Upper airway function and dysfunction in respiration

The Functional Capacity of the Upper Airway in Older Adults with Chronic Stroke

(1) Background: Older adults with chronic stroke may experience compromised upper airway functions due to stroke-related changes and aging. This study aimed to evaluate the functional capacity of the upper airway in older adults with chronic stroke. (2) Methods: A total of 44 patients (22 in each group) were included in the study. The respiratory assessment involved measuring forced vital capacity, forced expiratory volume in one second, maximum voluntary ventilation, and peak cough flow. The voice assessment recorded intensity, frequency, shimmer, and the harmonics-to-noise ratio during a monologue task. Additionally, the maximum phonation time of /a/ and /s/ was recorded. The swallowing assessment included the Eating Assessment Tool-10 and the Swallowing Quality of Life questionnaire. (3) Results: Significant differences were found in the experimental group compared to the control group in maximum voluntary ventilation (44.59 ± 15.61 vs. 58.50 ± 28.08, p = 0.049) and peak cough flow (173.64 ± 101.09 vs. 291.59 ± 176.58, p = 0.009). Additionally, the experimental group showed poorer results than the control group in monologue intensity (66.60 ± 3.72 vs. 114.72 ± 63.09, p = 0.001), the harmonics-to-noise ratio (9.08 ± 2.06 vs. 10.26 ± 1.59, p = 0.042), and the maximum phonation time of /s/ (4.36 ± 1.67 vs. 8.09 ± 4.07, p < 0.001). Patients with stroke also had significantly lower values for swallowing efficiency and safety compared to the control group (7.05 ± 8.44 vs. 2.23 ± 4.14, p = 0.021) and reported poorer quality of life related to swallowing difficulties (185.50 ± 23.66 vs. 200.32 ± 19.60, p = 0.029). (4) Conclusions: Older adults with chronic stroke exhibited significantly reduced cough strength, voice intensity, maximum phonation time, and swallowing function compared to controls.

Persistent glossopharyngeal nerve respiratory discharge patterns after ponto-medullary transection

Shape and size of the nasopharyngeal airway is controlled by muscles innervated facial, glossopharyngeal, vagal, and hypoglossal cranial nerves. Contrary to brainstem networks that drive facial, vagal and hypoglossal nerve activities (FNA, VNA, HNA) the discharge patterns and origins of glossopharyngeal nerve activity (GPNA) remain poorly investigated. Here, an in situ perfused brainstem preparation (n=19) was used for recordings of GPNA in relation to phrenic (PNA), FNA, VNA and HNA. Brainstem transections were performed (n=10/19) to explore the role of pontomedullary synaptic interactions in generating GPNA. GPNA generally mirrors FNA and HNA discharge patterns and displays pre-inspiratory activity relative to the PNA, followed by robust inspiratory discharge in coincidence with PNA. Postinspiratory (early expiratory) discharge was, contrary to VNA, generally absent in FNA, GPNA or HNA. As described previously FNA and HNA discharge was virtually eliminated after pontomedullary transection while an apneustic inspiratory motor discharge was maintained in PNA, VNA and GPNA. After brainstem transection GPNA displayed an increased tonic activity starting during mid-expiration and thus developed prolonged pre-inspiratory activity compared to control. In conclusion respiratory GPNA reflects FNA and HNA which implies similar function in controlling upper airway patency during breathing. That GPNA preserved its pre-inspiratory/inspiratory discharge pattern in relation PNA after pontomedullary transection suggest that GPNA premotor circuits may have a different anatomical distribution compared HNA and FNA and thus may therefore hold a unique role in preserving airway patency.

A speech therapy treatment protocol for exercise induced laryngeal obstruction

Background

Exercise induced laryngeal obstruction (EILO) is a common cause of exertional breathing problems in young individuals, relevant to 5%-7% of young people. It is caused by paradoxical inspiratory adduction of laryngeal structures and diagnosed by continuous visualization of the larynx during high intensity exercise. Empirical data suggest that EILO consists of different subtypes that require different therapeutic approaches. Currently applied treatment approaches do not rest on randomized controlled trials (RCTs), and thus evidence-based guidelines cannot be established. This protocol describes the speech therapy treatment approach which is applied to EILO patients in a large prospective RCT called HelpILO.

Methods and analysis

Consenting patients consecutively diagnosed with EILO at Haukeland University Hospital are randomized into four treatment arms. Speech therapy is represented in two of these, provided in a structured manner based on general speech therapy principles and abdominal breathing, combined with experience obtained with these patients at our hospital during the last decades. The main outcome measure of HelpILO is changes of laryngoscopically visualized laryngeal adduction, rated at peak exercise before vs. after interventions, using a validated scoring system.

Ethics and dissemination

Despite widespread use of speech therapy in patients with EILO, this approach is insufficiently tested in RCTs, and the study is therefore considered ethically appropriate. The study will provide knowledge listed as a priority in a recent statement issued by major respiratory and laryngological societies and requested by clinicians and researchers engaged in this area. The results will be presented at relevant conferences, patient fora, and media platforms, and published in relevant peer reviewed international journals.

Upper airway assessment and its implications for interventions by respiratory physiotherapists

BACKGROUND

When noninvasive interventions such as chest physiotherapy fail, then more aggressive interventions for airway secretion clearance with nasotracheal airway suctioning may be required. Clinicians however have to insert the nasotracheal suction catheter "blindly" and the success of being able to trigger a cough and pass through the vocal folds with a suction catheter is low.

