Velopharyngeal Volume Research Articles

Three-dimensional analysis of pharyngeal airway volume in Class I, II, and III malocclusion

Aim: This study aimed to evaluate pharyngeal airway dimensions using cone-beam computed tomography (CBCT) in patients with Class I, II, and III malocclusions and normal growth patterns. Methods: All CBCT images were categorized into three groups: Class I (0° < ANB < 4°, −1 mm < Wits < 0 mm), Class II (ANB > 4°, Wits > 0 mm), and Class III (ANB < 0°, Wits < −1 mm). CBCT images were obtained from individuals with normal growth patterns (32 ± 5° = GN/GO – SN), where GN represents gonion, GN is gnathion, and SN equates to the sella-nasion distance. Measurements were taken for total pharyngeal volume, velopharyngeal volume, glossopharyngeal volume, and oropharyngeal volume, and the narrowest area of the airway was measured. ANOVA and Tukey’s post hoc test were used to compare the airway dimensions among skeletal classes I, II, and III. Results: The CBCT images were captured from 90 patients (45 males and 45 females) aged 17 to 39. The mean volume of the total pharyngeal airway, velopharyngeal, glossopharyngeal, and oropharyngeal and the most constricted area were significantly greater in patients with skeletal Class III malocclusion compared to patients with skeletal Class II malocclusion showing normal growth pattern. Total pharyngeal airway, velopharyngeal, and oropharyngeal volumes were lower in Class II patients compared to Class I and III patients with normal growth patterns. There was a significant difference in the pharyngeal space between males and females with Class II malocclusion. Pharyngeal space in female Class II malocclusion was higher than that in males. There was no difference regarding airway space between female and male patients with Class 1 malocclusion. Pharyngeal space between females and males with Class III malocclusion showed no difference. Conclusion: Class III pharyngeal volumes were generally larger in Class I and II malocclusions. Sex differences in the volumes of various pharyngeal spaces were only present in the case of Class II malocclusions. Relevance for Patients: Class II pharyngeal volumes were generally smaller in Class I and III malocclusions.

Quantification of pharyngeal airway space changes after two-jaw orthognathic surgery in skeletal class III patients

BackgroundSkeletal class III malocclusion is a common dentofacial deformity. Orthognathic treatment changes the position of the jaws and affects the shape of the upper airway to some extent. The aim of this study was to use multislice spiral computer tomography data and orthognathic knowledge to quantify the relationship between the amount of surgical movement of the maxilla or mandible in all three spatial planes and the changes in airway volume that occurred.MethodsA retrospective study of 50 patients was conducted. Preoperative and postoperative linear changes related to skeletal movements of the maxilla and mandible were measured and compared to changes in the most constricted axial level (MCA) and its anteroposterior (MCA-AP) and transverse diameters (MCA-TV). Correlation tests and linear regression analysis were performed.ResultsSignificant interactions were observed between the anterior vertical movement of the maxilla and the MCA-AP. The anteroposterior movement distance of the mandible was significantly correlated with changes in the oropharyngeal, velopharyngeal, total airway volume, MCA, MCA-AP, and MCA-TV. The change in the mandibular plane angle was significantly correlated with the change in velopharyngeal volume, total airway volume (nasopharynx, oropharynx, velopharynx), and MCA.The linear regression model showed that oropharyngeal volume decreased by 350.04 mm3, velopharyngeal volume decreased by 311.50 mm3, total airway volume decreased by 790.46 mm3, MCA decreased by 10.96 mm2 and MCA-AP decreased by 0.73 mm2 when point B was setback by 1 mm.ConclusionsAnteroposterior mandibular control is the key to successful airway management in all patients. This study provides estimates of volume change per millimeter of setback to guide surgeons in treatment planning.

Three-Dimensional Comparative Changes in the Pharyngeal Airway of Patients with Cleft after Two-Jaw Orthognathic Surgery.

