|Year : 2014 | Volume
| Issue : 2 | Page : 45-52
Oral and pharyngeal transit time as a factor of age, gender, and consistency of liquid bolus
J Nikhil, Rahul K Naidu, Gayathri Krishnan, R Manjula
All India Institute of Speech and Hearing, Naimisham Campus, Manasagangotri, Mysore, Karnataka, India
|Date of Web Publication||21-May-2015|
All India Institute of Speech and Hearing, Naimisham Campus, Manasagangotri, Mysore, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Introduction: The oral transit time (OTT) and pharyngeal transit time (PTT) are measures that indicate the time taken for bolus transit in oral and pharyngeal cavities, respectively. These measures vary with respect to bolus type and quantity and reflect on the efficiency of the swallow. Objectives: The study aimed to compare OTT and PTT measures for thin (water) and thick (honey) liquid bolus consistencies in 88 typical participants (44 typical adults and 44 typical geriatric persons including males and females) and 10 persons with swallowing disorders. Materials and Methods: OTT and PTT measures for liquid bolus were derived using the equipment Digital Swallowing Workstation-Swallowing Signal Laboratory (DSW-SSL) (Kay/Pentax, Lincoln, New Jersey) Model 7120. In the absence of cited standard procedures to measure OTT and PTT, the measures of OTT and PTT were specifically defined in this study based on the measures obtained from three modules/tests of the DSW-SSL: (a) Tongue array (used to measure the tongue pressure during swallow), cervical auscultation (used to measure the swallow sound), nasal cannula (used to measure the respiratory-swallow coordination). Results and Discussion: The mean group scores of OTT and PTT measures were compared across gender, age, and consistency of bolus and treated with the appropriate statistical procedure. Results revealed that: (i) PTT for honey was longer than water in typical adults and geriatric persons. (ii) There was no significant difference in OTT for honey across age groups. (iii) Atypical patterns in the morphology of tongue pressure, swallow sound and respiratory-swallow coordination during swallow were noted across age and consistency of bolus in typical and atypical population. Conclusion: The OTT and PTT measures can serve as sensitive indices to understand swallow physiology in oral and pharyngeal phase. Increase in PTT is observed for thicker liquid like honey. There are more instances of nonhomogenous patterns across typical and atypical swallows for tongue pressure, swallow sound, and respiratory-swallow coordination.
Keywords: Oral transit time, pharyngeal transit time, swallow sound and respiratory-swallow coordination, tongue pressure
|How to cite this article:|
Nikhil J, Naidu RK, Krishnan G, Manjula R. Oral and pharyngeal transit time as a factor of age, gender, and consistency of liquid bolus. J Laryngol Voice 2014;4:45-52
| Introduction|| |
Swallowing is an orderly occurring physiological process that transports saliva or ingested food from the mouth to stomach.  A good swallow function requires the fine neuromotor coordination of the central pattern generating circuitry of the brainstem and the muscles of oral, pharyngeal, laryngeal, and esophageal structures. , The four phases of a normal swallow that occur independently of one another,  but in a sequential and coordinated manner typically includes: (a) The oral preparatory phase, where food is tasted, broken down into a consistency ready for swallowing in the form of a bolus by the action of teeth and tongue (b) the oral phase, where the bolus is propelled to pharynx by the tongue (c) the pharyngeal phase, where the bolus moves through the pharynx, and (d) the esophageal stage, where the bolus moves through the esophagus and enters the stomach. ,,,,,
One of the few measures indicative of adequate swallow is the oral transit time (OTT) and pharyngeal transit time (PTT). At the end of oral preparatory phase, the food is reduced to a single ball or "bolus." The time (in seconds) from the onset of bolus movement in the mouth until the head of the bolus reaches the point where the lower rim of the mandible crosses the tongue base is defined as "OTT."  The end of an oral phase of swallowing occurs when the food comes in contact with the posterior pharyngeal wall with the initiation of swallow reflex and pharyngeal phase of the swallow. The pharyngeal phase of swallow is a rapid, complex process which is more reflexive, and less voluntary. The pharyngeal swallow has two phases; (1) early phase characterized by sealing actions of nasopharynx and upper airway tract, and oral cavity to prevent regurgitation and (2) the late phase, where the bolus moves to the opening of upper esophageal structures with the peristaltic contractions in pharyngeal constrictors. , As the bolus begins its downward movement in the pharynx, the larynx elevates and laryngeal vestibule closes for a brief period to protect the airway from penetration of bolus, which gives rise to respiratory apnea (lasting approximately 1 s), simultaneously leading to descending movement of bolus due to relaxation of the cricopharyngeal muscle, allowing the food to pass from the pharynx into the esophagus, ,,,,,,, immediately followed by resumption of expiration. This whole process gives rise to the acoustic event of swallow sound. , The time taken for the bolus head to transit from the point where the ramus of the mandible crosses the tongue base and the bolus tail to reach the cricopharyngeal region is defined as "PTT." 
