Laryngeal Response Research Articles

Quantification of rat supraglottic laryngeal sensation threshold.

Laryngeal adductor response (LAR) to air puff is used as a reliable method in evaluating sensation thresholds (ST) in human laryngeal sensory disorders. This method has been difficult to perform in small subjects such as rodents. The aims of this study were to 1) evaluate ST to air puff under binocular microlaryngoscopy in rats to evaluate laryngeal sensory disorders, 2) determine sensory thresholds at varying target locations, and 3) determine the ideal depth of anesthesia. Animal study. Rats were induced with ketamine/xylazine. The level of anesthesia was monitored by spontaneous glottic closure and corneal reflex testing. Air puffs were delivered to the epiglottis, arytenoid, and piriform sinus at varied pressures with pulse time kept constant. Sensation thresholds were determined by direct visualization of the larynx using a binocular microscope. Topical lidocaine was then applied to the larynx and ST was determined. Trials were repeated in a small subset of animals. Twenty-six trials were performed in 14 rats. Mean STs were 39 ± 9.7 mm Hg at the epiglottis, 48.8 ± 10.5 at the arytenoid, and not detectable at the pyriform sinus. Repeated trials demonstrated consistent results. Lidocaine effectively ablated the LAR in each trial. The LAR was difficult to induce while corneal reflex was absent and was difficult to distinguish from spontaneous glottic closures while under lighter sedation. Air pulse stimulation in rats is a simple, reliable, and effective way to determine laryngopharyngeal STs in rats and can be used as an efficient and affordable method for experimentation involving laryngeal sensory disorders. NA. Laryngoscope, 127:E265-E269, 2017.

Evaluation of the Cortical Silent Period of the Laryngeal Motor Cortex in Healthy Individuals.

Objective: This work aimed to evaluate the cortical silent period (cSP) of the laryngeal motor cortex (LMC) using the bilateral thyroarytenoid (TA) muscles with transcranial magnetic stimulation (TMS).Methods: In 11 healthy participants, fine-wire electromyography (EMG) was used to record bilateral TA muscle responses to single pulse TMS delivered to the LMC in both hemispheres. Peripheral responses to stimulation over the mastoid, where the vagus nerve exits the skull, were collected to verify the central origin of the cortical stimulation responses by comparing the latencies.Results: The cSP duration ranged from 41.7 to 66.4 ms. The peripherally evoked motor-evoked potential (MEP) peak occurred 5–9 ms earlier than the cortical responses (for both sides of TAs: p < 0.0001) with no silent period. The right TA MEP latencies were earlier than the left TA responses for both peripheral and cortical measures (p ≤ 0.0001).Conclusion: These findings demonstrate the feasibility of measuring cSP of LMC based on intrinsic laryngeal muscles responses during vocalization in healthy volunteers.Significance: The technique could be used to study the pathophysiology of neurological disorders that affect TA muscles, such as spasmodic dysphonia. Further, the methodology has application to other muscles of the head and neck not accessible using surface electrodes.

Impact of high concentrations of sevoflurane on laryngeal reflex responses.

Exaggerated defensive upper airway reflexes, particularly laryngospasm, may cause hypoxemic damage, especially in children. General clinical experience suggests that laryngeal reflex responses are more common under light levels of anesthesia, and previous clinical studies have shown an inverse correlation between laryngeal responsiveness and depth of hypnosis. However, this seems to be less obvious in children anesthetized with sevoflurane. The aim of this study was to assess the impact of high concentrations of sevoflurane on laryngeal and respiratory reflex responses in spontaneously breathing children. Accordingly, we tested the hypothesis that laryngeal and respiratory reflex responses were completely suppressed in spontaneously breathing children when anesthetized with sevoflurane 4.7% (=MACED95Intubation ) as compared with sevoflurane 2.5% (=1MAC). In this prospective observational study, we tested the hypothesis that the incidence of laryngospasm evoked by laryngeal stimulation is diminished under high concentrations of sevoflurane. Following Ethics approval, trial registration, and informed consent, 40 children (3-7years) scheduled for elective surgery participated in the trial. All children received sevoflurane 2.5% (1 MAC) and 4.7% (ED95Intubation ) in random order with 5-min equilibration between the states. Under both conditions, distilled water was sprayed under bronchoscopic view onto the larynx. Potential laryngeal and respiratory reflex responses were assessed offline by a blinded reviewer. Laryngospasm (episodes lasting >10s) occurred in 12/38 (32%) of the patients anesthetized with sevoflurane 2.5%, vs 7/38 (18%) in those anesthetized with sevoflurane 4.7% (difference: OR 3.5; 95% CI [0.72-16.84], P=0.18). All other reflex responses (coughing, expiration reflexes, and spasmodic panting) were infrequent and were similar among the examined concentrations. Against our hypothesis, laryngospasm could still be observed in 18% of children under the higher concentration of sevoflurane (4.7%, ED95Intubation ).

