State-related changes in upper airway caliber and surrounding soft-tissue structures in normal subjects

3D analysis of upper airway morphology related to obstructive sleep apnea severity

BACKGROUND

Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder characterized by repetitive collapse of the upper airway during sleep. However, little evidence is available on the differences between the sub-regions of the upper airway morphology and OSA severity. Since orthodontists frequently perform cone beam computed tomography (CBCT) in the neck area, we aimed to investigate the relationship and the differences between upper airway morphology and OSA severity using CBCT.

MATERIALS AND METHODS

The medical records, CBCT imaging of 21 OSA patients diagnosed by polysomnography, and the apnea-hypopnea index (AHI) results were included to classify OSA severity as mild, moderate, or severe. The minimum cross-sectional areas (MCA) and volumes of the upper pharyngeal airway boundaries in four sub-regions: nasopharynx, retropalatal, retroglossal, and hypopharynx were measured. Dolphin Imaging software was used for upper airway segmentation. The correlation coefficient (r), one-way ANOVA, and the least significant difference post hoc multiple comparison test were applied to fulfill the objectives.

RESULTS

A statistically significant relationship was found between the MCA of the nasopharynx and the AHI (r = -0.473, P < 0.05). Furthermore, a difference was found between mild and moderate and moderate and severe OSA severity in the MCA results of the retroglossal region (P < 0.05). However, no relationship was found between the upper airway volume and OSA severity.

CONCLUSIONS

MCA was moderately negatively correlated to AHI only in the nasopharynx subregion. Moderate OSA presented significantly less MCA than mild and severe OSA only in the oropharynx and retroglossal subregions.

Surgical Management of Pediatric Obstructive Sleep Apnea Beyond Adenotonsillectomy: The Nose, Nasopharynx, and Palate

While adenotonsillectomy is the primary treatment of pediatric obstructive sleep apnea (OSA), persistent OSA after surgery is common and may be due to residual obstruction at the nose, nasopharynx, and/or palate. Comprehensive evaluation for persistent pediatric OSA ideally includes clinical examination (with or without awake nasal endosocpy) as well as drug-induced sleep endoscopy in order to accurately identify sources of residual obstruction. Depending on the site of obstruction, some of the surgical management options include submucous inferior turbinate resection, septoplasty, adenoidectomy, and expansion sphincter pharyngoplasty.

State-Dependent Biomechanical Behavior of Oropharyngeal Structures in Apneic and Control Subjects: A Proof-of-Concept Study

Rationale: Apneic individuals have reduced airway caliber during sleep. The biomechanical changes in upper airway anatomy contributing to this airway narrowing are largely unknown. Objectives: We sought to investigate the state-dependent (wake vs. sleep) biomechanical behavior of the upper airway soft-tissue and craniofacial structures. Methods: Upper airway magnetic resonance imaging was performed in 15 sleep-deprived control subjects (apnea-hypopnea index, <5; 0.3 ± 0.5 events per hour) and 12 sleep-deprived apneic subjects (apnea-hypopnea index, ⩾5; 35.2 ± 18.1 events per hour) during wake and sleep and analyzed for airway measures and soft-tissue/mandibular movement. Results: In the retropalatal region, control subjects showed sleep-dependent reductions (P ⩽ 0.037) in average cross-sectional airway area (CSA), minimum CSA, and anteroposterior and lateral dimensions. Apneic subjects showed sleep-dependent reductions (P ⩽ 0.002) in average CSA, minimum CSA, and anteroposterior and lateral dimensions. In the retroglossal region, control subjects had no sleep-dependent airway reductions. However, apneic subjects had sleep-dependent reductions in minimal CSA (P = 0.001) and lateral dimensions (P = 0.014). Control subjects only showed sleep-dependent posterior movement of the anterior-inferior tongue octant (P = 0.039), whereas apneic subjects showed posterior movement of the soft palate (P = 0.006) and all tongue octants (P ⩽ 0.012). Sleep-dependent medial movement of the lateral walls was seen at the retropalatal minimum level (P = 0.013) in control subjects and at the retropalatal and retroglossal minimum levels (P ⩽ 0.017) in apneic subjects. There was posterior movement of the mandible in apneic subjects (P ⩽ 0.017). Conclusions: During sleep, control and apneic subjects showed reductions in retropalatal airway caliber, but only the apneic subjects showed retroglossal airway narrowing. Reductions in anteroposterior and lateral airway dimensions were primarily due to posterior soft palate, tongue and mandibular movement and to medial lateral wall movement. These data provide important initial insights into obstructive sleep apnea pathogenesis.

Effects of rapid maxillary expansion on upper airway parameters in OSA children with maxillary restriction: A CBCT study

BACKGROUND

Rapid maxillary expansion (RME) has been proposed as an effective treatment for pediatric obstructive sleep apnea (OSA) and maxillary restriction in children. This study aimed to evaluate the effect of RME appliances on the nasomaxillary complex dimensions in children with OSA and maxillary constriction.

METHODS

This prospective longitudinal study included 34 children aged 8-12 years with maxillary restriction and OSA confirmed by polysomnography who had completed RME therapy. The nasomaxillary complex is segmented into the nasal cavity, maxillary sinuses, and nasopharynx. The effect of RME on nasomaxillary complex dimensions was assessed pre and posttreatment using cone-beam computed tomography, analysis, while a second standard overnight polysomnography (PSG) was performed to assess changes in respiratory parameters.

RESULTS

Significant improvements were observed, including inferior maxillary dislocation (S-S1 distance and N-ANS), increased anterior and posterior facial height, and a 5.43 events/h reduction in Apnea-Hypopnea Index (p < .001). The nasal cavity volume increased by 2439 (±584) mm3 (p < .001), nasopharynx size increased by 883 (±479) mm3 (p = .008), mid cross-sectional area increased by 31.74 (±14.50) mm2 (p < .001), and the distance between the right and left maxillary sinuses increased by 8.37 (±3.67) mm (p < .001) all exhibited positive changes, with some insignificant variations in volume change (p = .254).

CONCLUSION

RME treatment was found to be effective in improving nasal cavity and nasopharyngeal dimensions, leading to improved respiratory parameters in children with OSA and maxillary constriction. While these results are promising, considerations about the potential long-term benefits of RME on future growth are important. The study provides valuable insights into the efficacy of RME as a treatment option for this pediatric population.

The effect of pharyngeal structures on the severity of obstructive sleep apnea

BACKGROUND/OBJECTIVE

Obstructive sleep apnea (OSA) is characterized by complete or partial cessation of breathing during sleep. The tongue is suggested as a possible anatomical site causing airway obstruction. However, the role of other pharyngeal structures in the development of OSA remains unclear. We designed a study using both the apnea-hypopnea index (AHI) and the oxygen saturation measurements to assess the severity of OSA. We aimed to identify critical anatomical structures of the upper airway that correlate with the severity of OSA and to evaluate the utility of magnetic resonance imaging (MRI) markers to detect possible OSA in patients without overt symptoms.

MATERIALS AND METHODS

The study included participants referred to the neurology outpatient clinic from the check-up unit. Participants were grouped as controls, mild, moderate, or severe OSA according to the AHI. A cranial MRI with a field of view (FOV) encompassing the upper airway structures was obtained from all participants. The areas of the tongue and the uvula were measured on the sagittal images by drawing the boundaries of the tissues manually. The posterior air space (PAS) area was evaluated from regions of interest in five parallel planes.

RESULTS

Of 105 participants, 30 were controls, 27 had mild, 25 had moderate, and 23 had severe OSA. The moderate and severe OSA groups did not differ in oxygen saturation levels during sleep. Therefore, patients with moderate and severe OSA were combined into one group (moderate/severe OSA). The area of the tongue was significantly larger in the moderate/severe OSA group compared to the control group. Both the tongue and the uvula areas showed a significant positive correlation with the AHI.

CONCLUSION

Our findings suggest that the tongue and uvula have prominent roles in the severity of OSAS. It may be useful to measure these structures with MRI to screen for at-risk individuals without overt OSA symptoms.

Facial Contour Features Measured on CT Reflects Upper Airway Morphology in Patients With OSA

OBJECTIVE

To determine facial contour features, measured on computed tomography (CT), related to upper airway morphology in patients with obstructive sleep apnea (OSA); certain phenotype of facial abnormalities implying restriction of craniofacial skeleton and adipose tissue nimiety has predicted the value of the severity of OSA.

MATERIALS AND METHOD

Sixty-four male patients with OSA [apnea-hypopnea index (AHI) ≥10/h] who had upper airway CT were randomly selected to quantitatively measure indicators of facial contour and upper airway structures. Pearson correlation analyses were performed. Partial correlation procedure was used to examine correlations while controlling body mass index (BMI).

