Airway Cross-sectional Area Research Articles

0740 Correlation of Pharyngeal Critical Pressure with Upper Airway Anatomy in Obstructive Sleep Apnea: A Systematic Review

Abstract Introduction Obstructive sleep apnea (OSA) is a disease characterized by multiple episodes of upper airway collapse during sleep that causes oxygen desaturation and waking, leading to multiple comorbidities. The gold standard objective measure of upper airway collapsibility is the pharyngeal critical pressure (Pcrit), the nasal pressure at which inspiratory airflow is abolished. The objective of this systematic literature review is to summarize the current understanding of the anatomical factors that determine upper airway collapsibility. Methods A search using the PRISMA methodology was performed on PubMed for English language scientific papers that correlated Pcrit to anatomic measurements (such as airway length, airspace cross-sectional area, airway compliance, lung volumes, BMI, neck circumference, and waist circumference). In addition, papers reporting a correlation between Pcrit and the apnea-hypopnea index (AHI) were reviewed. Results 751 papers were retrieved, and a total of 29 papers that matched eligibility criteria were included in the quantitative synthesis. The literature review confirmed that Pcrit has a significant correlation with the AHI. Pcrit also correlated with multiple anatomic measurements, including airway length, tongue dimensions, lung volume, and measures of obesity including BMI, neck circumference, and waist circumference. Conclusion The pharyngeal critical pressure is a measure of disease severity in OSA, as demonstrated by its correlation with AHI. The primary variables determining Pcrit were found to be airway length and measures of obesity. Surprisingly few studies to date have investigated the correlation between Pcrit and pharyngeal compliance and between Pcrit and airway cross-sectional area. In the future, a better understanding of the biomechanical factors that determine upper airway collapsibility is expected to help identify the optimal intervention of each phenotype of airway collapse for personalized medicine. Support (If Any) Medical College of Wisconsin Department of Otolaryngology

The relationship between mandibular advancement, tongue movement, and treatment outcome in obstructive sleep apnea.

To characterize how mandibular advancement enlarges the upper airway via posterior tongue advancement in people with obstructive sleep apnea (OSA) and whether this is associated with mandibular advancement splint (MAS) treatment outcome. One-hundred and one untreated people with OSA underwent a 3T magnetic resonance (MRI) scan. Dynamic mid-sagittal posterior tongue and mandible movements during passive jaw advancement were measured with tagged MRI. Upper airway cross-sectional areas were measured with the mandible in a neutral position and advanced to 70% of maximum advancement. Treatment outcome was determined after a minimum of 9 weeks of therapy. Seventy-one participants completed the study: 33 were responders (AHI<5 or AHI≤10 events/hr with >50% AHI reduction), 11 were partial responders (>50% AHI reduction but AHI>10 events/hr), and 27 nonresponders (AHI reduction<50% and AHI≥10 events/hr). Responders had the greatest naso- and oropharyngeal tongue anterior movement (0.40 ± 0.08 and 0.47 ± 0.13 mm, respectively) and oropharyngeal cross-sectional area enlargement (6.41 ± 2.12%) per millimeter of mandibular advancement. A multivariate model that included tongue movement and percentage of airway enlargement per millimeter of mandibular advancement along with baseline AHI correctly classified 69.2% (5-fold cross-validated 62.5%, n = 39) of participants in response categories when the jaw was advanced in the range that would usually be regarded as sufficient for clinical efficacy (> 4 mm). In comparison, a model using only baseline AHI correctly classified 50.0% of patients (5-fold cross-validated 52.5%, n = 40). Tongue advancement and upper airway enlargement with mandibular advancement in conjunction with baseline AHI improve treatment response categorization to a satisfactory level (69.2%, 5-fold cross-validated 62.5%).

Efficacy of Han-uvulopalatopharyngoplasty (HUPPP) combined with radiofrequency ablation of tongue base or HUPPP with traction of tongue base on moderate to severe patients with obstructive sleep apnea hypopnea syndrome (OSAHS):a multicenter randomized controlled trial

