Airway Anatomy Research Articles

The role of neuromuscular function in sleep apnea pathogenesis and management: A consensus of experts

Study objectivesAlthough the importance of upper airway assessment in the consideration of obstructive sleep apnea (OSA) is recognized, there are current limitations in our approach to assessment.MethodsWe convened a group of experts in upper airway neuromuscular physiology and anatomy, sleep apnea endophenotypes, novel therapeutics and sleep epidemiology to summarize existing literature and delineate future opportunities to utilize and incorporate innovative and less invasive techniques focused on upper airway neuromuscular physiology to assess and manage OSA.ResultsIn OSA, genioglossus electromyogram (EMG) activity is reduced during sleep onset with higher levels observed during wakefulness compared to controls. Surface EMG recordings are limited due to distance from the actual muscle and while needle EMG offers more direct assessment, this approach is more invasive. Novel alternatives overcoming these limitations to assess upper airway neuromuscular physiology in OSA may therefore prove beneficial. Specifically, such an approach would facilitate identification of upstream prognostic biomarkers of OSA clinical trajectory and offer more informative mechanistic data. Novel approaches to neuromuscular assessment in OSA would enhance phenotyping to predict better tolerance to positive airway pressure therapy and set the stage to target neuromuscular function and upper airway anatomy. A quantifiable and repeatable neuromuscular physiologic metric has potential to facilitate a precision medicine strategy and personalize treatment, including measuring treatment response to neurophysiologic-focused interventions including hypoglossal nerve stimulation (HGNS), myofunctional therapy and neuromuscular electrical stimulation. A key area for future investigation is whether observed neuromuscular changes can identify patients at future risk of OSA, facilitating early intervention or prevention strategies.ConclusionsOverall, recognizing the critical contributions of abnormalities of upper airway neuromuscular function to the pathophysiology of OSA, it may be important to find accurate and reproducible neurophysiological assessments to address existing knowledge gaps in OSA assessment and management.

Direct Visualization and Quantitative Imaging of Small Airway Anatomy In Vivo Using Deep Learning Assisted Diffractive OCT.

In vivo imaging and quantification of the microstructures of small airways in three dimensions (3D) allows a better understanding and management of airway diseases, such as asthma and chronic obstructive pulmonary disease (COPD). At present, the resolution and contrast of the currently available conventional optical coherence tomography (OCT) imaging technologies operating at 1300 nm remain challenging to directly visualize the fine microstructures of small airways in vivo. We developed an ultrahigh-resolution diffractive endoscopic OCT at 800 nm to afford a resolving power of 1.7 µm (in tissue) with an improved contrast and a custom deep residual learning based image segmentation framework to perform accurate and automated 3D quantification of airway anatomy. The 800-nm diffractive OCT enabled the direct delineation of the structural components in the small airway wall in vivo. We further first demonstrated the 3D anatomic quantification of critical tissue compartments of small airways in sheep using the automated segmentation method. The deep learning assisted diffractive OCT provides a unique ability to access the small airways, directly visualize and quantify the important tissue compartments, such as airway smooth muscle, in the airway wall in vivo in 3D. These pilot results suggest a potential technology for calculating volumetric measurements of small airways in patients in vivo.

Postextubation stridor in paediatric cardiac surgery patients

Background: Paediatric patients undergoing cardiac surgery are likely to be prone to developing postextubation stridor (PES) due to their airway anatomy and several factors related to surgery, Aim: To examine the incidence and risk factors for PES in paediatric patients undergoing cardiac surgery. Methods: The study was prospectively conducted in the paediatric cardiac postsurgical ICU (PICU) at a tertiary referral hospital from November 2010 to January 2012. All paediatric patients presenting with immediate stridor or its developing within 24 hours after extubation were included. Only those patients who were ventilated for at least 6 hours after surgery, but not more than 7 days and deemed fit for elective extubation were considered. Results: Of the 1328 patients admitted to the PICU, 29 patients (2.18%) met the criteria for PES. Of these, 22 (75.6%) were < 1 year old. Ten patients (34%) did not respond to conservative approach or Noninvasive Ventilation (NIV) and had to be reintubated. Six patients were reintubated within an hour, three in < 6 hours and one after 12 hours of extubation. Conclusion: PES is common in paediatric postcardiac surgical patients. Infants are more prone to develop PES. Majority of them can be successfully managed with conservative measures and noninvasive ventilation. The onset of PES varies from immediately after extubation to 3 hours after extubation. Up to one-third of the patients with PES may require reintubation and is common in the first hour after extubation. Patients who develop PES need close observation in the first few hours after extubation.

