Dynamic Volume Computed Tomography Imaging of the Upper Airway in Obstructive Sleep Apnea

Non-brachycephalic dogs with stertor have higher nasopharyngeal collapsibility compared with dogs without stertor and foramen lacerum level is ideal for evaluating nasopharyngeal collapse on dynamic CT

Stertor, a clinical sign associated with obstructive airway syndrome, is often observed in non-brachycephalic dogs. This prospective, case-control study aimed to compare soft palate dimensions, nasopharyngeal cross-sectional area (CSA), and nasopharyngeal collapsibility at various locations in non-brachycephalic dogs with and without stertor. A total of 50 dogs were recruited and stratified into control (n = 34) and stertor (n = 13) groups. Static and dynamic computed tomography was conducted without tracheal intubation, and the following variables were calculated: normalized soft palate length and thickness, normalized maximum and minimum nasopharyngeal CSAs (rCSAmax and rCSAmin), and nasopharyngeal collapsibility at the level of the cranial end of the soft palate, pterygoid hamulus, foramen lacerum, bony labyrinth, and caudal end of the soft palate. The stertor group demonstrated significantly lower rCSAmax and rCSAmin, as well as higher nasopharyngeal collapsibility compared with the control group, while no significant differences were noted in the soft palate dimension. Evaluating nasopharyngeal collapse at the foramen lacerum level was recommended due to the clear presence of identifiable bony landmarks and lower overlap in the nasopharyngeal collapsibility between dogs with and without stertor. Physical dimensions of the soft palate may not be the primary contributing factor to nasopharyngeal collapse and clinical signs in non-brachycephalic dogs.

Vibro-Acoustic Platelet Activation: An Additive Mechanism of Prothrombosis with Applicability to Snoring and Obstructive Sleep Apnea

Introduction: Obstructive sleep apnea (OSA) and loud snoring are conditions with increased cardiovascular risk and notably an association with stroke. Central in stroke are thrombosis and thromboembolism, all related to and initiaing with platelet activation. Platelet activation in OSA has been felt to be driven by biochemical and inflammatory means, including intermittent catecholamine exposure and transient hypoxia. We hypothesized that snore-associated acoustic vibration (SAAV) is an activator of platelets that synergizes with catecholamines and hypoxia to further amplify platelet activation. Methods: Gel-filtered human platelets were exposed to snoring utilizing a designed vibro-acoustic exposure device, varying the time and intensity of exposure and frequency content. Platelet activation was assessed via thrombin generation using the Platelet Activity State assay and scanning electron microscopy. Comparative activation induced by epinephrine and hypoxia were assessed individually as well as additively with SAAV, as well as the inhibitory effect of aspirin. Results: We demonstrate that snore-associated acoustic vibration is an independent activator of platelets, which is dependent upon the dose of exposure, i.e., intensity x time. In snoring, acoustic vibrations associated with low-frequency sound content (200 Hz) are more activating than those associated with high frequencies (900 Hz) (53.05% vs. 22.08%, p = 0.001). Furthermore, SAAV is additive to both catecholamines and hypoxia-mediated activation, inducing synergistic activation. Finally, aspirin, a known inhibitor of platelet activation, has no significant effect in limiting SAAV platelet activation. Conclusion: Snore-associated acoustic vibration is a mechanical means of platelet activation, which may drive prothrombosis and thrombotic risk clinically observed in loud snoring and OSA.

Current Trends in Orthognathic Surgery

Orthognathic surgery has evolved significantly over the past century. Osteotomies of the midface and mandible are contemporaneously used to perform independent or coordinated movements to address functional and aesthetic problems. Specific advances in the past twenty years include increasing fidelity with computer-assisted planning, the use of patient-specific fixation, expanding indications for management of upper airway obstruction, and shifts in orthodontic-surgical paradigms. This review article serves to highlight the contemporary practice of orthognathic surgery.