Objective: To compare the therapeutic efficacy of Han-uvulopalatopharyngoplasty (HUPPP) combined with radiofrequency ablation of tongue base or HUPPP with traction of tongue base on moderate to severe patients with obstructive sleep apnea hypopnea syndrome (OSAHS). Methods: This is a multicenter randomized controlled trial. From March 2017 to July 2019, moderate to severe OSAHS patients from three clinical center in Shanghai who were intolerant to continuous positive airway pressure (CPAP) and with velopharyngeal and glossopharyngeal plane obstruction were enrolled in this study. According to the surgical type, they were 1∶1 randomized to HUPPP plus radiofrequency ablation of tongue base group (Ablation group) or HUPPP plus traction of tongue base group (Traction group). All patients completed over-night standard Polysomnography (PSG), upper-airway assessment (Friedman classification, Müller test, CT and cephalometric examination), preoperative routine examination, Epworth Sleepiness Scale (ESS) and Quebec sleep questionnaire (QSQ). Six to 12 months after operation, all the above-mentioned examinations were repeatedly performed. Changes of aforementioned variables before and after operation were assessed. Results: A total of 43 patients with moderate to severe OSAHS were enrolled in this study. One patient lost to follow-up, the remaining 21 were allocated to Ablation group and 21 were allocated to Traction group. The total therapeutic efficacy of all patients was 69.05% (61.90% in Ablation group and 76.19% in Traction group), but there was no statistical significance between the two groups (P= 0.317). The value of sleep scale score (ESS and QSQ), objective sleep variables (apnea-hypopnea index, oxygen saturation, percentage of time with blood oxygen less than 90% in total sleep time, oxygen desaturation index and micro-arousals) and upper airway cross-sectional area (palatopharyngeal and retrolingual area) of the two groups were improved (P<0.05), but the differences between the two groups were not statistically significant (P>0.05). Conclusion: For moderate to severe OSAHS who had glossopharyngeal plane obstruction, both HUPPP plus radiofrequency ablation of tongue base or HUPPP plus traction of tongue base are effective treatment for OSAHS, and the curative effect is similar. The choice of surgical type could be selected according to patient's or surgical conditions.

Computed Tomography and Cephalometric Evaluation of Obstructive Sleep Apnea Syndrome.

To examine the changes of upper airway cross sectional area in each phase of respiration in different degrees of severity of OSAS with computed tomography and cephalometry to decide on further treatment. A Prospective study was done in the Department of Radiology and Imaging, Kasturba Medical College, Mangalore, spanning over a period from March 2017 to December 2019. 50 patients were included in the study including control group. Patients who had at least 2-3 major symptoms of sleep apnea such as snoring, daytime somnolence, and apnea were included in this study. All patients were examined and then subjected to polysomnography(PSG) and upper airway CT. Patients with apnea-hypopnea index (AHI) of < 5 on Polysomnography were included in the control group and those with AHI of > 5 were categorized in to the study group Cross-sectional area of the airway at the level of the nasopharynx, oropharynx and the hypopharynx were obtained. Standard cephalometric measurements were made on a lateral radiograph of skull/ CT scanogram. Of the 36 patients in the study group, 31 patients were males and 5 were females. In the control group of 12 patients, 8 were males and 4 females. The cross sectional area at the lower border of the nasopharynx which is also the level of the nasopharyngeal sphincter was the most affected level in OSAS (p value of < 0.0001). Mean uvular diameter in the control group was 9.6mm and in the OSAS group it was 11.2mm. The mean length of the soft palate was 36.4mm in the controls, 39.5mm in the mild/moderate OSAS and 41.2mm in the severe OSAS group. Obstructive sleep apnea is a complex disorder characterized by apneic episodes during sleep. In this study the most common site of obstruction is nasopharyngeal sphincter and the oropharynx. Although PSG is the diagnostic test of choice, imaging plays an important role in planning surgical and conventional treatment.

A Cone Beam CT Study of Upper Airway Morphology in Perimenopausal and Postmenopausal Women.

PurposeMenopause is accompanied by a decline in estrogen and progesterone. Several studies have demonstrated that upper airway patency decreases in women after menopause, while morphology changes are still a lack of evidence. This study aimed to explore upper airway morphology changes in perimenopausal and postmenopausal women.MethodsThis retrospective cross-sectional study included 367 consecutive Chinese female patients over 25 years old who had routinely taken large-field cone beam computed tomography in the imaging library of Peking University School and Hospital of Stomatology from October 2016 to September 2020. A total of 283 males were screened as sex controls according to the same age group. Upper airway morphology, hyoid position and facial pattern were measured. The association between perimenopausal and postmenopausal years and upper airway morphology in both sexes was analyzed.ResultsPerimenopausal women (aged 45–54 years) showed a significant decrease in the volume (3172.91mm3, 95% CI = 653.86–5691.96) and minimum cross-sectional area (37.08 mm2, 95% CI = 5.36–68.80), and a significant increase in the length (−1.96mm, 95% CI = −3.62 to −0.29) of upper airway compared to adjacent reproductive years (aged 35–44), while this difference was neither seen in other adjacent two reproductive age groups of females nor in the same age groups of males. In postmenopausal women (55 years and older), hyoid position was significantly lower (−2.74mm, 95% CI = −4.42 to −1.07) than either age group, while no similar changes were seen in men.ConclusionWomen had smaller airway volume, reduced upper airway cross-sectional area and longer airway length in perimenopausal years, and a significantly lower hyoid position in postmenopausal years. These changes may be related to menopause itself and independent of the changes associated with aging.