CASE DESCRIPTION

The patient, a 48-year-old male underwent a heart and lung transplant. Following extubation, the patient developed secretion retention with a weak ineffective cough and swallow and required physiotherapy interventions with frequent "blind" passes of nasotracheal suctioning.

OUTCOMES

The patient required nasotracheal suction with frequent multiple failed attempts before successful passage of the suction catheter to trigger a cough reflex and clear secretions. A combined physiotherapist and speech and language therapist intervention during fiberoptic endoscopic evaluation of swallow (FEES) was recorded to both evaluate swallow and passage of the suction catheter. The video illustrated the successful passage of a suctioning catheter through the vocal folds leading to an effective cough and airway clearance.

DISCUSSION

We present a case report demonstrating that it is feasible to visualize the upper airways during nasotracheal suctioning as an objective means to guide the more accurate successful insertion of the suction catheter past the vocal folds. Rather than "blind" placement of nasotracheal suction catheters visualization using transnasal laryngoscopy should be useful to increase chances of passing through the vocal folds.

The complexity of multidisciplinary respiratory care in amyotrophic lateral sclerosis

Motor neurone disease/amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder with no known cure, where death is usually secondary to progressive respiratory failure. Assisting people with ALS through their disease journey is complex and supported by clinics that provide comprehensive multidisciplinary care (MDC). This review aims to apply both a respiratory and a complexity lens to the key roles and areas of practice within the MDC model in ALS. Models of noninvasive ventilation care, and considerations in the provision of palliative therapy, respiratory support, and speech and language therapy are discussed. The impact on people living with ALS of both inequitable funding models and the complexity of clinical care decisions are illustrated using case vignettes. Considerations of the impact of emerging antisense and gene modifying therapies on MDC challenges are also highlighted. The review seeks to illustrate how MDC members contribute to collective decision-making in ALS, how the sum of the parts is greater than any individual care component or health professional, and that the MDC per se adds value to the person living with ALS. Through this approach we hope to support clinicians to navigate the space between what are minimum, guideline-driven, standards of care and what excellent, person-centred ALS care that fully embraces complexity could be.

Educational aims

To highlight the complexities surrounding respiratory care in ALS.To alert clinicians to the risk that complexity of ALS care may modify the effectiveness of any specific, evidence-based therapy for ALS.To describe the importance of person-centred care and shared decision-making in optimising care in ALS.

Computational analysis of human upper airway aerodynamics

There is a considerable interest in understanding transient human upper airway aerodynamics, especially in view of assessing the effects of various ventilation therapies. Experimental analyses in a patient-specific manner pose challenges as the upper airway consists of a narrow confined region with complex anatomy. Pressure measurements are feasible, but, for example, PIV experiments require special measures to accommodate for the light refraction by the model. Computational fluid dynamics can bridge the gap between limited experimental data and detailed flow features. This work aims to validate the use of combined lattice Boltzmann method and a large eddy scale model for simulating respiration, and to identify clinical features of the flow and show the clinical potential of the method. Airflow was computationally analyzed during a realistic, transient, breathing profile in an upper airway geometry ranging from nose to trachea, and the resulting pressure calculations were compared against in vitro experiments. Simulations were conducted on meshes containing about 1 billion cells to ensure accuracy and to capture intrinsic flow features. Airway pressures obtained from simulations and in vitro experiments are in good agreement both during inhalation and exhalation. High velocity pharyngeal and laryngeal jets and recirculation in the region of the olfactory cleft are observed. Graphical Abstract The Lattice-Boltzmann Method combined with Large Eddy Simulations was used to compute the aerodynamics in a human upper airway geometry. The left side of this graphical abstract shows the velocity and vorticity (middle figure in bottom row, and right figure of the right bottom figure) profiles at peak exhalation. The simulations were validated against experiments on a 3D-print of the geometry (shown in the top figures on the right hand side). The pressure drop (right bottom corner) shows a good agreement between experiments and simulations.

Small Plastics, Big Inflammatory Problems

The immune system is the first defense against potentially dangerous chemicals, infections, and damaged cells. Interactions between immune cells and inflammatory mediators increase the coordinated activation of cross-talking signaling pathways, resulting in an acute response necessary to restore homeostasis but potentially detrimental if uncontrolled and prolonged. Plastic production exceeds million tons per year, becoming a global concern due to the stability of its constituent polymers, low density, which allows them to spread easily, and small size, which prevents proper removal by wastewater treatment plants, promoting environmental accumulation and increasing health threats. The interaction between plastic particles and the immune system is still being investigated, owing to growing evidence of increased risk not only for dietary intake due to its presence in food packaging, drinking water, and even fruits and vegetables, but also to emerging evidence of new intake pathways such as respiratory and cutaneous. We discuss in depth the impact of small plastic particles on the immune response across the body, with a focus on the nervous system and peripheral organs and tissues such as the gastrointestinal, respiratory, lymphatic, cardiovascular, and reproductive systems, as well as the involvement in increased susceptibility to worsening concomitant diseases and future perspectives in the exploration of potential therapeutics.

Biological Models of the Lower Human Airways-Challenges and Special Requirements of Human 3D Barrier Models for Biomedical Research

In our review, we want to summarize the current status of the development of airway models and their application in biomedical research. We start with the very well characterized models composed of cell lines and end with the use of organoids. An important aspect is the function of the mucus as a component of the barrier, especially for infection research. Finally, we will explain the need for a nondestructive characterization of the barrier models using TEER measurements and live cell imaging. Here, organ-on-a-chip technology offers a great opportunity for the culture of complex airway models.