The present study evaluated the three-dimensional changes of the pharyngeal airway after orthognathic surgery (OGS) in patients with unilateral and bilateral clefts, and in unilateral cleft patients with and without pharyngeal flap (PF). Forty-five patients with unilateral or bilateral clefts undergoing OGS were enrolled. Cone-beam computed tomographic images were obtained before and after OGS. We measured the pharyngeal airway volumes, minimal cross-sectional area, and the horizontal displacement of facial landmarks. The patients with bilateral cleft exhibited smaller initial velopharyngeal volume (unilateral, 8623 mm 3 ; bilateral, 7781 mm 3 ; P = 0.211), whereas the velopharyngeal volume increased significantly with a median of 744 mm 3 after OGS ( P = 0.031). The median horizontal displacement of A point was 2.9 and 2.6 mm among the patients with unilateral and bilateral clefts, respectively ( P = 0.276), and the median horizontal displacement of B point was -2.9 and -3.3 mm among patients with unilateral and bilateral clefts, respectively ( P = 0.618). The unilateral cleft patients with PF exhibited lower initial velopharyngeal volume (patients with a history of PF surgery, 7582 mm 3 ; patients without a history of PF surgery, 8756 mm 3 ; P = 0.129) and a lower increase in velopharyngeal volume (patients with a history of PF surgery, 437 mm 3 ; patients without a history of PF surgery, 627 mm 3 ; P = 0.739) after OGS. Midface hypoplasia and the decrease in the velopharyngeal volume were more prominent among the bilateral cleft patients and the unilateral cleft patients with PF. After OGS, the velopharyngeal volume increased considerably among the bilateral cleft patients, but no considerable differences were noted among the unilateral cleft patients with PF. Risk, II.

The effect of surgical weight loss on upper airway fat in obstructive sleep apnoea.

Obesity is a reversible risk factor for obstructive sleep apnoea (OSA). Weight loss can potentially improve OSA by reducing fat around and within tissues surrounding the upper airway, but imaging studies are limited. Our aim was to study the effects of large amounts of weight loss on the upper airway and volume and fat content of multiple surrounding soft tissues. Participants undergoing bariatric surgery were recruited. Magnetic resonance imaging (MRI) was performed at baseline and six-months after surgery. Volumetric analysis of the airway space, tongue, pharyngeal lateral walls, and soft palate were performed as well as calculation of intra-tissue fat content from Dixon imaging sequences. Among 18participants(89% women), the group experienced 27.4 ± 4.7% reduction in body weight. Velopharyngeal airway volume increased (large effect; Cohen's d [95% CI], 0.8 [0.1, 1.4]) and tongue (large effect; Cohen's d [95% CI], - 1.4 [- 2.1, - 0.7]) and pharyngeal lateral wall (Cohen's d [95% CI], - 0.7 [- 1.2, - 0.1]) volumes decreased. Intra-tissue fat decreased following weight loss in the tongue, tongue base, lateral walls, and soft palate. There was a greater effect of weight loss on intra-tissue fat than parapharyngeal fat pad volume (medium effect; Cohen's d [95% CI], - 0.5 [- 1.2, 0.1], p = 0.083). The study showed an increase in velopharyngeal volume, reduction in tongue volume, and reduced intra-tissue fat in multiple upper airway soft tissues following weight loss in OSA. Further studies are needed to assess the effect of these anatomical changes on upper airway function and its relationship to OSA improvement.

Restricted upper airway dimensions in patients with dentofacial deformity from juvenile idiopathic arthritis

BackgroundThis retrospective, cross-sectional study aimed to assess the pharyngeal airway dimensions of patients with juvenile idiopathic arthritis (JIA) and moderate/severe JIA-related dentofacial deformity (mandibular retrognathia/micrognathia), and compare the results with JIA patients with a normal mandibular appearance and a group of non-JIA patients.MethodsSeventy-eight patients were retrospectively included in a 1:1:1 manner as specified below. All patients had previously been treated at the Section of Orthodontics, Aarhus University, Denmark. All had a pretreatment cone beam computed tomography (CBCT). Group 1 (JIA+); 26 JIA patients with severe arthritis-related dentofacial deformity and mandibular retrognathia/micrognathia. Group 2 (JIA-); 26 JIA patients with normal mandibular morphology/position. Group 3 (Controls); 26 non-JIA subjects. Dentofacial morphology and upper airway dimensions, excluding the nasal cavity, were assessed in a validated three-dimensional (3D) fashion. Assessment of dentofacial deformity comprised six morphometric measures. Assessment of airway dimensions comprised nine measures.ResultsFive morphometric measures of dentofacial deformity were significantly deviating in the JIA+ group compared with the JIA- and control groups: Posterior mandibular height, anterior facial height, mandibular inclination, mandibular occlusal inclination, and mandibular sagittal position. Five of the airway measurements showed significant inter-group differences: JIA+ had a significantly smaller nasopharyngeal airway dimension (ad2-PNS), a smaller velopharyngeal volume, a smaller minimal cross-sectional area and a smaller minimal hydraulic diameter than JIA- and controls. No significant differences in upper airway dimensions were seen between JIA- and controls.ConclusionJIA patients with severe arthritis-related dentofacial deformity and mandibular micrognathia had significantly restricted upper airway dimensions compared with JIA patients without dentofacial deformity and controls. The restrictions of upper airway dimension seen in the JIA+ group herein were previously associated with sleep-disordered breathing in the non-JIA background population. Further studies are needed to elucidate the role of dentofacial deformity and restricted airways in the development of sleep-disordered breathing in JIA.

