Quantitative classification of pediatric swallowing through accelerometry
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English

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Quantitative classification of pediatric swallowing through accelerometry

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8 pages
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Description

Dysphagia or swallowing disorder negatively impacts a child’s health and development. The gold standard of dysphagia detection is videofluoroscopy which exposes the child to ionizing radiation, and requires specialized clinical expertise and expensive institutionally-based equipment, precluding day-to-day and repeated assessment of fluctuating swallowing function. Swallowing accelerometry is the non-invasive measurement of cervical vibrations during swallowing and may provide a portable and cost-effective bedside alternative. In particular, dual-axis swallowing accelerometry has demonstrated screening potential in older persons with neurogenic dysphagia, but the technique has not been evaluated in the pediatric population. Methods In this study, dual-axis accelerometric signals were collected simultaneous to videofluoroscopic records from 29 pediatric participants (age 6.8 ± 4.8 years; 20 males) previously diagnosed with neurogenic dysphagia. Participants swallowed 3-5 sips of barium-coated boluses of different consistencies (normally, from thick puree to thin liquid) by spoon or bottle. Videofluoroscopic records were reviewed retrospectively by a clinical expert to extract swallow timings and ratings. The dual-axis acceleration signals corresponding to each identified swallow were pre-processed, segmented and trimmed prior to feature extraction from time, frequency, time-frequency and information theoretic domains. Feature space dimensionality was reduced via principal components. Results Using 8-fold cross-validation, 16-17 dimensions and a support vector machine classifier with an RBF kernel, an adjusted accuracy of 89.6% ± 0.9 was achieved for the discrimination between swallows with and with out airway entry. Conclusions Our results suggest that dual-axis accelerometry has merit in the non-invasive detection of unsafe swallows in children and deserves further consideration as a pediatric medical device.

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Publié le 01 janvier 2012
Nombre de lectures 8
Langue English