RESULTS

Upper airway anatomy can nearly all be reflected in the face, except retroglossal airway. Upper face width can be measured to assess the overall skeletal structures of the airway. Lower face width can be used to represent how much adipose tissue deposited. Hard palate, retropalatal, and hypopharyngeal airways have corresponding face indicators respectively. Midface width is a better predictor of AHI severity and minimum blood oxygen even than neck circumference because it contains the most anatomical information about the airway, including RP airway condition, soft palate length, tongue volume, etc. These correlations persisted even after correction for BMI.

CONCLUSIONS

All anatomical features of the upper airway except retroglossal airway can be reflected in the face, and midface width is the best predictor of AHI severity and minimum blood oxygen, even better than neck circumference and BMI.

Obstructive sleep apnoea heterogeneity and cardiovascular disease

Obstructive sleep apnoea (OSA), characterized by recurrent periods of upper airway obstruction and intermittent hypoxaemia, is prevalent in patients with cardiovascular disease (CVD), and is therefore important to consider in the prevention and management of CVD. Observational studies indicate that OSA is a risk factor for incident hypertension, poorly controlled blood pressure, stroke, myocardial infarction, heart failure, cardiac arrhythmias, sudden cardiac death and all-cause death. However, clinical trials have not provided consistent evidence that treatment with continuous positive airway pressure (CPAP) improves cardiovascular outcomes. These overall null findings might be explained by limitations in trial design and low levels of adherence to CPAP. Studies have also been limited by the failure to consider OSA as a heterogeneous disorder that consists of multiple subtypes resulting from variable contributions from anatomical, physiological, inflammatory and obesity-related risk factors, and resulting in different physiological disturbances. Novel markers of sleep apnoea-associated hypoxic burden and cardiac autonomic response have emerged as predictors of OSA-related susceptibility to adverse health outcomes and treatment response. In this Review, we summarize our understanding of the shared risk factors and causal links between OSA and CVD and emerging knowledge on the heterogeneity of OSA. We discuss the varied mechanistic pathways that result in CVD that also vary across subgroups of OSA, as well as the potential role of new biomarkers for CVD risk stratification.

Anatomical determinants of upper airway collapsibility in obstructive sleep apnea: A systematic review and meta-analysis

Upper airway (UA) collapsibility is one of the key factors that determine the severity of obstructive sleep apnea (OSA). Interventions for OSA are aimed at reducing UA collapsibility, but selecting the optimal alternative intervention for patients who fail CPAP is challenging because currently no validated method predicts how anatomical changes affect UA collapsibility. The gold standard objective measure of UA collapsibility is the pharyngeal critical pressure (P_crit). A systematic literature review and meta-analysis were performed to identify the anatomical factors with the strongest correlation with P_crit. A search using the PRISMA methodology was performed on PubMed for English language scientific papers that correlated P_crit to anatomic variables and OSA severity as measured by the apnea-hypopnea index (AHI). A total of 29 papers that matched eligibility criteria were included in the quantitative synthesis. The meta-analysis suggested that AHI has only a moderate correlation with P_crit (estimated Pearson correlation coefficient r = 0.46). The meta-analysis identified four key anatomical variables associated with UA collapsibility, namely hyoid position (r = 0.53), tongue volume (r = 0.51), pharyngeal length (r = 0.50), and waist circumference (r = 0.49). In the future, biomechanical models that quantify the relative importance of these anatomical factors in determining UA collapsibility may help identify the optimal intervention for each patient. Many anatomical and structural factors such as airspace cross-sectional areas, epiglottic collapse, and palatal prolapse have inadequate data and require further research.

Effect of Different Maxillary Oral Appliance Designs on Respiratory Variables during Sleep

This study aimed to analyze the efficacy of maxillary oral appliance (MOA) designs on respiratory variables during sleep. At baseline, 23 participants underwent a sleep test with a portable device for two nights and were categorized as participants with mild obstructive sleep apnea (mild-OSA) (n = 13) and without OSA (w/o-OSA) (n = 10). Three types of MOAs, standard-OA (S-OA), palatal covering-OA (PC-OA), and vertically increasing-OA (VI-OA), were each worn for three nights, and sleep tests with each MOA were performed with a portable device for two nights. Based on the average of the respiratory event index (REI) values for the two nights for each MOA, w/o-OSA participants with an REI ≥ 5.0 were defined as the exacerbation group and those with an REI < 5.0 as the non-exacerbation group. In mild-OSA participants, an REI ≥ 15.0 or REI ≥ baseline REI × 1.5 were defined as the exacerbation group and those with an REI < 15.0 and REI < baseline REI × 1.5 were defined as the non-exacerbation group. The percentage of the exacerbation and non-exacerbation groups with MOA was evaluated in the w/o-OSA and mild-OSA participants. The maxillary and mandibular dental-arch dimension was compared by dentition model analysis. The exacerbation group in w/o-OSA participants (n = 10) comprised 10.0% participants (n = 1) with S-OA, 40.0% (n = 4) with PC-OA, and 30.0% (n = 3) with VI-OA. The exacerbation group in the mild-OSA participants (n = 13) comprised 15.4% subjects (n = 2) with S-OA, 23.1% (n = 3) with PC-OA, and 23.1% (n = 3) in VI-OA. In the model analysis for w/o-OSA, the posterior dental arch width was significantly greater in the exacerbation group than in the non-exacerbation group wearing S-OA (p < 0.05). In addition, the ratio of the maxillary to mandibular dental arch width (anterior dental arch width) was significantly greater in the exacerbation group than in the non-exacerbation group for both PC-OA and VI-OA (p < 0.05). In mild-OSA, the maxillary and mandibular dental arch lengths and the ratio of maxillary to mandibular dental arch width (posterior dental arch width) were significantly smaller in the exacerbation group than in the non-exacerbation group for S-OA (p < 0.05). This study confirmed that wearing an MOA by w/o-OSA and mild-OSA participants may increase the REI during sleep and that PC-OA and VI-OA may increase the REI more than S-OA. The maxillary and mandibular dental-arch dimensions may affect the REI when using an MOA.

Validation of the Sonographic Measurement of Lateral Parapharyngeal Wall Thickness in Childhood Obstructive Sleep Apnea

BACKGROUND

Lateral parapharyngeal wall (LPW) thickness is a potentially useful anatomical marker of childhood obstructive sleep apnea (OSA). Measuring LPW thickness by ultrasonography (USG) is technically feasible but its use in children has not been validated. Therefore, this study aimed to assess the intra- and inter-operator reliability of the sonographic measurements of LPW thickness in children and to assess its validity against magnetic resonance imaging (MRI) measurements.

METHODS

Prepubertal children aged 6-11 years suspected to suffer from OSA were recruited. Repeated measurements of LPW thickness by USG were conducted to evaluate the intra- and inter-operator reliability, examined by intraclass correlation coefficient (ICC). LPW thickness was measured as the distance between the internal carotid artery and the echogenic surface of the pharynx in an oblique coronal plane by USG. LPW thickness was measured by MRI at the retropalatal level. The agreement between the LPW thickness measured by USG and MRI was assessed by ICC and Bland-Altman plot.

RESULTS

Thirty-four children (mean age: 8.66 ± 1.61, 26 male) were recruited. The intra- and inter-operator reliability of the LPW thickness by USG was good (ICC = 0.84 and 0.82, respectively). The agreement between the USG-measured and MRI-measured LPW thickness was moderate (ICC = 0.72). he Bland-Altman plot demonstrated a mean difference of 0.061 cm and a 95% limit of agreement from 0.91 to 1.12 cm.

CONCLUSION

In this study, we demonstrated that ultrasonography is a valid and reliable method to assess LPW thickness in children. This study was supported by the Direct Grant for Research from the Research Committee of the Chinese University of Hong Kong (Project no. 2020.073).

Obstructive Sleep Apnoea in pycnodysostosis; a three-dimensional upper airway analysis

AIM

To assess the upper airway (UA) morphology in patients with pycnodysostosis with a 3D analysis, compare results with normative data and investigate correlation of the total volume (TV) to other UA morphology variables.

MATERIALS AND METHODS

Cone beam computed tomography (CBCT) images of eight Danish patients with pycnodysostosis (4 males, 4 females with a mean age of 31.8 years, SD:16.3 years), were analysed using Mimics® (Materialise®, Belgium) and compared with a sex- and age-matched control group (6 males, 8 females with a mean age of 33.6 years, SD:18.6 years).

