Laryngeal Cough Reflex Research Articles

Sensory Changes Related to Swallowing in Motor Neurone Disease.

Dysphagia is common in motor neurone disease (MND) and associated with negative health and psychosocial outcomes. Although largely considered a motor disease, a growing body of evidence suggests that MND can also affect the sensory system. As intact sensation is vital for safe swallowing, and sensory changes can influence the clinical management of dysphagia in people living with MND, this review evaluated and summarised the current evidence for sensory changes related to swallowing in MND. Of 3,481 articles originally identified, 29 met the inclusion criteria. Of these, 20 studies reported sensory changes, which included laryngeal sensation, taste, gag reflex, cough reflex, tongue sensation, smell, palatal and pharyngeal sensation, silent aspiration, and undefined sensation of the swallowing mechanism. Sensory changes were either described as decreased (n = 16) or heightened (n = 4). In the remaining nine studies, sensory function was reported as unaffected. The presence of changes to sensory function related to swallowing in MND remains inconclusive, although an increasing number of studies report sensory changes in some sensory domains. Future research is needed to evaluate the prevalence of sensory changes in MND and how such changes may influence dysphagia and its management.

Neurophysiology of the Superior Laryngeal Nerve in an In Vivo Rat Model.

The superior laryngeal nerve (SLN) is fundamental in laryngeal sensation, cough reflex, and pitch control. SLN injury has substantial consequences including altered sensation, aspiration, and dysphonia. To date, in vivo measurement of the SLN remains elusive. The purpose of this study was to assess the feasibility of recording motor and sensory evoked potentials in a rat SLN model. Twenty-two rat hemi-laryngeal preparations (n = 11) were obtained from 4-month-old Sprague-Dawley rats and included in this study. Compound motor action potentials (CMAPs) and motor unit number estimation (MUNE) were calculated by stimulating the SLN at the point of medial extension near the carotid artery and by placing a recording electrode on the cricothyroid muscle. Sensory response was determined through stimulation of the SLN and laryngoscopic visualization of a laryngeal adductor reflex (LAR). SLN and cricothyroid muscle cross-sections were stained and histologic morphometrics were quantified. Laryngeal evoked potentials were successfully obtained in all trials. Mean CMAP latency and negative durations were 0.99 ± 0.57 ms and 1.49 ± 0.57 ms, respectively. The median MUNE was 2.06 (IQR 1.88, 3.51). LAR was induced with a mean intensity of 0.69 ± 0.20 mV. Mean axon count, myelin thickness, and g-ratio were 681 ± 192.2, 1.72 ± 0.26, and 0.45 ± 0.04, respectively. This study demonstrates the feasibility of recording evoked response potentials following SLN stimulation. We hypothesize that this work will provide a tractable animal model to study changes in laryngeal sensation and cricothyroid motor function with aging, neurodegenerative disease, aspiration, or nerve injury. NA Laryngoscope, 134:1778-1784, 2024.

Infant aspiration and associated signs on clinical feeding evaluation

ObjectivesFew studies have examined clinical signs of aspiration in infants <51 weeks post-menstrual age (PMA) for whom the laryngeal cough reflex is not fully developed. This retrospective study explored 1) the association between signs of aspiration on a clinical feeding evaluation (CFE) and/or comorbid conditions with aspiration (silent or overt) on a modified barium swallow study (MBS) for infants in this age range, 2) the association between lower respiratory infection (LRI) and aspiration on MBS, and 3) the sensitivity and specificity of detecting aspiration according to signs on CFE and the evaluating speech-language pathologist's (SLP) years of experience. MethodsA retrospective review of charts of patients with MBS completed January 1, 2012–December 31, 2014 was performed. Patients were included if they were <51-weeks PMA at the time of MBS and had a CFE conducted no more than seven days prior to the MBS. Patient age, comorbidities, and MBS and CFE details were collected. The impact of CFE findings, patient age, comorbid syndromes/associations, and aerodigestive diagnoses on the odds of demonstrating silent aspiration (SA) or overt aspiration during MBS with thin liquids was determined using logistic regression, and the sensitivity and specificity of CFE for identifying SA was calculated. ResultsResults from 114 patients indicated that 46 (40 %) of the infants had SA and nine (8 %) had overt aspiration on MBS. Notable signs on CFEs were cough (36 %), oxygen desaturations (33 %), and chest congestion (32 %). On multiple regression analysis there was increased odds of SA on MBS with at least one clinical sign on CFE (OR: 24.3, p = 0.02), chronic lung disease, (OR: 18.2, p = 0.01), and airway abnormalities (OR: 2.94, p = 0.01). Cough on CFE was associated with increased odds of overt aspiration on MBS (OR: 5.69, p = 0.04). Neither SA nor overt aspiration were significantly associated with LRI. Sensitivity and specificity of CFE for correctly identifying the presence of SA were 98 % and 15 %, respectively; experience of the SLP was not a contributing factor. ConclusionFurther study is required to determine if specific signs on CFE are predictive of aspiration.

