Positional changes of oropharyngeal structures due to gravity in the upright and supine positions

The use of CBCT in orthodontics with special focus on upper airway analysis in patients with sleep-disordered breathing

Applications of cone-beam CT (CBCT) in orthodontics have been increasingly discussed and evaluated in science and practice over the last two decades. The present work provides a comprehensive summary of current consolidated practice guidelines, cutting-edge innovative applications, and future outlooks about potential use of CBCT in orthodontics with a special focus on upper airway analysis in patients with sleep-disordered breathing. The present scoping review reveals that clinical applications of CBCT in orthodontics are broadly supported by evidence for the diagnosis of dental anomalies, temporomandibular joint disorders, and craniofacial malformations. On the other hand, CBCT imaging for upper airway analysis-including soft tissue diagnosis and airway morphology-needs further validation in order to provide better understanding regarding which diagnostic questions it can be expected to answer. Internationally recognized guidelines for CBCT use in orthodontics are existent, and similar ones should be developed to provide clear indications about the appropriate use of CBCT for upper airway assessment, including a list of specific clinical questions justifying its prescription.

Prediction of Pharyngeal 3D Volume Using 2D Lateral Area Measurements During Swallowing

This study evaluated the validity of pharyngeal 2D area measurements acquired from the lateral view for predicting the actual 3D volume in healthy adults during swallowing. Seventy-five healthy adults (39 females, 36 males; mean age 51.3 years) were examined using 320-row area detector computed tomography (320-ADCT). All participants swallowed a 10 mL honey-thick barium bolus upon command while seated in a 45° semi-reclining position. Multi-planar reconstruction images and dynamic 3D-CT images were obtained using Aquilion ONE software. Pharyngeal 2D area and 3D volume measurements were taken before swallowing and at the frame depicting maximum pharyngeal constriction. Pharyngeal volume before swallowing (PVhold) was accurately predicted by 2D area (R2 = 0.816). Adding height and sex to the model increased R2 to 0.836. Regarding pharyngeal volume during maximum constriction (PVmax), 2D area also exhibited acceptable predictive power (R2 = 0.777). However, analysis of statistical residuals and outliers revealed a greater tendency for prediction errors when there is less complete constriction of the pharynx as well as asymmetry in bolus flow or movement. Findings highlight the importance of routinely incorporating anterior-posterior views during VFSS exams. Future work is needed to determine clinical utility of pharyngeal volume measurements derived from 320-ADCT.

The relationship between aerodynamic characteristics of the upper airway and severity of obstructive sleep apnea in adults

OBJECTIVE

To investigate the relationship between aerodynamic characteristics of the upper airway and severity of obstructive sleep apnea (OSA) in adults.

METHODS

Ninety-seven adult OSA patients underwent polysomnography and cone beam computed tomography (CBCT). The anatomical and aerodynamic characteristics were measured based on CBCT images and computational fluid dynamics modelling of the upper airway.

RESULTS

After controlling for patients' gender, age, and body mass index (BMI), the maximum velocity during inspiration (In-Vmax) led to the largest increase in the explanatory power of apnea-hypopnea index (AHI) variation. The In-Vmax was closely correlated with the minimum axial area, and their relationship was represented by an inversely proportional fitted curve.

CONCLUSIONS

The In-Vmax was the most relevant to OSA severity, and it could be used to assist in recognizing severe OSA patients and as a primary variable to evaluate treatment outcomes of OSA. The In-Vmax was closely related to the most constricted area of the upper airway.

Volumetric changes in the upper airway on CBCT after dentofacial orthopedic interventions - a systematic review

OBJECTIVE

To provide a critical overview of the effect of various orthodontic and/or dentofacial orthopedic interventions on three-dimensional volumetric changes in the upper airway.

MATERIALS AND METHODS

Four databases were searched for clinical studies concerning 3D volumetric assessments based on CBCT before and after orthodontics interventions. The quality of the studies was assessed using the quality assessment tool of the National Heart, Lung and Blood Institute. After the use of inclusion and exclusion criteria, the pre-and post-treatment volumes were used to visualize the effect of various orthodontics interventions.

RESULTS

A total of 48 studies were included in this review and none of which were RCTs. The quality of all included studies was assessed as medium. Overall, there is a tendency for an increase in airway volumes after various orthodontic interventions, except for studies concerning extraction therapy with fixed appliances in adults, in which both increases and decreases in airway volumes have been reported.

CONCLUSION

Orthodontic treatment by growth modification and non-extraction therapy with fixed appliances, regardless of the malocclusion, generally showed positive effects on the airway volume. Orthodontic treatment in combination with extractions does not provide an unambiguous insight. A consensus on the methodology of the airway measurement and nomenclature is urgently needed in order to gain insight into the effect of different interventions on three-dimensional airway changes.

CLINICAL RELEVANCE

Various orthodontic treatments do not negatively influence the upper airway volume. However, extraction therapy in adults should be chosen with caution, especially in subjects belonging to a group susceptible to airway obstruction.

A systematic review of the techniques for automatic segmentation of the human upper airway using volumetric images

The human upper airway is comprised of many anatomical volumes. The obstructions in the upper airway volumes are needed to be diagnosed which requires volumetric segmentation. Manual segmentation is time-consuming and requires expertise in the field. Automatic segmentation provides reliable results and also saves time and effort for the expert. The objective of this study is to systematically review the literature to study various techniques used for the automatic segmentation of the human upper airway regions in volumetric images. PRISMA guidelines were followed to conduct the systematic review. Four online databases Scopus, Google Scholar, PubMed, and JURN were used for the searching of the relevant papers. The relevant papers were shortlisted using inclusion and exclusion eligibility criteria. Three review questions were made and explored to find their answers. The best technique among all the literature studies based on the Dice coefficient and precision was identified and justified through the analysis. This systematic review provides insight to the researchers so that they shall be able to overcome the prominent issues in the field identified from the literature. The outcome of the review is based on several parameters, e.g., accuracy, techniques, challenges, datasets, and segmentation of different sub-regions. Flowchart of the search process as per PRISMA guidelines along with inclusion and exclusion criteria.