Pharyngeal enlargement via tongue advancement differs with mandibular advancement therapy response and improves treatment prediction

Abstract Introduction Mandibular advancement splint (MAS) treatment outcome prediction for obstructive sleep apnoea (OSA) is currently unreliable. Lower baseline AHI has been associated with better MAS response but is a poor predictor on its own. Imaging markers may enhance prediction. We investigate how the upper airway enlarges via posterior tongue advancement, using tagged MRI during mandibular advancement, as a potential predictor of MAS treatment response. Methods 101 untreated OSA participants (AHI 10–102 events/hr) underwent an MRI scan wearing a MAS. Mid-sagittal tagged MRI images were collected to quantify tongue movement during passive jaw advancement. Upper airway cross-sectional areas were measured with the mandible in a neutral position and advanced to 70% of the maximum protrusion. Treatment outcome was determined after a minimum of 9 weeks of therapy. Results 71 participants completed the study: 33 were responders (AHI&amp;lt;5 or AHI≤10 events/hr with &amp;gt;50% AHI reduction), 11 were partial responders (&amp;gt;50% AHI reduction but AHI&amp;gt;10 events/hr), and 27 non-responders (AHI reduction&amp;lt;50% and AHI≥10 events/hr). Responders had the greatest naso- and oropharyngeal tongue advancement (0.40±0.08 and 0.47±0.13mm, respectively) and oropharynx enlargement (6.41±2.12%) per millimetre of mandibular advancement. The inclusion of these imaging markers along with baseline AHI in a multivariate model classified more patients in the right MAS response group (69.2%) than a model based only on baseline AHI (50.0%) when the mandible was advanced by at least 4 mm. Conclusions Tongue advancement and upper airway enlargement with mandibular advancement in conjunction with baseline AHI improves MAS treatment response categorisation to a satisfactory level.

QS1: Nasopharyngeal Airway and Subcranial Space Analysis in Pfeiffer Syndrome

Background:Tracheotomy in infancy helps patients with Pfeiffer syndrome survive by preventing respiratory crisis, however, difficulty in decannulation consequently may be a challenge. This study attempts to investigate the regional abnormalities of the nasopharyngeal airway in Pfeiffer syndrome, to provide an anatomic basis for the upper airway surgical treatment and decannulation.Method:Seventy-two preoperative CT scans (Pfeiffer syndrome, n=30; control, n=42) were included in this study. The airway volume, cross-sectional area, and cephalometrics, were measured using Materialise software.Results:Patients with Pfeiffer syndrome developed a 50% (p<0.001) reduction of nasal airway volume, and a 44% (p=0.003) restriction in pharyngeal airway volume. The cross-sectional area of Pfeiffer patients at the choana, was only half that of normals’ (p<0.001). The posterior width of nasal airway in Pfeiffer syndrome was shortened by 13% (p=0.003), and the height was reduced by 21% (p<0.001). The cross-sectional areas at condylion and gonion levels, indicating the caliber of pharyngeal airway at entrance and midsection, were reduced by 67% (p<0.001) and 47% (p<0.001), respectively, when compared with normals.Conclusion:Nasal airway volume in Pfeiffer syndrome is significantly restricted, in length, height and width, along with the choanal stenosis in all cases in this cohort. The reduced anteroposterior length of nasal airway contributes to the shortened maxilla, more than the anteroposterior position. The limited nasal pathway height and width results from the hypoplastic sphenoid. Mediolateral and anteroposterior restricted dimensions are evident across the entire course of pharyngeal airway. Therefore, mediolateral maxillary expansion likely benefits Pfeiffer syndrome patients, in addition to maxillomandibular advancement.