Cough reflex testing in acute stroke: A survey of current UK service provision and speech and language therapist perceptions.

Silent aspiration (SA)-airway entry of food, drink or other material without a cough response-is common post-stroke. Clinical swallowing examination misses up to 40% of dysphagic patients with SA. This may put these patients at risk of aspiration pneumonia, prolonged length of hospital stay and increased healthcare costs. After stroke, the laryngeal cough reflex is frequently impaired with significant relationships between pneumonia rates and reduced cough strength and sensitivity. There has been a significant amount of recent interest in cough reflex testing (CRT) as a potential means to improve clinical identification of patients at risk of SA. However, there is a lack of consensus regarding the methodology and protocols for use of CRT with widely varying outcomes reported in the literature. To provide an overview of current practice in the UK with regards to clinical use of CRT by speech and language therapists (SLTs) in acute stroke settings and to explore the perceptions regarding its potential application in clinical dysphagia management and the barriers and facilitators associated with adopting CRT in clinical practice. A cross-sectional web-based survey was developed, piloted and delivered. The survey targeted all UK-based SLTs working in acute stroke settings. A total of 129 SLTs with varying levels of experience of CRT from all regions of the UK responded. Only four SLT services in the UK were reported to be currently using CRT clinically with acute stroke patients. A total of 29% of respondents who were not using CRT were considering introducing CRT into their service's dysphagia protocol. Variation was reported in the procedures and protocols. Overall, users reported improved confidence in the clinical detection of SA and felt that the introduction of CRT had improved their patient-related outcomes. Issues included difficulties procuring citric acid, implications for SLT time (including service set-up and delivery of CRT) and restricted access to instrumental assessments. This survey gives valuable insight into the current practice and perceptions of SLTs in the UK working in acute stroke settings in relation to CRT. It highlights discrepancies between reported approaches and recommendations from existing guidelines and validation studies. The variation in responses indicates a need to develop a consensus statement and further research to guide practice. What this study adds What is already known on the subject CRT is gaining popularity as a screening tool for the clinical identification of SA with acute stroke patients. However, there is a lack of consensus in the literature regarding the methodology and protocols with widely varying outcomes. Further work needs to be done to standardize its use, especially if it is to be incorporated into dysphagia protocols for use in the acute stroke setting. What this paper adds to existing knowledge This survey of SLTs working in acute stroke settings highlights variability in practice in CRT service delivery in the UK, reflecting findings from the existing CRT literature. What are the potential or actual clinical implications of this work? The findings of this study support the need for further research relating to clinical screening tests for SA and standardization of methodology and protocols for CRT use if its use is to be continued clinically.

Consideration of Cough Reflex Development When Ordering Modified Barium Swallow Studies in Infants.

