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Larynx motion associated with swallowing during radiation therapy.

PURPOSE: A basis is presented for predicting the reduction in radiation dose to the larynx attributable to swallowing during radiation therapy treatment. METHODS AND MATERIALS: Laryngeal movement associated with swallowing can occur during radiation therapy even when the patient's head is immobilized. Data on the extent and timing of laryngeal motions and the frequency of swallowing were used to predict the effect such motion would have on accuracy of radiation dose to the larynx. RESULTS: In a nontracheostomized adult the larynx elevates approximately 2 cm during a swallow and moves anteriorly less than 1 cm. The normal frequency of swallowing in the supine position is once every 1-2 min. During therapy, the likelihood of a swallow occurring during an irradiation interval depended on the duration of the interval. For irradiation intervals less than 2 min long the ratio of number of swallows to number of intervals was 0.27. For irradiation intervals between 2-3 min long the ratio was 1.76. Based on conservative estimates of radiation field dimensions, larynx motion, and incidence of swallowing, the reduction in radiation dose attributable to swallowing during treatment would be approximately 0.5%. CONCLUSION: With small fields the total dose is only decreased by 0.5% with swallowing, so the change in the total dose is insignificant.

Deglutition↗

Submental surface electromyographic measurement and pharyngeal pressures during normal and effortful swallowing.

OBJECTIVE: To evaluate the influence of 2 swallowing maneuvers on anterior suprahyoid surface electromyographic measurement and pharyngeal manometric pressure. DESIGN: Correlational analysis of biomechanic measures of swallowing. SETTING: Research laboratory in a community hospital. PARTICIPANTS: A consecutive volunteer sample of 22 healthy subjects (mean, 29.7y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Peak amplitude of submental surface electromyographic and pharyngeal manometric pressure at 3 locations. RESULTS: Effortful swallow generated greater pharyngeal pressure than normal swallow at the 2 proximal pharyngeal sensors (sensor 1: P=.017; sensor 2: P=.009) and lower pressure at the distal sensor (upper esophageal sphincter) (P<.001). Pressure in the upper pharynx was lower than that in the lower pharynx (P=.027). Effortful swallow generated greater surface electromyographic amplitudes than normal swallowing (P<.001). A statistically significant but weak negative correlation was identified between surface electromyographic and mid-pharyngeal pressure for normal swallowing condition (r=-.21, P<.01). For the effortful swallowing condition, statistically significant but weak negative correlations were identified between surface electromyographic and pressure measurements at all sensors (sensor 1: r=-.16, P=.02; sensor 2: r=-.30, P<.01; sensor 3: r=-.18, P<.01). CONCLUSIONS: There is a significant change in both suprahyoid surface electromyographic and pharyngeal pressures during effortful swallow compared with normal swallow.

Adult↗

Oral behavior from food intake until terminal swallow.

We analyzed oral behavior from food intake until terminal swallow for mastication and swallowing under a freely eating condition with a natural food. Measurements, including movement of the mandible and tongue, the size of the gape, different sequences involved in the oral aspect of the swallowing action, and bolus size and movement were carried out in five "freely eating subjects" using videofluorography. During food intake, the tongue moved forwards and backwards to introduce food into the mouth, to compress the food against the hard palate, and to transport food to the occlusal surface of the molar teeth. Most of the food was swallowed in the first swallow, and any residual food was aggregated by the tongue into a bolus and then swallowed in the last swallow. These findings suggest that 1) tongue manipulation plays an important role in recognizing and evaluating the volume of bite taken, 2) the intra-oral compression of food has a role in the recognition of food texture, 3) stage I transport is closely bound to the texture recognition process, 4) humans need at least two swallows, even with one bite of food, when ingesting food freely, and 5) the duration time of the oral stage of swallowing may depend on the bolus volume and be longer for smaller volumes unlike those measured under the command swallow.

Adult↗

Effects of bilateral lingual and inferior alveolar nerve anesthesia effects on masticatory function and early swallowing.

