Temporal coordination of pharyngeal and laryngeal dynamics with breathing during swallowing: single liquid swallows.
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The critical integration of timing and patterning between respiratory and swallowing events was studied with simultaneous videofluoroscopic and respiratory recording during single liquid swallows. Respiratory phase patterns and the onsets and durations of 12 predetermined swallowing events and associated respiratory activities were studied. Results showed four highly repeatable, temporally oriented sequences (clusters) of swallowing and related respiratory events. Two respiratory phase patterns were identified without statistically significant differences in frequency of occurrence between age, gender, or race. These findings will aid in the identification of normal and abnormal patterns of breathing and swallowing in patients with dysphagia. (+info)
Cephalometric norms for the upper airway in a healthy Hong Kong Chinese population.
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OBJECTIVE: To obtain normative data for cephalometric measurements of the upper airway in the local Chinese population. DESIGN: Observational study. SETTING: University department and teaching hospital out-patient clinic. SUBJECTS AND METHODS: Subjects included 74 healthy patients, 29 males (age range, 18-35 years) and 45 females (age range, 16-42 years), with normal skeletal facial profile, no history of snoring, sleep apnoea, upper airway disease, tonsillectomy or adenoidectomy, obesity, or pathology in the pharynx. Twenty cephalometric airway measurements, including size of the tongue, soft palate, nasopharynx, oropharynx, hypopharynx, and relative position of the hyoid bone and valleculae were obtained. Landmarks on cephalometric radiographs were digitised and measurements were made using a specially designed computer programme. Error analysis of measurements was performed and comparison of measurements according to sex was made. RESULTS: Significant sex dimorphism was seen for the majority of measurements, with the exception of minimal depth of the airway, oropharyngeal depth of the airway, and the soft palate angle with the hard palate. CONCLUSION: A minimum sagittal dimension of the upper airway was evident despite differences in measurements between sexes. Findings from this study should be a useful reference for the assessment of sleep apnoea in the local population. (+info)
Characterization of laryngopharyngeal reflux in patients with premalignant or early carcinomas of the larynx.
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BACKGROUND: An association between laryngopharyngeal reflux (LPR) and laryngeal carcinoma has been suggested, but remains unproven. The current pilot study was performed to determine the incidence of LPR among patients with early laryngeal carcinomas or dysplasia and to examine the associations between levels of LPR and histologic stage, smoking status, the symptom of heartburn, and body position during reflux episodes. METHODS: Behavioral and 24 hour pH monitoring data were prospectively acquired and analyzed for 40 previously untreated adults with dysplasia, T1 or T2 laryngeal carcinomas. RESULTS: Eighty-five percent of patients had LPR. No significant association was shown between the level of LPR and histologic stage or smoking status. Heartburn did not predict LPR. The incidence of LPR in the upright body position was 91%, compared with 9% in the supine position, among patients with LPR. CONCLUSIONS: When compared to available normative data, the current findings show a high incidence of LPR in patients with premalignant and early laryngeal cancer. These findings highlight the need for a matched-control study evaluating LPR as a potential predisposing factor for laryngeal carcinoma. (+info)
Active upper airway closure during induced central apneas in lambs is complete at the laryngeal level only.
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We tested the hypotheses that active upper airway closure during induced central apneas in nonsedated lambs 1). is complete and occurs at the laryngeal level and 2). is not due to stimulation of the superior laryngeal nerves (SLN). Five newborn lambs were surgically instrumented to record thyroarytenoid (TA) muscle (glottal constrictor) electromyographic (EMG) activity with supra- and subglottal pressures. Hypocapnic and nonhypocapnic central apneas were induced before and after SLN sectioning in the five lambs. A total of 174 apneas were induced, 116 before and 58 after sectioning of the internal branch of the SLN (iSLN). Continuous TA EMG activity was observed in 88% of apneas before iSLN section and in 87% of apneas after iSLN section. A transglottal pressure different from zero was observed in all apneas with TA EMG activity, with a mean subglottal pressure of 4.3 +/- 0.8 cmH2O before and 4.7 +/- 0.7 cmH2O after iSLN section. Supraglottal pressure was consistently atmospheric. Sectioning of both iSLNs had no effects on the results. We conclude that upper airway closure during induced central apneas in lambs is active, complete, and occurs at the glottal level only. Consequently, a positive subglottal pressure is maintained throughout the apnea. Finally, this complete active glottal closure is independent from laryngeal afferent innervation. (+info)
How high do the subclavian arteries ascend into the neck? A population study using magnetic resonance imaging.