Volumetric magnetic resonance imaging analysis of multilevel upper airway surgery effects on pharyngeal structure.

The Sleep Apnea Multilevel Surgery (SAMS) trial found that modified uvulopalatopharyngoplasty with tonsillectomy (if tonsils present) combined with radiofrequency tongue ablation reduced obstructive sleep apnea (OSA) severity and daytime sleepiness in moderate-severe OSA. This study aimed to investigate mechanisms of effect on apnea-hypopnea index (AHI) reduction by assessing changes in upper airway volumes (airway space, soft palate, tongue, and intra-tongue fat). This is a case series analysis of 43 participants of 51 randomized to the surgical arm of the SAMS trial who underwent repeat magnetic resonance imaging (MRI). Upper airway volume, length, and cross-sectional area, soft palate and tongue volumes, and tongue fat were measured. Relationships between changes in anatomical structures and AHI were assessed. The participant sample was predominantly male (79%); mean ± SD age 42.7 ± 13.3 years, body mass index 30.8 ± 4.1 kg/m2, and AHI 47.0 ± 22.3 events/hour. There were no, or minor, overall volumetric changes in the airway, soft palate, total tongue, or tongue fat volume. Post-surgery there was an increase in the minimum cross-sectional area by 0.1 cm2 (95% confidence interval 0.04-0.2 cm2) in the pharyngeal airway, but not statistically significant on corrected analysis. There was no association between anatomical changes and AHI improvement. This contemporary multilevel upper airway surgery has been shown to be an effective OSA treatment. The current anatomical investigation suggests there are not significant post-operative volumetric changes associated with OSA improvement 6-month post-surgery. This suggests that effect on OSA improvement is achieved without notable deformation of airway volume. Reduced need for neuromuscular compensation during wake following anatomical improvement via surgery could explain the lack of measurable volume change. Further research to understand the mechanisms of action of multilevel surgery is required. This manuscript presents a planned image analysis of participants randomized to the surgical arm or the clinical trial multilevel airway surgery in patients with moderate-severe obstructive sleep apnea (OSA) who have failed medical management to assess change in OSA events and daytime sleepiness. https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=266019&isReview=true%20Australian%20New%20Zealand%20Clinical%20Trials%20Registry%20ACTRN12514000338662, prospectively registered on March 31, 2014.

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

To evaluate the performance of 4-dimensional computed tomography (4D-CT) in assessing upper airway obstruction (UAO) in patients with Robin sequence (RS) and compare the accuracy and reliability of 4D-CT and flexible fiber-optic laryngoscopy (FFL). Prospective survey of retrospective clinical data. Single, tertiary care pediatric hospital. At initial and 30-day time points, a multidisciplinary group of 11 clinicians who treat RS rated UAO severity in 32 sets of 4D-CT visualizations and FFL videos (dynamic modalities) and static CT images. Raters assessed UAO at the velopharynx and oropharynx (1 = none to 5 = complete) and noted confidence levels of each rating. Intraclass correlation and Krippendorff alpha were used to assess intra- and interrater reliability, respectively. Accuracy was assessed by comparing clinician ratings with quantitative percentage constriction (QPC) ratings, calculated based on 4D-CT airway cross-sectional area. Results were compared using Wilcoxon rank-sum and signed-rank tests. There was similar intrarater agreement (moderate to substantial) with 4D-CT and FFL, and both demonstrated fair interrater agreement. Both modalities underestimated UAO severity, although 4D-CT ratings were significantly more accurate, as determined by QPC similarity, than FFL (-1.06 and -1.46 vs QPC ratings, P = .004). Overall confidence levels were similar for 4D-CT and FFL, but other specialists were significantly less confident in FFL ratings than were otolaryngologists (2.25 and 3.92, P < .0001). Although 4D-CT may be more accurate in assessing the degree of UAO in patients with RS, 4D-CT and FFL assessments demonstrate similar reliability. Additionally, 4D-CT may be interpreted with greater confidence by nonotolaryngologists who care for these patients.

Ansa cervicalis stimulation increases pharyngeal patency in patients with obstructive sleep apnea.