Infants <51weeks post-menstrual age (<51 PMA) are often referred for modified barium swallow (MBS) studies for suspectedsilent aspiration (SA) given a possible association between SA and aspiration pneumonia. Infants this young are unlikely to have developed a mature laryngeal cough reflex, most likely rendering SA an expected finding in those who aspirate. The aims of this retrospective review were to (1) determine if SA resolves in a significant proportion of infants around the expected emergence of the laryngeal cough reflex, (2) determine which factors or characteristics are associated with and without SA resolution in these infants, and (3) determine if SA, or any aspiration, is associated with increased rates of lower respiratory infection (including aspiration pneumonia) in these infants. Results from the chart review revealed that 79/148 (53.4%) infants had SA on MBS < 51 PMA. 16/48 (33.3%) infants assessed for SA by the time of the expected emergence of the cough reflex had resolution. SA resolution was less common in infants with obstructive sleep apnea (p = 0.037). A total of 50/70 (71.4%) infants with a follow-up MBS had eventual SA resolution. Aspiration was not significantly associated with LRI, including aspiration pneumonia. The results suggested that the laryngeal cough reflex might develop later than reported in the literature and there is no association between aspiration and LRI. These findings may indicate that age should be considered before ordering an MBS solely to assess for SA in this population. The study provides preliminary evidence for future prospective research regarding SA resolution.

Cohort Study on Laryngeal Cough Reflex, Respiratory Disease, and Death: A Mediation Analysis

ObjectiveTo estimate quantitatively whether the presence of cough associated with dysphagia (laryngeal cough reflex) increased mortality through respiratory disease among community-dwelling older Japanese. DesignA 6-year follow-up prospective cohort study (from 2010 to 2017). SettingThirteen municipalities in Japan. ParticipantsCommunity-dwelling individuals aged 65 years or older (N = 32,682). MeasuresThe baseline survey was conducted through self-reported questionnaire. Exposure was experience of laryngeal cough reflex while drinking. The outcome was all-cause mortality. All covariates were selected from demographic, socioeconomic variables, baseline health and functional status, smoking, alcohol drinking, number of remaining teeth, and stroke. The mediator variable was respiratory disease. Cox proportional hazards regression was used to estimate hazard ratios (HRs) for mortality. Parametric mediation analysis was conducted to estimate the effect of laryngeal cough reflex on the mean residual time to death mediated through respiratory disease. ResultsAmong the 32,682 participants (mean age = 74.1 years, standard deviation = 5.9 years), 5550 (17.0%) experienced laryngeal cough reflex at baseline. A total of 4037 deaths occurred. Crude mortality rates of the participants with or without laryngeal cough reflex were 16.3% and 11.6%, respectively. After adjusting for covariates, laryngeal cough reflex [HR = 1.10; 95% confidence interval (CI) = 1.02 to 1.19] and respiratory disease (HR = 1.80; 95% CI = 1.62 to 2.00) were associated with mortality. The mediation analysis showed that respiratory disease significantly (P < .001) and partially mediated the association between laryngeal cough reflex, an indicator of 1 or more conditions such as chronic aspiration and mortality. Conclusions/ImplicationsLaryngeal cough reflex was a prevalent condition, and it was associated with all-cause mortality in community-dwelling older Japanese individuals. Clinicians could contribute to reduce mortality risk by addressing swallowing function problems using their interprofessional collaboration team (speech-language pathologist, dentist, rehabilitation doctor, otolaryngologist, respiratory physician, and gerontologist).

Long-term Swallowing Function, Pulmonary Complications, and Quality of Life after Supracricoid Laryngectomy.