Newer techniques of humidification and secretion clearance

This paper begins with a review of airway anatomy, physiology of airway secretions, alterations in disease, and the importance of the mucociliary escalator, especially in airway disease states (asthma, COPD, cystic fibrosis, bronchiectasis etc). Alternatives to treating mild to moderate hypoxemia with high flow nasal cannula oxygen (HFNCO) such as Vapotherm are mentioned. A relatively new technique called Intrapulmonary Percussive Ventilation (IPV®) seems very effective in secretion removal. A newer device called CoughAssist™ assists cough by mechanical insufflation-exsufflation and is very useful in neurological disease. The review then focuses on High Frequency Percussive Ventilation (HFPV), otherwise known as Volumetric Diffusive Ventilation (VDR®). Lastly, the use of biphasic cuirass ventilation for secretion removal has been described.

Difficult airway in intensive care unit

Airway management in critically ill patients is often difficult and is associated with complications. Knowledge of airway anatomy, its change during laryngoscopy and physiology of oxygen transport is essential for predicting difficult airway and in planning the management. Optimal assessment of the airway anatomy to predict difficulty, formulating a plan of action, and an alternate plan, assembling the required equipment and personnel, keeping the difficult airway trolley ready, preparation of the patient by preoxygenation and proper positioning are some of the measures to decrease complications. Adequate training to develop cognitive and procedural skill for managing difficult airway is very important. All physicians involved in airway management should update their skills by involving in simulation excercises and workshops

Airway anomalies in patients with 22q11.2 deletion syndrome: A scoping review.

People with 22q11.2 deletion syndrome (22q11DS) can present with a wide variety of findings. Various airway anomalies have been described intermittently within this syndrome, but this feature has not been extensively investigated. Increased provider awareness of these findings may help guide clinical decision-making and improve overall patient outcomes. The objectives of this review are to identify the types of airway anomalies in 22q11DS and the prevalence of airway anomalies within symptomatic individuals. PubMed/MEDLINE, Cochrane Library, and EMBASE databases were searched in February 2022 for all available articles. Search terms included those that described 22q11DS or one of its synonymous conditions AND those that described airway anatomy and anomalies. The term airway anomaly was defined as any structural aberration in the conductive airway from the oral or nasal vestibule region to the mainstem bronchus. Studies were screened by two authors. A review of references was conducted. Eligible manuscripts underwent full-text review for quality appraisal and data extraction. From a total of 909 unique manuscripts, 58 studies were selected, describing 328 people. The prevalence of airway anomaly diagnosis within symptomatic individuals ranged from 14% to 74%. Twenty-two unique airway anomalies were described. Laryngeal web was the most frequently described anomaly, followed by airway malacia and subglottic stenosis. Laryngeal web was 40% sensitive for suggesting a diagnosis of 22q11DS. Among affected individuals, as many as 46% had multiple concomitant airway anomalies. Aside from respiratory symptoms, other features that prompted airway evaluation included difficult intubation or failed extubation. The findings within this review support the notion that a wide variety of airway anomalies may be seen in people with 22q11DS and that these findings have been discovered frequently in those with airway symptoms. Providers should maintain a low threshold to perform an airway examination in those with 22q11DS, especially when airway symptoms are present.

Current challenges faced by transgender and gender-diverse patients and providers in anesthesiology.

Current challenges faced by transgender and gender-diverse patients and providers in anesthesiology.