Hypoglossal nerve stimulation (HNS) is an alternative treatment option for obstructive sleep apnea (OSA) that reduces pharyngeal collapsibility, but HNS nonresponders often demonstrate continued retropalatal and lateral pharyngeal wall collapse. Recent evidence suggests that caudal pharyngeal traction with sternothyroid muscle contraction via ansa cervicalis stimulation (ACS) can also stabilize the pharynx, but the underlying mechanisms have not been elucidated. Our objective was to evaluate the effect of ACS on pharyngeal patency during expiration when the airway is most hypotonic. Eight participants with OSA underwent sustained ultrasound-guided fine-wire stimulation of the medial branch of the right hypoglossal nerve with and without transient stimulation of the branch of the ansa cervicalis nerve plexus innervating the right sternothyroid muscle during drug-induced sleep endoscopy. Airway cross-sectional area and expiratory airflow (V̇e) were measured from endoscopy video with ImageJ and pneumotachometry, respectively. ACS significantly increased retropalatal cross-sectional area (CSARP) to 211% [159-263] of unstimulated CSARP (P < 0.05). Adding ACS to HNS increased CSARP from baseline by 341% [244-439] (P < 0.05), a 180% [133-227] increase over isolated HNS (P < 0.05). ACS increased V̇e from baseline by 177% [138-217] P < 0.05). Adding ACS to HNS increased V̇e by 254% [207-301], reflecting decreases in pharyngeal collapsibility. Combining ACS with HNS increased retropalatal cross-sectional area and increased expiratory airflow, suggesting decreases in pharyngeal collapsibility. Our findings suggest that ACS exerts caudal traction on the upper airway through sternothyroid muscle contraction and that it may augment HNS efficacy in patients with OSA.NEW & NOTEWORTHY Ansa cervicalis stimulation (ACS) is a recently proposed neurostimulation mechanism for generating caudal pharyngeal traction that may benefit patients with obstructive sleep apnea. Here, we document endoscopic findings with ACS during drug-induced sleep endoscopy and additionally detail the effects of ACS on expiratory airflow, when the pharynx is known to be most hypotonic.

Determining normal values for lower trachea and bronchi size in children by computed tomography (CT).

Normative data for central airway dimensions are a prerequisite to objectively assess large airway pathologies. Studies with computed tomography (CT) measurements of normal trachea and bronchi size in children are scarce. The purpose of this study is to establish normal values of central airway dimensions in children by CT. The study included chest CT studies from children aged 0-18 years. Any condition that predisposed the patient to have an abnormal tracheal or bronchial size was excluded. Airway diameters and cross-sectional area (CSA) were measured using double oblique reconstructions at five levels: proximal trachea, mid-trachea, distal trachea, right main bronchus, and left main bronchus. The inclusion criteria were met by 110 subjects (mean age, 10.8 years; SD, 5.2 years). Various regression models that considered the relationship between patient demographics and anteroposterior (AP) diameter, transverse diameter, and CSA at each of the five levels were assessed. R2 was utilized to select the best model. Multiple formulae (using patient age) were developed to calculate expected normal dimensions for five levels in the central airways on the natural log scale. Finally, z-scores were obtained for central airway dimensions at these five levels. Normative data in pediatric central airways are crucial to identify large airway pathologies. We propose using the formulae devised in our study to calculate the predicted dimensions of central airways and their z-scores in pediatric patients. Normative data from our study will aid in objective quantification of central airways, increase clinician confidence, and provide appropriate patient care.

Three-dimensional changes of oropharyngeal airway after orthodontic extraction treatment in skeletal class Ⅰ adolescents