Does the Use of Lidocaine in Dogs and Cats Reduce Post-Operative Tracheitis?

&lt;p style="margin-left: 0in;" lang="en-US"&gt;&lt;strong&gt;Clinical bottom line:&lt;/strong&gt;&lt;/p&gt;&lt;p style="margin-left: 0in;" lang="en-US"&gt;Examination of a human systematic review and two veterinary prospective trials suggest topical application on the glottis, and placement of lidocaine on the endotracheal tube both seem to improve sore throat and laryngeal response in animals. Choice of pre-medicants and induction agents appears to have an impact on the extent of lidocaine efficacy. Consideration should be given in allowing enough time for lidocaine placement to have effect (around 60-90 seconds). Limitations in more confident assertions of the efficacy of lidocaine being utilized to prevent tracheitis is that only the human systematic review had enough follow up time to examine the benefits of lidocaine on sore throat in intubation.&lt;/p&gt;&lt;p style="margin-left: 0in;" lang="en-US"&gt; &lt;/p&gt;&lt;br /&gt; &lt;img src="https://www.veterinaryevidence.org/rcvskmod/icons/oa-icon.jpg" alt="Open Access" /&gt; &lt;img src="https://www.veterinaryevidence.org/rcvskmod/icons/pr-icon.jpg" alt="Peer Reviewed" /&gt;

Vagal and recurrent laryngeal nerves neuromonitoring during thyroidectomy and parathyroidectomy: A prospective study

ObjectivesThe aim of the study was to stimulate the vagal and the recurrent laryngeal nerves during and after thyroidectomy or parathyroidectomy, to record muscle responses, interpret the electrophysiological modifications and identify prognostic factors for postoperative vocal fold mobility. Patients and methodsA prospective study monitored 151 vagal nerves and 144 recurrent laryngeal nerves in 114 patients. Seven patients (14 vagal nerves) underwent continuous monitoring via an automatic periodic stimulation (APS®) electrode. In 15 patients (21 vagal nerves), the stimulation threshold was studied. Muscle response was recorded on direct vagal and/or recurrent laryngeal nerve stimulation by a monopolar electrode or direct repeated stimulation via an electrode on the vagal nerve. In case of signal attenuation on the first operated side, surgery was not extended to the contralateral side. ResultsThe vagal nerve stimulation checked inferior laryngeal nerve integrity and recurrent status, without risk of false negatives. The vagal nerve stimulation threshold, before and after dissection, that induced a muscle response of at least 100μV ranged from 0.1 to 0.8mA. Similarity between pre- and post-dissection responses to supramaximal stimulation, defined as 1mA, on the one hand, and between post-dissection vagal and laryngeal recurrent nerve responses on the other correlated with normal postoperative vocal cord mobility. Conversely, muscle response attenuation below 100μV and increased latency indicated a risk of vocal fold palsy. ConclusionVagal nerve stimulation allows suspicion or elimination of lesions on the inferior laryngeal nerve upstream of the stimulation point and detection of non-recurrent inferior laryngeal nerve. Intermittent monitoring assesses nerve function at the moment of stimulation, while continuous monitoring detects the first signs of nerve injury liable to induce postoperative recurrent nerve palsy. When total thyroidectomy is indicated, signal attenuation on the first operated side casts doubt on continuing surgery to the contralateral side in the same step.