Three-Dimensional Evaluation Effects of Microimplant-Assisted Rapid Palatal Expansion on the Upper Airway Volume: A Systematic Review and Meta-Analysis

Microimplant-assisted rapid palatal expansion is increasingly used clinically; however, the effect on the upper airway volume in patients with maxillary transverse deficiency has not been thoroughly evaluated yet. The following electronic databases were searched up to August 2022: Medline via Ovid, Scopus, Embase, Web of Science, Cochrane Library, Google Scholar, and ProQuest. The reference lists of related articles were also reviewed by manual search. The Revised Cochrane Risk of Bias Tool for randomized trials (ROB2) and the Risk of Bias in non-randomized Studies of Interventions (ROBINS-I) tool were used to evaluate the risks of bias of the included studies. The mean differences (MD) and 95% confidence intervals (CI) of changes in nasal cavity and upper airway volume were analyzed using a random-effects model, and subgroup and sensitivity analyses were also performed. Two reviewers independently completed the process of screening studies, extracting data, and assessing the quality of studies. In total, twenty-one studies met the inclusion criteria. After assessing the full texts, only thirteen studies were included, with nine studies selected for quantitative synthesis. Oropharynx volume increased significantly after immediate expansion (WMD: 3156.84; 95% CI: 83.63, 6230.06); however, there was no significant change in nasal volume (WMD: 2527.23; 95% CI: -92.53, 5147.00) and nasopharynx volume (WMD: 1138.29; 95% CI: -52.04, 2328.61). After retention a period, significant increases were found in nasal volume (WMD: 3646.27; 95% CI: 1082.77, 6209.77) and nasopharynx volume (WMD: 1021.10; 95% CI: 597.11, 1445.08). However, there was no significant change after retention in oropharynx volume (WMD: 789.26; 95% CI: -171.25, 1749.76), palatopharynx volume (WMD: 795.13; 95% CI: -583.97, 2174.22), glossopharynx volume (WMD: 184.50; 95% CI: -1745.97, 2114.96), and hypopharynx volume (WMD: 39.85; 95% CI: -809.77, 889.46). MARPE appears to be linked with long-term increases in nasal and nasopharyngeal volume. However, high-quality clinical trials are required to further verify the effects of MARPE treatment on the upper airway.

Ultrasound Evaluation to Predict Difficult Laryngoscopy in Children below 2 Years

OBJECTIVE

To evaluate the feasibility of sonography as a tool to predict difficult airway in children less than 2 y of age.

METHODS

Airway ultrasound was performed in 90 children below the age of 2 y to measure airway dimensions preoperatively. Hyomental distance ratio in predicting difficult laryngoscopy was recorded as the primary outcome. Secondary outcomes included tongue thickness/oral cavity thickness ratio and tongue thickness/thyromental distance ratio in predicting difficult laryngoscopy and difficult intubation, time taken for intubation, and any complications. The sensitivity, specificity, positive predictive value, and negative predictive value with 95% CI of all the parameters were recorded.

RESULTS

Six out of 90 (6.7%) patients had difficult laryngoscopy. HMDR was significantly different between children with easy and difficult laryngoscopy (1.15 ± 0.11 vs. 1.03 ± 0.016, p = 0.001). The optimal cutoff points for HMDR, TT/OCT, and TT/TMD to predict difficult laryngoscopy (CL grade III, IV) were > 1.055 (sensitivity 100%, specificity 86.9%), 0.755 (sensitivity 100%, specificity 57%), and 0.445 (sensitivity 53.5%, specificity 66.7%), respectively, the AUC being highest for HMDR (0.959). The cutoff value of ≥ 1.055 of HMDR to predict difficult laryngoscopy had the highest AUC of 0.959, p < 0.001. Fifty-two children had IDS = 0, while 38 had IDS between 1 and 4. None of the patients had IDS > 5.

CONCLUSIONS

Ultrasound-guided airway assessment is a feasible option in children less than 2 y. Hyomental distance ratio can form a useful tool for predicting difficult airway in this age group.

TRIAL REGISTRATION

The trial has been registered in Clinical trial Registry of India (CTRI/2019/05/019014) before enrollment of the first patient.

Volumetric measurement of the tongue and oral cavity with cone-beam computed tomography: A systematic review

Purpose

The goal of this systematic review was to compare the use of cone-beam computed tomography (CBCT) with that of computed tomography (CT) for volumetric evaluations of the tongue and oral cavity.

Materials and Methods

A search for articles was conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta-analyses guidelines. The PubMed, Scopus, ScienceDirect, and SAGE Journals databases were searched for articles published between 2011 and 2021. Articles were screened and assessed for eligibility. Screening involved checking for duplication, reading the title and abstract, and reading the full text.

Results

The initial search retrieved 25,780 articles. Application of the eligibility criteria yielded 16 articles for qualitative analysis. Multiple uses of CBCT were identified. In several studies, researchers assessed the volumetric correlation between tongue and oral cavity volumes, as well as other parameters. Post-treatment volumetric evaluations of the oral cavity were also reported, and the reliability of CBCT was assessed. The use of CT resembled that of CBCT.

Conclusion

CBCT has been used in the evaluation of tongue and oral cavity volumes to assess correlations between those volumes and with the upper airway. It has also been used for volumetric evaluation after surgical and non-surgical procedures and to assess the relationships between tongue volume, tooth position, occlusion, and body mass index. Participants with obstructive sleep apnea and malocclusion have been evaluated, and the reliability of CBCT has been assessed. In the included studies, CT was utilized for similar purposes as CBCT, but its reliability was not assessed.

Retrospective study on the pharyngeal airspace in the lateral cephalogram - A mathematical model to predict changes due to bimaxillary orthognathic surgery

The aim of this study was the development of a statistical model for reliable prediction of Posterior Airway Space (PAS) changes in lateral cephalograms (LCR) of patients after bimaxillary orthognathic surgery. The LCRs of patients who underwent bimaxillary orthognathic surgery were retrospectively analyzed. The anteroposterior dimension of the PAS was measured at three levels in the pre-operative and postoperative LCR: On the nasopharyngeal (SPAS), oropharyngeal (MAS), and hypopharyngeal level (IAS). The data of 139 patients were collected. The following changes of the PAS were measured: in class II patients SPAS: 0.291 mm (SD = 2.570 mm); MAS: 2.444 mm (SD = 2.986 mm); IAS: 0.750 mm (SD = 3.017 mm); in class III patients SPAS: 1.377 mm (SD 3.212 mm); MAS: 0.962 (SD: = 3.135 mm); IAS: 0.370 mm (SD = 3.468 mm). Linear regression analysis showed for class II patients, a significant influence of mandibular movement on MAS (p = 0.049) and a significant effect of maxillary and mandibular movements on SPAS (p = 0.001) and MAS (p = 0.022) in class III patients. The other jaw displacements had no significant impact on the investigated PAS levels. While the presented method does not permit exact prediction of the dimension of the PAS, it is still an easily accessible method of orientation for the surgeon. The surgeon can initiate three-dimensional examinations to provide exact three-dimensional prediction based on this calculation.

Cone beam computed tomography volumetric airway changes after orthognathic surgery: a systematic review

The aim of this systematic review was to provide a structured overview of three-dimensional airway volume changes in relation to various orthognathic surgeries. Clinical human studies performing pre- and postoperative three-dimensional airway volume assessments to investigate volumetric changes of the airway after orthognathic surgery were included. Pre-determined inclusion and exclusion criteria were applied in an extensive search of the PubMed, Embase, and Web of Science electronic databases. The cut-off date was set to January 1, 2022. Forty-one articles reporting retrospective and prospective case-control and case series studies were included. All studies were determined to be of medium quality (moderate risk of bias). The included studies were categorized by type of intervention. Pre- and postoperative volumes were extracted from the available data, and volume changes as a percentage of the preoperative levels were calculated. Isolated mandibular setback surgery generally decreased the airway volume. Isolated maxillary or mandibular advancement, bimaxillary advancement, and surgically assisted maxillary expansion generally increased the airway volume in the total airway and oropharynx, among which the effect of bimaxillary advancement surgery appeared most significant. High heterogeneity exists in the terminology and definitions of the airway and its segments. A more uniform methodology for airway volume measurement is needed to provide an insight into the impact on the airway of specific types of surgical intervention. In conclusion, airway volumes are affected after orthognathic surgery, which may be of clinical significance, especially in patients who are predisposed to obstructive sleep apnoea.