In-silico decongested trial effects on the impaired breathing function of a bulldog suffering from severe brachycephalic obstructive airway syndrome

Background and objectiveBrachycephalic obstructive airway syndrome (BOAS) susceptible dogs (e.g., French bulldog), suffer health complications related to deficient breathing primarily due to anatomical airway geometry. Surgical interventions are known to provide acceptable functional and cosmetic results; however, the long-term post-surgery outcome is not well known. In silico analysis provides an objective measure to quantify the respiratory function in postoperative dogs which is critical for successful long-term outcomes. A virtual surgery to open the airway can explore the ability for improved breathing in an obstructed airway of a patient dog, thus supporting surgeons in pre-surgery planning using computational fluid dynamics. MethodsIn this study five surgical interventions were generated with a gradual increment of decongested levels in a bulldog based on computed tomography images. The effects of the decongested airways on the breathing function of a patient bulldog, i.e., airflow characteristics, pressure drop, wall shear stress, and air-conditioning capacity, were quantified by benchmarking against a clinically healthy bulldog using computational fluid dynamics (CFD) method. ResultsOur findings demonstrated a promising decrease in excessive airstream velocity, pressure drop, and wall shear stress in virtual surgical scenarios, while constantly preserving adequate air-conditioning efficiency. A linear fit curve was proposed to correlate the reduction in the pressure drop and decongested level. ConclusionsThe in silico analysis is a viable tool providing visual and quantitative insight into new unexplored surgical techniques.

Transnasal Humidified Rapid-Insufflation Ventilatory Exchange for Difficult Airway Management in Adults With Recessive Dystrophic Epidermolysis Bullosa: A Case Series.

Airway management of adult patients with recessive dystrophic epidermolysis bullosa presents significant challenges associated with tissue fragility and distortion of airway anatomy. This retrospective case series describes 11 adult patients with recessive dystrophic epidermolysis bullosa and difficult airways undergoing 24 general anesthetics in which transnasal humidified rapid-insufflation ventilatory exchange was used for preoxygenation and apneic oxygenation. Despite an average time to intubation of over 6 minutes, transnasal humidified rapid-insufflation ventilatory exchange provided oxygenation before endotracheal intubation without the need for bag-mask ventilation or supraglottic airway ventilation, facilitating smooth and atraumatic flexible scope intubation. There were no major adverse events.

Ultrasound measurements for evaluation of changes in upper airway during anaesthesia induction and prediction difficult laryngoscopy: a prospective observational study

Upper airway collapsibility after anaesthesia induction may be associated with unpredictable difficult airway. However, most works on airway anatomy are tended to morphological description before anaesthesia. This study aimed to evaluate the changes of upper airway after anaesthesia induction and using pre-anesthetic ultrasound measurements to predict Difficult Laryngoscopy (DL). We included 104 eligible subjects with complete data, who were performed tracheal intubations under general anaesthesia in the study. The upper airway changes before and after anaesthesia induction were determined by seven neck ultrasound measurements, included as follow: (1) Distance from skin to under surface of Tongue (DT), (2) Thickness of the thickest part of Tongue body (TT), (3) Hyoid Mental Distance (HMD), (4) Depth of Hyoid (DH), (5) Width of Hyoid (WH), (6) Distance from Skin to Epiglottis (DSE), (7) Depth of the anterior combination of the Vocal Cords (DVC). DL was evaluated with Cormack–Lehane (CL). Data regarding HMD [from 45.3 (42.4–48.5) to 41.1 (38.5–44.9) mm], DH [from 8.7 (6.6–10.9) to 7.0 (5.3–9.1) mm], DSE [from 20.1 (16.6–22.5) to 19.5 (16.5–21.6) mm] and the DVC [from 7.1 (5.7–8.3) to 6.8 (5.7–7.9) mm] were decreased (P < 0.05), while the DT [from 15.9 (13.1–18.4) to 17.4 (14.5–19.8) mm] was increased (P > 0.05) after anaesthesia induction. Additionally, when cut-off value of DSE was 21.25 mm before anaesthesia, it may be better predicted to DL [sensitivity 80.0% (95% CI: 60.7–91.6%) and specificity 83.8% (95% CI: 73.0–91.0%)]. The upper airway after induction showed the propensity of collapsibility by ultrasound measurements. Compared with other indicators, the DSE assessed by ultrasound might be considered to a valuable predictor of DL.Trial registration: The study was registered in ClinicalTrials.gov on 23th Jan 2019, ChiCTR1900021123.