RESULTS

The distance from the tip of the epiglottis (E) to the Frankfurt horizontal plane (Fp) was significantly shorter in the pycnodysostosis group (p < 0.042). Regarding the cross-sectional measurements, at the "maximum constriction" (p < 0.005), the "upper airway limit" (p < 0.001) and the "lower airway limit" (p < 0.035) cross-sections were significantly smaller in the pycnodysostosis group. The volumes "nasopharynx" (p < 0.002) and "total airway" (TV) (p < 0.01) were also significantly smaller.

CONCLUSION

Patients with pycnodysostosis have a reduced total airway as well as nasopharyngeal volume compared with matched controls. Additionally, they have a reduced cross-sectional area in the upper and lower borders of the UA, and the area of maximum constriction is also reduced. These factors might explain the high prevalence of obstructive sleep apnoea in pycnodysostosis. TV is positively correlated to total length and cross-sections at all levels including the maximum constriction area as well as the anteroposterior dimension at the upper and lower airway borders.

The Biomechanical Mechanism of Upper Airway Collapse in OSAHS Patients Using Clinical Monitoring Data during Natural Sleep

Obstructive sleep apnea hypopnea syndrome (OSAHS) is a common sleep disorder characterized by repeated pharyngeal collapse with partial or complete obstruction of the upper airway. This study investigates the biomechanics of upper airway collapse of OSASH patients during natural sleep. Computerized tomography (CT) scans and data obtained from a device installed on OSASH patients, which is comprised of micro pressure sensors and temperature sensors, are used to develop a pseudo three-dimensional (3D) finite element (FE) model of the upper airway. With consideration of the gravity effect on the soft palate while patients are in a supine position, a fluid–solid coupling analysis is performed using the FE model for the two respiratory modes, eupnea and apnea. The results of this study show that the FE simulations can provide a satisfactory representation of a patient’s actual respiratory physiological processes during natural sleep. The one-way valve effect of the soft palate is one of the important mechanical factors causing upper airway collapse. The monitoring data and FE simulation results obtained in this study provide a comprehensive understanding of the occurrence of OSAHS and a theoretical basis for the individualized treatment of patients. The study demonstrates that biomechanical simulation is a powerful supplementation to clinical monitoring and evaluation.

Importance in the Occurrence Distribution of Minimum Oropharyngeal Cross-Sectional Area in the Different Skeletal Patterns Using Cone-Beam Computed Tomography

Purpose

Obstructive sleep apnea is a condition involving repetitive partial or complete collapse of the pharyngeal airway, especially in patient with mandibular hypoplasia. The present study investigated the differences between the volume of the oropharyngeal airway and the minimum axial area in three skeletal patterns through the use of cone-beam computed tomography (CBCT).

Materials and Methods

CBCT scans of 147 patients were collected to measure the upper oropharyngeal airway volume (UOV), lower oropharyngeal airway volume (LOV), upper oropharyngeal airway area (UOA), minimum upper oropharyngeal airway area (MUOA), lower oropharyngeal airway area (LOA), minimum lower oropharyngeal airway area (MLOA), anatomical structures (orbitale, Or; porion, Po; pogonion, Pog; hyoid, H; second cervical vertebra, C2; fourth cervical vertebra, C4), and relevant angles. Statistical analysis was performed using analysis of variance and Pearson's test.

Results

Compared with patients in Class II, those in Class III and Class I exhibited a significantly anterior position of H and Pog. The vertical positions of H and Pog revealed no significant difference between the three skeletal patterns. Patients in skeletal Class III exhibited significantly larger oropharyngeal area (UOA, MUOA, LOA, MLOA) and oropharyngeal airway (UOV and LOV) than those in skeletal Class II did. The horizontal position of Pog had a moderately significant correlation with UOA (r = 0.471) and MUOA (r = 0.455).

Conclusion

Patients in skeletal Class II had significantly smaller oropharyngeal airway areas and volumes than those in Class III did. The minimum oropharyngeal cross-sectional area had a 67% probability of occurrence in the upper oropharyngeal airway among patients in Class I and Class II and a 50% probability of occurrence among patients in Class III.

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.

Differences in three-dimensional upper airway anatomy between Asian and European patients with obstructive sleep apnea

STUDY OBJECTIVES

This study evaluated differences in upper airway, soft tissues and craniofacial structures between Asians from China and Europeans from Iceland with OSA using three-dimensional magnetic resonance imaging (MRI).

METHODS

Airway sizes, soft tissue volumes, and craniofacial dimensions were compared between Icelandic (N = 108) and Chinese (N = 57) patients with oxygen desaturation index (ODI) ≥ 10 events/h matched for age, gender, and ODI. Mixed effects models adjusting for height or BMI and residual differences in age and ODI were utilized.

RESULTS

In our matched sample, compared to Icelandic OSA patients, Chinese patients had smaller BMI (p < 0.0001) and neck circumference (p = 0.011). In covariate adjusted analyses, Chinese showed smaller retropalatal airway size (p ≤ 0.002), and smaller combined soft tissues, tongue, fat pads, and pterygoid (all p ≤ 0.0001), but male Chinese demonstrated a larger soft palate volume (p ≤ 0.001). For craniofacial dimensions, Chinese demonstrated bigger ANB angle (p ≤ 0.0196), differently shaped mandibles, including shorter corpus length (p < 0.0001) but longer ramus length (p < 0.0001), and a wider (p < 0.0001) and shallower (p ≤ 0.0001) maxilla.

CONCLUSIONS

Compared to Icelandic patients of similar age, gender and ODI, Chinese patients had smaller retropalatal airway and combined soft tissue, but bigger soft palate volume (in males), and differently shaped mandible and maxilla with more bony restrictions. Results support an ethnic difference in upper airway anatomy related to OSA, which may inform targeted therapies.

Upper airway morphological changes in obstructive sleep apnoea: effect of age on pharyngeal anatomy

OBJECTIVE

To evaluate the upper airway morphology changes associated with ageing in adult Chinese patients with obstructive sleep apnoea.

METHODS

A total of 124 male patients diagnosed with obstructive sleep apnoea by overnight polysomnography, who underwent upper airway computed tomography, were enrolled. The linear dimensions, cross-sectional area and volume of the upper airway region and the surrounding bony frame were measured. The association between ageing and upper airway morphology was analysed.

RESULTS

Soft palate length, minimum cross-sectional area of the retroglossal region, lateral dimensions at the minimum cross-sectional area of the retropalatal and retroglossal regions, nasopharyngeal volume, and average cross-sectional area of the nasopharyngeal region were found to significantly increase with ageing in all patients, while the upper airway shape flattened with ageing. The volume of the retropalatal region increased with ageing among the patients with a body mass index of less than 24 kg/m2. The volume of parapharyngeal fat pad increased with ageing among patients with a body mass index greater than 28 kg/m2.

CONCLUSION

A number of dimensional, cross-sectional and volumetric parameters of the pharynx increased with age, indicating that non-anatomical factors may play a more important role in the pathogenesis of obstructive sleep apnoea in aged patients.

Three-Dimensional Assessment of Pharyngeal Volume on Computed Tomography Scans: Applications to Anesthesiology and Endoscopy

Pharyngeal volume is important in anesthesiology for correctly assessing intubation procedures. However, most of studies are based on patients in upright position and do not assess possible relationships between pharyngeal volume and cranial size. This study aims at measuring pharyngeal volume in CT-scans and to assess possible statistically significant differences according to sex.Eighty healthy subjects (40 males and 40 females) aged between 21 and 86 years were retrospectively chosen from a hospital database of maxillofacial CT-scans; 3D segmentation was performed separately for naso-, oro- and laryngopharyngeal portion through ITK-SNAP software, and their volume was calculated. Three cranial measurements were obtained: distance between anterior and posterior nasal spine, upper facial height (nasion-prosthion) and biorbital breadth (ectoconchion-ectoconchion distance).The effect of sex on volume for each pharyngeal portion was assessed through one-way ANCOVA test using each of the 3 cranial measurements as covariate (P < 0.05).On average, the volume of nasopharynx, oropharynx and laryngopharynx was 7.2 ± 2.7 cm, 7.5 ± 4.2 cm, 3.5 ± 2.2 cm respectively in males, and 6.4 ± 2.9 cm, 5.2 ± 2.1 cm, 3.0 ± 1.8 cm in females. Statistically significant differences according to sex were found only for oropharyngeal volume, independently from cranial measurements (P < 0.05).This study provides data concerning volume of pharyngeal air space in supine subjects: these reference standards can be useful for anaesthesiologic procedures.

Quantitative Morphometric Measurements of the Oropharynx in Obstructive Sleep Apnea Syndrome Using a Laser Depth Measurement Module

INTRODUCTION

Current diagnostic routines in obstructive sleep apnea syndrome (OSAS), including drug-induced sleep endoscopy (DISE), provide qualitative data. Quantitative morphometric measurements of oropharyngeal structures remain challenging. This study aims to introduce a special linear laser projection device that can facilitate computer-assisted digitalized analysis and provide important quantitative information for OSAS prediction.