Objective: To explore the effect of extraction on upper airway in skeletal class Ⅰ adolescents. Methods: According to random number table method, 30 skeletal class Ⅰteenagers who underwent orthodontic straight wire treatment were selected randomly in Department of Orthodontics, School of Stomatology, The Fourth Military Medical University between January 2016 and December 2019. There were 13 males and 17 females, aged (13.7±1.5) years (12.2-15.7 years). In all patients, four first premolars were removed and the upper and lower anterior teeth were retracted under non-maximal anchorage (non-implant anchorage or face bow). The cone-beam CT (CBCT) data before and after orthodontic extraction treatments were studied. The three-dimensional model of the upper airway was reconstructed and segmented, and the relevant indexes of oropharyngeal volume and cross-sectional area were measured. Cephalograms was generated to measure tooth-jaw indexes and hyoid position. The changes of each index before and after orthodontic treatment were compared. The correlation between the changes in the volume or sectional area of the oropharyngeal airway and the changes in the dental and maxillary indexes and the hyoid position was tested. Results: Compared with those before treatment, palatopharyngeal volume, glossopharyngeal volume, oropharyngeal total volume, and minimum transection area increased by 632 (558) mm3, 758 (549) mm3, 1 454 (955) mm3 and 14 (29) mm2 respectively, and statistically significant differences were found (P<0.05). The minimum oropharyngeal area was mostly located in the glossopharynx. The cross-sectional area and the maximum anterior-posterior diameter of uvula tip decreased by (4±10) mm2 and (0.4±0.8) mm respectively, and the difference was statistically significant (P<0.05). There was no significant difference in the maximum lateral diameter before and after treatment (P>0.05). The ratio of the maximum antero-posterior diameter to the maximum lateral diameter at the uvula tip decreased from 0.589 (0.034) before treatment to 0.535 (0.047) after treatment (P<0.05), indicating that its shape tends to be more elliptic after treatment. In addition, the change of cross-sectional area at the apex of uvula was positively correlated with the changes of mandibular central incisor lip inclination and the distances from the upper and lower central incisor points to the Frankfort plane perpendicular to the sella point (UI-FHp and LI-FHp) (P<0.05). Conclusions: The impact of orthodontic extraction treatment on oropharyngeal airway was generally small in skeletal class Ⅰ adolescents. However, it could change the shape of the airway to some extent. The change of airway cross-sectional area at the uvula tip was positively correlated with the retraction of anterior teeth.

Airway Growth in Preoperative Patients with Crouzon Syndrome.

Background: Obstructive sleep apnea is common in patients with Crouzon syndrome, yet it may be caused by multiple factors. This study aims to investigate the natural history of airway development in preoperative Crouzon patients, from infants to adults. Methods: Preoperative computed tomography (CT) scans (Crouzon syndrome, n = 73; control, n = 87) were divided into five age subgroups. CT scans were measured using Materialise software. Results: Before 6 months of age, nasal airway volume in patients with Crouzon syndrome was smaller than normal by 37% (p = 0.002), and the cross-sectional area at the choana reduced by 45% (p < 0.001). The reduction of nasal airway volume and cross-sectional area reached their nadir at 2 years of age, with shortening of 44% and 63% (both p < 0.001), respectively. They gradually caught up to normal dimensions after 6 years of age. Between 2 and 6 years, the pharyngeal airway in patients with Crouzon syndrome reduced 44% (p = 0.011) compared with controls. However, the airway cross-sectional area at condylion and gonion levels was less than normal, before 6 months (35%, p = 0.024) and (44%, p = 0.006) after 2 years of age, respectively. This reduction remains into adulthood. Conclusion: Nasal airway volume is more limited in children with Crouzon syndrome who are younger than 2 years of age. Whereas after 2 years of age, the pharyngeal airway develops significant volume restriction, leading to timing and specific treatment area foci based on the site of temporal maximal constriction.

A comparative analysis of aerodynamic and anatomic characteristics of upper airway before and after mini-implant–assisted rapid maxillary expansion

The objective of this research was to observe changes in aerodynamics and anatomic characteristics of the upper airway after mini-implants assisted rapid maxillary expansion and to evaluate the correlation between the 2 changes of the upper airway in young adults. Thirty consecutive patients (mean age, 23.82±3.90years; median, 24.5years; 9 males, 21 females) were involved. Cone-beam computed tomography was taken before activation and over 3months. Three-dimensional models of the upper airway were reconstructed on the basis of cone-beam computed tomography. The anatomic characteristics of the upper airway, including volume, area, transverse, and sagittal diameter, were measured. The aerodynamic characteristics of the upper airway were calculated on the basis of 3-dimensional models using computational fluid dynamics. The correlation between the changes in aerodynamics and anatomic characteristics of the upper airway was explored. The enlargements of the volume of the total pharynx, nasopharynx, and oropharynx were found (9.99%, 20.7%, and 8.84%, respectively). The minimum cross-sectional area increased significantly (13.6%). The airway resistance (R) and maximum velocity (Vmax) decreased significantly in both the inspiration and expiration phase (inspiration: R, -26.8%, Vmax, -15.7%; expiration: R, -24.7%, Vmax, -16.5%). The minimum wall shear stress reduced significantly only in the inspiration phase (-26.3%). The correlations between decreased R and increased volume and minimum cross-sectional area were observed. Mini-implants assisted rapid maxillary expansion is an effective device for improving anatomic characteristics represented by the total volume of the upper airway and minimum cross-sectional area, which contributed to the respiratory function depending on the favorable changes of aerodynamic characteristics including resistance, velocity, and minimum wall shear stress.