Comparing Diagnostic Efficacy of Imaging During Muller's Maneuver Versus Drug Induced Sleep Endoscopy in Obstructive Sleep Apnoea

The aim of the study was to compare the diagnostic efficacy of quantitative computed tomography (CT) based upper airway analysis using the Muller's maneuver (MM) and compare the findings with drug induced sleep endoscopy (DISE). A prospective observational study was conducted on 50 adult patients with symptoms of OSA and having apnoea-hypopnea index more than 5. They further underwent CT during normal breathing and during MM; findings of which were compared with DISE. Collapse at velum had statistically significant correlation with collapse at retropalatal level in CT (in MM) (P value = 0.001; r = 0.536). Base of tongue in DISE correlates significantly with retroglossal collapse on CT (P value = 0.002; r = 0.423). Epiglottic and oropharyngeal collapse had no correlation with any CT parameter. Collapse in CT as measured during MM shows significant correlation with DISE findings at velum and tongue base but cannot solely predict all levels without the aid of DISE.

Dynamic Volumetric Computed Tomography Angiography is an Effective Method to Evaluate Tracheomalacia in Children

OBJECTIVE

Standard methods to evaluate tracheal pathology in children, including bronchoscopy, may require general anesthesia. Conventional dynamic proximal airway imaging in noncooperative children requires endotracheal intubation and/or medically induced apnea, which may affect airway mechanics and diagnostic performance. We describe a technique for unsedated dynamic volumetric computed tomography angiography (DV-CTA) of the proximal airway and surrounding vasculature in children and evaluate its performance compared to the reference-standard of rigid bronchoscopy.

METHODS

Children who had undergone DV-CTA and bronchoscopy in one-year were retrospectively identified. Imaging studies were reviewed by an expert reader blinded to the bronchoscopy findings of primary or secondary tracheomalacia. Airway narrowing, if present, was characterized as static and/or dynamic, with tracheomalacia defined as >50% collapse of the tracheal cross-sectional area in exhalation. Pearson correlation was used for comparison.

RESULTS

Over a 19-month period, we identified 32 children (median age 8 months, range 3-14 months) who had undergone DV-CTA and bronchoscopy within a 90-day period of each other. All studies were unsedated and free-breathing. The primary reasons for evaluation included noisy breathing, stridor, and screening for tracheomalacia. There was excellent agreement between DV-CTA and bronchoscopy for diagnosis of tracheomalacia (κ = 0.81, p < 0.001), which improved if children (n = 25) had the studies within 30 days of each other (κ = 0.91, p < 0.001). CTA provided incremental information on severity, and cause of secondary tracheomalacia.

CONCLUSION

For most children, DV-CTA requires no sedation or respiratory manipulation and correlates strongly with bronchoscopy for the diagnosis of tracheomalacia.

LEVEL OF EVIDENCE

3 Laryngoscope, 133:410-416, 2023.

Accuracy and Reliability of 4D-CT and Flexible Laryngoscopy in Upper Airway Evaluation in Robin Sequence

OBJECTIVES

To evaluate the performance of 4-dimensional computed tomography (4D-CT) in assessing upper airway obstruction (UAO) in patients with Robin sequence (RS) and compare the accuracy and reliability of 4D-CT and flexible fiber-optic laryngoscopy (FFL).

STUDY DESIGN

Prospective survey of retrospective clinical data.

SETTING

Single, tertiary care pediatric hospital.

METHODS

At initial and 30-day time points, a multidisciplinary group of 11 clinicians who treat RS rated UAO severity in 32 sets of 4D-CT visualizations and FFL videos (dynamic modalities) and static CT images. Raters assessed UAO at the velopharynx and oropharynx (1 = none to 5 = complete) and noted confidence levels of each rating. Intraclass correlation and Krippendorff alpha were used to assess intra- and interrater reliability, respectively. Accuracy was assessed by comparing clinician ratings with quantitative percentage constriction (QPC) ratings, calculated based on 4D-CT airway cross-sectional area. Results were compared using Wilcoxon rank-sum and signed-rank tests.

RESULTS

There was similar intrarater agreement (moderate to substantial) with 4D-CT and FFL, and both demonstrated fair interrater agreement. Both modalities underestimated UAO severity, although 4D-CT ratings were significantly more accurate, as determined by QPC similarity, than FFL (-1.06 and -1.46 vs QPC ratings, P = .004). Overall confidence levels were similar for 4D-CT and FFL, but other specialists were significantly less confident in FFL ratings than were otolaryngologists (2.25 and 3.92, P < .0001).

