Normal Swallowing Acoustics Across Age, Gender, Bolus Viscosity, and Bolus Volume

Cervical Auscultation for Detecting Oropharyngeal Aspiration in Paediatric and Adult Populations: A Systematic Review and Meta-Analysis

BACKGROUND

Cervical auscultation (CA) involves listening to swallowing and respiratory sounds and/or vibrations to detect oropharyngeal aspiration (OPA). CA has shown promising diagnostic test accuracy when used with the clinical swallowing examination and is gaining popularity in clinical practise. There has not been a review to date analysing the accuracy of CA in paediatric and adult populations with meta-analyses.

OBJECTIVES

To determine the accuracy of CA in detecting OPA in paediatric and adult populations, when compared to instrumental assessments.

SEARCH METHODS

Databases searched included MEDLINE, PubMed, Embase, CINAHL, AustHealth, Cochrane and Web of Science. The search was restricted between 01 October 2012 and 01 October 2022.

SELECTION CRITERIA

Inclusion criteria included (a) all clinical populations of all ages, (b) who have had an instrumental assessment and (c) CA. All study types were included.

DATA COLLECTION AND ANALYSIS

Studies were reviewed independently by two authors. The methodological quality of the studies was analysed using the QUADAS-2.

MAIN RESULTS

Ten studies met the inclusion criteria for this review and meta-analyses. The pooled diagnostic performance of CA in detecting OPA was 0.91 for sensitivity and 0.79 for specificity. The area under the curve summary receiver operating curve (sROC) was estimated to be 0.86, thereby indicating good discrimination of OPA. Most studies scored high for risk of bias in at least one domain in the QUADAS-2, likely attributed to a lack of high-quality prospectively designed studies.

CONCLUSIONS

There are promising diagnostic test accuracies for the use of CA in detection of OPA. Future research could include using CA in specific clinical populations and settings, and identifying standardised criteria for CA.

Acoustic Analysis of Swallowing of an Experimental Meal of Three Food Textures: A Comparative Aging Study

Swallowing disorders in the elderly represent a public health problem, their detections are a medico-economic issue. The acoustic analysis of swallowing has the advantages of being non-invasive with no radiation, compared to videofluoroscopy or fiberoptic swallowing assessments. Acoustic analysis of swallowing has been tested in many studies but only on small food boluses. The aim of this study was to compare the acoustic swallowing parameters of two groups of healthy subjects, before and after 70 years old, during the intake of a series of 3 food textures. A laryngophone was used to record the pharyngeal phase of swallowing. The experimental meal was composed of 100 ml of mashed potatoes, 100 ml of water, and 100 ml of yogurt. Group 1 (50-70 years old) comprised 21 subjects and group 2 (over 70 years old) 23 subjects. Acoustic parameters analyzed were the number of swallows, average duration of swallowing, average duration of inter-swallowing, meal duration, and the average frequency of swallowing per minute. These parameters for groups 1 and 2 were compared. The average duration of inter-swallowing and the meal duration were significantly higher in the older group (p < 0.001), with a mean duration of inter-swallowing that was 2.4 s longer than the younger group. The average swallowing frequency per minute was higher in the younger group (11.3 vs 7.9; p < 0.001). This study demonstrated that acoustic analysis of an experimental meal of three food textures generated usable data on swallowing. In the over 70 age group, there was a decrease in swallowing frequency, indicating a slowdown in food intake. A reduced swallowing frequency could become a criteria to assess presbyphagia.

Pilot Study: Magnetic Motion Analysis for Swallowing Detection Using MEMS Cantilever Actuators

The swallowing process involves complex muscle coordination mechanisms. When alterations in such mechanisms are produced by neurological conditions or diseases, a swallowing disorder known as dysphagia occurs. The instrumental evaluation of dysphagia is currently performed by invasive and experience-dependent techniques. Otherwise, non-invasive magnetic methods have proven to be suitable for various biomedical applications and might also be applicable for an objective swallowing assessment. In this pilot study, we performed a novel approach for deglutition evaluation based on active magnetic motion sensing with permanent magnet cantilever actuators. During the intake of liquids with different consistency, we recorded magnetic signals of relative movements between a stationary sensor and a body-worn actuator on the cricoid cartilage. Our results indicate the detection capability of swallowing-related movements in terms of a characteristic pattern. Consequently, the proposed technique offers the potential for dysphagia screening and biofeedback-based therapies.