Immune responses to bacterial lung infections and their implications for vaccination

The pulmonary immune system plays a vital role in protecting the delicate structures of gaseous exchange against invasion from bacterial pathogens. With antimicrobial resistance becoming an increasing concern, finding novel strategies to develop vaccines against bacterial lung diseases remains a top priority. In order to do so, a continued expansion of our understanding of the pulmonary immune response is warranted. Whilst some aspects are well characterised, emerging paradigms such as the importance of innate cells and inducible immune structures in mediating protection provide avenues of potential to rethink our approach to vaccine development. In this review, we aim to provide a broad overview of both the innate and adaptive immune mechanisms in place to protect the pulmonary tissue from invading bacterial organisms. We use specific examples from several infection models and human studies to depict the varying functions of the pulmonary immune system that may be manipulated in future vaccine development. Particular emphasis has been placed on emerging themes that are less reviewed and underappreciated in vaccine development studies.

Volumetric Changes in the Upper Airways after Rapid and Slow Maxillary Expansion in Growing Patients: A Case-Control Study

The aim is to evaluate changes in the volume of the upper airways before and after slow maxillary expansion (SME) obtained with the flexible properties of a nickel titanium leaf spring and rapid maxillary expansion (RME) with a conventional Hyrax appliance in growing patients. The records of 1200 orthodontic patients undergoing maxillary expansion from 2018 to 2019 were analyzed; among these pre and post treatment CBCT scans of 22 patients (mean age 8.2 ± 0.6 years old) treated by SME were compared with those obtained from 22 patients (mean age 8.1 ± 0.7 years old) treated by RME banded on the second primary molars. The following inclusion criteria were used: Maxillary transverse constriction, good general health, and no previous orthodontic treatment. Volumes of nasal cavity (NCavV), nasopharynx (NsPxV), and right and left maxillary sinuses (MSV) were calculated with ITK-SNAP. Shapiro–Wilk test revealed a normal distribution of data in each group. Paired t-test was used for within-group comparisons and independent t-test for between-group comparisons. Statistically significant increases occurred in NCavV, NsPxV, and MSVs after treatment with both appliances. No statistically significant difference between the appliances occurred in NCavV, NsPxV, and MSVs. Method error was considered negligible (mean intra-operator and inter-operator intraclass correlation coefficient were 0.928 and 0.911, respectively). It appears that both appliances produce similar effects on the different segments of the upper airway tract.

Effect of inspiration cycle and ventilation rate on heat exchange in human respiratory airways

A transient three dimensional (3D) theoretical axisymmetric model is developed for heat exchange across the human respiratory tract during inspiration phase and applied to study the changes in the airway temperature and velocity profile for varying ventilation rates and inhalation temperatures. A multi-compartment approach is used to study the same to avoid the airway scaling problem from micro to nano scale. This analysis also includes the role of water evaporation in mucus and non perfused tissue layers and the role of capillary bed in thermal variations during respiration. The results of heat transfer in airway and mucus layer depend on the local morphological parameters. The results are compared with the case of hypothetical regular geometry to show the significance of local morphology. The location where the inhaled air gets saturated with the body core temperature is computed to estimate the saturation distance of air. The complete analysis is made for two breathing cycles with different inhalation to exhalation ratios. The results indicate that decreasing the ventilation rate and increasing the respiration cycle can avoid the deep penetration of heat into the tract and consequently tissue thermal injury can be avoided. We have also explained numerically the role of mucus layer in avoiding tissue injury in intra-thoracic airways. We have also observed a significant difference in results for high ventilation rates between the cases of actual (cast replica) and regular airway geometry. The numerical results are in good adjustment with existing experimental data and thus validate our approach.

Evidence-Based Systematic Review: Effects of Speech-Language Pathology Treatment for Individuals With Paradoxical Vocal Fold Motion

PURPOSE

In this article, our goal was to determine the state of the evidence and the effect of speech-language pathology (SLP) treatment for individuals with paradoxical vocal fold motion (PVFM).

METHOD

The American Speech-Language-Hearing Association's National Center for Evidence-Based Practice in Communication Disorders searched 22 electronic databases using key words related to PVFM, speech or voice treatment, and behavioral intervention for articles published through July 2013. Identified articles were systematically evaluated to assess the quality of the evidence using a modification of the American Speech-Language-Hearing Association's critical appraisal scheme.

RESULTS

Sixty-five articles met the search criteria. Only 2 out of the 65 articles were judged to contain adequate evidence to evaluate the effect of SLP treatment for PVFM. All 65 articles exemplify the state of the evidence for SLP treatment for PVFM.

CONCLUSION

The state of the evidence for the use of SLP treatment is in its infancy, with a majority of articles in the exploratory stage of research. Consequently, few clinical implications can be drawn at this time. SLP treatment for PVFM is promising; however, there is clearly a pressing need for systematic experimental studies that involve a control group to further the evidence base.

Vocal cord dysfunction in bronchial asthma. A review article

INTRODUCTION

Vocal cord dysfunction (VCD) is a condition in which the larynx exhibits paradoxical vocal cord adduction during inspiration, resulting in extra-thoracic variable airway obstruction. It has been described as a mimic of asthma, and hence, many patients with VCD are diagnosed as difficult-to-treat asthma and suffer significant morbidity as such.