A Cross-Sectional Study on Hyomental Distance Ratio (HMDR) as a New Predictor of Difficult Laryngoscopy in ICU Patients

Background: Intubation in the ICU is sometimes unpredictable unlike in an operation theatre, where pre-anesthetic assessment for airway has been done. This study has been done to evaluate the usefulness of hyomental distance ratio (HMDR) in accurately predicting difficult laryngoscopy in ICU patients.

Methods: In this study, 104 critically ill patients in the age group 18-70 years, undergoing tracheal intubation in ICU were included. A hard plastic ruler was pressed on the skin surface just above the hyoid bone and the distance to the tip of the anterior-most part of the mentum measured was defined as hyomental distance (HMD). HMD was assessed in neutral and extended head positions, and the HMDR was calculated. All patients were sedated, pre-oxygenated, induced, and relaxed prior to glottic visualization by direct laryngoscopy, which was performed by an experienced anesthetist. Cormack-Lehane's (CL's) grade was assessed without external laryngeal manipulation. Further management was as per ICU protocol.

Results: Using the Chi-Square test for statistical analysis, a p-value of HMDR in assessing difficult laryngoscopy was found to be <0.001 suggesting strong significance. HMD in the extended head position (HDMe) showed moderate significance with a p-value of 0.047. HMDR <1.2 can be considered a clinically reliable individual predictor of difficult laryngoscopy in ICU patients.

Conclusion: HMDR <1.2 can be used as a simple, easy, and reliable bedside test to predict difficult laryngoscopy amongst ICU patients. An optimal combination of tests is suggested if feasible for better accuracy. 

Effects of head positions on awake fiberoptic bronchoscope oral intubation: a randomized controlled trial

Background

There are many factors affecting the success rate of awake orotracheal intubation via fiberoptic bronchoscope. We performed this study was to investigate the effects of head positions on awake Fiberoptic bronchoscope oral intubation.

Methods

Seventy-five adult patients, received general anaesthesia were included in this study. After written informed consent, these patients were undergoing awake orotracheal intubation via fiberoptic-bronchoscope and according to the head position, the patients were randomized allocated to neutral position group (NP group), sniffing position group (SP group) or extension position group (EP group). After sedation the patients were intubated by an experienced anesthesiologist. The time to view the vocal cords, the percentage of glottic opening scores (POGO), the time to insert the tracheal tube into trachea and the visual analog scale (VAS) scores for ease experienced of passing the tracheal tube through glottis, the hemodynamic changes and the adverse events after surgery were recorded.

Results

The time to view the vocal cords was significantly shorter and the POGO scores was significantly higher in the EP group compared with the other two groups (P < 0.05); The SpO₂ in the EP group was higher than NP group at before intubation and higher than SP group and NP group at immediate after intubation (P < 0.05); The time to insert the tracheal tube into trachea, the VAS scores for passing the tracheal tube through glottis, the coughing scores had no significant differences among groups (P > 0.05). There were also no significant differences regard to the incidence of postoperative complications, mean arterial pressure and heart rate among the groups (P > 0.05).

Conclusions

The head at extension position had a best view of glottic opening than neutral position or sniffing position during awake Fiberoptic bronchoscope oral intubation, so extension position was recommended as the starting head position for awake Fiberoptic bronchoscope oral intubation.

Trial registration

Clinical Trials.gov. no. NCT02792855. Registered at https://register.clinicaltrials.gov on 23 september 2017.

Deep Learning Based Airway Segmentation Using Key Point Prediction

The purpose of this study was to investigate the accuracy of the airway volume measurement by a Regression Neural Network-based deep-learning model. A set of manually outlined airway data was set to build the algorithm for fully automatic segmentation of a deep learning process. Manual landmarks of the airway were determined by one examiner using a mid-sagittal plane of cone-beam computed tomography (CBCT) images of 315 patients. Clinical dataset-based training with data augmentation was conducted. Based on the annotated landmarks, the airway passage was measured and segmented. The accuracy of our model was confirmed by measuring the following between the examiner and the program: (1) a difference in volume of nasopharynx, oropharynx, and hypopharynx, and (2) the Euclidean distance. For the agreement analysis, 61 samples were extracted and compared. The correlation test showed a range of good to excellent reliability. A difference between volumes were analyzed using regression analysis. The slope of the two measurements was close to 1 and showed a linear regression correlation (r2 = 0.975, slope = 1.02, p < 0.001). These results indicate that fully automatic segmentation of the airway is possible by training via deep learning of artificial intelligence. Additionally, a high correlation between manual data and deep learning data was estimated.

Evaluation of Velopharyngeal Closure Function With 4-Dimensional Computed Tomography and Assessment of Radiation Exposure in Pediatric Patients: A Cross-Sectional Study

OBJECTIVE

Some patients with cleft palate (CP) need secondary surgery to improve functionality. Although 4-dimensional assessment of velopharyngeal closure function (VPF) in patients with CP using computed tomography (CT) has been existed, the knowledge about quantitative evaluation and radiation exposure dose is limited. We performed a qualitative and quantitative assessment of VPF using CT and estimated the exposure doses.

DESIGN

Cross-sectional.

SETTING

Computed tomography images from 5 preoperative patients with submucous CP (SMCP) and 10 postoperative patients with a history of CP (8 boys and 7 girls, aged 4-7 years) were evaluated.

PATIENTS

Five patients had undergone primary surgery for SMCP; 10 received secondary surgery for hypernasality.

MAIN OUTCOME MEASURES

The presence of velopharyngeal insufficiency (VPI), patterns of velopharyngeal closure (VPC), and cross-sectional area (CSA) of VPI was evaluated via CT findings. Organ-absorbed radiation doses were estimated in 5 of 15 patients. The differences between cleft type and VPI, VPC patterns, and CSA of VPI were evaluated.

RESULTS

All patients had VPI. The VPC patterns (SMCP/CP) were evaluated as coronal (1/4), sagittal (0/1), circular (1/2), and circular with Passavant's ridge (2/2); 2 patients (1/1) were unevaluable because of poor VPF. The CSA of VPI was statistically larger in the SMCP group (P = .0027). The organ-absorbed radiation doses were relatively lower than those previously reported.

CONCLUSIONS

Four-dimensional CT can provide the detailed findings of VPF that are not possible with conventional CT, and the exposure dose was considered medically acceptable.

Effects of surgical mandibular advancement on the upper airways of adult class II patients: A systematic review with meta-analysis

AIM

To systematically review the effects of surgical mandibular advancement (SMA) regarding changes of the upper airways in adult patients with skeletal Class II malocclusion.