Effects of carbonated beverages on sustained swallowing behavior changes in older inpatients

Sensory stimulation, including stimulation with carbonated liquids, has been known to influence swallowing activity. The aim of this study is to determine the effect of sustained changes in the swallowing behavior of hospitalized patients without dysphagia using the cervical auscultatory recordings of swallowing sounds. The study participants were hospitalized older adults without dysphagia. The participants were asked to initially swallow water and then a carbonated beverage. The sustained effects of the carbonated beverage in relation to swallowing movements were evaluated by measuring the swallowing sounds at the following time periods: (1) immediately and (2) at 1 to 9 minutes with intervals of 2 minutes after swallowing the carbonated beverage. The swallowing sounds before and after swallowing the same volume of water were also measured and compared on a different day. Analysis was performed to calculate the time from a sound signal to the beginning of the swallowing sound. Significant shortening of the swallowing sound time of the late pharyngeal phase was observed up to 7 minutes after swallowing the carbonated beverage, except during the 3 minutes after swallowing. Shortening of the whole swallowing sound time was observed only immediately after swallowing the carbonated beverage. Regarding the shortening of the acoustic signal in the late pharyngeal period, the effect of cerebral excitability changes due to carbonic acid stimulation was considered.

Alterations in deglutition in children with congenital Zika virus syndrome

PURPOSE

To characterize swallowing in children with congenital Zika virus syndrome in comparison to typical children.

METHODS

This cross-sectional study enrolled 45 children diagnosed with congenital Zika virus syndrome and 45 others with typical development. Swallowing was evaluated through clinical feeding evaluations Protocolo de Avaliação Clínica da Disfagia Pediátrica and using acoustic swallowing parameters (Doppler sonar).

RESULTS

The mean age of children with congenital Zika virus syndrome was 26.69 ± 4.46 months and the mean head circumference was 29.20 ± 1.98 cm. Moderate/severe oropharyngeal dysphagia was found in 32(71.1%) of the children with congenital Zika virus syndrome. Significant differences were found between the groups on clinical evaluation: Children with congenital Zika virus syndrome presented insufficient lip closure 42(93.3%) and altered tonus of the tongue 35(77.8%) and cheeks 34(75.6%). In the children in the comparison group, only 6(13.3%) presented insufficient lip closure and 1(2.2%) had inadequate tongue posture. Changes during swallowing with liquid and spoonable food were not observed in the comparison group. When liquid/food was offered, affected children presented difficulties in sipping movements 14(77.8%) and lip/spoon contact 35(75%). The presence of residual food in the oral cavity after swallowing 38(86.4%) and clinical signs indicative of laryngotracheal penetration/aspiration, such as coughing, gagging and/or labored breathing, were also notable. No differences were found between the groups with regard to the acoustic parameters evaluated instrumentally.

CONCLUSION

Children with congenital Zika virus syndrome present alterations in the oral phase of swallowing, as well as clinical signs indicative of pharyngeal phase impairment.

Using an Automated Speech Recognition Approach to Differentiate Between Normal and Aspirating Swallowing Sounds Recorded from Digital Cervical Auscultation in Children

Use of machine learning to accurately detect aspirating swallowing sounds in children is an evolving field. Previously reported classifiers for the detection of aspirating swallowing sounds in children have reported sensitivities between 79 and 89%. This study aimed to investigate the accuracy of using an automatic speaker recognition approach to differentiate between normal and aspirating swallowing sounds recorded from digital cervical auscultation in children. We analysed 106 normal swallows from 23 healthy children (median 13 months; 52.1% male) and 18 aspirating swallows from 18 children (median 10.5 months; 61.1% male) who underwent concurrent videofluoroscopic swallow studies with digital cervical auscultation. All swallowing sounds were on thin fluids. A support vector machine classifier with a polynomial kernel was trained on feature vectors that comprised the mean and standard deviation of spectral subband centroids extracted from each swallowing sound in the training set. The trained support vector machine was then used to classify swallowing sounds in the test set. We found high accuracy in the differentiation of aspirating and normal swallowing sounds with 98% overall accuracy. Sensitivity for the detection of aspiration and normal swallowing sounds were 89% and 100%, respectively. There were consistent differences in time, power spectral density and spectral subband centroid features between aspirating and normal swallowing sounds in children. This study provides preliminary research evidence that aspirating and normal swallowing sounds in children can be differentiated accurately using machine learning techniques.

