Vocal Cord Closure Research Articles

Sugammadex to rescue a ‘can't ventilate’ scenario in an anticipated difficult intubation: is it the answer?

Sugammadex to rescue a ‘can't ventilate’ scenario in an anticipated difficult intubation: is it the answer?

Two cases of progressive vocal cord closure during desflurane–remifentanil anesthesia relieved after administration of propofol

Two cases of progressive vocal cord closure during desflurane–remifentanil anesthesia relieved after administration of propofol

Adductor laryngeal breathing dystonia in NBIA treated with botulinum toxin-A

We report a rare case of neurodegeneration with brain iron accumulation (NBIA) presented with episodic inspiratory stridor. A 10-year-old boy presented with 3-year history of gradually progressive spastic gait and generalized dystonia (involving all four limbs, neck, jaw, and speech). MRI brain showed “Eye of Tiger” sign. He recently developed severe inspiratory stridor associated with almost gasping respiration. Direct video laryngoscopy showed paradoxical vocal cord closure during inspiration. He was treated with EMG-guided botulinum toxin-A injection given into bilateral thyroarytenoid muscles, resulting in dramatic response with complete disappearance of the stridor within a week. The effect lasted 18 months.

Awake bronchoscopic intubation through an air-Q® with the application of BIPAP

To the Editor, Awake tracheal intubation is recommended for patients with a known or suspected difficult airway. A supraglottic airway device has been used as a conduit for awake intubation with a flexible bronchoscope. We describe an awake bronchoscope-guided tracheal intubation through an air-Q intubating laryngeal airway (air-Q , Mercury Medical, Clearwater, FL, USA) with continuous application of bilevel positive airway pressure (BIPAP) in a patient with a difficult airway and respiratory failure. Written consent was obtained from the patient for the publication of this article. A 46-yr-old, 146-kg man with severe obstructive sleep apnea and obesity hypoventilation syndrome was admitted to the intensive care unit (ICU) for acute respiratory failure. Six months prior, an emergency cricothyroidotomy was performed after a prolonged awake fibreoptic tracheal intubation failed due to rapid oxygen desaturation and repeated closure of false vocal cords during intubation. In this case, a decision was made to perform an urgent tracheostomy as previous tracheal intubation attempts had failed. An awake tracheostomy was likely difficult due to our patient’s anatomy, intolerance of supine positioning, and respiratory failure. Therefore, we planned to perform an awake tracheal intubation followed by induction of anesthesia and tracheostomy in the operating room (OR). The patient was transferred from the ICU to the OR on BIPAP (25/12 cm H2O); his oxygen saturation was 94% with an inspired oxygen fraction (FIO2) of 1.0, and the surgeons were prepared with their tracheostomy equipment. Standard monitors were applied, and following intravenous sedation, 4% topical lidocaine was atomized nasally and orally. During topicalization, BIPAP was reapplied repeatedly because of oxygen desaturation. The oral insertion of a size 4.5 single-use air-Q in the sitting position was well tolerated, and BIPAP was applied to the air-Q (Figure, top), followed by the insertion of a 6.5-mm endotracheal tube (ETT) via the air-Q to 14 cm. The ETT cuff was inflated, and BIPAP was connected to the ETT through a flexible connector with a bronchoscope port (Figure, bottom). A bronchoscope (outside diameter 5.2 mm) was advanced through the flexible connector past the well-visualized glottis to the carina. The ETT cuff was deflated and advanced over the bronchoscope into the trachea. After re-inflation of the ETT cuff and confirmation of tracheal positioning of the ETT with the bronchoscope, a general anesthetic was administered, and the ETT/air-Q unit was taped to the patient’s face. An oxygen saturation [ 97% was maintained during the intubation process. A tracheostomy was performed uneventfully. Bilevel positive airway pressure is used frequently in patients with respiratory failure or obstructive sleep apnea. In this case, it appears that continuous BIPAP through the air-Q was better tolerated by our patient than intermittent BIPAP via a tightly strapped facemask, and oxygenation was improved during tracheal intubation. The role of BIPAP is to improve functional residual capacity, reduce atelectasis, and prevent hypoxemia. The splinting effect of positive ventilatory pressures also prevents the collapse of upper airway structures during spontaneous breathing. By stenting open the upper airway, BIPAP may have improved our visualization of the vocal cords. Alternative techniques of awake intubation have been described with devices such as videolaryngoscopes, rigid fibreoptic laryngoscopes, and fibreoptic/lighted stylets; however, none of these D. T. Wong, MD (&) J. Wang, MD L. Venkatraghavan, MD Toronto Western Hospital, University of Toronto, Toronto, ON, Canada e-mail: david.wong@uhn.on.ca