Prevention of laryngospasm with rocuronium in cats: a dose-finding study

ObjectiveTo identify the dose of rocuronium that will prevent a laryngeal response to water spraying of the glottis in anesthetized cats. Study designRandomized crossover study. AnimalsEight healthy, adult, short-haired cats, aged 1–4 years, weighing 3.2–6.0 kg. MethodsEach cat was anesthetized four times and administered one of four doses of rocuronium (0.1, 0.2, 0.3 and 0.6 mg kg−1) in random order. The larynx was observed with a video-endoscope inserted through a laryngeal mask airway. Video-clips of the laryngeal response to a sterile water spray (0.2 mL) were obtained at baseline (without rocuronium) and at maximal effect of each treatment. Glottal closure score (0–2), duration of glottal closure, and number of adductive arytenoid movements were obtained from video-clips of laryngeal responses (reproduced in slow motion) at baseline and after treatment. Two observers blinded to treatment allocation scored the vigor of the laryngeal response on a visual analog scale (VAS). The duration of apnea (up to 5 minutes) was recorded for each treatment. ResultsCompared with baseline, rocuronium 0.3 mg kg−1 and 0.6 mg kg−1 significantly decreased all glottal scores obtained from the videos (all p < 0.03). Both observers gave lower VAS scores after 0.3 mg kg−1 (both p = 0.015). Apnea lasting ≥ 5 minutes occurred in none, one, three and seven of eight cats administered doses of rocuronium 0.1, 0.2, 0.3 and 0.6 mg kg−1, respectively. Conclusions and clinical relevanceRocuronium 0.3 mg kg−1 and 0.6 mg kg−1 consistently decreased the completeness and duration of the laryngeal response to water spray, and reduced the number of arytenoid adductive movements in response to that stimulus. However, a laryngeal response was never completely prevented. Rocuronium 0.3 mg kg−1 may be useful for facilitating tracheal intubation. Positive pressure ventilation must be available for cats administered rocuronium.

A sequential anesthesia technique for surgical repair of unilateral vocal fold paralysis.

Thyroplasty with arytenoid adduction, a combined procedure for treatment of unilateral vocal fold paralysis, is typically performed under local anesthesia with sedation to allow for intraoperative voice assessment. However, the need for patient immobility and suppression of laryngeal responses to surgical manipulation can make sedation-analgesia challenging. We describe our first 26 consecutive cases undergoing thyroplasty and arytenoid adduction with a standardized technique consisting of a combination of general anesthesia with tracheal intubation followed by sedation-analgesia. Most patients (69%) were women, with age of 53±15years (mean±SD). Neck surgery was the cause of vocal fold paralysis in 50% of patients. Initially, general anesthesia was maintained with desflurane and remifentanil with dexmedetomidine added just before tracheal extubation. During the sedation-analgesia phase, patients received infusions of remifentanil and dexmedetomidine. Duration of general anesthesia and sedation-analgesia phases was 162±68.2 and 79±18.3min, respectively. Mean (SD) wake-up time was 8.0±4.0min after desflurane discontinuation. Extubation occurred without coughing, bucking, or agitation in 96% of patients. All the patients were able to phonate appropriately and remained comfortable after emergence. This technique allowed improved surgical conditions with reduced patient discomfort and may be advantageous for other laryngeal and neck surgeries in which intraoperative patient feedback is required.

Laryngeal response patterns influence the efficacy of mechanical assisted cough in amyotrophic lateral sclerosis

BackgroundMost patients with amyotrophic lateral sclerosis (ALS) are treated with mechanical insufflation–exsufflation (MI-E) in order to improve cough. This method often fails in ALS with bulbar involvement, allegedly due to...

Oropharyngeal pH Testing Does Not Predict Response to Proton Pump Inhibitor Therapy in Patients with Laryngeal Symptoms.