Directed Functional Coordination Analysis of Swallowing Muscles in Healthy and Dysphagic Subjects by Surface Electromyography

Swallowing is a complex sequence of highly regulated and coordinated skeletal and smooth muscle activity. Previous studies have attempted to determine the temporal relationship between the muscles to establish the activation sequence pattern, assessing functional muscle coordination with cross-correlation or coherence, which is seriously impaired by volume conduction. In the present work, we used conditional Granger causality from surface electromyography signals to analyse the directed functional coordination between different swallowing muscles in both healthy and dysphagic subjects ingesting saliva, water, and yoghurt boluses. In healthy individuals, both bilateral and ipsilateral muscles showed higher coupling strength than contralateral muscles. We also found a dominant downward direction in ipsilateral supra and infrahyoid muscles. In dysphagic subjects, we found a significantly higher right-to-left infrahyoid, right ipsilateral infra-to-suprahyoid, and left ipsilateral supra-to-infrahyoid interactions, in addition to significant differences in the left ipsilateral muscles between bolus types. Our results suggest that the functional coordination analysis of swallowing muscles contains relevant information on the swallowing process and possible dysfunctions associated with dysphagia, indicating that it could potentially be used to assess the progress of the disease or the effectiveness of rehabilitation therapies.

Dysphagia management: Does structured training improve the validity and reliability of cervical auscultation?

Purpose: Cervical auscultation (CA) uses a stethoscope or microphone to complement the clinical swallow examination by interpreting swallowing sounds and swallow-respiratory coordination. This study investigated the effects of structured CA training on CA-rating agreement with Flexible Endoscopic Evaluation of Swallowing (FEES) and CA rater reliability.Method: Thirty-nine speech-language pathologists participated in a structured CA training course at Gothenburg University. They rated nine swallow-respiratory sound recordings which were simultaneously recorded during FEES. Swallow sounds were rated six weeks prior to the CA-workshop using two binary yes/no questions, (1) Safe, (2) Dysphagia, and a third Dysphagia Severity rating. Swallow sounds were rated again (re-randomised) one month post CA-workshop.Result: Agreement with FEES (validity) improved significantly (p < 0.05) pre-post training for the Safe and Dysphagia questions, with post training sensitivities >90% and specificities at 76% and 85% respectively. Dysphagia severity rating improved non-significantly. Intra-rater reliability improved significantly with kappa statistics >0.90 post training. Improvements for inter-rater reliability were noted, though non-significant.Conclusion: Results demonstrate that with structured training, the validity of CA (to detect a Safe/Dysphagic swallow) significantly improves, as does intra-rater reliability. This is congruent with literature identifying the positive effects of structured training improving instrumental dysphagia assessment.

Effects of different viscous liquids and solid foods on swallowing speeds and sounds among healthy adults

BACKGROUND

Digital cervical auscultation (CA) has been proposed since the 1950s for screening aspiration among patients with dysphagia. Researchers have investigated the 'external' effects such as bolus viscosity, volume, and head and neck positions. However, the influences of standardized liquid viscosity and food texture on swallowing sounds have not been fully understood due to lacking uniform standardization of bolus preparation. Furthermore, a paucity of the literature recommends proper viscous liquids and foods to start swallowing training or monitor the swallowing progress during the continuum of disease based on acoustic signals.

AIMS

To investigate the effects of eight-level liquids and foods on swallowing sound features based on the International Dysphagia Diet Standardisation Initiative (IDDSI).

METHODS & PROCEDURES

We collected swallowing sounds from 30 healthy participants ranging in age from 19 to 60 years and who were self-reporting no history of swallowing disorders. Each participant swallowed liquids and foods regarding different consistency or texture with their head-trunk in a neutral position.

OUTCOMES & RESULTS

Features of swallowing acoustic signals and the IDDSI flow test as well as food test confirmed the level 3 moderately thick (MO3) was more suitable to categorize into liquids and the level 4 extremely thick (EX4) was more corresponded to the properties of food bolus. We found significant differences in duration of acoustic signals across different liquids and foods except between swallowing level 0 thin liquid and level 1 slightly thick liquid, as well as EX4 and level 5 minced and moist. Our results also demonstrated liquid viscosity significantly impacted the peak intensity of swallowing sounds.

CONCLUSIONS & IMPLICATIONS

As an initial exploration of digital CA across eight levels of different liquids and foods according to the IDDSI, we established the baseline findings for future comparisons with other study populations or other various consistent liquids/foods. Although both MO3 and EX4 can be considered as liquid or food boluses with high thickness, MO3 might be suitable as the 'start liquid' for patients with dysphagia; however, the decision still needs to be confirmed by the healthcare provider based on patients' safety and the area of deficit. We also concluded there are influences of varied fluid consistency and food texture on swallowing sounds. Furthermore, future investigations should explore whether changing viscosity levels could either continuously or discretely disturb the swallowing acoustic signals.