Microaspiration in Intubated Critically Ill Patients: Diagnosis and Prevention

Microaspiration of contaminated oropharyngeal secretions and gastric contents frequently occurs in intubated critically ill patients, and plays a major role in the pathogenesis of ventilator-associated pneumonia. Risk factors for microaspiration include impossible closure of vocal cords, longitudinal folds in high-volume low-pressure polyvinyl chloride cuffs, and underinflation of tracheal cuff. Zero positive end expiratory pressure, low peak inspiratory pressure, tracheal suctioning, nasogastric tube and enteral nutrition increase the risk for microaspiration. Other patient related factors include supine position, coma, sedation, and hyperglycemia. Technetium 99 labelled enteral feeding is probably the most accurate marker of microaspiration in critically ill patients. However, use of this radioactive marker is restricted to nuclear medicine departments. Blue methylene is a reliable qualitative marker of microaspiration. However, fiberoptic bronchoscopy is required to diagnose microaspiration of blue dye in ICU patients. Quantitative pepsin measurement in tracheal aspirates is accurate in diagnosing microaspiration of gastric contents in critically ill patients. In addition, this marker is easy to use in routine practice. However, pepsin should be detected rapidly after aspiration. In vitro, and clinical studies suggested that semirecumbent position, polyurethane cuffs, positive end expiratory pressure, low-volume low-pressure cuff, and continuous control of cuff pressure were efficient in reducing microaspiration in ICU patients. Other preventive measures such as subglottic aspiration, tapered shape cuff, guayule latex cuff, lateral horizontal patient position, gastrostomy tube, and postpyloric feeding require further investingation.

Swallowing maneuver analysis using 320-row area detector computed tomography (320-ADCT)

Shibata S, Kagaya H, Inamoto Y, Saitoh E, Okada S, Ota K, Kanamori D. Swallowing maneuver analysis using 320-row area detector computed tomography (320-ADCT). Jpn J Compr Rehabil Sci 2011; 2: 54-62 Objective: Our objective was to examine whether swallowing maneuvers such as the Mendelsohn maneuver (MM) and the super-supraglottic swallow (SSGS) can be analyzed three-dimensionally and kinematically by using 320-row area detector computed tomography (320-ADCT). Methods: The subject was instructed to lean against a seat reclined at a 45° angle, hold 4 ml of 5% thickened liquid barium in the oral cavity, and then swallow normally or using the MM or the SSGS. Data were acquired for 3.15 s by using 320-ADCT, and images were reconstructed using a half-reconstruction method. The timing of each swallowing event was compared among the 3 swallowing methods. Results: We were able to determine the timing of vocal-cord closure and pharyngoesophageal segment (PES) opening during the normal swallowing method, the MM, and the SSGS. Conclusion: Swallowing maneuvers can be analyzed three-dimensionally and kinematically by using 320ADCT.

Vocal cord function and bispectral index in pediatric bronchoscopy patients emerging from propofol anesthesia

