James L. Coyle

Differentiation of Normal and Abnormal Airway Protection during Swallowing Using the Penetration–Aspiration Scale

Abstract. Accidental loss of food or liquids into the airway while eating or drinking is perhaps the most clinically significant consequence of dysphagia. Although videofluoroscopic recording of swallowing is the current gold standard for identifying and determining remediation for aspiration, results are generally described in descriptive terms, thus limiting information and lending to errors of interpretation. We previously published an 8-point scale to quantitate selected aspects of penetration and aspiration conveying depth of airway invasion and whether or not material entering the airway is expelled (Rosenbek et al., 1996, Dysphagia 11:93–98). The present study defines the distribution of the Penetration–Aspiration Scale scores in healthy normal subjects of different genders and ages. The scale was also used with two groups of patients known to have significant dysphagia relative to stroke or head and neck cancer. Significant differences found among groups are discussed.

Cervical Auscultation Synchronized with Images from Endoscopy Swallow Evaluations

Cervical auscultation is the use of a listening device, typically a stethoscope in clinical practice, to assess swallow sounds and by some definitions airway sounds. Judgments are then made on the normality or degree of impairment of the sounds. Listeners interpret the sounds and suggest what might be happening with the swallow or causing impairment. A major criticism of cervical auscultation is that there is no evidence on what causes the sounds or whether the sounds correspond to physiologically important, health-threatening events. We sought to determine in healthy volunteers (1) if a definitive set of swallow sounds could be identified, (2) the order in which swallow sounds and physiologic events occur, and (3) if swallow sounds could be matched to the observed physiologic events. Swallow sounds were computer recorded via a Littmann stethoscope from 19 healthy volunteers (8 males, 11 females, age range = 18–73 years) during simultaneous fiberoptic laryngoscopy and respiration monitoring. Six sound components could be distinguished but none of these occurred in all swallows. There was a wide spread and a large degree of overlap of the timings of swallow sounds and physiologic events. No individual sound component was consistently associated with a physiologic event, which is a clinically significant finding. Comparisons of groups of sounds and events suggest associations between the preclick and the onset of apnea; the preclick and the start of epiglottic excursion; the click and the epiglottis returning to rest; the click and the end of the swallow apnea. There is no evidence of a causal link. The absence of a swallow sound in itself is not a definite sign of pathologic swallowing, but a repeated abnormal pattern may indicate impairment. At present there is no robust evidence that cervical auscultation of swallow sounds should be adopted in routine clinical practice. There are no data to support the inclusion of the technique into clinical guidelines or management protocols. More evaluation using imaging methods such as videofluoroscopy is required before this subjective technique is validated for clinical use by those assessing swallowing outside of a research context.

Oropharyngeal dysphagia assessment and treatment efficacy: setting the record straight (response to Campbell-Taylor)

In September 2008, an article was published in the Journal of the American Medical Directors Association criticizing current dysphagia assessment and management practices performed by speech-language pathologists in Long-Term Care (LTC) settings. In the same issue, an editorial invited dialogue on the points raised by Campbell-Taylor. We are responding to this call for dialogue. We find Campbell-Taylors interpretation of the literature to be incomplete and one-sided, leading to misleading and pessimistic conclusions. We offer a complementary perspective to balance this discussion on the 4 specific questions raised: (1) Is the use of videofluoroscopy warranted for evaluating dysphagia in the LTC population? (2) How effective are thickened liquids and other interventions for preventing aspiration and do they contribute to reduction of morbidity? (3) Can aspiration be prevented and is its prevention important? and (4) Is there sufficient evidence to justify dysphagia intervention by speech language pathologists?