METHODS

In completing this review we searched the literature using the database from MEDLINE, PubMed, and the Cochrane library using the medical terms "vocal cord/vocal cord dysfunction and asthma".

RESULTS

During the last few decades, many publications have described many conditions that may cause or coexist with VCD. In addition, the association between asthma and VCD was recognized. In this narrative review we provide an overview of the current knowledge about VCD and, in particular its relationship to asthma. We also provide a pragmatic diagnostic algorithm and treatment options based on our collaborative multi-disciplinary management of patients attending a difficult to control asthma clinic.

CONCLUSION

Most VCD patients present with inadequately controlled asthma rather than the typical symptoms described in association with VCD. Careful diagnostic strategy as outlined in this review may be helpful in confirming the diagnosis.

Pathohistological changes of tracheal epithelium in laryngectomized patients

Total laryngectomy results in a permanent disconnection of the upper and lower airways. Thus, the upper airways are bypassed and can no longer condition, humidify, and filter the inhaled air, leading to damage of the tracheobronchial epithelium. There is little scientific information available about the effects of tracheostoma breathing and the degree of mucosal damage in laryngectomized patients. The aims of this study were to determine the histopathologic findings and investigate the potential impact of using a heat and moisture exchanger (HME) on the tracheal epithelium in long-term tracheostomy patients. Tracheal mucosal biopsies were taken from a total of 70 patients. Specimens were stained with hematoxylin and eosin and examined by a light microscope. Normal pseudostratified ciliated columnar epithelium was found in only 9 (12.9%) cases; while, 17 (24.3%) cases had some degree of basal cell hyperplasia. Squamous metaplasia was the most common finding (50%). Pre-invasive lesions (mild and moderate squamous dysplasia) were found in only one patient who used an HME, and in eight (11.4%) non-users. Although the HME cannot completely restore the physiological functions of the upper respiratory track, it delivers a better quality of air to the lower airways and has a positive effect on tracheal mucosa.

Laryngeal response patterns to mechanical insufflation-exsufflation in healthy subjects

OBJECTIVE

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.

DESIGN

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.

RESULTS

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.

CONCLUSIONS

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.

Dynamic upper airway obstruction secondary to severe feline asthma

A 2 yr old castrated male cat presented to an emergency referral facility for several episodes of gagging, nonproductive coughing, and increased respiratory effort. He was diagnosed with inspiratory stridor and referred to another emergency referral practice for further diagnostics. Three separate, sedated oral examinations, nasal computed tomography (CT), rhinoscopic biopsies, and tracheoscopy showed no structural causes for the cat's stridor. An endotracheal wash was consistent with feline asthma. Blood work showed a peripheral eosinophilia and exposure to Dirofilaria immitis (D. immitis). The feline asthma was treated with albuterol, fluticasone, dexamethasone sodium phosphate, and terbutaline. Despite aggressive therapy for feline asthma, the cat had several episodes of severe inspiratory respiratory distress and stridor secondary to an upper airway obstruction. After 3 days of hospitalization, a temporary tracheostomy was performed and no further episodes of respiratory distress were noted. The tracheostomy tube was removed 3 days later, and the cat was discharged on the fourth day. At a 14 mo follow-up examination, the client reported no further episodes of respiratory distress, coughing, or gagging. To the authors' knowledge, this is the first report of dynamic upper airway obstruction secondary to feline asthma.

The importance of side difference in nasal obstruction and rhinomanometry: a retrospective correlation of symptoms and rhinomanometry in 1000 patients

OBJECTIVES

The correlation between subjective and objective outcomes of nasal obstruction is still a matter of controversy. The aim of this study was to determine the minimal level of side difference in nasal airway resistance (NAR measured by Broms'v(2)) between the two nasal cavities, which could be discerned subjectively by the patient on a visual analogue scale (VAS). Nasal airway resistance was calculated from rhinomanometric measurements of nasal airflow and transnasal pressure after decongestion of the nasal mucosa.

DESIGN

A retrospective study.

SETTING

ENT department, Vaxjo Central Hospital, Sweden.

PARTICIPANTS

We studied 1000 active anterior rhinomanometries from patients with nasal obstructions.

MAIN OUTCOME MEASURES

We compared the side difference of nasal airway resistance with the side difference of VAS estimated immediately prior to the rhinomanometry. Each measurement was performed after nasal decongestion.

RESULTS

When the difference in nasal airway resistance between the two nasal cavities was larger than 20° (Broms'v(2)) or R(2) > 0.36 Pa/cm(3) /s, we found a significant correlation between side differences of the objective measurement and the subjective assessment (VAS). With a nasal airway resistance side difference over 20°, an additional 20° difference corresponded to a 0.9 centimetre average VAS change. The more obstructed side of the nose could be determined by VAS in 823 (82.3%) of 1000 patients. Yet, 177 (17.7%) patients had a paradoxical sensation of nasal obstruction with the low resistance side of the nose experienced as the most congested side.

CONCLUSION

A significant correlation between the side differences of nasal airway resistance and VAS can serve as a supplement to rhinoscopy in decisions about nasal surgery. This study also showed that in 17.7% of patients, there was a negative correlation between subjective and objective evaluations of nasal airway resistance. But in this group, the nasal airway resistance side difference was mostly under 20°.