WHAT THIS PAPER ADDS

What is already known on the subject Previous studies have found that the 'external' effects such as bolus viscosity, volume, and head and neck positions. Due to lacking uniform standardization of bolus preparation, there is limited information about the influences of standardized liquid viscosity and food texture on swallowing sounds. What this paper adds to the existing knowledge As an initial exploration, we utilized digital CA with a large sample of viscous liquids and different textures of foods based on the IDDSI to investigate the swallowing sounds. What are the potential or actual clinical implications of this work? This study confirms that the effects of various fluid consistency and food texture on swallowing acoustic signals. However, the findings of this study support the need for further research relating to changing viscosity could either continuously or discretely disturb the swallowing acoustic signals.

Automatic Detection and Analysis of Swallowing Sounds in Healthy Subjects and in Patients with Pharyngolaryngeal Cancer

Assessment of swallowing function is often invasive or involves irradiation. Analysis of swallowing sounds is a noninvasive method for assessment of swallowing but is not used in daily medical practice. Dysphagia could be the first symptom that occurs in head and neck cancer. This study evaluated a method for the automatic detection and analysis of swallowing sounds in healthy subjects and in patients with pharyngolaryngeal cancer. A smartphone application, developed for automatic detection and analysis of swallowing sounds was developed and tested in 12 healthy volunteers and in 26 patients with pharyngolaryngeal cancer. Swallowing sounds were recorded with a laryngophone during a standardized meal (100 mL mashed potatoes, 100 mL water, and 100 mL yogurt). Swallowing number and duration were noted; the results were compared to a standard swallowing sound analysis using the software AUDACITY^®. There were no statistically significant differences in swallowing number or duration between the two analysis methods for the three types of foods in healthy volunteers and only for water in patients. In healthy volunteers, the results of our automatic analysis were comparable with those obtained with the standard analysis. However, a better discrimination of swallowing sounds is necessary for the algorithm to obtain reliable results with thicker food in patients with head and neck cancer.

Evaluation of swallowing ability using swallowing sounds in maxillectomy patients

Maxillectomy for oral tumours often results in debilitating oral hypofunction, which markedly decreases quality of life. Dysphagia, in particular, is one of the most serious problems following maxillectomy. This study used swallowing sounds as a simple evaluation method to evaluate swallowing ability in maxillectomy patients with and without their obturator prosthesis placed. Twenty-seven maxillectomy patients (15 men, 12 women; mean age 66.0 ± 12.1 years) and 30 healthy controls (14 men, 16 women; mean age 44.9 ± 21.3 years) were recruited for this study. Participants were asked to swallow 4 mL of water, and swallowing sounds were recorded using a throat microphone. Duration of the acoustic signal and duration of peak intensity (DPI) were measured. Duration of peak intensity was significantly longer in maxillectomy patients without their obturator than with it (P < .05) and was significantly longer in maxillectomy patients without their obturator than in healthy controls (P < .025 after Bonferroni correction). With the obturator placed, DPI was significantly longer in maxillectomy patients who had undergone soft palate resection than in those who had not (P < .05). These results suggest swallowing ability in maxillectomy patients could be improved by wearing an obturator prosthesis, particularly during the oral stage. However, it is difficult to improve the oral stage of swallowing in patients who have undergone soft palate resection even with obturator placement.

Accuracy of cervical auscultation in detecting the presence of material in the airway

Several studies have investigated the accuracy of cervical auscultation (CA). However, both the sensitivities and the specificities of CA in detecting dysphagic conditions varied widely among these studies. These wide variations of the accuracy of CA might be caused by differences of the targeted sounds, such as the expiratory sound (ES) and/or swallowing sound (SS). Forty-six dysphagic patients were served as subjects. Patients who had unoccluded tracheostoma and patients who could not follow the instructions were excluded. During the videofluorographic swallowing study (VFSS), the subjects swallowed 3 ml of yogurt containing barium sulfate. The VFSS images were recorded with acoustic signals including both the swallowing and respiratory sounds detected by our method. Classification of the VFSS images was decided by consensus of the three dentists using a penetration-aspiration scale (PAS). Recorded VFSS images were classified into the following 2 groups based on PAS: "no or minimum risk group": PAS1-2; and "possible risk group": PAS3-8. As a result of the classification of VFSS findings, 30 samples were evaluated as no or minimum risk group and 16 as possible risk group. Twelve observers including 10 dentists other than 3 dentists who evaluated VFSS images and 2 speech pathologists auditorily diagnosed "negative" and "positive." Sensitivity, specificity, and intra-rater reliability was calculated for the 3 types of acoustic samples. The sensitivity of the intra-rater reliability was 60.3% for ES, 76.6% for SS, and 89.9% for ES + SS. The sensitivity of intra-rater reliability of ES + SS samples was significantly higher than that of ES (p < .01) and SS (p < .05). The sensitivity of intra-rater reliability of SS was significantly higher than that of ES (p < .01). The specificity of the intra-rater reliability was 53.7% for ES, 50.3% for SS, and 44.5% for ES + SS. ES + SS might be most useful for detecting the presence of material in the airway.

