Glenn Berall

Investigating the stationarity of paediatric aspiration signals

An aspiration signal is the time-varying anterior-posterior acceleration measured infero-anterior to the thyroid notch when foreign material enters the airway during inspiration. The hypothesis of weak stationarity is tested on aspiration signals by the reverse arrangements test. Results indicate that aspiration signals cannot be uniformly regarded as weakly stationary. Forty-five percent of the examined signals violated the stationarity hypothesis. For these signals, time-varying variance and spectral density structure are identified as major sources of nonstationarity. Stationarity test results generally corroborate qualitative clinical descriptions of aspiration. However, stationarity analysis indicates that aspiration signals are highly heterogenous, a finding which poses significant challenges to the automatic detection of aspirations by accelerometry.

A Practical Approach to Classifying and Managing Feeding Difficulties

Many young children are thought by their parents to eat poorly. Although the majority of these children are mildly affected, a small percentage have a serious feeding disorder. Nevertheless, even mildly affected children whose anxious parents adopt inappropriate feeding practices may experience consequences. Therefore, pediatricians must take all parental concerns seriously and offer appropriate guidance. This requires a workable classification of feeding problems and a systematic approach. The classification and approach we describe incorporate more recent considerations by specialists, both medical and psychological. In our model, children are categorized under the 3 principal eating behaviors that concern parents: limited appetite, selective intake, and fear of feeding. Each category includes a range from normal (misperceived) to severe (behavioral and organic). The feeding styles of caregivers (responsive, controlling, indulgent, and neglectful) are also incorporated. The objective is to allow the physician to efficiently sort out the wide variety of conditions, categorize them for therapy, and where necessary refer to specialists in the field.

Quantitative classification of pediatric swallowing through accelerometry

BackgroundDysphagia 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.MethodsIn 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.ResultsUsing 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.ConclusionsOur 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.

Testing the stationarity and normality of paediatric aspiration signals

Ninety-four aspiration signals were collected with a single-axis accelerometer placed infero-anterior to the thyroid notch from 23 children with Dysphagia. It was found that only 62% of aspiration signals can be considered stationary over short finite time windows. Further, 96% of aspiration signals violated normality to varying degrees. Nonstationarity was attributed to time-varying variance structure while departure from normality was linked to leptokurtic (more peaked than a normal distribution) amplitude distributions. Conventional assumptions of stationarity and normality do not simultaneously hold true for aspiration signals. Implications for automatic detection are mentioned.

A Radial Basis Function Classifier for Pediatric Aspiration Detection

Silent aspiration presents a serious health issue for children with dysphagia. To date, there is no satisfactory means of detecting aspiration in the home or community. In an effort to design a practical device that could offer reliability, non-invasiveness, portability, and easy usability, radial basis functions based on cervical accelerometry signals were investigated. Vibration signals associated with safe swallows and aspirations, both identified via videofluoroscopy, were collected from over 100 children with neurologically-based dysphagia using a single-axis accelerometer. Three time-domain discriminatory mathematical features were extracted from the accelerometry signals. An exhaustive set of all possible combinations of the features was investigated in the design of radial basis function classifiers. The feature pairing of dispersion ratio and normality achieved an accuracy of 81.03plusmn5.78%, a false negative rate of 9.06plusmn4.84%, and a false positive rate of 9.91plusmn5.03% for aspiration detection. The proposed classifier can be easily implemented in a hand-held device