Epiglottic Repositioning Procedure for Supraglottic Stenosis/Collapse

Objectives:

Supraglottic stenosis/collapse is an uncommon condition. It can be difficult to detect and may be a cause of failed decannulation following tracheostomy. We present a novel technique to correct supraglottic stenosis/collapse.

Methods:

We performed a retrospective analysis of the records of patients in whom attempts at decannulation had failed at our center between 2003 and 2007. A subgroup with supraglottic stenosis/collapse with posterior displacement of the base of the epiglottis was identified. Our epiglottic repositioning procedure was performed in these patients. Through an external incision, the epiglottis was divided above the anterior commissure and attached to the superior border of the thyroid cartilage.

Results:

Eight decannulation failures out of 36 attempted decannulations were identified. Three of these 8 cases involved supraglottic stenosis/collapse due to posterior displacement of the base of the epiglottis. Correction of the supraglottic stenosis/collapse led to successful decannulation in all cases.

Conclusions:

Diagnosis-directed laryngoscopy is required to identify this condition. We describe precisely a technique of repositioning the epiglottis to correct supraglottic stenosis/collapse.

Age-related changes in the hyoepiglottic ligament: functional implications based on histopathologic study

PURPOSE

The study aimed to identify age-related changes in the hyoepiglottic ligament associated with function of the epiglottis during swallowing and respiration.

MATERIALS AND METHODS

Normal postmortem laryngeal tissue samples were obtained at autopsy from 20 individuals with no history of laryngeal disease. The subjects were divided into 2 groups: those aged 81-91 years (elderly group, n = 11) and those aged 31-48 years (non-elderly group, n = 9). Specimens were subjected to Elastica van Gieson and hematoxylin-eosin staining, and characteristics of the hyoepiglottic ligament were compared between groups.

RESULTS

The hyoepiglottic ligament extended from the epiglottis to both lingual muscles and the hyoid bone (pars lingualis and pars hyoideus). The numbers of muscle fibers (P < .001), collagenous fibers (P < .01), and elastic fibers (P < .001) were significantly decreased in the elderly group in comparison to those in the non-elderly group.

CONCLUSION

Age-related changes in the hyoepiglottic ligament appear to be associated with aspiration, obstructive sleep apnea syndrome, and acquired laryngomalacia in the elderly.

Surgical options for the treatment of obstructive sleep apnea

Obstructive sleep apnea (OSA) is a prevalent condition characterized by repetitive airway obstruction during sleep with associated increased morbidity and mortality. Although CPAP is the preferred treatment, poor compliance is common. Patients intolerant of conventional OSA medical treatment may benefit from surgical therapy to alleviate pharyngeal obstruction. Case series suggest that maxillomandibular advancement has the highest surgical efficacy (86%) and cure rate (43%). Soft palate surgical techniques are less successful, with uvulopalatopharyngoplasty having an OSA surgical success rate of 50% and cure rate of 16%. Further research is needed to more thoroughly assess clinical outcomes (eg, quality of life, morbidity), better identify key preoperative patient and clinical characteristics that predict success, and confirm long-term effectiveness of surgical modalities to treat OSA.

Maximum opening of the mouth by mouth prop during dental procedures increases the risk of upper airway constriction

From a retrospective evaluation of data on accidents and deaths during dental procedures, it has been shown that several patients who refused dental treatment died of asphyxia during dental procedures. We speculated that forcible maximum opening of the mouth by using a mouth prop triggers this asphyxia by affecting the upper airway. Therefore, we assessed the morphological changes of the upper airway following maximal opening of the mouth. In 13 healthy adult volunteers, the sagittal diameter of the upper airway on lateral cephalogram was measured between the two conditions; closed mouth and maximally open mouth. The dyspnea in each state was evaluated by a visual analog scale. In one subject, a computed tomograph (CT) was taken to assess the three-dimensional changes in the upper airway. A significant difference was detected in the mean sagittal diameter of the upper airway following use of the prop (closed mouth: 18.5 ± 3.8 mm, maximally open mouth: 10.4 ± 3.0 mm). All subjects indicated upper airway constriction and significant dyspnea when their mouth was maximally open. Although a CT scan indicated upper airway constriction when the mouth was maximally open, muscular compensation was admitted. Our results further indicate that the maximal opening of the mouth narrows the upper airway diameter and leads to dyspnea. The use of a prop for the patient who has communication problems or poor neuromuscular function can lead to asphyxia. When the prop is used for patient refusal in dentistry, the respiratory condition should be monitored strictly, and it should be kept in mind that the “sniffing position” is effective for avoiding upper airway constriction. Practitioners should therefore consider applying not only systematic desensitization, but also general anesthesia to the patient who refuses treatment, because the safety of general anesthesia has advanced, and general anesthesia may be safer than the use of a prop and restraints.

Developmental changes in pharyngeal airway depth and hyoid bone position from childhood to young adulthood

OBJECTIVE

(1) To test the hypothesis that there are no developmental changes in the pharyngeal airway depth and hyoid bone position from childhood to adulthood in normal Taiwanese persons, (2) to identify any sexual dimorphism, and (3) to find the predictive value of selective variables for the hyoid bone position.

MATERIALS AND METHODS

Lateral cephalometric radiographs of 239 normal Taiwanese (132 females and 107 males; aged 7-27 years) were separated into three stages according to dental age. Twenty-three linear and 20 angular measurements were made in all subjects. Sexual dimorphism was analyzed by Student's t-test. Analysis of variance was used to compare the three stages in both genders. A stepwise regression analysis was carried out to predict the hyoid bone position. The level of significance for all analyses was set at P < .05.