Análise acústica do tempo de deglutição através do Sonar Doppler

RESUMO Objetivo: comparar o parâmetro acústico de tempo da deglutição orofaríngea nos adultos e idosos, nas diferentes consistências e volumes, através do Sonar Doppler. Métodos: a pesquisa foi realizada em duas etapas. Na primeira foi aplicado o Protocolo de Triagem de Risco para Deglutição. Na segunda os indivíduos foram submetidos à avaliação da deglutição com o Sonar Doppler. Os indivíduos receberam as seguintes consistências alimentares durante a avaliação - deglutição seca (saliva), líquida, néctar, mel e pudim, nos volumes de 5 ml, 10 ml e deglutição livre. O parâmetro acústico analisado neste estudo foi o Tempo acústico da deglutição (T). Resultados: dados objetivos e mensuráveis foram obtidos; a diferença do tempo de deglutição entre adultos e idosos em relação à consistência e o volume foi, na maioria, significante. Conclusão: verificou-se que há modificação do tempo da deglutição, tanto em relação à consistência quanto a volume do bolo alimentar, quando comparados idosos e adultos.

Evaluation of Swallowing Sound Using a Throat Microphone with an AE Sensor in Patients Wearing Palatal Augmentation Prosthesis

An increase in the population of dysphagia patients due to an aging population has led to increased attention on examination methods based on swallowing sound as simple methods of screening aspiration. However, an issue with the conventional method of cervical auscultation is that its accuracy varies based on the examiner. Previous studies examined the use of throat microphones and acceleration sensors to examine the acoustic characteristics of swallowing sound. Nevertheless, extant studies to date did not reach a level of clinical application. This study focused on using a throat microphone that is conventionally used to measure swallowing sound and an AE sensor to measurement a high-frequency range equal to and exceeding 20 kHz (upper limit 2 MHz). The study involved measuring the sounds of swallowing water of healthy subjects and patients wearing palatal augmentation prosthesis who had done surgical operation to treat head and neck cancer with the objective of using swallowing sound for screening aspiration. Acoustic characteristics of measured swallowing sound were analyzed using probability distributions using Quantile-Quantile (Q-Q) plots and spectral analysis based on wavelet transform. The findings indicated that with respect to patients with PAP, the duration time of the swallowing sound and the Q-Q plot departure rate were both significantly higher when compared with those in healthy subjects. The analysis based on wavelet transform indicated that the AE sensor allowed measurements of waveforms at a higher frequency range when compared to those in the case of the throat microphone. Additionally, an increased frequency of higher-frequency signals was associated with patients with PAP when compared to healthy subjects. The results revealed that it is possible to measure waveforms in the high-frequency range by using the AE sensor. The findings suggested the validity of analysis of the swallowing sound based on probability distributions using the Q-Q plot to evaluate the swallowing sound.

Characterization of Swallowing Sound: Preliminary Investigation of Normal Subjects

OBJECTIVE

The purpose of this study was to characterize the swallowing sound and identify the process of sound generation during swallowing in young healthy adults.

METHODS

Thirty-three healthy volunteers were enrolled and allocated into three experimental groups. In experiment 1, a microphone was attached to one of eight cervical sites in 20 subjects, participants swallowed 5 ml water, and the sound waveform was recorded. In experiment 2, 10 subjects swallowed either 0, 5, 10, or 15 ml water during audio recording. In addition, participants consumed the 5 ml bolus in two different cervical postures. In experiment 3, the sound waveform and videofluoroscopy were simultaneously recorded while the three participants consumed 5 ml iopamidol solution. The duration and peak intensity ratio of the waveform were analyzed in all experimental groups.

RESULTS

The acoustic analysis of the waveforms and videofluoroscopy suggested that the swallowing sound could be divided into three periods, each associated with a stage of the swallowing movement: the oral phase comprising posterior tongue and hyoid bone movement; the pharyngeal phase comprising larynx movement, hyoid bone elevation, epiglottis closure, and passage of the bolus through the esophagus orifice; and the repositioning phase comprising the return of the hyoid bone and larynx to their resting positions, and reopening of the epiglottis.

CONCLUSION

Acoustic analysis of swallowing sounds and videofluoroscopy suggests that the swallowing sound could be divided into three periods associated with each process of the swallowing movement: the oral phase comprising the posterior movement of the tongue and hyoid bone; the pharyngeal phase comprising the laryngeal movement, hyoid bone elevation, epiglottis closure, and the bolus passage to the esophagus orifice; and the repositioning phase comprising the repositioning of the hyoid bone and larynx, and reopening of the epiglottis.