Three-dimensional changes in the upper airway and craniomaxillofacial morphology of patients with Angle Class III malocclusion treated with a Frankel III appliance

BackgroundAngle Class III malocclusion, characterized by a concave profile, can cause serious harm to children’s physical and mental health. The Frankel III appliance is an effective treatment for Angle Class III malocclusion in mixed denition. We explored three-dimensional changes in the upper airway and craniomaxillofacial morphology, after one year of Frankel III appliance treatment, in children with Angle Class III malocclusion.MethodsWe included 20 children (9 males), aged 8–10 years, with Angle Class III malocclusion from the Orthodontics Department of our hospital. Each child was treated with a Frankel III appliance for one year. Cone beam computed tomography was performed before and after treatment to evaluate three-dimensional changes in the upper airway and craniomaxillofacial morphology.ResultsAfter one year of treatment, in the upper airway, we observed significant increases in the nasopharynx volume and height (P < 0.05); the velopharyngeal volume, height, and average cross-sectional area (P < 0.05); the glossopharynx volume and minimum cross-sectional area (P < 0.05); and the laryngopharynx height (P < 0.05). Accordingly, the total upper airway volume, height, and average cross sectional area increased significantly (P < 0.05). An examination of craniomaxillofacial morphology showed significant increases in some bone tissues (P < 0.05) and dental measurements, and a significant reduction in the inclination of the mandibular central incisor (P < 0.05).ConclusionChildren with Angle class III malocclusion treated with a Frankel III appliance showed no upper airway narrowing, even after repositioning the mandible posteriorly. Moreover, treatment promoted forward maxilla development and increased its width, in both the dental arch and alveolar bone, which provided a more harmonious craniofacial morphology.

Tongue Function: An Underrecognized Component in the Treatment of Obstructive Sleep Apnea with Mandibular Repositioning Appliance

Obstructive sleep apnea (OSA) is a common but still underrecognized disorder. A mandibular repositioning appliance (MRA) is used to treat OSA by advancing the mandible and thereby reducing the collapsibility of the upper airway. It has been found that an MRA increases the volume of the upper airway, especially the velopharyngeal area, in OSA patients. We hypothesize that this increase in the velopharyngeal volume is associated with an anterior displacement of the tongue, but likely not with a stretching of the soft tissue connecting the soft palate, lateral pharynx, palatopharyngeal arch, and mandible. Since the function and structure of the genioglossus and hypoglossal nerve are always abnormal in patients with OSA, the tongue does not always move simultaneously with the mandible when an MRA is being used. Oropharyngeal exercises, especially tongue exercises, can improve the quality of life of OSA patients, including reduction of daytime sleepiness and snoring, better quality of sleep, and partial decrease in the AHI. Further, in animal models, tongue exercise is also found to be effective in tongue function recovery and in the remodeling of the hypoglossal nucleus. We suggest that a combination of tongue exercises along with MRA is a promising approach for patients who do not respond to an MRA alone.

Evaluation of Three-Dimensional Changes in Pharyngeal Airway Following Isolated Lefort One Osteotomy for the Correction of Vertical Maxillary Excess: A Prospective Study.

Orthognathic surgery involves movement of jaws in all three planes, and this being a part of airway complex, displacement of jaws can influence the dimension of airway at all levels. Lefort one osteotomy surgery with superior repositioning is a common procedure done for patients with vertical maxillary excess. The purpose of this study was to evaluate the three-dimensional volumetric changes in airway after lefort one impaction surgery using three-dimensional cone beam computed tomography (3D-CBCT) in patients with vertical maxillary excess (VME). A prospective analysis of 15 patients who underwent isolated lefort one impaction surgery was done with pre-operative (T0) and 3-months (T1) post-operative 3D-CBCT scans. Airway was divided into three segments, nasopharyngeal, velopharyngeal and oropharyngeal. Volumetric analysis of all these segments was done before and after surgery. Paired 't test' was used to assess the mean difference in airway volume and area between T0 and T1. One-way ANOVA was used to check the mean percentage difference in airway volume and area among the three segments. The mean percentage of nasopharyngeal volume difference was - 0.6299 ± 0.9146%, velopharyngeal volume difference was - 0.5205 ± 1.107%, oropharyngeal volume difference was - 1.492 ± 2.745%. Though volume and area of pharyngeal airway were decreased after maxillary impaction surgery in all three segments of airway studied, they were not statistically significant. Among the three segments of airway studied, oropharyngeal airway volume has shown the highest post-surgical reduction though statistically insignificant. ESS scores were within normal limits. Hence, we are of the opinion that there is lack of evidence to conclude that the patients undergoing lefort one superior repositioning for the treatment of VME might develop significant narrowing of PAS that may predispose the patient to breathing disorders.