Long-term effects of supracricoid laryngectomies are nowadays under discussion. The purpose of this study was to detect the prevalence of chronic aspiration and incidence of pulmonary complications, to investigate possible influencing factors, and to analyze dysphagia-related quality of life in a cohort of patients who recovered swallowing function after undergoing supracricoid laryngectomies. Retrospective observational study. San Raffaele Hospital, Vita-Salute University, Milan, Italy. A cohort of 39 patients who recovered swallowing function free of disease after a minimum 3-year follow-up period was retrospectively investigated between October and December 2017-clinically with the Pearson's Scale and M. D. Anderson Dysphagia Inventory and instrumentally with fiberoptic endoscopic evaluation of swallowing. Chronic aspiration was demonstrated in a significant portion of patients (clinically in 33.3% and instrumentally in 35.9%). Aspiration was influenced by advanced age at surgery (P = .020). Type of surgical procedure, resection of 1 arytenoid cartilage, postoperative rehabilitation with a speech-language therapist, radiotherapy, age at consultation, and length of follow-up did not influence the prevalence of aspiration. Pulmonary complications affected 5 patients; incidence of pulmonary complications was related to aspiration and was favored by poor laryngeal sensation/cough reflex. Aspiration significantly affected quality of life. Chronic aspiration is frequent and affects patients' quality of life. However, incidence of pulmonary complications is low; therefore, oral feeding should not be contraindicated for aspirating patients. Preservation of laryngeal sensation and cough reflex is mandatory to prevent pulmonary complications.

An arterially perfused brainstem preparation of guinea pig to study central mechanisms of airway defense

The perfused working heart brainstem preparation of rodents has become a widely used tool to study brainstem function. Here, we adapt this experimental technique for newborn guinea pigs (postnatal day 7–14) to develop a tool that enables investigation of airway defense mechanisms not observed in other rodents. The perfused guinea pig brainstem preparation generates a stable eupnea-like motor pattern recorded from the phrenic, recurrent laryngeal and intercostal nerves and basic cardio-respiratory reflexes, including the arterial chemoreceptor, the baroreceptor reflex. In addition a fictive laryngeal cough reflex can be reliably elicited after mechanical stimulation of the trachea. Single unit recordings within the ponto-medullary respiratory column show robust central respiratory neuronal activity. Additionally, as in other species ponto-medullary transection of the brainstem produces apneusis. The latter suggests that the preparation fully preserves ponto-medullary synaptic connectivity that is required for eupnea-like respiratory rhythm and pattern formation and the mediation of various cardio-respiratory reflexes. We conclude that this novel research tool provides an alternative to established rat and mouse preparations and may become a experimental tool for the investigation of central mechanisms that mediate laryngeal cough.

Impact of an education program on the performance of nurses in providing oral care for mechanically ventilated children

BackgroundMechanically ventilated children are prone to pneumonia due to immobilization and lack of laryngeal (cough) reflex and swallowing. Nurses are directly responsible for many clinical approaches used to prevent ventilator-associated pneumonia. ObjectiveThe research objective is to determine the effectiveness of the nurse education program on the performance of nurses in providing oral care for mechanically ventilated children. MethodsThis quasi-experimental pretest-posttest design was conducted on 100 nurses (50 in each of the control and intervention groups) in pediatric intensive care units (PICU) in Tehran, 2015. The research tools included a demographic form and three checklists for evaluation of performance according to the clinical practice guidelines for the oral health status of children in PICU. Before intervention, the performance of nurses in both groups was observed at three stages and three different shifts, using an observational checklist. After one month, their performance was observed again with the same checklist at three stages and three different shifts in the PICU. The training was done in four 40-50 minute sessions in a workshop with a 4-week follow-up. The Chi-square test, Fisher’s exact test, paired t-test, independent t-test, and regression analysis comprised the tools used to analyze the data. FindingsThe mean performance scores of nurses before the education program in the intervention and control groups were 42.8 (±18.5) and 48.7 (±15.7), respectively. These scores improved to 68.6 (±31.4) and 48.6 (±15.4) four weeks after the intervention (p < 0.001). ConclusionThe performance of nurses in providing oral care for mechanically ventilated children improved after the intervention. It is recommended to implement this program for all nurses, regardless of their ward or specialty, based on the clinical practice guidelines. The periodic refreshing in-service training program should be provided to nurses in PICU in order to enhance their performance in providing oral care.