MATERIALS AND METHODS

We used a single-wavelength green three-linear laser to provide the scaling reference, with one at an angle of 8.5 degrees with the other two which were parallel. The oropharyngeal images were divided into two groups: the non-OSAS and OSAS group, after polysomnography. A minimum of three evaluations were carried out to determine the maximum cross-sectional area of the oropharyngeal inlet (CSAOI) and the retropalatal depth.

RESULTS

A total of 132 subjects were enrolled in this study, with 76 subjects in the non-OSAS group and 56 cases in the OSAS group. In the non-OSAS group, the CSAOI was significantly larger in males than in females. There was a trend toward deeper retropalatal region in men than in women (14.25 vs 11.76 mm). Correlation analysis revealed that retropalatal depth is significantly related to body height and the CSAOI. The body weight and BMI of patients with OSAS were significantly higher than those of participants without OSAS. The retropalatal depth and CSAOI were significantly decreased in OSAS patients as compared to those without OSAS. Our new parameter, the oropharyngeal index, showed the most outstanding discrimination by ROC analysis to predict OSAS.

CONCLUSION

Our innovative module can provide reference parameters, which make it possible to directly estimate the objective absolute values of relevant oropharyngeal structures. Our non-invasive approach can be used for outpatient screening, since it allows the identification of potential OSAS patients who should be referred for polysomnography, as many patients do not require DISE early in their evaluation.

Radiation exposure alters airway deformability and bony structure displacement during laryngoscopy

Background

Prior therapeutic radiation exposure in the setting of head and neck malignancies is associated with difficult airway instrumentation. We sought to characterize the anatomic changes that produce this phenotype.

Study Design

Retrospective review.

Methods

Five individuals with prior radiation therapy to the upper aerodigestive tract (previously irradiated) and 10 with no prior history of therapeutic radiation exposure (nonirradiated) were enrolled. Computed tomography images obtained before and during laryngoscope insertion ("uninstrumented" and "instrumented", respectively) were used to reconstruct three-dimensional representations of the pharyngeal airway, hyoid, and mandible.

Results

In the instrumented state, pharyngeal airway volumes were significantly greater in nonirradiated subjects relative to previously irradiated subjects (P = .01), and overall translation of both the hyoid and mandible was also greater in nonirradiated subjects (P = .01 and .04, respectively).

Conclusion

Individuals with prior therapeutic radiation exposure to the upper aerodigestive tract differ from nonirradiated subjects with respect to airway deformation and bony structure translation during laryngoscopy.

Level of Evidence

4.

Threshold of the upper airway cross-section for hypopnea onset during sleep and its identification under waking condition

Background

There is currently no method that can predict whether or under what condition hypopnea, even obstructive sleep apnea (OSA), will occur during sleep for individuals based on credible parameters measured under waking condition. We propose a threshold concept based on the narrowest cross-sectional area of the upper airway (CSA-UA) and aim to prove our hypothesis on the threshold of the area for hypopnea onset (TAHO), which can be used as an indicator of hypopnea onset during sleep and measured while awake.

Methods

We performed magnetic resonance imaging for 20 OSA patients to observe CSA-UA changes during fluid accumulation in the neck caused by elevating their legs, and identified TAHO by capturing the sudden enlargement in CSA-UA. Correlation analyses between TAHO and the body mass index (BMI), and between the reduction in CSA-UA and the increase in the neck circumference (NC) with fluid accumulation were performed. Logistic regression analysis was performed for identifying OSA patients based on the behaviors of their CSA-UA changes during leg raising. Shape changes of airway cross-section were also investigated.

Results

Four CSA-UA change patterns after fluid redistribution were identified. Six patients had similar CSA-UA variation behaviors observed in healthy subjects. From the other three change patterns involving 14 patients, a threshold value of CSA-UA 0.63 ± 0.21 cm² was identified for normal breathing. Data showed a positive correlation between TAHO and BMI (r = 0.681, p = 0.0007), and a negative correlation between the reduction in CSA-UA and the increase in NC (r = − 0.513, p = 0.051) with fluid accumulation. A sigmoid function for the probability of being a OSA patient p = 1/[1 + exp. (4.836 + 3.850 t-8.4 h)] was obtained to effectively separate OSA patients from normal subjects. The upper airway narrowing occurred in anteroposterior, lateral, or both directions, suggesting different tendencies of upper airway collapse in patients. Three types of shape changes in the cross-section of the upper airway, which had different effects on airway resistance, were measured.

Conclusions

Our findings prove TAHO hypothesis. The threshold measured while awake for normal breathing can be used clinically as the indicator of hypopnea onset during sleep, and therefore to identify OSA patients under waking condition and design effective personalized treatments for OSA patients. Both shape and size changes in the cross-section of the upper airway affect airway resistance significantly. Shape change in the cross-section of the upper airway can provide key clinical information on the collapse patterns of the upper airway for individuals.

Does upper airway deformation affect drug deposition?

Knowledge that enables the accurate simulation of drug deposition in the human upper airway is necessary to develop robust platforms for efficient drug delivery by inhalation devices. The human upper airway is deformable during inhalation but how it could affect the deposition of inhaled drugs is unknown. We aimed to determine whether pharyngeal deformation at the soft palate level would have any significant effects on throat deposition, in vitro lung dose and fine particle fraction. In this study, dry mannitol powders were delivered to the next-generation cascade impactor (NGI) through the United States Pharmacopeia (USP) throat, and a realistic upper airway cast (RUPAC) at flow rates of 40, 60 and 80 L min^-1. Deformation of the upper airway at 25%, 50%, and 75% in the lateral and antero-posterior directions were experimentally simulated in the RUPAC. Throat deposition (p = 0.04) is significantly affected when the upper airway deforms laterally but not antero-posteriorly.

Heritability of the pharyngeal airway volume and dimensions as assessed from siblings with overt malocclusions

OBJECTIVE

To quantify the relative contributions of genetic and environmental factors to airway volume and dimensions in orthodontic patients.

MATERIALS AND METHODS

One hundred and twenty-five siblings from 57 families were selected. Cone beam computed tomography scans were taken as part of the orthodontic records and the Dolphin3D © imaging software was used to determine airway volume and dimensions. SOLAR program was implemented to calculate heritability.

RESULTS

The heritability of the airway volume was negligible but increased significantly from 5% to 72% (95% confidence interval was 27% to 100%) when anterior-posterior (AP) dimension was controlled in the calculating model.

CONCLUSION

The capacity to maintain, rather than having proper AP dimension of the airway, seems to be the most critical mark of a proper airway volume.

State-dependent changes in the upper airway assessed by multidetector CT in healthy individuals and during obstructive events in patients with sleep apnea

Objective:

To determine whether airway narrowing during obstructive events occurs predominantly at the retropalatal level and results from dynamic changes in the lateral pharyngeal walls and in tongue position.

Methods:

We evaluated 11 patients with severe obstructive sleep apnea (OSA) and 7 healthy controls without OSA during wakefulness and during natural sleep (documented by full polysomnography). Using fast multidetector CT, we obtained images of the upper airway in the waking and sleep states.

Results:

Upper airway narrowing during sleep was significantly greater at the retropalatal level than at the retroglossal level in the OSA group (p < 0.001) and in the control group (p < 0.05). The retropalatal airway volume was smaller in the OSA group than in the control group during wakefulness (p < 0.05) and decreased significantly from wakefulness to sleep only among the OSA group subjects. Retropalatal pharyngeal narrowing was attributed to reductions in the anteroposterior diameter (p = 0.001) and lateral diameter (p = 0.006), which correlated with an increase in lateral pharyngeal wall volume (p = 0.001) and posterior displacement of the tongue (p = 0.001), respectively. Retroglossal pharyngeal narrowing during sleep did not occur in the OSA group subjects.

Conclusions:

In patients with OSA, upper airway narrowing during sleep occurs predominantly at the retropalatal level, affecting the anteroposterior and lateral dimensions, being associated with lateral pharyngeal wall enlargement and posterior tongue displacement.

Obstruction Patterns During Drug-Induced Sleep Endoscopy vs Natural Sleep Endoscopy in Patients With Obstructive Sleep Apnea

Importance

Drug-induced sleep endoscopy (DISE) has been suggested to be a valuable technique for identifying the obstruction site associated with sleep-disordered breathing. However, the reliability of DISE findings is controversial because the procedure uses sedative drugs, which may have implications for the obstruction patterns observed on DISE.

Objective

To compare the obstruction patterns during DISE with the obstruction patterns during natural sleep endoscopy (NSE).