In children undergoing bronchoscopy for evaluation of stridor or respiratory symptoms, movement of the vocal cords is routinely assessed at the conclusion of flexible bronchoscopy with children still anesthetized. The effect of anesthesia on vocal cord function is not well described. This study aimed to characterize the relationship between depth of propofol anesthesia, as measured by Bispectral Index (BIS), and vocal cord movement in pediatric patients. Children between 6 months and 12 years of age presenting for diagnostic flexible bronchoscopy were enrolled in this prospective observational study. Anesthesia was maintained with a propofol infusion which was discontinued upon completion of the lower airway evaluation. An independent observer recorded the BIS score every 15 sec from discontinuation of propofol whereas the pulmonologist continued to observe vocal cord motion. BIS scores were also recorded for each observed clinical endpoint (paradoxical and normal vocal cord movement, complete vocal cord closure, and volitional movement). Data were analyzed for 47 subjects. The BIS values increased significantly from the conclusion of the lower airway evaluation with return of normal vocal cord movement, complete vocal cord closure, and volitional movement (P < 0.0005). BIS readings were higher for patients younger than 2 years. Paradoxical vocal cord movement was documented in 10.6% of subjects, but resolved in all subjects. Our findings suggest that return of vocal cord function during emergence from propofol anesthesia is related to decreasing anesthetic depth with complete vocal cord closure occurring at BIS values near those associated with volitional movement.

Evaluation of Swallowing Using 320-detector-row Multislice CT. Part II: Kinematic Analysis of Laryngeal Closure during Normal Swallowing

The purpose of this study was to (1) depict normal dynamic swallowing and (2) measure (a) the temporal characteristics of three components of laryngeal closure, i.e., true vocal cord (TVC) closure, closure of the laryngeal vestibule at the arytenoid to epiglottic base, and epiglottic inversion, and (b) the temporal relationship between these levels of laryngeal closure and other swallowing events, hyoid elevation, and the pharyngoesophageal segment (PES) using 320-detector-row multislice computed tomography (320-MSCT). The swallowing of a 10-ml portion of honey-thick liquid (5% w/v) was examined in six healthy volunteers placed in a 45° reclining position. Three-dimensional CT images were created in 29 phases at an interval of 0.10s over a 2.90-s duration. Dynamic swallowing and TVC movement were depicted clearly. The sequence for laryngeal closure was the following: (1) the hyoid started to elevate, (2) the PES opened, (3) TVC closure and closure at the arytenoid to epiglottic base occurred almost simultaneously during the hyoid elevation, and (4) the epiglottic maximum inversion occurred after the hyoid maximum displacement. Those results indicated that the onset of hyoid elevation and the early opening of the PES occurring before three levels of laryngeal closure are critical components for airway protection. 320-MSCT allowed the 3D depiction and kinematic analysis of target structures, which will increase our knowledge of airway protection mechanisms during swallowing.

Laryngospasm

Laryngospasm

Tramadol and Vocal Cord Closure

TRAMADOL is an analgesic acting as both a weak opioid agonist and an inhibitor of monoamine neurotransmitter reuptake. It also provides effective postoperative analgesia. 1 Unlike other opioids, it is well tolerated and has no clinically relevant effects on cardiovascular parameters; therefore, it is widely administered and may prove particularly useful in patients with poor cardiopulmonary function, including the elderly, and in patients with nonsteroidal antiinflammatory drug contraindications.

Vocal Cord Dysfunction Induced by Methacholine Challenge Testing

To determine whether methacholine challenge testing (MCT) provokes vocal cord dysfunction (VCD), as evidenced by inspiratory vocal cord closure on direct laryngoscopy, and whether spirometry and flow-volume loops (FVLs) demonstrate any changes that are suggestive of VCD. Prospective, controlled study. Army medical center. Thirty-four subjects all with normal baseline spirometry. Ten subjects had documented evidence of VCD, 12 subjects had exercise-induced asthma (EIA) and reactive MCT, and 12 subjects served as healthy asymptomatic control subjects. Measurement of spirometry with FVLs and direct laryngoscopy of the vocal cords performed immediately before and after subjects had undergone MCT. Evidence of inspiratory vocal cord adduction was found in four VCD patients. Two patients had adducted vocal cords at baseline, and their conditions were unchanged after undergoing MCT. Two other patients had normal conditions at baseline and demonstrated acute inspiratory vocal cord adduction after undergoing MCT. None of the patients in the EIA or control groups had evidence of VCD at baseline or after undergoing MCT. Truncation of the inspiratory limb of the FVL after MCT was noted in five patients, which correlated with evidence of VCD in 60% of these patients. One EIA patient had truncation of the inspiratory FVL after MCT, and no changes were found in the control group. A comparison of spirometry between EIA patients and VCD patients with and without evidence of inspiratory vocal cord adduction during MCT showed no significant differences. The findings suggest that MCT may cause an acute episode of vocal cord adduction and that positive results may not reflect underlying reactive airways disease. However, a flattening or truncation of the inspiratory FVL after the patient undergoes MCT is not diagnostic for the presence of inspiratory vocal cord adduction.

