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

Background: Aspiration, 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. Methods: In 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. Results: Our 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. Conclusions: Overall, 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

Prediction of larynx function using multichannel surface EMG classification

Total laryngectomy (TL) affects critical functions such as swallowing, coughing and speaking. An artificial, bioengineered larynx (ABL), operated via myoelectric signals, may improve quality of life for TL patients. To evaluate the efficacy of using surface electromyography (sEMG) as a control signal to predict instances of swallowing, coughing and speaking, sEMG was recorded from submental, intercostal and diaphragm muscles. The cohort included TL and control participants. Swallowing, coughing, speaking and movement actions were recorded, and a range of classifiers were investigated for prediction of these actions. Our algorithm achieved F1-scores of 76.0 ± 4.4 % (swallows), 93.8 ± 2.8 % (coughs) and 70.5 ± 5.4 % (speech) for controls, and 67.7 ± 4.4 % (swallows), 71.0 ± 9.1 % (coughs) and 78.0 ± 3.8 % (speech) for TLs, using a random forest (RF) classifier. 75.1 ± 6.9 % of swallows were detected within 500 ms of onset in the controls, and 63.1 ± 6.1 % in TLs. sEMG can be used to predict critical larynx movements, although a viable ABL requires improvements. Results are particularly encouraging as they encompass a TL cohort. An ABL could alleviate many challenges faced by laryngectomees. This study represents a promising step toward realising such a device

Cervical Auscultation for the Identification of Swallowing Difficulties

Swallowing difficulties, commonly referred to as dysphagia, affect thousands of Americans every year. They have a multitude of causes, but in general they are known to increase the risk of aspiration when swallowing in addition to other physiological effects. Cervical auscultation has been recently applied to detect such difficulties non-invasively and various techniques for analysis and processing of the recorded signals have been proposed. We attempted to further this research in three key areas. First, we characterized swallows with regards to a multitude of time, frequency, and time-frequency features while paying special attention to the differences between swallows from healthy adults and safe dysphagic swallows as well as safe and unsafe dysphagic swallows. Second, we attempted to utilize deep belief networks in order to classify these states automatically and without the aid of a concurrent videofluoroscopic examination. Finally, we sought to improve some of the signal processing techniques used in this field. We both implemented the DBSCAN algorithm to better segment our physiological signals as well as applied the matched complex wavelet transform to cervical auscultation data in order to improve its quality for mathematical analysis

Noninvasive Dynamic Characterization of Swallowing Kinematics and Impairments in High Resolution Cervical Auscultation via Deep Learning

Swallowing is a complex sensorimotor activity by which food and liquids are transferred from the oral cavity to the stomach. Swallowing requires the coordination between multiple subsystems which makes it subject to impairment secondary to a variety of medical or surgically related conditions. Dysphagia refers to any swallowing disorder and is common in patients with head and neck cancer and neurological conditions such as stroke. Dysphagia affects nearly 9 million adults and causes death for more than 60,000 yearly in the US. In this research, we utilize advanced signal processing techniques with sensor technology and deep learning methods to develop a noninvasive and widely available tool for the evaluation and diagnosis of swallowing problems. We investigate the use of modern spectral estimation methods in addition to convolutional recurrent neural networks to demarcate and localize the important swallowing physiological events that contribute to airway protection solely based on signals collected from non-invasive sensors attached to the anterior neck. These events include the full swallowing activity, upper esophageal sphincter opening duration and maximal opening diameter, and aspiration. We believe that combining sensor technology and state of the art deep learning architectures specialized in time series analysis, will help achieve great advances for dysphagia detection and management in terms of non-invasiveness, portability, and availability. Like never before, such advances will enable patients to get continuous feedback about their swallowing out of standard clinical care setting which will extremely facilitate their daily activities and enhance the quality of their lives

The effects of lung volume on swallowing in chronic obstructive pulmonary disease

