| BackgroundSwallowing is a complex physiological process, and is one of the most important factors for surviving. It is a process to transport food from the mouth to the stomach safely and effectively. The whole processes of swallowing can be divided into four physiologic stages:oral preparation, oral, pharyngeal, and esophageal stage. As the growth of the age, function of swallowing declines gradually. Dysphagia is a common disease in the elderly, it occurs in 8-10% of persons over the age of 50 years old, however most of dysphagia patients do not consult a physician for this problem. Dysphagia can be caused by a variety of diseases, such as the nervous system diseases, myopathies, and structural disorders after the treatment of head and neck cancers with radiotherapy, chemotherapy or surgery. As is known to all, mealtime is the main mode of the old social and interpersonal communication, the disorder of swallowing can have a negative impact on their physical condition, mental health, and quality of life. In the long run, dysphagia can cause malnutrition, dehydration, aspiration pneumonia. The pharyngeal phase is the third phase during swallowing. Food will turn into bolus with suitable viscosity after it has been chewed thoroughly. When the bolus is propelled from the oral cavity to the pharyngeal cavity, the pharyngeal stage of the swallow will be activated. The pharyngeal phase is the most complicated one among the four phases. It includes some events that: the elevation of the hyoid bone, the rotation of the epiglottis, the closure of the glottis and the opening of the upper esophageal sphincter. Food properties such as consistency, volume and taste can produce a great influence on the measurement of parameters associated with pharyngeal phase. For example, the amplitude and the duration of the hyoid motion are significantly different when subjects swallow different volume or consistency. Highly viscous food can delay the start time of pharyngeal stage, whereas sour foods can make the trigger time earlier. The normal pharyngeal functions in the process of swallowing require finely tuned coordination between sensory perception and a lot of muscles. If this coordination is destroyed, pharyngeal swallowing disorder may be induced. Many abnormalities of swallowing in the pharyngeal phase are attributed to reduced range of hyoid movement. Reduced hyoid movement can cause an increased risk of airway invasion and pharyngeal residue. Hyoid motion can be decomposed into vertical and horizontal movement during swallowing. The vertical displacement of the hyoid bone contributes primarily to epiglottic and laryngeal closure, while the anterior displacement contributes primarily to opening of the UES and ensures safe passage of food into the esophagus. Dynamic videofluoroscopic swallow study is one of the most important technologies in the evaluation of swallowing. It can evaluate the duration of hyoid motion, the amplitude of the hyoid movement, the rotation of the epiglottis and the upper esophageal sphincter opening objectively. It also evaluates the amount of stasis in the laryngopharynx that occurred during swallowing. It has been reported that there are no significant gender differences in any temporal and dimensional parameters. Previous studies have shown that males and females perform similarly in pharyngeal transit time, pharyngeal constriction ratio and maximum opening of the upper esophageal sphincter. The age-related effects on various parameters of oral stage and pharyngeal stage have been reported. And the motion of the hyoid bone has been reported to be affected by the age, including the duration and the amplitude of hyoid movement. It is also speculated that the UES opening in healthy subject decreases as the growth of the age. Foreign experts reported the average onset of forward movement of the hyoid was closer to UES reference time significantly than was the onset of upward movement, and concluded that hyoid forward movement was related to pharyngeal stage of swallowing, especially the opening of the upper esophageal sphincter. In this study, we define the kinematics of the hyoid motion and the upper esophageal sphincter opening in subjects without dysphagia to explore the influence of aging on the pharyngeal stage of the swallowing in this study. The measurement of parameters associated with pharyngeal phase of swallowing is divided into two types of analysis: temporal and spatial. The correlation between hyoid displacement and UES opening during swallowing is investigated.ObjectiveThe main purpose of this study was to investigate the influence of age on hyoid bone motion and the UES opening in healthy subjects, and to investigate the correlation between hyoid displacement and UES opening during swallowing.MethodsDynamic videofluoroscopic swallow studies were performed on 100 healthy adult volunteers after they had signed the informed consent in Department of Radiology of Navy General Hospital. The study protocol was approved by the Hospital Ethics Committee. There were 56 males and 44 females, The age of the volunteers ranged from 20 to 74 years with an average of 43.5±12.3 years. All the volunteers underwent an indirect laryngoscopy, Repetitive saliva swallowing test and Water swallow test to rule out the influencing diseases of swallowing function. The volunteers were divided into 3 groups:the young group (<45years), with an average age of 34.2±7.3 years; middle-aged group (45 to 65 years), the average age was 54.1±5.8; old group (>65 years), with an average age of 71.3≈4.1. There were 40 subjects in young and middle-aged groups respectively and 20 subjects in old group.Shimadzu digital gastrointestinal machine, Horita time recording and digital video recorder were used to record the swallowing process of the volunteers. The video was transcribed in the upright position with the lateral and frontal anterior-posterior views of the pharynx. Measures were made for 60% barium sulfate mixture swallows of 20 ml. The subjects were asked to hold the barium sulfate mixture in the oral