Prevalence of positive skin prick tests to aeroallergens in children without symptoms of allergic disease: Analysis of the NHANES III data

VOLUME 109, NUMBER 1 7' Prevalence of Positive Skin Prick Tests to Aeroallergens in | Children Without Symptoms of Allergic Disease: Analysis of the NHANES III Data Jenny M Montejo*, Michael R Simon§, Merlin Hamre*, Ronald Thomas*, Abdul H Bahrainwala* *Children's Hospital of Michigan, Wayne State University, Detroit, MI §Wayne State University, Children's Hospital of Michigan, Detroit, MI Positive skin prick tests to aeroallergens do not necessarily indicate the presence of allergy symptoms. The prevalence of positive skin prick tests for common aeroallergens in children with absence of rhinitis and asthma symptoms has not been studied. The aim of this study was to determine the prevalence of positive skin tests to aeroallergens and absence of allergic rhinitis and asthma symptoms in children ages 7 to 16 years. METHODS: The Third National Health and Nutrition Examination Survey (NHANES III), conducted from 1988 to 1994, was the source of data for this study. NHANES III is a cross-sectional, random household survey of the civilian, non-institutionalized population that used a complex, multistage probability sampling design. The survey included an extensive questionnaire regarding asthma and allergic rhinitis symptoms, spirometry, and epicutaneous skin test performed using 9 common aeroallergens: dust mite, German cockroach, cat, ragweed, Bermuda grass, rye grass, Russian thistle, white oak and Alternaria. Analyses were conducted using SUDANN software (Research Triangle Park Institute, NC) to account for the complex, multistage sampling design of the survey. Sample weights were used to produce national estimates by adjusting for the oversampling of young children and minority groups. Differences in the proportions of African-American and White children with positive skin tests, no symptoms and normal spirometry were examined using crosstabs procedure, with statistical significance set at a p-value 0.8, 18.9% had positive skin tests to at least one of the 9 aeroallergens tested. Among 4610 White and African-American children with no such symptoms and FEV 1/FVC >0.8, 17.2% of whites and 24.1% of African-Americans had positive skin tests, chi square 15.4, p 20% of FVC and FEV 1 from baseline) and laboratory responses (marked leukocytosis and hypoxemia) was observed 6 hours after pulmonary inhalation provocation test. Bronchoalveolar lavage performed 24 hours after PIPT showed a total cell count of 220.000 with marked lymphocitosis. Histopathologic examination of a transbrochial biopsy specimen revealed intersticial alveolitis. DISCUSSION: Our case gathers sufficient criteria to be considered as hypersensitivity pneumonitis caused by the dust derived from corn. We were able to detect IgG antibodies against our corn extract, and within 6 hours after PIPT with corn extract, the patient had a systemic picture closely resembling the ones he had with corn harvest. 7 -~B~ Sinus CT and Markers of Inflammation in Vocal Cord DysfuncJF~ I tion and Asthma Tina Hatley, Edward Peters, Scott Crater, Timothy McLaughlin, Thomas AE Platts-Mills, Larry Borish University of Virginia, Charlottesville, VA The paradoxical inspiratory closure of the vocal cords is characteristic of vocal cord dysfunction (VCD). These patients present with wheezing and frequently receive a misdiagnosis of asthma. Treatment with beta agonists and corticosteroids tends to be unsuccessful, and these patients therefore develop refractory disease. Our purpose was to evaluate the presence and extent of sinus disease using computed tomography (CT) and compare the findings with other aspects of airway inflammation, and markers of atopy in a series of patients with vocal cord dysfunction, acute asthma and controls. Twenty patients presenting to the University of Virginia ER or Asthma Clinic were diagnosed with clinical obstructive airway symptoms consistent with vocal cord dysfunction. Diagnosis was confirmed by a combination of history, lung function and laryngoscopy. Comparisons were made between 71 patients presenting to the university ER with acute asthma, 27 non-acute asthmatics and 56 non-asthmatic controls. Evaluation consisted of spirometry with flow-volume loops, exhaled nitric oxide gas (eNO), cell blood count for eosinophils, total serum IgE and specific IgE, as well as sinus CT scan. Sinus CT's were scored using our validated system on the basis of the opacity in each of the sinus cavities and the osteomeatal complex (max score 30). Extensive sinus CT changes (score > 12) were present in 23/71 acute asthmatic patients, 4/27 non-acute asthmatics and 2/56 nonasthmatic controls. In addition, absolute eosinophil counts, eNO, and total IgE were significantly elevated among the asthmatics. Patients with extensive sinus disease had elevated total IgE (500 IU -+ 104). Sinus symptoms reported by questionnaire did not predict sinus CT findings and were equally common among controls. Among the 20 patients with VCD, none had extensive sinus disease (mean score 2). They also had normal eNO (<10 ppb), low IgE (< 100 IU/mL), and normal eosinophil count (<200 k/I.tL ). These results demonstrate that events in the upper airway that cause airway obstruction in VCD are not related to generalized airway inflammation.