Studies have suggested that the OTT and PTT depend on: (i) Consistency and volume of the bolus (ii) age and gender  in typical individuals. Using scintigraphy, it was found that OTT and PTT of typical individuals were lesser than the experimental group (individuals with Chagas's disease).  Few studies have used the biomagnetic method,  to analyze the pharyngeal clearance time along with OTT and PTT in typical individuals.  Studies have reported that delayed OTT and PTT indicate poor swallow efficiency ,,, and can serve as critical measures of swallow efficiency in persons with swallowing disorders.
Need for the study
Oral transit time and PTT are usually measured using instrumental procedures such as manometry, ,, videofluoroscopy, ,, and cineradiography, ,, where it is feasible to obtain dynamic time measures. However, such procedures are not easily accessible to all practicing speech-language pathologists due to lack of training, access, cost, and availability of the equipment. Furthermore, radiographic studies on human participants are well recognized for side effects and health hazards. However, these procedures facilitate online record of swallow physiology.
The Digital Swallowing Workstation-Swallowing Signal Laboratory (DSW-SSL) (Kay/Pentax, Lincoln, New Jersey) provides static data of swallow physiology. The procedure is noninvasive, and can be used by the speech-language pathologists without the participation of a radiologist. There are no reported studies that have used different modules of DSW-SSL simultaneously in understanding the physiology of swallow, nor to measure OTT and PTT. In this study, a combination of modules of DSW-SSL (tongue array, cervical auscultation, and nasal cannula) were used to measure and compare the OTT and PTT in typical adults and geriatric individuals and individuals with swallowing disorders for different types and volume of liquid bolus. There are no norms established for OTT and PTT using DSW-SSL in typical groups of participants. Although swallow function is said to be affected as a factor of aging in typical individuals, there are no reported studies on the typical geriatric group to the best of the knowledge of the investigators. The study uses a standard group comparison design. The study will shed light on: (i) Feasibility of use of this instrument to measure OTT and PTT in the three group of participants (ii) advantages and disadvantages of using the combined modules of DSW-SSL to measure OTT and PTT (iii) validity of the operational definition used in this study to derive OTT and PTT measures using DSW-SSL.
Aims of the study
The aims of the study were to measure and compare OTT and PTT for thin (water) and thick (honey) liquid volume of 20 ml across typical adults, typical geriatric individuals, and individuals with swallowing disorders using the combined modules of three tongue array, nasal cannula, and cervical auscultation in single swallow procedure using DSW-SSL.
| Materials and Methods|| |
Human volunteers were taken as participants for the study with their written and informed consent, as per the norms established by the Committee for Ethical Clearance for Bio Behavioral Research of the Institute where the study was conducted. A total of 98 participants were included, who were divided into three groups as follows:
Group 1: Forty-four typical adults in the age range of 18-30 years (mean age of 24 years) with equal gender distribution.
Group 2: Forty-four typical geriatric individuals in the age range of 60-80 years (mean age of 70 years) with equal gender distribution.
Group 3: Ten individuals in the age range of 28-60 years (mean age of 44 years) with swallowing disorders. [Table 1] provides the demographic details of participants in Group 3.
Criteria for selection of participants in the study
Group 1 and 2: A checklist developed by the investigators for the purpose of screening the participants were used by two speech-language pathologists to rule out the presence of speech, language, and swallowing disorders; neurological, metabolic, and systemic disorders (hypertension, and diabetes mellitus); and use of artificial dentures.
Group 3: Participants presented a primary disorder along with swallowing difficulties as shown in [Table 1].
