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.