Predicting response to proton pump inhibitor (PPI) therapy in patients with laryngeal symptoms is challenging. The Restech Dx-pH probe is a transnasal catheter that measures oropharyngeal pH. In this study, we aimed to investigate the prognostic potential of oropharyngeal pH monitoring to predict responsiveness to PPI therapy in patients with laryngeal symptoms. We conducted a physician-blinded prospective cohort study at a single academic institution between January 2013 and October 2014. Adult patients with Reflux Symptom Index scores (RSI) ≥13 off PPI therapy were recruited. Patients underwent video laryngoscopy and 24-h oropharyngeal pH monitoring, followed by an 8- to 12-week trial of omeprazole 40 mg daily. Prior to and following PPI therapy, patients completed various symptom questionnaires. The primary outcome was the association between PPI response and oropharyngeal pH metrics. PPI response was separated into three subgroups based on the post-treatment RSI score and % RSI response: non-response=RSI ≥13; partial response=post-treatment RSI <13 and change in RSI <50%; and complete response=post-treatment RSI <13 and change in RSI ≥50%. The primary analysis utilized a multinomial logistic regression controlling for the pre-treatment RSI score. A secondary analysis assessed the relationship between the change in RSI (post-pre) and oropharyngeal pH metrics via ordinary least square regression. Thirty-four patients completed the study and were included in final analysis. Symptom response to PPI therapy was as follows: 50% no response, 15% partial response, and 35% complete response. Non-responders had a higher pre-treatment RSI (P<0.01). There were no significant differences in oropharyngeal acid exposure (below pH of 4.0, 5.0, 5.5, 6.0, and RYAN scores) between responder types. The secondary analysis noted a trend between lower PPI response and a greater total percent time below pH of 5.0 (P=0.03), upright percent time below pH of 5.0 (P=0.07), and RYAN supine (corrected; P=0.03), as well as an association between PPI response and greater decreases in the Anxiety Sensitivity Inventory (P<0.01), Brief Symptom Inventory-18 (P<0.01), and Negative Affect Scale (P<0.01). Oropharyngeal pH testing did not predict laryngeal symptom response to PPI therapy. Contrary to hypothesis, our study signaled that the degree of oropharyngeal acid exposure is inversely related to PPI response. In addition, reduction in negative affect and psychological distress parallels PPI response.

Vitamin D deficiency and exercise-induced laryngospasm in young competitive rowers.

Exercise-induced dyspnea is common among adolescents and young adults and often originates from exercise-induced bronchoconstriction (EIB). Sometimes, dyspnea corresponds to exercise-induced laryngospasm (EILO), which is a paradoxical decrease in supraglottic/glottic area. Vitamin D deficiency, which occurs frequently at northern latitudes, might favor laryngospasm by impairing calcium transport and slowing striate muscle relaxation. The aim of this study was to evaluate whether vitamin D status has an influence on bronchial and laryngeal responses to exercise in young, healthy athletes. EIB and EILO were investigated during winter in 37 healthy competitive rowers (24 males; age range 13-25 years), using the eucapnic voluntary hyperventilation test (EVH). EIB was diagnosed when forced expiratory volume in the first second decreased by 10%, EILO when maximum mid-inspiratory flow (MIF50) decreased by 20%. Most athletes (86.5%) had vitamin D deficiency (below 30 ng/mL), 29 mild-moderate (78.4%) and 3 severe (8.1%). EVH showed EIB in 10 subjects (27%), EILO in 16 (43.2%), and combined EIB and EILO in 6 (16.2%). Athletes with EILO had lower vitamin D (19.1 ng/mL vs. 27.0 ng/mL, p < 0.001) and higher parathyroid hormone (30.5 pg/mL vs. 19.2 pg/mL, p = 0.006) levels. The degree of laryngoconstriction (post-EVH MIF50 as a percentage of pre-EVH MIF50) was related directly with vitamin D levels (r = 0.51; p = 0.001) and inversely with parathyroid hormone levels (r = -0.53; p = 0.001). We conclude that vitamin D deficiency is common during winter in young athletes living above the 40th parallel north and favors laryngospasm during exercise, probably by disturbing calcium homeostasis. This effect may negatively influence athletic performance.