The measures of OTT and PTT were derived (as per the procedure detailed in the analysis section) using the DSW-SSL (Model 7120; Kay/Pentax, Lincoln, New Jersey). Digital 12-bit samples were obtained with a sampling frequency of 200 Hz via a Bi-Link portable computer (Pentium Model MMX 166). The three tongue array module was used to assess the pressure exerted in the anterior, middle and posterior regions of the tongue during transfer of bolus across the tongue. In a clear swallow, a three peak waveform is seen when the three bulb tongue array module is used. The nasal cannula module is used to assess the respiratory apnea, which is indicative of protective action in the laryngeal vestibule. The period of respiratory apnea in a typical swallow is found to be <1 ms and varies with age, gender, and bolus volume.  The cervical auscultation module helps to record the "swallow sound," which is an acoustic event depicting the combined actions of movement of epiglottis,  movement of bolus through the upper esophageal sphincter  and the mechanical movement of hyo-laryngeal complex during swallow.  The combined modules of the nasal cannula, three bulb tongue array, and cervical auscultation were calibrated to the preset values defined in the modules before recording the measures of interest of every participant.
The participants were seated in a comfortable chair in up-right relaxed position and instructed to swallow the given bolus in a single attempt and avoid multiple swallow effort. The recording was carried out for individual participants for each bolus consistency (20 ml of liquid [water and honey]). The bulbs of tongue array were inflated and calibration check was done as per the prescribed norms of the equipment. The bolus was placed in the mouth of the participant followed by placing the tongue array in the mouth extending from an anterior portion of tongue till the velum. The nasal cannula was placed at opening of nares of the participant and the placement was secured by adjusting the tube around the head. The stethoscope head of the cervical auscultation module was placed on the lateral border of the thyroid notch and was secured with the velcro strap to participants' neck. Once the transducers were secured in position, and after ensuring that the participant understood the instruction, the recording was initiated as the participant swallowed the entire bolus in one single swallow. The presentation of honey and water was randomized across trials within participant and across participants to counter the order effect. A minimum of three complete swallows for each type of bolus was recorded from each participant.
Of the three recordings for each type of bolus, the best recording (defined as clear and coordinated wave morphology of at least two of the three modules without multiple swallow efforts) was selected for analysis. The initiation of tongue movement, the respiratory arrest during swallow and the swallow sound which were recorded [Figure 1] for each participant for each condition of wet swallow was analyzed. The OTT and PTT measures [Figure 1] defined as follows in this study were derived: (1) OTT is the time lapse between initiation of tongue movement (as measured in the tongue array waveform) to the beginning of respiratory apnea (as measured in the nasal cannula waveform). (2) PTT is the time lapse between initiation of respiratory apnea (as measured in the nasal cannula waveform) to the termination of swallow sound (as measured in the cervical auscultation waveform). Only 30 each (with good wave morphology) of the 44 samples of Group 1, and 44 samples of Group 2 respectively were analyzed for OTT and PTT measures. In Group 3, all the 10 samples were considered for analysis of OTT and PTT measures.
|Figure 1: The recorded sample of a typical adult for tongue pressure (using tongue array [top]); respiratory apnea (using nasal cannula to check the coordination between swallow and respiratory arrest-[middle]); and swallow sound (measured using cervical auscultation [bottom])|
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The group mean scores were tabulated and the data were treated statistically using SPSS 20.0 (Kay/Pentax, Lincoln, New Jersey) (confidence interval of 99%) for comparison of OTT and PTT values (dependent variables) across age, gender, and bolus consistency (independent variables). The test for normality of the sample was done to rule out outliers and since there were no outliers, nonparametric statistics was run. The comparison of means across the groups was carried out using nonparametric statistics. Descriptive statistics was used to establish the mean and standard deviations of OTT and PTT across groups, bolus and gender, and the means were subjected to statistical verification using Mann-Whitney U-test, Wilcoxon Signed Ranks test, and univariate ANOVA. Further, qualitative analysis of the various patterns of swallow was also done to profile different patterns that were evident across the groups of participants.
| Results|| |
Mean oral and pharyngeal transit time across gender in Group 1 and 2
[Figure 2] depicts the mean OTT and PTT for swallow of water and honey across gender in groups. The OTT and PTT values are higher in females compared to males for water and honey conditions in Group 2 and Group 1. However, no significant differences across gender were revealed for OTT-honey (F (1,29) = 1.27; P > 0.01), PTT-honey (F (1,29) = 5.78; P > 0.01), and PTT-water (F (1,29) = 3.28; P > 0.01) with no interactions between groups and gender when data were treated with univariate ANOVA. Hence, the data for males and females were combined for further analysis.