RESULTS

The pharyngeal airway depth increased from the mixed dentition stage to the permanent dentition stage in both genders. There was sexual dimorphism in the lower pharyngeal airway depth. The hyoid bone position showed an obvious difference in the permanent dentition stages between genders. The vertical position of the hyoid bone was associated with the mandibular morphology and position, but the relationship in males was reversed compared with that in females.

CONCLUSIONS

The hypothesis was rejected. There are developmental changes in the pharyngeal airway depth and hyoid position from childhood to young adulthood. Sexual dimorphism appeared in the lower pharyngeal airway and the direction of change in the vertical position of the hyoid bone.

Clinical assessment of nasal decongestion test by VAS in adolescents

Nasal airflow, as measured by rhinomanometry, is frequently impaired in allergic rhinitis (AR). The decongestion test evaluates whether the application of an intranasal vasoconstrictor drug increases nasal airflow. The aim of this study was to verify the suitability of the use of the visual analogue scales (VAS) as a surrogate for rhinomanometry in the decongestion test assessment in adolescents with atopic rhinitis. Forty adolescents [16 males and 24 females, mean age 15 (s.d. 2) yr] with AR were studied. Nasal symptoms, VAS, rhinomanometry, and nasal decongestion test were assessed in all patients. A significant association was observed between VAS and nasal airflow after performing the decongestion test (Spearman's r is -51.7%, p < 0.001). The associated sensitivity and specificity were 84.8 (95% confidence interval, CI 68.1-94.8) and 85.7 (95% CI 42.2-97.6), respectively. The corresponding area under the receiver operating characteristic (ROC) curve of 0.83 (95% CI 0.67-0.93) indicated a good discriminating ability for the decongestion measured on the VAS scale. In conclusion, the use of VAS appears as clinically relevant, in that it allows, with a fair reliability, to perform the decongestion test in the absence of rhinomanometry.

Ozone-induced Nasal Hyperresponsiveness to Tachykinins in Guinea Pigs

Objective

To assess role of hydroxyl radials in the ozone-induced upper airway hyperresponsiveness to tachykinins.

Methods

A prospective, controlled, animal model (n = 96) was performed. Half of them exposed to air (A-group, placebo) and the other half exposed to 3 ppm ozone (O-group) for 2 h. Two hours post air/ozone exposure, animals were anesthetized and equally randomized to be pretreated with one of the three treatments, including saline vehicle, dimethylthiourea (DMTU; 500 mg/kg m, a hydroxyl radical scavenger), or phosphoramidon (Phos; 2 μg/kg, an inhibitor for neutral endopeptidase). Ten minutes after pretreatment, half of the animals in each group were i.v. injected with capsaicin (2 μg/kg), and the other half were i.v. injected with substance P (10 μg/kg) to produce Evans blue dye extravasation.

Results

Nasal exudative response to capsaicin or substance P in O-group was found to be significantly greater than that in A-group. This ozone-induced nasal airway hyperresponsiveness was largely prevented by DMTU. Phosphoramidon produced a similar nasal airway hyperresponsiveness in the A-group, but failed to alter ozone-induced nasal airway hyperresponsiveness in O-group. In sharp contrast, only substance P, but not capsaicin, produced a laryngeal exudative response in the A-group, which was similar to that in the O-group. The laryngeal exudative response to substance P was not significantly affected by DMTU or Phos.

Conculsion

In the guinea-pig model, hydroxyl radicals play a vital role in the development of ozone-induced nasal airway hyperresponsiveness to tachykinins. It is possibly mediated through the suppressive action of ozone on the tachykinin degradation.

Laryngeal dyskinesia: an under-recognized condition

OBJECTIVE

To perform a review of the epidemiology, pathogenesis, clinical presentation, diagnosis and management of laryngeal dyskinesia.

METHODS

A search of the Medline database from 1966 to 2003 was performed. A manual search was performed of the references of each article.

RESULTS

Laryngeal dyskinesia is a respiratory condition characterized by abnormal vocal cord adduction and airflow limitation at the level of the larynx in the absence of evidence of local organic disease. It typically presents to the ED as wheeze, stridor or apparent upper airway obstruction. It occurs across a wide age range, is more common in females, and is typically associated with a range of underlying psychopathologies. Diagnosis is often delayed and unnecessary emergency treatment such as intubation and tracheostomy is not uncommon. Patients are commonly on high-dose steroids and are frequent users of the health-care system, often over prolonged periods. There are multiple diagnostic features on history and examination, and flexible nasendoscopy of the vocal cords in the ED can be used to confirm the diagnosis. Treatment options in the ED include sedation and use of continuous positive airway pressure. Long-term treatment involves a multidisciplinary approach involving respiratory physicians/ear, nose and throat surgeons, speech therapy and psychiatry.

CONCLUSION

Laryngeal dyskinesia remains an under-appreciated cause of respiratory presentations to the ED. Emergency physicians are ideally placed to make the diagnosis and initiate appropriate referral for specific therapies that have a high level of success.

Paradoxical vocal cord motion--a dangerous imitator of airway emergencies

We report a case of stridor in a 32 year old woman. Initial laryngoscopy demonstrated adduction of the vocal cords on inspiration, which reverted to abduction on induction of general anaesthesia. The airway was structurally normal. The most likely diagnosis was paradoxical vocal cord motion, a condition in which psychological stress can precipitate respiratory symptoms and signs due to involuntary adduction of the vocal cords during inspiration. Its importance to the anaesthetist lies in its ability to masquerade as a serious airway or respiratory condition.