Infection control in cough reflex testing: An equipment-based bacterial contamination study

Cough reflex testing evaluates the sensory integrity of the laryngeal cough reflex and has recently been applied for the evaluation of patients with dysphagia. It involves brief nebulization of citric acid through a sterile reservoir, mask, and tubing which are disposed of after use. Nebulizers used for drug delivery or humidification are reported to become contaminated with bacteria, leading to patient colonization and consequently increasing the risk of chest infection. No research has been undertaken to evaluate whether nebulization used for cough reflex testing poses similar threats. This study analyzed whether pathogens colonize in the disposable products used for cough reflex testing in the short duration of usual clinical practice as a component of the clinical swallowing assessment. Samples taken from both ends of the tubing, the reservoir and the mask, pre- and post-nebulization, were smeared onto blood agar plates, then incubated at 37°C in candle jars. After 48 hours the plates were removed and bacterial colonies were counted. No colonies grew from either end of the tubing for any trial. Evidence of bacterial colonization was found in samples from the reservoir and the mask and single-tailed paired t tests were completed for these datasets. For the reservoir and the mask data, there were no significant differences between pre- and post-nebulization bacteria counts. These results suggested that the clinical methods used for cough reflex testing do not result in significant colonization of bacteria on test materials.

Correlation Between Voluntary Cough and Laryngeal Cough Reflex Flows in Patients With Traumatic Brain Injury

ObjectiveTo correlate voluntary cough and laryngeal cough reflex (LCR) flows in patients with traumatic brain injury (TBI). DesignCross-sectional study. SettingUniversity rehabilitation hospital. ParticipantsPatients with TBI (n=25) and healthy controls (n=48). InterventionsNot applicable. Main Outcome MeasuresPeak cough flows (PCFs) and LCR flows were measured using a peak flow meter at the oral-nasal interface. The largest value of 3 attempts was recorded for PCF and LCR, respectively. LCR was elicited by 20% solution of pharmaceutic-grade citric acid dissolved in sterile .15M NaCl solution that was inhaled from a nebulizer. ResultsPCF was 447.4±99.0L/min in the control group and 211.7±58.2L/min in the patient group. LCR was 209.2±63.8L/min in the control group and 170.0±59.7L/min in the patient group. Both PCF (P=.000) and LCR (P=.013) were significantly reduced in patients with TBI compared to that of the control group. LCR was strongly related to the PCF in both control (R=.645; P=.000) and patient (R=.711; P=.000) groups. ConclusionsAs LCR can be measured as a numerical value and significantly correlates with PCF, LCR can be used to estimate cough ability of patients with TBI who cannot cooperate with PCF measurement.

Bilateral Internal Superior Laryngeal Nerve Palsy of Traumatic Cervical Injury Patient Who Presented as Loss of Cough Reflex after Anterior Cervical Discectomy with Fusion

Injury to the bilateral internal branch of superior laryngeal nerve (ibSLN) brings on an impairment of the laryngeal cough reflex that could potentially result in aspiration pneumonia and other respiratory illnesses. We describe a patient with traumatic cervical injury who underwent bilateral ibSLN palsy after anterior cervical discectomy with fusion (ACDF). An 75-year-old man visited with cervical spine fracture and he underwent ACDF through a right side approach. During the post-operative days, he complained of high pitched tone defect, and occasional coughing during meals. With a suspicion of SLN injury and for the work up for the cause of aspiration, we performed several studies. According to the study results, he was diagnosed as right SLN and left ibSLN palsy. We managed him for protecting from silent aspiration. Swallowing study was repeated and no evidence of aspiration was found. The patient was discharged with incomplete recovery of a high pitched tone and improved state of neurologic status. The SLN is an important structure; therefore, spine surgeons need to be concerned and be cautious about SLN injury during high cervical neck dissection, especially around the level of C3-C4 and a suspicious condition of a contralateral nerve injury.