The effect of cricoid pressure on the cricoid cartilage and vocal cords: an endoscopic study in anaesthetised patients.

Cricoid pressure is used to protect the lungs from contamination with gastric contents during tracheal intubation. We studied the effect of cricoid pressure applied with a yoke on 30 anaesthetised patients examined fibreoptically through a laryngeal mask airway. We assessed the effect of 20, 30 and 44 N on the internal appearance of the cricoid and vocal cords. Difficulty in ventilation was also recorded. At 44 N, cricoid deformation occurred in 27/30 patients (90%) and 15/30 (50%) had cricoid occlusion [13/30 (43%) had cricoid occlusion at 30 N and 7/30 (23%) at 20 N]. Associated difficulty in ventilation was present in 15 patients (50%) and 18/30 (60%) had vocal cord closure with associated difficult ventilation, at forces up to 44 N. Cricoid occlusion was unrelated to age and body mass index but females were at greater risk. Orthodox values of cricoid pressure, applied with a yoke, may produce obstruction at the level of the cricoid cartilage or vocal cords, with implications for tracheal intubation and ventilation by mask.

Vocal Cord Dysfunction in Patients With Exertional Dyspnea

To evaluate patients for vocal cord dysfunction (VCD) in a military population presenting with symptoms of exertional dyspnea. Cross-sectional, controlled study. Pulmonary disease clinic at an army tertiary care center. Forty military patients with complaints of exertional dyspnea and 12 military asymptomatic control subjects. Patients underwent direct visualization of vocal cords with flexible laryngoscopy before and after exercise to evaluate for presence of inspiratory vocal cord adduction. Complete evaluation for all patients consisted of spirometry with flow-volume loops, lung volumes, diffusing capacity, and maximum voluntary ventilation at rest; chest radiograph; methacholine bronchoprovocation testing; and a maximal cardiopulmonary exercise test with expiratory gas analysis. Fifteen percent of patients studied prospectively were found to have VCD, whereas all control subjects were negative for VCD. There was minimal difference in pulmonary function testing between VCD-positive and VCD-negative patients, whereas control subjects had higher spirometric values. Twenty percent of VCD-positive patients had abnormal flow-volume loops compared with 14% of patients without VCD, but after methacholine, 60% of VCD-positive patients developed abnormal flow-volume loops. In the VCD-positive group, 60% had a positive methacholine response, but there was less decrease in FEV(1)/FVC ratio compared with either VCD-negative patients or control subjects. Paradoxical inspiratory vocal cord closure is a frequent occurrence in patients with symptoms of exertional dyspnea and should be strongly considered in their evaluation.

Difficult or impossible ventilation after sufentanil-induced anesthesia is caused primarily by vocal cord closure.