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Merey´ etal. JournalofNeuroEngineeringandRehabilitation2012,9:34 JOURNAL OF NEUROENGINEERING
http://www.jneuroengrehab.com/content/9/1/34 AND REHABILITATIONJNER
RESEARCH OpenAccess
Quantitativeclassificationofpediatric
swallowingthroughaccelerometry
1* 2 4 3 1Celeste´ Merey´ ,AzadehKushki ,ErvinSejdic´ ,GlennBerall andTomChau
Abstract
Background: Dysphagiaorswallowingdisordernegativelyimpactsachild’shealthanddevelopment.Thegold
standardofdysphagiadetectionisvideofluoroscopywhichexposesthechildtoionizingradiation,andrequires
specializedclinicalexpertiseandexpensiveinstitutionally-basedequipment,precludingday-to-dayandrepeated
assessmentoffluctuatingswallowingfunction.Swallowingaccelerometryisthenon-invasivemeasurementof
cervicalvibrationsduringsandmayprovideaportableandcost-effectivebedsidealternative.Inparticular,
dual-axisswallowingaccelerometryhasdemonstratedscreeningpotentialinolderpersonswithneurogenic
dysphagia,butthetechniquehasnotbeenevaluatedinthepediatricpopulation.
Methods: Inthisstudy,dual-axisaccelerometricsignalswerecollectedsimultaneoustovideofluoroscopicrecords
from29pediatricparticipants(age6.8 ±4.8years;20males)previouslydiagnosedwithneurogenicdysphagia.
Participantsswallowed3-5sipsofbarium-coatedbolusesofdifferentconsistencies(normally,fromthickpureetothin
liquid)byspoonorbottle.Videofluoroscopicrecordswerereviewedretrospectivelybyaclinicalexperttoextract
swallowtimingsandratings.Thedual-axisaccelerationsignalscorrespondingtoeachidentifiedswallowwere
pre-processed,segmentedandtrimmedpriortofeatureextractionfromtime,frequency,time-frequencyand
informationtheoreticdomains.Featurespacedimensionalitywasreducedviaprincipalcomponents.
Results: Using8-foldcross-validation,16-17dimensionsandasupportvectormachineclassifierwithanRBFkernel,
anadjustedaccuracyof89.6% ±0.9wasachievedforthediscriminationbetweenswallowswithandwithoutairway
entry.
Conclusions: Ourresultssuggestthatdual-axisaccelerometryhasmeritinthenon-invasivedetectionofunsafe
swallowsinchildrenanddeservesfurtherconsiderationasapediatricmedicaldevice.
Keywords: Swallowing,Dysphagia,Dual-axis,Accelerometry,Classification
Background [2]. In neurogenic dysphagia, swallowing difficulties arise
Feeding disorders encompass a broad range of problems secondary to neurological impairments. Particularly, in
associated with eating solid and liquid foods. Difficulty neurological conditions such as cerebral palsy, incidence
with the process of swallowing is known as dysphagia, ofdysphagiaishigh[3].Dysphagiaimpactsthehealthand
and can occur in both adult and pediatric populations well-beingofachildasthedisordermayleadtomalnutri-
[1]. Epidemiologic data on the prevalence of dyspha- tion, dehydration and impairment of physical growth [4].
gia in children is not readily available; however feeding Dysphagiacanalsoinducefeeding-relatedstressandchal-
disorders as a whole are estimated to be present in a lenges, affecting the psychosocial well-being of the child,
significant and increasing portion of the pediatric popu- family and other caregivers [2]. A particularly dangerous
lation: in 25% to 45% of typically developing children and condition, aspiration pneumonia, is frequently associated
in 33% to 80% of children with developmental disorders with dysphagia [5]. Silent aspiration, that is, the entry of
foodstuffs into the airway in the absence of a cough or
*Correspondence:celeste.merey@utoronto.ca otherovertresponse,isgenerallydifficulttodetectduring1InstituteofBiomaterialsandBiomedicalEngineering,UniversityofToronto,
routineclinicalswallowingassessmentswithoutvideoflu-Toronto,Ontario,Canada
Fulllistofauthorinformationisavailableattheendofthearticle oroscopy. Recently, Weir and colleagues reported that
©2012Merey´ etal;licenseeBioMedCentralLtd. ThisisanOpenAccessarticledistributedunderthetermsoftheCreative
CommonsAttributionLicense(http://creativecommons.org/licenses/by/2.0),whichpermitsunrestricteduse,distribution,and
reproductioninanymedium,providedtheoriginalworkisproperlycited.Merey´ etal. JournalofNeuroEngineeringandRehabilitation2012,9:34 Page2of8
http://www.jneuroengrehab.com/content/9/1/34
silent aspiration occured frequently in children with dys- during the feeding protocol, in turn, generating more
phagia;over80%oftheirsampleof300childrenaspirated contaminant vibration signals. In addition, children with
silently [6]. Further, silent aspiration was significantly neurogenic dysphagia often exhibit behavioral feeding
associatedwithneurologicalimpairment. challenges (e.g., food refusal, food expulsion, disruptive
Early evaluation by a clinical team may greatly reduce mealtime routines, short attention span, impulsivity and
healthissuesthatcanresultfromdysphagia.Inparticular, distractibility) that further complicate the assessment of
instrumentalevaluationsofswallowingfacilitatethevisu- swallowing function [3]. Thus, the classification of swal-
alizationofthebolustrajectoryandmotionofanatomical lowing accelerometry in the pediatric population with
structures throughout the different phases of swallowing. neurologicalimpairmentordiseaselikelypresentsfurther
The current standard is the videoflouroscopic swallow analytical challenges than those encountered in the adult
study (VFSS), where the patient swallows barium coated case. In 2006, Lee et al. proposed a radial basis classi-
substances of various consistencies while lateral X-ray fier for the classification of uniaxial vibrations associated
images of the oral cavity, pharynx, larynx and upper with swallowing activity in children [14]. Although they
esophagus are displayed in real-time for live viewing and achieved an 80% adjusted accuracy, their classifier only
recordedforsubsequentreview.Asonepartoftheassess- detectedaveryspecificevent,i.e.,airwayentrywithinspi-
ment, the clinical team discerns whether or not the bolus ratory airflow. Dual-axis accelerometry provides unique
passes into the airway, either into the laryngeal vestibu- signal information in each axis of vibration (superior-
lum above the vocal chords or past the vocal chords and inferior and anterior-posterior) attributed to the motion
intotheinferiorairways[7]. of the hyoid and larynx [15,16]. Dual-axis accelerometry
Clinical evaluations of the health of the swallow have may serve as an informative adjunct to clinical swallow
yielded varying levels of agreement amongst clinicians assessment,mayprovideameansoftimelyandrepeatable
and trained experts [8]. Although perfect agreement was non-invasive assessment of swallowing function (espe-
not achieved, expert diagnosis matched on most occa- cially post-stroke) and may help to streamline referrals to
sions, indicating the effectiveness of VFSS as a means videofluoroscopy, reducing unnecessary exposure to ion-
of detecting unsafe swallowing. Hind et al.’s study [9] izing radiation and reducing radiology wait-times. The
resulted in agreement rates of 93-95% in clinical diagno- presentstudyaimstogeneralizedetectiontoanyinstance
sis of an unhealthy swallow. More recently, Bryant et al. ofairwayentryinchildrenwithneurogenicdysphagiaand
[8]foundahighervariabilityandloweraccuracyofdetect- to build upon methods of data collection, processing and
ingunhealthyswallows:between77%and88%agreement classification which have proven to be effective in adult
amongstparticipatingclinicians. populations[12].
VFSS is not without its shortcomings. Proper inter-
pretation of the swallow usually requires an experienced Methods
practitioner or a team of assessors. The method itself Dataacquisitionandswallowidentification
also exposes children to ionizing radiation and there- Cervical accelerometry swallowing samples were col-
fore should be used minimally [7]. As well, the process lected from 29 patients (aged 6.8 ± 4.8, 20 male) of the
is expensive both in terms of equipment and human Holland Bloorview Kids Rehabilitation Hospital’s feeding
resources.Furthermore,VFSScanonlyprovideasnapshot clinic. Participants of the feeding clinic all had neurolog-
of a patient’s swallowing function, despite the fact that ical conditions such as Cerebral Palsy, seizure disorder,
thisfunctioncanvaryfromdaytoday.Finally,manychil- developmental delay, brain injury and Downe Syndrome.
drenfindVFSSfrighteninganduncomfortable[10].These All participants were diagnosed with probable feeding
issues have motivated a search for alternative means of disorders at a previous appointment by the attending
instrumentallyevaluatingswallowingfunction. pediatrician through medical history and feeding pat-
Recently,theuseofaccelerometryhasbeenunderinves- terns.Atthetimeofthestudy,allparticipantswere being
tigation as a non-invasive, low cost technique for char- fedorally.Consenttoparticipateinthestudywasacquired
acterizing swallowing [11,12]. Initial research involving fromtheparentorcaregiveroftheparticipatingchild.The
the placement of an single-axis accelerometer at the thy- datacollectionsessionoccurredduringthefeedingclinic’s
roid cartilage to measure throat vibrations has garnered VFSSassessment,andfollowedaprotocolapprovedbythe
positive results in the identification of dysphagic activ- hospital’sBoardofEthics.
ity within the adult population [13]. Nonetheless, Reddy The accelerometer (Analog Devices, A

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