The effects of increased fluid viscosity on swallowing sounds in healthy adults

BackgroundCervical auscultation (CA) is an affordable, non-invasive technique used to observe sounds occurring during swallowing. CA involves swallowing characterization via stethoscopes or microphones, while accelerometers can detect other vibratory signals. While the effects of fluid viscosity on swallowing accelerometry signals is well understood, there are still open questions about these effects on swallowing sounds. Therefore, this study investigated the influence of fluids with increasing thickness on swallowing sound characteristics.MethodWe collected swallowing sounds and swallowing accelerometry signals from 56 healthy participants. Each participant completed five water swallows, five swallows of nectar-thick apple juice, and five swallows of honey-thick apple juice. These swallows were completed in neutral head and chin-tuck head positions. After pre-processing of collected signals, a number of features in time, frequency and time-frequency domains were extracted.ResultsOur numerical analysis demonstrated that significant influence of viscosity was found in most of the features. In general, features extracted from swallows in the neutral head position were affected more than swallows from the chin-tuck position. Furthermore, most of the differences were found between water and fluids with higher viscosity. Almost no significant differences were found between swallows involving nectar-thick and honey-thick apple juices. Our results also showed that thicker fluids had higher acoustic regularity and predictability as demonstrated by the information-theoretic features, and a lower frequency content as demonstrated by features in the frequency domain.ConclusionsAccording to these results, we can conclude that viscosity of fluids should be considered in future investigations involving swallowing sounds.

A comparative analysis of swallowing accelerometry and sounds during saliva swallows

BackgroundAccelerometry (the measurement of vibrations) and auscultation (the measurement of sounds) are both non-invasive techniques that have been explored for their potential to detect abnormalities in swallowing. The differences between these techniques and the information they capture about swallowing have not previously been explored in a direct comparison.MethodsIn this study, we investigated the differences between dual-axis swallowing accelerometry and swallowing sounds by recording data from adult participants and calculating a number of time and frequency domain features. During the experiment, 55 participants (ages 18-65) were asked to complete five saliva swallows in a neutral head position. The resulting data was processed using previously designed techniques including wavelet denoising, spline filtering, and fuzzy means segmentation. The pre-processed signals were then used to calculate 9 time, frequency, and time-frequency domain features for each independent signal. Wilcoxon signed-rank and Wilcoxon rank-sum tests were utilized to compare feature values across transducers and patient demographics, respectively.ResultsIn addition to finding a number of features that varied between male and female participants, our statistical analysis determined that the majority of our chosen features were statistically significantly different across the two sensor methods and that the dependence on within-subject factors varied with the transducer type. However, a regression analysis showed that age accounted for an insignificant amount of variation in our signals.ConclusionsWe conclude that swallowing accelerometry and swallowing sounds provide different information about deglutition despite utilizing similar transduction methods. This contradicts past assumptions in the field and necessitates the development of separate analysis and processing techniques for swallowing sounds and vibrations.

Tele-Dysphagia Management: An Opportunity for Prevention, Cost-Savings and Advanced Training

Many patients survive severe stroke because of aggressive management in intensive care units. However, acquiring pneumonia during the post-onset phase significantly reduces both the quality and likelihood of survival. Aspiration pneumonia (AP), a relatively recent addition to the list of the pneumonias, is associated with dysphagia, a swallowing disorder that may cause aspiration of swallowed food or liquids mixed with bacterial pathogens common to saliva, or by aspiration of gastric contents due to emesis or gastroesophageal reflux. While it is within the purview of speech-language pathologists to provide evaluation, treatment, and management of dysphagia, the number of patients with dysphagia is growing faster than the number of qualified dysphagia clinicians. Because dysphagia consultations via telepractice are feasible and relatively accessible from a technological standpoint, they offer a promising strategy to bring the expertise of distant dysphagia experts to patients in underserved areas. Tele-dysphagia management has the potential to increase patients’ survival, enhance the expertise of primary, local clinicians, and reduce healthcare costs. Even a modest reduction in either hospital admissions for aspiration pneumonia, or in the length of stay for AP, could save the US health care system hundreds of millions of dollars each year. Wide spread tele-dysphagia management offers significant opportunities for prevention, cost-savings and advanced training, and is therefore worthy of consideration by stakeholders in the health care system and university training programs.

A comparative analysis of DBSCAN, K-means, and quadratic variation algorithms for automatic identification of swallows from swallowing accelerometry signals