Comparison of Truview PCD and Trupti blade laryngoscope in adult patients of anticipated difficult Intubation

Background: The Truview PCD and Trupti blade provide better view of vocal cords and do not require the proper alignment of the oral, pharyngeal, and laryngeal axes as required with the Macintosh blade. Objective: To compare the laryngeal view and hemodynamic response to laryngoscopy and intubation with Truview PCD and Trupti blade in cases with single or multiple predictors of difficult intubation (PDI). Materials and Methods: Sixty adult patients of both sexes who were scheduled to undergo general anesthesia with endotracheal intubation were divided into two groups. Laryngoscopy was performed with Truview blade in group A and with Trupti blade in group B. Laryngeal view was graded by the Cormack–Lehane classification after laryngoscopy. Hemodynamic response during laryngoscopy and intubation was compared in both the groups. Results: Truview PCD was found to have better Cormack–Lehane glottic view and less hemodynamic response. The time required for the tracheal intubation was higher with Truview PCD blade than that with Trupti blade. Conclusion: The Truview PCD and Trupti blade both are better for intubation in adult patients having less than three PDI.

External Branch of the Superior Laryngeal Nerve Mediated Glottic Closing Force in the Porcine Model.

Based on our laboratory's newly confirmed motor pathway for glottic closure, we measured the glottic closing force (GCF) during isolated stimulation of the external branch of the superior laryngeal nerve (eSLN) in the porcine model. Glottic closure is 1 of the primary mechanisms for prevention of aspiration during deglutition. The recurrent laryngeal nerve (RLN) and eSLN were identified bilaterally in 4 porcine necks. Subsequently, GCF was measured with a pressure transducer as the distal ends of individual nerves were stimulated in 4 animals. The RLN mediated GCF was measured first, followed by isolated eSLN mediated GCF, followed by transection of the RLN and repeat measurement of the eSLN GCF. Ultimately, the cricothyroid (CT) muscle attachment was released and the GCF measured. The GCF during isolated eSLN stimulation before and after RLN transection is approximately 89% of the RLN mediated GCF in each animal. The GCF after CT release is approximately 84% of the RLN perceived GCF. Transection of the RLN did not alter the eSLN observed GCF. The GCF obtained during isolated eSLN stimulation is adequate for delivery of an appropriate laryngeal protective response and may be considered a target motor nerve for augmenting GCF in selected rehab settings.

Lower Oropharyngeal Acid Exposure and Higher Psychological Distress Exists Amongst Subjects With Laryngeal Symptoms and Response to PPI Therapy

Introduction: Predicting therapeutic response in patients with laryngopharyngeal reflux (LPR) symptoms is challenging. Consequently, patients with suspected LPR often receive empiric proton-pump inhibitor (PPI) therapy and up to 50% may not respond. The Restech Dx-pH probe is a transnasal catheter that measures oropharyngeal pH. We hypothesized that higher oropharyngeal acid burden is associated with a greater PPI response. The aims of this study were to (1) correlate oropharyngeal pH probe parameters with PPI response and (2) evaluate if alternative clinical surrogates predict PPI response. Methods: This was a physician blinded prospective cohort study conducted at a tertiary care teaching institution between 1/2013 and 10/2014. Adult subjects with laryngeal symptoms >1 month and a Reflux Symptom Index score (RSI) ≥13 off PPI therapy 2 weeks prior to study were recruited from an otolaryngology clinic. Laryngoscopy and oropharyngeal pH assessment with the Restech Dx-pH system were first performed, followed by an 8 to 12 week trial of omeprazole 40 mg once daily. Prior to, and following PPI therapy, subjects completed various symptom questionnaires [Table 1]. PPI response was defined as > mean delta RSI (difference between pre- and post-PPI therapy RSI).Table 1: Clinical variables by PPI Responder & Non-responder groupsResults: Of 34 subjects, 15 (44%) had a PPI response. Percent time of oropharyngeal pH below 5.0 did not correlate with change in RSI (Spearman's rho -0.07, P=0.7); similar trends were seen for pH < 4.0, 5.5 & 6.0. Low acid exposure ( < 1%) was significantly associated with PPI response when compared to high acid exposure (≥1%) [Figure 2]. PPI responders had higher psychological distress scores prior to treatment and a significantly greater reduction in post-treatment Brief Symptom Index, Negative Affect, and Heartburn Vigilance Scale scores. Baseline and delta GerdQ scores were significantly higher in the PPI responder group.Figure 2Conclusion: Contrary to our hypothesis, low oropharyngeal acid burden was associated with PPI symptom response, suggesting a non-acid mechanism of laryngeal symptoms in this group. PPI responders had higher psychological distress, indicating an association between cognitive affective symptoms and laryngeal complaints and supporting the placebo effect of PPI therapy. The etiology of laryngeal symptoms is undoubtedly complex, and the role of oropharyngeal pH testing to predict PPI response remains unclear.Figure 1