MATERIALS AND METHODS

Five electronic databases were searched up to April 2020. Human studies focusing on the morphology and dimension of the upper airways after SMA were included. 'Quality assessment for Before-After (Pre-Post) Studies' was used to assess the risk of bias of the individual studies. Standard mean differences (SMD) with 95% confidence intervals (CI) were calculated for random effect model meta-analysis. The certainty of evidence was assessed using the GRADE tool.

RESULTS

Twenty cohort studies of only treated patients without control group were eligible for qualitative synthesis, of which 17 were used for quantitative synthesis. Very low certainty of evidence indicated that SMA resulted in significant increase of the volume and of the smallest cross-sectional area (SMC) of the nasopharynx (volume SMD: 1.43, CI: 0.62, 2.24, P = .001, I²  = 87.8%; SMC SMD: 1.53, CI: 0.59, 2.47, P = .001, I²  = 90.5%) and oropharynx (volume SMD: 1.36, CI: 0.37,2.35, P = .007, I²  = 92.1%; SMC SMD: 1.21, CI: 0.11,2.32, P = .032, I²  = 93.1%). Significant augmentation of the distances between the posterior pharynx wall and the uvala (SMD: 0.73, CI: 0.46,0.98, P < .001, I²  = 72.7%), the posterior border of the tongue (SMD: 0.52, CI: 0.21,0.84, P = .001; I² : 60.5%), the gonion (SMD: 1.24, CI: 0.56,1.91, P < .001; I²  = 88.8%) and the epiglottis (SMD: 0.40, CI: 0.06,0.74, P = .033; I²  = 84.8%) were observed.

CONCLUSIONS

Weak evidence suggests enlargement of the upper airways of adult Class II subjects following SMA, with major increases in the oropharynx.

Evaluation of the pharyngeal recess with cone-beam computed tomography

PURPOSE

To evaluate the radiological anatomy of the pharyngeal recess (PR) by gender and age.

METHODS

Images of patients who underwent cone-beam computed tomography (CBCT) were analyzed retrospectively. A total of 600 PRs (140 male, 160 female) were examined. PR depths, distances between the posterior nasal spine (PNS) and the posterior wall of the pharynx, right and left torus levatorius lengths, and distances between the right and left torus levatorius were measured on the axial plane passing through the PNS-basion point.

RESULTS

PR depths differed significantly between age groups (right p = 0.030, left p = 0.047). The PR depths of individuals under 35 years of age were significantly higher than those of individuals aged 35 and over. Further, the distances between the PNS and the posterior wall of the pharynx differed significantly between age groups and between gender groups. The distances between the PNS and the posterior wall of the pharynx were shorter in patients under 35 years of age (p = 0.000). In terms of gender, these distances were significantly longer in males (p = 0.014). The distances between the right and left torus levatorius were also significantly longer in males (p = 0.029).

CONCLUSION

The PR is the region in which nasopharyngeal carcinoma originates most frequently and is very important for early diagnosis. The present results indicated that this region can be examined with CBCT.

Genioglossus motor unit activity in supine and upright postures in obstructive sleep apnea

This study investigated whether a change in posture affected the activity of the upper-airway dilator muscle genioglossus in participants with and without obstructive sleep apnea (OSA). During wakefulness, a monopolar needle electrode was used to record single motor unit activity in genioglossus in supine and upright positions to alter the gravitational load that causes narrowing of the upper airway. Activity from 472 motor units was recorded during quiet breathing in 17 males, nine of whom had OSA. The mean number of motor units for each participant was 11.8 (SD 3.4) in the upright and 16.0 (SD 4.2) in the supine posture. For respiratory-modulated motor units, there were no significant differences in discharge frequencies between healthy controls and participants with OSA. Within each breath, genioglossus activity increased through the recruitment of phasic motor units and an increase in firing rate, with an overall increase of ~6 Hz (50%) across both postures and participant groups. However, the supine posture did not lead to compensatory increases in the peak discharge frequencies of inspiratory and expiratory motor units, despite the increase in gravitational load on the upper airway. Posture also had no significant effect on the discharge frequency of motor units that showed no respiratory modulation during quiet breathing. We postulate that, in wakefulness, any increase in genioglossus activity to compensate for the gravitational effects on the upper airway is achieved primarily through the recruitment of additional motor units in both healthy controls and participants with OSA.

A New Method for Determining the Level of the Carotid Artery Bifurcation

Exact localization of the bifurcation of the common carotid artery using skin surface landmarks is important for various diagnostic and therapeutic purposes, including emergency cases. Traditional methods have confirmed their accuracy in only a certain percentage of cases and there are inconsistencies among various publications. The cervical computed tomography-angiographic examinations for any diagnostic purpose between June 2017 and December, 2017 in the authors' hospital were examined. Measurements were performed for (MT-CB) and (MT-SE) distances and the results were recorded [MT = The tip of the mastoid process; CB = common carotid artery bifurcation; SE = sternal extremity of the clavicle]. Cervical computed tomography angiography was found in the records of 91 patients in the 6-month period between June 2017 and December 2017. After exclusion criteria were applied, a total of 116 carotid bifurcation levels on the right and left sides were measured in 58 patients. The mean MT-CB distance was 6.29 ± 0.9 cm (range: 2.9-8.4 cm). The mean distance between MT and SE was 15.3 ± 1.7 cm (range: 9.9-19.0 cm). The (MT-CB): (MT-SE) ratios ranged from 29% to 51% with a mean of 41 ± 4.2% (95% CI: 39.88%-42.10%) and a median of 41.1% (P < 0.05) (Kolmogorov-Smirnov test). The distance ratio values did not change significantly according to age and gender (respectively P = 0.341, P = 0.093). These results show that the CB is usually located at two-fifths of the distance from the mastoid tip to the sternal extremity of the clavicle and closer to the mastoid tip.

The effect of altered head and tongue posture on upper airway volume based on a validated upper airway analysis-An MRI pilot study

OBJECTIVE

To determine the influence of altered head or tongue posture on upper airway (UA) volumes using MRI imaging based on a new objective and validated UA evaluation protocol.

SETTING AND SAMPLE POPULATION

One supine CBCT and five sagittal MRI scans were obtained from ten subjects in different head and tongue positions: (a) supine neutral head position (NHP) with the tongue in a natural resting position with the tip of the tongue in contact with the lingual aspect of the lower incisors (TRP); (b) head extension with TRP; (c) head flexion with TRP; (d) NHP with the tip of the tongue in contact with the posterior edge of the hard palate (THP); and (e) NHP with the tip of the tongue in contact with the floor of the mouth in contact with the caruncula sublingualis.

MATERIAL AND METHODS

Based on a validated CBCT UA analysis, the retropalatal, oropharyngeal and the corresponding total volumes were measured from each MRI scan. Wilcoxon signed-rank test was applied to determine the statistically significant difference in mean volume between the baseline head and tongue posture (NHP with TRP) and the other postures.

RESULTS

Five females and five males with a mean age of 46.5 ± 13.7 years volunteered for this pilot study. UA volumes, particularly the oropharyngeal volume, increased significantly with head extension and NHP with THP and decreased significantly with head flexion.

CONCLUSION

Altered head and tongue posture proved to affect UA volumes, thus representing confounding variables during three-dimensional radiographic image acquisition.