Design, Setting, and Participants

This prospective cohort study was conducted between June 2013 and May 2018 in Kyungpook National University Chilgok Hospital in Daegu, South Korea. All analysis took place from June 1 to July 31, 2018. Participants had an obstructive sleep apnea diagnosis, were older than 18 years, and had an apnea hypopnea index higher than 5 on type I polysomnography. The patients initially enrolled were excluded from the study for not reaching adequate sleep depth and waking up during insertion of the nasopharyngoscope.

Intervention

Patients underwent DISE using midazolam and NSE without sedatives on 2 different days.

Main Outcomes and Measures

Obstruction findings were observed only in the same range (65-75) of the bispectral index on both days. Obstruction findings were classified according to the VOTE (velum, oropharynx lateral wall, tongue base, and epiglottis) classification. The extent of agreement between DISE and NSE findings was evaluated using Cohen weighted κ value.

Results

The study included 26 patients with snoring or obstructive sleep apnea (mean [SD] age, 44.7 [10.3] years; predominantly male [22 (85%)]). The mean (SD) apnea hypopnea index was 41.9 (17.2) and the lowest mean (SD) oxygen saturation was 79.8% (12.2%). The degree of agreement in upper-airway obstruction between DISE and NSE was 76.9% (Cohen weighted κ = 0.42; 95% CI, 0.02-0.83) in the velum, 88.5% (Cohen weighted κ = 0.84; 95% CI, 0.67-1.01) in the oropharynx lateral wall, 69.2% (Cohen weighted κ = 0.66; 95% CI, 0.46-0.86) in the tongue base, and 92.3% (Cohen weighted κ = 0.67; 95% CI, 0.24-1.11) in the epiglottis. Agreement of configuration of the velum was 88.5% (Cohen weighted κ = 0.50; 95% CI, -0.03 to 1.03) and the epiglottis was 92.3% (Cohen weighted κ = 0.67; 95% CI, 0.24-1.11).

Conclusions and Relevance

Obstruction patterns of the upper airway appeared to be in agreement between DISE and NSE, suggesting that DISE may be a reliable test; future studies of multiple positions and sleep stages with larger sample sizes may confirm these results.

A pilot study to determine the effects of nasal co-phenylcaine on drug-induced sleep endoscopy

Purpose

The use of nasal decongestant and nasal anaesthesia is currently not recommended during drug-induced sleep endoscopy (DISE) according to the European position paper. The evaluation of the effects of nasal decongestant/anaesthesia on DISE has not been performed before and our aim is to perform a pilot study to determine whether nasal decongestants/anaesthesia affects DISE outcomes.

Methods

27 patients undergoing DISE for OSA or for simple snoring were included. On each patient, DISE was performed twice, before and approximately 10 min after the administration of two puffs of co-phenylcaine nasal spray (lidocaine hydrochloride 5%, phenylephrine 0.5%, and benzalkonium chloride 0.01%) into each nostril. A nasal peak inspiratory flow was used for the objective assessment of nasal airway obstruction. During the first and the second DISE the loudness of the snoring was also recorded.

Results

Change in DISE total grading after nasal spray administration was not statistically significant. For the same grading, changes in percentage of contribution to collapse were not statistically significant. Sex, AHI, BMI, tonsils grade, presence of rhinitis, turbinate hypertrophy, nasal septal deviation, or nasal peak inspiratory flow limitation had no influence on the effect of nasal spray. Co-phenylcaine did not significantly influence the loudness of snoring.

Conclusions

Our pilot study supports the use of co-phenylcaine nasal spray during DISE and the positive effects of the nasal spray do not influence the grading outcome. Importantly, the decongestant enhances the nasal assessment during DISE and potentially aids in the diagnosis of nasal obstruction while the nasal anaesthetic component may be beneficial by reducing nasal discomfort during DISE and thereby helping to reduce the total dose of intravenous anaesthetic administered. However, further studies on a larger population are needed to confirm our results.

Sagittal Measurement of Tongue Movement During Respiration: Comparison Between Ultrasonography and Magnetic Resonance Imaging

The tongue makes up the anterior pharyngeal wall and is critical for airway patency. Magnetic resonance imaging (MRI) is commonly used to study pharyngeal muscle function in pharyngeal disorders such as obstructive sleep apnoea. Tagged MRI and ultrasound studies have separately revealed ∼1 mm of anterior tongue movement during inspiration in healthy patients, but these modalities have not been directly compared. In the study described here, agreement between ultrasound and MRI in measuring regional tongue displacement in 21 healthy patients and 21 patients with obstructive sleep apnoea was evaluated. We found good consistency and agreement between the two techniques, with an intra-class correlation coefficient of 0.79 (95% confidence interval: 0.75-0.82) for anteroposterior tongue motion during inspiration. Ultrasound measurements of posterior tongue displacement were 0.24 ± 0.64 mm greater than MRI measurements (95% limits of agreement: 1.03 to -1.49). This may reflect the higher spatial and temporal resolution of the ultrasound technique. This study confirms that ultrasound is a suitable method for quantifying inspiratory tongue movement.

Comparison of upper airway measurement by lateral cephalogram in upright position and CBCT in supine position

Background/Purpose

Obstructive sleep apnea syndrome (OSAS) is a common form of sleep disorder. Lateral cephalograms and cone-beam computed tomography (CBCT) have been used for evaluation. However, it is lack of position comparison for these two assessments. Therefore, this study was aimed to evaluate the difference of upper airway measurements taken from lateral cephalograms in upright position and CBCT in supine position.

Material and methods

This retrospective study enrolled patients with lateral cephalograms and CBCT images due to diagnostic necessity. The anterior-posterior distance of most constricted area in pharynx (PASmin) and the distance from mandibular plane to hyoid bone (MP-H) were identified and measured from 21 normal subjects without obstructive sleep apnea (9 males and 12 females, mean age 21.2 years). A paired data were measured from lateral cephalograms taken in upright position and lateral cephalometric images derived from CBCT taken in supine position. Both images were taken within two months. All data were analyzed statistically.

Results

No significant difference was identified in intra-examiner reliability (P > 0.05). PASmin measured from lateral cephalograms in upright position was larger than that taken from CBCT derived cephalometric images, but without statistical significant difference (P = 0.073). Significant difference of MP-H length was identified between two different image taking methods (P = 0.000), and the measurement was significantly larger in cephalograms taken from upright position. No correlations were found among the variables (Body Mass Index (BMI), age, gender) in this study. The only two variables correlated were PASmin and MP-H, and they were negatively correlated (r = −0.535).

Conclusion

The anterior-posterior distance of most constricted area in pharynx (PASmin) and distance of mandibular plane to hyoid bone (MP-H) can be influenced due to change of body position.

Drug-Induced Sleep Endoscopy in Treatment Options Selection

Drug-induced sleep endoscopy is a safe and practical technique to evaluate the dynamic upper airway collapse during sleep. We review drug-induced sleep endoscopy in adults, including its indications, technique, evaluation of upper airway collapse, and clinical application. Drug-induced sleep endoscopy is useful to improve treatment options selection for patients with obstructive sleep apnea, especially for those who are unable to accept or tolerate continuous positive airway pressure therapy. Owing to a lack of standardization for drug-induced sleep endoscopy, it is difficult to compare the published literature from different sleep centers across the world.

The Effect of Sedating Agents on Drug-Induced Sleep Endoscopy Findings

OBJECTIVE

Drug-induced sleep endoscopy (DISE) has gained interest for upper airway evaluation in patients with snoring and obstructive sleep apnea (OSA), and different drugs have been used to induce sedation. Nevertheless, all drugs have presented specific advantages and disadvantages with differential effects on respiratory physiology. This study evaluated and compared the effects of midazolam, propofol and dexmedetomidine on DISE findings, O₂ nadir, and bispectral index (BIS) in the same sample of patients.

STUDY DESIGN

Case series prospective study.

METHODS

Consecutive patients who elected to undergo surgery for OSA treatment and were intolerant to conservative therapies underwent DISE with propofol, dexmedetomidine, and midazolam between July 2015 and July 2016.

RESULTS

Fifty-two patients were analyzed, and 43 (82.7%) were men. Agreement among drugs for both degree and patterns of obstruction was excellent at all sites (velum, oropharynx, and epiglottis) except for the tongue base. Dexmedetomidine had the least complete collapse sites and highest O₂ nadir and was the only drug for which apnea severity and obstruction levels (upper, lower, or combined) were correlated. The variability among drug treatments for the BIS index was considerable, and propofol had the lowest variability and average value.

CONCLUSION

Drug selection had a relevant influence in DISE findings. Compared with dexmedetomidine, midazolam and propofol presented higher incidence of tongue base collapse, lower O₂ levels, and lower BIS index values. Propofol resulted in an O₂ nadir that most resembled that observed during polysomnography. The BIS index variability differed among drugs, and its use was considered relevant for sedation orientation.

