspiration and
the subsequent changes in feeding interventions resulted in reduced
aspiration risk and clinical improvement, swallowing dysfunction does
tend to improve with time and maturation.21 Without an
appropriately matched control group, observed without any feeding
intervention- an ethically unacceptable concept- the bias resulting from
regression to the mean must be acknowledged. Finally, our cohort
consisted exclusively of children who were referred to VFSS following OT
assessment, due to clinical severity and complexity, and did not include
those who were managed by OT and CFE alone. A further limitation lies in
the fact that children underwent CFE and VFSS on different occasions and
each of these represent brief glimpses of a complex reality. Attention
was paid to avoid assessment during acute illness, but different scores
might not always necessarily reflect a true difference in “status” but
rather aspects of a variable occurrence of aspiration.
To conclude, in our selected population of children with high prevalence
of clinical aspiration lung disease, VFSS resulted in frequent change in
feeding route compared to prior CFE alone with ensuant clinical
improvement. We suggest to consider VFSS as part of an integrative
approach to feeding management whenever aspiration is suspected.