The Laryngeal Cough Reflex in Congenital Muscular Torticollis

Cinical experience has shown us that some infants with congenital muscular torticollis have a cough reflex while stretching the sternocleidomastoid muscle. The objective of this study is to present a case series with the maneuver inducing the cough reflex and facial color change and to provide the possible mechanism underlying this phenomenon. This is a case series from a prospective cohort. Among 290 children with congenital muscular torticollis who came to a single torticollis clinic from January to December 2008, the children who showed cough reflex were consecutively enrolled. Twenty-four infants (8.28%) showed the cough reflex. The age of first presentation with congenital muscular torticollis was 37.65 +/- 19.60 days old. They showed 57.5 +/- 7.3 degrees of the passive cervical rotation to the congenital muscular torticollis side at the initial visit. The mean thickness of the sternocleidomastoid muscle in those with cough reflex was 13.79 +/- 1.96 mm at the side of congenital muscular torticollis and 5.43 +/- 0.85 mm on the contralateral side. The cough reflex disappeared, and 90 degrees of passive cervical rotation to the congenital muscular torticollis side were regained with stretching exercises and/or surgical release in all 24 children. One of the possible mechanisms for this cough reflex is surmised to be the mechanical irritation of the internal branch of the superior laryngeal nerve during the maneuver, which is one of the branches of the vagus nerve and is responsible for the sensation of the mucous membrane of the larynx. 8.28% of the infants with congenital muscular torticollis showed positive sign of cough reflex and had at least double or more thickness of the sternocleidomastoid muscle compared with that of unaffected sternocleidomastoid muscle and, at the same time, had 60 degrees or less of passive cervical rotation toward the affected side. To the best of our literature review, this laryngeal cough reflex is a new finding that has never been described before. One of the possible mechanisms for this cough reflex is surmised to be the mechanical irritation of the internal branch of the superior laryngeal nerve during the maneuver, which is one of the branches of the vagus nerve, acting as the afferent nerve of laryngeal cough reflex.

Intra-abdominal Pressures during Voluntary and Reflex Cough

BackgroundInvoluntary coughing such as that evoked from the larynx, the laryngeal cough reflex (LCR), triggers a coordinated contraction of the thoracic, abdominal and pelvic muscles, which increases intra-abdominal pressure (IAP), displaces the diaphragm upwards and generates the expiratory force for cough and airway clearance. Changes in the IAP during voluntary cough (VC) and the LCR can be measured via a pressure catheter in the bladder. This study evaluated the physiological characteristics of IAP generated during VC and the LCR including peak and mean pressures and calculations of the area under the curve (AUC) values during the time of the cough event or epoch.MethodsEleven female subjects between the ages of 18 and 75 underwent standard urodynamic assessment with placement of an intravesicular catheter with a fiberoptic strain gauge pressure transducer. The bladder was filled with 200 ml of sterile water and IAP recordings were obtained with VC and the induced reflex cough test (RCT) using nebulized inhaled 20% tartaric acid to induce the LCR. IAP values were used to calculate the area under the curve (AUC) by the numerical integration of intravesicular pressure over time (cm H2O·s).ResultsThe mean (± SEM) AUC values for VC and the LCR were 349.6 ± 55.2 and 986.6 ± 116.8 cm H2O·s (p < 0.01). The mean IAP values were 45.6 ± 4.65 and 44.5 ± 9.31 cm H2O (NS = .052), and the peak IAP values were 139.5 ± 14.2 and 164.9 ± 15.8 cm H2O (p = 0.07) for VC and LCR, respectively.ConclusionThe induced LCR is the involuntary rapid and repeated synchronous expiratory muscle activation that causes and sustains an elevated IAP over time, sufficient for airway protection. VC and LCR have different neurophysiological functions. Quantification of the LCR using AUC values and mean or peak IAP values may be useful as a clinical tool for determining neurophysiological airway protection status and provide a quantitative assessment of changes in a patient's functional recovery or decline.