OBJECTIVE: To determine whether bilateral lingual and inferior alveolar nerve anesthesia affects the onset of swallowing including masticatory function. STUDY DESIGN: Twenty young male volunteers were asked to chew and swallow corned beef and then a mixture of corned beef and liquid in their usual manner before and after local anesthesia. The oral and pharyngeal swallowing was investigated using videofluoroscopic examination in a lateral plane. Eight objective indicators including oral containment time, swallowing threshold, and pharynx-to-swallow interval were measured. RESULTS: Oral containment time and total sequence duration, total number of chews, and total number of swallows for the 2 test foods varied significantly between those before and after anesthesia. Individual pharynx-to-swallow intervals varied with both foods without remarkable increases or decreases in the swallow duration and cricopharyngeal opening time. CONCLUSION: Bilateral lingual and inferior alveolar nerve anesthesia may affect early swallowing; changes in the onset of swallowing varied among the participants.

Adult↗

Abnormalities in the coordination of respiration and swallow in preterm infants with bronchopulmonary dysplasia.

Individual rhythms of suck, swallow, and respiration are disrupted in preterm infants with bronchopulmonary dysplasia (BPD). Integration of respiration into suck-swallow efforts is critical for establishing coordinated suckle feeding. This study quantitatively assessed the coordination of respiration and swallow in infants with and without BPD. Thirty-four preterm infants of 26 to 33 weeks' gestational age were included: 14 participants with BPD (eight males, six females)and 20 comparison participants without BDP (10 males, 10 females). Participants were studied at postmenstrual age 32 to 40 weeks and postnatal age 2 to 12 weeks using digital recordings of pharyngeal pressure, nasal thermistor flow, and thoraco-abdominal plethysmography. The coefficients of variation (COV; standard deviation/mean) of the swallow-breath (SW-BR) and breath-breath (BR-BR) intervals during swallow runs, the percentage of 'apneic swallows' (runs of >or=3 swallows without interposed breaths), and phase relationships of respiration and swallow were used to quantify rhythmic coordination and integration of respiration into feeding episodes. Apneic swallows were significantly increased after 35 weeks in infants with BPD (mean 13.4% [SE 2.4]) compared with non-BDP infants (6.7% [SE 1.8]; p<0.05), as were SW-BR phase relationships involving apnea. The BPD cohort also had significantly higher SW-BR COV and BR-BR COV than non-BPD infants, indicating less rhythmic coordination of swallowing and respiration during feeding. Results emphasize the need for frequent rests and closer monitoring when feeding infants with respiratory compromise. Quantitative assessment of the underlying rhythms involved in feeding may be predictive of longer-term feeding and neurological problems.

Analysis of Variance↗

Oropharyngeal swallow in younger and older women: videofluoroscopic analysis.

Much of the initial research on normal swallowing has been conducted in young men. Recently, there has been increasing interest in determining whether there are differences between the sexes in swallowing function and in the effects of aging on swallowing in both sexes. This investigation examined the swallowing ability of 8 healthy young women between the ages of 21 and 29 and 8 healthy older women between the ages of 80 and 93 during two swallows each of 1 ml and 10 ml liquid boluses. Videofluoroscopic studies of these swallows were reviewed in slow motion and real time to confirm the absence of swallowing disorders. Kinematic analysis of each swallow was completed. Data on range of motion of pharyngeal structures and coordination characteristics of the oropharyngeal swallow were taken from this kinematic analysis. Position of the larynx at rest and length of neck were compared between the two groups. Data from this study were compared with previously published data on younger and older men. Interestingly, the range of motion of the older women was often greater than that of the young women. Only tongue base movement diminished significantly with age in women. Volume effects observed in duration and extent of movement during the 1 ml and 10 ml swallows were similar to those in earlier studies. Older women also exhibited an increased range of motion relative to the old men. This increase may indicate a compensation for aging effects not seen in older men.

Adult↗

Swallow respiratory patterns and aging: presbyphagia or dysphagia?