|Figure 2: Mean oral and pharyngeal transit time for swallow conditions across gender in typical Groups (1 and 2)|
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Mean oral and pharyngeal transit time for swallow of water and honey in Group 1, 2 and 3
Oral transit time could be measured for water from 13 participants only in Group 1 and 2 as a robust tongue movement for swallow was not evident in others. However, the OTT measure for honey and PTT measures for water and honey could be obtained for all participants in the 3 groups. [Figure 3] shows the OTT and PTT values for swallow of water and honey. In general, OTT is less than PTT across the groups in both conditions of wet swallow (water and honey). The OTT and PTT for both water and honey are longest in Group 3 (Clinical group) followed by Group 2 and Group 1. Statistical analysis using ANOVA revealed significant difference across Group 1 and 2 in PTT-water (F (1,29) = 11.314; P < 0.01) and honey (F (1,29) = 30.39; P < 0.01) and OTT-honey (F (1,29) = 0.09, P > 0.01).
|Figure 3: Mean oral and pharyngeal transit time measures for two conditions of wet swallow in the three groups|
Click here to view
Further, the mean PTT-honey was higher in both Group 1 and 2 compared to the PTT-water. Since the data for OTT-water and honey were few, comparison across the two conditions was not done. Wilcoxon Signed Rank test revealed statistically significant difference across bolus consistencies in Group 1 and 2 (across PTT-honey and PTT-water in Group 1 [Z = −3.32; P < 0.01] and Group 2 [Z = −3.79; P < 0.01]).
Qualitative analysis of swallow measures
The Group 3 (Clinical group) showed atypical patterns, which was attributed to the differential involvement of structures in the oral and pharyngeal regions. It was interesting though to note that the swallow pattern observed across the typical participants also showed variations in wave morphology. In a typical swallow pattern [Figure 1], the tongue movements are initiated first followed by respiratory apnea and swallow sound. This sequence was not seen in all the participants in Group 1 and 2. Few participants exhibited low amplitude tongue sweep or multiple tongue pressure peaks contrary to the expected three pressure peaks (anterior, middle, and posterior peaks) for a single swallow. A typical swallow sound is a bi-peaked wave. Few participants in Group 1 and 2 (typical group) did not show the bi-peak wave. With regard to respiratory apnea, variations such as apnea arrests or interruption due to short breath support, hazy waves indicating poor apnea control before, and after single swallows were seen in few participants in Group 1 and 2. In majority of the instances, the atypical patterns were seen in the thicker bolus consistency (honey) compared to thin bolus consistency (water). Absence of initial tongue movements (for water swallow) and swallow with poor respiratory apnea (for water and honey) were seen in adults. Low amplitude tongue pressure, incomplete respiratory apnea, weak swallow sound, and multiple swallows were evident for honey in geriatric group. In the clinical group, turbulence preceding and following the swallow sound, poor and shallow swallow sound configuration, and multiple tongue movements were observed for honey and water consistencies. [Table 2] shows the percent occurrences of atypical patterns in the groups of participants.
|Table 2: Atypical patterns observed in swallow samples of the three group of participants|
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| Discussion|| |
Literature has suggested that factors such as bolus consistencies and volume and the subjects gender and age affect the temporal relationship of the onset of specific motor events of swallow. 
Influence of aging
Overall, the geriatric individuals showed longer OTT and PTT than adults, confirming the findings in the literature which suggest that aging leads to longer OTT and PTTs. , Stronger muscular contraction in tongue and pharynx is expected in adults compared to geriatrics. Closure of oropharynx (superior constrictor) and tongue and the force applied further by larynx helps to push the bolus into the pharynx. The peristaltic action of the middle and inferior constrictors helps to move the bolus to esophagus. ,, Studies have suggested weakening of muscles in aged individuals, , leading to prolonged OTT, and pharyngeal time in geriatric population when compared to typical adults. A longer OTT and PTT thus may serve as indices for risk in the elderly group for symptoms of oropharyngeal dysphagia in the absence of any hardcore signs of structural or neurological deficits. Although the mean OTT and PTT of typical geriatric individuals were much lesser than the clinical group, it was much higher than that of adult group, suggesting a definite trend of degeneration of oral and pharyngeal skills with advancing age. There are very few studies on OTT and PTT reported in the literature. Effect of swallowing apnea duration (SAD) in swallow process with aging reported longer SAD in elderly adults than younger adults.  However, support to explain the results of prolonged PTT in this study cannot be drawn from longer SAD as the correlation of SAD and PTT are not established.