Anatomical investigations on the upper airway in premature and newborn babies.

Safe intubation of newborns remains a challenge. This investigates the upper airway anatomy of (pre-)term infants was investigated to improve airway management and the development of airway devices. Angles and diameters of both oral and nasal intubation pathways of 22 cadavers of premature and term stillborn infants were measured, relative to their gestational age (GA) and tested for statistical significance. The systematic influence of sex on the distribution of values was examined. Cast models of the oral and nasal intubation pathway were (produced using a silicone dental impression material) 3D-scanned. No significant correlation with GA was seen in the angles studied. However, four distances around the hard and soft palate did show statistically significant positive correlations with GA. Regarding differences between the sexes, only the angle between the entrance of the trachea and the esophagus was greater for male cadavers. The angles of the ventilation pathway of (pre-)term infants do not depend systematically on GA. Anatomically, laryngeal masks might therefore also be well-suited ventilators for preterm infants. Alterations in the size but not the shape of laryngeal masks for small preterm infants is recommended. The data obtained may thus be used as a basis for the development of airway devices and airway simulators for medical education and clinical training.

The value of multiparameter combinations for predicting difficult airways by ultrasound

BackgroundBased on the upper airway anatomy and joint function parameters examined by ultrasound, a multiparameter ultrasound model for difficult airway assessment (ultrasound model) was established, and we evaluated its ability to predict difficult airways.MethodsA prospective case-cohort study of difficult airway prediction in adult patients undergoing elective surgery with endotracheal intubation under general anesthesia, and ultrasound phantom examination for difficult airway assessment before anesthesia, including hyomental distance, tongue thickness, mandibular condylar mobility, mouth opening, thyromental distance, and modified Mallampati tests, was performed. Receiver operating characteristic (ROC) curve analysis was used to evaluate the effectiveness of the ultrasound model and conventional airway assessment methods in predicting difficult airways.ResultsWe successfully enrolled 1000 patients, including 51 with difficult laryngoscopy (DL) and 26 with difficult tracheal intubation (DTI). The area under the ROC curve (AUC) for the ultrasound model to predict DL was 0.84 (95% confidence interval [CI]: 0.82–0.87), and the sensitivity and specificity were 0.75 (95% CI: 0.60–0.86) and 0.82 (95% CI: 0.79–0.84), respectively. The AUC for predicting DTI was 0.89 (95% CI: 0.87–0.91), and the sensitivity and specificity were 0.85 (95% CI: 0.65–0.96) and 0.81 (95% CI: 0.78–0.83), respectively. Compared with mouth opening, thyromental distance, and modified Mallampati tests, the ultrasound model predicted a greater AUC for DL (P < 0.05). Compared with mouth opening and modified Mallampati tests, the ultrasound model predicted a greater AUC for DTI (P < 0.05).ConclusionsThe ultrasound model has good predictive performance for difficult airways.Trial registrationThis study is registered on chictr.org.cn (ChiCTR-ROC-17013258); principal investigator: Jianling Xu; registration date: 06/11/2017).

31EMF Intubatable 3D Printed Airway Manikin: A Feasibility Study for Replicating Real Patient Anatomy

31EMF Intubatable 3D Printed Airway Manikin: A Feasibility Study for Replicating Real Patient Anatomy

Initiatives for Early Medical Student Engagement with the Field of Otolaryngology - Head and Neck Surgery.

Early exposure and mentorship in surgical specialties like otolaryngology - head and neck surgery are critical for medical students. This paper presents initiatives implemented at our institution to engage early-career medical students with the field. A hands-on laryngoscope workshop was organised, and a centralised online platform was created for research and mentorship opportunities using a collaborative project management tool. Both measures were advertised via e-mail to student interest groups and campus diversity groups. At the end of the workshop, participating students completed an online distributed survey. Students' perception of their knowledge of airway anatomy and related clinical scenarios significantly improved after the laryngoscopy workshop (p = 0.001 and p = 0.002, respectively). All attendees indicated that the workshop increased their comfort level with procedures and that they would recommend the workshop to colleagues. Nearly half of participants reported becoming 'very interested' in exploring otolaryngology - head and neck surgery through future elective courses. Implementation of such initiatives at other institutions can generate medical student interest and may improve diversity in otolaryngology - head and neck surgery.