Influences of the breathing route on upper airway dynamics properties in normal awake subjects with constant mouth opening

MB (mouth breathing) promotes the occurrence of sleep-disordered breathing even in non-apnoeic subjects. Considering that MO (mouth opening) contributes to an increase in UA (upper airway) collapsibility independently of MB, the aim of the present study was to assess the influence of breathing route on UA dynamics in the presence of MO. Bilateral anterior magnetic phrenic nerve stimulation was performed 2 s after expiratory onset in 12 healthy male subjects during wakefulness (age, 50±5 years; body mass index, 27.8±2.4 kg/m2) during MB through a mouthpiece and during exclusive NB (nasal breathing) with the same mouthpiece in place. Twitch-induced V̇I (instantaneous flow), Pph and Pes (pharyngeal and oesophageal pressures respectively) were recorded and the corresponding resistances were measured. A polynomial regression model, V̇I=k1Pd+k2Pd2, was used to characterize flow–pressure relationship and to determine the Pd value at which UA collapses. There was no difference in UA dynamic properties between NB and MB when UA collapse occurred above the pharyngeal catheter. For twitches where UA collapse occurred lower in the UA, pharyngeal resistance decreased from NB to MB (2.0±0.3 and 1.5±0.2 cmH2O·l−1·s respectively; P=0.02; values are means±S.D.), whereas closing pressure increased (−25.7±10.1 and −18.0±3.0 cmH2O respectively; P=0.04). We conclude that (i) in the presence of MO the dynamic properties of the proximal UA free of phasic activity do not differ between NB and MB, and (ii) MB decreases the upstream resistance and increases collapsibility of the distal UA.

Role of nitric oxide in capillary perfusion and oxygen delivery regulation during systemic hypoxia

The role of nitric oxide (NO) and reactive oxygen species (ROS) in regulating capillary perfusion was studied in the hamster cheek pouch model during normoxia and after 20 min of exposure to 10% O2-90% N2. We measured PO2 by using phosphorescence quenching microscopy and ROS production in systemic blood. Identical experiments were performed after treatment with the NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) and after the reinfusion of the NO donor 2,2'-(hydroxynitrosohydrazono)bis-etanamine (DETA/NO) after treatment with L-NMMA. Hypoxia caused a significant decrease in the systemic PO2. During normoxia, arteriolar intravascular PO2 decreased progressively from 47.0 +/- 3.5 mmHg in the larger arterioles to 28.0 +/- 2.5 mmHg in the terminal arterioles; conversely, intravascular PO2 was 7-14 mmHg and approximately uniform in all arterioles. Tissue PO2 was 85% of baseline. Hypoxia significantly dilated arterioles, reduced blood flow, and increased capillary perfusion (15%) and ROS (72%) relative to baseline. Administration of L-NMMA during hypoxia further reduced capillary perfusion to 47% of baseline and increased ROS to 34% of baseline, both changes being significant. Tissue PO2 was reduced by 33% versus the hypoxic group. Administration of DETA/NO after L-NMMA caused vasodilation, normalized ROS, and increased capillary perfusion and tissue PO2. These results indicate that during normoxia, oxygen is supplied to the tissue mostly by the arterioles, whereas in hypoxia, oxygen is supplied to tissue by capillaries by a NO concentration-dependent mechanism that controls capillary perfusion and tissue PO2, involving capillary endothelial cell responses to the decrease in lipid peroxide formation controlled by NO availability during low PO2 conditions.

Severe upper airway obstruction during sleep

Few disorders may manifest with predominantly sleep-related obstructive breathing. Obstructive sleep apnea (OSA) is a common disorder, varies in severity and is associated with significant cardiovascular and neurocognitive morbidity. It is estimated that between 8 and 18 million people in the United States have at least mild OSA. Although the exact mechanism of OSA is not well-delineated, multiple factors contribute to the development of upper airway obstruction and include anatomic, mechanical, neurologic, and inflammatory changes in the pharynx. OSA may occur concomitantly with asthma. Approximately 74% of asthmatics experience nocturnal symptoms of airflow obstruction secondary to reactive airways disease. Similar cytokine, chemokine, and histologic changes are seen in both disorders. Sleep deprivation, chronic upper airway edema, and inflammation associated with OSA may further exacerbate nocturnal asthma symptoms. Allergic rhinitis may contribute to both OSA and asthma. Continuous positive airway pressure (CPAP) is the gold standard treatment for OSA. Treatment with CPAP therapy has also been shown to improve both daytime and nighttime peak expiratory flow rates in patients with concomitant OSA and asthma. It is important for allergists to be aware of how OSA may complicate diagnosis and treatment of asthma and allergic rhinitis. A thorough sleep history and high clinical suspicion for OSA is indicated, particularly in asthma patients who are refractory to standard medication treatments.

