Effect of bolus volume and flow time on temporospatial coordination in oropharyngeal pressure production in healthy subjects

Thin Liquid Bolus Volume Alters Pharyngeal Swallowing: Kinematic Analysis Using 3D Dynamic CT

The previous studies reported that different volumes of thick liquid had an impact on spatiotemporal characteristics and pharyngeal response of swallowing. However, the bolus flow and swallowing motion pattern were different between thick and thin liquids. The effects of thin bolus volume on pharyngeal swallowing, especially true vocal cord (TVC) closure is still unclear. This study assessed the temporal characteristics when swallowing different volumes of thin liquid to determine the mechanical adaptation using 320-row area detector computed tomography (320-ADCT) and investigated a change of swallowing physiology including laryngeal closure, particularly TVC closure. Fourteen healthy women (28-45 years) underwent 320-ADCT while swallowing of 3, 10, and 20 ml of thin liquid barium in 45° semi-reclining position. Kinematic analysis was performed for each swallow including temporal characteristic, structural movements while swallowing, and maximal cross-sectional area of the upper esophageal sphincter (UES) opening. Bolus head reached to pharynx and esophagus earlier in larger volume significantly, indicating faster bolus transport as volume increased. There were significant effects on swallowing mechanism revealing earlier TVC closure and UES opening with increasing volume. Maximum cross-sectional area of the UES opening was increased to accommodate a larger bolus. Differences in mechanical adaptation through bolus transit and motion of swallowing structures were detected across increasing volumes. These volume-dependent adaptations potentially reduce the risk of aspiration. Understanding the swallowing physiological changes as volume increased is helpful for diagnosis and treatment of dysphagia patients as well as outcomes of swallowing rehabilitation in clinical practice.

Noninvasive Evaluation of the Biomechanical Accommodations to Bolus Volume during Human Swallowing

Bolus volume is very important in the biomechanics of swallowing. By noninvasively characterizing swallow responses to volume challenges, we can gain more knowledge on swallowing and evaluate swallowing behavior easily. This study aimed to evaluate the impact of bolus volume on the biomechanical characteristics of oropharyngeal swallowing events with a noninvasive sensing system. Fifteen healthy male subjects were recruited and instructed to swallow 5, 10, and 15 ml of water. The sensing system consisted of a tongue pressure sensor sheet, bend sensor, surface electrodes, and a microphone. They were used to monitor tongue pressure, hyoid activity, surface EMG of swallowing-related muscles, and swallowing sound, respectively. In addition to the onset, the peak time and offset of the above four structures, certain characteristics, such as the duration, peak value, and interval of the structure motions, were measured during the different drinking tasks. The coordination between the hyoid movement and tongue pressure was also assessed. Although no sequence of the structural events changed with volume, most of the timings of the structural events were significantly delayed, except for certain hyoid activities. The swallowing volume did not affect the active durations of the monitored structures, the peak values, or intervals of tongue pressure and supra- and infrahyoid muscle activity, but certain hyoid kinetic phases were prolonged when a larger volume was swallowed. Additionally, sequential coordination between hyoid movement and tongue pressure was confirmed among the three volumes. These findings suggest that oropharyngeal structural movements change in response to bolus volume to facilitate safe swallowing. The noninvasive and quantitative measurements taken with the sensing system provide essential information for understanding normal oropharyngeal swallowing.

Update and review of the gerodontology prospective for 2020's: Linking the interactions of oral (hypo)-functions to health vs. systemic diseases

New lines of evidence suggest that the oral-systemic medical links and oral hypo-function are progressively transcending beyond the traditional clinical signs and symptoms of oral diseases. Research into the dysbiotic microbiome, host immune/inflammatory regulations and patho-physiologic changes and subsequent adaptations through the oral-systemic measures under ageism points to pathways leading to mastication deficiency, dysphagia, signature brain activities for (neuro)-cognition circuitries, dementia and certain cancers of the digestive system as well. Therefore, the coming era of oral health-linked systemic disorders will likely reshape the future of diagnostics in oral geriatrics, treatment modalities and professional therapies in clinical disciplines. In parallel to these highlights, a recent international symposium was jointly held by the International Association of Gerontology and Geriatrics (IAGG), Japanese Society of Gerodontology (JSG), the representative of USA and Taiwan Academy of Geriatric Dentistry (TAGD) on Oct 25th, 2019. Herein, specific notes are briefly addressed and updated for a summative prospective from this symposium and the recent literature.

Tongue pressure distribution of individual normal occlusions and exploration of related factors

Background

Tongue plays an important part in oral and maxillofacial system. Measurement of tongue pressure helps to evaluate the performance of tongue movement.

Objectives

To establish a system for measuring tongue pressure against hard palate and to preliminarily explore pressure distribution of individual normal occlusions and the relationship with dental arch form.

Methods

A total of 19 volunteers of individual normal occlusions out of 189 dental students met inclusion criteria (nine males, ten females, aged 25.53 ± 0.96 years). A force‐sensing resistor device was used to measure tongue pressure at rest and functional state (swallowing). We observed tongue pressure of four channel (anterior, posterior and lateral sides of hard palate) in sitting, supine position and swallowing. We analysed pressure differences according to gender and explored correlation relationship between tongue pressure and dental arch width and length using 3D digital maxillary image.

Results

In rest, tongue pressure against hard palate increased from front to back in both sitting and supine position, without gender differences. When swallowing saliva, the pressure at lateral sides of females was found significantly higher than that of males. Bivariate correlation analysis revealed duration of swallowing was positively correlated with BMI and weight at posterior region and positively correlated with palatal length at anterior palate. The greater the dental arch width, the smaller the pressure of swallowing in the anterior and lateral region.

Conclusion

In rest, there was consistent pressure of tongue against hard palate. The pressure increased significantly during swallowing, especially in females. Tongue pressure was related to dental arch length, width, BMI and weight.