Computational assessment of upper airway muscular activity in obstructive sleep apnea – In vitro validation

Neuromuscular control of the upper airway contributes to obstructive sleep apnea (OSA). An accurate, non-invasive method to assess neuromuscular function is needed to improve surgical treatment outcomes. Currently, surgical approaches for OSA are based on airway anatomy and are often not curative. When the airway surface moves, the power transferred between air in the airway lumen and the structures of the upper airway may be a measure of airway neuromuscular activity. The aim of this study was to validate power transfer as a measure of externally applied forces, representing neuromuscular activity, through cine computed tomography (CT) imaging and computational fluid dynamics (CFD) analysis in a 3D-printed airway model. A hollow elastic airway model was manufactured. An insufflation/exsufflation device generated airflow within the model lumen. The model was contained in an airtight chamber that could be positively or negatively pressurized to represent muscular forces. These forces were systematically applied to dilate and collapse the model. Cine CT imaging captured airway wall movement during respiratory cycles with and without externally applied forces. Power transfer was calculated from the product of wall movement and internal aerodynamic pressure forces using CFD simulations. Cross-correlation peaks between power transfer and changes in externally applied pressure during exhalation and inhalation were −0.79 and 0.95, respectively. Power transfer calculated via cine CT imaging and CFD was an accurate surrogate measure of externally applied forces representing airway muscular activity. In the future, power transfer may be used in clinical practice to phenotype patients with OSA and select personalized therapies.

Utilization of submandibular ultrasound in assessing upper airway changes following the administration of propofol.

Our study aimed to use submandibular ultrasound to measure upper airway parameters before and after induction dose of propofol in order to further understand upper airway changes that occur during induction of anesthesia. Measuring the changes that occur in airway anatomy due to the hypotonic effects of induction agents will allow for a deeper understanding of airway management. We enrolled 39 patients between November 2021 and January 2022. Submandibular ultrasound was used to measure tongue thickness, geniohyoid muscle thickness, the distance between the lingual arteries (DLA), lateral pharyngeal wall thickness, and hyomental distance before and after administration of induction doses of the commonly used, sedative-hypnotic agent, propofol. The mean DLA increased significantly after propofol administration, from 3.62 ± 0.63 cm to 3.79 ± 0.56 cm (P < 0.001). The mean tongue thickness was 4.89 ± 0.51 cm and decreased significantly to a mean of 4.62 ± 0.50 cm after propofol administration (P < 0.001). The change in DLA measurements after propofol administration decreased significantly as STOP-BANG score increased (r = -0.344, P = 0.037). However, DLA measurements when patients were awake increased significantly with an increase in the STOP-BANG score (r = 0.351, P = 0.031). These findings suggest that propofol widens and flattens the tongue, which are changes that may contribute to difficult airway management. Given the quick and non-invasive nature of ultrasound, further studies should evaluate the role of submandibular ultrasound for understanding the upper airway and airway management in various populations.

Predicting tracheal work of breathing in neonates based on radiological and pulmonary measurements.

Tracheomalacia is an airway condition in which the trachea excessively collapses during breathing. Neonates diagnosed with tracheomalacia require more energy to breathe, and the effect of tracheomalacia can be quantified by assessing flow-resistive work of breathing (WOB) in the trachea using computational fluid dynamics (CFD) modeling of the airway. However, CFD simulations are computationally expensive; the ability to instead predict WOB based on more straightforward measures would provide a clinically useful estimate of tracheal disease severity. The objective of this study is to quantify the WOB in the trachea using CFD and identify simple airway and/or clinical parameters that directly relate to WOB. This study included 30 neonatal intensive care unit subjects (15 with tracheomalacia and 15 without tracheomalacia). All subjects were imaged using ultrashort echo time (UTE) MRI. CFD simulations were performed using patient-specific data obtained from MRI (airway anatomy, dynamic motion, and airflow rates) to calculate the WOB in the trachea. Several airway and clinical measurements were obtained and compared with the tracheal resistive WOB. The maximum percent change in the tracheal cross-sectional area (ρ = 0.560, P = 0.001), average glottis cross-sectional area (ρ = -0.488, P = 0.006), minute ventilation (ρ = 0.613, P < 0.001), and lung tidal volume (ρ = 0.599, P < 0.001) had significant correlations with WOB. A multivariable regression model with three independent variables (minute ventilation, average glottis cross-sectional area, and minimum of the eccentricity index of the trachea) can be used to estimate WOB more accurately (R2 = 0.726). This statistical model may allow clinicians to estimate tracheal resistive WOB based on airway images and clinical data.NEW & NOTEWORTHY The work of breathing due to resistance in the trachea is an important metric for quantifying the effect of tracheal abnormalities such as tracheomalacia, but currently requires complex dynamic imaging and computational fluid dynamics simulation to calculate it. This study produces a method to predict the tracheal work of breathing based on readily available imaging and clinical metrics.