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BACKGROUND: The relationship between the larynx and the subclavian arteries was studied in a series of magnetic resonance images (MRIs) from 50 patients without neck pathology. METHODS: The vertical distances of the excursion of the subclavian arteries into the neck was measured, as was the distance from the cricoid cartilage to the highest point of this excursion. Statistical analysis allows the probability of any given cricoid-subclavian distance occurring in the population to be estimated. RESULTS: The mean (SD) excursion of the right subclavian artery above the clavicle was 10.4 (11.4) mm. The mean (SD) distance from the cricoid cartilage to the right subclavian artery was 30.6 (14.3) mm, and the data showed a high degree of variance. There was a linear relationship between neck length and cricoid-subclavian distance (r=0.58), which explained some of the variance in the latter, but there was also wide individual variance, which was independent of this regression. CONCLUSIONS: When performing a percutaneous tracheostomy, a 'safe' distance between the incision site and subclavian artery cannot be assumed or reliably predicted from the neck length. (+info)
Prolongation of the laryngeal chemoreflex after inhibition of the rostral ventral medulla in piglets: a role in SIDS?
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We tested the hypothesis that inhibition of neurons within the rostral ventral medulla (RVM) would prolong the laryngeal chemoreflex (LCR), a putative stimulus in the sudden infant death syndrome (SIDS). We studied the LCR in 19 piglets, age 3-16 days, by injecting 0.05 ml of saline or water into the larynx during wakefulness, non-rapid eye movement (NREM) sleep, and REM sleep, before and after 1 or 10 mM muscimol dialysis in the RVM. Muscimol prolonged the LCR (P < 0.05), and the prolongation was greater when the LCR was stimulated with water compared with saline (P < 0.02). The LCR was longer during NREM sleep than during wakefulness and longest during REM sleep (REM compared with wakefulness). Muscimol had no effect on the likelihood of arousal from sleep after LCR stimulation. We conclude that the RVM provides a tonic facilitatory drive to ventilation that limits the duration of the LCR, and loss of this drive may contribute to the SIDS when combined with stimuli that inhibit respiration. (+info)
Laryngeal morbidity and quality of tracheal intubation: a randomized controlled trial.
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BACKGROUND: Vocal cord sequelae and postoperative hoarseness during general anesthesia are a significant source of morbidity for patients and a source of liability for anesthesiologists. Several risk factors leading to laryngeal injury have been identified in the past. However, whether the quality of tracheal intubation affects their incidence or severity is still unclear. METHODS: Eighty patients were randomized in two groups (n = 40 for each) to receive a propofol-fentanyl induction regimen with or without atracurium. Intubation conditions were evaluated with the Copenhagen Score; postoperative hoarseness was assessed at 24, 48, and 72 h by a standardized interview; and vocal cords were examined by stroboscopy before and 24 and 72 h after surgery. If postoperative hoarseness or vocal cord sequelae persisted, follow-up examination was performed until complete restitution. RESULTS: Without atracurium, postoperative hoarseness occurred more often (16 vs. 6 patients; P = 0.02). The number of days with postoperative hoarseness was higher when atracurium was omitted (25 vs. 6 patients; P < 0.001). Similar findings were observed for vocal cord sequelae (incidence of vocal cord sequelae: 15 vs. 3 patients, respectively, P = 0.002; days with vocal cord sequelae: 50 vs. 5 patients, respectively, P < 0.001). Excellent intubating conditions were less frequently associated with postoperative hoarseness compared to good or poor conditions (11, 29, and 57% of patients, respectively; excellent vs. poor: P = 0.008). Similar findings were observed for vocal cord sequelae (11, 22, and 50% of patients, respectively; excellent vs. poor: P = 0.02). CONCLUSIONS: The quality of tracheal intubation contributes to laryngeal morbidity, and excellent conditions are less frequently associated with postoperative hoarseness and vocal cord sequelae. Adding atracurium to a propofol-fentanyl induction regimen significantly improved the quality of tracheal intubation and decreased postoperative hoarseness and vocal cord sequelae. (+info)
Sensory regulation of swallowing and airway protection: a role for the internal superior laryngeal nerve in humans.