Changes in Airway Dimensions Following Non-extraction Clear Aligner Therapy in Adult Patients with Mild-to-moderate Crowding

This retrospective study aimed to assess changes in airway dimensions with non-extraction clear-aligner-therapy (NE-CAT) in adult patients with mild-to-moderate crowding. Cone-beam computed tomographic images were evaluated for 24 adults (16 females and 8 males) with mild-to-moderate crowding, and Class I or mild skeletal Class II malocclusion before and after NE-CAT. Cross-sectional and volumetric airway measurements were performed at the level of the nasal cavity, upper pharyngeal airway space (UAS), and lower pharyngeal airway space (LAS). The Frankfort-mandibular plane angle (FMA), point A-nasion-point B (ANB) angle, and intermolar width were measured. A paired t-test was used to assess changes in airway measurements. Linear regression analyses were performed to identify predictors of the pharyngeal airway volume change at the levels of the UAS and LAS. There was a significant decrease (p = 0.004) in UAS mean volume (486.63± 752.73 mm3), LAS mean volume (p = 0.006), and cross-sectional airway area (p = 0.022) (1536.92± 2512.02 mm3 and 34.66± 69.35 mm2, respectively) with NE-CAT. The mean airway volume of the nasal cavity, mean cross-sectional airway areas of the nasal cavity and UAS, and mean minimum cross-sectional pharyngeal airway area did not change significantly with NE-CAT. Changes in pharyngeal airway volume were not significantly associated with patients' age, gender, treatment duration, pretreatment ANB angle, and changes in FMA and maxillary first intermolar width with NE-CAT. Significant changes in the pharyngeal airway dimensions of the UAS and LAS with NE-CAT in adult patients with mild-to-moderate crowding were identified. The results of the present study show that NE-CAT is not associated with an improvement in airway dimensions in adults with mild to moderate crowding.

Nasopharyngeal airway and subcranial space analysis in Pfeiffer syndrome

Tracheotomy in infancy helps patients with Pfeiffer syndrome to survive by preventing respiratory crisis, but difficulty in decannulation may consequently be a challenge. This study has investigated the regional abnormalities of the nasopharyngeal airway in children with Pfeiffer syndrome to provide an anatomical basis for the surgical treatment and decannulation of the upper airway. Seventy-two preoperative computed tomograms (CT) (Pfeiffer syndrome n=30; control n=42) were included. The airway volume, cross-sectional area, and cephalometrics were measured using Materialise software. Patients with Pfeiffer syndrome developed a 50% (p<0.001) reduction of nasal airway volume, and a 44% (p=0.003) restriction in pharyngeal airway volume. In patients with Pfeiffer syndrome the cross-sectional area at the choana was only half that of the controls (p<0.001). The posterior width of the nasal airway in patients with Pfeiffer syndrome was shortened by 13% (p=0.003), and the height reduced by 21% (p<0.001). The cross-sectional areas at the condylion and gonion levels, which indicate the calibre of the pharyngeal airway at the entrance and midsection, were reduced by 67% (p<0.001) and 47% (p<0.001), respectively, when compared with the controls. The volume of the nasal airway in patients with Pfeiffer syndrome was significantly restricted in length, height, and width, and by choanal stenosis in all cases in this cohort. The reduced anteroposterior length of the nasal airway contributed to the shortened maxilla more than the anteroposterior position. The limited height and width of the nasal pathway was the result of a hypoplastic sphenoid. Restricted mediolateral and anteroposterior dimensions were evident across the entire course of the pharyngeal airway. Mediolateral maxillary expansion in addition to maxillomandibular advancement is therefore likely to benefit these patients.

Tetraplegic obstructive sleep apnoea patients dilate the airway similarly to able-bodied obstructive sleep apnoea patients