BACKGROUND Cervical auscultation with high resolution sensors is currently under consideration as a method of automatically screening for specific swallowing abnormalities. To be clinically useful without human involvement, any devices based on cervical auscultation should be able to detect specified swallowing events in an automatic manner. METHODS In this paper, we comparatively analyze the density-based spatial clustering of applications with noise algorithm (DBSCAN), a k-means based algorithm, and an algorithm based on quadratic variation as methods of differentiating periods of swallowing activity from periods of time without swallows. These algorithms utilized swallowing vibration data exclusively and compared the results to a gold standard measure of swallowing duration. Data was collected from 23 subjects that were actively suffering from swallowing difficulties. RESULTS Comparing the performance of the DBSCAN algorithm with a proven segmentation algorithm that utilizes k-means clustering demonstrated that the DBSCAN algorithm had a higher sensitivity and correctly segmented more swallows. Comparing its performance with a threshold-based algorithm that utilized the quadratic variation of the signal showed that the DBSCAN algorithm offered no direct increase in performance. However, it offered several other benefits including a faster run time and more consistent performance between patients. All algorithms showed noticeable differentiation from the endpoints provided by a videofluoroscopy examination as well as reduced sensitivity. CONCLUSIONS In summary, we showed that the DBSCAN algorithm is a viable method for detecting the occurrence of a swallowing event using cervical auscultation signals, but significant work must be done to improve its performance before it can be implemented in an unsupervised manner.

Decoding human swallowing via electroencephalography: a state-of-the-art review.

Swallowing and swallowing disorders have garnered continuing interest over the past several decades. Electroencephalography (EEG) is an inexpensive and non-invasive procedure with very high temporal resolution which enables analysis of short and fast swallowing events, as well as an analysis of the organizational and behavioral aspects of cortical motor preparation, swallowing execution and swallowing regulation. EEG is a powerful technique which can be used alone or in combination with other techniques for monitoring swallowing, detection of swallowing motor imagery for diagnostic or biofeedback purposes, or to modulate and measure the effects of swallowing rehabilitation. This paper provides a review of the existing literature which has deployed EEG in the investigation of oropharyngeal swallowing, smell, taste and texture related to swallowing, cortical pre-motor activation in swallowing, and swallowing motor imagery detection. Furthermore, this paper provides a brief review of the different modalities of brain imaging techniques used to study swallowing brain activities, as well as the EEG components of interest for studies on swallowing and on swallowing motor imagery. Lastly, this paper provides directions for future swallowing investigations using EEG.

The effects of increased fluid viscosity on stationary characteristics of EEG signal in healthy adults.

Electroencephalography (EEG) systems can enable us to study cerebral activation patterns during performance of swallowing tasks and possibly infer about the nature of abnormal neurological conditions causing swallowing difficulties. While it is well known that EEG signals are non-stationary, there are still open questions regarding the stationarity of EEG during swallowing activities and how the EEG stationarity is affected by different viscosities of the fluids that are swallowed by subjects during these swallowing activities. In the present study, we investigated the EEG signal collected during swallowing tasks by collecting data from 55 healthy adults (ages 18-65). Each task involved the deliberate swallowing of boluses of fluids of different viscosities. Using time-frequency tests with surrogates, we showed that the EEG during swallowing tasks could be considered non-stationary. Furthermore, the statistical tests and linear regression showed that the parameters of fluid viscosity, sex, and different brain regions significantly influenced the index of non-stationarity values. Therefore, these parameters should be considered in future investigations which use EEG during swallowing activities.

A statistical analysis of cervical auscultation signals from adults with unsafe airway protection

BackgroundAspiration, where food or liquid is allowed to enter the larynx during a swallow, is recognized as the most clinically salient feature of oropharyngeal dysphagia. This event can lead to short-term harm via airway obstruction or more long-term effects such as pneumonia. In order to non-invasively identify this event using high resolution cervical auscultation there is a need to characterize cervical auscultation signals from subjects with dysphagia who aspirate.MethodsIn this study, we collected swallowing sound and vibration data from 76 adults (50 men, 26 women, mean age 62) who underwent a routine videofluoroscopy swallowing examination. The analysis was limited to swallows of liquid with either thin (<5 cps) or viscous (≈300 cps) consistency and was divided into those with deep laryngeal penetration or aspiration (unsafe airway protection), and those with either shallow or no laryngeal penetration (safe airway protection), using a standardized scale. After calculating a selection of time, frequency, and time-frequency features for each swallow, the safe and unsafe categories were compared using Wilcoxon rank-sum statistical tests.ResultsOur analysis found that few of our chosen features varied in magnitude between safe and unsafe swallows with thin swallows demonstrating no statistical variation. We also supported our past findings with regard to the effects of sex and the presence or absence of stroke on cervical ausculation signals, but noticed certain discrepancies with regards to bolus viscosity.ConclusionsOverall, our results support the necessity of using multiple statistical features concurrently to identify laryngeal penetration of swallowed boluses in future work with high resolution cervical auscultation.