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During swallowing, the airway is protected from aspiration of ingested material by brief closure of the larynx and cessation of breathing. Mechanoreceptors innervated by the internal branch of the superior laryngeal nerve (ISLN) are activated by swallowing, and connect to central neurones that generate swallowing, laryngeal closure and respiratory rhythm. This study was designed to evaluate the hypothesis that the ISLN afferent signal is necessary for normal deglutition and airway protection in humans. In 21 healthy adults, we recorded submental electromyograms, videofluoroscopic images of the upper airway, oronasal airflow and respiratory inductance plethysmography. In six subjects we also recorded pressures in the hypopharynx and upper oesophagus. We analysed swallows that followed a brief infusion (4-5 ml) of liquid barium onto the tongue, or a sip (1-18 ml) from a cup. In 16 subjects, the ISLN was anaesthetised by transcutaneous injection of bupivacaine into the paraglottic compartment. Saline injections using the identical procedure were performed in six subjects. Endoscopy was used to evaluate upper airway anatomy, to confirm ISLN anaesthesia, and to visualise vocal cord movement and laryngeal closure. Comparisons of swallowing and breathing were made within subjects (anaesthetic or saline injection vs. control, i.e. no injection) and between subjects (anaesthetic injection vs. saline injection). In the non-anaesthetised condition (saline injection, 174 swallows in six subjects; no injection, 522 swallows in 20 subjects), laryngeal penetration during swallowing was rare (1.4 %) and tracheal aspiration was never observed. During ISLN anaesthesia (16 subjects, 396 swallows), all subjects experienced effortful swallowing and an illusory globus sensation in the throat, and 15 subjects exhibited penetration of fluid into the larynx during swallowing. The incidence of laryngeal penetration in the anaesthetised condition was 43 % (P < 0.01, compared with either saline or no injection) and of these penetrations, 56 % led to tracheal aspiration (without adverse effects). We further analysed the swallow cycle to evaluate the mechanism(s) by which fluid entered the larynx. Laryngeal penetration was not caused by premature spillage of oral fluid into the hypopharynx, delayed clearance of fluid from the hypopharynx, or excessive hypopharyngeal pressure generated by swallowing. Furthermore, there was no impairment in the ability of swallowing to halt respiratory airflow during the period of pharyngeal bolus flow. Rather, our observations suggest that loss of airway protection was due to incomplete closure of the larynx during the pharyngeal phase of swallowing. In contrast to the insufficient closure during swallowing, laryngeal closure was robust during voluntary challenges with the Valsalva, Muller and cough manoeuvres under ISLN anaesthesia. We suggest that an afferent signal arising from the ISLN receptor field is necessary for normal deglutition, especially for providing feedback to central neural circuits that facilitate laryngeal closure during swallowing. The ISLN afferent signal is not essential for initiating and sequencing the swallow cycle, for co-ordinating swallowing with breathing, or for closing the larynx during voluntary manoeuvres. (+info)