BACKGROUND: Assessment referrals are increasing for unexpected dysphagia, particularly for older people. It is unclear if this is due to more impaired swallows or healthy age-related changes. Swallow respiration coordination prevents aspiration, and may deteriorate with age. Nonpathological features of the swallow in healthy aging and the factors that influence an individual's ability to eat and drink safely need greater understanding. Some changes might predispose an older person to dysphagic complications in the event of an insult such as a stroke. We investigated the effects of healthy aging on resting and swallow respiratory patterns. METHODS: Fifty healthy volunteers (aged 20-78 years) were recruited to have swallow respiration patterns recorded on a computer. Bolus volume and consistency variations were studied: 5 and 20 ml of water and 5 ml of yogurt. RESULTS: Measurable swallows significantly decreased with age for water boluses. Swallow apnea increased with age (5 ml of water r = 0.433, p = .002; 5 ml of yogurt r = 0.367, p = .023). Independent of age were: breathing out (occurred after 98% of boluses); multiple swallowing (occurred with all bolus types); post-swallow respiration reset pattern (more irregular after yogurt, Wilcoxon signed rank Z = -2.236, p = .025); and resting respiration. CONCLUSIONS: Subtle changes occur in swallow respiration coordination with age. These changes may be compensatory protective mechanisms rather than the result of decreased muscle mobility or reaction times, and not indicative of impairment. Misattributing healthy age-related changes to impairment affects patient care and the use of healthcare resources.

Adult↗

Swallowing in sleep and wakefulness in adult cats.

Clinical evidence indicates that swallowing, a vital function, may be impaired in sleep. To address this issue, we elicited swallows in awake and sleeping adult cats by injecting water through a nasopharyngeal tube. Our results indicate that swallowing occurs not only in non-rapid eye movement (NREM) sleep, but also in rapid eye movement (REM) sleep. In NREM sleep, the injections often caused arousal followed by swallowing, but, in the majority of cases, swallowing occurred in NREM sleep before arousal. These swallows in NREM sleep were entirely comparable to swallows in wakefulness. In contrast, the injections in REM sleep were less likely to cause arousal, and the swallows occurred as hypotonic events. Furthermore, apneas were sometimes elicited by the injections in REM sleep, and there was repetitive swallowing upon arousal. These results suggest that the hypotonic swallows of REM sleep were ineffective.

Animals↗

Swallowing disorders in head and neck cancer patients treated with radiotherapy and adjuvant chemotherapy.

The nature of swallowing problems was examined in nine patients treated primarily with external-beam radiation and adjuvant chemotherapy for newly diagnosed tumors of the head and neck. All subjects underwent videofluorographic examination of their swallowing. Three analyses were completed, including the following: observations of motility disorders, residue, and aspiration; temporal analyses; and biomechanical analyses. Oropharyngeal swallow efficiency was calculated for the first swallow of each bolus. Swallow motility disorders were observed in both the oral and pharyngeal stages. Seven of the nine patients demonstrated reduced posterior tongue base movement toward the posterior pharyngeal wall and reduced laryngeal elevation during the swallow. Oropharyngeal swallow efficiency measures were significantly lower in the nine irradiated patients than in age-matched normal subjects. Between patients and normal subjects, significant differences were found in the measures of timing and distance of pharyngeal structural movements during the swallow, as well as in the measures of coordination during the swallow. Although treatment of head and neck cancer with external-beam radiation is designed to provide cancer cure and preserve organ functioning, oral and pharyngeal motility for swallow can become compromised if external-beam radiation treatment is provided to either the larynx or tongue base regions.

Adult↗

Cortical representation of swallowing in normal adults: functional implications.

OBJECTIVE: Dysphagia of neurogenic or postsurgical origin presents management and therapeutic challenges to the otolaryngologist. Improvements in management and therapeutic approaches may be facilitated by understanding how the central nervous system controls swallowing. The purpose of this investigation was to utilize functional magnetic resonance imaging to determine patterns of cortical activity during swallowing in normal, healthy adult subjects. STUDY DESIGN: Functional magnetic resonance imaging (fMRI) was performed on eight healthy adult subjects using conventional BOLD (blood oxygenation level dependent) techniques. METHODS: Subjects performed three different swallowing tasks including dry and bolus swallows, and performed a control finger movement task. Statistical maps of cortical activation were generated using a cross-correlation analysis. One-way and two-way ANOVA statistical analyses were performed to compare activated areas among the different tasks and to determine the effects of task sequence. RESULTS: Activation during the three swallowing tasks occurred in the primary motor cortex, primary somatosensory cortex, and other cortical and subcortical sites. Cortical representation of swallowing and finger movement followed somatotopic maps. Differential distribution of cortical activation was observed for the different swallowing tasks. CONCLUSIONS: Activation of the primary motor and somatosensory cortices, as well as other sensory-motor areas, occurs with swallowing in normal adults. Differential distribution of cortical activity with different swallowing tasks suggests differential functional organization for different swallowing tasks. Understanding these mechanisms may facilitate improved management and therapeutic intervention for neurogenic and postsurgical dysphagia.