LEVEL OF EVIDENCE

4 Laryngoscope, 129:506-513, 2019.

Retropalatal and retroglossal airway compliance in patients with obstructive sleep apnea

OBJECTIVES

We hypothesized that preferential retropalatal as compared to retroglossal collapse in patients with obstructive sleep apnea was due to a narrower retropalatal area and a higher retropalatal compliance. Patients with a greater retropalatal compliance would exhibit a recognizable increase in negative effort dependence (NED).

METHODS

Fourteen patients underwent upper airway endoscopy with simultaneous recordings of airflow and pharyngeal pressure during natural sleep. Airway areas were obtained by manually outlining the lumen. Compliance was calculated by the change of airway area from end-expiration to a pressure swing of -5 cm H₂O. NED was quantified for each breath as [peak inspiratory flow minus flow at -5 cm H₂O]/[peak flow] × 100.

RESULTS

Compared to the retroglossal airway, the retropalatal airway was smaller at end-expiration (p < 0.001), and had greater absolute and relative compliances (p < 0.001). NED was positively associated with retropalatal relative area change (r = 0.47; p < 0.001).

CONCLUSIONS

Retropalatal airway is narrower and more collapsible than retroglossal airway. Retropalatal compliance is reflected in the clinically-available NED value.

The use of drug-induced sleep endoscopy in England and Belgium

Purpose

The purpose of this international survey is to ascertain the current practice of drug-induced sleep endoscopy (DISE) for patients with sleep-disordered breathing (SDB) by Otolaryngologists in the United Kingdom and Belgium. We compare the results with recommendations from the European Position Paper on drug-induced sleep endoscopy.

Methods

An online questionnaire was circulated to Consultant Otolaryngologists, independent practitioners, and trainees across the two countries. Eleven questions were used in total.

Results

181 responses from the UK and 117 responses from Belgium were received, mostly from consultants and independent practitioners. SDB was a common presentation to ENT practice, seen by over 90% of clinicians. The use of DISE varied greatly between the two countries (72.9% Belgium, 26.1% UK). 54.1% of Belgian respondents use DISE on over 50% of their patients, compared to only 32.4% of British clinicians. Attitudes of surgeons towards the diagnostic value of DISE varied; in Belgium, the majority (54%) gave a rating of 3 or more (1 = useless to 5 = essential), with no respondents giving a score of 0 (useless). In the UK only 16% of respondents felt DISE had useful clinical value, with 25 respondents deeming it ’useless’. The majority opt for DISE when non-surgical therapies fail (51.4% UK, 61.3% Belgium). The majority of participants do not use objective measures for depth of sedation (75.7% UK, 66.7% Belgium), with a marked variation on anaesthetic methods. 62.2% of UK clinicians do not use a classification system, whereas in Belgium the majority of clinicians (60.8%) use the VOTE grading system.

Conclusions

Clinicians in Belgium were more favourable to using DISE than in the UK. Differences in its clinical effectiveness were apparent between the two countries. A consensus on patient selection, method of sedation and an effective classification system seemed to be lacking from both countries. Further education is required to raise awareness for the use of DISE.

Upper Airway Areas, Volumes, and Linear Measurements Determined on Computed Tomography During Different Phases of Respiration Predict the Presence of Severe Obstructive Sleep Apnea

PURPOSE

The objective of this study was to analyze the potential of using low-dose volumetric computed tomography (CT) during different phases of respiration for identifying patients likely to have severe obstructive sleep apnea (OSA), defined as a respiratory disturbance index (RDI) higher than 30.

PATIENTS AND METHODS

A prospective study was undertaken at the Ramathibodi Hospital (Bangkok, Thailand). Patients with diagnosed OSA (N = 82) were recruited and separated into group 1 (RDI, ≤30; n = 36) and group 2 (RDI, >30; n = 46). The 2 groups were scanned by low-dose volumetric CT while they were 1) breathing quietly, 2) at the end of inspiration, and 3) at the end of expiration. Values for CT variables were obtained from linear measurements on lateral scout images during quiet breathing and from the upper airway area and volume measurements were obtained on axial cross-sections during different phases of respiration. All CT variables were compared between study groups. A logistic regression model was constructed to calculate a patient's likelihood of having an RDI higher than 30 and the predictive value of each variable and of the final model.

RESULTS

The minimum cross-sectional area (MCA) measured at the end of inspiration (cutoff point, ≤0.33 cm²) was the most predictive variable for the identification of patients likely to have an RDI higher than 30 (adjusted odds ratio [OR] = 5.50; 95% confidence interval [CI], 1.76-17.20; sensitivity, 74%; specificity, 72%,), followed by the MCA measured at the end of expiration (cutoff point, ≤0.21 cm²; adjusted OR = 3.28; 95% CI, 1.05-10.24; sensitivity, 70%; specificity, 68%).

CONCLUSION

CT scanning at the ends of inspiration and expiration helped identify patients with an RDI higher than 30 based on measurement of the MCA. Low-dose volumetric CT can be a useful tool to help the clinician rapidly identify patients with severe OSA and decide on the urgency to obtain a full-night polysomnographic study and to start treatment.

Computed Tomography Characterization and Comparison With Polysomnography for Obstructive Sleep Apnea Evaluation

PURPOSE

We hypothesized that computed tomography (CT) combined with portable polysomnography (PSG) might better visualize anatomic data related to obstructive sleep apnea (OSA). The present study evaluated the CT findings during OSA and assessed their associations with the PSG data and patient characteristics.

PATIENTS AND METHODS

We designed a prospective cross-sectional study of patients with OSA. The patients underwent scanning during the awake state and apneic episodes. Associations of the predictor variables (ie, PSG data, respiratory disturbance index [RDI]), patient characteristics (body mass index [BMI], neck circumference [NC], and waist circumference [WC]), and outcome variables (ie, CT findings during apneic episodes) were assessed using logistic regression analysis. The CT findings during apneic episodes were categorized regarding the level of obstruction, single level (retropalatal [RP] or retroglossal [RG]) or multilevel (mixed RP and RG), degree of obstruction (partial or complete), and pattern of collapse (complete concentric collapse [CCC] or other patterns).

RESULTS

A total of 58 adult patients with OSA were scanned. The mean ± standard deviation for the RDI, BMI, NC, and WC were 41.6 ± 28.55, 27.80 ± 5.43 kg/m², 38.3 ± 4.3 cm, and 93.8 ± 13.6 cm, respectively. No variables distinguished between the presence of single- and multilevel airway obstruction in the present study. A high RDI (≥30) was associated with the presence of complete obstruction and CCC (odds ratio 6.33, 95% confidence interval 1.55 to 25.90; and odds ratio 3.77, 95% confidence interval 1.02 to 13.91, respectively) compared with those with a lesser RDI.

CONCLUSIONS

An increased RDI appears to be an important variable for predicting the presence of complete obstruction and CCC during OSA. Scanning during apneic episodes, using low-dose volumetric CT combined with portable PSG provided better anatomic and pathologic findings of OSA than did scans performed during the awake state.

New algorithm for semiautomatic segmentation of nasal cavity and pharyngeal airway in comparison with manual segmentation using cone-beam computed tomography

INTRODUCTION

Our objectives were to assess reliability, validity, and time efficiency of semiautomatic segmentation using Segura software of the nasal and pharyngeal airways, against manual segmentation with point-based analysis with color mapping.

METHODS

Pharyngeal and nasal airways from 10 cone-beam computed tomography image sets were segmented manually and semiautomatically using Segura (University of Alberta, Edmonton, Alberta, Canada). To test intraexaminer and interexaminer reliabilities, semiautomatic segmentation was repeated 3 times by 1 examiner and then by 3 examiners. In addition to volume and surface area, point-based analysis was completed to assess the reconstructed 3-dimensional models from Segura against manual segmentation. The times of both methods of segmentation were also recorded to assess time efficiency.

RESULTS

The reliability and validity of Segura were excellent (intraclass correlation coefficient, >0.9 for volume and surface area). Part analysis showed small differences between the Segura and manually segmented 3-dimensional models (greatest difference did not exceed 4.3 mm). Time of segmentation using Segura was significantly shorter than that for manual segmentation, 49 ± 11.0 vs 109 ± 9.4 minutes (P <0.001).

CONCLUSIONS

Semiautomatic segmentation of the pharyngeal and nasal airways using Segura was found to be reliable, valid, and time efficient. Part analysis with color mapping was the key to explaining differences in upper airway volume and provides meaningful and clinically relevant analysis of 3-dimensional changes.