Submental Muscle Activity is Delayed and Shortened During Swallowing Following Stroke

ObjectiveTo evaluate the activities of the submental muscles using surface electromyography (sEMG) in patients presenting with dysphagia secondary to middle cerebral artery (MCA) infarction, and to compare the results with those in healthy volunteers. DesignRetrospective study design. SettingA dysphagia clinic at a tertiary care university hospital. ParticipantsTwenty-one patients presenting with dysphagia after unilateral MCA infarction were recruited into the study within 2 months of stroke onset. To serve as a control group, 13 healthy volunteers were enrolled. Main Outcome MeasuresThe primary sEMG parameters were swallowing onset, pretrigger duration, swallowing duration, and swallowing amplitude. Swallowing functional outcome was evaluated using the Videofluoroscopic Dysphagia Scale and the American Speech-Language-Hearing Association National Outcome Measurement System. ResultsPatients with MCA infarction demonstrated significantly delayed swallowing onset (P < .001) and shorter swallowing duration (P = .003) compared with the controls. Duration from the start of sEMG activity and actual laryngeal elevation also was delayed in the patient group (P = .042). At a cut-off point of 0.13 seconds for swallowing onset, sensitivity was 85.7% and specificity was 69.2%. For swallowing duration, sensitivity was 84.6% and specificity was 66.7% with 1.05 seconds as the cut-off point. ConclusionsPatients with MCA infarction showed not only delayed swallowing onset and pretrigger duration, but also shorter duration of sEMG activity compared with those in healthy volunteers. Our results suggest that dysphagia after stroke might be further compromised by delayed laryngeal response especially after the start of suprahyoid muscle activity, which represents impaired laryngeal protection mechanism.

Laryngeal response patterns to mechanical insufflation–exsufflation in amyotrophic lateral sclerosis

Laryngeal response patterns to mechanical insufflation–exsufflation in amyotrophic lateral sclerosis

Menthol suppresses laryngeal C-fiber hypersensitivity to cigarette smoke in a rat model of gastroesophageal reflux disease: the role of TRPM8.

Patients with gastroesophageal reflux disease (GERD) display enhanced laryngeal reflex reactivity to stimuli that may be due to sensitization of the laryngeal C-fibers by acid and pepsin. Menthol, a ligand of transient receptor potential melastatin-8 (TRPM8), relieves throat irritation. However, the possibility that GERD induces laryngeal C-fiber hypersensitivity to cigarette smoke (CS) and that menthol suppresses this event has not been investigated. We delivered CS into functionally isolated larynxes of 160 anesthetized rats. Laryngeal pH 5-pepsin treatment, but not pH 5-denatured pepsin, augmented the apneic response to CS, which was blocked by denervation or perineural capsaicin treatment (a procedure that blocks the conduction of C fibers) of the superior laryngeal nerves. This augmented apnea was partially attenuated by capsazepine [an transient receptor potential vanilloid 1 (TRPV1) antagonist], SB-366791 (a TRPV1 antagonist), and HC030031 [a transient receptor potential ankyrin 1 (TRPA1) antagonist] and was completely prevented by a combination of TRPV1 and TRPA1 antagonists. Local application of menthol significantly suppressed the augmented apnea and this effect was reversed by pretreatment with AMTB (a TRPM8 antagonist). Our electrophysiological studies consistently revealed that laryngeal pH 5-pepsin treatment increased the sensitivity of laryngeal C-fibers to CS. Likewise, menthol suppressed this laryngeal C-fiber hypersensitivity and its effect could be reversed by pretreatment with AMTB. Our results suggest that laryngeal pH 5-pepsin treatment increases sensitivity to CS of both TRPV1 and TRPA1, which are presumably located at the terminals of laryngeal C-fibers. This sensory sensitization leads to enhanced laryngeal reflex reactivity and augmentation of the laryngeal C-fiber responses to CS, which can be suppressed by menthol acting via TRPM8.