Oral and pharyngeal reflexes in the mammalian nervous system: their diverse range in complexity and the pivotal role of the tongue

The oral cavity and pharynx are anatomically separate but functionally integrated regions of the head. The two regions are involved in complex motor responses that include feeding, chewing, swallowing, speech, and respiration. The multiple sensory receptors that innervate these two regions provide the first link in reflexes that control muscles of the entire head, upper gastrointestinal tract, and airway. Most of the reflexes affect the diversity of muscles that compose the tongue, which is vital to all stages of feeding and which continually affects the patency of the airway. Oral-pharyngeal reflexes are evident in the mammalian fetus and continually emerge as the animal or human matures. Some of the first reflexes in the oral region are geared toward nourishment. As the central nervous system matures and the oral and pharyngeal regions develop morphologically, new reflexes develop. Many of these reflexes are protective both of the tissue in the oral cavity, such as the tongue, and of the upper airway in preventing aspiration. While simple reflexes can be evoked in isolation, most reflexes combine with more complex oral and pharyngeal responses such as chewing and vocalization. Oral-pharyngeal reflexes demonstrate a range in complexity. Some sensory stimuli will evoke a series of responses, as is often evident in the infant, and other stimuli will evoke a complex multiple-level recruitment of muscles in a sequence, as in pharyngeal swallowing. Certain sensory inputs evoke an entire motor behavior pattern, such as taste avoidance or facial expression. The oral-pharyngeal reflexes are critical to maintaining life and ultimately serve functions that the oral and pharyngeal regions have in common, such as communication, feeding, and breathing.

Obstructive sleep apnea in the adult obese patient: implications for airway management

Adult obese patients with suspected or sleep test confirmed OSA present a formidable challenge throughout the perioperative period. Life-threatening problems can arise with respect to tracheal intubation, tracheal extubation, and providing satisfactory postoperative analgesia. Tracheal intubation and extubation decisions in obese patients with either a presumptive and/or sleep study diagnosis of OSA must be made within the context that there may be excess pharyngeal tissue that cannot be visualized by routine examination, and the literature indicates an increased risk of intubation difficulty. Regional anesthesia for postoperative pain control is desirable (although such management is not necessary or possible for many of these patients). If opioids are used for the extubated postoperative patient, then one must keep in mind an increased risk of pharyngeal collapse and consider the need for continuous visual and electronic monitoring. The exact management of each sleep apnea patient with regard to intubation, extubation, and pain control requires judgment and is a function of many anesthesia, medical, and surgical considerations.

Neural control of tongue movement with respect to respiration and swallowing

The tongue must move with remarkable speed and precision between multiple orofacial motor behaviors that are executed virtually simultaneously. Our present understanding of these highly integrated relationships has been limited by their complexity. Recent research indicates that the tongue s contribution to complex orofacial movements is much greater than previously thought. The purpose of this paper is to review the neural control of tongue movement and relate it to complex orofacial behaviors. Particular attention will be given to the interaction of tongue movement with respiration and swallowing, because the morbidity and mortality associated with these relationships make this a primary focus of many current investigations. This review will begin with a discussion of peripheral tongue muscle and nerve physiology that will include new data on tongue contractile properties. Other relevant peripheral oral cavity and oropharyngeal neurophysiology will also be discussed. Much of the review will focus on brainstem control of tongue movement and modulation by neurons that control swallowing and respiration, because it is in the brainstem that orofacial motor behaviors sort themselves out from their common peripheral structures. There is abundant evidence indicating that the neural control of protrusive tongue movement by motoneurons in the ventral hypoglossal nucleus is modulated by respiratory neurons that control inspiratory drive. Yet, little is known of hypoglossal motoneuron modulation by neurons controlling swallowing or other complex movements. There is evidence, however, suggesting that functional segregation of respiration and swallowing within the brainstem is reflected in somatotopy within the hypoglossal nucleus. Also, subtle changes in the neural control of tongue movement may signal the transition between respiration and swallowing. The final section of this review will focus on the cortical integration of tongue movement with complex orofacial movements. This section will conclude with a discussion of the functional and clinical significance of cortical control with respect to recent advances in our understanding of the peripheral and brainstem physiology of tongue movement.

Obstructive sleep apnea in the adult obese patient: implications for airway management

Obstructive sleep apnea in the adult obese patient may be due, in part, to an increased amount of pharyngeal tissue. Therefore, there is an increased risk of intubation and extubation difficulties and pain management can be expected to be complicated by opioid/sedative-induced pharyngeal collapse.

Flow-volume curve changes in patients with obstructive sleep apnoea and brief upper airway dysfunction

OBJECTIVE

Patients with obstructive sleep apnoea (OSA) and those with brief upper airway dysfunction (BUAD) have been reported to have abnormalities of maximal flow-volume curves. This study was designed to assess the ability of flow-volume curves to predict the presence of OSA or BUAD.

METHODOLOGY

Four maximal flow-volume manoeuvres performed by 33 OSA patients and 16 BUAD patients were compared with those of 36 normal subjects. Flow-volume indices, their variability, saw-toothing in the curve and an algorithm based on the flow ratios and shape of the curves were assessed.

RESULTS

When the confounding factors, body mass index (BMI), age, gender and smoking status were taken into account, there was no significant difference in a variety of indices derived from the flow-volume curves between OSA and normal subjects. No BUAD patient had normal flow-volume curves as determined with the algorithm. After BMI, age, gender and smoking status were accounted for, decreased forced expiratory volume in 1 s (FEV1), and increased variability of peak expiratory flow (PEF)/peak inspiratory flow (PIF) and FEV1/PEF remained significantly associated with BUAD.

CONCLUSIONS

These findings suggest that flow-volume curve indices have no value in predicting OSA. Some abnormalities are found in patients with BUAD; a normal flow-volume curve makes the diagnosis of BUAD unlikely.