Characteristics of the swallowing sounds recorded in the ear, nose and on trachea

Abstract

The various malfunctions and difficulties of the swallowing mechanism necessitate various diagnostic techniques to address those problems. Swallowing sounds recorded from the trachea have been suggested as a noninvasive method of swallowing assessment. However, acquiring signals from the trachea can be difficult for those with loose skin. The objective of this pilot study was to explore the viability of using the ear and nose as alternative recording locations for recording swallowing sounds. We recorded the swallowing and breathing sounds of five healthy young individuals from the ear, nose and trachea, simultaneously. We computed time-frequency features and compared them for the different locations of recording. The features included the peak and the maximum frequencies of the power spectrum density, average power at different frequency bands and the wavelet coefficients. The average power calculated over the 4 octave bands between 150 and 2,400 Hz showed a consistent trend with less than 20 dB difference for the breath sounds of all the recording locations. Thus, analyzing breath sounds recorded from the ear and nose for the purpose of aspiration detection would give similar results to those from tracheal recordings; thus, ear and nose recording may be a viable alternative when tracheal recording is not possible.

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

“…Many studies, in fact, utilize the raw transducer signal to draw their conclusions and many used the human ear in the analysis without any digital or mathematical analysis of the signal waveform’s characteristics [14]–[17], [19], [20], [22], [27], [32]–[37], [40], [48], [50], [52], [63], [76]–[79], [91]–[112]. Those studies that have conditioned the signal between acquisition and analysis generally only applied a bandpass filter in order to eliminate sources of noise at either end of the frequency spectrum [13], [28], [38], [39], [43]–[47], [49], [51], [53]–[62], [65], [68]–[73], [84]–[89]. Once again Takahashi, et al’s work [16], which was later supported by Youmans, et al [17], is cited often because their study characterized the frequency range of swallowing accelerometry signals.…”

“…Unfortunately, these studies have been unable to determine the lower bound on useful frequency components, resulting in much more variability of the placement of the lower notch. While some place it as low as 0.1 Hz in order to maintain a “pure” signal [21], [49], [51], [65], [66], [83], [86], [90], others place it as high as 30 Hz or more in order to eliminate motion artifacts and other low frequency noise [39], [42], [44], [60]–[62], [69]. Since similar bandlimits have yet to be identified for swallowing sounds, studies which use a microphone simply limit the recorded signal to either the human audible range [21], [32], [33], [37], [40], [46], [48], [67], [76]–[78], [86], [89], [95], [97]–[100], [102], [103], [110], [112]–[116] or the range of common stethoscopes used in bedside assessments [13], [22], [28], [39], [56], [69], [73], [88], [91], [92].…”

“…In the time domain, it is common to investigate the overall duration of the swallow [17], [31], [43], [45], [46], [49], [61], [63], [65], [86], [111], [122], the timing of the different phases of deglutition such as the duration of a pharyngeal delay [14], [63], [109], the magnitude of the recorded signal [16], [18], [43], [45], [47], [51], [53], [60], [61], [63], [65], [67], [70], [84], [109], and the statistical moments of the signal such as variance or kurtosis [15], [43], [49], [51], [61], [65], [84], [86], [93], [119], [122]. Many experiments also looked at various frequency domain features of the signal, such as the peak frequency, average power, or other moments, by either visual inspection of the spectrogram or via the fast Fourier transform [13], [17], [18], [31], [35], [39], [43], [44], [46], [49], [51], [53], [54], [60], [61], [63], [79], [84], [86], [94], [96], [101], [106], [112], [114], [122]. Figure 5 shows both a swallowing and a breath sound as time domain and spectrogram representations.…”

Building a three-dimensional model of the upper gastrointestinal tract for computer simulations of swallowing

“…Regarding the detection and characterization of swallowing disorders, some works [25,26] describe the analysis of the breath and swallowing sounds, at different locations such as the ear, the nose and the trachea. We believe that these techniques can be simulated in a virtual environment including trachea, oropharynx and other anatomical structures, to reproduce the acoustic manifestations of the swallowing process in the computer model, and compare against experimental recordings on healthy and dysphagic subjects.…”

Identifying the Timing of Swallowing Sounds Using Videoendoscopy Findings in Healthy Adults

“…Our results showed that swallowing sounds almost always began during the initial period of velopharyngeal closure, and almost always ended before completion of velopharyngeal closure. Several other studies have investigated the origin of swallowing sounds, with the common assumption that swallowing sounds were associated with laryngeal elevation, passing of the bolus through the upper esophageal sphincter UES and laryngeal descent [19][20][21] .…”