Adult↗

Swallowing dysfunction in 101 patients with nephropathic cystinosis: benefit of long-term cysteamine therapy.

Nephropathic cystinosis is a rare, autosomal recessive lysosomal storage disorder caused by mutations in the CTNS gene that codes for a cystine transporter in the lysosomal membrane. Affected patients store 50-100 times the normal amounts of cystine in their cells, and suffer renal tubular and glomerular disease, growth retardation, photophobia, and other systemic complications, including a myopathy and swallowing dysfunction. Using videofluoroscopy and ultrasound examinations, we assessed the swallowing function of 101 patients with nephropathic cystinosis on their most recent admission to the National Institutes of Health Clinical Center between 1987 and 2004. These patients ranged in age from 6 to 45 years; more than half had significant complaints of swallowing difficulty. On examination of barium swallow, the oral, pharyngeal, and esophageal phases of swallowing were abnormal in 24%, 51%, and 73% of patients, respectively. The frequency of dysfunction increased with age for each phase of swallowing. Both the Swallowing Severity Score (a measure of dysfunction on barium swallow) and the Oral Muscle Composite Score (a reflection of vocal strength, oral-facial movement, and tongue and lip function) increased (that is, worsened) with the number of years that a patient was not receiving treatment with cysteamine, the cystine-depleting agent of choice in cystinosis. The severity scores decreased with the number of years on cysteamine therapy. The Swallowing Severity Score varied directly with the severity of muscle disease, but was not correlated with the presence or absence of the 57-kb CTNS deletion that commonly occurs in nephropathic cystinosis patients. We conclude that swallowing dysfunction in cystinosis presents a risk of fatal aspiration, correlates with the presence of muscle atrophy, and, based on cross-sectional data, increases in frequency with age and number of years without cysteamine treatment. Cystine-depleting therapy with cysteamine should be considered the treatment of choice for both pre- and posttransplant cystinosis patients.

Adolescent↗

Swallowing and voice effects of Lee Silverman Voice Treatment (LSVT): a pilot study.

OBJECTIVE: To define the effects of Lee Silverman Voice Treatment (LSVT on swallowing and voice in eight patients with idiopathic Parkinson's disease. METHODS: Each patient received a modified barium swallow (MBS) in addition to voice recording before and after 1 month of LSVT. Swallowing motility disorders were defined and temporal measures of the swallow were completed from the MBS. Voice evaluation included measures of vocal intensity, fundamental frequency, and the patient's perception of speech change. RESULTS: before LSVT, the most prevalent swallowing motility disorders were oral phase problems including reduced tongue control and strength. Reduced tongue base retraction resulting in residue in the vallecula was the most common disorder in the pharyngeal stage of the swallow. Oral transit time (OTT) and pharyngeal transit time (PTT) were prolonged. After LSVT, there was an overall 51% reduction in the number of swallowing motility disorders. Some temporal measures of swallowing were also significantly reduced as was the approximate amount of oral residue after 3 ml and 5 ml liquid swallows. Voice changes after LSVT included a significant increase in vocal intensity during sustained vowel phonation as well as during reading. CONCLUSIONS: LSVT seemingly improved neuromuscular control of the entire upper aerodigestive tract, improving oral tongue and tongue base function during the oral and pharyngeal phases of swallowing as well as improving vocal intensity.

Aged↗

Nitric oxide modulates spontaneous swallowing behavior in near-term ovine fetus.