CONCLUSION

Although 4D-CT may be more accurate in assessing the degree of UAO in patients with RS, 4D-CT and FFL assessments demonstrate similar reliability. Additionally, 4D-CT may be interpreted with greater confidence by nonotolaryngologists who care for these patients.

Dynamic computed tomography evaluation of the nasopharynx in normal Beagle dogs

Pharyngeal collapsibility has been used as diagnostic criteria in dogs, whereas the normal range and quantitative method have not been studied. Dynamic and static computed tomography (CT) was performed in 23 normal Beagle dogs to quantify the nasopharyngeal collapsibility at different locations. Using dynamic CT, maximum and minimum nasopharyngeal cross-sectional areas (CSAs) were measured at the level of the cranial end of the soft palate, pterygoid hamulus, foramen lacerum, bony labyrinth, and caudal end of the soft palate. The ratio of all maximum and minimum CSA to nasopharyngeal CSA at the level of the caudal hard palate (rCSAmax and rCSAmin) and the nasopharyngeal collapsibility were calculated. The differences of rCSAmax, rCSAmin, and nasopharyngeal collapsibility were analyzed at various locations. The nasopharyngeal collapsibility at the level of foramen lacerum, bony labyrinth, and caudal end of soft palate were higher than the others. At the level of the caudal end of the soft palate, rCSAmin was lower than that of the foramen lacerum and bony labyrinth, whereas rCSAmax at foramen lacerum was higher than that of the caudal end of the soft palate. These results indicated that the nasopharynx at the level of foramen lacerum and caudal end of the soft palate were considered notable locations for evaluating collapsibility. Dynamic CT could show the nasopharyngeal dynamic profile and will be an adequate modality for evaluating nasopharynx. Our results will be helpful for further comparative studies in dogs with and without nasopharyngeal collapse.

Effect of sleep on upper airway dynamics in obese adolescents with obstructive sleep apnea syndrome

STUDY OBJECTIVES

The biomechanical basis of obstructive sleep apnea syndrome (OSAS) may influence upper airway dynamics. In this study, we investigate dynamic changes during respiration in wakefulness and sleep in obese adolescents with and without OSAS.

METHODS

Respiratory-gated dynamic magnetic resonance imaging (MRI) at the retropalatal and retroglossal regions was performed with simultaneous measurement of SpO2 and nasal-oral mask airflow and pressure. Airway cross-sectional area (CSA) was determined using AMIRA. Percent change in CSA was calculated from five continuous tidal breaths in states of wakefulness and sleep. Mixed effects models were used to evaluate interactions between group (OSAS/control), site (retropalatal/retroglossal), and stage (wake/sleep).

RESULTS

We studied 24 children with OSAS (mean age 15.49 ± 2.00 years, mean apnea-hypopnea index [AHI] 16.53 ± 8.72 events/h) and 19 controls (mean age 14.86 ± 1.75 years, mean AHI 2.12 ± 1.69 events/h). Groups were similar in age, sex, height, weight, and BMI Z-score. Participants with OSAS had a 48.17% greater increase in percent change of airway CSA during sleep than controls (p < 0.0001), while there was no difference between groups during wakefulness (p = 0.6589). Additionally, participants with OSAS had a 48.80% increase in percent change of airway CSA during sleep as compared with wakefulness (p < 0.0001), whereas no such relationship was observed in controls (p = 0.5513).

CONCLUSIONS

This study demonstrates significant effects of sleep on upper airway dynamics in obese children with OSAS. Dynamic MRI with physiological data can potentially provide further insight into the biomechanical basis of OSAS and assist in more effective management.