Acoustic and Perceptual Profiles of Swallowing Sounds in Children: Normative Data for 4-36 Months from a Cross-Sectional Study Cohort

Limited data on cervical auscultation (CA) sounds during the transitional feeding period of 4-36 months in healthy children exist. This study examined the acoustic and perceptual parameters of swallowing sounds in children aged 4-36 months over a range of food and fluid consistencies. Using CA, swallowing sounds were recorded from a microphone as children ate or drank. Acoustic parameters of duration, peak frequency and peak intensity were determined. Perceptual parameters of swallowing/breath sounds heard pre-, during and post-swallow were rated ('present', 'absent', 'cannot be determined') for each texture. 74 children (35 males; mean age = 17.1 months [SD 10.0]) demonstrated mean swallow durations of <1 s. Increasing age correlated to reduced peak frequency on puree (r = -0.48, 95 % CI -0.66, -0.24). Age correlated to peak amplitude when swallowing puree (r = 0.27, 95 % CI 0.02, 0.49), chewable solids (r = 0.31, 95 % CI 0.02, 0.56) and thin fluids (r = 0.48, 95 % CI 0.27, 0.64). The bolus transit sound was present in all swallows. A majority of children had normal breathing sounds and coordinated swallows. A swallow duration of <1 s and the presence of a quick bolus transit sound with normal breathing sounds were found in healthy children. The normative data reported in this study provide a platform for future comparison to abnormal swallowing sounds in children.

Aspirating and Nonaspirating Swallow Sounds in Children

Background:

Cervical auscultation (CA) may be used to complement feeding/swallowing evaluations when assessing for aspiration. There are no published pediatric studies that compare the properties of sounds between aspirating and nonaspirating swallows.

Aim:

To establish acoustic and perceptual profiles of aspirating and nonaspirating swallow sounds and determine if a difference exists between these 2 swallowing types.

Methods:

Aspiration sound clips were obtained from recordings using CA simultaneously undertaken with videofluoroscopic swallow study. Aspiration was determined using the Penetration-Aspiration Scale. The presence of perceptual swallow/breath parameters was rated by 2 speech pathologists who were blinded to the type of swallow. Acoustic data between groups were compared using Mann Whitney U-tests, while perceptual differences were determined by a test of 2 proportions. Combinations of perceptual parameters of 50 swallows (27 aspiration, 23 no aspiration) from 47 children (57% male) were statistically analyzed using area under a receiver operating characteristic (aROC), sensitivity, specificity, and positive and negative predictive values to determine predictors of aspirating swallows.

Results:

The combination of post-swallow presence of wet breathing and wheeze and absence of GRS and normal breathing was the best predictor of aspiration (aROC = 0.82, 95% CI, 0.70-0.94). There were no significant differences between these 2 swallow types for peak frequency, duration, and peak amplitude.

Conclusion:

Our pilot study has shown that certain characteristics of swallow obtained using CA may be useful in the prediction of aspiration. However, further research comparing the acoustic swallowing sound profiles of normal children to children with dysphagia (who are aspirating) on a larger scale is required.

Anatomical Directional Dissimilarities in Tri-axial Swallowing Accelerometry Signals

Swallowing accelerometry is a noninvasive approach currently under consideration as an instrumental screening test for swallowing difficulties, with most current studies focusing on the swallowing vibrations in the anterior-posterior (A-P) and superior-inferior (S-I) directions. However, the displacement of the hyolaryngeal structure during the act of swallowing in patients with dysphagia involves declination of the medial-lateral (M-L), which suggests that the swallowing vibrations in the M-L direction have the ability to reveal additional details about the swallowing function. With this motivation, we performed a broad comparison of the swallowing vibrations in all three anatomical directions. Tri-axial swallowing accelerometry signals were concurrently collected from 72 dysphagic patients undergoing videofluoroscopic evaluation of swallowing (mean age: 63.94 ± 12.58 years period). Participants swallowed one or more thickened liquids with different consistencies including thin-thick liquids, nectar-thick liquids, and pudding-thick liquids with either a comfortable self-selected volume from a cup or a controlled volume by the examiner from a 5-ml spoon. Swallows were grouped based on the viscosity of swallows and the participant's stroke history. Then, a comprehensive set of features was extracted in multiple signal domains from 881 swallows. The results highlighted inter-axis dissimilarities among tri-axial swallowing vibrations including the extent of variability in the amplitude of signals, the degree of predictability of signals, and the extent of disordered behavior of signals in time-frequency domain. First, the upward movement of the hyolaryngeal structure, representing the S-I signals, were actually more variable in amplitude and showed less predictable behavior than the sideways and forward movements, representing the A-P and M-L signals, during swallowing. Second, the S-I signals, which represent the upward movement of the hyolaryngeal structure, behaved more disordered in the time-frequency domain than the sideways movement, M-L signals, in all groups of study except for the pudding swallows in the stroke group. Third, considering the viscosity and the participant's pathology, thin liquid swallows in the nonstroke group presented the most directional differences among all groups of study. In summary, despite some directional dissimilarities, M-L axis accelerometry characteristics are similar to those of the two other axes. This indicates that M-L axis characteristics, which cannot be observed in videofluoroscopic images, can be adequately derived from the A-P and S-I axes.