Velopharyngeal mucosal surface topography in healthy subjects and subjects with obstructive sleep apnea

Macroscopic pharyngeal anatomical abnormalities are thought to contribute to the pathogenesis of upper airway (UA) obstruction in obstructive sleep apnea (OSA). Microscopic changes in the UA mucosal lining of OSA subjects are reported; however, the impact of these changes on UA mucosal surface topography is unknown. This study aimed to 1) develop methodology to measure UA mucosal surface topography, and 2) compare findings from healthy and OSA subjects. Ten healthy and eleven OSA subjects were studied. Awake, gated (end expiration), head and neck position controlled magnetic resonance images (MRIs) of the velopharynx (VP) were obtained. VP mucosal surfaces were segmented from axial images, and three-dimensional VP mucosal surface models were constructed. Curvature analysis of the models was used to study the VP mucosal surface topography. Principal, mean, and Gaussian curvatures were used to define surface shape composition and surface roughness of the VP mucosal surface models. Significant differences were found in the surface shape composition, with more saddle/spherical and less flat/cylindrical shapes in OSA than healthy VP mucosal surface models (P < 0.01). OSA VP mucosal surface models were also found to have more mucosal surface roughness (P < 0.0001) than healthy VP mucosal surface models. Our novel methodology was utilized to model the VP mucosal surface of OSA and healthy subjects. OSA subjects were found to have different VP mucosal surface topography, composed of increased irregular shapes and increased roughness. We speculate increased irregularity in VP mucosal surface may increase pharyngeal collapsibility as a consequence of friction-related pressure loss.NEW & NOTEWORTHY A new methodology was used to model the upper airway mucosal surface topography from magnetic resonance images of patients with obstructive sleep apnea and healthy adults. Curvature analysis was used to analyze the topography of the models, and a new metric was derived to describe the mucosal surface roughness. Increased roughness was found in the obstructive sleep apnea vs. healthy group, but further research is required to determine the functional effects of the measured difference on upper airway airflow mechanics.

Opioid Toxicity

In recent years, there has been a substantial increase in opioid use and abuse, and in opioid-related fatal overdoses. The increase in opioid use has resulted at least in part from individuals transitioning from prescribed opioids to heroin and fentanyl, which can cause significant respiratory depression that can progress to apnea and death. Heroin and fentanyl may be used individually, together, or in combination with other substances such as ethanol, benzodiazepines, or other drugs that can have additional deleterious effects on respiration. Suspicion that a death is drug-related begins with the decedent's medical and social history, and scene investigation, where drugs and drug paraphernalia may be encountered, and examination of the decedent, which may reveal needle punctures and needle track marks. At autopsy, the most significant internal finding that is reflective of opioid toxicity is pulmonary edema and congestion, and frothy watery fluid is often present in the airways. Various medical ailments such as heart and lung disease and obesity may limit an individual's physiologic reserve, rendering them more susceptible to the toxic effects of opioids and other drugs. Although many opioids will be detected on routine toxicology testing, more specialized testing may be warranted for opioid analogs, or other uncommon, synthetic, or semisynthetic drugs.

Cephalometrics of Pharyngeal Airway Space in Lebanese Adults

Purpose. The upper airway space is significant in orthodontic diagnosis and treatment planning. The objectives of this study are to assess the dimensions of soft tissue elements of the upper pharyngeal space and evaluate potential correlations with modifying variables such as gender, skeletal class, and anthropometric parameters. Materials and Methods. Lateral cephalograms were obtained from 117 healthy young adult Lebanese subjects. Nineteen cephalometric linear/angular measurements of the nasopharynx, oropharynx, and hypopharynx were recorded. Anthropometric parameters including body mass index and neck circumference were measured. Results. Significant differences were demonstrated for 12 out of the 19 parameters considered between genders. Uvula and tongue dimensions and the distances between epiglottis-posterior pharyngeal wall and epiglottis-posterior nasal spine were significantly larger in males. The anteroposterior inclination of the uvula and the distances between the uvula and posterior pharyngeal wall were significantly greater in females. No significant differences were found between skeletal classes relative to most of the variables. Body mass index and neck circumference were positively correlated with the dimensions of tongue and uvula. Conclusions. Sexual dimorphism relative to some cephalometric variables and anthropometric parameters may account partly for larger oronasopharyngeal spaces in females. Anthropometric data need to be accounted for in population-related comparisons.

Investigation of the Upper Airway Anatomy With Ultrasound

OBJECTIVE

The aims of this study were to describe the relationship between the scanning planes and appearance of the upper airway on sonography and to demonstrate the reliability and reproducibility of sonographic measurements of the upper airway.

METHODS

Airway sonoanatomy was recognized by comparing the airway images and the corresponding cadaver's anatomical specimens. Systemic sonographic examination of 267 healthy volunteers was conducted to obtain the sonographic measurement of airway lumen. The reliability and reproducibility studies were conducted in 40 healthy volunteers.

RESULT

The air-filled upper airway appeared as a bright heterogeneous hyperechoic line. During deep inspiration, the upper airway lumen expanded to the highest anterior-posterior dimension, whereas during deep expiration, the lateral dimension tended to increase. The sonographic measurements had good reproducibility, with intraclass correlation coefficient ranging from 0.722 to 0.887 and 0.727 to 0.882 for interobserver and intraobserver reliability, respectively.

CONCLUSIONS

Ultrasonography can determine the anatomy of the upper airway and perform the quantitative analysis of the upper airway lumen during respiration. The results were encouraging and support the utility of ultrasonography in future airway disorder studies.

Three-dimensional imaging of the upper airway anatomy in obstructive sleep apnea: a systematic review

INTRODUCTION

The pathogenesis of upper airway collapse in people with obstructive sleep apnea (OSA) is not fully understood. The aim of this study was to systematically review the literature in order to assess the most relevant anatomical characteristics of the upper airway related to the pathogenesis of OSA by analyzing the three-dimensional upper airway anatomy.

METHOD

A PICO (population/patient, intervention, comparison, outcome) search strategy, focusing on the upper airway anatomy of people with OSA, was conducted using the following databases: MEDLINE (PubMed), Excerpta Medica database (EMBASE), Web of Science, and Cochrane Library. The studies in which three-dimensional images were made from the participants who were awake and in the supine position during quiet breathing were selected in this systematic review.

RESULTS

Of the 758 unique retrieved studies, eight fulfilled the criteria for this systematic review. The minimum cross-sectional area of the upper airways of people with OSA, which is influenced by many factors such as hard and soft tissues surrounding the upper airway, was significantly smaller than that of those without OSA.

CONCLUSION

Within the limitation of the selected studies, this systematic review suggested that a small minimum cross-sectional area is the most relevant anatomical characteristic of the upper airway related to the pathogenesis of OSA.

How has our interest in the airway changed over 100 years?

Since the beginning of our specialty, our understanding of the link between function and facial growth and development has progressively improved. Today, we know that children with sleep-related breathing problems will often develop distinctive facial characteristics. In adults, sleep apnea can result in serious morbidity and mortality. Orthodontists can ask sleep-related questions in the health history to help identify sleep breathing disorders. Treating these patients presents unique opportunities for orthodontists to collaborate with other medical specialties to improve a patient's health and treatment outcome. Research presented in our Journal in the next century may shed new light that will help us better identify the problem and aid the specialty in developing more effective evidence-based treatment. Additional efforts are needed to understand the physiology, neurology, and genetics of sleep breathing disorders.

Dynamic 3-D MR Visualization and Detection of Upper Airway Obstruction During Sleep Using Region-Growing Segmentation

GOAL

We demonstrate a novel and robust approach for visualization of upper airway dynamics and detection of obstructive events from dynamic 3-D magnetic resonance imaging (MRI) scans of the pharyngeal airway.

METHODS

This approach uses 3-D region growing, where the operator selects a region of interest that includes the pharyngeal airway, places two seeds in the patent airway, and determines a threshold for the first frame.

RESULTS

This approach required 5 s/frame of CPU time compared to 10 min/frame of operator time for manual segmentation. It compared well with manual segmentation, resulting in Dice Coefficients of 0.84 to 0.94, whereas the Dice Coefficients for two manual segmentations by the same observer were 0.89 to 0.97. It was also able to automatically detect 83% of collapse events.

CONCLUSION

Use of this simple semiautomated segmentation approach improves the workflow of novel dynamic MRI studies of the pharyngeal airway and enables visualization and detection of obstructive events.

SIGNIFICANCE

Obstructive sleep apnea (OSA) is a significant public health issue affecting 4-9% of adults and 2% of children. Recently, 3-D dynamic MRI of the upper airway has been demonstrated during natural sleep, with sufficient spatiotemporal resolution to noninvasively study patterns of airway obstruction in young adults with OSA. This study makes it practical to analyze these long scans and visualize important factors in an MRI sleep study, such as the time, site, and extent of airway collapse.