Rapid Maxillary Expansion Has a Beneficial Effect on the Ventilation in Children With Nasal Septal Deviation: A Computational Fluid Dynamics Study

Nasal septal deviation (NSD) is one of the most common nasal diseases. Different from common clinical examination methods, computational fluid dynamics (CFD) can provide visual flow information of the nasal cavity. The dimension and volume of the nasal cavity are easily affected by rapid maxillary expansion (RME). The purpose of this study was to use CFD to evaluate the effect of RME on the aerodynamics of the nasal cavity in children with maxillary transverse deficiency and NSD. Computational fluid dynamics was implemented after 3D reconstruction based on the CBCT of 15 children who have completed RME treatment. After treatment, the volume increases in the nasal cavity, nasopharynx, oropharynx, and pharynx were not statistically significant. The wall shear stress of the nasal cavity after RME, 1.749 ± 0.673 Pa, was significantly lower than that before RME, 2.684 ± 0.919 Pa. Meanwhile, the maximal negative pressure in the pharyngeal airway during inspiration was smaller after RME (-31.058 Pa) than before (-48.204 Pa). This study suggests that RME has a beneficial effect on nasal ventilation. The nasal airflow became more symmetrical in the bilateral nasal cavity after RME. Pharyngeal resistance decreased with the reduction in nasal resistance and the increase in the volume of oropharynx after RME.

Sleep-Induced Glottis Closure in Multiple System Atrophy Evaluated by Four-Dimensional Computed Tomography

Multiple system atrophy (MSA) is a progressive neurodegenerative disorder. Since patients with MSA often have sleep-related respiratory disorders including upper-airway obstruction and/or central sleep disturbance, appropriate evaluation of the upper airway especially during sleep may be indispensable. Fiberoptic laryngoscopy during diazepam-induced sleep has been reported for upper-airway obstruction verification. However, some patients cannot endure the uncomfortable sensation of the fiberscope. To address these issues, we devised a protocol of four four-dimensional computed tomography (4D-CT) for upper-airway evaluation during sleep. Here, we report the case of patient with MSA who was evaluated for upper-airway obstruction during sleep using 4D-CT. A 46-year-old man (height 1.60 m, weight 79 kg) was admitted to our neurological department for tracheal intubation because of a sudden onset of respiratory failure occurring at night. At the age of 45 years, he was diagnosed as MSA with predominant parkinsonism. As pulmonary disease had been excluded and his swallowing was normal, our differential diagnoses were central sleep apnea or obstructive sleep apnea related to his MSA or obstructive sleep apnea (SA) related to his obesity. A tracheostomy was done to maintain the airway after extubation. Polysomnography showed obstructive SA and not central SA. Awake fiberoptic laryngoscopy showed no upper airway obstruction but bilateral vocal abduction impairment (BVAI) during inspiration. To assess the spatial and temporal conditions of the upper respiratory tract—the patient could not tolerate sleep laryngoscopy—we carried out a 4D-CT. Reconstructed 4D-CT images of respiration during sleep showed clear abnormalities: glottis closure at the terminal stage of inspiration and subsequent velopharyngeal closure. As glottis closure does not occur normally in obesity patients, the cause of the respiratory failure in this patient was considered MSA-related sleep-induced airway obstruction. We decided to keep the tracheostoma, because BVAI in patients with MSA may be getting worse, although central apnea after tracheostomy may cause sudden central origin-related death; 4 months postoperatively, the patient had experienced no further airway-related complications. This report indicates that 4D-CT sequential upper-airway assessment during sleep is useful for determining the abnormalities causing obstructive SA in patients with MSA.

Upper airway visualization in pediatric obstructive sleep apnea

Pediatric Obstructive Sleep Apnea (OSA) is a condition that may lead to a variety of comorbidities in adolescence and adulthood. The gold standard of diagnosing OSA is polysomnography (PSG). Over the past fifteen years numerous publications have explored how to better visualize the upper airway to further assess OSA in the pediatric population, and eventually institute personalized treatment. Lateral neck radiograph, cephalometry, computed axial tomography, and magnetic resonance imaging are all unique imaging techniques that are used in the diagnosis of OSA. Drug Induced Sleep Endoscopy is a direct visualization technique that is gathering momentum in pediatrics. Each approach has respective benefits and weaknesses. However, none of them at this time can replace PSG. They are a helpful supplement in those patients with complicated upper airway anatomy and in those with residual OSA.

The Value of Dynamic Voice CT Scan for Complex Airway Patients Undergoing Voice Surgery

Introduction:

Dynamic voice computerized tomography (DVCT) is a novel technique that provides additional information to characterize laryngeal function for patients with complex airway history that may alter surgical decisions. The goal of this study was to evaluate the impact of DVCT on decision making for reconstructive voice surgery for a cohort of post-airway reconstruction dysphonia patients.