Detection and Characterization of Laryngeal Reflex Pathology in Mouse Models of Human Diseases

Objectives: The laryngeal adductor reflex (LAR) is readily triggered in healthy, awake humans by delivering a puff of air to the laryngeal entrance via an endoscope passed through the nose into the throat. LAR impairment has been identified (but not well-characterized) in people with amyotrophic lateral sclerosis (ALS) and is highly correlated with dysphagia. We propose to develop a nonsurgical approach for longitudinal investigation of the LAR in mice. Methods: We designed and constructed an elaborate prototype air pulse delivery system for use with mice. The system interfaces with a miniature endoscope that is small enough for oral insertion into the laryngeal entrance and contains a working channel through which calibrated puffs of air can be delivered, synchronized with rate and phase of the respiratory cycle. Results: We have successfully used this prototype system to evoke and video record (30 fps) the LAR in 10 healthy, C57BL/6 mice under light anesthesia, thus demonstrating proof of concept. Objective quantification of several LAR parameters is currently underway, including total LAR duration, duration of adduction versus abduction phases, and velocity of dorsal angle adduction and abduction. Conclusions: This study provides novel evidence that mice have an LAR similar to humans and that several parameters of the LAR can be objectively quantified in this small animal model. Additional research will include laryngeal brainstem response (LBR) recordings evoked by air pulse triggering of the LAR to elucidate pathological neural substrates in mouse models of ALS and other human diseases that cause dysphagia.

Laryngeal Response Patterns to Mechanical Insufflation-Exsufflation in Healthy Subjects

Mechanical insufflation-exsufflation (MI-E) is used to assist cough in patients with neuromuscular diseases. Clinically, application may be challenging in some patient groups, possibly related to laryngeal dysfunction. Before launching a study in patients, the authors investigated laryngeal responses to MI-E in healthy individuals. Twenty healthy volunteers, aged 21-29 yrs, were studied with video-recorded flexible transnasal fiber-optic laryngoscopy while performing MI-E using the Cough Assist (Respironics, United States) according to a standardized protocol applying pressures of ±20 to ±50 cm H2O. An initial abduction of the vocal folds was observed in all subjects, both during the insufflation and exsufflation phases. Nineteen of the 20 subjects adequately coordinated glottic closure when instructed to cough. When instructed simply to exhale during exsufflation, the glottis stayed open in a majority. Subsequent to an initial abduction during exsufflation and cough, various obstructive laryngeal movements were observed in some subjects, such as narrowing of the vocal folds, retroflexion of the epiglottis, hypopharyngeal constriction, and backward movement of the base of the tongue. The larynx can be studied with transnasal laryngoscopy during MI-E in healthy individuals. Laryngeal responses to MI-E vary, and laryngoscopy may offer valuable clinical information when applying MI-E in patients with bulbar muscle weakness.

The Role of the Larynx in Chronic Cough

Cough lasting more than 8 weeks is considered chronic. If the classic causes of chronic cough have been discarded, vagus nerve sensory disturbances are currently considered the most important etiological cause. Patients with chronic cough of laryngeal origin have associated symptoms such as globus, dysphagia, dysphonia, dyspnoea and/or stridor. These patients are more likely to have paradoxical vocal fold movement. There is a higher cough reflex sensibility and neuropathic laryngeal response, mainly caused by viral infection or reflux. The cough associated with reflux has 2 mechanisms: Exposure to acid in the distal oesophagus (gastroesophageal reflux) and microaspiration of oesophageal contents into the larynx and tracheo-bronchial tree (pharyngo-laryngeal reflux). Laryngeal neuropathy hypersensitivity responds well to speech therapy as a treatment for refractory chronic cough. Because chronic cough is a sign of laryngeal sensory, neuropathy can improve with neuroleptic drugs such as amitriptyline and gabapentin.

Laryngeal reflex responses in anaesthetised children: breach of international research governance

Laryngeal reflex responses in anaesthetised children: breach of international research governance