Relations between mandible-only advancement surgery, the extent of the posterior airway space, and the position of the hyoid bone in Class II patients: a three-dimensional analysis

The objective of the present study was to evaluate the relation between mandibular advancement, the three-dimensional extent of the posterior airway space (PAS), and the position of the hyoid bone, using cone-beam computed tomography (CT). Twenty-eight Class II patients (21 women (mean (SD) age 29 (9) years) and seven men (mean (SD) age 23 (6) years)), who had had mandibular-only advancement surgery (Obwegeser-Dal Pont) were included in the study. In each case, cone-beam CT scans were taken one week before and six months after operation, and a retrospective analysis made of the alterations of several airway variables (volume, mean cross-sectional area, and diameter) and the three-dimensional extent of mandibular and hyoid movement, by using IPlan® cranial software. A linear regression was also done to correlate mandibular advancement, the movement of the hyoid bone, and airway variables. There were significant postoperative increases in all volumetric PAS variables, and in most diametric and spherical variables (p<0.05). There was also a significant linear relation between forward displacement of the mandible and the movement of the hyoid bone (p<0.05). These results show that mandible-only advancement surgery causes an increase in most dimensions of the PAS. This intervention can be assumed to reduce airway resistance and therefore might be a suitable treatment option for patients with obstructive sleep apnoea syndrome.

Changes in sleep and airway variables in patients with obstructive sleep apnea after mandibular advancement splint treatment

INTRODUCTION

Obstructive sleep apnea (OSA) is an extensive public health problem that imposes considerable morbidity. Mandibular advancement splint (MAS) therapy is a well tolerated treatment, but success rates are difficult to predict. Our objective was to investigate the relationship of oropharyngeal airway dimensions, sleep characteristics, patient biometrics, and treatment response within an OSA patient sample.

METHODS

Records of 33 adults were assessed retrospectively with the use of Dolphin 3D and Image J to measure the airway on pretreatment supine cone-beam computed tomography images and derived lateral cephalograms. The patients used Somnodent (Somnomed; Crows Nest, Australia) MAS appliances, which were titrated over 6-8 weeks. Appliance titration measurements and pre- and posttreatment polysomnograms were assessed. Respiratory disturbance index (RDI), absolute and percentage changes in RDI, non-rapid eye movement (NREM) RDI, rapid eye movement (REM) RDI, supine and nonsupine NREM and REM RDI, and minimal blood-oxygen saturation variables were evaluated. The associations of measurements from 2D and 3D minimal anterior-posterior linear distance and 3D airway variables with MAS treatment response were estimated.

RESULTS AND CONCLUSIONS

Combined effects of baseline total airway volume, body mass index, neck circumference, location of minimal cross sectional area, and OSA severity were associated with treatment response. Patients with higher initial OSA and more superiorly located airway constriction showed enhanced treatment response to MAS therapy. Airway constriction due to maxillofacial disproportions rather than soft tissue obstruction also showed better treatment response. No significant relationships were found in lateral cephalogram measurements.

Comparison of vocal cord view between neutral and sniffing position during orotracheal intubation using fiberoptic bronchoscope: a prospective, randomized cross over study

Background

In intubation using fiberoptic bronchoscope (FOB), partial or complete obstruction of upper airway makes the FOB insertion difficult. Thus, maneuvers to relieve such obstructions are recommended. There have been no studies to determine whether the sniffing or neutral position is superior for this purpose. Therefore, this study was performed to examine the effects of these two positions including vocal cord view.

Methods

Fifty-four patients scheduled to receive general anesthesia by orotracheal intubation were eligible for inclusion in the study with informed consent. After confirmation of proper head positioning depending on the group, the view of the vocal cord was acquired in each position. Images were reviewed using the percentage of glottic opening (POGO) score.

Results

A total of 106 images of vocal cords from 53 patients were obtained. The mean of difference of POGO score was 11.09, higher for the neutral position and standard deviation was 23.73 (p = 0.002). Neutral position increased POGO score in 31 patients and decreased POGO score in 13 patients compare to sniffing position (p = 0.017). There were no significant differences between the two head positions with regard to intubation time or degree of convenience during intubation.

Conclusions

Neutral position improved the view of glottic opening than sniffing position during oral fiberoptic intubation. However, there was no difference in the difficulty of tube insertion between the two positions.

Trial registration

Clinical Trials.gov identifier: NCT02931019, registered on October 12, 2016.

Comparison of Imaging Softwares for Upper Airway Evaluation: Preliminary Study

The interest about upper airway evaluation has increased lately. Therefore, many softwares have been developed aiming to improve and facilitate the analysis of airway volume. The objective of this study was to compare two different softwares packages, Mimics and Dolphin, in their accuracy and precision in upper airway space measurements. Preoperative cone beam computed tomography scans of nine nonsyndromic patients submitted to surgically assisted rapid maxillary expansion were included in this study. The imaging exams were converted to DICOM (digital imaging and communications in medicine) files and imported to the softwares. The mean volume for the Dolphin group (G1) was 10.791 cm ³ (SD = 4.269 cm ³ ) and for the Mimics group (G2) was 10.553 cm ³ (SD = 4.564 cm ³ ). There was no statistically significant difference between the two groups ( p  = 0.105).

Three-dimensional evaluation of the posterior airway space: differences in computed tomography and cone beam computed tomography

OBJECTIVES

Obstructive sleep apnea syndrome (OSAS) becomes increasingly important. For diagnosis and surgery, computed tomography (CT), and cone beam computed tomography (CB-CT) are used equally, although in most of cases, patient positioning differs between supine positioning (CT) and upright seating positioning (CB-CT). We measured volumetric and anatomical changes in the posterior airway space (PAS) between upright and supine positioning in a three-dimensional set up.

MATERIALS AND METHODS

Coherent CT and CB-CT scans of 55 patients were included in the study. Using Brainlab ENT 3.0, image data was superimposed, and three-dimensional models were segmented. PAS height, cross-sectional area, vertical and horizontal position of the mandible and hyoid, and volumetric analyses of the three-dimensional models were measured.

RESULTS

PAS height and cross-sectional area were significantly higher in CB-CT compared to CT scans (p < 0.001). In the vertical dimension, the mandible and hyoid were localized more caudally in CB-CT in contrast to CT scans (p < 0.04; p < 0.001). Three-dimensional evaluation showed a greater volume of the PAS in CB-CT (p < 0.0001). Pearson correlation coefficient showed a correlation between vertical positioning of the mandible and hyoid compared to the positioning of the patient.

CONCLUSIONS

Patient positioning during CT and CB-CT has an effect on the location of anatomical structures like the mandible and hyoid and changes the dimensions and volume of the posterior airway space significantly.

CLINICAL RELEVANCE

The radiological technique used and the positioning of the patient should be taken into account when considering further surgical therapy.