Human and ovine fetuses demonstrate an enhanced rate of swallowing, an activity critical for amniotic fluid regulation. Fetal swallowing may be modulated by both systemic and central factors. Nitric oxide (NO) is a central neuromodulator that has been localized to brain regions regulating thirst and swallowing. We sought to determine if NO contributes to the regulation of spontaneous ovine fetal swallowing. Six time-dated pregnant ewes with singleton fetuses (129 +/- 1 day) were chronically prepared with fetal vascular and lateral ventricle catheters and electrocorticogram (ECoG) and esophageal electromyogram electrodes. After a 2-h control period, fetuses were given lateral ventricle injection of NO synthase inhibitor nitro-L-arginine methyl ester (L-NAME) and monitored for 2 h. NO precursor L-arginine was then injected into the lateral ventricle, and fetuses were monitored for a final 2 h. All fetuses received an additional control study of fetal swallowing before and after lateral ventricle injection of artificial cerebrospinal fluid (aCSF). Data were analyzed with repeated-measures ANOVA and paired t-test (P < 0.05). Suppression of a central NO with central L-NAME significantly reduced mean (+/-SE) spontaneous fetal swallowing (1.2 +/- 0.1-0.6 +/- 0.1 swallows/min low-voltage ECoG; P < 0.01). Restoration of central NO by L-arginine significantly increased fetal swallowing to pre-L-NAME levels (1.2 +/- 0.1 swallows/min low voltage). There were no changes in fetal swallowing during the control study of aCSF. Fetal ECoG activity and blood pressure did not change during the study or control aCSF injection. We conclude that NO is an important neuromodulator of fetal swallowing activity. Central NO synthase activity may contribute to the heightened level of spontaneous fetal swallowing and thus amniotic fluid regulation.

Animals↗

Influence of sleep state on frequency of swallowing, apnea, and arousal in human infants.

Apnea and arousal are modulated with sleep stage, and swallowing may interfere with respiratory rhythm in infants. We hypothesized that swallowing itself would display interaction with sleep state. Concurrent polysomnography and measurement of swallowing allowed time-matched analysis of 3,092 swallows, 482 apneas, and 771 arousals in 17 infants aged 1-34 wk. The mean rates of swallowing, apnea, and arousal were significantly different, being 23.3 +/- 8.5, 9.4 +/- 8.8, and 15.5 +/- 10.6 h(-1), respectively (P < 0.001 ANOVA). Swallows occurred before 25.2 +/- 7.9% and during 74.8 +/- 6.3% of apneas and before 39.8 +/- 6.0% and during 60.2 +/- 6.0% of arousals. The frequencies of apneas and arousals were both strongly influenced by sleep state (active sleep > indeterminate > quiet sleep, P < 0.001), whether or not the events coincided with swallowing, but swallowing rate showed minimal independent interaction with sleep state. Interactions between swallowing and sleep state were predominantly influenced by the coincidence of swallowing with apnea or arousal.

Arousal↗

Effects of spontaneous swallows on breathing in awake goats.

The effects of spontaneous swallows on breathing before, during, and after solitary swallows were investigated in 13 awake goats. Inspiratory (TI) and expiratory (TE) time and respiratory output were determined from inspiratory airflow [tidal volume (VT)] and peak diaphragmatic activity (Dia(peak)). The onset time for 1,128 swallows was determined from pharyngeal muscle electrical activity. During inspiration, the later the swallowing onset, the greater increase in TI and VT, whereas there was no significant effect on TE and Dia(peak). Swallows in early expiration increased the preceding TI and reduced TE, whereas later in expiration swallows increased TE. After expiratory swallows, TI and VT were reduced whereas minimal changes in Dia(peak) were observed. Phase response analysis revealed a within-breath, phase-dependent effect of swallowing on breathing, resulting in a resetting of the respiratory oscillator. However, the shift in timing in the breaths after a swallow was not parallel, further demonstrating a respiratory phase-dependent effect on breathing. We conclude that, in the awake state, within- and multiple-breath effects on respiratory timing and output are induced and/or required in the coordination of breathing and swallowing.

Animals↗

Swallowing disorders following acute stroke: prevalence and diagnostic accuracy.