Magnetic resonance imaging of the upper airway in patients with quadriplegia and obstructive sleep apnea.

The aim of this study was to investigate upper airway anatomy in quadriplegics with obstructive sleep apnea. Fifty subjects were recruited from three hospitals in Australia: people with quadriplegia due to spinal cord injury and obstructive sleep apnea (n=11), able-bodied people with obstructive sleep apnea (n=18), and healthy, able-bodied controls (n=19). All underwent 3-Tesla magnetic resonance imaging of their upper airway. A subgroup (n=34) received a topical vasoconstrictor, phenylephrine and post-phenylephrine magnetic resonance imaging. Mixed-model analysis indicated no significant differences in total airway lumen volume between the three groups (P=0.086). Spinal cord injury-obstructive sleep apnea subjects had a significantly larger volume of soft palate (P=0.020) and retroglossal lateral pharyngeal walls (P=0.043) than able-bodied controls. Able-bodied-obstructive sleep apnea subjects had a smaller mandible volume than spinal cord injury-obstructive sleep apnea subjects and able-bodied control subjects (P=0.036). No differences were seen in airway length between groups when controlling for height (P=0.055). There was a marginal increase in velopharyngeal volume across groups post-phenylephrine (P=0.050), and post hoc testing indicated the difference was confined to the able-bodied-obstructive sleep apnea group (P<0.001). No other upper airway structures showed significant changes with phenylephrine administration. In conclusion, people with obstructive sleep apnea and quadriplegia do not have a structurally smaller airway than able-bodied subjects. They did, however, have greater volumes of soft palate and lateral pharyngeal walls, possibly due to greater neck fat deposition. The acute response to upper airway topical vasoconstriction was not enhanced in those with obstructive sleep apnea and quadriplegia. Changes in upper airway anatomy likely contribute to the high incidence in obstructive sleep apnea in quadriplegic subjects.

Airway Changes after Cleft Orthognathic Surgery Evaluated by Three-Dimensional Computed Tomography and Overnight Polysomnographic Study

Cleft lip and palate is the most common congenital craniofacial anomaly. Up to 60% of these patients will benefit from cleft orthognathic surgery, which consists primarily of maxillary advancement and mandibular setback to address midface retrusion and relative mandibular protrusion, respectively. It is believed that maxillary advancement can enlarge the airway whilst mandibular setback can reduce the airway, but this has not previously been quantified for cleft patients undergoing orthognathic surgery. This unique longitudinal prospective study of 18 patients was conducted between April 2013 and July 2016. No significant changes occurred by six months postoperatively in body mass index, apnoea-hypopnoea index or lowest oxygen saturation (LSAT). There was a mean increase of 0.73 cm3 in velopharyngeal volume, a mean decrease of 0.79 cm3 in oropharyngeal volume, an improvement in snoring index, and no statistically significant change in hypopharyngeal volume. In conclusion, cleft orthognathic surgery that produced anterior advancement of the maxilla, setback of the mandible and clockwise rotation of the maxillo-mandibular complex resulted in increased velopharyngeal, decreased oropharyngeal and unchanged hypopharyngeal airways, and improved snoring, but did not significantly alter objective sleep-related breathing function.

Changes in Upper Airway Volume in Edentulous Obstructive Sleep Apnea Patients Treated with Modified Mandibular Advancement Device.