Evaluation of tongue volume and oral cavity capacity using cone-beam computed tomography

The aims of this study were to reveal the usefulness of a newly developed method for measuring tongue volume (TV) and oral cavity capacity (OCC) and to assess the relationship between them. The tongue was coated with a contrast agent, and the TV and OCC were determined using cone-beam computed tomography (CBCT). We enrolled 20 adults who were scheduled to undergo CBCT to evaluate the relationship of the third molar roots to the alveolar nerve before molar extraction. Each participant’s tongue was coated with a contrast agent, and CBCT of the tongue and oral cavity was performed. Using computer software, we evaluated reconstructed 3D images of the TV, oral cavity proper volume (OCPV), and OCC. The mean TV was 47.07 ± 7.08 cm³. The mean OCPV and OCC were 4.40 ± 2.78 cm³ and 51.47 ± 6.46 cm³, respectively. There was a significant correlation between TV and OCC (r = 0.920; p < 0.01) but not between TV and OCPV. The mean TV/OCC ratio was 91 ± 5%. The proposed method produced CBCT images that enabled effective measurement of TV and OCC. This simple method of measuring TV and OCC will be useful in the diagnosis on the tongues with abnormal size.

Sonographic Measurement of the Epiglottis in Normal Chinese Adults

Objectives

(1) To assess the normal range of thickness of the epiglottis by means of ultrasound measurement. (2) To evaluate inter-observer agreement in measuring the thickness of the epiglottis of normal individuals by ultrasound. (3) To assess the association between biological factors and the thickness of the epiglottis.

Methods

Fifty adult volunteers working at a local accident and emergency department were recruited. The thickness of the epiglottis was measured by means of ultrasound examination, which was performed twice by two emergency physicians at different time. The study subjects' age, sex, height and body weight were recorded.

Results

The mean thickness of the epiglottis was 0.236 cm and the standard deviation was 0.020. Male subjects had thicker epiglottis. Interobserver agreement of the two emergency physicians who performed the ultrasound scan was very good. Multiple regression models showed that sex and height were useful predictors of the thickness of the epiglottis.

Conclusions

Bedside ultrasound assessment of the epiglottis is an easy, rapid and reliable method to evaluate its thickness. Further studies are needed to evaluate the thickness of the epiglottis in patients with epiglottitis before it can be put into clinical use.

Effect of Body Position on Pharyngeal Swallowing Pressures Using High-Resolution Manometry

The effect of body position and gravitational pull on the complex pressure-driven process of pharyngeal swallowing remains unknown. Using high-resolution manometry (HRM), this study aims to identify positional adaptations of pharyngeal physiology by evaluating swallowing pressure patterns in a series of inverted body positions. Ten healthy adults each underwent swallowing tasks with pharyngeal HRM at six body positions using an inversion table (0°[upright], 45°, 90°[supine], 110°, 135°, and 180°[fully inverted]). Repeated measures ANOVA was used to assess impact of position on pressure parameters, and pharyngeal-UES pressure gradients translate. Velopharyngeal pressures varied by position (P < 0.001), with significantly higher pressures generated with inversion ≥90°, compared with upright and 45°. Change in position did not significantly affect common mesopharyngeal pressures or swallowing pressure durations. UES valving mechanisms were preserved during inversion, with subtle variations observed in integral pressures (P = 0.011). Pharyngeal-UES pressure gradients changed with position (P < 0.01), increasing with inversion > 90° compared to upright and 45°. Mechanisms of deglutition may differ with position and relative direction of gravity, particularly when at > 45° inclination. Increased palatal pressure is generated in the upside-down position to achieve nasopharyngeal closure and prevent regurgitation. While other classically measured pressures may not consistently differ with positioning, many individuals exhibit adaptations in pressure gradients when inverted, likely due to a combination of changes in pharyngeal driving force and UES opening mechanisms. Identification of these changes, relative to position, further builds on our understanding of the adaptability of the pharyngeal swallowing system.

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.

Effectiveness and Validity of Sonographic Upper Airway Evaluation to Predict Difficult Laryngoscopy

OBJECTIVES

Our objective was to evaluate the effectiveness of 9 airway sonographic parameters imaged from the submandibular view as predictors of difficult laryngoscopy. Additionally, we aimed to evaluate the validity of the models of combined sonographic and clinical tests in predicting difficult laryngoscopy.

METHODS

This study analyzed a sample of 199 patients who were categorized as having easy (grades 1 and 2) or difficult (grades 3 and 4) laryngoscopy during general anesthesia with endotracheal intubation based on the laryngoscopic criteria of Cormack and Lahane (Anaesthesia 1984; 39:1105-1111). Nine sonographic parameters imaged from the submandibular view, including the hyomental distance in neutral and extended positions, hyomental distance ratio, tongue cross-sectional area, tongue width, tongue volume, tongue thickness-to-oral cavity height ratio, and floor of the mouth muscle cross-sectional area and volume, were analyzed. The validity of the models encompassing combined screening tests was assessed.

RESULTS

Twenty-two patients (11.1%) were categorized as having difficult laryngoscopy. Statistically significant differences between patients with difficult and easy laryngoscopy were noted for 5 of 9 parameters. The diagnostic validity profiles showed poor sensitivity (9.1%-42.9%) and positive predictive value (4.5%-66.7%), but good specificity (71.8%-97.7%) and negative predictive value (87.1%-94.5%). The combination of tests improved the diagnostic validity profile (area under the curve, 0.852).

CONCLUSIONS

Sonographic predictors may help identify patients with difficult laryngoscopy. Individual measures have unsatisfactory diagnostic profiles. The models based on combined tests have improved diagnostic value.

Are three-dimensional airway evaluations obtained through computed and cone-beam computed tomography scans predictable from lateral cephalograms? A systematic review of evidence

OBJECTIVE

To systematically review the literature correlating upper airway parameters between lateral cephalograms (LC) and cone-beam computed tomography (CBCT) or computed tomography (CT) scans to determine the utility of using LC to predict three-dimensional airway parameters.

MATERIALS AND METHODS

Both electronic and manual searches of the included studies were performed by two reviewers, and the quality of the studies that met selection criteria were assessed.

RESULTS

A total of 11 studies from the literature met the selection criteria. Assessed outcome variables showed correlation r < .7 between the LC and CT scans. The correlation between the LC and CBCT ranged from weak to strong with -.78 ≤ r and r ≤ .93 reported in the nasopharyngeal segment. In the oropharyngeal segment, a weak to strong correlation was reported with a range of -37 ≤ r and r ≤ .83 between the CBCT and LC. All associations in the hypopharyngeal segment showed a weak correlation. Four of studies were of weak quality, five were of moderate quality, and two were rated to be of strong quality.

CONCLUSION

No strong correlations were reported between the LC and CT scans. However, the LC-derived adenoid-nasopharyngeal ratio and the linear measurement (posterior nasal spine, PNS, to posterior pharyngeal wall) had a strong correlation with upright nasopharyngeal area and volume in the CBCTs. The area measurement in conventional LC can be also used as an initial screening tool to predict the upright three-dimensional oropharyngeal volumetric data. The variability of the hypopharyngeal segment cannot be predicted by LCs. However, more well-designed studies are needed to determine the clinical utility of using LC to predict airway size.