Context/objective: Obstructive sleep apnoea (OSA) develops soon after cervical spinal cord injury (SCI) at rates higher than the general population, but the mechanisms are not understood. This study aimed to determine whether OSA in SCI is associated with altered pharyngeal muscle dilatory mechanics during quiet breathing, as has been observed in the non-SCI injured with obstructive sleep apnoea. Design: Cross sectional imaging study. Setting: Medical research institute. Participants: Eight cervical SCI patients with OSA were recruited and compared to 13 able-bodied OSA patients and 12 able-bodied healthy controls of similar age and BMI. Interventions and outcome measures: 3T MRI scans of upper airway anatomy and tagged-MRI to characterize airway muscle motion during quiet breathing were collected for analysis. Results: Considerable variation in the patterns of inspiratory airway muscle motion was observed in the SCI group, with some participants exhibiting large inspiratory airway dilatory motions, and others exhibiting counterproductive narrowing during inspiration. These patterns were not dissimilar to those observed in the able-bodied OSA participants. The increase in airway cross-sectional area of able-bodied control participants was proportional to increase in BMI, and a similar, but not significant, relationship was present in all groups. Conclusion: Despite the limited sample size, these data suggest that SCI OSA patients have heterogeneous pharyngeal dilator muscle responses to the negative pressures occurring during inspiration but, as a group, appear to be more similar to able-bodied OSA patients than healthy controls of similar age and BMI. This may reflect altered pharyngeal pressure reflex responses in at least some people with SCI.

Ultrasonographic Measurement of Pharyngeal-Airway Dimension and Its Relationship with Obesity and Sleep-Disordered Breathing

Previous studies based on magnetic resonance imaging (MRI) or computed tomography (CT) have shown that pharyngeal airway diameter during wakefulness is different between healthy controls and patients with a high risk of sleep-disordered breathing (SDB). However, MRI and CT are expensive and not easily accessible. Conversely, ultrasonography is more accessible and is getting more attention as a point-of-care technology to assess physiologic systems, such as the pharynx. Thus, we aimed to evaluate the feasibility of ultrasonography in estimating the pharyngeal airway dimension. To evaluate the pharyngeal airway with ultrasonography, we measured the parasagittal anterior–posterior (PAP) diameter and transverse diameter. For PAP diameter measurements, the transducer probe was placed in a submandibular lateral oblique position, with its superior margin abutting the angle of the left mandible. For the transverse measurement, the ultrasound probe was positioned in a submandibular location, in a near-coronal plane, just above the hyoid bone so that the tongue could be seen in cross-section. The diameter measurements were performed manually by two technicians. The reliability of these measurements was assessed by the intra-class correlation coefficient (ICC). To validate our measurements, we compared the measured PAP diameter with the average pharyngeal airway cross-sectional area from vellum to glottis measured by acoustic pharyngometry. Furthermore, we compared the influence of obesity and SDB in the measured pharyngeal diameters. Eighteen controls and 13 individuals with a high risk of SDB participated in this study. Reliability analysis of the PAP measurements yielded an ICC of 0.97 (95% confidence interval: 0.94–0.98). Furthermore, measured PAP diameters were significantly correlated with the pharyngeal airway cross-sectional area (r = 0.76, p < 0.01). Moreover, obesity and SDB were associated with decreases in PAP diameter. Our study shows that ultrasonography measurement of the PAP diameter may provide a quantitative assessment of the pharyngeal airway and may be useful for screening of SDB.

Relationship between Vowel Sound Features and Pharyngeal Airway Cross-Sectional Area during Normal Breathing.

Assessment of the pharyngeal airway is becoming important for delivering personalized treatment and better management of sleep apnea. However, evaluation of the pharyngeal airway area is difficult in the current state of the art. It is essential to use simple and accessible technology to measure the pharyngeal airway area. As vowel sounds are generated by vocal cords vibration and characterized by the pharyngeal airway, vowel sounds have the potential to evaluate the pharyngeal airway area. The objective of this study was to investigate the relationship between acoustic features of vowel sounds and the pharyngeal airway cross-sectional area (PAXSA) between soft palate and glottis. Twenty subjects were included in this study whose PAXSA was measured by acoustic pharyngometry. Vowel sounds were recorded with a microphone while lying supine. Vowel sound average power was calculated in different frequency ranges of 100-3000 Hz, 100-500 Hz, 500-1000 Hz, 1000-1500 Hz, 1500-2000 Hz, 2000-2500 Hz and 2500-3000 Hz. Statistical analysis showed that the decreases in the PAXSA were strongly correlated with the higher average power of vowel sounds in all frequency ranges. These results showed that individuals with low PAXSA might articulate the vowel in higher intensity. Clinical Relevance - This study demonstrates that the pharyngeal airway cross-sectional area during normal breathing has a significant effect on vowel articulation. Thus, vowel sound features can be used to estimate the resting pharyngeal airway cross-sectional area.

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

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. 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). 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). 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.