Chronic Obstructive Pulmonary Disease (COPD), a respiratory disease that leads to reduced airflow, may result in difficulty swallowing with disease progression. The coordination between the respiratory and swallowing systems decouple and they may experience increased risk of aspiration. This study aimed to determine the effects of lung volume on swallowing in individuals with COPD compared with older healthy. Specifically, the study examined if altering lung volume at the time of the swallow changed swallowing timing, specifically pharyngeal swallow duration, and impacted the respiratory-swallow pattern in individuals with COPD. Measurement of estimated lung volume (ELV), pharyngeal swallow duration, and respiratory-swallow patterning in individuals with COPD was compared with older healthy at varying lung volume conditions. Participants completed seven 20 ml water bolus swallows by medicinal cup across 4 lung volumes: non-cued volume (NC), and in order of increasing volume, resting expiratory level (REL), tidal volume (TV), and total lung capacity (TLC) . ELV was determined using respiratory inductive plethysmography (RIP) and spirometry. Swallow timing was measured by events during the swallow with pharyngeal manometry. Individuals with COPD had lower lung volumes at the time of the swallow than older healthy individuals. A moderate to strong negative relationship between estimated lung volume at the time of the swallow and pharyngeal swallow duration was found in individuals with COPD that was not present in the healthy participants. They had a longer pharyngeal duration when swallowing at lower lung volumes. The percentage of swallows resuming on inspiration post-swallow were significantly greater in individuals with COPD than the healthy. In the COPD group, resumption of respiration in inspiration occurred significantly less often at the higher lung volumes (TLC and TV) than the lower volume condition, REL. In conclusion lower lung volumes at the time of the swallow in individuals with COPD were associated with longer pharyngeal swallow duration and increased resumption of respiration in inspiration post-swallow

An exploration of swallowing stimulation in the infant

The purpose of this study was twofold: to determine the effects of two types of non-invasive, peripheral sensory stimulation on the frequency of infant swallowing and to explore the cortical activation patterns in response to stimulation in the somatosensory and motor regions of the brain during infancy, between 2-4 months and 7-9 months of age. The two different forms of mechanical stimulation investigated include pacifier stimulation to the lips and oral cavity and vibrotactile stimulation via the external throat area to the laryngeal tissues. The study represents a prospective, repeated experimental research design. Investigators utilized an accelerometer and an inductive plethysmography system to identify swallowing events and functional near-infrared spectroscopy (NIRS), a non-invasive cortical optical-imaging technique, to cortical responses to the peripheral stimulation conditions by measuring the hemodynamic responses in cortical oral-motor and sensorimotor regions. A repeated-measures ANOVA was performed on the participants’ swallowing frequency data with and without the stimulation conditions. The results indicated a significant difference (p \u3c .001) among the three conditions (no stimulation, pacifier stimulation, and vibrotactile stimulation), with pairwise comparisons indicating that the pacifier and vibrotactile conditions significantly (p \u3c .001) increased the infants’ swallowing frequency compared to swallowing frequency without stimulation. Swallowing frequency did not differ between the pacifier and vibrotactile conditions (p \u3e .05). NIRS recordings were obtained on only a few subjects for technical reasons. NIRS pilot data changes in blood flow occurred during the pacifier and vibrotactile stimulation conditions in a few infants. Overall findings suggest that both pacifier and vibrotactile stimulation can serve to up-regulate the frequency of swallowing in normal infants. Non-nutritive pacifier stimulation may be beneficial for increasing the frequency of swallowing in infants in addition to the known benefits of aiding in sucking skills development. Vibrotactile stimulation represents an alternative or complementary intervention for increasing the frequency of swallowing in infants that may not interfere with the process of oral intake. The current study continues to collect data for normal infants and should be explored in infants with disordered swallowing, particularly in the neonatal intensive care unit

Mechanisms of Respiratory-Swallow Coordination and the Effects of Skill Training on Swallowing Rehabilitation in Parkinson’s Disease