cavity before the order to swallow. The progress of oral and pharyngeal stages was recorded. We used Avidemux 2.5 software and Image J measurement software to analyze the recording of the swallowing process frame-by-frame and measured the time lag of the hyoid motion, maximum hyoid anterior displacement, and the maximum hyoid displacement of each subject. The contraction of base of tongue, rotation of the epiglottis and the opening of the upper esophageal sphincter during swallowing of the volunteers were normal. We found no bucking and aspiration, no obvious pharyngeal barium residue in all subjects.Duration of hyoid motion:Avidemux 2.5 software was used for image analysis, and the slowing down of the videofluoroscopy recordings. The duration of the hyoid bone motion from rest position to the maximum displacement position was measured first. Then the average duration of hyoid bone remaining in the highest position and the duration of hyoid bone returns to its resting position from maximum displacement position were evaluated. In the end, the total time for the hyoid motion was calculated.Maximum hyoid anterior displacement (HAmax) and maximum hyoid superior displacement (HSmax):Avidemux 2.5 software was used to select two images from the swallowing recordings which represented the resting position and maximum displacement position of the hyoid bone respectively. In our study, the angle of the line between the anterior-inferior corner of cervical vertebra 4 (C4) and the anterior-inferior corner of cervical vertebra 2 (C2) was used to rotate the image to 90° through the Image J software, as a result of this, the picture frames were rotated to a true vertical of 90°. The point on the anterior-inferior corner of C4 was used as an anchor point, and the coin with a diameter of 1.9cm placed under the chin of the subjects was served as the reference ruler. The X and Y coordinates of each point was provided by Image J software. The formula for the calculation of the hyoid anterior displacement:(x2-x1)-(Ox2-Ox1); and the formula for the hyoid vertical displacement:(y2-y1)-(Oy2-Oy1), where x1 and y1 were the starting coordinates of the anterior-inferior border of hyoid bone and x2 and y2 were the maximum displacement coordinates. Ox1 and Oy1 were the coordinates of the anchor point in the rest frame, and Ox2 and Oy2 were the coordinates of the anchor point in the maximum hyoid displacement frame.Maximum hyoid displacement (Hmax):Hmax was defined by measuring the shortest distance between the position of anterior-superior border of hyoid one at rest and the position of anterior-superior border of the hyoid at its maximum displacement during the swallowing. In the frame corresponding to resting position and maximum displacement position of hyoid bone, the anterior-superior border of hyoid was outlined and an angle of 90° was drawn up along the anterior border of the C2-C4 and anterior-inferior corner of the C4. Then this segment was cut and pasted from the first image to the second image, the anterior-superior border of the hyoid and two sides of the right angle from the two frames were aligned completely in the second image and the distance between points on the hyoid anterior-superior border was calculated using Image J software and the distance was the Hmax.Maximum upper esophageal sphincter opening (UESmax):UESmax was defined as the narrowest part of the tract between C4 and C6 with the tract maximally opened in the process of swallowing.Statistical methods:SPSS version 16.0 was used for statistical analysis, and statistical significance was indicated when P value was less than 0.05. Time and spatial variances were divided into 3 groups according to age. The measurement data were then compared across age groups using a one-way analysis of variance. Bivariate correlation analysis was used to analyze the correlation coefficients.ResultThe average duration of the hyoid excursion from its resting position to the maximal displacement point was 0.83±0.29 s, and the interval prolonged with the increase of age, and that showed significant differences among the 3 groups (P< 0.05). The mean time of hyoid bone keeping in the maximal excursion was 0.18± 0.05 s, it decreased with the increase of age, the difference was statistically significant between the young group and the old group and between the middle-aged group and the old group(P<0.05). The duration of hyoid bone from maximum displacement position to the resting position and the total time of the hyoid bone were 1.23±0.48 s and 2.24±0.55 s respectively, and there was no statistically significant difference in T3 and T among the 3 groups(P>0.05).The maximal hyoid superior displacement was 1.44±0.58cm, and there was no obvious difference among the 3 groups(P>0.05). The maximum hyoid anterior displacement was 1.05±0.25cm, it decreased with the increase of the age, and significant differences were found between the young group and the middle-aged group and between the young group and the old group (P<0.05). The hyoid total displacement during the swallowing was 1.83 ± 0.49cm, it became smaller with the increase of age, but there was no remarkable difference among the 3 groups(P> 0.05). The maximal UES opening was 0.95±0.14cm, it decreased with the increase of age, and significant differences were found between the young group and the old group (P<0.05).The correlation coefficient between maximal hyoid superior displacement and UES opening was 0.07, and there was no correlation between them; The correlation coefficient between maximal hyoid anterior displacement and UES opening was 0.66, and the anterior hyoid displacement had significant relation to UES opening (P< 0.05).ConclusionThis two-dimensional kinematic swallowing motion analyses showed that the hyoid bone movement parameters and the UES opening in healthy subjects changed with age. The correlation between anterior hyoid displacement and UES opening was significant(P< 0.05). The measurement of parameters associated with pharyngeal phase during swallowing could be used for the diagnosis of dysphagia. |