Methods:

Retrospective chart review at a pediatric tertiary care center for patients with history of complex airway surgery and subsequent reconstructive voice surgery for dysphonia between 2010 and 2016. The study group had a DVCT prior to surgery while the control group underwent surgery without a DVCT. Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) and pediatric Voice Handicap Index (pVHI) scores were evaluated by the voice clinic team (otolaryngologist, speech therapist) before and after voice surgery.

Results:

Twenty-one patients were analyzed (14 female, 67%) with a mean age (SD) of 14 (4.5) years old. Ninety percent (17/21) had a prior tracheostomy and a mean (SD) of 2.6 (1.3) airway surgeries. Twelve patients (57%) underwent DVCT prior to reconstructive voice surgery. CAPE-V baseline scores were similar between study and controls (means [SE] = 49 [4.6] and 57 [6.0], P = .72). However, scores significantly improved for the study group after voice surgery (mean [SE] = 31 (4.7), P < .0001) while controls did not improve (58 [5.7], P = .99). Baseline VHI scores were similar between both groups: mean (SE) = 54 (5.4) versus 52 (6.2), respectively, P = .99. Postsurgically, VHI scores were also similar between both groups (means [SE]: 46 [7.1] vs 47 [4.5], P = .99). Reconstructive voice surgery for study patients included posterior cricoid reduction (46%), vocal fold medialization/augmentation (46%), and laryngeal reinnervation (7.7%) while all controls underwent a single treatment (vocal fold medialization/augmentation).

Conclusion:

Patients with preoperative DVCT were more likely to have improvement. DVCT appeared to have altered surgical decision making and has allowed tailoring of reconstructive surgery to specific patients’ needs. DVCT could represent an important tool prior to reconstructive surgery to guide the choice of surgical procedures for complex airway patients.

Otolaryngologic management of Down syndrome patients: what is new?

PURPOSE OF REVIEW

The management of children with Down syndrome as it pertains to the otolaryngologist continues to evolve. Obstructive sleep apnea (OSA) has dominated the recent literature, but other topics including hearing loss, swallowing, and perioperative considerations are also reported.

RECENT FINDINGS

The prevalence of OSA in children with Down syndrome ranges from 57 to 73% in certain cohorts, and, whereas adentonsillectomy can decrease Apnea-Hypopnea Index, up to 80% may have persistent OSA. Surgical techniques involving reduction of the base of tongue are effective for those who fail adenotonsillectomy, and it is expected that drug-induced sleep endoscopy may improve outcomes. New technology is also on the horizon that can assist with diagnosis and treatment including computational modelling and upper airway stimulation. Children with Down syndrome may not respond to medical management of eustachian tube dysfunction as well as normally developing children. In addition, there is a high prevalence of inner ear anomalies, increasing the risk for sensorineural hearing loss.

SUMMARY

Questions remain pertinent to the otolaryngologist regarding the ideal management of children with Down syndrome. Additional studies are necessary, to optimize understanding and treatment of this complex population, in particular as opportunities develop with technological advances.

The role of upper airway morphology in apnea versus hypopnea predominant obstructive sleep apnea patients: an exploratory study

OBJECTIVE

The objective of this study was to investigate the association between upper airway morphology and apnea vs hypopnea predominance in patients with obstructive sleep apnea (OSA) syndrome.

METHODS

A retrospective study on consecutively CT scans obtained from 54 OSA patients and 53 non-snoring controls. CT scans were measured to evaluate upper airway and surrounding structures' morphologic characteristics. OSA patients (matched for age, gender and body mass index) compared as two groups; apneic group: apnea ratio >50% and hypopneic group: hypopnea ratio >50%. Morphologic characteristics were analyzed using Kruskal-Wallis test and Pearson's correlation test.