Correlation Between Retropalatal Collapse as Observed During Muller's Maneuver to Severity of OSA

Objective of the study was to evaluate the reliability of Muller's maneuver (MM) with the severity of obstructive sleep apnea (OSA) at the retropalatal level. Case series of 58 adult patients diagnosed to have OSA. Sleep apnoea clinic in a tertiary referral center in south India. Fifty-eight adult OSA patients underwent outpatient based MM under local anaesthesia. Collapse of hypopharynx and the retroglossal regions were assessed during a maximal inspiratory effort against the closed mouth and sealed nose (reverse valsalva). Correlation co efficient was used to compare MM grade with apnea-hypopnea index (AHI) scores. Severity of OSA based on AHI scores were compared with the results of Muller's maneuver at the retropalatal level. The correlation coefficient was 0.213, hence no correlation was found, p value was 0.019, which was not statistically significant. MM is an useful tool for evaluation of upper airway collapse. The advantages include simplicity, cost-effectiveness, relatively easy to perform, thorough evaluation of upper airway. The pitfalls of the procedure includes the subjectiveness of the procedure and the fact that it is performed on awake patients and therefore remains an indirect estimation of obstruction that occurs during sleep. In our study, we did not find correlation between the severity of OSA based on the AHI scores and the collapse at the retropalate level assessed by the Muller's maneuver.

Surgical results of different palate techniques to treat oropharyngeal collapse

The aim of this study was to assess the surgical success rate of patients undergoing oropharyngeal surgery, selected through drug-induced sleep endoscopy. Secondly, to compare outcomes of the different oropharyngeal surgery techniques applied. The study design was retrospective case series of surgically treated patients from 2006 to 2013. All patients were diagnosed with either moderate or severe obstructive sleep apnea and did not tolerate conventional positive airway pressure. We performed five different surgical techniques to treat oropharyngeal collapse: partial palate resection, uvulopalatopharyngoplasty, Z-palatoplasty, lateral pharyngoplasty and expansion pharyngoplasty. Patients in whom multilevel surgery was performed were excluded. 53 patients were included in our study, 52.8 % were severe obstructive sleep apnea patients, mean age was 43.9 years, mean body mass index 27.5. The surgical success rate according to Sher's criteria was 71.7 %. 47.2 % had a postoperative apnea hypopnea index lower than 10. The highest success rate was measured in patients who underwent expansion pharyngoplasty (90 % according to Sher's criteria, 80 % with a postoperative apnea hypopnea index lower than 10) although it did not reach statistical significance. Our conclusion is that drug-induced sleep endoscopy is a good tool to select surgical candidates in patients with moderate-to-severe obstructive sleep apnea who are not compliant with the optimal therapy. Expansion pharyngoplasty was the surgical technique with the highest success rates.

Pharyngeal mucosal wall folds in subjects with obstructive sleep apnea

Mechanical processes underlying pharyngeal closure have not been examined. We hypothesized that the pharyngeal mucosal surface would fold during closure, and lowering the upper airway lining liquid surface tension would unfold areas of mucosal apposition, i.e., folds. We compared baseline pharyngeal fold numbers and response to reduction in upper airway liquid surface tension in healthy and obstructive sleep apnea (OSA) subjects. Awake, gated magnetic resonance pharyngeal airway images of 10 healthy and 11 OSA subjects were acquired before and after exogenous surfactant administration (beractant). Upper airway liquid surface tension was measured at the beginning and end of image acquisition and averaged. Velopharyngeal and oropharyngeal images were segmented and analyzed separately for average cross-sectional area, circumference, and fold number. Compared with healthy subjects, at baseline, velopharynx for OSA subjects had a smaller cross-sectional area (98.3 ± 32.5 mm(2) healthy, 52.3 ± 23.6 mm(2) OSA) and circumference (46.5 ± 8.1 mm healthy, 30.8 ± 6.1 mm OSA; both P < 0.05, unpaired t-test), and fewer folds (4.9 ± 1.6 healthy, 3.1 ± 1.8 OSA, P < 0.03). There were no differences in oropharynx for cross-sectional area, circumference, or folds. Reduction in upper airway liquid surface tension from 61.3 ± 1.2 to 55.3 ± 1.5 mN/m (P < 0.0001) did not change cross-sectional area or circumference for velopharynx or oropharynx in either group; however, in OSA subjects, oropharyngeal folds fell from 6.8 ± 3.1 to 4.7 ± 1.2 (n = 8, P < 0.05), and velopharyngeal folds from 3.3 ± 1.9 to 2.3 ± 1.2 (P = 0.08), and were unchanged in healthy subjects. Subjects with OSA have fewer velopharyngeal wall folds, which decrease further when surface tension falls. We speculate that reduced pharyngeal wall folds contribute to an increase in pharyngeal collapsibility.

Variability in Nose-to-Lung Aerosol Delivery

Nasal delivery of lung targeted pharmaceutical aerosols is ideal for drugs that need to be administered during high flow nasal cannula (HFNC) gas delivery, but based on previous studies losses and variability through both the delivery system and nasal cavity are expected to be high. The objective of this study was to assess the variability in aerosol delivery through the nose to the lungs with a nasal cannula interface for conventional and excipient enhanced growth (EEG) delivery techniques. A database of nasal cavity computed tomography (CT) scans was collected and analyzed, from which four models were selected to represent a wide range of adult anatomies, quantified based on the nasal surface area-to-volume ratio (SA/V). Computational fluid dynamics (CFD) methods were validated with existing in vitro data and used to predict aerosol delivery through a streamlined nasal cannula and the four nasal models at a steady state flow rate of 30 L/min. Aerosols considered were solid particles for EEG delivery (initial 0.9 μm and 1.5 μm aerodynamic diameters) and conventional droplets (5 μm) for a control case. Use of the EEG approach was found to reduce depositional losses in the nasal cavity by an order of magnitude and substantially reduce variability. Specifically, for aerosol deposition efficiency in the four geometries, the 95% confidence intervals (CI) for 0.9 and 5 μm aerosols were 2.3-3.1 and 15.5-66.3%, respectively. Simulations showed that the use of EEG as opposed to conventional methods improved delivered dose of aerosols through the nasopharynx, expressed as penetration fraction (PF), by approximately a factor of four. Variability of PF, expressed by the coefficient of variation (CV), was reduced by a factor of four with EEG delivery compared with the control case. Penetration fraction correlated well with SA/V for larger aerosols, but smaller aerosols showed some dependence on nasopharyngeal exit hydraulic diameter. In conclusion, results indicated that the EEG technique not only improved lung aerosol delivery, but largely eliminated variability in both nasal depositional loss and lung PF in a newly developed set of nasal airway models.

Upper airway collapsibility is associated with obesity and hyoid position

STUDY OBJECTIVES

Upper airway anatomy plays a major role in obstructive sleep apnea (OSA) pathogenesis. An inferiorly displaced hyoid as measured by the mandibular plane to hyoid distance (MPH) has been consistently associated with OSA. The hyoid is also a common landmark for pharyngeal length, upper airway volume, and tongue base. Tongue dimensions, pharyngeal length, and obesity are associated with OSA severity, although the link between these anatomical variables and pharyngeal collapsibility is less well known. We hypothesized that obesity as measured by body mass index (BMI), neck and waist circumferences, and variables associated with hyoid position (pharyngeal length, upper airway volume, and tongue dimensions) would be associated with passive pharyngeal critical closing pressure (Pcrit).

DESIGN

Cross-sectional.

SETTING

Academic hospital.

PATIENTS

34 Japanese-Brazilian males age 21 to 70 y.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

We performed computed tomography scans of the upper airway, overnight polysomnography, and Pcrit measurements in all subjects. On average, subjects were overweight (BMI = 28 ± 4 kg/m(2)) and OSA was moderately severe (apnea-hypopnea index = 29 [13-51], range 1-90 events/h). Factor analysis identified two factors among the studied variables: obesity (extracted from BMI, neck and waist circumferences) and hyoid position (MPH, pharyngeal length, tongue length, tongue volume, and upper airway volume). Both obesity and hyoid position correlated with Pcrit (r = 0.470 and 0.630, respectively) (P < 0.01). In addition, tongue volume, tongue length, pharyngeal length, and MPH correlated with waist and neck circumferences (P < 0.05).

CONCLUSIONS

Pharyngeal critical closing pressure is associated with obesity and hyoid position. Tongue dimensions, pharyngeal length, and the mandibular plane to hyoid distance are associated with obesity variables. These findings provide novel insight into the potential factors mediating upper airway collapse in obstructive sleep apnea.