Surgical anatomy of the internal branch of the superior laryngeal nerve

The internal branch of the superior laryngeal nerve (ibSLN) may be injured during anterior approaches to the cervical spine, resulting in loss of laryngeal cough reflex, and, in turn, the risk of aspiration pneumonia. Such a risk dictates the knowledge regarding anatomical details of this nerve. In this study, 24 ibSLN of 12 formaldehyde fixed adult male cadavers were used. Linear and angular parameters were measured using a Vernier caliper, with a sensitivity of 0.1 mm, and a 1 degrees goniometer. The diameter and the length of the ibSLN were measured as 2.1+/-0.2 mm and 57.2+/-7.7 mm, respectively. The ibSLN originates from the vagus nerve at the C1 level in 5 cases (20.83%), at the C2 level in 14 cases (58.34%), and at the C2-3 intervertebral disc level in 5 cases (20.83%) of the specimens. The distance between the origin of ibSLN and the bifurcation of carotid artery was 35.2+/-12.9 mm. The distance between the ibSLN and midline was 24.2+/-3.3 mm, 20.2+/-3.6 mm, and 15.9+/-4.3 mm at the level of C2-3, C3-4, and at the C4-5 intervertebral disc level, respectively. The angles of ibSLN were mean 19.6+/-2.6 degrees medially with sagittal plane, and 23.6+/-2.6 degrees anteriorly with coronal plane. At the area between the thyroid cartilage and the hyoid bone the ibSLN is the only nerve which traverses lateral to medial. It is accompanied by the superior laryngeal artery, a branch of the superior thyroid artery. The ibSLN is under the risk of injury as a result of cutting or compression of the blades of the retractor at this level. The morphometric data regarding the ibSLN, information regarding the distances between the nerve, and the other consistent structures may help us identify this nerve, and to avoid the nerve injury.

Effect of stroke location on the laryngeal cough reflex and pneumonia risk

BackgroundThe purpose of this study was to evaluate the risk of developing pneumonia in acute stroke patients comparing the early anatomical stroke location and laryngeal cough reflex (LCR) testing.MethodsA prospective study of 818 consecutive acute stroke patients utilizing a reflex cough test (RCT), which assesses the neurological status of the LCR compared to magnetic resonance imaging or computerized tomography for stroke location and subsequent pneumonia outcome. Stroke diagnosis and stroke location were made by a neurologist and clinical radiologist, respectively; both were blinded to the RCT results.ResultsBrainstem (p-value < .007) and cerebral strokes (p-value < .005) correlated with the RCT results and pneumonia outcome. Of the 818 patients, 35 (4.3%) developed pneumonia. Of the 736 (90%) patients who had a normal RCT, 26 (3.5%) developed pneumonia, and of the 82 (10%) patients with an abnormal RCT, 9 (11%) developed pneumonia despite preventive interventions (p-value < .005). The RCT had no serious adverse events.ConclusionThe RCT acted as a reflex hammer or percussor of the LCR and neurological airway protection and indicated pneumonia risk. Despite stroke location, patients may exhibit "brainstem shock," a global neurological condition involving a transient or permanent impairment of respiratory drive, reticular activating system or LCR. Recovery of these functions may indicate emergence from brainstem shock, and help predict morbidity and mortality outcome.

Electrophysiologic latency to the external obliques of the laryngeal cough expiration reflex in humans.

The purpose of this study was to trigger the laryngeal cough expiration reflex using inhaled tartaric acid aerosol and to record the latency between the time of initiation of the laryngeal cough expiration reflex component of the laryngeal cough reflex and the onset of electromyographically recorded responses in the external abdominal oblique in humans. Five male subjects were tested in the seated position, and four latencies were recorded for each subject. The latencies were recorded from laryngeal stimulation to an electromyogram in the muscle belly of the left external abdominal oblique. The time line was activated by a microswitch attached to a breath-activated nebulizer. Data were analyzed using SPSS for mean latency and standard deviation. The mean (standard deviation) latency to the external abdominal oblique muscle was 17.6 +/- 10.6 msec. No adverse events to inhalation were reported. SIn humans, nebulized tartaric acid stimulates primarily rapid adapting receptors in the supraglottic larynx rather than C-fiber receptors. This receptor location in humans evolved neurologically to protect the airway during speech and swallowing, making the laryngeal cough expiration reflex an inseparable component of the laryngeal cough reflex, thus making it clinically significant when assessing airway protection.