The Recline Exercise: Comparisons with the Head Lift Exercise in Healthy Adults

The aim of this investigation was to examine the comparative effectiveness of the new Recline Exercise (RE) and the traditional Head Lift Exercise (Shaker Exercise) on submental muscle activity, tongue strength, and perceived exertion in 40 healthy young adults (mean age = 24.5 years, SD 2.6 years). Both groups participated in a 6-week exercise regimen. Outcome variables evaluated pre- and post-exercise included: duration and peak amplitude of submental muscle activity during swallowing measured via surface electromyography (sEMG); anterior and posterior isometric lingual pressures measured with the Iowa Oral Performance Instrument; and perceived exertion levels measured with the Borg category-ratio scale of perceived exertion. Results indicated no significant pre-post differences within or between groups in swallow duration and peak amplitude. In addition, the RE group demonstrated significant post-treatment increases in anterior and posterior tongue strength [p = 0.009; p < 0.001]; however, these increases were of small magnitude (d = 0.132; d = 0.319). Both groups showed marked improvements in perceived exertion levels [p < 0.001]. Our findings indicate that healthy young adults who perform the RE or the HLE do not have significant swallow duration or amplitude gains, most likely due to the reduced need for such gains in the healthy head/neck musculature for submaximal tasks. Furthermore, the significant lingual strength gains seen with the RE indicate that additional musculature is being engaged during its completion. These results are encouraging; however, future research in older adults and patients with dysphagia with examination of swallowing biomechanics is needed to determine its full potential as a rehabilitative regimen.

Effect of body position on vocal tract acoustics: Acoustic pharyngometry and vowel formants

The anatomic basis and articulatory features of speech production are often studied with imaging studies that are typically acquired in the supine body position. It is important to determine if changes in body orientation to the gravitational field alter vocal tract dimensions and speech acoustics. The purpose of this study was to assess the effect of body position (upright versus supine) on (1) oral and pharyngeal measurements derived from acoustic pharyngometry and (2) acoustic measurements of fundamental frequency (F0) and the first four formant frequencies (F1-F4) for the quadrilateral point vowels. Data were obtained for 27 male and female participants, aged 17 to 35 yrs. Acoustic pharyngometry showed a statistically significant effect of body position on volumetric measurements, with smaller values in the supine than upright position, but no changes in length measurements. Acoustic analyses of vowels showed significantly larger values in the supine than upright position for the variables of F0, F3, and the Euclidean distance from the centroid to each corner vowel in the F1-F2-F3 space. Changes in body position affected measurements of vocal tract volume but not length. Body position also affected the aforementioned acoustic variables, but the main vowel formants were preserved.

A comparative study of the pharyngeal airway space, measured with cone beam computed tomography, between patients with different craniofacial morphologies

PURPOSE

The present study aims to determine any existing association between airway dimensions, measured with cone beam computed tomography (CBCT), and the different patient craniofacial morphologies.

MATERIAL AND METHODS

Sixty CBCT (Dental Picasso Master 3D) images, from patients treated at the Orthodontics Master at Valencia University were selected. The program InVivoDental 5.1 was used to visualize sections, analyze three-dimensional images, and perform airway measurements in the three planes of the space. Intra- and interobserver error methods were recorded. After that, measurements at three different levels of the airway (upper, medium, lower) were taken, in both the anteroposterior and transversal directions of the airway space. The area (mm(2)) of the airway space at the three levels was also measured.

RESULTS

In the anteroposterior airway measurements, there were differences between the measurements by level. The magnitude of these differences depended on the skeletal pattern of the individual. In the transversal airway measurements and in the area airway measurements, there were no differences according to the skeletal pattern. However, in the transversal direction, measurements in the lower level were significantly higher than in the superior level in all cases. When measuring the area, significantly higher measurements in the upper level were recorded. The homogeneity between medium and lower levels decreased gradually from class I to class III subjects.

CONCLUSIONS

No statistically significant results were observed that related the anteroposterior and vertical skeletal craniofacial morphology with airway dimensions, although some specific associations have been detected for certain airway levels or for pattern combinations.

Proposal of new upper airway margins in children assessed by CBCT

OBJECTIVES

Recently, studies have performed three-dimensional analyses of upper airways in children. However, there was a lack of airway delineation according to anatomical boundaries and/or easily mobile soft-tissue landmarks were used. The aim of the present study was to define new upper airway margins in children on CBCT according to anatomical bony landmarks and to validate the method.

METHODS

25 scans were randomly selected from a larger database containing CBCT scans of children prior to orthodontic treatment (14 girls and 11 boys; mean age, 10.9 ± 2.5 years). Scans were evaluated by two observers. Specific head positioning and virtual orientation protocols were adopted and greyscale thresholding was established for each patient. Volume and minimum cross-sectional area of the oropharynx were calculated. Intra- and interobserver reliability were assessed by reassessment of the CBCTs 2 weeks later.

RESULTS

The new airway margins were defined superiorly by a line passing through the palatal plane (anterior nasal spine to posterior nasal spine) extending to the posterior wall of the pharynx, inferiorly by a line passing from the anterosuperior edge of C4 to menton, anteriorly by a line passing from the soft palate to menton, posteriorly and laterally by the respective pharyngeal walls. Method error for airway volume and minimal cross-sectional area was ≤2.00%, and intra- and interobserver reliability ranged from 0.99 to 1.00.

CONCLUSIONS

The proposed protocol utilizes easily identifiable bony landmarks to delineate the upper airway on cone beam scans of children and was found to be reliable and reproducible.

Ultrasonographic evaluation of geniohyoid muscle and hyoid bone during swallowing in young adults

OBJECTIVES/HYPOTHESIS

The geniohyoid muscle plays an important role in hyoid bone movement. Adequate hyoid bone movement during swallowing is important for effective bolus flow and pharyngeal clearing. The aim of this study was to estimate the relationship between the geniohyoid muscle size and function and hyoid bone movement during swallowing in healthy young adults, as measured via ultrasound, in different body positions.

STUDY DESIGN

Cross-sectional study.

METHODS

Forty young (20-40 years old) adults (20 male and 20 female) participated. The cross-sectional area of the geniohyoid muscle at rest (seated position), the geniohyoid muscle contraction velocity, and the hyoid bone displacement during swallowing 10 mL of mineral water were measured by ultrasound in seated, supine, and right lateral decubitus positions.

RESULTS

The size of the geniohyoid muscle correlated with body height. Males had larger geniohyoid cross-sectional area than females and greater maximal and anterior hyoid displacement during swallowing than females, and maximal and anterior hyoid bone displacement during swallowing correlated with the size of geniohyoid muscle only when the body was in the supine position; these two movements were positively correlated to each other.

CONCLUSIONS

Genders vary in hyoid bone movement during swallowing, and the correlation between geniohyoid muscle size and hyoid bone displacement varies among different body positions during swallowing. This investigation also illuminates the use of ultrasound in providing quantitative measures of geniohyoid muscle and hyoid bone displacement during swallowing.

LEVEL OF EVIDENCE

2c.

Evaluation of pharyngeal airway space changes after bimaxillary orthognathic surgery with a 3-dimensional simulation and modeling program

INTRODUCTION

The aims of this study were to use 3-dimensional simulation and modeling programs to evaluate the effects of bimaxillary orthognathic surgical correction of Class III malocclusions on pharyngeal airway space volume, and to compare them with the changes in obstructive sleep apnea measurements from polysomnography.