Opioid-induced rigidity often makes bag-mask ventilation difficult or impossible during induction of anesthesia. Difficult ventilation may result from chest wall rigidity, upper airway closure, or both. This study further defines the contribution of vocal cord closure to this phenomenon. With institutional review board approval, 30 patients undergoing elective cardiac surgery participated in the study. Morphine (0.1 mg/kg) and scopolamine (6 microg/kg) given intramuscularly provided sedation along with intravenous midazolam as needed. Lidocaine 10% spray provided topical anesthesia of the oropharynx. A fiberoptic bronchoscope positioned in the airway photographed the glottis before induction of anesthesia A second photograph was obtained after induction with 3 microg/kg sufentanil administered during a period of 2 min. A mechanical ventilator provided 10 ml/kg breaths at 10/min via mask and oral airway with jaw thrust. A side-stream spirometer captured objective pulmonary compliance data. Subjective airway compliance was scored. Pancuronium (0.1 mg/kg) provided muscle relaxation. One minute after the muscle relaxant was given, a third photograph was taken and compliance measurements and scores were repeated. Photographs were scored in a random, blinded manner by one investigator. Wilcoxon signed rank tests compared groups, with Bonferroni correction. Differences were considered significant at P < 0.05. Twenty-eight of 30 patients exhibited decreased pulmonary compliance and closed vocal cords after opioid induction. Two patients with neither objective nor subjective changes in pulmonary compliance had open vocal cords after opioid administration. Both subjective and objective compliances increased from severely compromised values after narcotic-induced anesthesia to normal values (P = 0.000002) after patients received a relaxant. Photo scores document open cords before induction, progressing to closed cords after the opioid (P = 0.00002), and opening again after a relaxant was administered (P = 0.00005). Closure of vocal cords is the major cause of difficult ventilation after opioid-induced anesthesia.

Lightwand intubation of infants and children

Study Objective: To examine factors contributing to successful lightwand (lighted stylet) intubation of infants and children. Design: Prospective observational study. Setting: University hospital. Patients: 125 children under age 10 years presenting for elective surgery. Interventions: Prototype lightwands specifically designed for pediatric patients were used. Intubations were done by anesthesia residents with little or no prior lightwand experience. All attempts were recorded on videotape. In a subgroup of 14 patients, an endoscopic view of the lightwand was also recorded with a flexible nasopharyngoscope. Measurements and Main Results: 125 patients with a mean age of 3.0 years (±2.4 years SD; range: 3 weeks to 9 years) were enrolled. 83.2% were intubated using the lightwand, including 75.5% (34 of 45) of infants weighing less than 10 kg. Of the 21 failed intubations, 8 were due to an inappropriately large endotracheal tube, as recognized during direct laryngoscopy; 4 were due to other reasons discussed; and 9 (persistent vallecular or esophageal entry) could not be explained from videotape analysis. Factors contributing to successful intubation included: (1) use of a shoulder roll and slight head extension; (2) conscientious alignment of airway axes; (3) anterior jaw lift to elevate the epiglottis; and (4) gentle handling of the lightwand to avoid displacing soft tissue. Inability to advance the lightwand despite correct glow is caused by entrapment in the vallecula, hang up of the lightwand on the aryepiglottic folds, subglottic narrowing, or vocal cord closure. Conclusions: Lightwand intubation in children uses both tactile and visual cues regarding the location of the endotracheal tube tip. Attention to detail results in a high level of success among novice users of the pediatric lightwand. Endoscopic and external videotaping gave us a means of monitoring the progress of mechanical skills among novice users.

Laryngeal deglutition movement in Parkinson's disease.

Laryngeal muscle function is defective in Parkinson's disease (PD) patients; the intrinsic group (vocal cords) is defective during phonation and the extrinsic group (laryngeal strap muscles) is slow during deglutition. There are no studies of vocal cord motility during deglutition in PD. We investigated laryngeal motility during deglutition in 71 patients with PD in a videofluoroscopic swallowing study. Patients were subdivided into two groups by the Hoehn and Yahr disability scale, stages II and III (n = 38) and stages IV and V (n = 33). At least one abnormality of laryngeal movement was present in 68 of 71 patients (95.8%); most patients had multiple abnormalities. There was statistically significant slowing of vertical laryngeal excursion; true vocal cord closure; or delayed, incomplete, or absent opening of the true vocal cords. Patients with more advanced disease manifested more deficits of laryngeal movement. Laryngeal dysmotility in PD may be related to defective descending basal ganglionic control of medullary deglutory and phonatory motor functions.