Respiratory-swallow coordination (RSC) is critical for safe and efficient swallowing. In healthy adults, RSC is most frequently characterized by an exhale-swallow-exhale pattern initiated within the mid-lung volume range with a respiratory pause of approximately one second. This combination in RSC behaviors is thought to be most optimal for swallowing-related bolus clearance and airway protection. Deviations from these RSC behaviors are observed at disproportionately higher rates in people with Parkinson’s disease (PD) when compared to non-dysphagic, healthy adults. However, little is known about which variables influence RSC in PD, if the RSC behaviors that are most optimal for swallowing in healthy adults are also most optimal for swallowing in PD, and if respiratory-swallow training can be used to successfully rehabilitate suboptimal RSC, swallowing safety, and swallowing efficiency in PD. This dissertation document includes a series of four studies that address these important clinical research questions. Chapter 1 will begin by reviewing the current body of literature as it relates to dysphagia in PD, RSC in healthy adults and PD, respiratory-swallow training as a skill-based treatment for dysphagia rehabilitation, and motor learning considerations for respiratory-swallow skill training in PD. Chapter 2 will be used to examine the relationships among RSC with patient- and swallowing-specific factors in PD. Chapter 2 will also be used to assess the influence of RSC behaviors on measures of swallowing safety (penetration-aspiration) and swallowing efficiency (pharyngeal residue) in PD. Chapter 3 will then evaluate the effects of verbal cueing on RSC in PD as a method of determining if RSC is stimulable for rehabilitative change. Chapter 4 will explore the effects of respiratory-swallow training on swallowing safety and efficiency rehabilitation in a person with mid-stage PD and severe dysphagia within the context of a single-subject experimental design. Chapter 5 will then examine the effects of respiratory-swallow training on dysphagia and RSC rehabilitation within the context of a cohort study. Chapter 5 will also be used to compare the effects of constant versus variable practice in order to explore how principles of motor learning can be used to enhance respiratory-swallow training outcomes. This document will then conclude by synthesizing the results from Chapters 2-5 and by discussing directions for future research

Hyolaryngeal kinematics and swallow patterning in normal and disordered swallowing

Hyoid and laryngeal movements contribute to laryngeal vestibule closure and upper esophageal sphincter (UES) opening for safe swallowing. However, the extent of movement required for achieving these goals, and the interaction between hyoid and laryngeal movements during swallowing are unknown. Despite impairment in vestibule closure and UES opening, patients with dysphagia may exhibit reduced, increased or similar hyolaryngeal displacements as healthy individuals. This limits the delineation between normal and disordered swallowing. We investigated whether anatomical differences in hyolaryngeal positions and the extent of laryngeal vestibule opening at rest would better predict hyolaryngeal displacements and the extent of vestibule closure during swallowing than neck length. We then examined if hyolaryngeal maximal displacements that corrected for individual anatomical differences would show greater contrast between the swallows of patients and healthy individuals than uncorrected measures. We also investigated if the relationship between hyoid and laryngeal elevation, as well as measures of laryngeal elevation peak velocity, timing and movement patterning would differ between patients and controls swallowing more than corresponding measures of hyoid elevation. Videofluoroscopic examinations of swallowing were performed in healthy adults and patients with dysphagia. Using frame-by-frame motion analysis, measures of forward and upward hyolaryngeal displacements and velocities, and vestibule area were made during swallowing. In healthy volunteers, the extent of laryngeal vestibule opening at rest predicted the extent to which laryngeal elevation exceeded hyoid elevation for closing the space between the hyoid and larynx during swallowing. Spatially normalized measures of hyoid and laryngeal elevation magnitudes showed greater differences between normal and abnormal swallowing than raw measures. Patients with dysphagia had insufficient laryngeal elevation relative to hyoid elevation to achieve vestibule closure during swallowing. In conclusion, healthy individuals may adapt hyolaryngeal movement magnitudes according to changes in the movement targets required for vestibule closure to ensure safe swallowing. Insufficient laryngeal elevation relative to hyoid elevation may be detrimental to airway protection for swallowing in dysphagia