METHODS

Twenty-five male patients (mean age, 21.6 years) with mandibular prognathism were treated with bilateral sagittal split osteotomy and LeFort I advancement. Polysomnography and computed tomography were performed before surgery and 1.4 ± 0.2 years after surgery. All computed tomography data were transferred to a computer, and the pharyngeal airway space was segmented using SimPlant OMS (Materialise Medical, Leuven, Belgium) programs. The pretreatment and posttreatment pharyngeal airway space determinants in volumetric, linear distance, and cross-sectional measurements, and polysomnography changes were compared with the paired samples t test. Pearson correlation was used to analyze the association between the computed tomography and polysomnography measurements.

RESULTS

The results indicated that setback procedures produce anteroposterior narrowing of the pharyngeal airway space at the oropharyngeal and hypopharyngeal levels and the middle and inferior pharyngeal volumes (P <0.05). In contrast, advancement of the maxilla causes widening of the airway in the nasopharyngeal and retropalatal dimensions and increases the superior pharyngeal volume (P <0.05). Distinctively, bimaxillary orthognathic surgery induces significant increases in the total airway volume and the transverse dimensions of all airway areas (P <0.05). Significant correlations were found between the measurements on the computed tomography scans and crucial polysomnography parameters.

CONCLUSIONS

Bimaxillary orthognathic surgery for correction of Class III malocclusion caused an increase of the total airway volume and improvement of polysomnography parameters. A proposed treatment plan can be modified according to the risk of potential airway compromise or even to improve it with 3-dimensional imaging techniques and polysomnography.

Effects of Gravity on the Velopharyngeal Structures in Children Using Upright Magnetic Resonance Imaging

Objective

The influence of gravity on the velopharyngeal structures in children is unknown. The purpose of this study is to compare the velopharyngeal mechanism in the upright and supine positions while at rest and during sustained speech production in children between 4 and 8 years old.

Methods

A 0.6 Tesla open-type, multipositional magnetic resonance imaging scanner was used to image subjects in the upright and supine positions. The scanning protocol included a T2 fluid attenuation inversion recovery and an oblique coronal turbo spin echo scan with short scanning durations (7.9 seconds) to enable visualization of the velopharyngeal anatomy during rest and production of sustained /i/ and /s/.

Results

The magnetic resonance imaging protocol used for this study enabled successful visualization of the velopharyngeal anatomy in the sagittal and oblique coronal planes at rest and during sustained phonation of /i/ and /s/. Positional differences demonstrated a small nonsignificant ( P > .05) variation for velar measures (length, thickness, and height), retrovelar space, and levator veli palatini measures (length and angles of origin).

Conclusions

Gravity had a negligible effect on velar length, velar thickness, velar height, retrovelar space, levator muscle length, and levator angles of origin. Supine imaging data can be translated to an upright activity such as speech. This is the first study to provide normative levator muscle lengths for children between 4 and 8 years old. Upright imaging may be a promising tool for difficult-to-test populations.

Airway changes in obstructive sleep apnoea patients associated with a supine versus an upright position examined using cone beam computed tomography

OBJECTIVE

This study aimed to describe total volume and cross-sectional area measurement changes in obstructive sleep apnoea patients associated with a supine versus an upright position.

METHOD

A retrospective chart review of patients who underwent cone beam computed tomography in upright and supine positions was performed, and the images were analysed.

RESULTS

Five obstructive sleep apnoea patients (all male) underwent both upright and supine cone beam computed tomography imaging. Mean age was 35.0 ± 9.3 years, mean body mass index was 28.1 ± 2.7 kg/m2 and mean apnoea-hypopnoea index was 39.3 ± 23.0 per hour. The airway was smaller when patients were in a supine compared with an upright position, as reflected by decreases in the following airway measurements: total volume; posterior nasal spine, uvula tip, retrolingual and tongue base (not significant) cross-sectional areas; and site of the minimum cross-sectional area (of the overall airway). Total airway volume decreased by 32.6 per cent and cross-sectional area measurements decreased between 32.3 and 75.9 per cent when patients were in a supine position.

CONCLUSION

In this case series, the airway of obstructive sleep apnoea patients was significantly smaller when patients were in a supine compared with an upright position.

Videofluoroscopic investigation of body position on articulatory positioning

PURPOSE

To quantitatively examine the effects of body position on the positioning of the epiglottis, tongue, and velum at rest and during speech.

METHOD

Videofluoroscopic data were obtained from 12 healthy adults in the supine and upright positions at rest and during speech while the participants produced 12 VCV sequences. The effects of body position, target sounds, and adjacent sounds on structural positioning and vowel formant structure were investigated.

RESULTS

Velar retropositioning in the supine position was the most consistent pattern observed at rest. During speech, all structures, with varying degrees of adjustment, appeared to work against the gravitational pull, resulting in no significant narrowing in the oro- and nasopharyngeal regions while in the supine position. Minimal differences in the formant data between the body positions were also observed. Overall, structural positioning was significantly dependent on the target and adjacent sounds regardless of body position.

CONCLUSIONS

The present study demonstrated that structural positioning in response to gravity varied across individuals based on the type of activities being performed. With varying degrees of positional adjustment across different structures, fairly consistent articulatory positioning in the anterior-posterior dimension was maintained in different body positions during speech.

Cephalometric and three-dimensional assessment of the posterior airway space and imaging software reliability analysis before and after orthognathic surgery

PURPOSE

This study aimed to compare the reliability of three different imaging software programs for measuring the PAS and concurrently to investigate the morphological changes in oropharyngeal structures in mandibular prognathic patients before and after orthognathic surgery by using 2D and 3D analyzing technique.

MATERIAL AND METHODS

The study consists of 11 randomly chosen patients (8 females and 3 males) who underwent maxillomandibular treatment for correction of Class III anteroposterior mandibular prognathism at the University Hospital in Zurich. A set of standardized LCR and CBCT-scans were obtained from each subject preoperatively (T0), 3 months after surgery (T1) and 3 months to 2 years postoperatively (T2). Morphological changes in the posterior airway space (PAS) were evaluated longitudinally by two different observers with three different imaging software programs (OsiriX(®) 64-bit, Switzerland; Mimics(®), Belgium; BrainLab(®), Germany) and manually by analyzing cephalometric X-rays.

RESULTS

A significant increase in the upper airway dimensions before and after surgery occurred in all measured cases. All other cephalometric distances showed no statistically significant alterations. Measuring the volume of the PAS showed no significant changes in all cases. All three software programs showed similar outputs in both cephalometric analysis and 3D measuring technique.

CONCLUSION

A 3D design of the posterior airway seems to be far more reliable and precise phrasing of a statement of postoperative gradients than conventional radiography and is additionally higher compared to the corresponding manual method. In case of Class III mandibular prognathism treatment with bilateral split osteotomy of the mandible and simultaneous maxillary advancement, the negative effects of PAS volume decrease may be reduced and might prevent a developing OSAS.