Dynamic magnetic resonance imaging of vocal cord closure during deglutition

Background & Aims : Vocal cord closure is instrumental in airway protection during deglutition. Conventional imaging of vocal cord closure and reopening during deglutition requires invasive and nonphysiological methods. The aim of this study was to characterize the biomechanical properties of normal vocal cord adduction/abduction during deglutition using echoplanar magnetic resonance imaging, a technique that has the capability of imaging soft-tissue motion with real-time temporal resolution. Methods : The movements of laryngeal and vocal cord structures during swallowing were determined in 11 normal volunteers by single slice and axially reformatted multislice coronal echoplanar images. Results : During swallowing, the larynx ascended to peak elevation, maintained peak elevation for a discrete interval, and descended to its resting position. Vocal cord adduction occurred with a symmetric tent-like configuration at the midpoint of maximal laryngeal elevation, whereas vocal cord abduction occurred at the midpoint of laryngeal descent. Spatial analysis of vocal cord configuration during adduction determined that the vocal cords attained an initial parallel configuration during ascent, followed by closure at peak laryngeal elevation. Conclusions : These results show that the vocal cords adduct and abduct synchronously with laryngeal ascent and descent, respectively, during deglutition. Echoplanar magnetic resonance imaging constitutes a novel tool used to assess clinical abnormalities of deglutitive laryngeal function.

Timing of glottic closure during normal swallow.

The purpose of this study was to determine the temporal characteristics and patterns of glottic closure during normal swallow using concurrent videofluoroscopy and videoendoscopy. Three swallows each of four bolus types were examined in eight healthy volunteers with the endoscope in two positions: at the level of the uvula and at the laryngeal vestibule. Data analysis compared: (1) temporal relationships between laryngeal behaviors and oropharyngeal swallow events and (2) airway conditions at the time of key oropharyngeal events. Although arytenoid adduction and subsequent arytenoid contact occurred as one of the initial events during swallow, the timing of these events was highly variable. On the other hand, true vocal cord (TVC) closure occurred mainly after the onset of laryngeal elevation, and it was affected by bolus volume. In normal swallow, arytenoid closure did not always mean complete TVC closure, and complete TVC closure might be accomplished during the process of laryngeal elevation and arytenoid tilting.

2 Upper airway reflexes

The maintenance of a clear unobstructed upper airway and the rapid return of normal laryngeal reflexes after the end of general anaesthesia form two of the most fundamental principles of modern anaesthetic practice. Upper airway reflexes are of considerable importance to clinical anaesthetists. The sensitivity of the upper airway reflexes are important during induction of anaesthesia, when heightened upper airway reflexes may lead to the development of life threatening laryngospasm. Following anaesthesia the larynx plays a primary role in protecting the lungs from aspiration of foreign material. The irritant nature of inhalation anaesthetic agents varies, with halothane being one of the least irritant. Newer agents including isoflurane and desflurane have been found to be associated with a much higher incidence of airway irritation. The intravenous anaesthetic induction agents thiopentone and propofol seem to have different actions on the sensitivity of upper airway reflexes during induction of anaesthesia, the upper airway appearing to be less irritable following propofol. Laryngospasm is a common and potentially dangerous complication of general anaesthesia, the incidence is higher in young children particularly between the ages of 1 and 3 months. Upper respiratory tract infection increases the incidence of laryngospasm. This is thought to be due to the viral infection causing shedding of epithelial cells, leading to increased exposure of intraepithelial sensory receptors to inhaled irritants. Histologically, sensory nerve fibres are found in almost all areas of the laryngeal mucosa. A particularly high density of sensory free nerve endings are found in the posterior supraglottis. Stimulation of irritant receptors in the upper respiratory tract causes a reflex motor response, afferent signals travel in the vagus nerve and project centrally to the caudal and posterior parts of the nucleus tractus solitarius. The efferent response results in vocal cord closure, changes in respiratory rhythm and coughing, which together act to protect the lower airway from foreign material.