Oropharyngeal dysphagia: manifestations and diagnosis

Swallowing disorders (dysphagia) have been recognized by the WHO as a medical disability associated with increased morbidity, mortality and costs of care. With increasing survival rates and ageing of the population, swallowing disorders and their role in causing pulmonary and nutritional pathologies are becoming exceedingly important. Over the past two decades, the study of oropharyngeal dysphagia has been approached from various disciplines with considerable progress in understanding its pathophysiology. This Review describes the most frequent manifestations of oropharyngeal dysphagia and the clinical as well as instrumental techniques that are available to diagnose patients with dysphagia. However, the clinical value of these diagnostic tests and their sensitivity to predict outcomes is limited. Despite considerable clinical research efforts, conventional diagnostic methods for oropharyngeal dysphagia have limited proven accuracy in predicting aspiration and respiratory disease. We contend that incorporation of measurable objective assessments into clinical diagnosis is needed and might be key in developing novel therapeutic strategies.

New Swallowing Evaluation Using Piezoelectricity in Normal Individuals

This study aimed to elucidate the relationship between the piezoelectric waveform latency, hyoid bone movement, surface electromyogram (sEMG), and the pharyngeal transit time (PTT) during swallowing. Forty-one healthy subjects were divided into three age groups: younger (20-39 years, n = 8), middle-aged (40-59 years, n = 9), and older (60-79 years, n = 24). Motion analysis of the hyoid bone using videofluorography (VF), waveform analysis of the front neck using piezoelectric films, and sEMG of the suprahyoid muscle group were performed simultaneously. Latencies of the three movement phases were defined as upward (VFS1), forward (VFS2), and returning to starting position (VFS3). The three phases of the piezoelectric waveform-from wave initiation of the negative wave to the start of the second deep negative wave; from the start of the second deep negative wave to the start of the last positive wave (SLPW); and from the SLPW to the end of the last positive wave-were defined as PS1, PS2, and PS3, respectively. VFS1-3 and PS1-3 were significantly correlated. VFS1 and PS1 latencies were significantly longer with thick liquid than with thin liquid. VFS2, PS1, and PS2 latencies were longer in the older group than in the other two groups. The start of PS1 was nearly equal to those of sEMG and VFS1. Bolus arrival time in the valleculae was statistically equal to the end of the PS1 with both thin and thick liquids. To establish the swallowing screening using Piezoelectric film, further investigation is necessary in the dysphagia patients.

Dysphagia Screening: Contributions of Cervical Auscultation Signals and Modern Signal-Processing Techniques

Cervical auscultation is the recording of sounds and vibrations caused by the human body from the throat during swallowing. While traditionally done by a trained clinician with a stethoscope, much work has been put towards developing more sensitive and clinically useful methods to characterize the data obtained with this technique. The eventual goal of the field is to improve the effectiveness of screening algorithms designed to predict the risk that swallowing disorders pose to individual patients' health and safety. This paper provides an overview of these signal processing techniques and summarizes recent advances made with digital transducers in hopes of organizing the highly varied research on cervical auscultation. It investigates where on the body these transducers are placed in order to record a signal as well as the collection of analog and digital filtering techniques used to further improve the signal quality. It also presents the wide array of methods and features used to characterize these signals, ranging from simply counting the number of swallows that occur over a period of time to calculating various descriptive features in the time, frequency, and phase space domains. Finally, this paper presents the algorithms that have been used to classify this data into 'normal' and 'abnormal' categories. Both linear as well as non-linear techniques are presented in this regard.