Anesthesia of the superior laryngeal nerves and tartaric acid-Induced cough

Objective: The internal branch of the superior laryngeal nerve (ibSLN) conveys impulses for the laryngeal cough reflex, which protects the laryngeal aditus and prevents the development of aspiration pneumonia. The purpose of this study was to determine the effect of bilateral anesthesia of the ibSLN on the cough reflex after inhalation of a nebulized chemoirritant solution of tartaric acid. Design: Prospective, clinical investigation. Setting: Outpatient. Participants: Nine healthy volunteers. Interventions: Bilateral injections of 2% lidocaine solution without epinephrine into the paraglottic space containing the ibSLN. Main Outcome Measures: The tidal volume after inhalation of a nebulized 20% tartaric acid solution and forced vital capacity (FVC) were measured before and after injection. Data were analyzed using the Wilcoxon signed ranks, Mann-Whitney, and sign tests. Results: Complete anesthesia of the ibSLN abolished the laryngeal cough reflex. Postinjection tidal volumes were significantly lower than preinjection volumes ( p < .01). The decrease in tidal volumes for six subjects with complete bilateral anesthesia was significantly larger than the decrease in tidal volumes for three subjects with partial anesthesia ( p < .05). FVC in both the six subjects with complete bilateral anesthesia and the three subjects with partial anesthesia did not significantly change from preinjection to postinjection. None of the subjects in this study had complications or adverse respiratory sequelae. Conclusion: Tartaric acid-induced cough may be useful in assessing the integrity of the laryngeal cough reflex after anesthesia or in patients with neurologic injury who are at risk of developing aspiration pneumonia. It may also be useful in making the decision whether to resume oral feeding.

Assessing the laryngeal cough reflex and the risk of developing pneumonia after stroke

Objective: To determine the effectiveness of a new reflex cough test, using nebulized tartaric acid, in the evaluation of the laryngeal cough reflex and the development of aspiration pneumonia. Study Design: In this two-phase study, the cough test assessed the cough reflex in 161 stroke subjects. Phase 1 was a double-blinded prospective study of 40 subjects scheduled to have both modified barium swallow and the reflex cough test. Phase 1 subjects with an abnormal cough test showed an increased pneumonia incidence, and therefore, phase 2 was not blinded. In phase 2, 121 subjects were evaluated using the cough test; 38 received a modified barium swallow. Test results were compared using the Fisher exact test. Results: A total of 131 subjects from both phases had a normal reflex cough test; none developed pneumonia ( p < .01). Thirty subjects from both phases had abnormal reflex cough test results; 5 developed pneumonia. Modified barium swallow findings did not reliably indicate the risk for developing pneumonia. Specificity of a normal reflex cough test was 100%. Conclusion: The reflex cough test reliably evaluated the laryngeal cough reflex and the associated risk of developing aspiration pneumonia in stroke patients. Testing the laryngeal cough reflex may significantly reduce morbidity, mortality, and costs in stroke patients.

Anatomy of the internal branch of the superior laryngeal nerve.

The purpose of this study was to determine the length and distribution of the branches of the internal branch of the superior laryngeal nerve (ibSLN) and describe the initial afferent pathway for the laryngeal cough reflex (LCR). On 25 sides of 19 cadaver specimens, the ibSLN and its branches were dissected from the greater cornu of the hyoid to the mucosa of the larynx and laryngopharynx. The location of these terminal fibers were confirmed by direct observation and fiberoptic laryngoscopy. In 21 specimens, the ibSLN coursed 6.95+/-3.71 mm before piercing the thyrohyoid membrane and splitting into superior, middle, and inferior rami. Four specimens split proximal to the thyrohyoid membrane. The superior ramus distributed to the mucosa of the piriform recess. In this study the large, middle ramus was a new finding and distributed branches to the mucosa of the vestibule of the larynx, specifically the quadrangular membrane. The length of the ibSLN from the greater cornu to the end of the middle ramus at quadrangular membrane was 28.52+/-4.61 mm. The termination of these fibers were confirmed by observation and direct laryngoscopy. The middle ramus probably conveyed the afferent component of the laryngeal cough reflex. The inferior ramus did not distribute to the vestibular mucosa.