Assessment of Anatomic Airway Changes in Obstructive Sleep Apnea Patients Post Bariatric Surgery

Obstructive sleep apnea (OSA) is known to cause adverse health-related effects, reduce quality of life, and is the most common sleep disordered respiratory disease. Obesity is a main risk factor for OSA and several studies have investigated the effect of surgical weight loss on OSA. Some of these studies have shown an improvement in the apnea-hypopnea index (AHI) in OSA patients following bariatric surgery; however, the extent to which OSA improves is unclear. In their 2009 systematic review, Greenburg et al concluded that despite an improvement in AHI, most OSA patients still had moderately severe OSA and should not expect a cure from bariatric surgery.

Endotracheal Intubation Using a Flexible Intubation Endoscope As a Standardized Model for Safe Airway Management in Swine.

Endotracheal intubation is often a basic requirement for translational research in porcine models for various interventions that require a secured airway or high ventilation pressures. Endotracheal intubation is a challenging skill,requiring a minimum number of successful endotracheal intubations to achieve a high success rate under optimal conditions, which is often unachievable for non-anaesthesiology researchers. Due to the specific porcine airway anatomy, a difficult airway can usually be assumed. The impossibility of establishing a secure airway can result in injury, adverse events, or death of the laboratory animal. Using a prospective, randomized, controlled evaluation approach, it has been shown that fiberoptic-assisted endotracheal intubation takes longer but has a higher first-pass success rate than conventional intubation without causing clinically relevant drops in oxygen saturation. This model presents a standardized regimen for endoscopically guided endotracheal intubation, providing a secured airway, especially for researchers who are inexperienced in the technique of endotracheal intubation via direct laryngoscopy. This procedure is expected to minimize animal suffering and unnecessary animal losses.

Respiratory Tract Deposition of E-Cigarette Particles.

Total and regional deposition of inhaled electronic cigarette (E-cig) particles in the respiratory tract (RT) depends on both physical properties of the inhaled particles and biological factors of users, for example, breathing pattern or puff profile, airway anatomy, and regional ventilation. Accurate particle sizing of E-cig aerosols is essential for predicting particle deposition in the RT. Studies using a variety of sizing methods have shown mass median aerodynamic diameters ranging from 0.2 to 1.2 um and secondary count diameters in the ultrafine range (<0.1 μm). Incorporating these particle sizes into a multiple-path particle dosimetry (MPPD) model shows 10% to 45% total lung deposition by mass and 30% to 80% for ultrafine particles depending on the breathing patterns. These predictions are consistent with experimental measures of deposition fraction of submicron and ultrafine particles. While box-mod-type E-cig devices allow for full "direct-lung" inhalations of aerosol, the more recent pod-based, and disposable E-cigs (e.g., JUUL, Puff Bar, Stig) deliver the aerosol as a "mouth-to-lung" puff, or bolus, that is inhaled early in the breath followed to various degrees by further inhalation of ambient air. Measurement of realistic ventilation patterns associated with these various devices may further improve deposition predictions. Finally, while in vivo measures of RT deposition present a challenge, a recent methodology to radiolabel E-cig particles may allow for such measurements by gamma scintigraphy. Supported by NIH/NHLBI R01HL139369. © 2022 American Physiological Society. Compr Physiol 12: 1-10, year.