We prospectively examined 128 patients with acute first-ever stroke to determine the prevalence of swallowing disorders, the diagnostic accuracy of our clinical assessment of swallowing function compared with videofluoroscopy, and interobserver agreement for the clinical and videofluoroscopic diagnosis of swallowing disorders and aspiration. We found clinical and videofluoroscopic evidence of a swallowing disorder in 51% [95% confidence interval (CI) 42-60%] and 64% (95% CI 55-72%) of patients, respectively, and aspiration in 49% (95% CI 40-58%) and 22% (95% CI 15-29%) of patients, respectively. The optimal clinical criteria for detecting videofluoroscopic evidence of a swallowing disorder and aspiration were any clinical evidence of a swallowing disorder (sensitivity 73%, 95% CI 62-82%; specificity 89%, 95% CI 76-96%), and any clinical evidence of aspiration (sensitivity 93%, 95% CI 76-99%; specificity 63%, 95% CI 53-72%). The interobserver agreement between two speech pathologists for the clinical diagnosis of a swallowing disorder (kappa: 0.82 +/- 0.09) and aspiration (kappa: 0.75 +/- 0.09) was good, and between a speech pathologist and radiologist for the videofluoroscopic diagnosis of a swallowing disorder (kappa: 0.75 +/- 0.09) and aspiration (kappa: 0.41 +/- 0.09), it was good and fair, respectively. Although clinical bedside examination underestimates the frequency of swallowing abnormalities and overestimates the frequency of aspiration compared with videofluoroscopy, it may still offer valuable information for the diagnosis of swallowing impairment. Long-term follow-up studies are required to determine the independent functional significance of the findings of the bedside and videofluoroscopic examinations in predicting the occurrence of important outcome events such as aspiration pneumonia.

Acute Disease↗

Capsaicin desensitization inhibits swallowing reflex in guinea pigs.

To determine whether capsaicin-sensitive sensory nerves are involved in the swallowing reflex, we examined swallowing reflex in terms of the number of swallows elicited by injections of three different volumes (0.2, 0.4, and 0.6 ml) of distilled water, into the pharynx through a catheter in anesthetized guinea pigs pretreated with and without systemic capsaicin. The number of swallows was counted by submental electromyographic activity and visual observation of characteristic laryngeal movement. Injections of distilled water caused a volume-dependent increase in the number of swallows in animals treated with and without capsaicin. Capsaicin treatment significantly decreased the number of swallows elicited by all volumes of distilled water (p < 0.01). Exogenously administered substance P (SP) caused a dose-dependent increase in the number of swallows in all volumes but calcitonin gene-related peptide and acetylcholine were without effect. FK 888 (10(-5) M; 1 ml), a specific inhibitor of NK1 receptor, reduced the number of swallows elicited by distilled water to a similar degree as capsaicin treatment. Pharyngeal application of lidocaine (4%; 1 ml) also inhibited distilled water-induced swallowing. These results suggest that nonmyelinated C-fibers regulate the swallowing reflex through the release of SP in response to stimulation.

Acetylcholine↗

Coordination of swallowing and phases of respiration during added respiratory loads in awake subjects.

In order to test the hypothesis that different types of respiratory mechanical loads may differently modify the coordination of respiration and swallowing, we investigated the coordination of respiration and swallowing during resistive and elastic loads in 14 healthy subjects. Ventilation was monitored with a pneumotachograph and reflex swallowing was elicited by continuous infusion of distilled water into the pharynx (3 ml/min) and recorded on a submental electromyogram while the subject breathed through a device with a flow-resistive load (180 cm H2O/L/s), an elastic load (70 cm H2O/L), or without any external load. We found that addition of a flow-resistive load did not influence the frequency of swallowing, whereas addition of an elastic load caused a significant increase in swallowing frequency during continuous infusion of water. Analysis of the timing of swallowing in relation to respiratory cycle phase revealed that with flow-resistive loading, swallows occurred preferentially during the inspiratory-expiratory (I-E) transition, whereas with elastic loading, swallows occurred preferentially during the expiratory-inspiratory (E-I) transition. Signs of laryngeal irritation were observed most often during the elastic loading following E-I swallows. These results indicate that different types of respiratory mechanical loads can differently modify this coordination of respiration and swallowing, and suggest that the coordination may be compromised more with elastic loading than with flow-resistive loading.

Adult↗