RESULTS

Apneic group (17 patients) showed 76.56% apnea rate and hypopneic group (37 patients) showed 78.46% hypopnea rate. Minimal lateral and anteroposterior dimensions of velopharynx in the apneic group (0.86 ± 0.73 and 0.21 ± 0.13 cm, respectively) was statistically lesser from that of the hypopneic group (1.2 ± 0.42 and 0.54 ± 0.22 cm, respectively). Minimum cross-sectional area of the velopharynx was also lesser in apneic group (0.21 ± 0.16 cm²) than that in hypopneic group (0.65 ± 0.38 cm²). Almost all upper airway parameters in both apneic and hypopneic groups were tended to be smaller than in controls.

CONCLUSION

Decrease in airway volume does not signify the type of respiratory event, but significant narrowing of velopharynx in both dimensions; thus having the narrowest value below a certain level causes more apnea. Advances in knowledge: We did not find a similar study when we did a literature search, showing the relationship of apnea vs hypopnea predominance and upper airway parameters in CT in patients with OSA.

Preliminary Assessment of Dynamic Voice CT in Post–Airway Reconstruction Patients

Objectives

To compare the ability of the dynamic voice computed tomography (CT) scan to characterize laryngeal function in airway reconstruction patients vs bedside endoscopic nasopharyngolaryngoscopy and videolaryngostroboscopy.

Study Design

Case series with chart review.

Settings

Pediatric tertiary care center.

Subjects and Methods

Retrospective case series of children and young adults with a history of complex airway surgeries with subsequent dysphonia. We analyzed clinical data for all patients who underwent an airway reconstruction procedure between January 1, 2010, and April 30, 2016, and also had a dynamic voice CT and bedside endoscopic exam during the same period.

Results

Twenty-four patients were analyzed (4 male, 20 female) with a mean age of 15.1 years (95% confidence interval [CI], 12.9-17.22). Patients had a mean of 2.2 airway surgeries (95% CI, 1.8-2.6), with 62.5% of them being open procedures. Laryngotracheoplasty with a cartilage graft was the most common procedure (40.0%). The pattern of laryngeal closure could be detected in all cases with the dynamic CT scan (n = 24/24, 100%) compared to 87.5% (21/24) with the standard endoscopic examination ( P = .04). The location of gap closure could be detected in all cases (24/24) with the dynamic voice CT while 20.8% (5/24 patients) could not be rated with standard endoscopy/stroboscopy ( P = .02). Dynamic voice CT was able to assess the vertical closure pattern of the glottis 100% (24/24) while it could be detected in 83.3% (20/24) cases with endoscopic study ( P = .04).

Conclusion

Dynamic voice CT shows promise as an additional tool for evaluation of patients with a history of complex airway procedures by providing complementary information.

Characterization of upper airway obstruction using cine MRI in children with residual obstructive sleep apnea after adenotonsillectomy

OBJECTIVES/BACKGROUND

Tonsillectomy and adenoidectomy (T&A) lead to resolution of obstructive sleep apnea (OSA) in most children. However, OSA persists in about 25-40% of children. Cinematic magnetic resonance imaging (cine MRI) can aid the management of persistent OSA by localizing airway obstruction. We describe our experience in implementing and optimizing a cine MRI protocol by using a 3 Tesla MRI scanner, and the use of dexmedetomidine for sedation to improve reproducibility, safety, and diagnostic accuracy.

PATIENTS/METHODS

Patients aged 3-18 years who underwent cine MRI for the evaluation of persistent OSA after T&A and failed positive airway pressure (PAP) therapy were included. Clinical data and the apnea-hyponea index were compared with quantitative and qualitative estimates of airway obstruction from imaging sequences.

RESULTS

A total of 36 children were included with a mean age of 9.6 ± 4.6 (SD) years with 40% over 12 years of age. Two-thirds of them were boys. Seventeen out of 36 children (47%) had Down syndrome. Single site and multilevel obstruction were identified in 21 of 36 patients (58%) and in 12 of 36 patients (33%), respectively. All cine MRIs were performed without complications. Multiple regression analysis demonstrated that a combination of the minimum airway diameter and body mass index z-score best predicted OSA severity (P = 0.002).

CONCLUSIONS

Cine MRI is a sensitive, safe, and noninvasive modality for visualizing upper airway obstruction in children with persistent OSA after T&A. Accurate identification of obstruction can assist in surgical planning in children who fail PAP therapy.