Few studies , have supported gender difference for OTT and PTT while few others , deny any influence of gender on OTT and PTT. Studies also show that males show greater strength in tongue muscles during swallowing than females,  but few other studies , report no gender difference. In this study, although the mean PTT and OTT were longer for females than males, it was not found to be statistically different.
Consistency of bolus
In this study, longer PTT was observed for thick liquid (honey) compared to thin liquid (water) in all the three groups. It can be reasoned that high viscous liquids like honey move slowly in pharynx compared to water, this notion being supported in the literature.  OTT for honey and water could not be compared as clear OTT for water was noted only in few participants across the groups, which is due to limited use of tongue for water swallow which draws good support from the qualitative observations made in [Table 2]. The results of this study do not support the observation of studies, , which found no difference in swallows between thin and thick liquid. However, it may be noted that in both of these studies the volume of the bolus was <20 ml and in this study, 20 ml of bolus was used.
On qualitative analysis of swallow
Different atypical patterns of swallow were observed across age groups, gender, and consistencies of bolus as shown in [Table 2]. It is common to observe retention of bolus for a longer time near open airway in older healthy adults, along with pooling or pocketing of bolus in the pharyngeal recesses when compared to younger adults. , This senescent change is associated with greater risk for airway penetration or aspiration. In the clinical group, different patterns of swallow were observed across consistencies of bolus which was in concurrence to the reported pathologies.
| Conclusion|| |
The present study aimed at developing and validating a noninvasive protocol for measurement of OTT and PTT and the investigation of effect of factors such as age, gender, and bolus type on these measures. Using the three modules, tongue array (for tongue pressure measurement), cervical auscultation (for swallow sound), and nasal cannula (for understanding the coordination of respiration and swallow leading to the inference of adequacy of airway protection/closure of laryngeal vestibule for safe swallow) of the DSW-SSL equipment for analysis of single swallows, it is possible to derive the OTT and PTT as a valid measure as per the operational definition stated in this study. A definite trend was observed in that the OTT and PTT were highest in clinical population followed by typical geriatric population and typical adults, leading to clear indication that OTT and PTT are sensitive measures and are susceptible to increase with aging and thus could serve as useful indices to suggest compromised oropharyngeal action in swallow in persons with dysphagia as well as typical ageing adults. Viscosity of the bolus is an important issue to be considered while evaluating swallow abilities in individuals. In all the three groups of the study, honey consistency was more difficult to swallow than water by the participants. It is possible that higher viscous fluid bolus requires greater neuromuscular compatibility. Future studies with graded viscous liquid bolus could throw more light in this direction. It is also possible that the volume of the bolus also contributes significantly. In this study, 20 ml liquid bolus was considered with the assumption that robust waves in the measure of intent of the study would be obtained. However, it needs to be investigated further to see if graded amount of bolus would help in understanding if there is an optimum level that could be prescribed in adults or geriatric individuals. The increased percentage of occurrences of atypical patterns in the qualitative observation of swallow across the typical adults and the geriatric group also supports the notion of idiosyncrasy in the swallow patterns of even the "typical" population. This emphasizes the fact that quantitative measures such as OTT and PTT could indicate a holistic trend but may not be sufficient enough to comment on individual differences in swallow patterns even in typical population and hence individual specific approach is also required to draw inferences of swallow process in individuals. It will be more useful if this is supported by behavioral observations of swallow.
| Acknowledgments|| |
The authors would like to sincerely thank the Director, All India Institute of Speech and Hearing for permitting them to use the infrastructure of the institute. The authors also wish to sincerely thank the participants and their family members for their consent and participation in the study. They also wish to place on record the help given for statistical analysis of data by Mr. C.D. Santhosh, Lecturer in Biostatistics, Department of Speech-language Pathology, All India Institute of Speech and Hearing.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]
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