Cervical auscultation as an adjunct to the clinical swallow examination: a comparison with fibre-optic endoscopic evaluation of swallowing

This prospective, single-blinded study investigated the validity and reliability of cervical auscultation (CA) under two conditions; (1) CA-only, using isolated swallow-sound clips, and (2) CSE + CA, using extra clinical swallow examination (CSE) information such as patient case history, oromotor assessment, and the same swallow-sound clips as condition one. The two CA conditions were compared against a fibre-optic endoscopic evaluation of swallowing (FEES) reference test. Each CA condition consisted of 18 swallows samples compiled from 12 adult patients consecutively referred to the FEES clinic. Patients' swallow sounds were simultaneously recorded during FEES via a Littmann E3200 electronic stethoscope. These 18 swallow samples were sent to 13 experienced dysphagia clinicians recruited from the UK and Australia who were blinded to the FEES results. Samples were rated in terms of (1) if dysphagic, (2) if the patient was safe on consistency trialled, and (3) dysphagia severity. Sensitivity measures ranged from 83-95%, specificity measures from 50-92% across the conditions. Intra-rater agreement ranged from 69-97% total agreement. Inter-rater reliability for dysphagia severity showed substantial agreement (rs = 0.68 and 0.74). Results show good rater reliability for CA-trained speech-language pathologists. Sensitivity and specificity for both CA conditions in this study are comparable to and often better than other well-established CSE components.

Acoustic study of pharyngeal swallowing as a function of the volume and consistency of the bolus

Cervical auscultation is a noninvasive technique for the exploration of swallowing and has been used since the 1960s. The aim of our study was to describe how the volume and consistency of the bolus affect swallowing acoustic sound characteristics in healthy subjects. Twenty-three subjects aged from 20 to 59 years were included (13 women and 10 men). A microphone mounted on a stethoscope chest piece, positioned on the skin on the right side in front of the posteroinferior border of the cricoid cartilage, was used; it was connected to a computer for acoustic recordings. Each subject swallowed 2-, 5-, and 10-ml aliquots of water, yogurt, and mashed potato. Each bolus was administered once, with a period of at least 30 s between each swallow. For each recorded sound, the total duration of the sound and the duration of each sound component (SC) (SC1, SC2, and SC3) and interval (IT1 and IT2) between the SCs were measured. For all records, the average duration of acoustic measures was calculated. Differences according to the volume and the consistency of the swallowed bolus were assessed using Student's t test for paired data. We calculated the percentage of recordings that included each SC. We also compared results between men and women using Student's t test. We successfully interpreted 540 of the 621 (87 %) records. The results indicated that the average total duration of the sound, and especially the average duration of SC2, increased with increasing volume and was greater for mashed potato than for the boluses of other consistencies. SC2 was present in all of the records.

Contribuição da ausculta cervical para a avaliação clínica das disfagia orofaríngeas

Para auxiliar na avaliação funcional da deglutição, a maior parte dos fonoaudiólogos utiliza recursos instrumentais como a ausculta cervical. Em vista disso, o objetivo deste estudo foi verificar na literatura a contribuição da ausculta cervical para a avaliação clínica das disfagias. Para tanto, foram revisados periódicos nacionais e internacionais, indexados nas bases de dados Springer, Lilacs, Bireme, Medline e Scielo, entre os anos de 1992 e 2011. A partir da análise dos estudos foi possível verificar que a ausculta cervical vem se modernizando com a evolução tecnológica, possibilitando a realização de estudos quantitativos dos sons da deglutição; que ainda há evidências pouco claras das correspondências entre os componentes sonoros da deglutição e os eventos fisiológicos da fase faríngea; que não foram evidenciadas diferenças nos sons da deglutição entre crianças e adultos; e que alguns estudos apresentaram concordância entre a ausculta cervical e a avaliação videofluoroscópica da deglutição, e outros ainda apresentaram correlação positiva entre estas duas avaliações. Assim, considerando-se que a videofluoroscopia da deglutição em nosso país ainda é um exame de difícil acesso, com custo relativamente alto, acredita-se que a ausculta cervical constitui um importante recurso para o diagnóstico e acompanhamento clínico em casos de disfagia orofaríngea.

Fast Fourier transform analysis of sounds made while swallowing various foods

The cervical auscultation method was applied to investigate sounds generated while swallowing various foods with unique physical properties, including liquid (water), semiliquid (yogurt), and solid (konjac jelly). To study the differences among swallowing sounds for various foods, fast Fourier transform (FFT) analysis was applied to signals that were attributed to the flow of a food bolus, which is a swallowable soft mass of chewed food. An FFT program was developed that enabled the calculation of a spectrum for a specified region of time domain swallowing sound signals. The intensity of spectra in the frequency range between 400 and 1000 Hz significantly differed: liquid > semiliquid > solid. The FFT spectrum in this range was suggested to represent the frequency characteristics of the swallowing sounds of various foods.