This study was an attempt to verify the utility of complete dentures modified as a mandibular advancement device (MAD) in effecting expansion in pharyngeal volume to treat obstructive sleep apnea (OSA) in edentulous patients. The sample consisted of 17 patients (12 male, 5 female, average age 61 ± 4 years; BMI, 22 ± 5; apnea hypopnea index [AHI] 15 to 30). All patients had worn complete dentures for at least 1 year; all patients had the dentures modified to a MAD. Five variables were assessed preoperatively and 6 months after wearing the modified MADs. These variables were: sleep efficiency, AHI, oxygen desaturation events/hr., mean oxygen saturation, snoring index, and airway volume. This assessment was done by subjecting the patients to all-night polysomnography. Without any prosthesis or device in the edentulous patients, the mean velopharyngeal volume was 8.05 ± 0.58 cm(3) , oropharyngeal volume was 2.14 ± 0.38 cm(3) , and hypopharyngeal volume was 3.26 ± 0.78 cm(3) . With complete dentures (unaltered) in the edentulous patients, the mean velopharyngeal, oropharyngeal, and hypopharyngeal volumes were 10.73 ± 0.98 cm(3) , 2.60 ± 0.48 cm(3) , and 4.31 ± 0.89 cm(3) , respectively. There was a statistically significant change in the airway volume following insertion of the complete dentures modified as MADs with velopharyngeal, oropharyngeal, and hypopharyngeal volume recorded as 11.76 ± 1.07 cm(3) , 3.33 ± 0.51 cm(3) , and 4.94 ± 0.83 cm(3) , respectively. From the results obtained in this limited small sample study, it was inferred that the pharyngeal expansion induced by complete dentures modified as MADs effectively reduced symptoms of OSA. Increased volume was most pronounced in the velopharynx region followed by hypopharynx and oropharynx.

Comparative Effects of Two Oral Appliances on Upper Airway Structure in Obstructive Sleep Apnea

Oral appliances are increasingly being used for treatment of obstructive sleep apnea (OSA). Mandibular advancement splint (MAS) mechanically protrudes the mandible, while the tongue stabilizing device (TSD) protrudes and holds the tongue using suction. Although both appliances can significantly improve or ameliorate OSA, their comparative effects on upper airway structure have not been investigated. Cohort study. Sleep Investigation Unit. 39 patients undergoing oral appliance treatment for OSA. OSA patients underwent magnetic resonance imaging (MRI) of the upper airway during wakefulness at baseline and with MAS and TSD in randomized order. Treatment efficacy was determined by polysomnography in a subset of 18 patients. Upper airway lumen and surrounding soft tissue structures were segmented using image analysis software. Upper airway dimensions and soft tissue centroid movements were determined. Both appliances altered upper airway geometry, associated with movement of the parapharyngeal fat pads away from the airway. TSD increased velopharyngeal lateral diameter to a greater extent (+0.35 ± 0.07 vs. +0.18 ± 0.05 cm; P<0.001) and also increased antero-posterior diameter with anterior displacement of the tongue (0.68 ± 0.04 cm; P<0.001) and soft palate (0.12 ± 0.03 cm; P<0.001). MAS resulted in significant anterior displacement of the tongue base muscles (0.35 ± 0.04 cm). TSD responders (AHI reduction ≥50%) increased velopharyngeal volume more than non-responders (+2.65 ± 0.9 vs. -0.44 ± 0.8 cm(3); P < 0.05). Airway structures did not differ between MAS responders and non-responders. These results indicate that the patterns and magnitude of changes in upper airway structure differ between appliances. Further studies are warranted to evaluate the clinical relevance of these changes, and whether they can be used to predict treatment outcome.

Influence of tongue muscle contraction and dynamic airway pressure on velopharyngeal volume in the rat

The mammalian pharynx is a collapsible tube that narrows during inspiration as transmural pressure becomes negative. The velopharynx (VP), which lies posterior to the soft palate, is considered to be one of the most collapsible pharyngeal regions. I tested the hypothesis that negative transmural pressure would narrow the VP, and that electrical stimulation of extrinsic tongue muscles would reverse this effect. Pressure (-6, -3, 3, and 6 cmH2O) was applied to the isolated pharyngeal airway of anesthetized rats that were positioned in a 4.7-T MRI scanner. The volume of eight axial slices encompassing the length of the VP was computed at each level of pressure, with and without bilateral hypoglossal nerve stimulation (0.1-ms pulse, one-third maximum force, 80 Hz). Negative pressure narrowed the VP, and either whole hypoglossal nerve stimulation (coactivation of protrudor and retractor muscles) or medial nerve branch stimulation (independent activation of tongue protrudor muscles) reversed this effect, with the greatest impact in the caudal one-third of the VP. The dilating effects of medial branch stimulation were slightly larger than whole nerve stimulation. Positive pressure dilated the VP, but tongue muscle contraction did not cause further dilation under these conditions. I conclude that the narrowest and most collapsible segment of the rat pharynx is in the caudal VP, posterior to the tip of the soft palate. Either coactivation of protrudor and retractor muscles or independent contraction of protrudor muscles caused dilation of this region, but the latter was slightly more effective.